AN ABSTRTOT CF THE THESIS OF RAYMOND GENE CAVOLA for the degree of MASTER in MECHANICAL ENGINEERING Title: presented on OF SCIENCE APRIL 27, 1982 AN EXPERIMENTAL/ANALYTICAL INVESTIGATION OF NEGATIVELY BUOYANT JETS DISCHARGED VERTICALLY UPWARD INTO A CROSSFLOW CURRENT Abstract approved: Redacted for Privacy Dr. Lorin R. Davis An experimental and analytical study of negatively buoyant jets discharged vertically upward into a crcssf low current was conducted to obtain information on the fate of oil well produced water. This information could be used to validate and calibrate the short and intermediate term portions of a computer model used to predict the disposal. The experirriental results include the dilution arid plume width, measured at selected incremental distances downstream ci the discharge. Independent parameters varied in this investigation were the discharge deosimetric Froude Number, and the ambient to discharge velocity ratio. Results indicate that the Frcucae NurrLber has the greatest effect on dilution; decreasing the Froude Number increases both dilution and plume width. Altering the velocity ratio has little effect on dilution, but does affect plume width. The analytical portion of this study includes a brief presenta-tion of the background of olume modeling, the mathematical develop- ment of the produced water comouter model, and an outline of the pro- cedure for tuning the coefficteucs within the model uslag the experi- mental results of this investigation. It is expected that the results presented here are sufficient for validating and calibrating the initial phases of the computer model. Upon calibration and validation, the model can be used as a predictive tool for determining the fate of negatively buoyant jets. AN EXPERIMENTAL/ANALYTICAL INVESTIGATION OF NEGATIVELY BUOYANT JETS DISCHARGED VERTICALLY UPWARD INTO A CROSSFLOW CURRENT by Raymond Gene Cavola A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Comnieted April 27, 1982 Coraip.encement June 1982 APPROVED: Redacted for Privacy Professor of Mechanical Engineering in charge of major Redacted for Privacy Head o/iePartment of Mechanica/Engineering Redacted for Privacy Dean of Graduate/Sichool Date thesis is presented: APRIL 27, 1982 Typed by Sandy Orr for RAYMOND GENE CAVOLA Ac:oowLEDGEMENTs The successful completion of this project would not have been possible without the assistance of several people. I owe many thanks to: Dr. Lorin Davis, my major professor, who unselfishly provided guidance, encouragement, and timely comments and criticisms throughout the course of this work; Hassan Bahrami, who provided assistance in conducting the experiments; Jack Kellogg, for his help with the shop and tools while I was constructing the apparatus; A special note of thanks to my lovely wife, Nina, for her encouragement, and many sacrifices, made so that this thesis and degree could be completed; Sandy Orr, for typing this document; and finally to Exxon Production Research Company and the Offshore Operators Committee, whose financial assistance made this study possible. TABLE OF CONTENTS PAGE INTRODUCTION 1 ANALYTICAL MODELING 3 Introduction 3 Model Development 6 Tuning the Mode1 25 EXPERIMENTAL MODELING 27 Modeling Parameters 27 Apparatus and Data Acquisition 30 Data Treatment 39 Uncertainty Analysis 46 Results 48 CONCLUSIONS 68 REFERENCES 69 APPENDICES Appendix A - Graphs 70 Appendix B - Experimental Data 36 LIST OF FIGURES FIGURE 1 2 PAGE Idealized jet discharge described by mathematical model. Cross sections are shown at three stages of plume development 5 Coordinate system and definition sketch for a round jet 7 3 Geometry of the collapsing jet plume 14 4 Plane of traverse of the probe 29 5 Schematic of the experimental apparatus and electronic instrumentation 21 6 Schematic of the constant reservoir head salt water 33 7 Enlarged view of conductivity probe 34 8 Typical calibration curve for the conductivity probe. 37 9 Section view showing lifter plate used for measuring conductivity on the false bottom 10 Typical Visicorder print of conductivity and position signals 41 11 Flowchart showing data treatment process 12 Example of typical excess salinity ratio data, as a function of X/D, and its' representative curve. . 44 Example of typical excess salinity ratio data, as a function of Y/D, and its' representative curve. . 45 13 14 A repeat of Figure 12 with 90% confidence interval included to indicate the quality of the experimental data i17 Excess salinity ratio as a function of velocity ratio 49 16 Excess salinity ratio as a function of Froude Number 51 17 Plume half-width as a function of X/D and R for 15 18 FR05 52 Plume half-width as a function of X/D and R for FR1O 53 LIST CF FIGURES (continued) FIGURE 19 PAGE Plume half-width as a function of X/D and R for FR15 54 20 Comparison of regression model with data averages curve for the conditions: FR = 0.5, R = 0 5 21 Comparison of regression model with data averages curve for the conditions: FR = 0.5, F = 0.99 . 57 Comparison of regression model with data averages curve for the conditions: FR = 0.5, R = 1.47 . 58 Comparison of regression model with data averages curve for the conditions: FR = 1.01, F = 0.48. . 59 Comparison of regression model with data averages curve for the conditions: FR = 1.01, F = 1.01. - 60 Comparison of regre.sion model with data averages curve for the conditions: FR = 1.01, F = 1.48. . . . 22 . . 23 . 24 . 25 . . 61 26 Comparison of regression model with data averages curve for the conditions: FR = 1.44, F = 0.52.....62 27 Comparison of regression model with data averages curve for the conditions: FR = 1.44, R = 1.02, . . Comparison of regression model with data averages curve for the conditions: FR = 1.44, R = 1.49. . 28 . 29 30 31 63 * 64 Velocity distribution in the boundary layer above the false bottom for R = 0 5 65 Velocity distribution in the boundary layer above the false bottom for F = 1 0 S6 Velocity distribution in the boundary layer above the false bottom for R = 1.5 .........67 A-i A- 2 A- 3 Plume centerline excess salinity ratio versus X/D, for FR = 0.50, P. = 0.50, and Y/D 0 1 71 Plume centerline excess salinity rario versus X/D, for FR = 0.S0, F = 0.99, and. Y/D 0 1 72 Plume centerline excess salinity ratio versus X/D, for FR = 0,50, P. = 1.47, and Y/D 0 1 73 LIST OF FIGURES (continued) PAGE FIGURE A-4 Plume centerline excess salinity ratio versus X/D, 0.1 for FR = 1.01, R = 0.48, Y/D = 0, and Y/D . Plume centerline excess salinity ratio versus Y/D, for FR = 1.01, R = 0.48, and X/D = 2.5, 5 and 10. . . A-5 A-6 Plume centerline excess salinity ratio versus X/D, 0.1 for FR = 1.01, R = 1.01, Y/D = 0, and Y/D A-8 . . Plume centerline excess salinity ratio versus X/D, 0.1 for FR = 1.01, R = 1.48, Y/D = 0, and Y/D . 78 . 80 . 81 . 82 Plume centerline excess salinity ratio versus Y/D, for FR = 1.01, R = 1.48, and X/D = 2.5 and 5 A-la Plume centerline excess salinity ratio versus X/D, 0.1 0, and Y/D for FR = 1.44, R = 0.52, Y/D . Plume centerline excess salinity ratio versus Y/D, for FR = 1.44, R = 0.52, and X/D = 2.5, 5 and 10. Plume centerline excess salinity ratio versus X/D, 0.1 0, and Y/D for FR = 1.44, R = 1.02, Y/D . A-l3 A-l4 Plume centerline excess salinity ratio versus Y/D, for FR = 1.44, R = 1.02, and X/D = 2.5, 5 and 10. Plume centerline excess salinity ratio versus X/D, 0.1 for FR = 1.44, R = 1.49, Y/D = 0, and Y/D . A-15 76 Plume centerline excess salinity ratio versus Y/D, for FR = 1.01, R = 1.01, and X/D = 2.5, 5 and 10. A-9 A-12 75 . . A-ll 74 . . A-7 . Plume centerline excess salinity ratio versus Y/D, 1.44, P. = 1.49, and x/D = 2.5, 5 and 10. for FR . . 77 83 . 84 . 85 NOMENCLATURE a a 0 semi-minor axis of collapsing element radius of element at end of convective descent semi-major axis of collapsing element; also plume radius in convective descent phase B relative buoyancy C plume salt concentration ambient salt concentration C Carag CD drag coefficient for a.n elliptical cylinder edge drag coefficient for a two-dimensional cylinder drag coefficient for a two-dimensional wedge CD 3 drag coefficient for a two-dimensional plate normal 4 C fric D toflow skin friction coefficient drag force; also discharge port diameter form drag on collapsing element E E in entrainment function momentum jet entrainment entrainment by a two-dimensional thermal ET F Fbf F , 1 F total entrainment buoyancy force bed friction force FD driving force of collapse; also drag force Ff skin friction drag of collapsing element rictn bottom friction coefficients 1/2 FR Froude Number = U / 0 0 g D) 0 2 FRL local Froude Number = U ,/[ g acceleration of gravity I inertial force j unit vector in vertical direction L length of jet-plume element P pressure R velocity ratio = U/U S salinity g b] centerline salinity S discharge salinity S ambient salinity c LS 0 s s C 0 -s -s S distance along jet axis T plume temperature ambient temperature U t time U jet velocity vector a ambient velocity vector discharge velocity towing or current velocity U jet velocity in x-direction ambient velocity in x-direction v plume element velocity in vertical direction tip velocity due to collapse tip velocity due to entrainment V contribution to tip velocity due to entrainment 3 plume half-width plume element velocity in z-direction w a ambient velocity in z-direction horizontal downstream distance from discharge port vertical distance from discharge port x, y, z x_, y, z rectangular coordinates fixed on discharge port rectangular coordinates fixed on plume element Greek Symbols a a1 a2 a3, a4 entrainment coefficient entrainment coefficients for convective descent entrainment coefficients for collapsing plume coefficient of thermal expansion angles ambient current at s makes with x and z axes, respectively density gradient coefficient for density gradient difference inside and outside of collapsina element; also angle in a vertical plane between s and the resultant ambient current coefficient of salt concentration expansion density reference density ambient density discharge density p 0 53 2' p 0 Co direction angles of the jet trajectory angle between the surface projection of the collapsing element centerline and the x-axis AN EXPERINENTAL/ANALYTICAL INVESTIGATION OF NEGATIVELY BUOYANT JETS DISCHARGED VERTICALLY UPWARD INTO A CROSSFLOW CURRENT I. INTRODUCTION With the growing environmental awareness, industry practices are coming under close scrutiny to ensure that industrial processes and operations are conducted so as to minimize their impact on the surOffshore oil operations are a case in point. rounding environment. In the process of extracting oil from beneath the ocean floor, brine mixes with the oil. Serving no useful purpose, the brine is separated from the oil and discharged into the ocean. Since the salinity of the brine is typically 2-5 times that of sea water, the potential for environmental disruption is significant. In the interest of obtaining more information on the disposal of produced water, the Offshore Operators Committee and Exxon Production Research Company have developed a computer model to simulate and predict the fate of produced water when discharged into offshore receiving water. The model has the capability to predict the behavior of produced water discharged into a variety of ambient conditions. This model will aid in the evaluation of the environmental impacts of of f- shore oil operations and will help establish the relative merits of alternative site selection. A critical phase in mathematical modeling is the model validation and calibration phase. In this phase the model is checked for valid- ity and calibrated to ensure that the model agrees with actual field conditions. The development of such computer models involves the use 2 of many assumptions and empirical coefficients. As a result, the assumptions must be checked and verified, and the empirical coeff i- cients within the model must be adjusted (or "tuned") before the model can be used as a predictive tool. The purpose of this investigation was to conduct laboratory simulations of negatively buoyant jets discharged vertically upward into a crossflow current to obtain information useful in the calibration and validation of the model. Specifically, this study included devel- oping the experimental model for laboratory simulation; conducting measurements to obtain data for the computer model validation and calibration; and reviewing and briefly describing the analytical basis of the produced water computer model. The investigation was directed mainly towards the jet and collapse phases of the plume, which included the interaction of the plume with the ocean bottom. The results of this investigation are presented in two parts. The first describes the analytical basis of the computer model and a procedure for tuning the coefficients within the model. part, concerned with The second he experimental modeling involved in the labor- atory simulation, outlines the experimental procedure and presents the results to be used in the calibration and validation of the computer model. 3 II. ANALYTICAL MODELING This chapter is devoted to the description of the mathematical/ computer model for predicting the fate of produced water disposal. First, a brief background is given of pertinent plume models, followed by a description of the basic aspects of the produced water computer model. Then the development of the mathematical model is presented, including a discussion of the solution procedure used in the model. Lastly, the method of tuning the model using the experimental results of this investigation is outlined. INTRODUCTION A number of models for predicting the fate of marine discharges have been developed over the past several years. Early efforts were directed towards the development of stand alone models for passive diffusion of pollutants in the deep ocean, and for the behavior of buoyant plumes from thermal discharges (see Davis and Shirazi1). Koh and Chang2 assembled some of these models and added a treatment for particulate solids contained in the discharge. The resulting model assumed the ambient fluid to have a steady current uniform in the horizontal but varying in direction and speed with depth, and to be density stratified with an arbitrary gradient uniform in the horizontal. Brandsma and Divoky3 built upon the Koh-Chang model and incorporated a passive diffusion model by Fischer to develop a gener- alized model for ambient current variations in three dimensions and in time, variable water depths, and up to 12 different solids. A 1. paper by Brandsma, et. al.5 describes a new model, developed from the Brandsma and Divoky model and tempered by field measurements made at drilling sites in the Gulfs of Mexico and Alaska, and on the eastern The produced water model is this new coast of the United States. model with the solids handling feature removed. In the produced water model, the discharge of produced water into the ocean is taken to originate as a jet from a submerged pipe at an arbitrary orientation. The ocean is assumed to be stratified with an arbitrary velocity distribution. The behavior of the material after release is divided into three distinct phases: 1) convective descent, during which the material tends to behave as a plume under the influence of gravity; 2) dynamic collapse, occuring when the descending plume either impacts the bottom or arrives at the level of neutral buoyancy, at which time the descent is retarded and horizontal spreading dominates; and 3) passive diffusion, beginning when the transport and spreading of the plume is determined more by ambient currents and turbulence than by any dynamic character of its own. This behavior is illustrated in Figure 1. The simplified conceptualization just presented is modeled mathematically. The development of the model is presented below. This investigation deals exclusively with the short and intermediate term regions of the discharge. Consequently, the model development con- centrates on the two dynamic phases of plume behavior. The develop- ment for the long-term passive diffusion will not be presented here. Most of the material presented is taken from References 3 and 5. PLUME IMPACTS BOTTOM CONVECTIVE DIFFUSIVE SPREADING GREATER THAN DYNAMIC SPREADING DYNAMIC COLLAPSE P H AS E PASS I V E DIFFUSION / - Figure 1. Idealized jet discharge described by mathematical model. Cross sections are shown at three stages of plume development. Ui 6 MODEL DEVELOPMENT n this section the mathematical formulation of the produced water model is presented. The flow phenomena of the discharge to be modeled are described as follows: the flow near the discharge port is that of a rising (or sinking) jet in a crosscurrent. The jet entrains ambient fluid and momentum, and experiences a drag force from the ambient fluid due to pressure differences between the upstream and downstream faces of the jet. As a result, the jet grows in size, bends in the direction of the ambient current, and is diluted due to the entrainment of ambient fluid. As the jet extends further downstream, its centerline velocity approaches that of the ambient fluid, the influence of the ambient density gradient becomes dominant, and the jet begins to behave more like a plume (convective descent phase). Upon reaching a point of neutral buoyancy or the ocean bottom, the plume will spread out horizontally and collapse vertically (dynamic collapse phase). After spreading out into a relatively thin layer, further transport and spreading are determined by ambient currents and turbulence (passive diffusion). The model describing all but the passive diffusion portion of this sequence of events is developed below. Convective Descent The equations describing a jet in a stratified ambient with an arbitrary velocity distribution are those for conservation of mass, momentum, energy, and salt. Figure 2 shows a round jet discharging with a flow rate, Q, into a crosscurrent. It is assumed that the 7 (a) Jet coafiguration I (b) Arnbien density profile Figure 2. (c) Ambient velocity and drag furcea Coordinate system and definition sketch for a round jet. 8 jet cross section remains circular and that velocity and density distributions may be approximated by "top hat" profiles. The jet properties are then described by its radius, b, velocity, U, and density, p. The ambient density and current are designated by (y,t) and U (x,y,z,t). As shown in Figure 2, the coordinate axes are fixed on the discharge port, with s the direction of the jet trajectory; @, O, and 63 are its direction angles; and 2 are the directions the resul- tant ambient current at position s makes with respect to the x and z axes, respectively; and y is the angle in a vertical plane between s and the resultant ambient current. Near the discharge port, the flow is very similar to that in a momentum jet. In momentum jet theory, variation in the above quan- tities occur only with distance along the jet axis, s, so rates of change of the conserved quantities are written as derivatives with respect to s. The rate of change of mass flux along the jet axis equals the rate of ambient fluid mass entrainment per unit jet length, so the conservation of mass equation is d 2 (rb pu) = EPa (1) where E is the entrainment rate. The rate of change of momentum flux along the jet axis is equal to the buoyancy force per unit length plus the rate of ambient fluid momentum entrainment per unit length minus the drag force. servation of momentum equation is expressed as The con- 9 - ds (rrb2pLi) = Fj + E aa - D (2) where j is the vertical unit vector. The drag term in the momentum equation accounts for the action of the ambient current in bending the jet. The drag force, accounting for the action of the unbalanced pressure field around the jet caused by the ambient current seen by the jet, is proportional to the square of the velocity component of the oncoming ambient fluid normal to the jet axis. Referring to Figure 2c, the magnitude of the drag force is FD CDPa b(iUaI Sin y) (3) where CD is the drag coefficient. The rate of change of energy flux along the jet axis equals the energy entrained from the ambient fluid, ds [irb2 tJ(T - T )} = Tb dT (4) The rate of change of salt flux along the jet axis is equal to the amount of salt entrained from the ambient fluid, dC ds = irn (5) The rate of change of relative buoyancy flux along the jet axis is equal to the rate of ambient fluid relative buoyancy entrainment, d -ds[rrb 2 U(pa (0) - pH = E(p (o) - p a a (6) 10 An equation of state is required to calculate the local density. p(T, C, F) in a Taylor series about a reference density, Expanding p p, and neglecting higher order terms, yields p=p[l-(T-T)-A(C-c)] 0 0 (7) where p0 T T,P and = 0 (incompressible fluid). T,C Equation (7) can be rewritten as p - p - (T - T) + X(c - C) (8) Solving (4) and (5) provides the information required in (8) to calculate the local density. Following Abraham6, the entrainment function is assumed to de- pend upon the local mean flow andis the sum of contributions due to momentum jet entrainment and a two-dimensional thermal type of entrainxnent. Momentum jet entrainment is proportional to the perimeter of the jet and the velocity difference between the jet and the velocity component of the ambient fluid in the direction of jet travel, = 2Trb ci.1(UI - UI cos y) (9) Entrainment from a two-dimensional thermal is proportional to the perimeter and velocity of the thermal. Visualizing the thermal 11 plume moving horizontally with the ambient fluid but with a vertical velocity U sin y, the resulting equation is E = 2Trb c where ITJ 2a and 2 sin y (10) are entrainment coefficients. The total entrainment is then + Et sin 02 ET = E where sin 82 is arbitrarily introduced as a convenient way to turn on the thermal type of entrainment as the jet bends over to the horizontal. The momentum entrainment depends upon the local Froude Number, 2 FR L where p p-p = U /{ g b] is the ambient density, p is the plume density, b is the plume radius, g is the acceleration of gravity, and p is a reference density, in this case the ambient density at the water surface. expression for l An as a function of the local Froude Number is given by Wu and Koh8: = 0.0806 for FRL 19.1 (12a) = 0.1160 for FRL < 19.1 (12b) Several additional equations are needed to complete the modeling of the convective descent phase. Momentum flux M = These are: 7rb2 pU (13) Buoyancy force per unit length: F = Trb g(p - p Buoyancy flux B = U(P(0) - 2 : irb2 a The locus of the jet centerline is found by integrating the directional cosine differential equations: dx ds - = cos e ds = cos 0 2 dz - = cos 8 ds 3 (l6c) The trigonometric relation, cos 2 0 + cos 2 0 ± cos 2 (17) 03 = 1 is also required. Given a set of initial conditions: 02(0)1 and 03(0)1 Equations (1) - U(o), b(o), p(o), e.,(o), (17) can be integrated using a numerical integration scheme, resulting in the description of the jet behavior in the convective descent phase. When the jet encounters the sea bottom or a depth where the jet density equals the ambient density, the calculation is switched to the dynamic collapse phase. Dynamic Col1ase in the Water Column If the jet encounters a level of neutral buoyancy, its momentum will tend to make it overshoot beyond the neutral point causing a buoyant force to push it back to the neutral position. The combined 13 action of these forces will cause the plume to undergo a decaying vertical oscillation. As the vertical motion of the plume is being suppressed, the plume tends to collapse vertically and spread out horizontally, seeking hydrostatic equilibrium within the stratified ambient fluid. The jet plume here is expected to behave more like a two-dimensional thermal than a momentum jet. The cross section of the two-dimensional thermal is assumed to b elliptical, as shown in Figure 3a. If coordinate axes originate from the centroid of the thermal, the cross sectional outline of the thermal is described by x y a 2 b (18) 2 where a and b, the semi-minor and semi-major axes, respectively, vary with time. The conservation equations for the dynamic collapse in the water column are formulated considering a portion of the thermal of length L. For this case, the conservation equations, written per unit length L, are: Mass: ds Salt: Buoyancy: (19) a Fi-D+Eo a Momentum: Energy: (pabTrU) = Ep d ds (20) a dT [rabU(T - TCo H = rabU d --- ['rrabtj(C - C as dt U = E(p a (o) ds (21) dC H = TrabUds - - p a (22) (23) 14 (a) Figure 3. (b) Geometry of the collapsing'jet plume. 15 ifl these equations, Momentum of the element: - M piTabU Buoyancy force: F lTabg(p Buoyancy: B = irab(p (24) a (25) - (o) - p) (26) Drag force: x-direction: D x = 2 C D3 2a sin()p a lu-ua I (u-u a (27) 2 y-direction: D y c p frica /(a2+b a cos 0 =-C 2bp a lu-u a lv 2 D4 (28) -C - 2 z-direction: D fric p a /(a2+b2)2 IUUaJ cos 07 COS ()p = 2 CD34a IUUI (W_Wa) (29) - c 2 p r / 2 2 frica v(a+b ) Lu-u a cos 0 is the is the drag coefficient for a spheroid wedge, CD where CD 3 4 3 drag coefficient for a circular plate, C. is a skin friction coefficient, is the angle between the surface projection of the element centerline and the x-axis, and 01 and 03 are the angles between the element centerline and the x, y, and z axes, respectively. The auxiliary equations needed are those for entrainment of ambient fluid and for the collapse of the plume. Entrainment is assumed to be the sum of contributions due to convection of the element through the ambient fluid and to the collapse of the element. 16 Each type occurs over the surface area of the element. The total entrainment is given by 3a' + a4 ET = 2r(22) where and (30) a4 are the entrainment coefficients for convection and collapse, respectively, and is the tip velocity of the collapsing plume. The mechanism that drives the plume collapse is the density difference between the inside and outside of the plume. It is assumed that because of turbulent mixing the density gradient inside the plume is less than that outside. This difference is assumed to be ya constant at , where 'y is a coefficient, and a is the radius of a 0 the plume at the end of convective descent. If it is assumed that the plume is resting at the level of neutral buoyancy, that the am- bient density at this level is p, and is the normalized ambient density gradient, 1 p (31) y then the ambient density seen from the plume centroid is = p(1 - cy') (32) and the density inside the plume is ' a p = p0(l - cy') (33) Brandsma and Divoky3 evaluate the force driving the collapse of the plume as 17 'a gL(l -) aa 1 3 a 3 The forces resisting the collapse are form drag, 4 Cg = a Lav2v2 and skin friction Lv frica 2 These forces all act at the centroid of the quadrant of the element, and their resultant equals the inertia of the quadrant, I=FD -F f -D D The horizontal inertia of the quadrant is the time rate of change of the product of its mass and the horizontal velocity of its centroid I = d ab (-i---- L p v1) (3'3) The tip velocity of the quadrant is db = V1 + V3 In these equations, v1 is the quadrant tip velocity due to collapse, and is the combination of the tip velocity due to collapse and due to stretching of the element (obtained by assuming that the minor axis a is kept constant and that no entrainment occurs at that moment), expressed as V2 = V1 - b dL : 18 As the buoyant element velocity approaches the ambient velocity, it will either increase or decrease due to the entrainment of ambient momentum and the drag forces applied to the element. material is supplied continuously Since the from the jet, the element should be capable of stretching or squeezing so that the trajectory of one element can represent the steady picture of a continuous plume. The stretching or squeezing of the element is assumed to be represented by L /22 = constant (41) (u +w V In Equation (39), v3 is the contribution to tip velocity due to entrainment. Its magnitude is obtained by solving for v3 = in Equation (19) while instantaneously holding p and a constant, which yields E V (42) 3 rap The trajectory of the two-dimensional buoyant element is determined from: dx dt U V dz = w at Equations (18) through (43) can be integrated using a numerical integration scheme, using the jet characteristics at the end of the convective descent phase as initial conditions. The development of 19 the plume collapse is computed until spreading of the plume due to collapse is less than that due to diffusion. to handle passive diffusion is used. At this point a routine If the collapsing plume en- counters the bottom, calculation is switched to a different set of equations designed to handle collapse on the bottom. Dynamic Collapse on the Bottom If the plume does not encounter a level of neutral buoyancy it will eventually hit the bottom. This section presents a variation of the model for collapse in the water column to apply to a plume collapsing on the bottom. It is assumed that the shape of the plume cross section is changed to, and maintained as, a half-ellipsoid, as shown in the upper half of Figure 3a. Equation (18) describing the cross section still applies. Velocity differences between the plume element, the bottom, and the anthient fluid are allowed. The bottom is assumed horizontal in the region of plume collapse. Except for minor modifications due to different geometry and to account for the reaction and friction forces on the bottom, the conservation equations are very similar to that for collapse in the water column: Mass: Momentum: Energy: Salt: (- p'rrabu) --- (- pTrab[J) d = (44) a = Fj - D ± 1 - [- rabU(T - T)J = d ds 1 - [- iabU(C - C )] = - 1 2 Ecu - Ff dT rrabu a- (45) (46) dC TrabUds - (47) 20 d Buoyancy: 1 [ rab(o (o) - E(p(o) - (48) The dynamic collapse of a quadrant of the semi-elliptical element is expressed as I = F (49) - Ff - Fbf - where the inertial force is aD I= L p v1) (50) Two forces drive the collapse of the plume on the bottom: the force as developed for collapse in the water column, and the force due to the difference in mean density between the plume and ambient fluid. The combined collapse driving force is given by: ia 3 gL(l - F'D = _a) 2 Bp + - (p - the form drag is = 2 C drag p LaIv v a 2 2 the skin friction is F f C Lv frica 2 the friction force on the bottom is F bf =Fb F rictn F 1 As with the collapse in the water column, db = vi + V3 g L 21 b dL V2V1---- L /22 Y (56) = constant (57) (u +w EPa 1 prra Entrainment is given by /(a2b2) db (c ET 2 c4d) a 3 Momentum: M Buoyancy force: F = Buoyancy: B = = 4 1 pabU (60) 6) 7rabg(p-o) iab(p (o)-p) 2 (62) a The trajectory of the plume may be determined by dx U (63a) dy (63b) dz (63 c) dt Equations (44) through (63) can be integrated using a numerical integration scheme, using the jet characteristics prior to entering the bottom collapse phase as initial conditions. the plume collapse on the bottom is computed until The development of horizontal spread- ing due to collapse is less than that due to diffusion. At this point, calculation is switched to the passive diffusion phase. 22 Solution Technique Once the ambient conditions, topography of the ocean bottom, and discharge conditions have been defined, the model can be used. The discharge is described by the volumetric flow rate and density of the discharge material, the initial jet radius, and the depth and vertical angle of the discharge port. The convective descent phase of the jet is computed by integrating Equations (1) through (17) using a standard fourth-order RungeKutta integration routine. This routine simultaneously integrates the equations of motion over small increments of arc length along the jet axis, resulting in a complete history of the convective descent. If the jet encounters neutral buoyancy, its cross sectional shape is instantly transformed from a circle to an ellipse. Equa- tions (18) through (43) are then integrated by the same routine as that for the convective descent. Since many of the equations in this phase contain time derivatives, the model uses derivative routines before integration for converting time derivatives to derivatives with respect to an element of plume length, ds. Initial conditions are provided from the final step of the convective descent. The history of the plume collapse is computed until either the plume hits the bottom or the spreading of the plume due to collapse is less than that due to diffusion. If the descending jet or collapsing plume encounters the bottom, its cross sectional width is immediately transformed to a half ellipse. Equations (44) through (63) are then integrated using the 23 same routine as described above for collapse in the water column. History of the collapsing plume on the bottom is calculated until passive diffusion dominates. There are a number of numerical toefficients used in the model. Many are the same as those used by Koh and Chang1-. Table 1 lists the coefficients, and default numerical values, which may be modified during program execution. is obtained from Equation (12), and 02 is obtained from Abraham6, after Brandsma and Divoky3 corrected for the difference in the similarity distributions used in Abraham's and the present formulations. The value of 03 the entrainment coeff 1- cient for a convecting thermal, is also obtained from Abraham6. Values for 041 the coefficient for entrainment due to collapse, and -y, the coefficient used to simulate the effect of density gradient differences in causing plume collapse, are suggested by Koh and Chang; these particular default values are based on educated guesses. The default values for the drag coefficients were obtained, considering the range of Reynolds numbers expected, from diagrams presented by Hoerner7 for solid shapes in fluids. applicable to this work. However, in the absence of more relevant data, these values are used. coefficients (C drag , C. rric As such, they are not strictly , The default values for the remaining F ricrn , and F 1 ) were presented by Koh and Chang based on educated guesses, and as such are subject to revision. All default values of the coefficients are used if the user cannot, or chooses not to, supply his or her own values. of a procedure to adjust (or An outline 'tun&') some of these coefficients based on the experimental results of this investigation is presented below. 24 Table 1. COEFFICIENT Coefficients used in the present model and their default numerical values. DEFAULT NUMERICAL VALUE DESCRIPTION Entrainment coefficient for a momentum jet a2 CD Entrainment coefficient for a two-dimensional thermal 0.3536 Entrainment coefficient for a convecting thermal 0.3536 Entrainment coefficient for a collapsing plume 0.001 Drag coefficient for a twodimensional cylinder 1.3 Drag coefficient for a two-dimensional wedge CD I C drag C. fric rictn F, Equation (12) - 0.2 Drag coefficient for a twodimensional plate normal to flow 2.0 Coefficient to simulate denity gradient differences causing collapse 0.25 Drag coefficient for an elliptical cylinder edge 1.0 Skin friction coefficient 0.01 Eottom friction coefficient 0.01 Modification factor for bottom friction 0.1 25 TUNING THE MODEL The intent of this investigation was to provide information to validate and calibrate the produced water computer model. The assuxnp- tions used in the model must be verified, and the coefficients within the model must be tuned before the model can be used as a predictive tool. The procedure for tuning the model by adjusting the coeff i- cients is outlined below. A prominent feature of the plume behavior in this investigation was the collapse of the plume on the bottom. As a result, the major- ity of the experimental data corresponds to this phase of plume development and will tune mainly-those coefficients in the bottom collapse routine of the model for CDf CD 1 4 mended for use. 2' ( , 4 C C , D3 frc , F rlctn ) . The default values and c3 are fairly well established and are recoin- Due to the lack of more relevant data, default values are also recommended for y, F and C , 1 drag . The following procedure is recommended for tuning the model: Run the model at conditions similar to the experimental conditions investigated using default values for all coefficients. Check for agreement on dilution and plume width between the model output and the experimental results. Adjust to make the dilution output from the model agree with the experimental results. Adjust individually C D3 , C fric , and F rictn to make the plume width output from the model agree with the experimental data. 26 5) Iterate steps 3 and 4 until good agreement is obtained between the model output and experimental results. 27 EXPERIMENTAL MODELING III. This chapter details the experimental modeling involved in the laboratory simulation of negatively buoyant jets discharged into a crossflow current. First, the parameters involved in the modeling are introduced, then the apparatus and data acquisition system are Following this are details of the data treatment process described. Finally, the results of the laboratory and uncertainty analysis. simulation are presented and discussed. MODELING PARAMETERS In experimental modeling, certain conditions of similarity must be observed to ensure that the model test data are applicable to the TW9 kinds of conditions must be satisfied: prototype. 1) geometric similarity of the physical boundary, and 2) dynamic similarity of the flow fields. analysis. Relations for similitude are obtained from a dimensional Such an analysis yields the following independent vari- ables necessary for dynamic similarity: 1) the densirnetric Froude 1/2 Number, FR = g 0) , which is the ratio of inertial to 0 buoyant forces; and 2) the velocity ratio, P. = U/U, which is the ratio of current to discharge velocities. Since the discharge is turbulent, Reynolds number effects are negligible. The discharge in the experimental model must, therefore, also be turbulent. The dependent variables resulting from the dimensional analysis include: 1) the excess salinity ratio, IS /IS C 0 = (S C - S_)/(S 0 - S ), which is the ratio of local excess salinity to the excess salinity at discharge; and 2) the dimensionless plume half-width, W/D. 28 The independent parameters were varied in this study as follows: FR = 0.5, 1.0, 1.5 R = 0.5, 1.0, 1.5 All combinations of these variables were considered. Salinity measurements were made along a vertical traverse of the plume centerplane at X/D values of 2.5, 5, 10, 20, and 30. A schema- tic showing the plume coordinates and line of traverse is given in Figure 4. For most conditions, the plume collapsed rapidly on the bottom and spread out in a thin layer. So for many runs, the traverse would yield a measurement at only one Y/D value very close to the bottom. Consequently, most measurements were taken along the bottom at Y/D '\ 0.1. A detailed discussion of the apparatus and measuring techniques is given in the next section. A partially randomized experimental plan was developed to reduce trend errors associated with natural effects (changing barometric pressure, temperature, etc.), human activities (increasing skill or boredom), and mechanical effects (sticky instruments, hysteresis). The plan consisted of selecting at random the sequencing of sampling events. The Froude Number, FR, was first randomly selected from the possible values, then the velocity ratio, R. Following this was the random selection of the downstream distance, x/D, at which measure- ments were to be taken. This procedure was followed until all com- binations of independent variables were considered. Data collection yielded plume excess salinity ratio and plume half-width. LINE OF TRAVERSE PROBE CENTER PLANE OF PLUN&_- PLANE OF TRAVERSE EDGE OF CHANNEL Figure 4. Plane of traverse of the probe. 30 APPARATUS AND DATA ACQUISITION The experiments were conducted in Graf Hall on the Oregon State University campus. In each run, a jet of heavy salt water was dis- charged vertically upward, from a false bottom, into a towing channel. Information desired from the experiments included dilution, as expressed by the excess salinity ratio, and plume half-width. Salinity measurements were taken of the discharge solution, ambient fluid, and along the vertical centerplane of the plume at several stations down- stream from the discharge port to evaluate the excess salinity ratio. Plume width measurements were made using photographs of dyed jets. The experimental apparatus, electronic instrumentation, and sequence of events termed a run are described in detail below. A schematic of the apparatus is given in Figure 5. The apparatus consisted of a salt water discharge into a 12.2 m x .6 m x .9 m towing channel. Two carriages containing the discharge and conductivity measuring systems were mounted on rails along the top of the channel and connected to a motor driven tow cable. The discharge system, supported by the first carriage, included a salt water reservoir, a main discharge valve, a flow control valve, 1.3 cm PVC pipe for the manifold, and 2.5 cm PVC pipe for both the reservoir outlet piping to the manifold and the discharge port. A false bottom was used to minimize the disturbance from the discharge piping along the channel bottom and to allow the discharge port to be flush with the bottom. 31 POTENTIOMETER GEARED TO VERTICAL HEIGHT PROSE SALT WATER RESERVOIR DC DRIVE MOTOR MAIN DISCHARGE VALVE FLOW CONTROL VALVE FALSE BOTTOM CHANNEL BOTTOM BALL-SCREW DRIVE POTENTIOMETER SIGNAL PROBE SIGNAL 000 O 'I p'i 1101 r 0000000 I I - I I 000 CARRIER LIFIER LIGHT-SENSITIVE PRINT Figure 5. Schematic of the experimental apparatus and electronic instrumentation. 32 The sealed salt water reservoir was kept at constant head by bubbling air in as the water level dropped. voir is shown in Figure 6. The constant head reser- As water is discharged from the reservoir, air pressure pushes the water from the bubbling tubes until air issues from the tubes into the reservoir. In this manner, the level of ambient air pressure is kept constant at the level of the bottom of the bubbling tubes. Baffles were included in construction of the reservoir td damp out waves that would form when the reservoir was towed. The reservoir was filled with salt water of the proper salin- ity and sealed with a rubber stopper prior to each run. A second carriage supported the conductivity measuring system, responsible for measuring the electrical conductivity in the field of the jet. A conductivity probe (Figure 7) connected to a Tektronix Carrier amplifier monitored the electrical conductivity at given values of X/D and Y/D. Calibration of the probe prior to its use provided information to obtain salinity values from the conductivity measurements. The probe was mounted on a rod that traversed veri- cally through the plume. The mechanism to move the probe vertically employed a double-ball-screw drive powered by a remotely controlled D.C. motor. A potentiometer geared to this mechanism monitored the vertical position of the probe. The probe was positioned laterally on the rod such that it followed the vertical centerplane of the jet, as shown in Figure 4. The conductivity signal from the Carrier ampli- fier arid the potentiometric position signal were recorded using a Honeywell Visicorder (see Figure 5) FILLING STOPPER SEALED TANK BUBBLING TUBES n 0 C 0 0 BAFFLES MAIN DISCHARGE VALVE ATMOSPHERIC PRESSURE LEVEL AMBIENT WATER LEVEL Figure 6. Schematic of the constant head salt water reservoir. 34 ELECTRICAL LEAD ThNGS I LN LEADS GROUNDING CTR0DE PLATINUM ELECTRODE 4 Figure 7. 3nm H- Enlarged view of conductivity probe. 35 As mentioned previously, the rapid collapse and spreading of the plume into a thin layer on the bottom required many measurements close to the bottom. Because the grounding electrode protruded from the end of the probe, measurements attempted directly on the bottom grounded the probe. To avoid this, the probe was positioned at the lowest pos- sible height, about Y/D "-' 0.1. The discharge flow rate was adjusted using the flow control valve. Flow measurements were made by observing the reservoir level drop over a given length in time. Temperature measurements of the salt water and ambient were made with a mercury-in--glass thermometer. The fluids were kept within about 100 of each other during the experiments. For FR = 1.5, the nominal discharge velocity was 9.1 cm/sec and the nominal difference between discharge salinity and ambient salinity was about 220/00 (parts per thousand), depending on ambient salinity. At FR = 1.0, the nominal U difference of 47°/oo. was 8.9 cm/sec, with a nominal salinity For FR = 0.5, U salinity difference was 150°/oo. = 8.2 cm/sec and the nominal Ambient salinity varied from 00/00 to a high of about 8°/oo at times during the FR = 0.5 cases. The conductivity probe was calibrated using standard salt solutions of differing salinities. A salinometer from the OStJ School of Oceanography was used to standardize the salt solutions. The uncer- tainty in the salinity measurements using the salinometer was about ± 0.2%. Calibration of the probe was obtained by immersing the probe into these standard solutions and recording the corresponding signal with the Honeywell Visicorder. Since the calibration drifted slightly 36 on occasion, the calibration curve was checked and adjusted periodically. Figure 8 shows a typical calibration curve for the probe. Dilution Measurements In order to have reasonable confidence in the dilution results, duplicate runs were needed for each FR and R condition at each X/D station downstream from the port. Typically three runs were made at each station and condition; however, when two points showed favorable replication, a third run was not made. Due to the multitude of runs, exact duplication of conditions was impossible. The resulting stan- dard deviation was about 6% for the Froude Nunther and about 6.5% for the velocity ratio. The X/D and Y/D values were reasonably exact. The sequence of events which constitute a run for measuring dilution is described as follows: Calibrate the conductivity probe and the potentiometer connected to the vertical height control. Prepare and align the traversing mechanism for the particular downstream distance, X/D and vertical height, Y/D (usually starting from the bottom). Fill the reservoir with salt water of desired salinity. Adjust the flow control valve to attain the desired discharge velocity. Measure the discharge salinity and temperature and ambient salinity and temperature. Adjust towing speed to desired value. Open main discharge valve to begin the discharge. 37 2 4 6 8 10 12 14 PROBE OUTPUT(DIVISIQNS) Figure 8. Tyoical calibration curve for the Conductivity probe. 38 Initiate tow. After towing speed is reached, begin traversing the jet with the probe. At the conclusion of the tow, record the distance of the tow and the time associated with that towing distance to measure the towing speed. Shut the main discharge valve off. Record the reservoir level drop and the associated time for the drop to measure the volumetric flow rate. Use continuity to cal- culate the average discharge velocity. Plume Width Measurements Photographs of dyed jets using a 35 nmi camera provided plume width measurements. A 4 cm square grid was drawn on the false bottom to provide a reference for the measurements. Runs were made similar to that described above, except salinity measurements were not needed. Instead, top view color transparencies were taken of the dyed plume for each FR and R condition investigated. These photos were then used to plot plume width, W/D, as a function of downstream distance, X/D, for each condition. Another study was conducted to determine the character of the boundary layer along the upper half of the false bottom. Velocity measurements within the boundary layer were made using a Thermal Systems, Inc. hot wire anemometer. During a tow, the sensor traversed the boundary layer vertically to provide velocity measurements at various heights for a given X,D station. These measurements were plotted to give the velocity distribution within the boundary layer. 39 In general, the experimental apparatus operated as desired and had acceptable error. A couple of problems arose in the course of experimentation, including: 1) variations in towing speed at slow speeds, which required great care to ensure that measurements were taken only over the portion of the channel with uniform towing speed; and 2) fouling of the conductivity probe when using high saline discharges, which required periodical cleaning of the probe with methyl alcohol. At the end of the experimentation, an effort was made to measure conductivity directly on the bottom by modifying the apparatus A ulifterfi plate, illustrated in Figure 9, was attached to slightly. the false bottom to allow for bottom measurements. Measurements were taken at the end of the lifter and represent actual plume bottom conductivities. ments. Time did not allow for replication of these measure- Rather, the information resulting from this effort was used to verify that bottom salinities were significantly higher than at Y7D " 0.1. DATA TREATMENT A typical Visicorder plot of the conductivity and position signals is shown in Figure 10. For each probe position, the conductivity signal was examined and by visual scrutiny the mean (time averaged) value of the signal was determined. This value and the value ascribed to the position signal were referenced back to their respective calibration curves to obtain a salinity value at the associated probe height. A flowchart outlining the data treatment process is shown in Figure 11. 40 LIFTER PLATE CHANNEL CONDUCT IV ITY BOTTOM PROBE FALSE BOTTOM mm / / / // / Figure 9. / / / / / / Section view showing lifter plate used for measuring conductivity on the false bottom. 41 C(N)UCTIVfly PROBE SI(NAL INCREASING SALINITY PND PROBE HEIGHT POTENTI C(9EJER PUS I TI'SI Ei"JAL Figure 10. Typical Visicorder print of conductIvity and position signals. 42 DATA TREATMENT Read Instrument Output Record Values and Other Importart Information Enter Data on Data File Normalize Data and Compute Dimensionless Parameters by Computer Statistically Analyze Eliminate Outlying Data Points Data. Plot Data on Graphs, Draw Curve Through Ilean of Data Groups Run Regresslon Analysis on Data Figure 11. Flowchart showing data treatment process. 43 These values and other important information were recorded on The data for all runs was assembled and entered on data data sheets. files in the computer. A computer program then normalized and re- duced the data to the forms iS /iS c 0 , FR, R, X/D, Y/D. This output was statistically analyzed by computing the mean and standard deviation for each Froude Number and velocity ratio condition investigated. Using a method known as the Chauvenet's Criterion9, data with significant deviation from the investigated conditions were eliminated from the data base. The normalized data was then plotted on graphs, and curves were drawn through the mean of each data group. An example of the plots and data points for excess salinity ratio as a function of X/D and Y/D are shown in Figures 12 and 13. Some of the data points have been shifted off the true X/D position in order to clarify the plots. Appendix A contains all the curves obtained in this experimental inLike the others, the curves are drawn through the mean vestigation. of the data groups, and are restricted to the X/D range investigated. A table of all data contributing to the curves in Appendix A is given in Appendix B. In addition to having plots with curves drawn through the mean of data groups, a regression analysis was performed to offer an unbiased examination of the collected data. Employment of the Statisti- cal interactive Programming System (SIPS) available at Oregon State University's Computer Center provided a least-squares regression curve fit. The model proposed to SIPS was a logarithmic transforma- tion of the function FR = 1,L4L R = 1.02 A Y/D0 0 Y/D0.1 0 (I) (j U F 0 0 0 10 20 3) 1() FOUZItffAL DtSTN'cE - X/D Figure 12. Example of typical excess salinity raho data, as a function of X/D, arid its' represenLajve curve, 0,6 0.5 FR = 1.01 R = 1.118 XJD = 5 0.2 0 0. ] 0 ' 0 1 0 0.2 0.Lj 0,6 0.8 1.0 VERTICAL If IGIIT - y/lJ Figure 131. Examplo of typical excess salinity ratio data, as a function of VD, and its' representative curve, 46 1s C = exp(a) (X/D) b d c (R) (FR) 0 The transformed equation LS ln(-) - a + bln(X/D) cln(R) + dln(FR) provided the unknown coefficients (a,b,c,d) in linear form as required for a least-squares linear regression analysis. UNCERTAINTY ANALYS IS An uncertainty analysis of the data was performed to obtain a general indication of the quality of the data. The standard approach to uncertainty analysis requires knowledge of the error in the rnea- sured quantities, and the mathematical relationship between the measured quantities and the desired result, before the propogation of errors to the final result can be assessed9. Since the process of making salinity measurements was involved (it required making stan- dard salt solutions, diluting a portion of each solution for the salinometer measurements, calibrating the conductivity probe using the standard solutions, making a conductivity measurement, and relating instrument output back to the calibration curve to arrive at a salinity value), an estimate of the error in the salinity measurement would at best be an educated guess. As such, the standard approach to uncertainty analysis was abandoned. Instead, 90% confidence inter- vals were estimated for the data groups using a method for small data samples outlined by Ang and Tang10. Figure 14 is a repeat of Figure 12 with the 90% confidence interval included to indicate the quality of the data. FR = 1,LI11 R = L02 0 (I) 0 U V) Y/r=0 YiD0.1 90% ConfIdence Interval 10 20 FKJRIZCTAL MSTNCE Figure 14. XiB A repeab of Figure 12 with 90% confidence inberval included to indicate the quality of Lhe experimental data. 48 Three factors explain the spread of the data illustrated by the confidence interval: 1) the small number of data points within each data group; 2) usual measurement errors or uncertainties; and 3) the sensitivity of excess salinity ratio to vertical height, as shown in Figure 13. Small variations in probe height around Y/D = 0.1 yield significant deviations of excess salinity ratio from that at Y/D = 0.1. Since it was virtually impossible to align the probe exactly at Y/D 0.1 for each run, the vertical sensitivity added to the data spread. The data obtained in this investigation, however, was suffi- cient to define the functional relations between the variables and to recognize established trends. The results of the experimental inves- tigation are discussed in detail below. RESULTS The effects of FR and R on dilution are best demonstrated by the nf plots C versus X/D and Y/D for the various combinations of FR 0 and R, as given in Appendix A. The individual effects of Froude Number and velocity ratio on dilution are described as follows: 1) Within the range of values investigated, the effect of velocity ratio, F, on dilution is minor, as demonstrated in Figure 15. All measurements were made within the boundary layer above the false bottom (see Figures 29-31) . Since the magnitude of the velocity within the boundary layer at Y/D 0.1 (where most measurements were made) was much lower than the freestrearn current, the effects of the .25 FR = :1.01 .20 20 X./D 0 A Y/D=O 0 V/DuO,1 C,, U C.,) .15 10 MS 0 0 00 0.- 0.5 0 1,0 1.5 WLOCI1Y RATIO - R Fiqure 15. Excess salinity ratlo as a function of velocity ratio. 50 ambient current were reduced. As a result, the net effect of the velocity ratio on dilution was found to be small. The most critical parameter affecting dilution is the 2) Froude Number, FR. It was found that dilution in- creases with decreasing FR, as shown in Figure 16. The dense fluid associated with low FR numbers spreads very rapidly on the bottom following collapse of the plume. This rapid spreading is thought to increase entrainment and thereby increase dilution. The results of the photo study of dyed jets, providing plume width information, are presented as plots bf plume half-width versus X/D, for the various FR and P. conditions investigated, in Figures 17-19. The results indicate that: 1) plume width increases with decreasing velocity ratio; and 2) plume width increases with decreas- ing Froude Number, supporting the explanation of greater spreading with lower FR. The regression analysis on the data yieldsthe following regression model: Ls - (0.363) (x/D)"02 (R)024 (FR)277, 0 valid for Y/D 0.1. An examination of the exponents in the regression model supports the results presented earlier. The Froude Number, with the largest ex- ponent, has the greatest effect on dilution. On the other hand, the velocity ratio has the smallest exponent and hence has the least effect on dilution. R 1.00 X/D = 5 X/D10 - X/D=30 V/B 0.1 .20 / 0,5 1,0 1.5 FROUDE NUMBER - FR Figure 16. Excess salinity ratio as a function of Froude Number. 2.0 10 / / / / / I/I FR=0.5 1/ / -12 0 R=0.5 0- -0 R1.0 o----0 R=1,5 0 U Li 8 HORIZONTAL DISTANCE - X/D Figure 17. Plunie half-width as a function of X/D and R for FP = Ob. 12 10 / I/ 7,, 1/' / IL / 1 2 / ,' 7' FR1:0 0 0 R10 G-- 0 0 11 8 12 20 16 HORIZONTAL DISTANCE - X/D Figure lB. Plume haif-width as a function of X/D and B. for FR 1 .0. FR=L5 0 0 R=O,5 0- -0 R=L0 ° R=1,5 ° 8 12 HORIZONTAL DiSTANCE 16 20 X/D Figure 19. Plume half-width as a function of X/D and R for FR = 1.5. 2L 55 The regression analysis results are shown graphically, and corn- pared to the data average curves, in Figures 20-28 for the selected values of FR and R. The graphs show reasonable agreement in shape and trend between the proposed model and the data average curves for most of the conditions investigated. The relatively low value for the coefficient of determination (R2 = 0.53) suggests that: 1) im- provements could possibly be made in the proposed model to better fit the data, and/or 2) the spread of the data may affect the regression analysis to the extent that a good fit cannot be obtained. The velocity distributions within the boundary layer over the false bottom for each of the R values investigated are presented in Figures 29, 30, and 31. The graphs indicate that virtually all salin- ity measurements were made within the boundary layer. Due to the complexity of ambient currents along the ocean bottom, no attempt was made to replicate the ocean bottom conditions in this investigation. Instead, the study provides information on the actual velocity distribution within the boundary layer over the false bottom associated with the data obtained. Since turbulence is a second order effect, the difference in boundary layer between the experimental model and actual field conditions should have a negligible effect on the results. 0.125 I I I I FR = 0,50 R = 0.50 0.10 fr0 0- 0 V/i) 0,1 DATA ATRNES REGRESSIIflf4I(L .075 ;.ty50 10 20 FURIZ1ffAL D1STM Figure 20, 30 LIt) - X/D Comparison of regression model with data averaqes curve FR 0,5, R = 0.5. for the condit:iong; 0.125 FR = R = 0,99 0.10 Y/DO.1 -o DATA AVERAGES o REGRESSI tfla C) .050 .cY25 20 3) -j Lb HOMZCt'LTPL MSTi4E - XJD Fiqure 21. Comparison of regression model with data averages curve for the conditions: FR = 0.5, R 0.99. FR = 0.50 R = 1.1i7 Y/D = 0.1 WTA AVERAGES RE3RESSI 0 10 fI[L 20 HORIZ(1iThL MSTN4E - )VD Figure 22. Comparison of regression model with data averages curve for the conditions: FR 0.5, R = 1.47. 20 uoKI21Ta Figure 23. iSTP4CE - XJD cornpar° regressiOfl model with data av6raq for the cofld° FR = 1.01, R = 0.48. curve FR = 1.0]. R = 1.01 v/f) -. 0.1 ETA AVERPLES RERESSJt 0 2 10 20 30 tkRJ711'lTAL DISTP14E Fiqure 24. JEL Ito X/[) Comparison of reqression model with data averages curve for the conditions: FR 1.01, R = 1.01. FR = 1,01 R = LLI8 Yin o,i LVTA AEMfS 0 1ESSI1J tUIEL 0,2 0.1 - 0 0 10 20 33 I10(UZ1SffAL D)STP1KE - XJD Figure 2. Comparison of regression model with data averages curve for the conditions: FR 1.01, R 1.48. 0.6 FR = 1MLI R=0.52 0.5 - V/B - 0,1 IYTA ARAGES REGRESSILli WEL - cD 0.3 0,2 0.1 - if) 0 20 30 L10 HORIZ(Nf/L MST!E - XJD Figure 26. Comparison of regression model with data averages curve for the conditions FR = 1,44, R 0.52. 50 0.6 FR = 1.LILt 0.5 R = 1.02 Y/D A- -A 0 0 0.1 DATA AVERA(iS REGFSSIct1 MJDEL 0.3 0.2 0,1 0 L I 10 20 IERIZTL D!STJN Figure 27. I LiO - XJD Comparison of regression model with data averages curve for the conditions: FR 1.44, R = 1.02. 0.6 FR = 1.'14 R = 1.49 0.5 A0 0 Yin 0.1 DATA AVER(TS IGRESSII fvTIL (1 0,3 0.2 0.1 50 VERTICAL HEIGHT - V/I) F'igure 29. Velocity distribution in the boundary layer above the false bottom for R = 0.5. 1.0 0,8 8 -4 0.4 R = 1.00 -0-0,2 0,25 0.50 0.75 a X1DJ5 o X/D=30 1.00 1.25 VERTICAL hEIGHT - V/I) Figure 30. Velocity distribution in the boundary layer above the false bottom for R = 1.0. 1.50 0.8 0,6 0.L1 0.2 \iERTICAL lElGif - Y/B Figure 31. Velocity distribution in the boundary layer above the false bottom for P = 1.5. 68 IV. CONCLUSIONS The purpose of this investigation was to conduct laboratory simulations of negatively buoyant jets discharged vertically upward into a crossflow current to obtain information useful in the validation and calibration of the produced water computer model. The re- suits of the experimental modeling effort may be summarized as follows: The Froude Number has the greatest effect on dilution. Both dilution and plume width increase with decreasing Froude Number. Within the range of values investigated, the velocity ratio has a minor effect on dilution. Plume width decreases with increasing velocity ratio. In the analytical portion of this study, the produced water computer model was reviewed, the development of the mathematical model was presented, and the solution technique used in the model was discussed. Then a procedure was outlined to tune the coefficients with- in the model using the experimental results of this investigation. Using the experimental results presented here, the near and intermediate portions of the model can be validated as representing actual field situations and calibrated for use as a predictive tool to determine the fate of produced water disposal. 69 V. REFERENCES Davis, L. R. and Shirazi, M. A., A Review of Thermal Plume Modeling, Keynote Address, Proceedings of the 6th International Heat Transfer Conference, Toronto, Canada, August 1978. Koh, R. C. Y. and Chang, Y. C., Mathematical Model for Barged Ocean Disposal of Wastes, U.S. E.P.A. Report EPA-660/2-73-029, December 1973. Brandsma, M. G. and Divoky, D. J., Development of Models for Prediction of Short-Term Fate of Dredged Material Discharged in the Marine Environment, U.S. Army Engineer Waterways Experiment Station Report D-76-5, May 1976. Fischer, H. B., A Method for Predicting Pollutant Transport in Tidal Waters, U.C. Berkeley Water Resources Center, Report 132, March 1970. Brandsma, M. C., Davis, L. R., Avers, R. C. and Sauer, T. C., A Computer Model to Predict the Short-Term Fate of Drilling Discharges in the Marine Environment, Proceedings of the Symposium: Research on Environmental Fate and Effects of Drilling Fluids and Cuttings, Lake Buena Vista, Florida, January 1980. Abraham, C., The Flow of Round Buoyant Jets Issuing Vertically Into Ambient Fluid Flowing in a Horizontal Direction, Proceedings: Fifth International Conference on Water Pollution Research, San Francisco, Paper 111-15, July 1970. Hoerner, S. F., Fluid Dynamic Drag, Published by the Author, Brick Town, New Jersey, 1965. Wu, F. H. Y. and Koh, R. C. Y., Mathematical Model for Multiple Cooling Tower Plumes, U. S. E. F. A. Report EPA-6007-78-102, 1978. Schenck, H., Theories of Engineering Experimentation, 3rd Ed., McGraw-Hill, New York, 1979. Ang, A.H-S. and Tang. W. H., Probability Concepts in Engineering Planning and Design, John Wiley, New York, 1975. APPENDICES 70 APPENDIX 1\ What follows are graphs of the experimental data obtained in this investigation. The graphs include centerline excess salinity ratio plotted against downstream distance, X/D, and vertical distance, Y/D, for conditions of FR = 0.5, 1.0, 1.5 and R 0.5, 1.0, 1.5. curves presented are drawn through the mean of the data groups. The For clarity, some of the data points have been shifted off the true X/D position. 0 25 FR = 0.50 R = 0.50 Y/D 0.1 0.2 (40 U C,) ':3 0.15 I.- ; Oil 0105 0 0 10 .1 20 30 HORIZONTAL DISTANCE - X/D Fiqure ii-l. Plume centerline excess salinity ratio versus X/D, for FR= 0.50,R = 0.50, and Y/D 0.1. 025 0.50 R = 0.99 0.1 YID FR 0.2 0 U) U U) 0 :: 0.05 o 0 0 p I0 0 0 00 20 30 HORIZONTAL DISTANCE - X/O Figure A-2. Plume centerline excess salinity ratio versus X/D, for FR = 0.50, F = 0.99, and Y/D 0.1. 0.25 FR = 0.50 R 1.147 Y/D0.1 0.2 0 (4 U (4 cJ c. 0.15 0.1 0.05 0 A 0 0 I 10 20 30 HORIZONTAL DISTANCE - X/D Figure A-3. Plume centerline excess salinity ratio versus X/D, for 0.1. FR = 0.50, R = 1.47, and Y/t) FR = 1.01 R A Y/D Y/D 0 0i 0 A 10 20 30 HORIZONTAL DISTANCE - X/D Figure A-4, Plume centerline excess salinity ratio versus X/D, for 0.48, Y/D = 0, and Y/D 0,1. FR LO 0.6 0.5 0.1 0.2 O.'4 0.6 0r8 VERTICAL HEIGHT - Y/D Figure A--5. Plume centerline excess salinity.ratio versus Y/D, for 1.01, R = 0.48, and X/D = 2.5, 5 and .10. F1 1.0 0.6 0 FR = 1.01 0.5 R A V/U 0 A V/U 1.01 0 0.1 0,1 A A A 0 0 10 20 30 HORIZONTAL DiSTANCE - X/D Figure A-6. Plume centerline excess salinity ratio versus X/fl, for FR = 1.01, R = l0i, Y/D = 0, and Y/D 0.1. '10 0.6 I I I FR = 1.01 0.5 R=1.01 X/D = 2.5 - X/D = 5 0 - - - X/D = 10 . 0.3 0.2 0.1 0 0.2 0 0.11 0.6 0.8 VERTICAL HEIGHT - Y/D Figure A-7. Plume centerline excess salinity ratio versus Y/D, for FR = 1.01, R = 1.01, and X/D = 2.5, 5 and 10. 1.0 0.6 I I I 05 FR = 1.01 R 0 A C,, (-I C.') . 0 Y/D nU. I- 1148 Y/D =0 0.1 £ 0.3 a L) 0,2 8 0.1 A £ 10 0 20 HORIZONTAL DISTANCE Figure A-8. '30 X/D Plume centerline excess salinity ratio versus X/D, for 0.1. FR = 1.01, R = 1.48, Y/D = 0, and Y/D LjQ 0.6 0.5 FR = 1.01 R 1.48 X/D = 2.5 - - X/D = 5 0.1 0.2 0.4 0.6 0.8 VERTICAL hEIGHT - Y/D Fiçure A-9. Plume centerline excess salinity ratio versus Y/D, for FR = 1.01, F = 1.48, and X/D = 2 5 and 5. 1.0 0.6 0.5 0,1 0 10 20 HORIZONTAL DISTANCE Figure A-JO. 30 X/D Plume centerline excess salinity ratio versus X/D, for FR = 1.44, R = 0.52, Y/D = 0, and Y/D 0.1. 110 0.5 FR = 1,L14 Ii 0,52 X/D 2.5 ___ - X/D= 5 - -X/D= 10 >_J A 'J. C/) 0.1 0.2 0.6 0.8 VERTICAL HEIGHT - Y/D Figure A-il. Plume centerline excess salinity ratio versus Y/D, for FR = 1.44, R = 0.52, and X/D = 2.5, 5 and 10. 0.6 0.5 FR = 0 C,, R = .1.02 Y/D = 0 0.1 U 0 Y/D 0,1k : 0.3 A 0.2 0.1 0 10 20 30 HORIZONTAL DISTANCE - X/D Figure A-12. Plume centerline excess salinity ratio versus X/D, for 1.02, Y/D = 0, and Y/D 1.44, R 0.1. FR LQ 0.6 FR 0.5 = 1.02 X/D=2.5 0 C,, C') 3 1.1111 - X/D = 5 = 10 A us c 5- I- 0.3 3 0.2 C-i 0.1 0-0 0.2 0.11 0.6 - I 0.8 VERTICAL HEIGHT - Y/D Figure A-13. Plume centerline excess salinity ratio versus Y/D, for 1.02, and X/D = 2.5, 5 and 10. FR 1.44, P 1,0 0.5 FR R= 1.'i9 It Y/D 0 Y/D 0 01 0 £ 0 óôó 0.1 4 0 10 20 30 hORIZONTAL DISTANCE - X/D Figure A-i4. Plume centerii!ne excess salinity ratio versus X/I), for 1.44, R = 1.39, Y/D = 0, and Y/D 0.1. FR tO 0.6 FR 0.5 R 1.44 1.49 2.5 ----X/D=10 -X/D5 X/D (I) 4 Lii L) 11 I). 0.1 ___J 1- 0.2 0.4 0.6 0.8 VERTICAL HEIGHT - Y/D Figure A-iS. Plume centerline excess salinity ratio versus Y/D, for FR = 1.44, P. 1.49, and' X/D = 2.5, 5 arid 10. 1.0 86 APPENDIX B Appendix B contains a complete table of the experimental data obtained in this investigation. The data, normalized by a computer program, include FR, R, X,'D, Y/D, iS/IS, U, S, S, T, T. In this listing U FR = Discharge densimetric Froude Number / po-p= p0 R = U /U 0 gD = Velocity ratio X/D = Dimensionless downstream distance from the discharge port, in port diameters Y/D = Dimensionless vertical distance from the discharge port, in port diameters is/IS 0 0 S -s SQ -s - Centerline excess salinity ratio CO = Discharge velocity, in cm/s S = Discharge salinity, in ppt (°/oo) Ambient salinity, in ppt (°/oo) T T = Discharge temperature, in Ambient temperature, in ac C 87 xiJ 1.L, ,L45 .50 5.3 .50 20.3 0 C . .,, .22 ..0 .05 .-.' .:3 23.0 0.3 :7.3 '.0 23,3 0.3 :7.0 7 , 0.0 .IJ .33 1.33 .53 2. 1 33 .55 5*0 .J * :0 3 i.L+2 .52 20.0 .13 .33 I .52 30.3 .0 I : 2.5 .J ;:; .33 e_L UI J 4 1 -7 .t C SU , .33 3 6.0 16.0 U7 Ii .06 .72 22.0 3.0 .5 .72 22.3 0.3 0.0 :.0 0.00 ..J ._.,. :6.3 :s.a :.: 1U - I, .55 :3.3 .13 .55 ?I:3 22.3 0.3 16.8 160 .31 .33 23.: . _0. - a 1) ,7 'r _4J .j :6.5 :.o . - 4n * .13 i...#o ,5 . 88 V/C 1.38 .95 5.3 .13 1.38 .95 Z0.j .13 55 C /t.S 0 U S 0 22. .31 37 65 2.00 0 0 3.3 15.5 3.3 :6.5 1.G 1.3 1.85 10.3 .13 .12 22.5 0.3 :.5 :5.5 1.39 1.06 2.5 ..0 .53 .23 22.5 0.0 16.5 :,0 1.03 30.3 .05 22.0 3.3 b.3 :5.3 :.so i.C3 L.Q3 2:.3 C.3 :5.3 :5. _, -tu.0 U.0 - 1.58 s')L 4 .65 .13 .55 0.00 .13 .05 3.03 .5 .:3 '. - a r _..JJ 1.36 I 1.12 51 S 1.51 . ri 1.03 i. 2O s.o ) .55 .07 - .13 .a7 .57 ?.32 10.0 .12 .05 . .2 ' 33 . . .13 .3 -, 5.3 1.03 13.0 . 4S_/ :2.3 .7 .5, .: 33;; J. r. ) ' - 22.2 3.2 6.3 .3? 22 0.3 :o.0 :.3 ,79 233 . :6.5 :6.3 3.2 :5.5 7.J 15 - .:3 23.0 89 FR 3 / R I0 tS C/L\S 0 T 1.5; 23.J .3 .37 3.3S 22.5 r.3 :6.5 :.o 5.3 .0 .55 .3: 9,2L 22.5 3.3 5.5 7.3 - *J .12 -, , .L I -- .7 .23 1.56 1.5 30.0 .13 1.1*3 23.3 .13 4-- .10 :.L+3 13.3 .1.3 .1 1.1*7 1.1+7 j.L3 2.5 .55 ..0 .L1+ L.147 1.1+3 5.3 .0 j.J0 .39 0.0 16.5 :7.0 9.3L 22.0 3.3 16.3 :.0 2. 3.0 S.3 937 22.0 G. 9.:7 22.3 .32 ,t .1 .32 .ss 22. .0 .55 ."4 .72 .0 i5.3 1.3 3.0 6,3 :. 1.1*3 1.1*1 30.3 .1.3 .3 22.3 3.3 16.3 5,3 1.1+3 1.1*: 1+0.3 .13 .07 22.3 0,3 ..S.G 1. 1.1+5 1.57 :0.0 .: ,:7 :3.0 :5.5 :5.0 .4 -.1 - 1.35 1.5 .j 2.3 .33 .._J . ,:o a3. .5 , o.5 :5.5 90 x io 2,5 C .:: .'.7 .pi 33.3 .33 5,3 1.39 L.L 1.39 47.5 .13 7.5 S 3.3 17.5 :.5 7.S , Q _) S.) 3.3 . .Li .4 0 0 , .13 , 1.10 U .: .44 1.04 /iS 0 00 3 .07 q,4 47.E .5 17.5 +7.3 .5 17. 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