Chan Wei
Lim Zhong Hui
Tan Hong You
M4
Laminar flow
 Also known as
streamline flow
 Occurs when the
fluid flows in
parallel layers, with
no disruption
between the layers
 The opposite of
turbulent flow
(rough)
Laminar flow
 In fluid dynamics (scientific study of properties of
moving fluids), laminar flow is:
 A flow regime characterized by high momentum
diffusion, low momentum convection, pressure and
velocity independent from time.
*momentum diffusion refers to the spread of momentum
(diffusion) between particles of substances, usually
liquids
Laminar flow
 Laminar flow over a flat
and horizontal surface can
be pictured as consisting of
parallel and thin layers
 Layers slide over each
other, thus the name
‘streamline’ or smooth.
 The paths are regular and
there are no fluctuations
Turbulent
Flow
Laminar Flow
Laminar flow
 3 Conditions
 fluid moves slowly
 viscosity is relatively high
 flow channel is relatively small
 Blood flow through capillaries is laminar flow, as it
satisfies the 3 conditions
 Most type of fluid flow is turbulent
 There is poor transfer of heat energy!
Turbulent flow
 Usually occurs when the liquid
is moving fast
 The flow is ‘chaotic’ and there
are irregular fluctuations
 Includes:
 Low momentum diffusion
 high momentum convection
 rapid variation of pressure and
velocity of the fluid
 Good way to transfer thermal
energy
Turbulent Flow
 The speed of the fluid at a point is continuously
undergoing changes in both magnitude and direction.
Examples of turbulence
 Oceanic and atmospheric layers and ocean currents
 External flow of air/water over vehicles such as
cars/ships/submarines
 In racing cars, e.g. leading car causes understeer at fast
corners
 Turbulence during air-plane’s flight
 Most of terrestrial atmospheric circulation
 Flow of most liquids through pipes
Reynold’s number
 A dimensionless number in fluid mechanics
 Dynamic Pressure : Shearing Stress
 Thus, it quantifies the relative importance of these two types
of forces for given flow conditions.
 Arises when performing analysis of fluid dynamics
 Can be used to determine dynamic similitude in such cases.
Concept used in the testing of models, e.g. testing miniature
airplanes/submarines
Dynamic Pressure + Shearing Stress
 Dynamic Pressure
 The pressure of a fluid
which results from its
motion
 Formula:
 Shearing Stress
 Measure of the force of
friction from a fluid
acting on a body in the
path of that fluid
 Formula:
Fluid Density
Fluid Velocity
Weight Density
of Water
Average
water
depth
Water
Surface
Slope
Reynold’s number
Flow in a pipe or liquid
 p is the density of the fluid
 V is the mean fluid velocity
 D is the diameter
Dynamic Pressure
 Q is the volumetric flow rate
 μ is the dynamic viscosity of the fluid
 v is the kinematic velocity of the fluid
 A is the pipe cross-sectional area.
Shearing Stress
Reynold’s number
 The Reynold’s number can be used to determine if a
flow is laminar, transient or turbulent
 Laminar when Re < 2300
 Turbulent when Re > 4000
 Transient when 2300 < Re < 4000
Spermatozoa
1×10−4
Blood flow in brain
1×102
Blood flow in aorta
1×103
Acknowledgements
 http://www.geo.wvu.edu/~jtoro/geol101/streams/lami
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nar%20flow.jpg
http://www.britannica.com/EBchecked/topic/328742/l
aminar-flow
http://en.wikipedia.org/wiki/Laminar_flow
http://www.answers.com/topic/laminar-flow
http://www.cosmosmagazine.com/files/imagecache/f
eature/files/20071217_physics.jpg
http://en.wikipedia.org/wiki/Turbulent_flow#Exampl
es_of_turbulence
Acknowledgements
 http://anordinarymom.files.wordpress.com/2008/11/ai
rplane-turbulence-copy.gif
 http://www.engineeringtoolbox.com/reynoldsnumber-d_237.html
 http://en.wikipedia.org/wiki/Dynamic_similitude
 http://www.engineeringtoolbox.com/reynoldsnumber-d_237.html