Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Modeling and numerics for (shallow) (water) flows Part 2 : Beyond the Saint-Venant system E. Audusse . LAGA, UMR 7569, Univ. Paris 13 ANGE group (CETMEF – INRIA – UPMC) April 3, 2013 E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Beginning of the story I Saint-Venant system with sources ∂t hu + ∂x I Numerics: Finite volume method I I I ∂t h + ∂x hu = 0, hu 2 + gh2 /2 = −gh ∂x b Positive (and entropic) scheme Well-balanced scheme Softwares MASCARET, TELEMAC 2D (EDF-LNHE) http://www.opentelemac.org/index.php/presentation?id=17 FULLSWOF (Univ. Orléans) http://www.univ-orleans.fr/mapmo/soft/FullSWOF/ E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model A discriminant test case ? E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Joint work with I ANGE group J. Sainte-Marie, M.O. Bristeau, Y. Penel, P. Ung, N. Seguin, E. Godlewski I EDF LNHE – Saint-Venant Lab. N. Goutal, M. Jodeau, S. Boyaval I Academic partners F. Bouchut, C. Berthon, C. Chalons, O. Delestre, S. Cordier... E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Saint-Venant system Saint-Venant – Exner system Finite Volume Method ∂t u + ∇ · f (u) = 0, I u ∈ Rp , f : Rp → R2×p Integration on the prism Ci × [t n , t n+1 ] X Uin+1 = Uin − σijn F (Uin , Ujn , nij ) j∈V (i) with σijn ∆t n |Γij | = , |Ci | F (Uin , Ujn , nij ) Z t n+1 ≈ f (U(t, s)).nij dtds Γij E. Audusse Z tn Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Saint-Venant system Saint-Venant – Exner system Relaxation solver I Godunov scheme I I I Relaxation models : Introduction of a larger system I I I I I Consistency, Stability Complexity : Solution of the Riemann problem that is hyperbolic (with LD fields) that formally approaches the original ones that ensures some stability property for which the (homogeneous) Riemann problem is easy to solve Numerical algorithm I I I Definition of auxiliary variables from physical ones Solution of the Riemann problem Computation of the physical variables at the next time step (Chen et al. [94], Jin-Xin [95], Bouchut [04]...) E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Saint-Venant system Saint-Venant – Exner system Relaxation solver I Example for scalar conservation law I Original SCL ∂t u + ∂x f (u) = 0 I Relaxation model ∂t u + ∂x v 2 ∂t v + c ∂x u I = = 0 1 (f (u) − v ) Stability requirement c ≥ |f 0 (u)| I One retrieves the Rusanov scheme (i.e. HLL scheme with cl = −cr ) E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Saint-Venant system Saint-Venant – Exner system Suliciu relaxation solver : No source I Suliciu relaxation model for SW system ∂t h + ∂x hū = 0 ∂t hū + ∂x hū 2 + π = 0 2 ∂t hπ + ∂x (hπū) + c ∂x ū = I gh2 −π 2 Stability criterion c ≥h I 1 p gh Eigenvalues (distincts and associated to LD fields) c λ± = u ± , h λu = u (Suliciu [90,92]) E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Saint-Venant system Saint-Venant – Exner system Suliciu relaxation solver : No source I Initialization : Relaxation source term with ” = 0” πin = g (hin )2 /2 I Solution of the (homogeneous) Riemann problem R w[W (t, x), l ,Wr ] E. Audusse W= (h, ū, π)T Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Saint-Venant system Saint-Venant – Exner system Suliciu relaxation solver : No source I I Computation of the intermediate states 1 c u ∗ = uM − ∆π, π ∗ = πM − ∆u 2c 2 1 1 1 1 τl∗ = τl + ∆u− 2 ∆π, τr∗ = τr + ∆u+ 2 ∆π, 2c 2c 2c 2c Waves celerities c λl = ul − , λu = u ∗ , hl λ+ = ur + c , hr ”c ≥ h ”τ = p gh” Extension to vacuum : Bouchut, ”Nonlinear Stability of FVM for HCL”, Birkhäuser, 2004 E. Audusse Numerics for SW flows 1 ” h Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Saint-Venant system Saint-Venant – Exner system Suliciu relaxation scheme : With source I First version ∂t hū + ∂x ∂t h + ∂x hū = 0 hū + π + gh∂x z = 0 2 1 ∂t hπ + ∂x (hπū) + c ∂x ū = ∂t z = 0 2 I gh2 −π 2 Eigenvalues (associated to LD fields) c λ± = u ± , h λu = u, λ0 = 0 (Bouchut [04]) E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Saint-Venant system Saint-Venant – Exner system Suliciu relaxation solver : With source I I I Computation of the new solution Non conservative system Integration process (no flux) Properties Consistency, WB, Positivity, Entropy inequality Effective computation Eigenvalues not ordered Multiple Riemann pbs to solve E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Saint-Venant system Saint-Venant – Exner system Suliciu relaxation solver : With source I Alternative version ∂t hū + ∂x ∂t h + ∂x hū = 0 hū + π + gh∂x z̃ = 0 2 2 ∂t hπ + ∂x (hπū) + c ∂x ū = ∂t z̃ + ū∂x z̃ I = 1 gh2 −π 2 1 (z − z̃) Eigenvalues (associated to LD fields) c λ± = u ± , h λu = u (double) Riemann problem is under-determined... E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Saint-Venant system Saint-Venant – Exner system Suliciu relaxation solver : With source I Linearized alternative version ∂t hū + ∂x ∂t h + ∂x hū = 0 hū + π + g h̄∂x z̃ = 0 2 2 ∂t hπ + ∂x (hπū) + c ∂x ū = ∂t z̃ + ū∂x z̃ I = 1 gh2 −π 2 1 (z − z̃) Eigenvalues (associated to LD fields) c λ± = u ± , h E. Audusse λu = u (double) Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Saint-Venant system Saint-Venant – Exner system Suliciu relaxation solver : With source I Solution of the Riemann problem Same structure as in the conservative case... But different intermediate states I Properties : Consistency, WB, Positivity, Entropy inequality h̄ = hM (Introduced as a wb simple Riemann solver : Galice [02]) E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Saint-Venant system Saint-Venant – Exner system Suliciu relaxation solver : Numerical test Comparison between Suliciu without source + Hydrostatic reconstruction and Suliciu with source E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Saint-Venant system Saint-Venant – Exner system Suliciu relaxation solver : Towards morphodynamics . Morphodynamics process Suspended- and bedload E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Saint-Venant system Saint-Venant – Exner system Suliciu relaxation solver : Towards morphodynamics I Saint-Venant – Exner model ∂t qw + ∂x ∂ t h + ∂ x qw = 0, qw2 g + h2 h 2 = −gh∂x b − ρs (1 − p)∂t b + ∂x qs I τb , ρw = 0, Properties I I I I Hyperbolic for classical choices of qs (h, ū, ∂x b) Eigenvalues hard to compute except for special choices of qs No dynamics in the solid phase No transport in the fluid phase (Hudson [05], Castro [08], Benkhaldoun [09], Cordier [11]...) E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Saint-Venant system Saint-Venant – Exner system Suliciu relaxation solver : Towards morphodynamics I Sediment flux formula (Grass [81]) qs = Ag |ū|2 ū I Shields parameter θ= I |τb |/ρw , g (s − 1)dm s = ρs /ρw Threshold sediment flux formulae q 3 qs = Φ g (s − 1)dm I I I 3/2 Meyer-Peter & Müller [48] : Φ = 8 (θ − θc )+ 1/2 Engelund & Fredsoe [76]: Φ = 18.74(θ − θc )+ (θ1/2 − 0.7θc ) 1/2 Nielsen [92] : Φ = 12 θ (θ − θc )+ ... E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Saint-Venant system Saint-Venant – Exner system Numerical strategies for bedload transport I Steady state strategy I I I I External coupling (time splitting) I I I I I Hydrodynamic computation on fixed topography Steady state Evolution of topography forced by hydrodynamic steady state Efficient for phenomena involving very different time scales Use of two different softwares for hydro- and morphodynamics Allow to use existing solvers and different numerical strategies Actual strategy at EDF (MASCARET-COURLIS) Efficient for low coupling Internal coupling I I I Solution of the whole system at once Need for a new solver Efficient for general coupling E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Saint-Venant system Saint-Venant – Exner system Dam break : Failure for external coupling External coupling (M. Jodeau) E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Saint-Venant system Saint-Venant – Exner system Suliciu relaxation solver : Towards morphodynamics I Relaxation model ∂t (hū) + ∂x ∂t h + ∂x hū = 0 hū + π + gh∂x b = 0 2 1 gh2 α2 ∂x u = −π ∂t π + ū∂x π + h 2 ∂t b + ∂x ω = 0 2 β 1 ∂t ω + − ū 2 ∂x b + 2ū∂x ω = (qs − ω) 2 h I Definitions I I I (π, ω) : Auxiliary variables (fluid pressure, sediment flux) > 0 : (Small) relaxation parameter (α, β) > 0 : Have to be fixed to ensure stability E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Saint-Venant system Saint-Venant – Exner system Suliciu relaxation solver : Towards morphodynamics I General properties I I I Formally tends to SW-Exner model when tends to 0 Always hyperbolic (h 6= 0) and LD fields Stability requirement a2 ≥ h2 p 0 (h) = gh3 , I b 2 ≥ (hu)2 + gh2 ∂u Qs Specificities for morphodynamics I I No explicit dependency on sediment flux qS Ordered eigenvalues u− I b a a b <u− <u<u+ <u+ H H H H Riemann problem easy to solve for a < b... But case b < a leads to unafordable computations... With linearized version : Riemann pb may have no solution ! E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Saint-Venant system Saint-Venant – Exner system Dam break : Internal coupling zb+Hf [m] Free surface at t=1 s - J=4000 2 1.5 1 0.5 0 zb+Hf at t=1 s 0 2 4 6 8 10 x [m] zb [m] Bottom topography at t=1 s - J=4000 0.15 0.1 0.05 0 -0.05 -0.1 zb+Hf at t=1 s 0 2 4 6 8 x [m] Internal coupling (O. Delestre) E. Audusse Numerics for SW flows 10 Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Saint-Venant system Saint-Venant – Exner system ”Steady” flow over a movable bump Dunes Antidunes Fluvial flow Torrential flow E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Saint-Venant system Saint-Venant – Exner system ”Steady” flow over a movable bump in 2d E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Derivation Numerics : Kinetic scheme Fluid models for geophysic flows I Incompressible Navier Stokes equations I I I I I Efficient model for a large class of flows CPU time (3d computations) Complex implementation (moving boundaries, not connected domains...) Robustness of the softwares for stiff flows (dam break, hydraulic jumps...) Shallow water equations I I I I I I Easy implementation (fixed domain) CPU time (2d computations) Robustness of the software Agreement with experiments... but not for all flows ! Constant velocity along the z-direction Hydrostatic approximation E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Derivation Numerics : Kinetic scheme Fluid models for geophysic flows I Incompressible Navier Stokes equations I I I I I Efficient model for a large class of flows CPU time (3d computations) Complex implementation (moving boundaries, not connected domains...) Robustness of the softwares for stiff flows (dam break, hydraulic jumps...) Shallow water equations I I I I I I Easy implementation (fixed domain) CPU time (2d computations) Robustness of the software Agreement with experiments... but not for all flows ! Constant velocity along the z-direction Hydrostatic approximation E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Derivation Numerics : Kinetic scheme From hydrostatic NS equations to multilayer models I General Idea I I Derivation I I I To derive a 2d (of hyperbolic type) model that takes into account vertical effects in the flow Vertical discretization of the fluid into M layers Vertical integration of hydrostatic incomp. NS equ. by layer Consequences I I Each layer has its own velocity Coupling between the layers through I I I Pressure term (global coupling) Mass exchange (”local” coupling : interface condition for mass equation) Viscous effect (local coupling : interface condition for momentum equation) E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Derivation Numerics : Kinetic scheme Multilayer model : Simplified case I Hydrostatic incompressible Euler equ. with free surface ∂x u + ∂z w = 0, 2 ∂t u + ∂x u + ∂z uw + ∂x p = 0, ∂z p = −g , with x ∈ R, t > 0, I zb (x) ≤ z ≤ η(t, x), Boundary conditions ∂t η + uη ∂x η − wη = 0 E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Derivation Numerics : Kinetic scheme Multilayer model : Vertical discretization I Velocity u(t, x, z) = M X 1[zα−1/2 ,zα+1/2 ] ūα (t, x) α=1 E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Derivation Numerics : Kinetic scheme Multilayer model : Vertical integration I Equations after integration on a layer ∂t hα + ∂x hα ūα = Gα+1/2 − Gα−1/2 , ∂t hα ūα + ∂x hα u¯2 + ghα ∂x H α = −ghα ∂x b + uα+1/2 Gα+1/2 − uα−1/2 Gα−1/2 I Mass exchange term Gα+1/2 = ∂t zα+1/2 + uα+1/2 ∂x zα+1/2 − wα+1/2 I Natural conditions for lowest and uppest layers G1/2 = GN+1/2 = 0 I What choice for the others ? E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Derivation Numerics : Kinetic scheme Multilayer model : Variable density I Equations after integration on a layer ∂t ρα hα + ∂x ρα hα ūα = Gα+1/2 − Gα−1/2 , ∂t ρα hα ūα + ∂xρα hα u¯2 + ∂x hα pα α = pα+1/2 ∂x zα+1/2 − pα−1/2 ∂x zα−1/2 +uα+1/2 Gα+1/2 − uα−1/2 Gα−1/2 I Mass exchange term Gα+1/2 = ρα+1/2 ∂t zα+1/2 + uα+1/2 ∂x zα+1/2 − wα+1/2 I Pressure terms Z zα+1/2 1 pα = p(x, z, t)dz, hα zα−1/2 E. Audusse pα+1/2 = p(x, zα+1/2 , t), Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Derivation Numerics : Kinetic scheme Multilayer model : Different models I No exchange : Multifluid problems Gα+1/2 = 0 M superposed Saint-Venant systems (Castro et al. [01]...) I Horizontal layers ∂t zα+1/2 = ∂x zα+1/2 = 0 ⇒ Gα+1/2 = −wα+1/2 1 equ. for hM and M velocity equations (Rambaud [12]) I Adaptative layers hα (t, x) = λα H(t, x) 1 equ. for H and M velocity equations (ABPSa [11]) E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Derivation Numerics : Kinetic scheme Multilayer model : Links with classical NS discretization I Isopycnal coordinates Stratifications are imposed in the model I z− coordinates Pbs to deal with complex bottom and water surface I σ− coordinates Well-adapted to geometry but may diffuse stratifications E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Derivation Numerics : Kinetic scheme Multilayer model : System of equations ∂t N X N X ρα lα H + ∂x α=1 ρα lα Huα = 0 α=1 ∂t (ρα hα uα ) + ∂x ρα hα uα2 + hα pα = uα+1/2 Gα+1/2 − uα−1/2 Gα−1/2 +pα+1/2 ∂x zα+1/2 − pα−1/2 ∂x zα−1/2 ∂t (ρα hα Tα ) + ∂x (ρα hα Tα uα ) = Tα+1/2 Gα+1/2 − Tα−1/2 Gα−1/2 ρα = ρ(Tα ) Z zα+1/2 1 pα = p(x, z, t)dz, hα zα−1/2 Gα+1/2 = α X ∂ρj hj j=1 ∂t + pα+1/2 = p(x, zα+1/2 , t) α X ∂ρj hj uj j=1 E. Audusse ∂x Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Derivation Numerics : Kinetic scheme Multilayer model : Properties I Invariant domain Positivity of total water depth I Global energy inequality N Esv ,α = ∂ ∂t I N X ! N Esv ,α α=1 2 2 g ρα (zα+1/2 − zα−1/2 ) ρα hα uα2 + 2 2 ∂ + ∂x N X α=1 uα g N Esv + ρ h H α α ,α 2 ! =0 Hyperbolicity I I Bi-layer model is hyperbolic Possible local loss of hyperbolicity for more than three layers E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Derivation Numerics : Kinetic scheme Numerics : Kinetic interpretation of SW system I Saint-Venant system ∂t hu + ∂x I Density function M(t, x, ξ) = I ∂t h + ∂x hu = 0, hu 2 + gh2 /2 = −gh ∂x b h(t, x) χ c(t, x) ξ − u(t, x) c(t, x) r , c= gh 2 with χ an even probability function, ξ a kinetic velocity Kinetic equation ∂t M + ξ∂x M − g ∂x z∂ξ M = Q(x, t, ξ) Equivalency with SW system : Integration in ξ vs. (1, ξ)T E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Derivation Numerics : Kinetic scheme Numerics : Kinetic scheme (derivation, no source) I Kinetic level I I fi I I n+1 Definition of Min from (hin , uin ) Upwind scheme for the linear transport kinetic equation = ∆t Min − ∆x n fi+1/2 − n fi−1/2 Macroscopic scheme Integration in ξ Z n (F h )ni+1/2 = fi+1/2 dξ, , n fi+1/2 = (F q )ni+1/2 = Z ξMin if ξ > 0 n ξMi+1 if ξ < 0 n ξfi+1/2 dξ Source term Perthame-Simeoni [Calcolo, 01] : Numerical integration processes E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Derivation Numerics : Kinetic scheme Numerics : Kinetic scheme (properties, no source) I Simplicity Macroscopic fluxes can be computed analytically if probability function χ is simple enough 1 χ(ω) = √ I[−√3,√3] , 2 3 I 1/2 ω2 χ(ω) = 1 − 4 + No need for the computation of the eigenvalues Stability I I I Positivity for water depth Entropy inequality CFL condition n ∆t ≤ mini E. Audusse ∆xi p n ωm |uin | + √ ghi 2 Numerics for SW flows ! Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Derivation Numerics : Kinetic scheme Numerics : Multilayer system I Extension of the kinetic interpretation Construction of a kinetic scheme I Modified CFL condition Takes into account mass exchange terms Positivity of water depth and tracer concentration I Extension of the hydrostatic reconstruction Preservation of relevant equilibria Variable density case I I I Computation of solution : Non linear problem to solve Boussinesq assumption : Back to simple case E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Derivation Numerics : Kinetic scheme Numerics : 3d dam break E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Derivation Numerics : Kinetic scheme Numerics : Wind-induced circulation E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Derivation Numerics : Kinetic scheme Numerics : Stratified fluid ? E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Derivation Numerics : Kinetic scheme Numerics : Lock exchange E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Derivation Numerics : Kinetic scheme Numerics : Gibraltar straight E. Audusse Numerics for SW flows Towards morphodynamics : Suliciu relaxation Towards 3d : Multilayer model Derivation Numerics : Kinetic scheme Numerics : Ocean in bottles . Authors : A. Rousseau, M. Nodet, S. Minjeaud, P.O. Gaumin (INRIA, MOISE team) mpe2013.org/fr http://imaginary.org/exhibition/mathematics-of-planet-earth ”Un jour, une brève” mpt.2013.fr E. Audusse Numerics for SW flows