Finite-Volumes II: Non Cartesian Sauro Succi
Finite Volumes Real-life geometries: coordinate-free Courtesy of Prof. M. Porfiri, NYU Poly
Structured Non-Cartesian Geometrical data
Co/Contravariant/Cartesian
CEV = Centers/Edges/Vertices Non-cartesian: structured S W N Ε NΕ SΕ NW SW ne se C ew n s Non-orthogonal Still structured
Non-structured: diffusive flux Non-orthogonality: S W N Ε NΕ SΕ NW SW ne se C ew n s
CEV = Centers/Edges/Vertices Staggered S W N Ε NΕ SΕ NW SW ne se C ew n s Non-orthogonal
Navier-Stokes (Compressible) Staggered FV
NW NΕ SΕ SW n e w s P E N W S Vertex-centered staggered
Discretized Gauss: Continuity Discretized Convective Fluxes Same for north,west, south … Non-orthogonality issues (!) S W N Ε NΕ SΕ NW SW ne se C ew n s
Discretized Gauss: Continuity Discretized midpoint (2 nd order 8 neigh) Discretized Simpson (4 th order, 8 neigh)
Discretized Convective Fluxes
Discretized Gauss: Momentum_x Convective and Dissipative Fluxes
Non-Linear (outer) iteration Nonlinear (outer) iteration, k=0,1…
Real-life geometries Courtesy of Prof. M. Porfiri, NYU Poly
Example: Global: Cylindrical, Spherical, Local: Oblique
Unstructured FV~FEM
Reconstruction: Cell Centered
Mean square residual Minimize error functional:
Mean square residual
Exercise: Construct gradient on Regular cells Trapezoidal cells
Vertex control elements
Gradient computation: Gauss-Green
P E
Finite Volumes: summary Intuitive and physically sound Round-off Conservative (fluxin=-fluxout) Geo-topological ahead, laborious Interpolation to be decided (unlike FEM) Structured: Finite-Difference with non-smooth coordinates Unstructured: Close to FEM No-singularity (1/r for sherical coordinates) Commercially dominant (STAR-CD, FLUENT…)