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Finite-Volumes II: Non Cartesian Sauro Succi
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Finite Volumes Real-life geometries: coordinate-free Courtesy of Prof. M. Porfiri, NYU Poly
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Structured Non-Cartesian Geometrical data
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Co/Contravariant/Cartesian
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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
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Non-structured: diffusive flux Non-orthogonality: S W N Ε NΕ SΕ NW SW ne se C ew n s
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CEV = Centers/Edges/Vertices Staggered S W N Ε NΕ SΕ NW SW ne se C ew n s Non-orthogonal
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Navier-Stokes (Compressible) Staggered FV
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NW NΕ SΕ SW n e w s P E N W S Vertex-centered staggered
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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
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Discretized Gauss: Continuity Discretized midpoint (2 nd order 8 neigh) Discretized Simpson (4 th order, 8 neigh)
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Discretized Convective Fluxes
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Discretized Gauss: Momentum_x Convective and Dissipative Fluxes
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Non-Linear (outer) iteration Nonlinear (outer) iteration, k=0,1…
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Real-life geometries Courtesy of Prof. M. Porfiri, NYU Poly
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Example: Global: Cylindrical, Spherical, Local: Oblique
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Unstructured FV~FEM
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Reconstruction: Cell Centered
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Mean square residual Minimize error functional:
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Mean square residual
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Exercise: Construct gradient on Regular cells Trapezoidal cells
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Vertex control elements
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Gradient computation: Gauss-Green
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P E
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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…)
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