Depend on the specific purpose and flow conditions of the problem different CFD

# Depend on the specific purpose and flow conditions of

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Depend on the specific purpose and flow conditions of the problem, different CFD codes can be chosen for different applications (aerospace, marines, combustion, multi-phase flows, etc.) Once purposes and CFD codes chosen, “ CFD process ” is the steps to set up the IBVP problem and run the code: 1. Geometry 2. Physics (Setup) 3. Mesh 4. Solve 5. Results
CFD Process Viscous Model (ANSYS Fluent- Setup) Boundary Conditions (ANSYS Fluent- Setup) Initial Conditions (ANSYS Fluent- Solution) Convergent Limit (ANSYS Fluent- Solution) Contours, Vectors, and Streamlines (ANSYS Fluent- Results) Precisions (ANSYS Fluent- Solution) Numerical Scheme (ANSYS Fluent- Solution) Verification & Validation (ANSYS Fluent- Results) Geometry Geometry Parameters (ANSYS Design Modeler) Physics Mesh Solution Flow properties (ANSYS Fluent- Setup) Unstructured (ANSYS Mesh) Steady/ Unsteady (ANSYS Fluent- Setup) Forces Report (ANSYS Fluent- Results) XY Plot (ANSYS Fluent- Results) Domain Shape and Size (ANSYS Design Modeler) Structured (ANSYS Mesh) Iterations/ Steps (ANSYS Fluent- Solution) Results Green regions indicate ANSYS modules 37
38 Geometry Selection of an appropriate coordinate Determine the domain size and shape Any simplifications needed? What kinds of shapes needed to be used to best resolve the geometry? (lines, circular, ovals, etc.) For commercial code, geometry is usually created using commercial software (either separated from the commercial code itself, like Gambit) For research code, commercial software (e.g. Gridgen) is used.
39 Physics (Setup) Flow conditions and fluid properties 1. Flow conditions : inviscid, viscous, laminar, or turbulent, etc. 2. Fluid properties : density, viscosity, and thermal conductivity, etc. 3. Flow conditions and properties usually presented in dimensional form in industrial commercial CFD software, whereas in non-dimensional variables for research codes. Selection of models: different models usually fixed by codes, options for user to choose Initial and Boundary Conditions: not fixed by codes, user needs specify them for
40 Mesh Meshes should be well designed to resolve important flow features which are dependent upon flow condition parameters (e.g., Re), such as the grid refinement inside the wall boundary layer Mesh can be generated by either commercial codes (Gridgen, Gambit, etc.) or research code (using algebraic vs. PDE based, conformal mapping, etc.) The mesh, together with the boundary conditions need to be exported from commercial software in a certain format that can be recognized by the research CFD code or other commercial CFD software.
41 Solve Setup appropriate numerical parameters Choose appropriate Solvers Solution procedure (e.g. incompressible flows) Solve the momentum, pressure Poisson equations and get flow field quantities, such as velocity, turbulence intensity, pressure and integral quantities (lift, drag forces)
42 Results Reports the saved time history of the residuals of the velocity, pressure and temperature, etc.

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• Fall '12
• Yang
• Fluid Dynamics, CFD Labs, CFD codes, ANSYS Mesh