• 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.
You've reached the end of your free preview.
Want to read all 57 pages?
- Fall '12
- Fluid Dynamics, CFD Labs, CFD codes, ANSYS Mesh