1. © Ram Ramanan 2/22/2016 Commercial Codes 1 ME 7337 Notes-2001-001 Computational Fluid Dynamics for Engineers Lecture 4: Commercial Codes

2. © Ram Ramanan 2/22/2016 Commercial Codes 2 ME 7337 Notes-2001-001 Why commercial CFD codes  > 100 man-years of CFD development  Integrated grid generation, solver and post-processing  Standardized tools (tested and validated) for companies  Ability to handle complex geometries  Easy to use user interfaces  Good technical support  Ability to import information from other CAD tools and interface with other analysis tools  Faster virtual prototyping leading to quicker design times  Designed to cost, performance and quality  Extremely flexible user subroutines that allow creative problem solving

3. © Ram Ramanan 2/22/2016 Commercial Codes 3 ME 7337 Notes-2001-001 Physics modeled  Incompressible or compressible flows  Internal or external flows  Laminar or turbulent flows  Moving boundary flows  Newtonian, non-Newtonian with variable properties  Combustion, chemical kinetics, plasma chemistry  Multiphase flows

4. © Ram Ramanan 2/22/2016 Commercial Codes 4 ME 7337 Notes-2001-001 Limitations  Learning curve related to user interfaces  Makes users regard it as a black box  Solutions look realistic enough to be believable  Move toward reducing the number of solution variables or algorithms removed from the user  Defaults for algorithm, convergence etc.  Codes – too robust or too stable ? (always guaranteed a solution – even with incorrect boundary conditions or problem set-up)

5. © Ram Ramanan 2/22/2016 Commercial Codes 5 ME 7337 Notes-2001-001 Suggestions  Always know what to expect from the solution  Compare with analytical solutions for ‘simplified’ scenarios  Need for good experimental data and validation  Always question the results  Use the most accurate (even if time consuming) algorithms  Work with tighter tolerances, finer mesh  Verify if solutions are mesh-converged  Review cell reynolds number, mesh skewness (compute CFL limit)  Do not believe the absolute numbers !  Let simulations suggest trends and simplifications for analytical solutions