Fidelity and accuracy is critical in CFD simulation. After all, physical prototyping and testing can only be reduced and even replaced by CFD if one can expect accurate results. Up to now, high fidelity, high accuracy results came with a price. Complex geometries — the realistic, no holds barred type — required hours of manual effort to clean up the model and then prepare the mesh. Users were tempted to cut corners and take short cuts that sped up prep but took a toll on accuracy and fidelity. Unfortunately, there is no way of knowing just how those inaccuracies skewed the results, putting any recommendations in doubt. For example, if you don’t resolve a boundary layer correctly then any aerodynamic drag figures could be highly inaccurate.
At ANSYS, we won’t compromise on results and we don’t want you to either. That’s why we have been putting special focus on model preparation and meshing over the last few releases. I’m really excited with what we have accomplished: Pre-processing time for complex geometries has already been reduced by up to 40 percent in ANSYS 16.0. Now ANSYS 17.0 delivers further reductions of between 40 and 80 percent. If you haven’t tried ANSYS CFD lately, I urge you to try it now. Contact us for your free trial!
Direct Modeling Speeds Prep
To calculate the right solution it is important to model the right geometry. Complex models provided for simulation are often prepared by multiple designers, sometimes working on different systems. As a result, when models are brought together for simulation they are rarely complete. For this stage, ANSYS SpaceClaim is the ideal partner to inspect and rectify major faults in the geometry that simply cannot be ignored. Unlike typical bottoms up CAD systems, ANSYS SpaceClaim is a direct modeler and can be used to move whole components, close off regions or shrink large gaps. ANSYS SpaceClaim DirectModeler is fast and interactive and provides the perfect environment for rapid correction of complex geometries. Check out this video to learn more.
Finalize the Model While Preserving Key Features
Your model may still have features such as rivet holes that are unnecessary for simulation but complicate meshing. ANSYS Fluent meshing can tidy up these and any other loose ends using quick and easy sewing or hole capping tools.
Certain features are critical to the simulation and yet are subtle enough to be easily lost by conventional tools. For example, Volvo needed to capture all the details of sculpting on an automobile hood designed to set air flow around the “A” pillar in a way that minimized wind noise. Feature extraction in ANSYS Fluent meshing helped them to quickly identify and protect key elements of the model where geometrical accuracy could not be compromised.
Mesh for Accuracy and Speed
New meshing algorithms and parallelization mean that a mesh can be generated quickly and efficiently. Employing body-fitted meshing techniques can enhance solution accuracy and avoids literally “cutting corners,” which can occur with other approaches. Optimizing the mesh in the boundary layer region can be achieved by ensuring maximum availability of high aspect ratio elements and minimizing stair stepping. Further mesh improvement can be obtained by employing anisotropic mesh adaption in the boundary layer (rather than more costly isotropic adaption) within the solution step, to bring about efficient and accurate boundary layer resolution. The result is the right number of cells of the right size in the right position for optimal accuracy and speed.
Finally, the use of scripts can automate the majority of steps in the meshing process, producing high quality meshes, with appropriate sizing, even for complex models. This is especially useful for multiple runs of similar models for optimization.
Faster, Better CFD
Now with ANSYS 17.0, it’s possible to have it all – unsurpassed “gold standard” accuracy with drastically reduced manual effort. We have seen reductions in hands-on time of up to 80 percent when using these tools along with scripted pre-processing. All this is before we have started solving. ANSYS Fluent can power through the simulation using record-breaking high performance computing parallelization to minimize your turnaround time for each and every simulation — but that is the subject of another blog!
To learn more about how ANSYS 17.0 speeds model prep and meshing, download the application brief. For more depth, watch the webinar titled, “Get better, Faster CFD results with ANSYS Fluent.”