Better, Faster Prep and Meshing with ANSYS CFD

Fidelity and accuracy are critical in CFD simulation. 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 required hours of manual effort to “clean up” the model and then prepare the mesh. Users were tempted to 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. As a result, pre-processing time for complex geometries has been reduced by 60 to 80 percent. If you haven’t tried ANSYS CFD lately, you have not tried ANSYS CFD.

Most Accurate Results and Fast Prep and Meshing - White Paper

Capturing the fine details in free surface flows and combustion simulations requires an extremely fine polyhedral mesh. In the past, this mesh could not be automatically adapted, resulting in extremely long solve times. Now, patented, polyhedral unstructured mesh adaptation (PUMA) in ANSYS Fluent automatically refines the polyhedral mesh to resolve fine details, while leaving coarser mesh in place. As a result, engineers can get the accuracy they need — without the wait.

PUMA speeds high quality free surface flows
PUMA technology automatically refines polyhedral mesh to capture splash details, while leaving courser mesh in place for faster solve times.

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 glossed over. 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 is fast and interactive, and it provides the perfect environment for rapid correction of complex geometries.

Spaceclaim for CFD
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Finalize the Model While Preserving Key Features

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 Meshing helped them to quickly identify and protect key elements of the model where geometrical accuracy could not be compromised.

ANSYS Meshing preserves subtle details of this automotive hood geometry to ensure accuracy of the aeroacoustic simulation.

ANSYS Meshing preserves subtle details of this automotive hood geometry to ensure accuracy of the aeroacoustic simulation. Courtesy of Volvo.

The Fluent Meshing integrated CAD module maintains the original CAD hierarchy to easily navigate, display and manage model data. The resulting model

  • Has faster loading and response times
  • Represents each part at high or low resolution to get the right geometry or mesh – no more huge, worst-case scenario files
  • Maintains link back to the original CAD engineering model for easy updates and design changes

Integrated CAD module

Integrated CAD module can reduce hands-on time for complex models by 1/3 or more.

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, minimizing stair stepping, and employing anisotropic mesh adaption in the boundary layer (rather than the more costly isotropic adaption) within the solution step, to home in on efficient and accurate boundary layer resolution. The result is the right number of cells of the right size and 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.

With today’s ANSYS CFD, it’s possible to have it all – unsurpassed gold standard accuracy with drastically reduced manual effort. Hands-on time has been reduced by up to 80 percent when using these tools along with scripted pre-processing.