PHX ModelCenter Adds Efficiency and Extensibility to CFD Analysis in Design Process
Challenge: Aircraft Aerodynamic Trade Studies using High-Fidelity CFD Analyses
Most Computational Fluid Dynamics (CFD) analyses are done manually, which means starting with CAD geometry, parameterizing and de-featuring it (if necessary), meshing it, and running it in a CFD solver. This process is labor intensive, time consuming and error prone. Once the solution is finished, post-processing normally takes place with additional calculations to glean overall performance metrics from the detailed results. CFD analyses are not normally well integrated into practical design processes, since they require a far more efficient process. As an example, the aerodynamic analysis of a Predator UAV would need CFD to study the effect of wing twist on lift and drag coefficients for specific geometries. In such a scenario, NASA’s Vehicle Sketch Pad (VSP) could be used for CAD modeling, ANSYS ICEM CFD as the meshing tool, and ANSYS FLUENT as the CFD solver.
Solution: PHX ModelCenter’s Capabilities to Integrate and Automate the Design Process
For this example, ModelCenter’s QuickWrap tool and a plug-in were used to integrate CAD modeling, meshing generator and the CFD solver into an interactive, automated design environment. A plug-in for VSP allowed users to pick parametric geometry variables from a list to incorporate them into the model. Geometry could be modified and VSP could be run entirely from within ModelCenter. The QuickWrap tool was used to tell ModelCenter the location of an input geometry file from VSP, name the output mesh file from ICEM CFD, and how to run the mesh on the command prompt. "QuickWrapping" FLUENT allowed choosing two outputs—drag and lift coefficients—from a single mesh input, and provide them from FLUENT as a text file. FLUENT was run in a batch through a journal file by simply typing the instruction into QuickWrap. This process in ModelCenter included, as a final step, a script that allowed users to input additional post-processing calculations in any of various languages, such as VBScript, Python, etc. The geometry of the aircraft was rendered in ModelCenter to provide a visual check of modeling updates as geometric parameters were changed. A plot of the residuals from the CFD solver were captured and also updated automatically as the process was executed. Once this process in ModelCenter was set up, trade studies were invoked to exercise the model.
Benefit: A Trade Study Engine with Superior Visualization and Response Surface Capability
Once set up, trade studies in ModelCenter require very little time to create. For long running codes, ModelCenter provides a response surface tool that allows analysts to use a surrogate model instead of the actual CFD solver, enabling further trade studies or optimization to be performed quickly.