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ANSLab Projects

  • GRUMMP --- Generation and Refinement of Unstructured, Mixed-Element Meshes in Parallel

    Before an analyst can begin a numerical simulation, he/she must first generate a mesh of the problem domain. This sounds simple enough, but in practice is currently often the bottleneck in the simulation cycle in terms of human time and effort. This problem is only getting more severe as simulations of more complex problem domains becomes commonplace. To handle complex geometries and support solution-based adaptation, unstructured meshes are becoming more prevalent as time goes on. We have developed an unstructured mesh generation package called GRUMMP. This software, which is still actively under development, is primarily a testbed for developing new algorithms to generate high-quality triangular and tetrahedral meshes. In addition, GRUMMP is freely available for non-commercial usage and is in use worldwide --- it has been downloaded over 7000 times in over 60 countries.

  • High-Order Accurate Simulation of Aerodynamic Flows Using Unstructured Meshes

    The history of scientific computing in general and of computational fluid dynamics in particular is the story of a relentless pursuit of highly-accurate solutions to increasingly complex problems with efficient use of computing resources. This desire for highly-accurate solutions is the main general motivation for the development of high-order accurate methods (by which we mean specifically in this paper third- and fourth-order accurate methods). A more specific motivation that has increasing urgency in recent years is that practical application of large-eddy simulations for turbulent flows requires the use of high-order methods to minimize the effect of numerical error on the sub-grid scale model. We are one of only a handful of research groups worldwide working on developing high-order accurate finite-volume methods for unstructured meshes. We have had considerable success in applying these methods to problems in transonic aerodynamics.

  • Impact of Mesh Quality on Solution Quality

    The design of aircraft, from commercial and military transport aircraft to combat aircraft and unmanned aerial vehicles, depends increasingly on the use of computational fluid dynamics (CFD). Accurate and reliable CFD simulation require the ability to reduce and quantify both physical modeling errors (including turbulence modeling and real gas effects) and numerical errors. Presently, physical modeling errors and numerical errors are comparable in magnitude for computations of the flow around transport aircraft, as illustrated by the results of the AIAA's series about Drag Prediction Workshops (DPW). While user expertise is certainly an important factor, the DPW participants are world leading experts in configuration aerodynamics simulations, so user expertise alone will not resolve this problem. Two factors are at work here. First, initial mesh generation does not account for the type and location of flow features; this is the province of adaptive mesh refinement. Second, local mesh features --- including cell size, anisotropy, shape, and connectivity --- can have adverse interactions with a discretization scheme. The problem of adaptive mesh refinement is well studied and reasonably well understood. The interactions between mesh quality and discretization schemes, on the other hand, is not. This problem is particularly severe for unstructured meshes, because the local shape and connectivity of the mesh are more varied and difficult to quantify than for structured meshes. We have recently begun working to analyze the local truncation error in unstructured mesh finite-volume schemes and relate that error to solution quality, with the goal of improving mesh generation techniques to generate meshes that lead to better solutions.



News

  • ANSLab is pleased to welcome Dr. Daniel W. Zaide as a Post-Doctoral Researcher.
  • ANSLab is also pleased to welcome David and Liang as new masters students.
  • Congrats to Alireza and Mahkame for completing their Masters.

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