Moving targets

released 08.25.09

A research team is using NCSA resources to develop new methods of studying fluid‑structure interaction and modeling of turbulence on moving grids.

Coupled analysis of fluid-structure interaction (FSI) problems combines fluids, solids, and their interactions in a single-pass simulation with the intent of capturing the true multiphysics behavior of the system. Current computational methods work reasonably well in predicting coupled effects in mildly nonlinear nonlinear FSI problems. However, says Arif Masud, "mathematically non-smooth FSI problems pose great challenge." For general systems where a time accurate simulation is the only authentic approach, high-fidelity computer programs and computer algorithms will be required to take full advantage of the opportunities offered by the developments in hardware, such as the Blue Waters sustained petascale machine to come online in 2011.

Professor Masud and his team in the civil and environmental engineering department at the University of Illinois at Urbana-Champaign are developing mathematically robust and computationally economic FSI techniques with the assistance of NCSA, so researchers can economically obtain accurate solutions. One of their projects tested algorithms modeling aircraft pressure, velocity, and vorticity around YF-17 aircraft. This lightweight fighter jet prototype is the basis for the U.S. Navy's F-18 Hornet and Super Hornet. Using NCSA's Cobalt, the team conducted numerous simulations.

Since these computations involved large and dense meshes—the mesh is composed of 1 million tetrahedral elements with about 5 million degrees of freedom—Masud turned to NCSA's Advanced Applications Support visualization group to visualize the results. The visualization was especially helpful in method development as it allowed researchers to see the effects of various terms that otherwise could only be indirectly estimated.

"This was an interesting project which required the use of a variety of visualization tools," says visualization programmer Mark Van Moer. "The polygonal aircraft body was extracted from the original mesh using a combination of custom VTK scripts and Blender. The final renderings were done with Kitware's ParaView, a parallel renderer, which is built with Kitware's VTK C++ class library. The data also allowed for a wide variety of vector and scalar visualization techniques."

Masud says the team successfully developed multiscale finite element methods for incompressible Navier-Stokes equations and extended the capability to formulations written in arbitrary Lagrangian-Eulerian frameworks for problems involving moving and deforming spatial domains. The technology was integrated with 2D and 3D adaptive mesh rezoning schemes previously developed. And they have recently extended variational multiscale/stabilized formulation for incompressible Navier-Stokes equations to variational multiscale residual-based turbulence models for large eddy simulation.

This research was funded through the NCSA Faculty Fellows program, which enables campus researchers to collaborate with NCSA.

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