An ODE-based Wall Model for Turbulent Flow Simulations
Speaker: Michael J. Aftosmis, NAS Computational Aerosciences Branch, NASA Ames Research Center
Presentation
Abstract
We present a new wall model to compute turbulent boundary layers using the RANS equations in high Reynolds number flows. The model solves a two-point boundary value problem for a coupled set of equations for the streamwise velocity and the turbulent viscosity. Since it includes both the pressure gradient and the momentum balance of the full Navier-Stokes system, the ODE is valid farther from the wall. We implement the model within a Cartesian cut cell method, and use one-dimensional linelets in each cut cell to avoid the excessive mesh refinement that would otherwise be needed. The linelets are coupled to the outer Cartesian grid in a fully conservative manner, with two-way interaction between the linelets and the background grid. Detailed comparisons of velocity and eddy viscosity with three well-studied examples from the Turbulence Modeling Resource website are presented to demonstrate the model’s performance in two space dimensions, including an example with smooth-body separation. The results show the new model gives excellent results even when the y+ value of the first point is in the wake layer.
Biography
Michael J. Aftosmis is an Aerospace Engineer in the Computational Aerosciences Branch of the NASA Advanced Supercomputing Division at Ames Research Center, Moffett Field, California. He currently leads the atmospheric propagation and impact effects component of NASA’s Asteroid Threat Assessment Project. Michael has 25 years of experience in the development and application of numerical methods for unstructured and Cartesian grids, computational geometry, mesh generation, adaptation and adjoint methods for error-estimation and shape design. He leads NASA’s Cart3D software development team which supports a community of over 500 users across all NASA mission directorates, the DoD, DOE, academia and industry. His work on the Debris Transport Team for Shuttle Return to Flight was recognized with a NASA Silver Snoopy in 2006 and his contributions have been recognized through numerous NASA Achievement Awards, Research awards of the AIAA, and NASA’s Software of the Year in 2002. Michael has served as an invited lecturer at the von Karman Institute in Belgium, a visiting scientist at the DLR Design Institute for Aerodynamics and his background includes 10 years in the Air Force Research Laboratory. He has served as research advisor/external examiner for Ph.D candidates at MIT, Stanford University, University of Michigan, Georgia Tech and the University of Toronto. Michael holds a S.M. in Aerospace Engineering from MIT, a B.S. from Syracuse University and is an Associate Fellow of the AIAA.