Open Rotor Computational Aeroacoustic Analysis with an Immersed Boundary Method
Speaker: Michael Barad, NAS Computational Aerosciences Branch, NASA Ames Research Center
Presentation
Abstract
Reliable noise prediction capabilities are essential to enable novel fuel efficient open rotor designs that can meet the community and cabin noise standards. Toward this end, Navier-Stokes based immersed boundary methods (IBM) have reached a level of maturity where more and more complex flow problems can be tackled with this approach. The Launch Ascent and Vehicle Aerodynamics (LAVA) structured Cartesian higher-order IBM methodologies for this moving boundary problem are discussed. This work demonstrates that LAVA's Navier-Stokes based IBM provides the ability for aeroacoustic analysis of wake-dominated flow fields generated by a contra-rotating open rotor. These are first-of-a-kind aeroacoustic simulations of an open rotor propulsion system employing an IBM. Two free-stream Mach numbers with M=0.2 and M=0.78 are considered in this analysis that are based on the nominally take-off and cruise flow conditions. An installed configuration with pylon is also presented. The simulation data is compared to available experimental data and other computational results employing more conventional CFD methods. Spectral analysis is used to determine the dominant wave propagation pattern in the acoustic near-field.
Biography
Michael Barad is a research scientist in the Computational Aerosciences Branch at NASA Ames Research Center. Barad received his B.S. from the University of Colorado Boulder in 1993, and his M.S. at the University of California, Berkeley in 1997, focusing on computational environmental fluid mechanics. He received his Ph.D. at the University of California, Davis in 2006, where his dissertation was "An Adaptive Cartesian Grid Projection Method for Environmental Flows". During his Ph.D. he was a DOE Computational Science Graduate Fellow, and through this he conducted his research within the Applied Numerical Algorithms Group at Lawrence Berkeley National Laboratory. From 2006-2009 he was at Stanford's Environmental Fluid Mechanics Laboratory as a NSF Mathematical Sciences Postdoctoral Research Fellow. There he continued to focus on structured adaptive mesh refinement (AMR) algorithms, and applied them to simulating multiscale nonlinear oceanic internal gravity waves. While at Stanford, he also taught several graduate level courses. Barad then came to NASA Ames in 2009 and works with Cetin Kiris within the LAVA group where his focus is applications and numerical tools. In LAVA, he has developed a high-order high-performance immersed boundary code for solving unsteady Navier-Stokes equations using adaptively refined structured Cartesian grids, requiring only a water-tight surface triangulation. Using the LAVA solver he has worked on numerous NASA projects, including: the 21st century launch complex at KSC; SLS buffet analysis; NESC Battery simulations; Landing Gear Noise; SOFIA cavity acoustics; and many others. He has published in the Journal of Fluid Mechanics, Journal of Computational Physics, and others. Barad received the NASA Early Career Achievement Medal in 2014.