Submitted to the 17th AIAA/CEAS Aeroacoustics Conference, 6-8 Jun 2010, Portland, Oregon Unstructured Large Eddy Simulation for Prediction of Noise Issued from Turbulent Jets in Various Configurations Yaser Khalighi * , Cascade Technologies Inc., Palo Alto, CA 94303 Joseph W. Nichols † , Stanford University, Stanford, CA 94305 Frank Ham ‡ , Cascade Technologies Inc., Palo Alto, CA 94303 Sanjiva K. Lele § , and Parviz Moin ¶ Stanford University, Stanford, CA 94305 A novel numerical scheme for unstructured compressible large eddy simulation (LES) is developed. This method is low-dissipative and less sensitive to the quality of the computa- tional grid and is targeted for performing large-scale, high-fidelity simulations of turbulent flows in complex configurations. The objective of this work is to introduce this method, present a rigorous validation study, and demonstrate the application to a variety of jet configurations. This technique is validated by predicting the flow and noise emitted from a single-stream pressure-matched hot supersonic jet. Nearfield flow as well as farfield noise computed using an acoustic projection method is studied and compared to experimental measurements obtained by Dr. James Bridges at NASA Glenn. Mesh refinement studies and sensitivity study on selecting the acoustic projection surface are provided. To test the method’s performance in a variety of jet noise configurations, it is applied to a high bypass ratio dual-stream jet at sonic conditions, a vertical supersonic jet impinging on the ground, and a horizontal supersonic jet impinging on an angled jet blast deflector. I. Introduction Existing engineering methods for estimating the noise of propulsive jets rely heavily on empirical databases developed from scale model testing and the available full-scale data. While these semi-empirical methods provide useful first estimates, they lack the sensitivity to design/configuration changes needed to usefully evaluate the benefits and drawbacks of various strategies for mitigating the noise. A prediction method based on large eddy simulation (LES) which captures the physics of the various relevant aerodynamic noise gener- ation processes and their interactions while treating the realistic geometrical configurations is now feasible. By capturing the unsteady flow physics responsible for the noise-generation, LES provides a first-principles approach to understand the crucial contributors to jet aeroacoustics, and to evaluate various strategies for mitigating the noise impacts. This physics-based approach is free of any user-defined models or parameters or empirical constants. However, its predictive capability centrally depends on adequate capturing of the unsteady flow phenomena responsible for noise generation. In high Reynolds number complex turbulent flows this requires a careful design of the mesh to capture the noise-source dynamics directly and thus LES requires substantially more computer resources than steady state RANS calculations. * Technical Lead, khalighi@cascadetechnologies.com † Research Associate, Center for Turbulence Research ‡ Chief Technology Officer § Professor, Dept. of Mechanical Engineering and Dept. of Aeronautics and Astronautics ¶ Franklin P. and Caroline M. Johnson Professor of Mechanical Engineering 1 of 16 American Institute of Aeronautics and Astronautics