David B. Schein
William C. Meecham
Dept. of Mech. and Aerospace Eng., Univ. of California, Los Angeles, CA 90095
Far-field noise from turbulence near an NACA 0012 airfoil and potential core of a high-speed (subsonic) jet engine exhaust have been computed using the ANSWER computational fluid dynamics code of Runchal and Caretto [Intl. J. Num. Methods Eng. 24 (1990)] and Lighthill's acoustic analogy. The k-(epsilon) turbulence model which is part of ANSWER is used to compute Reynolds stress from two ``side'' equations in addition to continuity, Navier--Stokes, and for high-speed flow, the energy equation. Three-dimensional turbulence intensities are obtained from the stress. Fluctuations are needed to calculate aerosound, while k-(epsilon) only produces averages. Thus the time derivative form of Lighthill's analogy is used to calculate the sound. Time derivatives must be estimated; the characteristic time L/u[sup '], as calculated by k-(epsilon), is used. ANSWER modified to perform Large Eddy Simulation is used for the free jet, employing a hybrid subgrid scale model previously developed for application to a low-speed jet by Lee [UCLA dissertation (1992)] which combines the conventional Smagorinsky formulation with a deductive model formed by taking a Taylor series expansion of the flow field and using the first terms to give the fluctuations. Preliminary results are compared with jet noise measurements.