### ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

## 2aNS6. Numerical simulation of aerosound from airfoils and exhaust jets
using lighthill theory with k-(epsilon) turbulence model and large eddy
simulation.

**Wei-Jen Huang
**

**
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.