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

## 2aNS1. Recent developments in computational aeroacoustics.

**Lyle N. Long
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*Penn State Univ., 233 Hammond Bldg., University Park, PA 16802
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There is renewed interest in predicting aeroacoustic noise, especially for
jets, rotating blades, and shock waves. These flows involve nonlinear,
three-dimensional, turbulent phenomena, and nonuniform free streams. Simulating
these flows requires algorithms quite different than those traditionally used in
computational fluid dynamics (CFD). The time-dependent nature of aeroacoustic
problems requires the algorithm to correctly simulate the dispersion and
dissipation features of the flow. Good CFD algorithms usually rapidly damp out
all but the steady-state portion of the flow, and are inappropriate for
aeroacoustics. Computational aeroacoustics schemes have more in common with
large eddy simulation (LES) algorithms than those used in CFD. Recent progress
in higher-order algorithms for supersonic jets [T. S. Chyczewski and L. N. Long,
16th AIAA Aeroacoustics Conference, Paper 95-011 (1995)] and fan noise [Y.
Ozyoruk and L. N. Long, 16th AIAA Aeroacoustics Conference, Paper 95-063 (1995)]
illustrates that quite complicated aeroacoustic problems can be simulated. These
algorithms require roughly 5-10 grid points per wavelength. The large demand on
computer memory and speed requires that one use modern parallel computers, such
as the IBM SP2 and the TMC CM-5. One must be careful to properly load balance
the scheme and to minimize interprocessor communication. Kirchhoff surfaces are
very effective in predicting the far-field solution.