Second Computational Aeroacoustics (CAA) Workshop on ...

Problem 3
This problem is designed to test the ability of a numerical scheme to model the p_0p-
agation of acoustic and vortical waves across a sliding-interface typical of those used in
rotor stator interaction problems.
Repeat Problem 2, but translate the portion of the grid aft of the line x = 2 in the
positive ?]-direction with speed 1. If possible, arrange the sliding grid motion so that at
times corresponding to the start of each period (t = 27rn/w) the sliding grid is in the
original nonsiiding position. This will aid in the plotting and evaluation of solutions.
Category 4 m Airframe and Automobile Noise
Aeolian tones, sound generation by flow over a cylinder, are relevant to automobile
antenna and airfl'ame noise. The purpose of this problem is to demonstrate computation
of sound generation by viscous flows.
Consider uniform flow at Math number 0.2 over a two-dimensional cylinder of diameter
D = 1.9cln as shown in figure 5. The Reynolds number based on the diameter of the
cylinder is 90,000. Perform numerical simulations to estimate the power spectra of the
radiated sound in dB (per 20Hz bandwidth) at r/D = 35 and 0 = 60 °, 90 °, 120 ° over the
Strouhal number, St = u/_-0 D, range of 0.01 < St __ 0'61 a{ ASt = 0.002,
You may use a smaller Reynolds number in your simulation. However, data may not
be available for direct validation.
verged.
Perform grid and time resolution studies to demonstrate that your solution has con-
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Figure 5
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