Abstract
Calculations are performed to verify the dipole nature of the edgetone in which the flow consists of an incompressible two-dimensional jet issuing from a nozzle and impinging on a fixed rigid wedge-shaped body. The wedge body is abruptly removed from a previously computed, laboratory-verified, multifrequency edgetone flow at a Reynolds number of 450 and replaced by an oscillating dipole. The dipole strength is treated as unknown and part of the solution process but is such that the combination of the dipole flow and jet flow yields a transverse jet velocity time trace near the the dipole identical to that from the previously computed edgetone flow. The resultant flow field is numerically computed for a Reynolds number of 450 and, after initial start-up effects, the flow field for the latest cycle computed strongly resembles that of the previously computed edgetone flow. Results for the jet–dipole flow are given in the form of stream function and equivorticity contour plots and jet spectra. In addition, sound-pressure radiation due to a fluctuating pressure distribution at the surface of the wedge-shaped body is computed using data from the previously calculated edgetone flow. The moduli of the computed sound-pressure components corresponding to various time frequencies reveal on polar plots a figure eight pattern in the farfield with the largest component or tone associated with the frequency of jet impingement. According to theory, this is the farfield sound pattern due to a fluctuating dipole centered at the wedge tip with axis transverse to the wedge tip.
Published Version
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