Measurement of the time evolution of Rayleigh streaming in high-amplitude standing waves

Abstract

The time evolution of the axial component of the Rayleigh streaming velocity field in a cylindrical, air-filled resonator has been measured using laser Doppler anemometry. At low acoustic amplitudes, the measured field is in agreement with classical theory. The axial component varies sinusoidally along the axial direction and quadratically along the radial direction, and the position of maximum streaming velocity on the axis is located midway between the velocity node and velocity antinode. At higher acoustic amplitudes, the streaming velocity field initially resembles the classical result, but becomes progressively distorted as time passes. The position of maximum streaming velocity on the axis shifts towards the velocity antinode, while the streaming velocity outside the boundary layer, near the resonator wall, remains unaffected. Additionally, the radial dependence of the axial streaming velocity deviates from its initially parabolic shape, becoming flatter near the velocity node and steeper near the velocity antinode. The length of time required for the streaming to reach steady state is on the order of several minutes for a fundamental frequency of 310 Hz, a resonator radius of 23 mm, and an antinodal acoustic velocity of 6.0 m/s peak. [Work supported by ONR.]