Instantaneous Pressure Distribution Around a Sphere in Unsteady Flow

Abstract

Pressure fluctuations on a small sphere in a periodically pulsating jet are measured in relation to the study of measurements of instantaneous static pressure in unsteady flows, where the wavelength of unsteadiness is much longer than the probe dimensions and the amplitude of the velocity fluctuation is small. Both the instantaneous pressure on the sphere and the instantaneous velocity of the flow field in the absence of the sphere are measured by means of periodic sampling and averaging techniques. The measured surface pressure is expressed in terms of the measured velocity and acceleration of the flow. A simple inviscid theory is developed and compared with the experimental results. An application of the present results to the correct determination of instantaneous static pressure in unsteady flows is discussed.