Experimental studies of shear stress and flow separation in low Reynolds number flows

Abstract

Presented here is an experimental investigation of the kinematic theory of separation in unsteady two-dimensional flows, and an evaluation of a novel optical shear stress sensor. Fixed separation in the rotor-oscillator flow is studied for steady, periodic, and quasi-periodic fluid motion. Experimental results are directly compared to numerical simulations, which provide the shear-stress and pressure data required for detecting fixed separation in an unsteady flow. Good agreement between theory and experiments in determining both the location of the separation point and the angle of the separation profile is found. With the goal of directly measuring shear stress to high accuracy, an optical shear stress sensor is evaluated on a flat plate boundary layer. Wall-shear measured with the sensor is compared to that derived from particle image velocimetry (PIV) velocity profiles, and the resulting discrepancy between the two measurements is discussed.