Performance Prediction for Optical Wall Shear Stress Sensor Using Direct Numerical Simulation of Fluid Flow

We conducted a performance prediction for an optical wall shear stress sensor with using the velocity data of a direct numerical simulation. The Doppler signals were generated with respect to the path of tracer particles passing through the measurement volume. A signal processing technique was proposed to estimate the magnitude and yaw angle of local wall shear stress simultaneously from each Doppler signal. The simulated Doppler signals were processed with the technique, however the accuracy of estimating the yaw angle is not sufficient. In contrast, the estimated magnitude of wall shear stress showed a good agreement with the direct estimate from the DNS data if the yaw angle was accurately estimated. The measurement accuracy of the sensor mainly depends on estimating the yaw angle of each tracer particle. Another technique for detecting the yaw angle is needed for the accurate measurement of both the yaw angle and magnitude of local wall shear stress.