Towing tank PIV measurement system, data and uncertainty assessment for DTMB Model 5512

Abstract

 A towed PIV system designed by DANTEC Measurement Technology for the Iowa Institute of Hydraulic Research towing tank is commissioned by measuring the mean velocity and Reynolds stresses at the nominal-wake plane of a model-scale ship. The mean velocities are compared with previous 5-hole pitot probe data. Uncertainty assessment following standard procedures is used to quantify the comparisons and reach conclusions regarding the quality of the data. The PIV results are analyzed with regard to axial velocity defects, axial vorticity, and level, pattern and anisotropy of turbulence. Quantitative comparisons with 5-hole pitot data shows that PIV uncertainties are about 1% lower than those for 5-hole pitot. However, data differences are larger than RSS of PIV and 5-hole pitot uncertainties for the axial and vertical velocity components, indicating unaccounted for bias and precision limits. The bias error of the pitot probe in a shear flow is discussed, and a method for reducing the bias error is suggested. The data is being used for verification and validation of RANS simulation of DTMB Model 5512.