Comparison of Wake Flow Measurements between 5-Hole Pitot Probes and Laser Doppler Velocimetry in the Ship Propeller Plane

Abstract

Wake flow measurements have traditionally been made with pitot probes. Most commonly used probes are of the 5-hole spherical and hemispherical head on cylindrical stem variety. A limitation is that the measurement can be intrusive and the probe may not physically fit in the area to be measured. One modern solution uses multi-component Laser Doppler Velocimetry (LDV) to measure the wake profile. A question arises as to how the laser measurements comp are with the pitot probe measurements. Experimental studies were conducted at the David Taylor Model Basin, Carderock Division, Naval Surface Warfare Center (formerly the David Taylor Research Center) where pitot probe s and LDV measurements were simultaneously collected in the propeller plane of a single screw ship model. No n-simultaneous wake measurements have also been collected on twin screw shaft and strut ship models. The two flow measurements correlate well at the outer propeller radii. Near the hub or in low-flow regions, the pitot probe axial velocities fall off more rapidly than LDV measurements.