Measurement of the cavitation pattern by two non-intrusive techniques: laser imaging and ultrasound pulsed echography

We propose the use of ultrasound pulsed echography (UPE) for the mapping of the leading edge cavitation pattern, in view of its application to full-scale measurements on propeller blades aboard a ship in actual service. Measurements are done on a two-dimensional NACA16009 hydrofoil, and a comparison is performed against a well-tested technique based on laser light scattering imaging. On a reference solid surface, the mean location of the surface is recovered within ±0.5 % of the foil maximum thickness, against ±0.1 % for the imaging technique. In terms of uncertainty, UPE displays error levels four to six times higher with respect to the reference imaging data. In presence of cavitation, the UPE approach tends to overestimate the thickness dimension of the vapor volume as a result of its sensitivity to noise scattering from wall reverberation and from particles in the bulk fluid. However, the overall performance is highly satisfactory for a potential use in a full-scale context, and specific improvements are suggested to fulfill this long-term goal.