Hydrofoil Testing At High Reynolds Number

Abstract

Lifting surfaces are used both for propulsion and control of sea vessels and must meet performance criteria such as lift, drag, and (in some military applications) hydroacoustic noise limits. Design tools suitable to predict such criteria must handle complex flow phenomena and manage the wide range of flow scales inherent in marine applications (Reynolds numbers ~10^8). To date, the development of such tools has been limited by the lack of controlled experimental data in this high Reynolds numbers range. Lifting surface flow is the focus of current high Reynolds number experiments involving a two-dimensional hydrofoil in the world's largest water tunnel, the US Navy's William B. Morgan Large Cavitation Channel (LCC). The goal of these experiments is to provide a unique high Reynolds number experimental dataset at chord-based Reynolds numbers (Re) approaching those of full-scale propulsors ( ~ 10^8). This data will be used for validation of scaling laws and computational models, with particular emphasis given to the unsteady, separated, turbulent flow at the trailing edge. In addition, these experiments will provide fundamental insight into the fluid mechanics of trailing-edge noise generation in marine propulsion systems. This paper describes the experimental equipment and methods employed in the test program. Described herein is the use of the LCC's Laser Doppler Velocimetry (LDV) capability to acquire flow velocity mean and turbulence quantities, as well as estimates of boundary layer transition. Also presented is a Particle Imaging Velocimetry (PN) system developed for these experiments and employs seed injection upstream of the channel's flow straightener. Finally, a description is given of instrumentation mounted in the foil for measurement of vibration and surface static and dynamic pressures. [Significant assistance provided by personnel from NWSC-CD, Sponsored by Code 333 of the Office of Naval Research].