Laser Doppler Velocimetry Techniques in the Large Cavitation Channel

Abstract

Recent demands for making velocity measurements on complex models in the Large Cavitation Channel have required the use of innovative techniques in the application of Laser Doppler Velocimetry (LDV). Several typical models, from bodies of revolution to fully-appended surface ships, are shown to demonstrate various effective techniques used in obtaining LDV measurements. Furthermore, LDV measurements of test section and diffuser flows obtained in the absence of a model are compared favorable with wind tunnel model data.

High Reynolds number experimentation in the US Navy's William B Morgan Large Cavitation Channel

“…Laser Doppler velocimetry (LDV) is by far the most common technique used for water velocity measurements in the LCC. Two Dantec direct-backscatter LDV systemsa stationary single-component system for reference measurements and a traverse-mounted two-component system for surveys-are resident at the LCC and are described in Blanton (1995b). Recent improvements to these systems are described in Park et al (2002Park et al ( , 2003.…”

“…Recent improvements to these systems are described in Park et al (2002Park et al ( , 2003. Particle seeding for LDV purposes has been frequently unnecessary (Blanton and Etter 1995), has merely involved flood seeding the entire LCC volume with silicone carbide or titanium dioxide particles (1-2 µm average size), or has involved injection of silvercoated spheres 4 µm in diameter from the test model (Fry 1995). The LDV test that involved the injection of the silvercoated spheres was conducted using a custom hub-mounted optical arrangement that allowed the quantification of the flow in the wake plane from within a nearly axisymmetric body that was being tested.…”