Optical velocimeters for use in seawater

Laser velocimeters are versatile instruments in controlled liquid flows, wind tunnels, and atmospheric environments. The first steps are now being taken to bring the versatility of these instruments to use into the more difficult ocean environment. In this environment optical clarity and particulate concentrations are not adjustable and this presents significant constraints in the design of such systems. This paper describes the investigative work that is presently being performed to make the transition. The analysis considers natural waterborne particulate concentrations, optical propagation phenomena, and signal processor behavior. Preliminary conclusions are that optical velocimeter devices are likely to be employed in the study of ocean wave action, in the study of turbulence and material transport, in the study of advective and convective currents, in the study of structure-generated flow fields, in the study of particulate microdynamics, in the more detailed analysis of particulate size distributions, and even in the optical detection of sound transmission in water. The data base which was used in performance calculations thus far seems adequate for our present optimism, but not conclusive without experimental demonstration and additional performance model verification. Experiments for these purposes are planned for 1978.