velocimeter

noun

1. any of various instruments for measuring velocity, as of a wave in water or of sound in air.

1. A device that utilizes the Doppler effect to measure the speed of sound in water. Developed by the US Army Corps of Engineers, a velocimeter transmits a pulse of sound through water and measures its echo for changes in either pitch or frequency. Oceanographers employ velocimeters to study the interior structure of breaking waves; they are also used in hydraulic engineering and to study fluid flow.