Measurement of Fluid Velocity Using Laser Doppler Velocimetry

Benjamin Gleason and Elias Peterson

University of Minnesota

Methods of Experimental Physics Spring 2012

Abstract

Laser Doppler Velocimetry is utilized to measure the flow velocity of water pumped through transparent glass tubing. When the water is seeded with particles, the particles pass through an interference region at the intersection of two coherent laser beams and reflect light into a photomultiplier tube. A burst signal is observed, and particle velocity is calculated from its frequency. The velocity profile of the glass tubing is modeled and compared to existing data and theory, and we attempt to observe at what fluid speeds laminar flow turn into turbulent flow.