Laser Velocimetry

Laser velocimetry, often referred to as laser anemometry and laser flowmetry and also known by some other names which will be used below, is a set of laser techniques designed for noncontact, remote measurements of velocities of gaseous, fluid, and solid media. Basically all these techniques make use of light scattering by tracer particles naturally present in the gaseous, fluid, and tissue-like media or specially administered therein, or light scattering inhomo-geneities and roughness on the solid surfaces. In this sense, laser velocimetry is based on light scattering theory, in most cases within the Mie theory approximation. There exist also laser velocimetry techniques based on detecting laser-induced fluorescence signal from moving fluorescing species. However, this set of techniques is beyond the scope of this chapter.

Being able to perform nonperturbing velocity measurements is very important for solving various basic problems of experimental fluid mechanics and gas dynamics, as well as of biomechanics, in particular, hemodynamics. The applications of different variants of laser velocimetry range from the study of aircraft and vehicles, combustion, multiphase flows, channel and cavity flows, boundary layers, natural convection, unsteady flows and flow instability, vortices, turbulence, and large-scale environmental flows, to low-Reynolds-number and microscale flows, in particular, in medical/physiological applications. In all these applications, the noncontact, noninvasive, and nondestructive mode of measurement is of utmost importance.