ABSTRACT
Laser anemometry, or laser velocimetry, refers to any technique that uses lasers to measure velocity. e most common approach uses the Doppler shi principle to measure the velocity of a owing uid at a point and is referred to as Laser Doppler Velocimetry (LDV) or Laser Doppler Anemometry (LDA). is technique (also known as dual beam, dierential Doppler, or fringe mode technique), incorporating intersecting (focused) laser beams, is also used to measure the motion of surfaces, for example, in industrial applications [1]. In some special ow situations, another approach using two nonintersecting, focused laser beams known as Laser two focus (also known as Laser transit velocimetry or L2F) technique is used to measure ow velocity at a point [2]. Laser illumination by light sheets is used to make global ow measurements in a plane and is referred to as Particle Image Velocimetry (PIV) [3]. e strength of PIV (including particle tracking velocimetry) lies in its ability to capture instantaneous velocity elds, extract turbulence structures within the ow, observe transient phenomena, and examine unsteady ows. e development of this technique to obtain both spatial and temporal information about ow elds is making this a powerful diagnostic tool in uid mechanics research [4-6]. More recently, using pulsed-laser volume illumination (in place of light sheet illumination), combined with multi-camera capture of particle images in a volumetric region in the ow, has provided the instantaneous velocity vector eld in the three-dimensional domain [7]. Other approaches to measure global ow velocities come under the category of molecular tagging velocimetry [8] or Doppler global velocimetry [9].
