Planar Doppler velocimetry
Planar Doppler Velocimetry (PDV), also referred to as Doppler Global Velocimetry (DGV), determines flow velocity across a plane by measuring the Doppler shift in frequency of light scattered by particles contained in the flow. The Doppler shift, Δfd, is related to the fluid velocity. The relatively small frequency shift (order 1 GHz) is discriminated using an atomic or molecular vapor filter. This approach is conceptually similar to what is now known as Filtered Rayleigh Scattering (Miles and Lempert, 1990).