Extended particle streak velocimetry (E-PSV) for a comprehensive view of film flows

Abstract

Extended particle streak velocimetry (E-PSV) is a novel approach for comprehensive 2D flow measurement. It extends the measuring range of particle streak velocimetry (PSV) via particle tracking velocimetry (PTV). By using long camera exposure when recording moving tracer particles, streaks are created in areas of high flow velocities (PSV). In areas of low velocity, in contrast, particles are imaged point-shaped (PTV). E-PSV hereby offers the advantage of continuous measurement with PSV-typical setups, particularly when areas close to the wall and vortices require to be recorded simultaneously with areas of high velocity. For precise extraction of the flow information, a new model for the description of particle images is presented. It is based on the assumption that the intensity of a tracer can be modeled by a 2D Gaussian function. The temporal integral of the moving Gaussian is approximated by combining analytical calculation with values from a lookup table. We show that by this method even curved streaks can be reconstructed with subpixel accuracy under noise and quantization effects. The technique is demonstrated using a film flow in vicinity of a microstructure.