Abstract
The speckle photography has been established as a method of velocity measurement in two-dimensional flow field at the same instance. This method is based on taking a double exposure photograph (specklegram) of measuring field, seeded with tracer particles and illuminated by pulsed light sheets. If a pulsed light source combined a low-power CW-laser with a beam chopper is used for this method, the intensity of light sheet is not sufficient to obtain a fine specklegram of the flow suspending with small tracer particles following up the flow.
In this report, a new technique that the flow field is swept by a laser beam generated from a He-Ne laser source (15mW) is developed and named as the beam sweep laser speckle velocimetry. This method is applied to velocity measurement of a flow with a horseshoe vortex produced by a triangular column placed into a laminar boundary layer developed in a water channel flow suspending TiO2 particles (mean dia. 5μm). As the result, the fine specklegram is obtained for quantitative flow visualization.
