Tomographic spatial filter velocimetry for three-dimensional measurement of fluid velocity

Spatial filter velocimetry (SFV) is extended to three-dimensional three-component velocimetry by coupling the SFV processing with a tomographic technique, which reconstructs three-dimensional particle distributions from stereoscopic particle images recorded by two cameras. Since time duration of a ghost particle traveling through an interrogation area of SFV is shorter than the transit time of a real tracer particle, a validation method of velocity data based on a particle transit time is used to eliminate ghost particles generated in the particle reconstruction process. Effect of a ghost particle on velocity evaluation is not significant due to the short transit time of a ghost particle. The developed system is applied to a free jet, and an impinging jet discharged from a circular pipe. Three-dimensional distributions of time-averaged velocity vectors of the jets are successfully measured by the developed tomographic spatial filter velocimetry (Tomo-SFV) in spite of using only two cameras. The peak-locking errors, which are apt to occur in particle image velocimetry measurements, do not appear in Tomo-SFV measurements.