高解像度粒子画像流速測定法による自由噴流内の乱れ生成・消散率の計測

抄録

High-resolution particle image velocimetry was used repetitively to obtain the time-change of instantaneous velocity vectors, which enabled us to analyze turbulence kinetics. Each term in the balance equation of turbulence energy was evaluated, based on the ensembles of fluctuating velocities and instantaneous velocity-gradients, thereby finding the factors primarily responsible for production and dissipation of turbulence energy. It was shown that the turbulence production rate is high in the shear layer because of a large Reynolds stress, and viscous dissipation of turbulence energy occurs mainly near the jet axis. Furthermore, typical turbulence eddies in the shear layer were sampled to discuss the effects of instantaneous vortices and fluctuating flow on turbulence production. It was shown that elliptical shape of vortex observed in the shear layer might significantly contribute to the turbulence production. Also, the effect of vortex shape and arrangements on the local turbulence production were discussed in more detail. There were two regions with turbulence production around the vortex and the local turbulence dissipation distributes in the center of the vortex.