低Re数自由噴流の初期過渡流れの直接数値計算と実測値による検証

抄録

We report the differences between transitional and steady flows of a free jet. In this calculation, the fifth-order upwind finite difference scheme and Runge-Kutta method are applied to the convective terms and the time developing term, respectively, in three-dimensional Navier-Stokes equations to simulate directly the free jet flow. The calculated flow field ranges from the nozzle exit to the developed turbulent region. The computational cell size is smaller than the Kolmogorov microscale in the developed region. Calculated results are compared with experimental data of flow visualization, velocity fluctuation and FFT analysis, and found to be in fairly good agreement with experimental data. Large-scale vortices which are created in the early transitional flow lead to differences between transitional and steady flows. The direct numerical simulation accurately represents the motions of microscale eddies in a free jet.