溝乱流の壁近傍の流れの考察

抄録

It is intended in this report to discuss the structure of near-wall turbulence by drawing pictures of flow fields of specified concerns using three-dimensional computer graphics. The flow taken here as the material is a two-dimensional channel flow obtained by a large-scale computer simulation. The discussion is focused on the streaks which are observed in all kinds of near-wall turbulence as a marked feature. It turned out that impinging, which is the key phenomenon in high-speed streaks, plays a key role in the near-wall turbulence as well as the lift-up and break-up of low-speed streaks. Most of the important events take place in these sparsely distributed spots. Turbulent shear stress is found only sparsely where it is produced, and the whole process of shear stress mostly restricts itself to within a small confined area. It was confirmed that although the pressure diffusion and the redistribution of shear stress are important when considered separately, they almost cancel one another and as a result the splitting of the velocity-pressure gradient term into these two terms is not beneficial in turbulence modelling.