2010 年 5 巻 3 号 p. 515-527
Direct numerical simulations (DNS) of turbulent flow through an asymmetric plane diffuser, consisting of a flat wall and an inclined wall, were performed using a high-order finite difference method, to reveal the relationship between turbulence and flow separations under negative pressure gradients. A typical feature of this flow field is the non-steady three-dimensional separation region formed near the inclined wall. At the opening of the diffuser, low speed streaks in wall turbulence cause the initial non-steady separation layer, which includes small-scale reverse flow regions. Because turbulent eddies growing from this initial separation suppress the separated flow, a small reattachment section is formed downstream. When turbulent eddies start to decay and the negative pressure gradient begins to dominate, the flow separates again, and then a large-scale separation region is formed. In summary, the intensity of turbulent eddies affects the formation of the separation and reattachment regions near the inclined wall.
