关键词: 表面活性剂, 湍流, 微沟槽, 数值模拟, 协同减阻

Abstract:

A systematic study on the turbulent flow of surfactant solutions in different wide-rib rectangular microgroove channels was carried out by direct numerical simulation. The results showed that the drag reduction performance of surfactant solutions could be further enhanced in the grooved channel with a suitable groove size. The optimal size of microgroove for drag reduction could be enlarged in the surfactant solution. The collaborative drag reduction effect of surfactant solution in grooved channel was mainly the competition result of the “restriction effect” and the “tip effect” of the microgroove. There was a higher shear stress near the grooved tips, but the stress was very small within the grooved valley. If the microgroove not only prevents the near-wall vortices from intruding into the grooved valley effectively, but also presents a better restriction effect on the spanwise motions of the near-wall streamwise vortices, the microgroove will show a drag reduction enhancement effect. On the contrary, if the size of microgroove increases too large to prevent the near-wall vortices from intruding into the grooved valley, the shear stress near grooved tip and within grooved valley will increase, and the microgroove will show drag-increasing performance. The fact that a large number of small and weak secondary streamwise vortices induced in the grooved valley is the key factor to increase the restriction effect and thus enhance the drag reduction of surfactant solutions.

Key words: surfactants, turbulent flow, microgroove, numerical simulation, collaborative drag reduction