SOME CHARACTERISTICS OF LOW-SPEED STREAKS UNDER SHEARED AIR-WATER INTERFACES

• 来源期刊: 力学学报（英文版）
• 学科: 物理学
• 年，卷（期）: 2001,（2）
• 页码范围: 115-124
• 页数: 10页
• 分类号: O3
• 语种: 英文

摘要

The characteristics of low-speed fluid streaks occurring under sheared air-water interfaces were examined by means of hydrogen bubble visualization tech nique. A critical shear condition under which the streaky structure first appears was determined to be uT ≈ 0.19 cm/s. The mean spanwise streak spacing increases with distance from the water surface owing to merging and bursting processes, and a lin ear relationship describing variation of non-dimensional spacing λ+- versus y+ was found essentially independent of shear stress on the interface. Values ofλ+, however,are remarkably smaller than their counterparts in the near-wall region of turbulent boundary layers. Though low-speed streaks occur randomly in time and space, the streak spacing exhibits a lognormal probability distribution behavior. A tentative explanation concerning the formation of streaky structure is suggested, and the fact that λ+ takes rather smaller values than that in wall turbulence is briefly discussed.