一维周期与准周期排列沟槽结构的流体减阻特性研究

本文设计了具有相同平均沟槽密度的三种排列类型的一维沟槽结构: 密排列、周期间隔排列和两种准周期间隔排列, 并采用数值模拟和实验验证相结合的方法研究了一维沟槽结构在不同排列下的流体减阻特性. 模拟计算分析流场特征和总阻力, 发现相对于密排列和周期间隔排列的沟槽结构, 准周期间隔排列具有更好的减阻特性, 并且这一结果得到减阻实验的验证. 通过流场分布特性进一步分析沟槽结构的减阻机理. 机理分析发现高速流在经一维准周期结构的扰动波调制后形成了准周期间隔排列的速度条纹相, 这有效地抑制了大涡在流向和展向上的形成, 从而实现较大幅度的减阻. 同时对比分析沟槽排列结构调制展向涡和流向涡各自对流动减阻的贡献, 结果表明, 调制流向涡对减阻的作用更大. 关键词： 流体减阻 沟槽结构 准周期

Drag-reduction of one-dimensional period and puasiperiod groove structures

We design three types of groove structures which are arranged in closely-packedarry (space free), periodic and quasiperiodic orders. The drag reduction properties of these structures are studied by numerical simulations and experimental shear stress measurements. Particularly, the effect of groove arrangement on the drag reduction is elucidated. Based on both the numerical and experimental results, it is found that the quasiperiodic arrangement can obtain more effective drag reduction than the close-packed groove structure and periodic structure. The underlying mechanism of the drag reduction is analyzed by vortex redistribution caused by the groove structures. The high-speed flow can be modulated by the disturbance wave resulting from the quasi-periodic groove structure, forming stripe-like flow patterns arranged in quasiperiodic style. This restrains the formation of big vortex in both the spanwise and the streamwise directions, hence leading to substantial drag reduction. Furthermore, the modulation effect on the streamwise vortex is more remarkable than on spanwise vortex, suggesting that the modulation of streamwise vortex plays a more important role in the drag reduction.