壁面加热湍流相干结构的子波分析实验研究

The Experimental Investigation of Wavelet Transform on Coherent Structure Influenced by Heated Wires on the Wall

通过在平板湍流边界层沿流向固壁表面平行放置若干条通电加热的金属细丝,在平板表面形成沿展向周期性分布的温度场,利用该温度场引起的空气热对流,在湍流边界层近壁区域产生一组沿湍流边界层展向周期分布的大尺度流向涡结构,改变了平板湍流边界层中不同尺度结构及其能量分布。采用对壁湍流多尺度结构的子波分析表明,在湍流边界层近壁区域产生规则的流向涡结构将壁湍流各种尺度湍涡结构不规则的脉动有序地组织起来,抑制了壁湍流各种尺度湍涡结构脉动,特别抑制了能量最大尺度湍涡结构的脉动,减小由于湍流脉动引起的在湍流边界层法向和展向的动量和能量损耗,从而减小了湍流的阻力。

A group of manipulated longitudinal vortex is introduced on the surface of a flat plate in a turbulent boundary layer by a group of longitudinal heated wires. Periodical variation of temperature in span-wise of flow field is formed on the surface of flat plate. With thermal convection of this periodical temperature field, the heated wires in the turbulent boundary layer generates a group of longitudinal vortex, which changes the distribution of multi-scale eddy structures and their energy in the turbulent boundary layer. This change organizes and controls the original eddy structures in the turbulent boundary layer and reduces the turbulent cost of momentum and energy. Controlling turbulence and reducing turbulent drag are finally realized.The results of wavelet transformation show that the manipulated longitudinal vortex introduced in turbulent boundary layer makes the disorder fluctuation of multi-scale eddy structures organized. Fluctuations of multi-scale eddy structures are restrained, especially for maximum energy scale eddy structures. The cost of momentum and energy for turbulent fluctuation in the normal and span-wise of turbulent boundary layer is decreased. Therefore turbulent drag is reduced.