脊状表面减阻机理研究

Drag Reduction Mechanism of Riblet Surface

针对脊状表面流场的特点,通过实验测量和数值模拟的方法对脊状表面微观流场进行了深入研究,获得了脊状表面湍流边界层的时均速度分布曲线、湍流度分布曲线和微观流场结构.为了得到脊状结构对壁面物性的影响,对脊状表面进行了疏水性测试,获得了液滴在脊状表面上的表观接触角,并通过水洞试验验证了脊状表面的减阻效果.研究表明,与光滑表面相比,脊状表面微观流场结构中存在"二次涡",近壁区的黏性底层厚度比平板的要厚得多,湍流度显著降低,且脊状表面表现出明显的疏水性.由此提出了基于壁面隔离效应、增大湍流阻尼效应和改变壁面物性效应的减阻机理.

According to the characteristic of flow field of riblet surface, microcosmic flow field of riblet surface was studied thoroughly through experimental measurement and numerical simulation. Distribution of mean velocity, distribution of turbulence intensity and microstructure of turbulent boundary layer of riblet surface were obtained. To understand the effect of structure of riblet surface on properties of wall, the apparent contact angle of riblet surface was measured and drag reducing effect of riblet surface was confirmed by water - tunnel experiment. The results showed that compared with smooth surface, there was secondary vortex in micro flow field, the viscous sub - layer in the near region of riblet surface was thicker, turbulence intensity was depressed and riblet surface was hydrophobie. Finally, the drag reduction mechanisms based on wall separating effect, increasing turbulence damp effect and altering wall character effect were proposed.