减阻沟槽表面对湍流边界层高阶矩特性的影响

Effect of Drag Reducing Grooved Surface on High-Order Moments in Turbulent Boundary Layer

以光滑平板及间隔V型减阻沟槽面为研究对象,利用二维LDV系统获得光滑平板及沟槽板上部区域湍流边界层流场的流动参数。通过象限分析法深入研究减阻沟槽表面湍流边界层中雷诺切应力的变化情况,着重考察沟槽面对湍流边界层高阶统计参数的影响,并将高阶统计参量同湍流边界层相干运动规律结合起来,由此来探讨沟槽面与湍流边界层之间的相互作用规律。结果表明,沟槽的存在抑制了整个近壁区低速条带的喷射运动,降低了y+<15区域内高速流体的下扫强度;雷诺切应力以及湍动能的法向输运主要是由喷射和下扫这两种运动来完成的,沟槽的存在削弱了雷诺切应力及湍动能的法向输运水平;沟槽的存在减小了y+<13区域内的流向速度脉动的偏斜因子与y+<3区域内流向速度脉动的平坦因子。

Measurements of flow field by means of a two- component LDV have been carried out in turbulent boundary layers over a smooth surface and a spaced V- type drag reducing grooved surface with a zero pressure gradient. Quadrant analysis method was employed in analyzing the detail changes of Reynolds shear stresses and other turbulent statistics parameters, with the emphasis on high- order moments, Special attention b.as been paid to the relationship between the high - order moments and the turbulent coherent motions, The results show that the ejection motions in the whole near - wall region are mitigated, sweep motions in the region for y^＋ 〈 15 are impaired, the wall- normal transportations of Reynolds shear stress and turbulent kinetic energy are mainly undertaken by ejection and sweep of motions, the capability of wall- normal transportation is impeded by the existence of grooves, at the same time the skewness and flatness of streamwise velocity fluctuations are reduced by drag reducing grooves in the region for y ^＋〈 13 and y^＋ 〈3, respectively.