二维扁卵形体近壁面水动力干扰实验

对长度-厚度比为7.0的二维扁卵形体近平壁面运动的水动力特性进行了研究.拖曳水池试验选择了六种不同的壁面间距,五个攻角状态,将卵形体模型安装在U形槽中,保证流场的二维特性.Reynolds数范围从5×105到2×106.根据无界流实验结果,在数据处理中消除测力天平的安装角误差.给出了水动力系数相对于间距、攻角的回归公式,并划分了三个典型的干扰区域:升力区、混合区、阻塞区.实验表明:即使对于钝尾物体,也存在类似机翼的升力效应,无界流中扁卵形体的升力线斜率小于二维平板机翼的相应值.当物体离壁面较远时,水动力系数随攻角线性变化,壁面影响随间距减小而增大;当物体离壁面很近时,出现排斥现象,水动力系数随攻角的变化呈非线性特征.与其它参数相比,在大部分试验状态下,运动速度对水动力系数的影响较小.

Experiment on Hydrodynamic Interaction Between 2D Oval and Wall

The hydrodynamic characteristics of a 2D oval with length-thickness ratio 7.0 while moving near plane wall were presented.Towing-tank tests were conducted under six distinct wall clearances and five attack angles and the 2D characteristics of flow field were ensured by installing the oval model in a U-shape trough.The Reynolds numbers considered were in the range of 5×105 to 2×106 .Through corresponding measuring data in unbounded flow field,the installing angle error of balance to model was eliminated in data processing. The regressive formulae of hydrodynamic coefficients relative to clearances,attack angles were given.Three typical interaction regions were divided,defined as Lifting,Mixed and Blocking Region.The experimental results indicate that even for the blunt-end body,there exists lifting effect similar to wing, and the lift-curve slope of oval in unbounded field is smaller than that of 2D wing. When the wall clearance is large,hydrodynamic coefficients vary linearly with attack angle,and the influence of wall increases with the decreasing of clearance.While for small clearance, there appear repulsion phenomena, and the variation of coefficients with attack angle is nonlinear. The effect of velocity on hydrodynamic coefficients is small at most cases,compared with other factors.