Passive Drag Reduction of Wall-Turbulent Flows

该项目的目标是开发一种有效的壁面湍流被动减阻装置。为此，提出了两个模型来模拟聚合物的作用，聚合物在减阻中起着重要的作用，称为汤姆斯效应。第一种模型是用静电法将细纤维长丝沉积在平板上。“羊毛”平板的阻力是由专门设计的仪器测量的，使用平衡方法，将微小的阻力检测为轻微的流向位移。然而，测量结果表明，由于难以获得足够细的纤维丝来满足目的，该模型没有减少阻力。然后对第二个模型进行测试，该模型由放置在平板上并沿顺流方向排列的钓鱼线组成。对于最佳配置，观察到阻力减少约7%。这种情况下突起的高度比细纹情况小得多。

The objective of the project is to develop a devise effective for passive drag reduction of wall-turbulent flows. For this purpose two models are proposed to simulate roles of polymers which plays important roles in drag reduction known as Toms' effect. The first model is fine fibre-filament deposited on a flat plate by means of electrostatic method. The drag of the 'woolly' flat plate is measured by a specially designed apparatus using a ballancing method which edtects minute drag force as slight streamwise displacement. The measurements show, however, no drag reduction for the model because of difficulty in obtaining fibre filament fine enough to meet the purpose. The second model is then tested which consists of fishing lines placed on a flat plate and alligned in streamwise direction. For optimum configuration the drag reduction of about 7 % is observed. The height of protuberance for this case turns out to be much smaller than the riblets case.