论文标题
翼型边界层气泡分离和过渡流
Airfoil Boundary Layer Bubble Separation and Transition in a Surging Stream
论文作者
论文摘要
理论上研究了高振幅谐波飙升对翼型层流气泡的影响，并在专用的涌出流风隧道中进行了实验。开发了一个广义压力系数，该压力系数涉及局部静压变化，这导致了由于急剧增长而导致的。这种概括以前从未实施过，促进了飙升和准态压力系数之间的直接比较，因此可以将不稳定效应与雷诺数效应区分开。实施了动量 - 融合边界层分析，以确定气泡分离点的运动，并从实验表面压力系数中提取过渡点的运动。最重要的发现是，在早期施加有利的颞压梯度时，违反直觉发生气泡破裂。这是因为有利的压力梯度迅速驱动泡沫尾部，使其无法重新构成。爆发导致了较大的升力和形式拖拉系数的振荡，并且未能实现广义压力系数定义，导致时间拖动误差最多为400个计数。
The effect of high-amplitude harmonic surging on airfoil laminar separation bubbles was investigated theoretically, and experimentally in a dedicated surging-flow wind tunnel. A generalized pressure coefficient was developed that accounts for local static pressure variations due to surging. This generalization, never previously implemented, facilitated direct comparisons between surging and quasi-steady pressure coefficients, and thus unsteady effects could be distinguished from Reynolds number effects. A momentum-integral boundary layer analysis was implemented to determine movement of the bubble separation point, and movement of the transition point was extracted from experimental surface pressure coefficients. The most significant finding was that bubble bursting occurs, counterintuitively, during early imposition of the favorable temporal pressure gradient. This is because the favorable pressure gradient rapidly drives the bubble aft, rendering it unable to reattach. Bursting resulted in large lift and form-drag coefficient oscillations, and failure to implement the generalized pressure coefficient definition resulted in temporal form-drag errors of up to 400 counts.
