Active management of naturally separated flow over a solid surface. Part 2. The separation process
Active management of naturally separated flow over a solid surface. Part 2. The separation process
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主动管理固体表面上自然分离的流动。
DOI：
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发表时间：
2004
影响因子：
3.7
通讯作者：
I. Wygnanski
中科院分区：
文献类型：
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作者：
A. Darabi;I. Wygnanski
对大倾角直襟翼的控制分离进行了实验研究。分离过程是由襟翼肩部的一个缝发出的激励的突然变化引起的。驱动的完全停止导致在襟翼上方形成一个大的涡流，类似于在俯仰振荡翼型上看到的熟悉的“动态失速涡流”（DSV）。DSV在襟翼降到其低分离值之前暂时增加了襟翼上的气动载荷。这种过载的持续时间随着襟翼倾角的增加而减少。分离期间使用周期性激发会减慢分离速率，并根据所使用的振幅和频率改变其特征。通过将激励切换到高频（$3，{<}，F^{+}，{<}，8 $）来强制分离，减少甚至消除了与DSV相关的襟翼载荷的增加。切换到低频（$F^{+}，{<}，1 $）延长了分离的持续时间，并增加了过程初始阶段的瞬时过载。
The controlled separation of flow from an inclined straight flap at high inclination angles was investigated experimentally. The separation process was initiated by an abrupt change in the excitation emanating from a slot at the flap shoulder. A complete cessation of the actuation resulted in formation of a large vortex above the flap akin to the familiar ‘dynamic stall vortex’ (DSV) seen over oscillating airfoils in pitch. The DSV temporarily increased the aerodynamic load over the flap before it dropped to its low separated value. The duration of this overload decreased as the flap inclination increased. The use of periodic excitation during separation slowed down the rate of separation and changed its character depending on the amplitude and the frequency used. Forcing separation by switching the excitation to a high frequency ($3,{<},F^{+},{<},8$) reduced or even eliminated the increase in flap loading that is associated with the DSV. A switch to low frequencies ($F^{+},{<},1$) extended the duration of separation and increased the transient overload during the initial stage of the process.