Boundary layer separation negatively influences the performance of aerospace vehicles, for example, by triggering static stall or reducing combustion engine efficiency. Developing effective flow control to delay or eliminate separation is therefore of real use to the field. In this paper, numerical studies were carried out to optimise distributed suction profiles for preventing boundary layer separation on a circular cylinder in the fully laminar regime (), with the least control effort. Relationships were found between the Reynolds number, the separation angle of the uncontrolled case, and the uniform suction needed to eliminate separation. It was found that for , the uniform suction required to eliminate separation followed a quadratic profile, as a function of . Maximum uniform suction effort was needed at , requiring a suction coefficient of (as a percentage of the free-stream velocity) to eliminate separation. To resolve the best nonuniform suction profile at , a variety of optimisation studies were performed using the coordinate search method. It was determined that the use of six control segments on each half of the cylinder provided the best control and efficient convergence to the optimal solution. 6-segment nonuniform suction eliminated separation at with net suction effort of compared to for the uniform case. These optimal suction profiles were compared using time-dependent simulations to confirm that both methods eliminate separation when introduced to an already unsteady case. Nonuniform suction eliminated separation faster, though uniform suction was more stable.

中文翻译：

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消除非均匀吸力作用下圆柱体的边界层分离

边界层分离会对航空航天器的性能产生负面影响，例如，通过触发静态失速或降低内燃机效率。因此，开发有效的流量控制以延迟或消除分离在该领域中是真正有用的。在本文中，进行了数值研究以优化分布式吸力分布图，以防止在完全层流状态下圆柱体上边界层的分离（），以最少的控制力。在雷诺数，不受控制的情况下的分离角度和消除分离所需的均匀抽吸之间发现了关系。发现，对于，为消除分离所需的均匀抽吸遵循二次曲线，是的函数。需要最大的均匀吸力，要求吸力系数为（以自由流速度的百分比表示）以消除分离。为了解决最佳的非均匀吸力分布，使用坐标搜索方法进行了各种优化研究。已确定在汽缸的每个半部上使用六个控制段可提供最佳控制，并有效收敛到最佳解决方案。6段非均匀抽吸消除了分离 净吸力为 相比 对于统一的情况。使用依赖于时间的模拟对这些最佳吸力曲线进行比较，以确认在引入到已经不稳定的情况下，两种方法都可以消除分离。尽管均匀抽吸更稳定，但非均匀抽吸可更快地消除分离。