Effects of three-dimensional (3-D) distributed roughness elements on the flow characteristics within a cavity are investigated using a series of high-fidelity eddy-resolving simulations. The cavity flows generate undesirable low-frequency pressure fluctuations due to the vortex impingement over the trailing edge of the cavity. We explore the possibility of employing distributed hemispherical roughness elements as a passive flow control strategy towards suppressing these pressure fluctuations. A rectangular cavity with a length to depth ratio, L/D, of 3 is considered. Simulations are carried out at a Mach number of 0.2 and Reynolds numbers of 7000 and 19300, based on the free-stream velocity and the depth of the cavity. The effect of sparsely and densely packed roughness elements on the stability of shear layer separating from the cavity are brought out. Pre-transitional fluctuations generated by the roughness elements (a) resulted in transitional/turbulent flow at the cavity leading edge for low/high Reynolds numbers (b) promoted an earlier breakdown of the large-scale coherent structures in the shear layer (c) are beneficial in decreasing the ‘cavity tones’ and the associated sound pressure levels (SPL) by 5-13 dB. Reduction in SPL is observed to be prominent at higher Reynolds numbers and with dense spacing between the roughness elements. At low Reynolds numbers, the benefit obtained by suppressing the ‘cavity tones’ can be eclipsed with an increase in the broadband noise.

使用一系列高保真涡流解析模拟研究了三维 (3-D) 分布粗糙度元素对腔内流动特性的影响。由于在空腔后缘上的涡流冲击，空腔流动会产生不希望的低频压力波动。我们探索了使用分布式半球形粗糙度元素作为被动流量控制策略来抑制这些压力波动的可能性。具有长深比L / D的矩形空腔, 3 被考虑。基于自由流速度和空腔深度，以 0.2 的马赫数和 7000 和 19300 的雷诺数进行模拟。提出了疏密堆积粗糙元对剪切层与空腔分离稳定性的影响。由粗糙度元素产生的过渡前波动 (a) 导致低/高雷诺数 (b) 的腔前缘处的过渡/湍流流动促进了剪切层中大规模相干结构的早期破坏 (c)有利于将“腔音”和相关的声压级 (SPL) 降低 5-13 dB。在较高的雷诺数和粗糙度元素之间的密集间距下，观察到 SPL 的降低是显着的。在低雷诺数时，