Since laminar separation bubbles are neutrally shaped on the suction surface of full-span wings in a low Reynolds number flows, a roughness element can be used to improve the performance of micro aerial vehicles (MAVs). The purpose of this paper was to investigate the roughness element effect and its location on the laminar separation bubble from phase portrait point of view. Moreover, most of the micro unmanned aerial vehicles (UAVs) are developed with military purposes and regulatory concerns forced to reduce noise. Therefore, passive control might have an acoustic side effect, especially when the bubble might burst and increase noise. Consequently, the effect of roughness element features on the bubble\\\'s behavior is considered on the acoustic pressure field and the vortices behind the NASA-LS0417 cross-section. The consequences express that the distribution of roughness in the appropriate dimensions and location could contribute to increasing the performance of the aerofoil and the interaction of vortices produced by roughness elements with shear layers on the suction side has increased the sound frequency in the relevant SPL.

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