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At moderate Reynolds numbers, the perturbations may be intensified and laminar flow regime changes to turbulent flow regime. In transition process from laminar to turbulence, the flow tends to separate from a surface and then reattaches with it. As a result, some bubbles are formed which are called laminar separation bubbles. Understanding the physics of the separation bubble phenomenon and controlling of them are needed to proper aerodynamic devices design at moderate Reynolds numbers. This study has tried to enhance the aerodynamic efficiency of a low speed UAV airfoil and wing by using geometric heterogeneity like groove and bump. In this study; firstly, around CLARK-Y airfoil a proper turbulence model is proposed and effective value of Reynolds numbers on bubbles are obtained; secondly, a geometric heterogeneity is build and moved from leading edge to trailing edge on the airfoil and the performance of this airfoil is evaluated; Thirdly, geometric heterogeneity around the transition zone is changed and its effect on the performance of this airfoil is evaluated; and fourthly, some grooves and bump are arranged on the wing and their aerodynamic performance are compared relative to the clean wing. The results show that, the K-Kl-ω turbulence model is more accurate than others, higher Reynolds number lower bubble size, nearby transition point position is a good option for heterogeneity building, grooves enhance aerodynamic performance more than bumps, and a continues groove is obtained higher aerodynamic performance than clean wing but discontinues aligned grooves obtained lower aerodynamic performance than clean wing.

Keywords: Laminar Separation Bubble, Transitional Flow Control, Numerical simulation

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