Effects on the Boundary Layer Caused by Inclusion of Dimples at Varying Depths

On airfoils, dimples were found to lengthen the area of boundary-layer attachment at a high angle of attack. This paper presents the effects of dimple depth on the boundary-layer separation point for a NACA 2412 airfoil at an airspeed of 110 mph and a 20 deg angle of attack. Four airfoil models were tested: a baseline model without dimples and models with dimple depths of 0.04, 0.07, and 0.10 in., respectively. Results were obtained with a technique using a paint-solvent mixture. Results showed that boundary-layer attachment length did increase with increasing dimple depth. For the model with the greatest dimple depth (0.10 in.), the length of boundary-layer attachment increased by a factor of 3.7 when compared with the baseline model. [PUBLICATION ABSTRACT]