Analysis of Surface Augmentation of Airfoil Sections via Flow Visualization Techniques

This report details an experiment done to verify the effectiveness of two passive flow control systems on two-dimensional airfoil sections. The flow control was tested on two types of airfoils: a symmetric NACA 0011, intended to represent an airplane in cruise, and a NACA16611, intended to represent an aircraft with flaps extended. Two types of passive systems were employed, a dimple surface augmentation, similar to a golf ball, and a grit system located at 20% chord. Airfoils without either augmentation were tested as a control case. Using a water tunnel and dye to perform flow visualization, the effects of each system were analyzed. Comparison of the image data demonstrated that the surface augmentation dimples aided in delaying the flow separation from the upper surface. The boundary layer separation was measured by using images and locating the point of separation and using the chord line to convert to percent chord separation. The data showed conclusively that the airfoil test section with surface augmentation from 8% chord to the trailing edge had reduced separation throughout the 6 different tests