Jakkali, V., Huebsch, W., Robert, A., Hamburg, S. et al., "Investigation of Dynamic Roughness Flow Control on NACA 0012 Airfoil at Low Reynolds Number," SAE Technical Paper 2013-01-2096, 2013, doi:10.4271/2013-01-2096.
There is an ever growing need in the aircraft industry to increase the performance of a flight vehicle. To enhance performance of the flight vehicle one active area of research effort has been focused on the control of the boundary layer by both active and passive means. An effective flow control mechanism can improve the performance of a flight vehicle by eliminating boundary layer separation at the leading edge (as long as the energy required to drive the mechanism is not greater than the savings). In this paper the effectiveness of a novel active flow control technique known as dynamic roughness (DR) to eliminate flow separation in a stalled NACA 0012 wing has been explored. As opposed to static roughness, dynamic roughness utilizes small time-dependent deforming elements or humps with amplitudes that are on the order of the local boundary layer height to energize the local boundary layer. DR is primarily characterized by the maximum amplitude and operating frequency. A flow visualization study was conducted on a NACA 0012 wing at an angle of attack of 13° and Reynolds numbers of 25,000 and 50,000 at fixed maximum DR amplitude and varying frequencies. The study suggests that DR is an effective method of reattaching a totally separated boundary layer. For our flow we discovered that a threshold frequency exists for DR to be effective.