About the Effect on the Airfoil Wake Induced by Periodic Mobile Flap

Abstract

The flow in the wake of an aerodynamic airfoil gives us information about the flow pattern that generates the aerodynamic forces. This wake will depend not only on the geometry of the model, but also on the characteristics of the incident flow. If the airfoil has a flow control system, it can modify the characteristics of the resulting flow field. The wake turbulence in this case will be modified. In the near wake, it will be possible to study the mechanisms of generation and vortex shedding, while the analysis of the distant wake provides us with information on the general fluid-dynamic field resulting from the aero-dynamic forces. The objective of the present work is to study the develop of the fluid-dynamic structures found in the NACA 4412 airfoil wake, as well as the development of the same structures when flow control techniques are applied by means of an oscillating Gurney Flap place in the lower surface of the wing model, close to the trailing edge. The flow control system was set at different frequencies. In order to study the effect of the control mechanism on the wake, hot wire anemometry techniques were used. Two components of the velocity vector were measured - longitudinal and vertical by means of a vertical array of three sensors acquiring simultaneously. Velocity fluctuations will be analyzed, as well as turbulence intensities, integral scales and flow energy, in order to quantify the turbulent wake generated and understand the mechanisms involved in its generation.