Flow control effects on length scales over a turret

Turbulence has an adverse effect on aero-optic applications when present in separated and inviscid flows, boundary and shear layers. A study of the flow physics around a cylindrical turret with the application of open-loop control has been performed. The evaluation of flow control performance is accomplished by analyzing the changes in the turbulent flow time/length scales across the turret surface for three cases: baseline, modulated sine wave and pure sine wave. Simultaneous velocity and unsteady pressure measurements were acquired at a Reynolds number of 300,000 based on turret's diameter. Turbulence intensity results present reduction of 20% on the u′ for the actuated cases. Results of the autocorrelations of the unsteady pressure sensors exhibit a more organized, almost periodic behavior. Flow control demonstrates the ability to organize the flow structures moving the flow towards homogeneity. Even when the measurements performed are not direct measures of the aero-optics, literature suggest that there is a strong relationship between them and the optical quality of the flow. Results are encouraging from the adaptive optics point of view. The flow control is able to "organize" the structures in the shear layer and possibly simplify the application of adaptive optics.