Schlieren Visualization of Coflow Fluidic Thrust Vectoring Using Sweeping Jets

Abstract

Reducing the consumption of secondary flow is of significance to future development of fluidic thrust vectoring (FTV) technology. A new coflow FTV control method based on sweeping jet (SWJ) excitation is proposed for the deflection of primary jets, and its performance is comparatively examined against conventional steady jet (SJ) excitation. Schlieren visualization using a high-speed camera is applied to provide insights into the flowfields. The results show that at the same mass flow rate of the secondary coflow injection and for Mach numbers of primary flow up to 0.35 SWJ excitation achieves a larger primary flow deflection angle than the SJ excitation does. To examine the flow control mechanisms, clear flow structures are extracted from noisy images by using robust principal component analysis. Moreover, dynamic mode decomposition is applied to investigate the flow dynamics of the primary flow. The SWJ is found to be more capable of enhancing the flow mixing than the SJ is. Furthermore, the SWJ ensures that the primary jet attaches to the nozzle surface and produces a larger deflection angle, which leads to the higher efficiency in coflow vectoring control.