Numerical Investigation on the Effect of Vortex Generator on the Transonic Flow Field of a Hemispherical Turret
The airborne laser platform is severely challenged by aero-optical problems led by the transonic flow around its turret.Aiming to essentially study transonic flow features around a turret with a passive flow control method,an Improved Delayed Detached Eddy Simulation(IDDES)approach with modified subgrid scales was employed to conduct a numerical investigation on flow control of a hemispherical airborne laser turret under the transonic condition,using a thin cylindrical vortex generator.The results show that the vortex generator introduced a distinct secondary flow features,attenuating the incoming flow energy.This led to a noticeable impact on the shock intensity at the top of the turret,subsequently affecting the size of the separation bubble in the turret's wake region.While the lateral oscillation and vertical fluctuation features of the turret's wake showed no significant alterations due to the vortex generator,Dynamic Mode Decomposition(DMD)results highlighted a pronounced decay in the energy of the longitudinal fluctuation modes when the vortex generator was present.This observation matched well with the morphological changes in the wake separation bubble,revealed the effectiveness of current vortex generator to suppress the separation in the turret wake region and provided a basis for using passive control methods to suppress aero-optical problems of turrets.
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