Simulation of Separation Control in Axisymmetric Diffuser Flow

Large–Eddy Simulations were performed for the separated turbulent flow in an axisymmetric diffuser. An active control technique was investigated in order to decrease the size of the separation region. The technique was based on periodic perturbation using sinusoidal blowing and suction through slits on the diffuser’s circumference. The slit position and slit geometry were varied as well as the frequency and the amplitude of the control flow. The length of the separation region could be reduced by up to 37%, along with a 20% reduction of pressure loss in the diffuser. A vortex visualization technique was applied to detect changes in the turbulent structures of the flow in the axisymmetric expansion.