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INVESTIGATION OF LOW-HIGH SPEED COMPRESSIBLE FLOW OVER A ROUND CAVITY

K. Muraleedharan Nair
Department of Mechanical Engineering, Mar Baselios College of Engineering and Technology, Kerala, India

S. Vishnu Prasad
Mar Baselios College of Engineering and Technology; Mechanical Engineering, College of Engineering Trivandrum, Kerala, India

G. Balu
Mar Baselios College of Engineering and Technology

Krishna V. Gopal
Mar Baselios College of Engineering and Technology

DOI: 10.1615/IHMTC-2017.1550
pages 1111-1116

Abstract

The study on flow over cavities is very much significant, due to its real-world applications and simplicity in geometry. Cavities can find application in Aerospace and Automobile engineering such as sunroof and windows of cars, weapon bays, landing gears, flame holders in supersonic jets, open cockpit aircrafts, escape hatches, reconnaissance etc. Cavity flows are delineated by complex mechanisms. The sudden change in geometry at the fore wall of the cavity induces a high velocity gradient between the free stream flow and flow within the cavity, leading to the parting of the approaching flow. The disturbances at the leading edge are amplified by K-H instability, the generated small-scale structures at the shear layer convected towards the aft wall and impinge on the aft wall edge producing pressure waves. Variation in static pressure distribution inside the cavity results in large pressure gradients, and the unsteady flow disturbances causes self-sustaining oscillations which in turn generate acoustic tones that radiate from the cavity. These unsteady flows induce structural vibration which causes difficulties for store separation from an internal weapons bay. To ensure safe carriage and separation for subsonic and supersonic speeds, the flow fields that develop in cavities must be thoroughly characterized. In the present work flow past a round cavity of aspect ratio 2 has been studied to analyse self-sustaining oscillations for a subsonic and supersonic flows of Mach number 0.6 and 1.5 respectively. The simulations were done in ANSYS FLUENT PACKAGE. Compared with subsonic cavity flows supersonic cavity flows shows compression waves in the free stream and within the cavity. The present work demonstrates compressive wave-shear layer coupling, interaction of counter rotating vortices, generation of Mach waves etc. The generation of sound pressure level and its propagation for subsonic and supersonic flow are also resolved.

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