Static Cylinder as a Base Pressure Controller in Supersonic Regime

An experimental examination of the efficiency of a static cylinder to reduce base drag for over-expanded, perfectly-expanded, and under-expanded supersonic jets at Mach 2 is presented. As a passive control device, a 2 mm diameter static cylinder is positioned 2 mm from the square duct sidewall and 8 mm from the converging-diverging square nozzle exit in the base region. Base pressures in the wake flow were measured after a quick expansion of jets into a square nozzle. The duct has a length-to-width ratio of 10. The jets were run at various nozzle pressure ratios ranging from 2 to 9. In all cases, the flow field in the square duct was also observed. The static cylinder, when used as a passive controller, reduced base drag by up to 59 percent at NPR = 9 and 14 percent at NPR = 6. Mach number, area ratio, length to width ratio, and nozzle pressure ratio all influence the base pressure. The static control is ineffective until NPR is 6, when the flow from the nozzle is over inflated. The degree of expansion is critical. For the most part, the flow flux in the square duct remains nearly same with and without control. However, for higher NPRs, such as 6, 7.8, and 9, the control causes both an increase and a drop in the duct’s wall pressure. For higher NPRs, passive management of the base flow is beneficial. The shock waves dominate the flow field with higher NPR. A shadowgraph is also used to depict this phenomenon.

Author(s) Details

Mohammed Asadullah
Department of Mechanical Engineering, Lords Institute of Engineering & Technology, Hyderabad, India.

S. A. Khan
Department of Mechanical Engineering, International Islamic University Malaysia, Kuala Lumpur, Malaysia.

Waqar Asrar
Department of Mechanical Engineering, International Islamic University Malaysia, Kuala Lumpur, Malaysia.

E. Sulaeman
Department of Mechanical Engineering, International Islamic University Malaysia, Kuala Lumpur, Malaysia.

Syed Azam Pasha Quadri
Department of Mechanical Engineering, Lords Institute of Engineering & Technology, Hyderabad, India.

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