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Conceptual Designing and Numerical Modeling of Micro Pulse Jet for Controlling Flow Separation

Author(s): Zakir Mahfooz, Mohsin Khalil Ahmed, Huang Guoping

Journal: International Journal of Engineering
ISSN 1985-2312

Volume: 5;
Issue: 1;
Start page: 41;
Date: 2011;
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Keywords: Vortex Formation | Mixing Enhancement | Flow Separation | Pulse Frequency | Pressure Ratio | Pitch Angle | Mass Flow Rate | Unsteady and Steady jet | Periodic Behavior

A conceptual design and numerical model of Micro Pulse Jet has been developed to investigatethe flow separation. This valve is designed to generate the stream line vortices to suppress theflow separation by enhancing the mixing of the flows between free stream and separated flow ofthe boundary layer through pitched jet orifice of very small width. This paper describes not onlythe conceptual modeling of Micro Pulse Jet but also presenting the numerical analysis and resultsof steady and unsteady pulse of micro jet. The unsteady pulse of the valve is simulated by theperiodic inlet boundary condition through a mathematical model. A 2-D ramp with 20 degreesdivergence is selected. The divergence of the lower wall of the ramp is large enough to produce astrong adverse pressure gradient causing the boundary layer to separate. A jet orifice isintroduced at the upstream of the divergent portion of the ramp and the effect of steady andunsteady jet is analyzed. The main inlet boundary condition is almost of 0.2 Mach. The jetamplitude is characterized by the velocity ratio (Vj/V∞) in between 0 to 5 and the jet pulsefrequency is varying between 0 to 100 Hz. A comparison between the steady and unsteady MicroPulse Jet is also done, which indicates the mass flow requirement for pulse micro jet is reducedsignificantly as compare to the steady jet for the flow separation control.
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