Shock Reduction through Opposing Jets—Aerodynamic Performance and Flight Stability Perspectives

In this research paper, investigations of counter flow (opposing) jet on the aerodynamic performance, and flight stability characteristics of an airfoil with blunt leading-edge in supersonic regime are performed. Unsteady Reynolds-Averaged Navier-Stokes (<inline-formula> <math display="inline"> <semantics> <mrow> <mi>U</mi> <mi>R</mi> <mi>A</mi> <mi>N</mi> <mi>S</mi> </mrow> </semantics> </math> </inline-formula>) based solver is used to model the flow field. The effect of angle of attack (<inline-formula> <math display="inline"> <semantics> <mi>&#945;</mi> </semantics> </math> </inline-formula>), free-stream Mach number (<inline-formula> <math display="inline"> <semantics> <msub> <mi>M</mi> <mo>&#8734;</mo> </msub> </semantics> </math> </inline-formula>), and pressure ratio (<inline-formula> <math display="inline"> <semantics> <mrow> <mi>P</mi> <mi>R</mi> </mrow> </semantics> </math> </inline-formula>) on aerodynamic performance of airfoil with and without jet are compared. The results indicate that the opposing jet reduces drag from <inline-formula> <math display="inline"> <semantics> <mrow> <mn>30</mn> <mo>%</mo> </mrow> </semantics> </math> </inline-formula> to <inline-formula> <math display="inline"> <semantics> <mrow> <mn>70</mn> <mo>%</mo> </mrow> </semantics> </math> </inline-formula>, improves the maximum lift-to-drag ratio from 2.5 to 4.0, and increases shock stand-off distance from <inline-formula> <math display="inline"> <semantics> <mrow> <mn>15</mn> <mo>%</mo> </mrow> </semantics> </math> </inline-formula> to <inline-formula> <math display="inline"> <semantics> <mrow> <mn>35</mn> <mo>%</mo> </mrow> </semantics> </math> </inline-formula> depending on flow conditions. The effect of opposing jet on longitudinal flight stability characteristics, studied for the first time, indicate improvement in dynamic stability coefficients (<inline-formula> <math display="inline"> <semantics> <msub> <mi>C</mi> <msub> <mi>m</mi> <mi>q</mi> </msub> </msub> </semantics> </math> </inline-formula> + <inline-formula> <math display="inline"> <semantics> <msub> <mi>C</mi> <msub> <mi>m</mi> <mover accent="true"> <mi>&#945;</mi> <mo>˙</mo> </mover> </msub> </msub> </semantics> </math> </inline-formula>) at low angles of attack. It is concluded that the opposing jet can help mitigate flight disturbances in supersonic regime.

Abstract licence: CC BY

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