Abstract:
Supersonic cruise, low acoustic signature, wave drag and heating are an integral part of
any supersonic flight. In order to quickly pass through transonic regime and sustain in
supersonic dash, the aircraft have to overcome wave drag. Efforts in the form of sleek
aerodynamic designs and better propulsion systems are generally adopted to achieve
these goals. The main motivation of this research is to explore the utilization of opposing
jet, an active flow control technique, to tailor the shock wave characteristics in supersonic
regime.
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 (URANS) based solver is used
to model the flow field. k - ! SST turbulence model is used for the numerical analysis
with block meshing techniques for the generation of mesh domain.
The effect of angle of attack ( ), free-stream Mach number (M1), and pressure ratio
(PR) on aerodynamic performance of airfoil with and without jet are compared. This
research also contain the detailed analysis of influence of jet Mach number on the performance
of airfoil. It also explain the effect of recirculation regions on the reduction of
drag and their reattachment position to the surface of airfoil (the region of triple point
for the generation of expansion waves).
The results indicate that the opposing jet reduces drag from 25% to 45% with increasing
free stream Mach numbers at constant angle of attack ( = 0o) and pressure ratio (PR
= 2.0). Increase in the pressure ratio of opposing jet causes the reduction in the drag
from the surface of airfoil (from 18% to 65%) at constant free stream Mach number
(M1 = 1.6) and angle of attack ( = 0o).
The effect of opposing jet on longitudinal flight stability characteristics are studied for
xv
the first time and indicates improvement in dynamic stability coefficients. The pitching
moment derivatives (Cmq + Cm ˙ ) of airfoil reduces by the ejection of opposing jet.
Similarly, it also increases the static lift slope and dynamic lift derivative coefficients
(Cl and Cl ˙ ) of airfoil. It is concluded that the opposing jet can help to mitigate flight
disturbances in supersonic regime.
