CFD Analysis of Space Shuttle Launch Vehicle During Ascent Phase

Abstract

A computational work is done to study the formation of shock wave over space shuttle launch vehicle in ascent phase. In ascent phase, the flow accelerates from subsonic to supersonic during which shock formation occur leading to sudden change in flow properties e.g., pressure, Mach number, and Density. An attempt is made to work with unstructured mesh using prism layer for space shuttle launch vehicle in software ICEM-CFD and T-Grid (version 14.5). The prism layer is generated considering y+=3 to capture the boundary layer formation near the wall accurately. The study is carried out for a flight Reynolds number of Re=283X 106 with orbiter length as the reference length. The analysis is performed at different Mach number (M= 0.9, 1.05, 1.25, 1.5) and varying the flight angle of attack (α= -3, 0, 3, 6) using CFDExpert-Lite Solver. The main emphasis is on the influence of Mach number and angle of attack on the intensity of shock wave generated on the surface of Space shuttle launch vehicle. Pressure, density and velocity profiles are displayed to show the jump in these parameters where the shocks are generated. Effect of shock waves on the flow parameters such as pressure coefficient, lift coefficient and drag coefficient are established. From the study, the formation of shockwave and expansion fan at the head of the orbiter is seen at M-1.05 which results in increase in drag coefficient. As the Mach number increases the flow get adjusted to the shockwave which again reduces the drag coefficient. There is 29.41% increase in drag coefficient for M-1.05 compared to the drag coefficient for M-0.9. And 16.4% decrement in drag coefficient is seen as the Mach number increases to 1.25. For negative angle of attack, the shockwave affects the upper surface more as compared to the lower surface. Hence the shockwave is inclined towards the upper surface. While for positive angle of attack, the influence is seen on the upper surface. As the angle of attack increases the inclination of the shock toward the upper surface is increased. The lift coefficient shows the contrasting behavior. For -3°, 0° the lift increases for M-1.05 and then decreases. This increment can be explained by the vortex generated at the wing tips. There is less effect of shockwave for M-1.05 but as the Mach number increases the intensity of vortices increases creating disturbance in the flow and hence the lift coefficient decrease. After further increase in Mach number, there is not a significant change in lift coefficient.