Separation Motion of Strap-On Boosters with Base Flow and Turbulence Effects

Abstract

A numerical investigation is conducted around a multistage launch vehicle to examine the influence of the base region and turbulence. A Reynolds-averaged Navier–Stokes flow solver coupled with rigid body dynamics, because of resultant aerodynamic forces and gravity, is developed to simulate the detachment motion of strap-on boosters. An overset mesh technique is adopted to achieve maximal efficiency in simulating the relative motion of launch vehicles, and various turbulence models are implemented to accurately predict aerodynamic forces in high Reynolds number flows. The flow solver is validated by comparing the computed pressure coefficients of the Titan-IV launch vehicle with the experimental data. In addition, some preliminary studies are conducted to examine the influence of the base flow and turbulence effect in the accurate simulation of detachment motion. Finally, the separation behavior of the KSR-III, a three-stage sounding rocket developed in Korea, is numerically investigated. It is observed that the afterbody flowfield strongly affects the separation motion of strap-on boosters. The negative pitching moment of a strap-on at the initial stage of a detachment motion is gradually recovered and the final result is a safe separation, whereas forebody-only analysis yields a collision scenario between the core rocket and the booster. Only a slight difference in vehicle trajectory is observed from the comparison between inviscid and turbulent analyses. Change of the separation trajectory due to viscous effects is just a few percentage points and, therefore, inviscid analysis seems to be sufficient for the simulation of separation motion if the study focuses on the movement of strap-ons.