Numerical investigation of environmental parameters on dynamic stability of a reentry capsule

Dynamic instability and control of reentry capsules is one of interesting issues for researcher because of its complex flow structure and interaction of very parameters effects in unsteady flow. One of the main problems for reentry capsules is their dynamic instability in some velocities and environmental conditions. Thus, determination of dynamic stability criteria of this kind of capsules is one of key parameters of its design. In this paper firstly, 3D numerical simulation of unsteady flow is performed around a reentry capsule in forced pitching oscillation using slip mesh technique. After validation of the results and study of grid independency, effects of environmental parameters including the angle of attack, Mach number and frequency on the capsule dynamic stability are determined. For this aim, the results are captured by Fluent software and flow structure around the capsule are studied at different conditions. The longitude dynamic derivatives, which are needed for stability analyzing of a body in pitching oscillation, are calculated. Finally, effect of mentioned parameters on value of dynamic derivative is investigated. In the present study, variation range for the mean angle of attack is between 0 to 15 degree, for the Mach number is between 0.8 to 2 and for the frequency is between 10 to 40 hertz. Using the sliding mesh in simulation of pitching oscillation of the Muses-C capsule which decreases computational cost, study of multi-parameter on dynamic stability of this capsule and investigation of variation trend of dynamic stability in different conditions are some goles of this paper. Results of analysis of various parameters influence indicate that increasing of mean angle of attack from zero angle enhances dynamic stability. Furthermore, dynamic instability of the capsule is more critical at subsonic flow rather than supersonic flow. In addition, dynamic stability of Muses-C capsule increases by rising of oscillation frequency.