Numerical investigation of shock-induced combustion with unsteady oscillation around hypervelocity conical projectile

Shock-Induced Combustion around hypervelocity conical projectile was numerically investigated using two-dimensional axisymmetric and three-dimensional Euler equations. For the calculation conditions used in this study, the shock wave around a conical projectile is attached in the case of nonreacting flow. Periodic oscillatory combustion and unsteady combustion around a conical body are observed in two-dimensional simulations. The twodimensional calculation results reveal that the propagation of triple point structure generates the dynamic behavior of oscillatory combustion. The oscillatory combustion for the large diameter case becomes unsteady because plural triple points are randomly formed. Parametric studies for the diameter and the induction length are conducted, and the results reveal the importance of l_cone/l^OSW _ind, showing the geometry vs. the induction effect, and l_cone/l^OSW _reac, showing the geometry vs. the exothermic effect, for the combustion regime. Threedimensional calculation is conducted to confirm the three-dimensional behavior of the combustion wave for both periodic and unsteady regimes. The calculation results indicate that the Shock-Induced Combustion around a conical body is essentially axisymmetric. The re-attachment of an oblique shock wave to the tip of the conical projectile during the unsteady oscillation is the key phase to keep the axisymmetry in this phenomenon because this process removes a disturbance on the reaction front.