To gain an insight into the complex ow structure in the base region of a projectile with a base cavity, a hypersonic cone-cylinder-are projectile has been investigated through computational means, and the results were compared with free-ight experimental results. Aerodynamic coef cients, base pressure surveys, base ow visualization, and shock patterns over the projectile were investigated for a Mach number range of 3.5-5.75. Several base cavity depths were selected to identify the effects of cavity depth on a range of aerodynamic coef cients. Correlation between experimental and numerical values seems to show the absence of a relation between the aerodynamic coef cients, such as drag, normal force, and pitching moment, and the presence of a base cavity for this particular con guration. Variations in the depth parameter of the base cavity presented similar results.
Nomenclature
C= Crocco number C M = pitching moment coef cient C M = pitching moment coef cient slope, 1/rad C M 3 = cubic pitching moment coef cient, 1/rad 3 C N = normal force coef cient slope, 1/radCartesian components of the outward normal surface vector H = total enthalpy, m 2 /s 2 h = static enthalpy of the uid, m 2 /s 2 k = turbulent kinetic energy, J l = length, m M = Mach number P = pressure, Pa q = molecular energy transport due to conduction S = additional (external) source terms s = surface integrals T = temperature, K t = time, s u = velocity component, m/s Vol = volume of the control volume = volume integrals x = axial distance, m Y = mass fraction of the species k y = viscous coordinate = molecular diffusion coef cient n j = discrete outward surface vector = dissipation of turbulent kinetic energy = conductivity of the uid (sometime symbolized as k), Wm/ C = dynamic viscosity of the uid, kg/ms = density, kg/m 3 = viscous shear stress, kg/ms 2 Subscripts b = base plane E = energy related e = edge of boundary layer i j k = indices in three transformed computational coordinates inf = freestream conditions ip = integration point ui = momentum related Superscript o = at the old time level Introduction M ANY of the actual and future con gurations of projectileshave some form of base cavity. The aerodynamic characteristics and stability parameters associated with this type of vehicle have not always been completelyunderstoodin the actual and future speed regimes. However, this type of aerodynamic information will have to be known and understood for the next generation of kinetic energy penetrators, at extreme speed regimes (Mach 4-8), before being elded with operational units.To better understandthese phenomena,the Defence Research Establishment,Valcartier (DREV), and the Defence Research Agency, Fort Halstead, have been involved in a research project to study the ight dynamic, aerodynamic, and aerothermal properties of conecylinder-are hypersonic con gurations up to Mach 7. The overall research program consists in conducting aeroballistic range testing of several con gurations to determine their aerodynamic coefcients and stability derivatives....
