No abstract

To improve the quality of driving ows generated with detonation-driven shock tunnels operated in the forwardrunning mode, various detonation drivers with specially designed sections were examined. Four con gurations of the specially designed section, three with different converging angles and one with a cavity ring, were simulated by solving the Euler equations implemented with a pseudo kinetic reaction model. From the rst three cases, it is observed that the re ection of detonation fronts at the converging wall results in an upstream-traveling shock wave that can increase the ow pressure that has decreased due to expansion waves, which leads to improvement of the driving ow. The con guration with a cavity ring is found to be more promising because the upstream-traveling shock wave appears stronger and the detonation front is less overdriven. Although pressure uctuations due to shock wave focusing and shock wave re ection are observable in these detonation-drivers, they attenuate very rapidly to an acceptable level as the detonation wave propagates downstream. Based on the numerical observations, a new detonation-driven shock tunnel with a cavity ring is designed and installed for experimental investigation. Experimental results con rm the conclusion drawn from numerical simulations. The generated driving ow in this shock tunnel could maintain uniformity for as long as 4 ms. Feasibility of the proposed detonation driver for high-enthalpy shock tunnels is well demonstrated. NomenclatureD CJ = Chapman-Jouguet (C-J) detonation velocity e = total energy per mass= molecular weight of the reactant m 2 = molecular weight of the product P CJ = C-J detonation pressure P i = initial pressure in driver section P ignit = ignition pressure P 0 = initial pressure in driven section p = pressure Q = reaction heat per mass S, H = source terms= mass fraction of the reactant Z 2 = mass fraction of the product ®,¯, Adet = tuned constants of reaction model°= effective adiabatic exponent°1 = adiabatic exponent of the reactant°2 = adiabatic exponent of the product 1s = local mesh size

To improve the quality of driving ows generated with detonation-driven shock tunnels operated in the forwardrunning mode, various detonation drivers with specially designed sections were examined. Four con gurations of the specially designed section, three with different converging angles and one with a cavity ring, were simulated by solving the Euler equations implemented with a pseudo kinetic reaction model. From the rst three cases, it is observed that the re ection of detonation fronts at the converging wall results in an upstream-traveling shock wave that can increase the ow pressure that has decreased due to expansion waves, which leads to improvement of the driving ow. The con guration with a cavity ring is found to be more promising because the upstream-traveling shock wave appears stronger and the detonation front is less overdriven. Although pressure uctuations due to shock wave focusing and shock wave re ection are observable in these detonation-drivers, they attenuate very rapidly to an acceptable level as the detonation wave propagates downstream. Based on the numerical observations, a new detonation-driven shock tunnel with a cavity ring is designed and installed for experimental investigation. Experimental results con rm the conclusion drawn from numerical simulations. The generated driving ow in this shock tunnel could maintain uniformity for as long as 4 ms. Feasibility of the proposed detonation driver for high-enthalpy shock tunnels is well demonstrated. NomenclatureD CJ = Chapman-Jouguet (C-J) detonation velocity e = total energy per mass= molecular weight of the reactant m 2 = molecular weight of the product P CJ = C-J detonation pressure P i = initial pressure in driver section P ignit = ignition pressure P 0 = initial pressure in driven section p = pressure Q = reaction heat per mass S, H = source terms= mass fraction of the reactant Z 2 = mass fraction of the product ®,¯, Adet = tuned constants of reaction model°= effective adiabatic exponent°1 = adiabatic exponent of the reactant°2 = adiabatic exponent of the product 1s = local mesh size

This study explored inviscid supersonic corner flows induced by three-dimensional symmetrical intersecting compression wedges by introducing the spatial dimension reduction theoretical approach to transform the threedimensional steady shock/shock interaction problem into a two-dimensional pseudosteady problem; this method allows not only wave configurations, which include regular reflection and Mach reflection, to be determined accurately, but also flowfield characteristics, which include density, temperature, pressure, and total pressure recovery coefficient near the regular reflection point (or in the vicinity of the Mach reflection triple point), as well as the location and the strength of the Mach stem. Theoretical results were compared to numerical simulation (performed by solving three-dimensional inviscid Euler equations with an non-oscillatory and non-free-parameters dissipative finite difference scheme) and analyzed thoroughly. The effects of inflow Mach number, sweep angle, and wedge angle on flowfield parameters and wave configurations were also considered. The influence of sweep angle is negligible, but the effects of Mach number and wedge angle are significant.

Abstract. An investigation into the three-dimensional propagation of the transmitted shock wave in a square cross-section chamber was described in this paper, and the work was carried out numerically by solving the Euler equations with a dispersion-controlled scheme. Computational images were constructed from the density distribution of the transmitted shock wave discharging from the open end of the square shock tube and compared directly with holographic interferograms available for CFD validation. Two cases of the transmitted shock wave propagating at different Mach numbers in the same geometry were simulated. A special shock reflection system near the corner of the square cross-section chamber was observed, consisting of four shock waves: the transmitted shock wave, two reflection shock waves and a Mach stem. A contact surface may appear in the four-shock system when the transmitted shock wave becomes stronger. Both the secondary shock wave and the primary vortex loop are three-dimensional in the present case due to the non-uniform flow expansion behind the transmitted shock.