An adaptive mesh refinement technique is used to calculate the focussing process of shock waves in a reactive mixture. The fluid flow is described by the reactive Euler equations in two dimensions, which are integrated in time using an operator splitting technique. The convective part is integrated by the Harten-YeeTVD method, and the integration of chemical source terms is performed by CHEMEQ, an explicid Euler method. A one-sep reaction mechanism is used to model the chemistry of a stoichiometryic H_2/O_2-mixture. Calculations are performed for shock Mach numbers of 1.6 and 1.9. At lower shock strenght, the complex interaction of different shock and expansion waves during the focussing process dominate the wave field and chemistry is not significnat. The computed results show the same wave patterns as obtaiend by experiments for a similar set-up. In case of the higher Mach number of 1.9 the calculations lead to the ignition of a spherical detonation wave in the focal region which interacts with the diffracted shock wave and the reflector, resulting in an even more complex wave field.
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