Numerical Simulations of Gaseous Detonations

Diffraction of a Detonation Wave, H2:O2:Ar / 2:1:7, T0=298 K, p0=10.0 kPa

Like in the pervious section, a regular oscillating two-dimensional solution of a H2:O2:Ar Chapman-Jouguet detonation with molar ratios 2:1:7 at T0=298 K and p0=10.0 kPa is calculated in advance and reproduced periodically as a reasonabe model for the flow situation in a larger detonation tube. It is know experimentally that diffusors with rectangular cross-section allow the successful transmission of a detonation wave only for tube widths greater than 10 detonation cells. For widths significantly below 10 detonation cells the hydrodynamic process of shock wave diffraction causes a weakening of the shock ahead of the detonation below the limit of detonability across the entire tube width. In this case, shock and reaction decouple and the reaction front remains behind as a deflagration wave.

Godunov-splitting is used for the incorporation of the source term and for the dimensional extension of a hybrid Roe-HLL scheme with MUSCL reconstruction. Automatic time step adjustment for CCFL = 0.95, Van Albada-limiter, 25.5 Pts/L1/2. Dynamic adaptive mesh refinement with AMROC with four additional refinement levels (refinement factors 2,2,2,4). Computational time for each runs was about 4600 h CPU time on Athlon 1.4GHz.

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last update: 06/10/03