Numerical investigation on acoustic coupling of transverse waves in two-dimensional H₂-C₂-diluent detonations

Two-dimensional computations of stoichiometric hydrogen-oxygen detonations diluted with nitrogen/argon were performed using a detailed chemical reaction mechanism at initial pressures 0.101 and 0.013 MPa. With increasing channel widths, the relation between the channel widths normalized by half-reaction lengths and the transverse wave strengths defined by pressure ratio across a reflected shock are examined. Various mixture conditions are compared for the maximum channel width where a single transverse wave appears,' because numerical cell widths and aspect ratios of the cell are in comparative agreement with previous experimental data. In a mixture diluted with nitrogen at 0.101 MPa, the strong transverse detonation with a transverse wave strength of 1.5 overdrives the transverse wave at 1.3 times faster velocities than the speed of sound in detonation products and makes the maximum channel width larger than those of other conditions. In the presence of strong transverse detonation, acoustic coupling between the transverse wave and the acoustic wave does not apply. The empirical irregularity of the cell with the mixture diluted by nitrogen is interpreted as flexibility of the cell width due to the strong transverse detonation and instability due to out-of-phasc acoustic coupling.