Numerical Simulation of Transient Detonation Structures in H2-O2 Mixtures in Smooth Pipe Bends

Accidental internal detonation waves are a common threat to the pipeline systems of petrochemical or nuclear fuel processing plants. In order to quantify the failure potential of piping structures, especially at bends, accurate detonation pressure histories are required [5]. Since detonations inhibit multi-dimensional wave structures with triple points of enhanced chemical reaction, one-dimensional detonation theory is hardly applicable. Particular for low initial pressures, resulting in large cellular structures, detonation propagation through bends is rather complex. For small radius and larger bending angle, the detonation wave structure is not maintained and triple point quenching can be observed at the outer compressive side, while detonation failure and violent re-initiation occur at the inner diffractive wall (see Fig. 5a of [7] for experimental results showing detonation re-ignition in bends). In the present paper, we use highly resolved numerical simulations to study the transient structural evolution as low-pressure Chapman-Jouguet detonations in perfectly stirred stoichiometric hydrogenoxygen-argon mixtures propagate through smooth two-dimensional bends. The pipes have the constant width 8 cm and encompass initially five regular detonation cells. For an unchanged inner radius of 15 cm, we consider the bending angles 15, 30, 45, and 60. The computations employ detailed chemical kinetics and have been carried out with a massively parallel high-resolution finite volume code with temporal and spatial dynamic mesh adaptation. An overview of the solution approach is given in Sec. 2. Computational results are presented and discussed in Sec. 3.