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K. Vaagsaether; V. Knudson; D. Bjerketvedt

Flame acceleration and deflagration to detonation transition (DDT) is simulated with a numerical codebased on a flux limiter centered method for hyperbolic differential equations [1]. The energy source term iscalculated by a Riemann solver for the inhomogeneous Euler equations for the turbulent combustion and atwo-step reaction model for hydrogen-air. The transport equations are filtered for large eddy simulation(LES) and the sub-filter turbulence is modelled by a transport equation for the the turbulent kinetic energy[2]. The flame tracking is handled by the G-equation for turbulent flames [3]. Numerical results arecompared to pressure histories from physical experiments. These experiments are performed in a closed,circular, 4 m long tube with inner diameter of 0.107 m. The tube is filled with hydrogen-air mixture at 1 atm,which is at rest when ignited. The ignition is located at one end of the tube. The tube is fitted with anobstruction with circular opening 1 m down the tube from the ignition point. The obstruction has a blockageratio of 0.92 and a thickness of 0.01 m. The obstruction creates high pressures in the ignition end of the tubeand very high gas velocities in and behind the obstruction opening. The flame experiences a detonation todeflagration transition (DDT) in the supersonic jet created by the obstruction. Pressure build-up in theignition end of the tube is simulated with some discrepancies. The DDT in the supersonic jet is simulated,but the position of the DDT is strongly dependent on the simulated pressure in the ignition end.

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