WAVE FRONT CAPTURING USING DETONATION SHOCK DYNAMICS

Abstract

High fidelity fluid dynamics based combustion models for reactive media can be implemented by way of simulations but require significantly large CPU effort. The Detonation Shock Dynamics (DSD) models offer a simpler alternative. The challenge presented while implementing DSD equations is mostly computational. Accuracy, simulation time and spatial resolution considerations turn out to counteract each other and a tradeoff is necessitated. We present simulation results obtained for a single detonation point using the level set method for DSD and describe an example of such a trade-off. We demonstrate that curvature dependence and independence of detonation velocity affects this trade-off. We then address the hydro-code results using a test case with five detonation points. The times of arrival of the detonation front at certain locations (gauge points) are taken to represent the shape of the detonation front. Times of arrival obtained using hydro-code are compared with those obtained by the level set method which has been optimized for the three considerations above. The shape of the front gets similarly reproduced in both cases, but the level set method over predicts the time of arrival up to 10 percent. We conclude that more efficient computing hardware needs to employed for DSD simulations and the level set method would serve as a quicker means for preliminary checks of detonation point arrangements. We also suggest a method for accommodating time delays at detonation points. The initial scalar field is assumed to be a combination of Gaussian functions centered at the detonation points. This is taken to represent the detonation at certain lead time which is accommodated for in the algorithm. This lead time is reduced if any delay is to be accommodated. The above method for accommodating time delay has a limitation. The initial radius cannot be made smaller that the radius set by the standard decay constant of the initial Gaussian profiles of the scalar field. The accommodated delay cannot be longer than this radius divided by detonation speed to be employed. We offer a work-around involving a construction of suitably located secondary detonation points.