Bulletin of the American Physical Society
61st Annual Meeting of the APS Division of Fluid Dynamics
Volume 53, Number 15
Sunday–Tuesday, November 23–25, 2008; San Antonio, Texas
Session HW: Mini-Symposium: Computational Challenges in Modeling Transient Detonation |
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Chair: David Kassoy, University of Colorado Room: 004 |
Monday, November 24, 2008 10:30AM - 10:56AM |
HW.00001: Simulation of multidimensional gaseous detonations with a parallel adaptive method Invited Speaker: A detonation wave is a self-sustained, violent form of shock-induced combustion that is characterized by a subtle energetic interplay between leading hydrodynamic shock wave and following chemical reaction. Multidimensional gaseous detonations never remain planar and instead exhibit transverse shocks that form triple points with transient Mach reflection patterns. Their accurate numerical simulation requires a very high resolution around shock and reaction zone. A parallel adaptive finite volume method for the chemically reactive Euler equations for mixtures of thermally perfect gases has been developed for this purpose. Its key components are a high-resolution shock-capturing scheme of Roe-type, block-structured Cartesian mesh adaptation, and operator splitting to handle stiff, detailed kinetics. Beside simple verification examples to quantify the savings in wall time from mesh adaptation and parallelization, large-scale computations of Chapman-Jouguet detonations in low-pressure hydrogen-oxygen-argon mixtures will be discussed. These computations allowed the detailed analysis of triple point structures under transient conditions and a comparison between two and three space dimensions. [Preview Abstract] |
Monday, November 24, 2008 10:56AM - 11:22AM |
HW.00002: Numerical Modeling of Multi-dimensional Acoustic Timescale Detonation Initiation Invited Speaker: In this talk we discuss the issues related to modeling and simulation of acoustic timescale detonation initiation. Momentary, partial inertial confinement resulting from localized heat addition on time scales comparable with the local acoustic time causes a high pressure and temperature reaction center. Subsequent gasdynamic processes including wave reflections lead to the spontaneous appearance of numerous additional reaction centers that promote the development of an overdriven detonation. One of the main difficulties encountered when numerically modeling detonation initiation through localized thermal energy deposition is coping with the numerous spatial and temporal scales involved. The reaction and energy deposition zones are quite small in comparison to the entire detonation tube and the energy is deposited on sub-acoustic timescales. The multiplicity of scales makes it challenging to accurately model the initiation process in a truly multi-dimensional sense. In order to deal with these challenges, we use the Adaptive Wavelet Collocation Method with shock capturing capabilities, which ensures adequate resolution of the transient dynamics leading to detonation initiation. The details of the method are discussed and the results of two-dimensional simulations in a channel initiated by thermal power deposition into a small circular region are presented. In collaboration with David R. Kassoy and Jonathan D. Regele, University of Colorado at Boulder. [Preview Abstract] |
Monday, November 24, 2008 11:22AM - 11:48AM |
HW.00003: Shock Fitting Algorithms in Advanced Detonation Shock Dynamics Simulations Invited Speaker: A general formulation for shock fitting will be presented in regards to applications in detonation modeling. Solutions, where applicable, will be compared to traditional high resolution schemes. It will be shown that shock fitting can lead to a computational savings of several orders of magnitude for practical problems, when compared to shock capturing. Furthermore, for certain applications of higher-order Detonation Shock Dynamics modeling, shock fitting is a prerequisite. [Preview Abstract] |
Monday, November 24, 2008 11:48AM - 12:14PM |
HW.00004: Accurate Simulation of Multi-Dimensional Detonation Waves in a Shock-Attached Frame Invited Speaker: Numerical simulation of detonation waves is a challenging problem due to resolution requirements necessary to compute highly nonlinear multiple-scale dynamics of the shock--reaction zone structure. Widely used shock-capturing techniques are often inadequate when dealing with unstable detonations. Large errors at the lead shock propagate into the reaction zone, amplify, and can dominate the true dynamics of the detonation instability. In order to eliminate the shock-capturing errors at the lead shock, we propose a shock fitting algorithm that is based on numerical integration of the reactive Euler equations in the frame attached to the lead shock. A local system of hyperbolic partial differential equations on the shock coupled to the Euler equations inside the reaction zone is derived and used as part of a numerical algorithm. With high-order time- and space discretizations, we compute the growth of linear instability into non-linear cellular detonation waves. For the first time, we performed detailed verification of the results of detonation stability theory in two dimensions. Our approach is ideally suited for testing detonation stability theories as well as nonlinear asymptotic theories such as detonation shock dynamics. [Preview Abstract] |
Monday, November 24, 2008 12:14PM - 12:40PM |
HW.00005: An adaptive method for a model of two-phase reactive flow on overlapping grids Invited Speaker: A two-phase model of heterogeneous explosives is handled computationally by a new numerical approach that is a modification of the standard Godunov scheme. The approach generates well-resolved and accurate solutions using adaptive mesh refinement on overlapping grids, and treats rationally the nozzling terms that render the otherwise hyperbolic model incapable of a conservative representation. The evolution and structure of detonation waves for a variety of one and two-dimensional configurations will be discussed with a focus given to problems of detonation diffraction and failure. [Preview Abstract] |
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