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We present a new scheme for modeling rotational energy exchange with the direct simulation Monte Carlo (DSMC) method. The new scheme is fundamentally different from conventional Borgnakke-Larsen (BL) procedures, in which energy exchange is performed at the time of collision. In the new scheme, all collisions are performed elastically. Rotational energy exchanged is performed after the collision routine, in an independent step. The rotational energy of all particles in each cell is adjusted by a factor, to satisfy the desired macroscopic relaxation behavior. To conserve total energy in a cell, the thermal velocities of all particles in the cell are adjusted. DSMC calculations of shock structure show that the new scheme gives results in reasonable agreement with those provided by conventional BL procedures. The new scheme has a potential...
In conventional 2D or 3D continuum solvers, the fluxes are `direction decoupled'; 1D flux calculations are performed in the direction normal to the cell interfaces, and fluxes are exchanged only between cells which share a cell interface. On a 2D structured grid, for example, the fluxes flow in two coordinate directions and never flow in one time step between cells which are diagonally contiguous but do not have a common interface. Cook [37th American Institute of Aeronautics and Astronautics Aerospace Sciences Meeting and Exhibit, 1998] shows that direction decoupled methods may produce unphysical results such as negative temperatures or densities where strong shocks occur or interact. Pullin [J. Comput. Phys. v34, p231, 1980] proposed the Equilibrium Flux Method (EFM) in which the molecular fluxes in a 1D flow were computed analytica...
The macroscopic chemistry method [Lilley and Macrossan, Phys. Fluids, v16, p2054, 2004] was developed to model non-equilibrium chemically reacting flows with the direct simulation Monte Carlo (DSMC) method. The macroscopic method uses kinetic temperatures, calculated from mean particle energies, to calculate reaction rates. For strongly non-equilibrium flows, it is possible the macroscopic method might ignore reactions that should result from high-energy collisions that occur in the high-energy tail of the collision energy distribution. This could result in a "rate-reducing" effect relative to conventional collision-based DSMC chemistry models that perform reactions based on the energy of each individual collision. This effect would be most pronounced for reactions with low activation energy. We test for this possible rate-reducing eff...
In this contribution, we discuss a total cross-section model which can be applied to both photon and purely hadronic processes. We find that the model can reproduce photo-production cross-sections, as well as extrapolation of gamma*p processes to gamma p using Vector Meson Dominance models, with minimal modifications from the proton case.
In this contribution, we discuss a total cross-section model which can be applied to both photon and purely hadronic processes. We find that the model can reproduce photo-production cross-sections, as well as extrapolation of gamma*p processes to gamma p using Vector Meson Dominance models, with minimal modifications from the proton case.
http://tartu.ester.ee/record=b2448841~S1*est
http://tartu.ester.ee/record=b2448840~S1*est
Comment: 27 pages. arXiv admin note: substantial text overlap with arXiv:math/0607358
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