Large eddy simulations of compressible MHD turbulence
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概要
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Large eddy simulation method is developed for study of decaying and forced compressible magnetohydrodynamic turbulence. The obtained results of numerical computations for large eddy simulation are compared with the results of direct numerical simulation of three-dimensional compressible magnetohydrodynamic turbulence under various similarity parameters, namely, magnetic Reynolds numbers,hydrodynamic Reynolds numbers and Mach numbers for polytropic case. The comparison of five subgrid-scale closures of large eddy simulation for magnetohydrodynamic case is made: the Smagorinsky model, the Kolmogorov model, the cross-helicity model, the scale-similarity model and mixed model. The comparison between large eddy simulation and direct numerical simulation is carried out regarding the time evolution of kinetic and magnetic energy, cross helicity, subgrid-scale and molecular dissipations for kinetic and magnetic energy, turbulent intensities and quantities that describe anisotropy of flow, that is, skewness and kurtosis of velocity and magnetic field. It is shown that some proposed subgrid-scale models provide sufficient dissipation of kinetic and magnetic energy, reduce computational efforts and produce adequate results of magnetohydrodynamic turbulent modeling for various values of similarity parameters of flows. We also consider a heat conducting compressible fluid with the use of an energy equation. Application of large eddy simulation approach to heat conducting compressible magnetohydrodynamics is considered. It is shown that novel subgrid-scale terms arise in Favre-filtered equations due to the presence of a magnetic field in the total energy equation. Parameterizations of these extra terms are developed. Computations at various Mach numbers are made for decaying compressible magnetohydrodynamic turbulence. The obtained numerical large eddy simulation results are analyzed on the basis of comparison with results of numerical experiments performed by direct numerical simulation. We present the large-eddy simulation method for studying forced compressible magnetohydrodynamic turbulence as well. The proposed method is based on a linear representation of the driving forces in the momentum conservation equation and the magnetic induction equation. These forces supply the production of kinetic and magnetic energy. The emphasis is placed upon the important, and not investigated, question about the ability of the large-eddy simulation approach to reproduce Kolmogorov and Iroshnikov-Kraichnan scale-invariant spectra in compressible magnetohydrodynamic flows.
- 日本学術会議 「機械工学委員会・土木工学・建築学委員会合同IUTAM分科会」の論文
日本学術会議 「機械工学委員会・土木工学・建築学委員会合同IUTAM分科会」 | 論文
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