• Proceedings of the KSME Conference
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• 2002.08a
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• pp.169-172
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• 2002

When a plane shockwave reflects ken a concave wall, it is focused at a certain location, resulting in extremely high local pressure and temperature. This focusing is due to a nonlinear phenomenon of shock wave. The focusing phenomenon has been extensively applied to many diverse folds of engineering and medical treatment as well. In the current study, the focusing of shock wave over a reflector is numerically investigated using a CFD method. The Harten-Yee total variation diminishing (TVD) scheme is used to solve the unsteady, two-dimensional, compressible, Euler equations. The incident shock wave Mach number $M_{s}\;of\;1.1{\~}l.3$ is applied to the parabolic reflectors with several different depths. Detailed focusing characteristics of the shock wave are investigated in terms of peak pressure, gasdynamic and geometrical foci. The results obtained are compared with the previous experimental results. The results obtained show that the peak pressure of shock wave focusing and its location strongly depend on the magnitude of the incident shock wave and depth of parabolic reflector. It is also found that depending up on the depth of parabolic reflector, the weak shock wave focusing process can classified into three distinct patterns : the reflected shock waves do not intersect each other before and after focusing, the reflected shock waves do not intersect each other before focusing, but intersect after focusing, and the reflected shock waves intersect each other before and after focusing. The predicted Schlieren images represent the measured shock wave focusing with a good accuracy.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.70.2-70.2
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• 2014

We developed a three-dimensional (3D) magnetohydrodynamic (MHD) simulation code to reproduce the structure of a solar wind and the propagation of a coronal mass ejection (CME) through it. This code is constructed by a finite volume method based on a total variation diminishing (TVD) scheme using an unstructured grid system (Tanaka 1994). The grid system can avoid the singularity arising in the spherical coordinate system. In this study, we made an improvement of the code focused on the propagation of a CME through a solar wind, which extends a previous work done by Nakamizo et al. (2009). We first reconstructed a solar wind in a steady state from physical values obtained at 50 solar radii away from the Sun via an MHD tomography applied to interplanetary scintillation (IPS) data (Hayashi et al. 2003). We selected CR2057 and inserted a spheromak-type CME (Kataoka et al. 2009) into a reconstructed solar wind. As a result, we found that our simulation well captures the velocity, temperature and density profiles of an observed solar wind. Furthermore, we successfully reproduce the general characteristics of an interplanetary coronal mass ejection (ICME) obtained by the Helios 1/2 spacecraft (R. J. FORSYTH et al. 2006).