Ramp Wave Compression in a Copper Strip Line: Comparison Between MHD Numerical Simulations (LS-DYNA®) and Experimental Results (GEPI device)

GEPI [3][4] is a pulsed power generator developed by ITHPP for Centre d’Etudes de Gramat (CEG) devoted to ramp wave (quasi isentropic) compression experiments in the 1 GPa to 100 GPa range and to non shocked high velocity flyer plate in the 0.1 km/s to 10 km/s range. The aim of this paper is to compare numerical simulation and experimental results on a 3D GEPI configuration. A coupled mechanical / thermal / electromagnetism simulation has been performed to validate the new LS-DYNA beta version, ls980, where the electromagnetism package has been implemented. The validation is realized by free surface velocity comparisons on a reference configuration [5]. The study is presented in three main steps. First, a validation of LS-DYNA is performed by comparison to an analytical model and to another electromagnetic solver modeling a basic configuration. In the second step, the GEPI configuration is described and experimental strip line free surface velocities are analyzed. Then LS-DYNA models are presented. The model validation is realized by free surface velocity comparisons between LS-DYNA and GEPI results. As the electromagnetism solver requires a lot of memory, in order to optimize the memory used as well as the CPU time, the electromagnetic domain is limited to the “launcher” with a thickness around 1 mm. The rest of the strip line is merged to the “launcher” and the mechanical solver only is used there. The last section of this study presents the optimization of the strip line geometry in order to improve the magnetic pressure homogeneity along this strip line.