Mesh rezoning for a dynamic triangular finite-elements hydrocode

A Lagrangian type of finite element hydrocode has one major disadvantage as it cannot handle severely distorted elements. A remedy to this problem is rezoning. In most works concerning rezoning, the entire domain simulated is rezoned at times determined by input data. In most problems rezoning is necessary only at certain times and in certain local regions. This paper presents a new approach: the time of rezoning is automatically determined, and only local regions are rezoned when necessary. The new mesh is generated by automatic triangulation. The assignment of values of variables to the nodes and elements of the new mesh is done in such a way that mass, internal energy, momentum, and kinetic energy are conserved for the region rezoned. The approach was programmed into the Lagrangian hydrocode DEFEL and penetration problems were simulated as examples. Even though the penetration depth is in agreement with the result from an approximate erosion algorithm, a more accurate shape of the penetrator tip was obtained by the new rezoning approach.