ダイカストにおける乱流を考慮した気液2流体問題の数値解析法

抄録

  In die-casting simulation, it is very important to take into account back pressure and the flow of air remaining inside the mold. However, two-fluid flow simulation requires considerable calculation time, because of the difficulties in the convergence of calculation and the conservation of mass balance. In the present study, we propose an implicit FEM algorithm applying the Semi Laglangean Galerkin Method (SLG) for the advection equation of the VOF function to realize computational efficiency and stabilization. This numerical method was developed based on tetra mesh, which can be used to build analytical models automatically. Furthermore, we adopted a VOF function transformation technique to preserve the mass conservation and keep the interface sharp. As a bench mark test problem of the advection equation for this numerical method, we applied the present scheme to the rectangle rotation problem.
  We confirmed that the sharp interface between liquid and air was preserved after one rotation of the rectangle. Furthermore, we applied the present scheme to the dam break problem with an obstacle. Use of the VOF function transformation technique maintained mass conservation error within 0.15%, and the simulation could be performed with a large time step interval by applying the implicit method. Compared with experimental data, the characteristic behavior of the interface could be determined using the present scheme. Finally, we applied this scheme to squeeze casting simulation, and the numerical results showed good qualitative agreement with experimental data.