Simulation of Mixing Flows using Particle Exchange Technique in Moving Particle Semi-implicit Method

  • Imakiire, Yoshiya (The University of Tokyo)
  • Matsunaga, Takuya (The University of Tokyo)
  • Koshizuka, Seiichi (The University of Tokyo)
  • Yamauchi, Koji (Mitsubishi Chemical Corporation)
  • Takeda, Eiji (Mitsubishi Chemical Corporation)
  • Takenaka, Kazuhiro (Mitsubishi Chemical Corporation)
  • Ishiba, Yasushi (Mitsubishi Chemical Corporation)
  • Miyasaka, Etsuko (Mitsubishi Chemical Corporation)
  • Kikuchi, Yasuharu (Mitsubishi Chemical Corporation)

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The Moving Particle Semi-implicit (MPS) method [1] employs Lagrangian approach so as to keep clear interfaces in mixing flows as well as to maintain the numerical stability in violent free surface flows. To date, advanced techniques have been proposed to enhance the accuracy, stability and applicability, and various simulations have been carried out in industries [2]. However, one of the problems in the Lagrangian approach is disturbance of the interfaces and the free surfaces. Khayyer et al. proposed the technique named Optimized Particle Shifting to recover the disturbed free surface to be smoother by shifting the particles near the free surfaces [3]. In the present study, a particle exchange technique is proposed, where a pair of particles are exchanged to smooth the interfaces. Numerical stability and mass conservation are kept since the particle positions are not shifted while the particle types are exchanged. Taylor instability of heavy and light fluids is calculated using this technique. The interfaces are drastically smoothed without substantial change of the fluid behavior. Next, a mixing flow in a twin screw extruder is simulated. The technique of Tanaka and Masunaga [4] for the pressure Poisson equation and the boundary condition of Matsunaga et al. [5] are incorporated. In addition, a multi-resolution technique combining separation of a large particle and merging of small particles is used to efficiently analyze small gaps in the extruder. The particle separation to the half volumes is repeated six times to reduce the particle size to 1/4 in three dimensions. The particle exchange technique is applied to set the counterpart of a small particle to be merged. Using the present particle exchange technique, the counterpart small particle for the merging is always found successfully and the simulation can be carried out without isolated small particles. REFERENCES [1] S. Koshizuka and Y. Oka, Nucl. Sci. Eng., 123, 421-434 (1996). [2] S. Koshizuka, K. Shibata, M. Kondo and T. Matsunaga, Moving Particle Semi-implicit Method, Academic Press (2018). [3] A. Khayyer, H. Gotoh and Y. Shimizu, J. Comput. Phys., 332, 236-256 (2017). [4] M. Tanaka and T. Masunaga, J. Comput. Phys., 229, 4279-4290 (2010). [5] T. Matsunaga, N. Yuhashi. K. Shibata and S. Koshizuka, Int. J. Numer. Methods Eng.,