Masaaki Naruse

A numerical method for gas-solid two-phase free turbulent flow using a vortex method

Abstract This paper presents a numerical method for gas–solid two-phase free turbulent flow. The computation of the gas flow by a vortex method and the Lagrangian calculation of the particle motion are simultaneously performed, in which the change in the vorticity for the gas-phase by the interaction between the two phases is taken into account. The change due to the force exerted by the particle on the gas-phase is evaluated by an area weighting method, while the change by the viscous effect is simulated through a core spreading method. The present numerical method is also applied to calculate a two-dimensional gas–solid two-phase mixing layer to confirm the applicability. The numerical results, such as the number density, velocity and turbulent intensity of the particle, are favorably compared with the experimental data.

Numerical simulation of gas-particle two-phase mixing layer by vortex method

Abstract Gas-particle two-phase mixing layer is simulated by a two-way vortex method to investigate the effects of the mass loading ratio and the particle diameter on the flow. The method, proposed by the authors in a prior paper, simultaneously calculates the behavior of the vortex elements, discretizing the gas flow field, and the particle motion by the Lagrangian approach. The loaded particle delays the pairing process of the vortex element. When the mass loading ratio m is increased, the pairing process becomes less apparent and the flow structures are elongated in the streamwise direction. With an increment in m, the gas velocity gradient in the cross-stream section becomes gentler and the center of the mixing layer shifts toward the low-speed side. The velocity fluctuation of the gas lessens at the center of the mixing layer and heightens at the edges of the layer due to the loaded particles. These changes are unremarkable when large particles are loaded.

Two-dimensional vortex simulation of particulate airflow induced by free falling particles

This paper is concerned with the numerical simulation for a particulate air flow induced by free falling solid particles. The particles are stationed within a rectangular region at the commencement of the fall. They are made to fall in an air, and the air flow induced by the falling particles as well as the particle motion is simulated. The simulation highlights that the falling particles induce large scale eddies and that the eddies convect with involving the particles when the particle volume fraction is high. It also reveals that the strength of large-scale eddy becomes lower with increasing the aspect ratio of the particle ensemble.