Lagrangian-lagrangian simulation of gas-solid two-phase flow across two cylinders

A new and effective Lagrangian-Lagrangian model based on the coupling of discrete vortex method (DVM) and the particle collision model was proposed to study the interaction between large eddies and particle cloud in turbulent flow across circular cylinders. To achieve the compatibility in the discrete vortex method, sub time-step was used to adjust the calculation time step of the particle motion to couple the two-phase simulation in our model. The present method was validated by the particle trajectory in Rankine vortex and was applied to simulate the horizontal particle transport process in high Reynolds number turbulent flow across circular cylinders for the particle sedimentation, entrainment and concentration process. The particle distributions were investigated with different Stokes number when the mean velocity was in the direction of gravity. For vertical gas-solid two phase flow, when the Stokes number is smaller than 1, particles are entrapped easily by vortex and finally is concentrated near the outer edges of vortex structure due to their quick response to the flow field. With the increase of Stokes number, particles respond more and more slowly to the flow field, and thus the influence of gravity is stronger. As Stokes number is far larger than 1, vortex structure has little influence on the particle distribution, which is similar to the distribution of free sedimentation.