Improved collision model to analyze the flow characteristics of sand-containing fracturing fluid in T-tube

Abstract

The choice of particle calculation time step in CFD-DEM (Computational Fluid Dynamics and Discrete Element Method) coupling calculation affects the accuracy and efficiency of particle collision calculation. In this paper, interpolation algorithm is introduced to weighted average the velocities of particles before and after collision. According to elastic theory, particle collision force is calculated and dynamic equation is solved. The initial value of the velocity was corrected by the velocity convergence criterion and the number of iterations was automatically adjusted. A high-efficiency and high-precision reinforced hard-ball model was proposed that is not affected by the calculation time step and does not require a detailed description of the collision process. In the case of collision of two particles with uniform and variable speed, the calculation error was less than 4%, and the calculation efficiency was increased by 36.3% and 36.8%. Pressure loss experiment showed that the model can accurately calculate the pressure loss. Analysis of the flow characteristics of the T-tube showed that increase in the flow rate and sand ratio, increased the density of the collision force distribution, increased the diameter ratio, significantly decreased the local collision and accumulation phenomenon, and resulted in more uniform collision force distribution.