STUDY ON LIFT COEFFICIENT AND DRAG COEFFICIENT OF PROPPANT PARTICLE CLUSTERS IN HYDRAULIC FRACTURES BASED ON LATTICE BOLTZMANN METHOD

In hydraulic fracturing, the fracture wall has an important influence on the force of proppant clusters when transporting and settling in narrow fractures. In this study, a numerical model of particle flow is established based on the lattice Boltzmann method. The star, triangular prism and cuboid particle cluster models are constructed to study the variation of lift and drag of particle clusters under different Re and relative distance H/d from the wall. The results show that the drag and lift coefficients of particle clusters decrease with Re under the influence of wall, and the lift coefficient in the wall direction is always smaller than that in the non-wall direction. The ratio of single particle drag coefficient to cluster average drag coefficient decreases with Re, and increases with the influence of wall boundary effect. For the drag coefficient ratio of particles at different positions, it decreases for the front row particles, and it increases first and then decreases for the middle particles, and it gradually increases for the particles near the wall. With the increase of H/d, the particle clusters are far away from the wall and the boundary influence is weak, and the decrease rate of drag coefficient decreases gradually. For the front row particles and particles near the wall, the ratio of drag coefficient and lift coefficient decrease. The particles away from the wall gradually approach the wall, and the ratio of drag coefficient increases. The wall boundary effect can aggravate the force on the particles near the wall, and the outer particles have a shielding effect on the forces on the inner particles.