Experimental study and numerical simulation of water-sand two-phase flow in fracture network

Abstract

ABSTRACT The flow characteristics of water-sand two-phase in fractured rock mass has an important influence on underground engineering. A series of laboratory experiments are carried out by using a self-made fracture network test system. Based on the Euler-Lagrange method, a numerical simulation study of water-sand two-phase flow is conducted. The effects of sand mass fraction w, sand particle size Φ and combination of inlet and outlet on the flow characteristics of water-sand are systematically analyzed. The results show that the water-sand outflow is directly proportional to the fracture openings, and the growth rate of water-sand outflow is significantly different under multiple inlet-outlets configurations. The final volume proportions of water-sand are 14.1%, 35.9% and 50% respectively. Fluidity I exhibits an inverse correlation with fracture opening, w and Φ. Under the condition of the single inlet and outlet, the minimum fluidity I for 0.6 mm opening is 3.28E–7 m2+ns2- n/kg, the maximum fluidity I for 2.0 mm opening, reaching 3.88E–6 m2+ns2- n/kg. Based on the response surface regression method, a multivariate regression model for three fracture openings was established, boasting exceptional predictive accuracy and reliability. Particle residence time correlates positively with w and Φ. The turbulent kinetic energy k is significantly affected by the fracture opening and decreases with the increase of w and Φ. The variation range of k is 0.38 m2/s2 ~0.63 m2/s2. The results deepen our understanding of the migration behavior of water-sand in the fracture network, and provide a theoretical guidance for groundwater resource protection and other underground engineering.