Simulations on Pressure Characteristics of Low-Flow Rate Water Circulating System Based on Porous Media Model

A spherical experimental device is placed in an underground cylindrical laboratory hall, and the surface is covered with ~17,510 photomultiplier tubes (PMTs) for detecting radiation signals. Since the device is placed underground for a long time, an effective water circulation is required to remove radon and algae to ensure stable operation. In this paper, the pressure distribution characteristics of water in the PMT region are studied. The PMT areas of the device are simplified into a porous media. Two models, i.e., a vertical-flow and a horizontal-flow model, were established to obtain the coefficient of resistance using CFD. In addition, the relationship between the pressure difference and the water entry parameters in the porous media is also studied. The results show that the resistance coefficients of single-layer PMT and two-layer PMT are similar in the vertical direction. However, the resistance coefficient of two-layer PMT in the horizontal direction is smaller than that of the single-layer PMT. Another simplified 2D model was also proposed to further study the effect of the simplified porous media on the overall flow. Overall, when the water inlet velocity is smaller, and the angle of inclination of the inlet is larger, the fluid is more likely to pass through the PMT areas, and the pressure distribution in the PMT areas can be more uniform.