Abstract: Abstract: In order to provide a new alternative design scheme for the interception treatment of urban sewerage, and reduce the effluent overflow in the catchment or the incidence of water logging in the pipe network, the closure characteristics of the eddy current closure device, the static pressure field distribution, the velocity field distribution and the velocity streamline distribution of the internal flow field at different inlet height are investigated. In this article, the transient N-S equations of incompressible flow, the renormalization group RNG k-ε turbulence model and the VOF (volume of fluid) method of Euler model are selected to carry out three-dimensional numerical simulation on the eddy closure device. Under the change of inlet height, the influences of the eddy current on the closure properties and closure efficiency of closure device are analyzed, as well as the internal flow characteristics of device. At the same time, the closure characteristics of the eddy current interception device have been experimentally verified. The experimental results are in good agreement with that of the numerical simulation. Based on the analysis of the riveting characteristics and the internal flow field characteristics of the eddy current device, the results show that under all the inlet height, the eddy current closure device produces the S-type turning and plays the role of closure. The smaller the inlet height, the stronger the intercepting capacity of the eddy current closure device; but the possibility of overflow and blockage is also bigger. At the different the inlet height, when the S-type turning occurs, the water level in the catchment is not the same, indicating that the cutoff characteristics of the eddy current closure device not only are related to the water level in the water collecting well, but also may be related to the water level inside the eddy current closure device. When the inlet height is small, the area of the inlet cross section of the eddy current closure device is smaller than that of the outlet cross section, and the inlet function is the effect of the orifice interception. The cutoff is the superposition of the interception of the orifice and the cutoff of the device. With the increase of the inlet height, the cutoff efficiency of the eddy current closure device decreases at first and then increases, and the increase range is between 4/5 and 5/5 of the inlet height, indicating that to ensure no overflow or clogging and achieve good closure, the inlet area of eddy current closure device should be greater than the export cross-sectional area. In the whole flow field, there are different vortices of different sizes, which are mainly present in the bottom of the trap, the gas-liquid interface, and the upper part of the internal and external eddy current closure device, and the existence of the eddy current closure device makes the fluid obtain dynamic pressure, resulting in obstacles obstruction. In the eddy current closure device, the high-speed swirl forms. The eddy closure device has S-type shutoff characteristics because of the low pressure or even negative pressure inside the eddy current closure device. With the decrease of the static pressure, the dynamic pressure increases, and the fluid flow rate increases; on the transverse cross section of the eddy current closure device, a high-speed swirl is produced around the low pressure zone, so the fluid flows out rotationally from the swirl device, resulting in the closure of cyclone flow. Through the experimental verification, it can be explained that the high speed vortex generated by fluid is a spiral gas column, and has a performance of long extension, which is beneficial to realize cyclone cleaning.