Abstract：In order to study the flow separation phenomenon and wake vortex phenomenon in the downstream of the pipe system when the pipe car, as a kind of obtuse cylindrical structure with intersection flow field. The flow field characteristics of the downstream of the pipe system are studied by combining theoretical analysis and numerical simulation. The LES-WALE turbulence model is used in the numerical simulation, and the comparison between the results and the physical test proves the feasibility of the numerical simulation. The numerical simulation results are analyzed theoretically. Firstly, the velocity distribution in the flow field behind the flow separation cross-cylinder system is divided into two parts: the low-velocity flow area and high velocity flow area. The low velocity area is mainly distributed in the center of the section, while the high-speed flow area is distributed in the periphery of the section, which showing an approximate circular distribution. Secondly, in terms of velocity amplitude along the flow field, from the proximal section downstream of the cross-cylinder system to the distal section. The higher the overall velocity amplitude of the low-velocity flow area in the middle part, the lower the velocity amplitude of the surrounding high-speed flow area. The flow fields in the two areas shows a convergence change with the increase of the distance from the cross-cylinder system. Finally, in terms of the pressure characteristics of the flow field, the pressure along the flow field shows a downward trend as whole, and the average pressure of the pipeline flow field section at Z6 is only 3.4% different from that at the same flow.
