Numerical Simulation Of Flow Field Of Pipeline Anti-scouring Picket Pier

Currently,pipeline transportation plays an irreplaceable role as a unique transportation mode in water,gas,oil and power supply,etc.Pipelines are exposed and suspended by local scouring of water flow,and are highly susceptible to damage.In this paper,through the numerical simulation of fixed bed and dynamic bed for the pipeline and the pipeline supported by anti-scouring piers respectively,the changing characteristics of the flow field when each component is scoured locally under different incoming flows are studied,the impact of the flow field with or without anti-scouring piers on the flow field is compared and analyzed,and the development history of scouring and the maximum depth of scouring pits in the erodible sand bed after adding the anti-scouring piers are discussed,and the conclusions of the study include the following:(1)By setting different working conditions for the pipeline to carry out the numerical simulation of fixed bed and dynamic bed,the simulation results were compared with the test results,and the errors between the numerical simulation calculated values and the actual measured values were within the allowable range.(2)For the numerical simulation of the fixed bed,the flow field at different moments:the incoming flow generates three vortices near the single-pipe pipe,forms an obvious large vortex after the longitudinal profile 1 of the pipe pier member,and generates a small wake vortex after the longitudinal profile 2 of the pipe pier member;the pressure field at different flow rates:the pressure curves all show a trend of first decreasing and then increasing,the pressure difference before and after the pipe pier member is lower than that of the single-pipe case,the lowest pressure difference decreases by 2677 Pa,and the pressure difference decreases by 46%;turbulent energy:single pipe case at 1.5D after the pipe water turbulent dissipation collision occurs the most,the most frequent energy exchange.The maximum turbulence energy of single pipe case with different burial depth decreases by 0.502 m~2/s~2,and the turbulence energy decreases by about 67%,and the maximum turbulence energy of pipe pier member is lower than that of single pipe case by 0.208 m~2/s~2,and its value decreases by about 44%;shear force:the maximum shear stress on the bed surface increases with the increase of incoming flow velocity,and the maximum shear stress of pipe pier member is smaller than that of single pipe case,and the minimum decrease is 88%.(3)For the numerical simulation of the dynamic bed,the scour development process:the single-pipe case is mainly divided into the initial scouring stage,accelerated scouring and equilibrium stage,and the tail vortex strength formed by the incoming flow downstream of the longitudinal profile 1 of the pipe pier member does not cause obvious scouring effects on the bed,and the action range becomes larger after the longitudinal profile 2 of the pipe pier member,which is about 4D,and the scouring strength becomes lower;local scouring at different flow velocities:the depth of the pipe scouring pit is positively correlated with the flow velocity.Local scouring with different flow velocities:the depth of pipe crater is positively correlated with flow velocity,the maximum crater depth is about 0.98m,and the maximum crater depth of pipe pier members is lower than that of single pipe,with a minimum reduction of 64%;local scouring with different particle sizes:as the particle size of sediment increases,the critical shear stress required for sediment initiation increases,and the maximum crater depth around the pipe decreases.The maximum scour depth of each component is about 0.96m,and the maximum scour depth of longitudinal section 2 of the pipe pier component is 72%lower than that of the single pipe case.