Numerical Simulation Study On The Coating Erosion Of Steel Members In Inland River Terminal

The large wharf in the upper reaches of the Yangtze including Chongqing,Sichuan,Guizhou,due to the existence of shallow covering layer and deep water construction problems,the lower part of the wharf is mainly used in the type of steel pipe concrete,both pile foundation and crossbar are widely used in steel structure.At present,the steel components of inland river port adopt coating protection method,which is mainly based on the anti-corrosion standard of coastal steel structure.However,compared with the offshore,the inland river has a large flow velocity and a high sediment concentration in the flood season,which causes the coating to rapidly age under the effect of sediment erosion.In this paper,a numerical model of the flow field around water-sandowed two-phase circular cylinders is established using CFD numerical simulation method.Based on this,the erosion characteristics of sediment particles under high flow velocity and sediment-laden flow in inland rivers are studied based on the existing erosion theory.The model proposes an erosion damage model under inland conditions.The main research work and achievements of this paper are as follows:(1)A large eddy model was used to simulate the unsteady turbulent flow field,and a particle random orbit model(DPM)was used to simulate the sediment trajectory.A numerical model with a Reynolds number of 1.5×10~5was established.The resistance coefficient C_d,lift coefficient C_l,Strouhal number St,surface pressure coefficient,and the distribution characteristics of sediments with different particle sizes in the wake are basically consistent with the literature results,verifying the reliability of the model.(2)Based on the established numerical model of water and sediment flow,the erosion characteristics of the silt particles at different diameters and different flow velocities are studied.The results show that the nearer the column 90 is the stigma,which is subject to sediment erosion.The greater the probability,the smaller the erosion speed.Most of the sediments slide across the cylindrical surface with a small angle of attack,causing micro-cutting damage to the surface of the coating material and forming a long gully after repeated rinsing.Near the cylinder 90°,there will be a small amount of sediment impacting the coating at a large angle and forming an impact pit under repeated impact.The larger the particle size or velocity of the sediment,the greater the probability of erosion of the position of the cylinder 45°-90°,and the increase in erosion velocity,erosion angle,and effective impact rate.When the particle size increases to a certain extent,the effective impact rate begins to decrease.(3)Based on the numerical model of water flow around sand,the erosion characteristics of silt particles at different particle sizes and different flow velocities on cylindrical back surface are studied.The results show that the back surface of water is close to the-90°position of the column and is subject to sediment erosion.The greater the probability,the greater the erosion speed.Most of the sediment particles that eroded the backwater surface still have a small attack angle across the cylindrical surface.Compared with the water surface,there is a wider range of large-angle erosions on the back surface,and the proportion is more,but the erosion is far less than the surface.The larger the particle size or velocity of the sediment,the greater the probability of erosion at the-45°to-90°position of the column,and the increase in erosion velocity,erosion angle,and effective impact rate.When the particle size increases to a certain extent,the effective impact rate begins to decrease.(4)Based on the numerical simulation results and the existing erosion model,the mathematical model of coating erosion under the conditions of inland river flow with sediment flow is proposed.The thickness damage of the coating at four flow rates of1.0m/s,1.2m/s,1.5m/s,and 1.8m/s was calculated.The maximum erosion at each flow rate was found in the cylinder 30°-45°.Comparing the calculated values with the experimental values of the indoor model,the applicability of the proposed coating erosion mathematical model was verified.