Research On Wind And Snow Effect Of Main Girder And Vehicle-Bridge System Based On CFD-DEM Bidirectional Coupling

The large wind effect will cause drifting movement of snow on the bridge area,which will change the shape of the snow on the bridge deck.The aerodynamic performance of the bridge structure changes due to the change in the shape of the snow,which in turn threatens the safety and performance of the bridge.Based on the CFD-DEM two-phase flow coupling algorithm,this thesis discusses the fluid phase governing equations,particle phase governing equations and the coupling between the two phases under the wind and snow coupling state,and builds a wind and snow flow coupling framework.Based on the theory of wind and snow two-phase flow,combined with numerical simulation method,the main beam,vehicle-bridge combined system wind-induced snow movement and its influence on aerodynamic force were studied.The main work and conclusions of this paper are as follows:(1)Construction of a numerical simulation framework of wind and snow flow based on CFD-DEM two-way coupling.The Euler-Lagrange method in the two-phase flow theory is used to establish a CFD-DEM mathematical model to numerically simulate the movement of wind-induced snow drift.The air phase follows the NS equation,and the snow phase particle movement follows Newton’s laws of motion.The two-phase flow of wind and snow realizes the coupling effect through the exchange of momentum through the drag and buoyancy of the fluid.Based on the CFD-DEM coupling method,the parameters of the numerical simulation were clarified,and the snow distribution of the stepped roof area of Tsuchiya was numerically simulated.The results of the numerical simulation and the measured results were compared by the wind field distribution and the snow phase distribution,respectively It is basically consistent with the field measurement results,which verifies the rationality of the wind-snow two-phase flow coupling CFD-DEM model.(2)Research on the shape and aerodynamics of wind-induced snow in the main beam.Taking the typical single-box main beam as the object,the wind-snow two-phase flow coupled CFD-DEM model is used to numerically simulate the drift movement of the wind-induced main beam snow,track the position change of snow particles,and clearly describe the erosion and Sedimentation simulates the process of wind and snow flow movement to obtain the snow shape and aerodynamic force of the main beam at different times.By comparing the difference between the air phase and the snow phase under different wind speeds and wind angles of attack,the influence of wind and snow flow on the aerodynamic characteristics of the main beam is discussed.For this main beam,the amount of snow erosion on the leeward side of the bridge deck is significantly larger than that on the windward side,and a large amount of snow is deposited on the windward side of the main beam.The wind force causes uneven snow distribution on the bridge area,and the changes in snow cover cause changes in the flow field around the main beam,which in turn changes the aerodynamic shape of the main beam surface.The snow phase in the wind and snow flow will obviously change the drag coefficient,lift coefficient and torque coefficient.From the change of each component coefficient,the snow phase reduces the drag coefficient of the main beam,the lift coefficient increases,and there is a certain difference in the torque coefficient.(3)Establish a suitable vehicle-bridge combination system for wind and snow flow and study aerodynamics Establish the CFD-DEM model of the typical single-box main beam-vehicle,calculate the wind field around the vehicle-bridge combination system under no snow and snow conditions,monitor the vehicle aerodynamic force,and monitor the bridge deck pressure to obtain wind and snow Conditions,the aerodynamic force of the main beam affected by the vehicle.Compare the calculated aerodynamic force of the vehicle with the aerodynamic coefficient of the vehicle-bridge combination system in the absence of snow,perform a visual analysis of the wind-snow flow of the vehicle-bridge combination system,and explore the wind-snow flow and the vehicle-bridge combination system aerodynamics The relationship and mechanism.The most snow-prone area is near the windward side of the main beam and the leeward side of the vehicle.The lower side of the vehicle has suffered severe erosion due to the faster air flow rate;the snow depth coefficient of the main beam leeward side is relatively small The snow particles are relatively less distributed.For this vehicle-bridge combination system,wind and snow flow have a significant effect on the aerodynamics of the vehicle-bridge combination.Compared with the absence of snow,wind and snow flow causes the main beam moment coefficient to increase.At the same time,the drag coefficient of the vehicle decreases,the lift coefficient increases,and the torque coefficient increases.