Analysis Of Outflow Field Simulation Error Source Of Pickup Truck And Its Modeling Optimization

The intensification of the energy crisis makes the reduction of energy consumption an important subject in the automotive research field.It is a very effective measure to reduce the energy consumption by reducing the aerodynamic drag of the automobile.At present,CFD simulation is one of the most important methods to study the characteristics of vehicle flow field.Compared with wind tunnel experiment,this method has the advantages of low cost and high efficiency.In this paper,the CFD simulation method was used to analyse the error sources of the pickup truck’s external flow field simulation,and the aerodynamic shape optimization of the pickup truck body was carried out.First,the error sources of pickup truck external flow field simulation were analysed.The factors that influence the simulation of external flow field were studied from several aspects including grid strategy,turbulence model and wheel boundary condition.By comparing the speed vector of the pickup car,the pressure of the body surface and the distribution of the streamline,we concluded that the hybrid grid scheme between the three prism and the hexahedron has a higher calculation precision.The simulation performance of each turbulence model was compared from the calculation accuracy and convergence.It was concluded that the SST k-ω model has high computation accuracy.When the error allowes,the appropriate number of grids can be used to reduce the time consumption when calculating the Cd value of pickup truck.When studying the influence of wheel boundary conditions on the Cd value,the accuracy of the calculation can be improved by simulating the boundary conditions of the wheel with the rotating wall.It is found that the combination of the SST k-co model and the 10 layer boundary layer can obtain higher calculation precision when studying the influence of the combination factors of the turbulence model and the boundary layer number on the aerodynamic drag.Secondly,orthogonal test was adopted to optimize the body shape of pickup truck.Four body parameters,such as the corner of the windshield of the pickup car,the upwarping angle of the front part,the angle of the engine cabin and the rear end,were selected to study their influences on the aerodynamic drag of the pickup truck respectively.Then,the above 4 body parameters were chosed to establish an orthogonal test table to study the influence of multiple parameter combinations on aerodynamic drag coefficient.It was found that the Cd value of the optimized model is significantly reduced,with a decrease of 5.78%.Finally,the local modeling optimization of pickup truck was studied.The advantages and disadvantages of the local optimization method and the overall optimization method were compared.In order to improve the pneumatic modeling of pickup truck,the local optimization was used to study the influence of the front wheel damper plate,the rear bumper,the bottom guard plate and the tail corner on the aerodynamic characteristics of the pickup truck,and the optimization scheme was given.It eventually saved 2.89%fuel consumption and improved the fuel economy of pickup trucks.