Optimization Study On Aerodynamic Add-on Devices Of The Container Semi-Trailer Truck

With the rapid progress on the construction of expressway in our country, the road transportation has great development.Nowadays,container semi-trailer truck, as the major tool in road transportation, plays an increasingly important role.To improve the efficiency of transportation, adapt the stricter policies on energy-saving and emission reduction, it is paid more and more attentions on the truck aerodynamics.There are two major methods used in vehicle aerodynamics,which are wind tunnel test and numerical simulation. With the rapid development of computer technology and taking the cost into consideration, the method of Computational Fluid Dynamics (CFD) is more and more widely applied to the process of automobile's research and development.It is reviewed that the developing history and the current situation on road vehicle aerodynamics and CFD.The external field of the truck was simulated by the CFD method. The result of numerical simulation provides an instruction for the truck design and research.At first, generate the grid computational model on the basis of three dimensional CAD model of the truck. Numerically simulate the external field of the truck without crosswind making use of the CFD software Fluent.The air flow in the external field of the truck is analytical researched in detail.The relationship between the flow characteristic of external flow field of the truck and the aerodynamic drag is on discussion.The reason why the drag was produced is clear. It provides references for the following work of drag reduction.The next, select several experimental points using Design of Experiment (DOE), based on the Response Surface Method (RSM),the function relationship is established between coefficient of drag and lift and the five parameters,which reflect the cab roof fairing.The optimization solution can be obtained by algorithm.To compare with the result of CFD numerical simulation, the relative error is less than 5%.Combined with the sensitivity anlysis,analyze the structural parameters which are sisitive to the aerodynamic drag of the truck.Optimizing design for a kind of commercial cab roof fairing,it has the guiding sense to the cab roof fairing of the real truck.Furthermore,three methods of simulating the truck in yaw angles were discussed. To compare with the result of wind tunnel test based on the standard model,method 3 was used for simulating the truck in yaw angles in this paper.At last,based on the truck aerodynamic characteristic of external flow, the vortex trapped device added on the front of the trailer. The influence on the aerodynamic drag by the geometric parameters of that was discussed.It provides references that improving the characteristic of drag of the truck in crosswind.