Research On Non-smooth Body Aerodynamic Drag Reduction Characteristics Of Heavy Trucks

In recent years, China’s atmospheric environment is deteriorating,"haze"pollution phenomenon becomes the new factor which restricted the people’sproduction and life. Studies have shown that: about20%-22%of atmosphericparticulate matter comes from vehicle exhaust emissions, and heavy trucks alwayswork in conditions like high fuel consumption, long working hours,high emissions, soif we improve the heavy trucks resistance characteristics, we can not only effectivelyimprove their fuel economy, but also can effectively reduce emissions and improvethe atmospheric environment, so it is a issue with important research and practicalvalue.This paper presents the study of non-smooth surface’s application to the heavytruck’s drag reduction research. The effect of drag-reducing properties of pit-typenon-smooth surface of the external flow field by means of heavy trucks CFD(computational fluid dynamics) method. Through the optimization of non-smoothsurface designed for optimal drag reduction program. The above method is applied tothe study of a real truck and get a more ideal drag reduction.Firstly, to build a heavy truck model, a preliminary study of the characteristics ofits external flow field is carried on by CFD method for determining the non-smoothsurfaces adding location, add a non-smooth surface by comparing the changes of theflow field the truck after of non-smooth surface of its flow field characteristics of.Heavy truck models by analyzing the tail pressure and turbulent kinetic energy cloudcloud reveals the reason for reduced aerodynamic drag, and by means of vortex flowinside the pit cushion effect reveals the non-smooth surface drag reductionmechanism.Second, in order to obtain the maximum drag reduction the pit-type non-smoothsurface was optimized. We firstly optimize the design variables related to non-smoothsurface call gradient optimization method. The specific process is similar to thecontrol variables: To determine the optimal depth of the pits within the range by thedesign of the pit depth is increased or decreased while the remaining variables remainconstant, other design variables is determined with similar method. Second, considerthe coupling factor between the design variables for all design variables globaloptimization method called multi-objective optimization,30sets of sample points ofdesign variables were randomly selected to build Kriging approximate model, verified the accuracy of the approximate model and determined the range of the parameters.Finally, obtained the optimal value and the better optimization results.Finally, these findings were applied to a subsection truck, by combiningexperimental and simulation methods to verify the engineering practicality ofnon-smooth surface drag reduction. Determine the optimal solution applicable toinstances of heavy trucks through multi-objective optimization methods.The text Included the theory inquiry of the heavy truck aerodynamic dragreduction based on non-smooth surface characteristics, and with the wind tunnel testdata to explore the feasibility of non-smooth surface drag reduction characteristicswill be applied to the heavy truck drag reduction research, by means ofmulti-objective optimization method further improved drag reduction effect ofnon-smooth surface, which has a certain significance for the study of heavy truck dragreduction.