The Low Wind Resistance Optimization Study On The Heavy Commerical Trucks Base On Aerodynamic Additional Device

In the early 1980s of 20th century, the research on heavy commercial truck's aerodynamics boomed in Europe and America. The mainly directions are shape optimization of cab and aerodynamics additional device design.Research shows that there are great relationship between the heavy commercial trucks aerodynamics drag coefficient and the body surface's fillet radius (especially cab part). The aerodynamics drag will reduce 30% at most if the body surface have reasonable fillet radius. Considered that the heavy commercial trucks'transportation functions and the structure characteristics, which decided it can't depends on a large area streamline design to reduce the aerodynamic drag. So design and optimization of the aerodynamics additional device just blaze a new path for the heavy commercial trucks drag-reduction and energy-saving.At present, compared with the cars, buses, and high-speed trains in aerodynamics drag-reduction have more thorough research and achievements, heavy commercial trucks on this aspects just getting started, too little guiding significance from the new methods and application of aerodynamics drag-reduction. In the early 1980s, only the professor Limin Fu in Chang Chun automobile research institute have the preliminary research of heavy commercial trucks flow field's liquid display and aerodynamics additional device. In recent years, China's literature limited to Air-deflector, not only have no in-depth studies on the principle of heavy commercial truck's aerodynamics drag and new aerodynamics additional device, but also new aerodynamics drag-reduction methods. According to above problems, this article mainly puts forward several new design of aerodynamics additional device. Firstly, we discussed the necessary automobile aerodynamics and computational fluid dynamics' basic theory. Automotive aerodynamics includes: six aerodynamics forces; computational fluid dynamics include:Related fluid type and flow characteristics classification:perfect fluid and non-perfect fluid, compressible and incompressible fluid, Laminar and turbulent, steady and unsteady flows, boundary layer and streaming around forces; Governing equation of computational fluid dynamics-Mass, momentum and energy conservation equation; By going through contrast and analysis for several commonly used turbulent model equations, we chose SST k-ωas numerical simulation turbulence equation in this article that according to their respective characteristics.Secondly, this paper adopts 1:1 proportion of heavy commercial truck model as experimental subjects, local simplified and keep most of original design. We only take half of the longitudinal symmetry to simulate for saving time and reduce grid numbers. The length of the computed field is 7 times to the truck (twice length of truck from cab to entrance,4 times length from the back of container to exit); The height of the computed field is 3 times to the truck; The width of the computed field is 2.5 times to the truck (twice width of truck form the truck's edge to computed field's border) because of half truck body calculation.At last, according to the analysis of original model, we got several flow separation key areas to add aerodynamics additional devices of truck. We are going to add air-deflector, rear air-deflector, side edge turning vanes, full gap seal, transverse gap seal, longitudinal gap seal, transverse-longitudinal mixed gap seal and wells style container back seal into the areas of cab's top, the gap between cab and container and container's back, analysis of their principles, combine them together according to their respective characteristics. To contrast to the original model, the aerodynamics drag of 4 results respective reduced 17.4%,19.8%,20.9%,24.4%.