CFD-oriented Parametric Modeling Of Automobile At The Bottom

In recent years, with the continued progress of science and technology, automobile manufacturers increasingly fierce competition among themselves facing users of product performance and the increasingly demanding high quality, safety and environmental standards and regulations more stringent constraints, and so the pressure, forcing its competition must shorten product development cycles, improve product quality, reduce development costs. Currently cars constantly speeding up the pace of upgrading, automotive products in the market gradually shortened life expectancy, and automotive research and development cycle has been reduced to 1 to 2 years, almost every year a new style, excellent quality, good performance and attractive looks, the car ride comfort type available. In the brutal competition in the market, further reducing vehicle development cycle and improving the quality of products has become the key to victory manufacturers. The vehicle aerodynamics as a vehicle development are closely related disciplines, it is necessary to seek its own breakthrough in the development of the automobile industry to increase the power. Reduce air resistance coefficient, improve its aerodynamic stability, control exhaust emissions, etc. can be embodied in the development of the automobile industry. How to better aerodynamics will be used in automotive product design and development. First of all, automobile aerodynamics should have achieved remarkable progress in the three-dimensional separation of cars and wake vortex resistance research.This paper studies the content of automobile in the conceptualization of the development of the design phase. In the conceptual design stage it should complete vehicle design, including the exterior appearance, interior design and color design. Design requirements must achieve both functional and aesthetic. Beautiful external design to give people the enjoyment of the beauty at the same time also affect market sales, is an important work. But the exterior appearance and the design must take into account the car should be good aerodynamic characteristics, which requires the desinger to make aerodynamics analysis in the conceptual design stage. Under normal circumstances, the CAS model is not directly used for CFD analysis by CFD engineers. At this point models of the apparent need CFD engineers do a large number of model geometry clean-up and re-building work in the CAD / CAS software. When these are completed, the CFD engineer need to make a floor model, so closed body model. Because of the complex shape at the bottom of the car, to complete body of work on the model of closed is particularly difficult, but also very time-consuming. To address these issues, this paper model body at the bottom of the closed model has been simplified, and the creation of this simplified model is made to be a modular, integrated into the UG software.Knowledge-based engineering (KBE) is an important branch of artificial intelligence and knowledge engineering theory in practice, and its essence is to "re-use." It focused on industrial products in its project development life cycle at every stage, is to make full use of all kinds of practical experience and expertise as well as other relevant information. The core of knowledge engineering is how to use the knowledge to solve the problem. The differences between knowledge-based systems and the traditional procedure is that the knowledge-based system handle knowledge as an object and the object of traditional processing is data.In this paper, the first time, knowledge engineering and aerodynamics of combining theory and method applied to the concept of car design stage, and it research the methods of the knowledge-driven body structure design in the face of computational fluid dynamics (CFD), and study on the structure of car Design parameters, automation and knowledgeable, and development the bottom (chassis and wheel) parametric modeling efficient design tools. These tools can help the body engineers quickly and efficiently complete the body design, to shorten design time and improve design quality, and to enhance the competitiveness of enterprises in the automobile industry is of great significance.At the bottom of the car in the conceptualization of appropriate design phase to simplify the development of this system is based on. But many parts of the car at the bottom are usually convex and concave grievances, so it uses zoning simplification. It can be divided into: nacelles, the Central Corridor and the exhaust pipe, spare cabin and four-wheel cover plate after suspension.At the bottom of the engine compartment little effect on the flow of air, so it is simplified into a simple handling; The flat central channel and the exhaust pipe of a car are on the same floor location, and the two were in the process of simplifying a cuboids-shaped concave slot instead, the specific size under different development model in accordance with the requirements set; spare tire compartment is more complex, more prone to turbulence and eddy current, detailed its simplified compared to retain the basic module spare shape suspension after taking into account space, and it will spare module connected with the central channel processing, spare cabin on the various drawbar Thus, as shown in Figure 3.6; Four-wheel cover plate is the main consideration to increase the snow tires anti-skid chains enveloping face, body surface to simplify round hood line as baseline, with a tire width parameter values to the y / y-direction of a surface extrusion cover a round plate; the front and rear suspension are omitted, and the only reservation is the wheel; All of others at the bottom such as holes, small ribs are omitted.Simplify the wheels in accordance with the results of previous studies of programmers. As the open area in the same circumstances, the appropriate number of openings will be increased to improve the aerodynamic characteristics. Generally speaking, as the number of openings increased, the total automobile aerodynamic resistance has decreased; with the increase in size of each hole the wheels of its own aerodynamic drag coefficient is increasing. Therefore wheel rims designed as a five-hole, the other dimensions are in accordance with the standard parameters calculated from the wheel.This paper studies the second development process in the platform of UG NX5 by using UG/OPEN API language, using UG/UIStyler components function in accordance with the simplified model of the car at the bottom called for the establishment of an interactive interface, and the functional modeling is adopted use UG/OPEN API language and C, C + + integration achievable. The whole system is the development of commercial software development processes, and a high degree of practical value. In this paper a three box car model as an example, the developed system is used to create the bottom CAD model which is a match with the automobile body model. Through its numerical simulation analysis, it access to several major aerodynamic parameters, and parameters of CFD analysis from the bottom of the plane simplified model to compare the data to prove that the simplified model created by the use of the system developed is more in the real value.