客车车身周围流场数值模拟的空间离散化研究

【作者】 陈斌；

【导师】 高利；

【作者基本信息】 长安大学 ， 车辆工程， 2000， 硕士

【摘要】 客车车身周围空间离散是客车车身周围流场数值模拟研究的关键步骤之一。通过对客车车身曲线曲面数学描述方法、网格单元划分方法及目前面临问题的分析，在进行客车车身外表面数值模型建立的基础上重点进行了有限元法流场数值模拟的空间离散研究。 客车车身表面数值模型建立是客车车身周围流场数值模拟空间离散的基础。客车车身由大量相互约束的自由曲面组成，本研究利用B样条和NURBS曲线曲面，以测量试验得到的数据为原始数据，运用逆向工程原理，建立了客车车身数值模型。并研究了利用双三次曲面，对有公共交接的曲面进行光顺拼接及对三角域进行缝合。 为了对客车车身周围空间进行单元划分而得到高质量的网格单元，本研究依据空间拓扑原理，对客车车身周围三维空间进行了拓扑分区。利用客车车身数值模型提供的数据，采用代数和椭圆型方程相结合的方法，对客车车身周围三维空间进行了网格单元划分。为进一步提高网格单元的质量，提出了网格单元密度控制的指数函数控制方法。本次研究利用抛物化了的椭圆型方程，加速网格单元的划分速度。对于三维网格单元的节点编号优化，研究提出了最小节点数阵面推进法，自动进行节点编号优化。 本研究运用Visual C⁺⁺程序设计语言，在Windows平台上开发了3D—BusMesh软件，以客车车身数值模型建立为基础，实现了客车车身周围空间自动拓扑分区及单元划分并自动生成了网格节点—坐标、单元—节点信息。更多还原

【Abstract】 The discretization of the space around bus body is one of the key steps in the studying of numerical simulation to the flow field surrounding bus. By analyzing the mathematical description of curves and surfaces, the methods of mesh generation and the questions we face at present, the space discretization that will be used in finite element numerical simulation is particularly carried out based on the surface numerical modeling of the bus body. The surface numerical modeling of bus body is the base of the space discretization. As the bus body composes of mass free surfaces, B-Spline and NURBS are applied. According to the reverse engineering principle, and on the basis of the datum that comes from three-dimension measure experimentation, the modeling of buses body is established. Also, the method that the surfaces commonality connecting are joined and the triangle field is sewed by applying the double cube B-Spline style is utilized. The three-dimension space around the bus has been partitioned topologically according to topological theory so as to improve the quality of mesh and elements generation from the division of the space. In this work, the datum which are provided by the above modeling have been used, the method that composes of algebra equation and ellipse equation has been adopted leading to measure off the three-dimension space surrounding the bus. Exponent function control method is presented to further advance the quality of the mesh and elements. For speeding up the discrete rapidity, the elliptic equation improved by parabola has been applied. The means that known as the least node amount section advance is educed to optimize node number order. With Visual programming language, 3D-BusMesh software has been developed in Windows environment. On the basis of numerical modeling of the bus body, the automatic topological partition of the space enclosing the bus body and the elements discretization have been accomplished automatically resulting in node-coordinate and element-node information.更多还原