Aerodynamic Design and Shape Optimization with the Far-Field Drag Decomposition Approach

基于阻力分解方法的气动特性及优化设计研究

¹ School of Aeronautics, Northwestern Polytechnical University, Xi'an 710072, China
² Unmanned System Research Institute, Northwestern Polytechnical University, Xi'an 710072, China
³ China Academy of Launch Vehicle Technology, Beijing 100076, China

Received: 25 June 2019

Abstract

In the aerodynamic shape design, the drag prediction has always been an extremely challenging mission for the exploration of a configuration. As for the more complex configurations, it is especially desired to the availability of a highly accurate and reliable aerodynamic numerical solution. For improving the drag prediction accuracy and promoting the aerodynamic shape designs, firstly, the characteristics of drag prediction based on far-field drag method and near-field drag method is analyzed and compared. Also, the merits and demerits of defining axial velocity defect with the current main far-field drag prediction approaches is summarized, which promotes the building of the improved method of axial velocity defect and the improved far-field drag prediction and decomposition approach. Moreover, during the establishment of the drag decomposition method, it is necessary to judge and decide on the selection of the drag region. Therefore, the discussions on the sensitivity of the relevant parameters are fulfilled. Furthermore, based on the far-field drag prediction and decomposition method constructed, the aerodynamic performance research of Common Research Model wing-body configuration is launched. The results show that it can effectively observe and analyze the changes in drag components, their impact on the total drag and the contribution percentage. Finally, combining the far-field drag prediction and decomposition method proposed in this paper with a gradient-based aerodynamic shape optimization design system, the aerodynamic shape optimization designs are studied with CRM wing-body configuration. The results can not only directly analyze the detailed change of the visualized drag region, but also can obtain the more accurate total drag and lift-to-drag ratio of the optimized configuration by removing the spurious drag.

摘要

在气动外形设计研究中，设计构型的阻力预测一直以来都是一项极具挑战的任务，而对于越来越复杂的构型而言，更是希望能够得到高准确度和高可信度的阻力数值结果。为了能够实现更加高精确度的阻力预测方法，并有针对性地开展气动外形设计研究，首先对比和分析了近场法和远场法进行阻力预测的特点，并提炼出现有主流的几种远场法关于轴向速度损失量（axial velocity defect）公式的优劣势和差异，进而提出了关于轴向速度损失量的改进方法，建立了改进的基于远场法的阻力预测方法和阻力分解方法。其次，在阻力分解方法建立的过程中，由于需要对阻力区域的选择划分进行判断和决定，因此开展了相关参数敏感性的讨论分析。然后，基于构造的阻力分解方法，针对Common Research Model（CRM）翼身组合体构型开展了气动特性研究，结果表明文中的方法不仅可以充分保证力系数的预测精度，还可有效分析不同阻力分量及其对总阻力的影响和具体的贡献占比。最后，将改进的阻力分解方法融入基于梯度的气动外形优化设计系统，针对CRM构型进行了气动外形优化设计，优化结果不仅可通过阻力区域识别函数直观感受阻力分量可视化区域的详细变化情况，还可更加精确地得到优化构型去除伪阻力以后的总阻力与升阻比。