机身上翘后体绕流与阻力分析

Analysis of the flows and the drag about upswept afterbodies

基于N S方程数值计算研究了九个机身上翘后体在零迎角、高亚音速时的绕流与其阻力之间的关系。结果表明,后体在零迎角时存在三种流型:附着流型、分离涡流型和底部分离流型;影响阻力最大的几何参数是后体收缩比,其次是上翘角;收缩比ηA较大时(如ηA≥0.5),会产生很大的底阻;上翘角增加则使压差阻力迅速增大。当收缩比ηA减小时(即尾部较尖)使底部分离引起的粘性压差阻力大大减小,从而可实现最小的后体阻力。因此,首先选择较小的ηA排除底部绕流分离流型的出现、再选择适中的上翘角是上翘后体设计的一项重要原则。

The flow over upswept afterbodies of transport aircraft at zero forebod y incidence and highersubsonic speed has been investigated by numerical metho d based on 3D compressible NS equations in order to study the relationship bet ween flow fields and drag values of the afterbodies. The results show that there are three flow patterns for the nine upswept afterbodies, such as attached flow , separated vortex flow and base separated flow. The afterbody drag is influence d by two major geometric parameters--afterbody contraction ratio and afterbody upswept angle. The base drag increases rapidly with increasing contraction rati o (ηA≥0.5). The pressure drag increases rapidly with increasing upswept angle. The pressure drag on the upswept afterbody caused by separated flow can g reatly decrease with decreasing afterbody contraction ratio so as to reach the m inimum drag. Therefore, it is an important principle to select smaller contracti on ratio and temperamental upswept angle in order to avoid base separated flow a nd weaken separated vortex throughout the afterbody aerodynamic design. 