平流层飞艇尾部形状对气动阻力的影响

为了研究平流层飞艇尾部动量边界层厚度与尾涡结构,应用LES(大涡模拟)方法计算了零攻角工况下飞艇绕流场,并对LOTTE和M-LOTTE两种飞艇进行了对比分析.采用Q分布和涡量描述回转体尾涡结构,根据Q分布可以确定M-LOTTE飞艇较LOTTE飞艇尾部分离区显著减小;并分析了回转体的轴对称曲面动量边界层厚度对飞艇气动阻力的影响,随着飞艇尾部厚度逐渐减小,动量边界层厚度逐渐增大,M-LOTTE飞艇尾部动量边界层厚度明显小于LOTTE飞艇.飞艇尾部动量边界层厚度分布说明了MLOTTE飞艇的总阻力系数较LOTTE飞艇降低17.2%的原因,同时也表明飞艇尾部形状对飞艇气动阻力影响较大.

Influences of geometry of hull tail on aerodynamic drag of stratospheric airships

LES (large-eddy simulation) method was used to simulate the external flow field around hulls of the LOTTE and M-LOTTE airships at zero incidence angle in order to analyze the momentum boundary thickness and trailing vortex structure of stractospheric airship. Q distribution together with vorticity was used to visualize the trailing vortex structures of revolutional body. The Q distribution shows that compared with the LOTTE airship, the separation region in the tail of M-LOTTE airship is much smaller. Influence of axial symmetry momentum boundary layer thickness of revolutional bodies on aerodynamic drag of airship was analyzed. It has been found that the momentum boundary layer thickness increases obviously toward to the tail end for both of the two airship hulls and apparently thinner momentum boundary layer thickness exists for the M-LOTTE airship. The distribution of momentum boundary layer thickness explains the fact that the total drag coefficient of the M-LOTTE airship hull was 17.2% smaller than that of the LOTTE airship. It can be concluded that hull tail geometry of the airship can significantly determine the total aerodynamic drag.