高速有迎角圆锥绕流底部复杂流动结构研究

Research on complex flow structures at the base of high-speed conical flow with an angle of attack

  • 摘要: 在非零攻角下,圆锥外形底部流动将失去轴对称性,其流动结构将显著区别于零攻角工况。本文以Reentry-F飞行器飞行试验中高度为37.5 km、马赫数为19.13的工况为基准工况,利用数值模拟方法开展了5°半锥角圆锥外形非轴对称层流底部流动结构研究,分析了来流攻角、马赫数、雷诺数等因素对底部流动结构以及底面热流、压力等参数的影响规律。研究结果表明:与零攻角时的锥形回流区不同,非零攻角下回流区为非规则形状,且回流区长度较零攻角大幅减小,最大减小了44.6%。随着攻角增大,底部涡与前体背风侧涡发生相互作用,导致回流区长度随攻角增大呈现先减小后增大再减小的非线性变化规律;模型底面的无量纲压力、斯坦顿数峰值总体上呈现先减小后增大的趋势。随着马赫数增大,流动的可压缩性增强,小尺度的涡面及波系结构减少,回流区长度单调减小,无量纲压力和斯坦顿数峰值则分别呈单调增大、单调减小的变化趋势。雷诺数对波系结构的影响相对较小,随单位雷诺数增大,黏性效应减弱,回流区背风侧凹陷逐渐增强,回流区长度单调增加,无量纲压力及斯坦顿数峰值均单调减小。

     

    Abstract: Under non-zero angle of attack, the near-wake flow of a conical shape vehicle loses its axisymmetric nature, and the flow structure significantly differs from that under the condition of zero angle of attack. In the present study, we selected a reference state from the Reentry-F flight experiment of an altitude of 37.5 km and Mach number of 19.13, and conducted a numerical study on the laminar near-wake flow structure of a 5° half-cone angle circular cone. Influences of the angle of attack, Mach number, Reynolds number, etc., on the near-wake flow structures, pressure and heat flux on the base surface were analysed. The results indicated that, in contrast to the conical shape at zero angle of attack, the recirculation region at non-zero angles of attack displayed an irregular shape, and its length decreased significantly, up to 44.6%. As the angle of attack increased, the near-wake vortices and the leeward vortices of the forebody could interact with each other, which results in a trend of decreasing-increasing-decreasing of the recirculation zone length. The non-dimensional pressure and peak values of the Stanton number showed a decreasing-increasing trend with the increase of the angle of attack. As the Mach number increases, the flow compressibility got stronger, leading to a monotonic decrease in the length of small-scale vortex surfaces and wave structures in the recirculation zone, while the dimensionless peak pressure increased monotonically, and the peak Stanton number decreased monotonically. The influence of Reynolds number on the wave structures was relatively small. As the unit Reynolds number increased, the viscous effect weakened, resulting in an increase in the leeward depression of the recirculation zone and a monotonic increase in the length of the recirculation zone, with both the dimensionless peak pressure and Stanton number decreasing monotonically.

     

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