不同迎角下脊形前体绕流数值模拟研究

Simulation of flow around ridge precursors at different angles of attack

脊形前体有较强的背风涡流场,不同的前体形状对前体涡流场和气动力有很大的影响。本文针对脊形前体飞行器大迎角湍流大分离流动计算的困难,采用IDDES混合湍流模型,以及与之匹配的非定常算法,研究了不同来流迎角下脊形前体的气动特性,以及背风涡非定常演化、破裂的细致流动结构。选取了不同脊形角,以及不同上、下高宽比的脊形前体进行计算。计算结果表明,在迎角较小时,随着迎角的增大,前体主涡会逐渐增强,在迎角较大时,前体主涡破裂;在相同迎角下,脊形角较小时,前体涡较强,涡升力也更大;对于相同脊形角的前体,当上半截面高宽比较小时,前体主涡强度较大,前体涡破裂临界迎角较小,即会提前破裂。

The advantages of good stealth and supersonic flight performance make the ridged precursor an ideal configuration for future high-performance fighters and cruise missiles.The ridged precursor has a dominant leeward vortex,and the shape of the precursor can have a great influence on the vortex as well as the aerodynamic forces.Although many research works have been carried out on the static aerodynamic characteristics of ridged forebodies,which have also been applied to engineering practices,the understanding on the flow evolution mechanism and the influence of ridged forebodies at high angles of attack is still insufficient.To overcome the difficulty in simulating separated turbulent flows at high attack angles for ridged precursor aircrafts,the present study adopts the IDDES hybrid turbulence model with a matched unsteady algorithm.This work focuses on the aerodynamic characteristics of ridged precursors at different attack angles,and gives the detailed evolution of flow structures,including the breakdown of the leeward vortex.The ridged precursors with different ridge angles and different ratios of height to width are selected for the computation,and the results show that when the attack angle is small,the leeward vortex of the ridged precursor gradually increases with the increase of the attack angle;above a certain attack angle,the leeward vortex breaks down.For a given attack angle,when the ridge angle becomes smaller,the leeward vortex gets stronger and the vortex lift gets larger.For precursors with the same ridge angle,when the ratio of the height to width for the upper half section becomes smaller,the strength of the leeward vortex gets larger,and the critical attack angle gets smaller,i.e.,the precursor vortex breaks down in advance.