小展弦比飞翼标模非定常流动及自由摇滚特性

Unsteady flow and wing rock characteristics of low aspect ratio flying-wing

小展弦比飞翼布局是中国新型战斗机布局的选择之一,其动态特性尤为重要。针对小展弦比飞翼标模在较大攻角下出现的非定常流动与自由摇滚现象,采用延迟脱体涡模拟(DDES)方法以及动力学模态分解(DMD)方法研究了飞翼标模在Ma=0.6下的非定常流动特性、脉动压力特性、自由摇滚特性,分析运动失稳机理,探索失稳运动控制方法。研究表明:飞翼标模大攻角下非定常流动特性主要体现为,头部发展的集中涡、涡破裂、螺旋波流动结构,其中旋涡破裂点以St=0.12~0.23的频率沿涡轴振荡,螺旋波频率在St=1.16~2.33范围内。数值模拟获得的飞翼标模自由摇滚特征与风洞试验吻合较好,摇滚运动出现在俯仰角24.5°~26°,滚转角平衡位置为28°。对摇滚机理的研究发现,背风侧的集中涡流动与迎风侧的分离流动相互“博弈”是摇滚运动发生与维持的物理机制。上扰流板打开30°时,对自由摇滚运动控制效果不明显,外侧副翼向下打开30°时,自由摇滚现象能够得到较好的抑制。

The low aspect ratio flying-wing layout is one of the options of new fighter aircraft,and its dynamic charac⁃teristics are particularly important.Aiming at the unsteady flow and wing rock of the low aspect ratio flying-wing stan⁃dard model at a large angle of attack,we employ the Delay Detached Eddy Simulation(DDES)method and the Dy⁃namic Modal Decomposition(DMD)method to study the unsteady flow,fluctuating pressure and wing rock character⁃istics of flying-wings.The instability mechanism is analyzed and the method of instability motion control is explored.The results show that the unsteady flow characteristics(Ma=0.6)of the flying-wing model at a large angle of attack are mainly reflected in the concentrated vortex,vortex breakdown,and spiral wave.The vortex breakdown point oscillates along the vortex axis at the frequency of St=0.12-0.23,and the spiral wave frequency is within the range of St=1.16-2.33.The wing rock characteristics of the flying-wing model obtained through numerical simulation are in good agree⁃ment with those of the wind tunnel test.The wing rock phenomenon appears at the angle of attack of 24.5°-26°,and the roll angle balance position is 28°.It is found that the balance between concentrated vortex flow on the leeward side and separated flow on the windward side is the physical mechanism for the occurrence and maintenance of wing rock.When the upper spoiler is opened for 30°,the control effect of wing rock is not obvious.When the outer aileron is de⁃flected for 30°downward,the wing rock phenomenon can be well restrained.