基于合成射流的高空飞艇分离流控制

采用数值模拟方法研究了基于合成射流技术的高空飞艇流动控制方法。将合成射流装置安放在飞艇表面,靠近分离线处,并沿分离线布置,通过合成射流口吹吸空气产生涡流,并将其注入边界层内来达到延缓流动分离,进而达到减阻和大迎角阵风减缓的目的。研究首先利用对原始飞艇进行仿真,找到分离线的位置,进而研究了合成射流口出射速度幅值不同时飞艇阻力系数的变化,并以此来分析合成射流的流动控制效果。结果表明,射流口吹吸速度幅值越大,时均减阻效果越好,但射流的能量消耗也越大,气动力的脉动幅值也大。在扣除合成射流本身的能量消耗影响以后,最优的时均控制效果发生在迎角30°左右。研究结果显示,合成射流可以用来降低飞艇小迎角下的巡航阻力,也可以用来控制大迎角情况下的瞬态气动力,从而作为阵风减缓措施。

Study on Separation Flow Control of Airship Based on Synthetic Jet

Flow control for high-altitude airship based on synthetic jet was studied by a numerical simulation. The synthetic jet was arranged along primary separation lines on the surface of the airship. The synthetic jet was injected into boundary layers around the airship through slots on the wall to generate vortex flows, thus delaying flow separation, reducing drag and mitigating gust at high angles of attack. The original airship was first simulated to find the locations of the primary separation lines; the variation of the airship"s drag coefficient was subsequently studied with various amplitudes of the synthetic jet. Based on these, the flow control effect of the synthetic jet is further analyzed. The results show that greater suction velocities have larger reduction in the time-averaged drag, but with a cost of more energy consumption and larger fluctuations of aerodynamic forces. After deducting energy consumption of the synthetic jet, the optimal time-averaged control was achieved at about 30 degrees angles of attack. The study indicates that synthetic jets can be used to reduce a cruise drag of the airship at lower angle of attack and to mitigate a gust by controlling transient aerodynamic forces at higher angle of attack.