蜻蜓爬升过程间歇性拍动飞行现象的数值研究

采用数值模拟方法研究了蜻蜓双翼做间歇性拍动运动时的气动特征。计算结果表明,在所研究的雷诺数工况下(Re=157),模型翼的平均升力系数和平均推力系数随着间歇占比的增大而减小,前段下降较快,中段下降平缓,后段下降至零。其中平均推力系数受到的影响相对平均升力系数更大,当连续飞行转变为间歇性飞行时,短暂滑翔初期和短暂滑翔稳定阶段均大幅削弱推力系数,共占42.7%;而对于升力系数,短暂滑翔稳定期对升力系数的削弱作用很大,占41.4%,但短暂滑翔初期却对平均升力系数的提高贡献8%。间歇拍动飞行能够提高蜻蜓飞行的升推比,当滑翔时长占间歇飞行周期之比为0.3时,平均升推比接近为1。

Numerical study on intermittent flapping flight performance of dragonfly during climbing

Aerodynamic force generation in a dragonfly intermittent flapping flight with modeled wings was studied using the method of numerical simulation.The computational results show that the average lift coefficient and average thrust coefficient of the modeled wing decrease with the increase of the intermittent proportion at the Reynolds number of 157.They descend faster in the frontal part,while gently in the middle part,and decrease to zero in the latter part.The average thrust coefficient is affected greater than the average lift coefficient.When the continuous flight turns into intermittent flight,the thrust coefficient during the early phase and stable phase of short gliding is significantly weakened with totally 42.7％;For the lift coefficient,it is mainly weakened during the stable phase of short gliding,accounting for 41.4％,but the early phase of short gliding has a contribution of 8％ to the increase of average lift coefficient.Intermittent flapping flight is possible to improve the lift-thrust ratio in dragonfly flight.When the the proportion of gliding time to intermittent flight cycle is 0.3,the average lift-thrust ratio is close to 1.