Quinn Daniel B, Watts Anthony, Nagle Tony, Lentink David
Department of Mechanical Engineering , Stanford University , Stanford, CA , USA.
Jacobs , Tullahoma, TN , USA.
R Soc Open Sci. 2017 Mar 29;4(3):160960. doi: 10.1098/rsos.160960. eCollection 2017 Mar.
Our understanding of animal flight benefits greatly from specialized wind tunnels designed for flying animals. Existing facilities can simulate laminar flow during straight, ascending and descending flight, as well as at different altitudes. However, the atmosphere in which animals fly is even more complex. Flow can be laminar and quiet at high altitudes but highly turbulent near the ground, and gusts can rapidly change wind speed. To study flight in both laminar and turbulent environments, a multi-purpose wind tunnel for studying animal and small vehicle flight was built at Stanford University. The tunnel is closed-circuit and can produce airspeeds up to 50 m s in a rectangular test section that is 1.0 m wide, 0.82 m tall and 1.73 m long. Seamless honeycomb and screens in the airline together with a carefully designed contraction reduce centreline turbulence intensities to less than or equal to 0.030% at all operating speeds. A large diameter fan and specialized acoustic treatment allow the tunnel to operate at low noise levels of 76.4 dB at 20 m s. To simulate high turbulence, an active turbulence grid can increase turbulence intensities up to 45%. Finally, an open jet configuration enables stereo high-speed fluoroscopy for studying musculoskeletal control in turbulent flow.
我们对动物飞行的理解很大程度上得益于专门为飞行动物设计的风洞。现有的设施可以模拟直线飞行、上升和下降飞行过程中的层流，以及不同高度的层流。然而，动物飞行的大气环境更加复杂。在高海拔地区气流可能是层流且平稳的，但在地面附近则高度湍流，并且阵风会迅速改变风速。为了研究层流和湍流环境中的飞行，斯坦福大学建造了一个用于研究动物和小型飞行器飞行的多功能风洞。该风洞是闭路式的，在一个宽1.0米、高0.82米、长1.73米的矩形试验段中能产生高达50米/秒的空速。风道中的无缝蜂窝结构和滤网，以及精心设计的收缩段，可将所有运行速度下的中心线湍流强度降低至小于或等于0.030%。一个大直径风扇和专门的声学处理使风洞能够在20米/秒的速度下以76.4分贝的低噪音水平运行。为了模拟高湍流，一个主动式湍流格栅可将湍流强度提高至45%。最后，开放式射流配置能够进行立体高速荧光透视，以研究湍流中的肌肉骨骼控制。
