A low-cost wind tunnel for bird flight experiments

A blower-type wind tunnel for physiological bird flight experiments has been developed, constructed and evaluated. Since the birds to be investigated are rather big (Northern Bald Ibis, Geronticus eremita), the cross-sectional area of the test section measures 2.5 m x 1.5 m. The maximum achievable flow speed is approximately 16 ms(-1). The wind tunnel exhibits a flexible outlet nozzle to provide up- and downdraft to allow for gliding and climbing flights. The current paper describes in detail the layout, design and construction of the wind tunnel including its control. Numerical simulations of the flow and measurements of the velocity distribution in the test section are presented. Apart from a non-homogeneous flow region in the mixing layer at the boundaries of the free jet, the test section exhibits a very even velocity distribution; the local speed deviates by less than two percent from the mean velocity. The turbulence intensity inside the test section was measured to be between 1 and 2%. As a constraint, a limited budget was available for the project. Four northern bald ibises were hand-raised and trained to fly in the wind tunnel.

Automated summary

This paper provides a detailed description of the layout, design, and construction of a blower-type wind tunnel used for physiological bird flight experiments. The wind tunnel performs well according to numerical simulations and measurements of velocity distribution, with a relatively homogeneous flow and low turbulence intensity. The wind tunnel is able to accommodate large birds and has a flexible outlet nozzle to allow for various flight maneuvers.