A novel elastic suspension system for wind tunnel section model studies

A novel three-degree-of-freedom (DOF) suspension system has been developed for the wind-tunnel section model study of wind-excited vibrations of flexible structures. This system enables simultaneous vertical, horizontal, and torsional motion of the suspended model and captures the effect of coupling between different degrees of freedom of a flexible structure immersed in a dynamic flow field. It utilizes pneumatic bushings that glide along polished steel shafts in the vertical and horizontal directions of motion. Torsional assemblies are used to generate torsional motion of the model. Force measurement is accomplished with compact straingage type force transducers that allow precise placement for accurate measurements. Static measurements are also possible by restraining the desired DOF. Vibration frequencies of the system are tuned with combinations of springs. System damping is low due to the low-friction pneumatic bushings, restriction of coil spring wire to small diameters, and highly polished stainless steel guide shafts. Relatively large displacements can be generated by the suspension system, if required. Results from two experiments on aeroelastic studies are presented to demonstrate the functioning of the suspension system. The effect of including the lateral motion on the coupled-mode response is illustrated.