Experimental study on proximity interference induced vibration of two staggered square prisms in turbulent boundary layer flow

Slender structures placed close to each other could greatly magnify the dynamic response due to interference effects. This paper presents the results of experimental studies of the proximity interference induced vibration of two identical square prisms in a turbulent boundary layer to clarify its excitation mechanism. The upstream interfering prism was static, while the principal prism was dynamic and free to vibrate only in the crosswind direction. The divergent vibration behavior at the critical interfered location was examined in detail. Based on the time-resolved particle image velocimetry (TR-PIV) technique and unsteady pressure measurement, the vortex shedding process and corresponding pressure distribution of the dynamic principal prism were described by examining their correlation with the motion time histories. The biased gap flow between the two prisms was found to control the vibration of the dynamic principal prism. The interaction between the vortex shedding in the wake of the dynamic principal prism and the gap flow is dramatically intensified with increasing wind velocity. Such effects create a large fluctuating lift force on the dynamic principal prism at high reduced wind velocity, compared with measurement taken with two static prisms, which drives the prism to undergo a divergent crosswind response.