Experimental study of aerodynamic damping in arrays of vibrating cantilevers

Abstract

Cantilever structures vibrating in a fluid are encountered in numerous engineering applications. The aerodynamic loading from a fluid can have a large effect on both the resonance frequency and damping, and has been the subject of numerous studies. The aerodynamic loading on a single beam is altered when multiple beams are configured in an array. In such situations, neighboring beams interact through the fluid and their dynamic behavior is modified. In this work, aerodynamic interactions between neighboring cantilever beams operating near their first resonance mode and vibrating at amplitudes comparable to their widths are experimentally explored. The degree to which two beams become coupled through the fluid is found to be sensitive to vibration amplitude and proximity of neighboring components in the array. The cantilever beams considered are slender piezoelectric fans (approximately 6 cm in length), and are caused to vibrate in-phase and out-of-phase at frequencies near their fundamental resonance values. Aerodynamic damping is expressed in terms of the quality factor for two different array configurations and estimated for both in-phase and out-of-phase conditions. The two array configurations considered are for neighboring fans placed face-to-face and edge-to-edge. It is found that the damping is greatly influenced by proximity of neighboring fans and phase difference. For the face-to-face configuration, a reduction in damping is observed for in-phase vibration, while it is greatly increased for out-of-phase vibration; the opposite effect is seen for the edge-to-edge configuration. The resonance frequencies also show a dependence on the phase difference, but these changes are small compared to those observed for damping. Correlations are developed based on the experimental data which can be used to predict the aerodynamic damping in arrays of vibrating cantilevers. The distance at which the beams no longer interact is quantified for both array configurations.Understanding the fluid interactions between neighboring vibrating beams is essential for predicting the dynamic behavior of such arrays and designing them for practical applications.

Aerodynamic damping of sidewall bounded oscillating cantilevers

“…As it can be gathered from an understanding of drag, as the velocity increases it causes the drag resistance to increase. This has also been demonstrated in other studies using similar systems by Kimber et al (2009a), Bidkar et al (2009), and Porfiri and coworkers (Aureli et al, 2012;Facci and Porfiri, 2013). This further reinforces that the non-linear response compared to the linear voltage input is not a product of some unknown systematic error.…”

Optimum tip gap and orientation of multi-piezofan for heat transfer enhancement of finned heat sink in microelectronic cooling

“…Hosaka and Itao [12] and Basak and Raman [13] reported that the vibration characteristics of a vibrating cantilever were altered by the presence of a second oscillating beam depending on the vibration amplitude as well as the pitch, and the phase difference between the neighboring cantilevers. These findings were also confirmed experimentally by Kimber and co-workers [14,15] who studied the fluidic coupling between piezofans.…”

“…While most of the researchers focused on the use of single piezofan, only few works [4,8,[12][13][14][15][16] were reported on multipiezofan which has important practical applications. Few researchers were interested in the combination of piezofan and finned heat sink [17][18][19], which was proved to be relatively excellent.…”

Experimental investigation of added mass effects on a hydrofoil under cavitation conditions

“…They also found that the added mass effect on a cylinder was overestimated when using the same analytical method. More recently, Kimber et al (2009) studied the interaction between two cantilever structures vibrating in air for various configurations. They verified that resonance frequencies and aerodynamic damping depend on the vibrating phase difference between the plates.…”