Experimental Investigation of Vortex-Induced Vibration of a Circular Cylinder Mounted on a Cantilever Beam

Experimental investigation of vortex-induced vibration of a bluff body usually requires the use of air bearings that allow motion with negligible friction. The use of air bearings allows us to conduct experiment at very low mass damping. However, air bearing systems are costly and require continuous supply of pressurized air. The pressurized air is supplied through a tube that can act as a source of external damping as the tube vibrates with the system. In this work, we present an alternate and cheap method of conducting vortex-induced vibration experiments while keeping very low mass damping. We use a cantilever beam for the elastic support of the bluff body. The cantilever beam provides restoring force and frictionless motion for the system. In our experiments, we tested one long cantilever beam made of mild steel and one short cantilever beam made of stainless steel. We compared the vibration response of the circular cylinder with the existing literature. For sufficiently long cantilever beams, the vibration response is found to be comparable to that of an air bearing mounted cylinder free to vibrate transverse to the flow. In case of MS cantilever beam, three response branches, initial, upper, and lower branches, are observed. The maximum amplitude of vibration occurs at \(U^{ * } \, = \,4.92,\) and it is \(A_{{{\text{max}}}}^{ * } \, = \,0.79D.\) For SS cantilever beam, only two response branches, initial and lower, are observed, and the peak amplitude of vibration \(A_{max}^{*} = 0.70D\) occurs in the lower branch at \(U^{ * } \, = \,5.26.\) It is observed that on reducing the length of the cantilever beam, the peak of the amplitude reduces.