F. Oviedo-Tolentino

Fluid Forces on a Flexible Circular Cylinder in Vortex-Induced Vibrations

In this work fluid forces acting on a flexible circular cylinder in Vortex-Induced Vibrations (VIV) were studied. An experimental campaing was conducted at low mass-damping ratio (\(\mathrm {m_{cil}^{*}\zeta }\) = 0.126) covering the entire lock-in region. The dynamic response of the cylinder was computed using the Particle Tracking Velocimetry technique on the cylinder free end tip. Drag and lift coefficients (\(C_{D}\) and \(C_{L}\)) were determined using the experimental data from the cylinder response in a spring-mass-damping model. Results show that \(C_{L}\) is one order of magnitude greater than \(C_{D}\). Strong cylinder oscillations are associated with a flow pattern showing two vortex center lines corresponding mainly at the upper end of the initial region.

Effect of the Inlet Flow Angle on the Vortex Induced Vibration of a Collinear Array of Flexible Cylinders

In this work an experimental study of vortex-induced vibration (VIV) was carried out in an collinear array of ten identical cylinders. This investigation was conducted with a mass ratio (\(m^{*}\xi =0.13\)) and a blockage ratio (\(W/D<1\%\)). The inlet flow angle was fixed to \(30^{\circ }\) and the leading cylinder vibration amplitude was compared under the condition of \(0^{\circ }\) inlet flow angle. The free-end cylinders had two degrees of freedom with identical in-line and cross-flow natural frequencies in still fluid medium. The experimental essays were performed in a water tunnel in the lock-in region (\(90<Re<450\)). The results show that the cross-flow vibration amplitude is 68 % reduced when the inlet flow angle increases to \(30^{\circ }\).