Author(s): Siddharth Manda; Narendran Kumar; Vinay Kumar Varma Kolahalam; Murali Kantharaj
Linked Author(s):
Keywords: Vortex induced vibration; Ventilated trouser (VT); Perforated shroud; Semi active control method
Abstract: The marine structures are commonly subjected to flow induced vibrations also known as Vortex induced vibration (VIV). Significant and critical evaluations were made for many years by researchers to minimize the vibrations in structures that undergo VIV, particularly in the field of offshore structures. Therefore, significance of study in the field of VIV has increased termondously. The present study focuses on the experimental investigations of elastically mounted circular cylinder using Ventilated Trouser (VT) to suppress VIV. The present paper gives an overview of the performance of a novel VIV technique to inhibit the response of circular cylinder. Ventilated Trouser (VT) is a typical mesh/net like flexible wrapping used for suppressing VIV. VT is an Omni directional, economical, customisable device which can be retro fitted for the offshore structures/risers, thus preventing the structure from fatigue failure due to VIV. It contains a network of mesh with circular rod-lets embedded in a systematic arrangement wounded around the model. The experiments were performed in towing tank facility in Department of Ocean Engineering, IIT Madras, India. The primary objective of the present investigation is to suppress VIV using VT around the cylinder at high Re regime, ranging from (0.22-2.50) x10 5. Drag forces acting on cylinder are measured along with oscillations for cylinder shrouded with and without VT. Parametric investigations were also carried out by varying the spacing of rod lets and space sizes of mesh net and shrouding diameters around the cylinder. From the measurements it is observed that cylinder with VT of mesh spacing 75mm at a radial spacing of twice the diameter of bare cylinder suppresses VIV by 97%and drag force by 40%at Re of 1.2x10 5.
Year: 2016