Effect of blockage on free vibration of a circular cylinder at low Re

Abstract

SUMMARYThe effect of the blockage on vortex-induced vibrations of a circular cylinder of low non-dimensional mass (m * = 10) in the laminar flow regime is investigated in detail. A stabilized space-time finite element formulation is utilized to solve the incompressible flow equations in primitive variables form in two dimensions. The transverse response of the cylinder is found to be hysteretic at both ends of synchronization/lock-in region for 5% blockage. However, for the 1% blockage hysteresis occurs only at the higher Re end of synchronization/lock-in region. Computations are carried out at other blockages to understand its effect on the hysteretic behavior. The hysteresis loop at the lower Re end of the synchronization decreases with decrease in blockage and is completely eliminated for blockage of 2.5% and less. On the other hand, hysteresis persists for all values of blockage at the higher Re end of synchronization/lock-in. Although the peak transverse oscillation amplitude is found to be same for all blockage (∼ 0.6D), the peak value of the aerodynamic coefficients vary significantly with blockage. The r.m.s. values show lesser variation with blockage. The effect of streamwise extent of computational domain on hysteretic behavior is also studied. The phase between the lift force and transverse displacement shows a jump of almost 180 • at, approximately, the middle of the synchronization region. This jump is not hysteretic and is independent of blockage.

On the Response of a Freely Vibrating Thick Elliptic Cylinder of Low Mass Ratio

“…The earlier studies on undamped VIV concerning circular (Prasanth and Mittal 2008) and elliptic (Navrose et al 2014) cylinders of m * = 10 suggest that a hysteresis-free regime exists near the onset of lock-in under certain conditions (e.g., low blockage or low m * ). However, flow and body motion were hysteretic (secondary) near the closure of lock-in.…”

“…However, flow and body motion were hysteretic (secondary) near the closure of lock-in. The choice of m * = 1 in the present study is motivated by the conclusions of Jauvtis and Williamson (2004) and findings of Prasanth and Mittal (2008) and Navrose et al (2014) for m * = 10>6. A fundamental question regarding the hysteretic behaviour of oscillators having curved contours therefore relates to conditions that might suppress secondary hysteresis.…”

“…Therefore, the precise number 16.91 is the product of the reference FN and reference Re. This kind of set-up has been used earlier for a circle by Willden and Graham (2006), Prasanth and Mittal (2008), Bahmani and Akbari (2010) and for a square by Sen and Mittal (2011). In the present work, U A block-structured non-uniform mesh consisting of 7437 nodes and 7236 bilinear quadrilateral elements is used for domain discretization.…”

Layout Optimization Design of Two Vortex Induced Piezoelectric Energy Converters (VIPECs) Using the Combined Kriging Surrogate Model and Particle Swarm Optimization Method

“…Each VIPEC's center was 10 D away from its nearest side wall. Thus, the whole computational domain had a size of (40 + a) D× (20 + b) D, which is large enough to eliminate the influence of walls on the flow field [17].…”

Numerical Computation of Fluid-Structure Interaction on Isolated Stationary Cylinder with Elastic Surface

“…The flow around circular cylinders has been studied by various researchers in the past [1][2][3][4][5][6][7][8][9][10][11][12] . The main issues in the latter applications are to reduce the unsteady fluid forces on the object.…”