Vibration Of Square Cylinder Research Articles

Effect of pulsatile flow on hydrodynamic characteristics of vortex induced vibration of square cylinder

Vortex Induced Vibration (VIV) of an elastically mounted square cylinder subjected to pulsatile flow conditions is solved numerically for Reynolds number (Re = 100) and low mass ratio (Mred = 2). The focus of the present work is on investigating the effects of pulsatile frequency on the response of the cylinder. Effects of variation in Keulegan-Carpenter number, KC ϵ [10- 40, step of 10] and reduced velocity, Ured, ϵ [3-25, step of 1], on hydrodynamic characteristics is studied. An Arbitrary-Lagrangian Euler (ALE) formulation is used to write the governing equations in two space dimensions. Maximum cross-flow displacement is observed for Ured = 7 for KC=10. It is found that, the lock-in becomes slightly wider with increase in KC. Different regimes like Initial Branch , Lower Branch and desynchronized have been identified for all KC. Beyond KC = 20, cylinder starts to vibrate with the pulsatile frequency. Moreover, in the Lock-in zone flow amplitude is not always enhanced, and it sometimes gets reduced. This is basically due to state of synchronization between displacement and forcing. For all KCs, in-phase and out-of-phase regimes were also identified for X and Y-direction displacements. Wake width and vortex strength are maximum at the lock-in.

Hydrodynamic and heat transfer characteristics of vortex- induced vibration of square cylinder with various flow approach angle

In this work, the effect of flow approach angle (α) on forced convective heat transfer from an elastically mounted vibrating rigid square cylinder is studied numerically. The Navier-Stokes equations along with the two-dimensional equation of motion of elastically mounted rigid square cylinder are solved using finite difference method. An Arbitrary Lagrangian Euler (ALE) method is used to capture the relation between fluid flow and vibrating cylinder. Numerical simulations are conducted for different Reynolds number ∈ [60–100], reduced velocity (Ured∈[3−8]) and flow approach angle (α∈[0o−45o]). Prandtl number (Pr) = 7.1 and Reduced mass (Mred) = 2 are kept constant and damping coefficient, ξ' = 0. The detailed kinematics of the flow and temperature fields is visualized in terms of instantaneous vorticity and isotherm contours. Examining the distribution of local Nusselt number (Nu) along the faces of the heated square develops further detailed insights. Overall gross characteristics are reported in terms of the time average drag coefficient and Nusselt number. Average Nusselt number (Nu‾) scales linearly with Reynolds number (Re) while both Ured and α has quadratic relationship. Different vortex shedding modes viz; 2S, 2S* and P + S have also been observed for different flow approach angle. At α =30o, the average Nusselt number (Nu‾) is maximum for Ured = 6, 8 and at all Reynolds numbers as the flow shows 2S* mode of vortex shedding.

Piezoelectric Wind Energy Harvesting from Self-Excited Vibration of Square Cylinder

Self-excited vibration of a square cylinder has been considered as an effective way in harvesting piezoelectric wind energy. In present work, both of the vortex-induced vibration and unstable galloping phenomenon process are investigated in a reduced velocity (Ur=U/ωn·D) range of4≤Ur≤20with load resistance ranging in100 Ω≤R≤1 MΩ. The vortex-induced vibration covers presynchronization, synchronization, and postsynchronization branches. An aeroelectromechanical model is given to describe the coupling of the dynamic equation of the fluid-structure interaction and the equation of Gauss law. The effects of load resistance are investigated in both the open-circuit and close-circuit system by a linear analysis, which covers the parameters of the transverse displacement, aerodynamic force, output voltage, and harvested power utilized to measure the efficiency of the system. The highest level of the transverse displacement and the maximum value of harvested power of synchronization branch during the vortex-induced vibration and galloping are obtained. The results show that the large-amplitude galloping at high wind speeds can generate energy. Additionally, energy can be harvested by utilization of the lock-in phenomenon of vortex-induced vibration under low wind speed.