vortex-induced vibration

Global energy demand will increase by 1.8% annually between 2000 and 2030. Carbon dioxide gas increases by 1.2% per year. Lack of energy and air pollution are two big problems of humanity. The use of renewable energy sources with the least environmental pollution is very important. Attention to the low pollution effect of harvesting energy from the wind has led most researchers to research this type of energy. Wind energy is one of the renewable energy sources, the new generation of bladeless wind turbines is based on a flexible structure. This article is an overview of 67 fundamental researches in this new field that are being investigated by researchers, which are based on validity and practical testing. The FSI calculations made in the articles have been filtered, the studies made are mainly to optimize the use of renewable energy of the bladeless turbine and check one or two parameters. The simulated wind turbine model is without blades, almost all parameters effective in energy harvesting in these turbines have been investigated, and an adjustment system has been used to increase the productivity hours of the wind turbine per year.

Vortex-induced vibration is a critical phenomenon that occurs in offshore structures and causes fatigue and damage to these structures. Previous studies show that these structures show complex and sometimes non-linear behavior. This study uses a rigid cylinder with non-linear support to evaluate the hydrodynamic parameters in these systems. The amount of non-linearity of the support has been changed, and its effect on the hydrodynamic parameters of the system has been investigated. The displacement and velocity of the cylinder were obtained by solving the two-dimensional Reynolds averaged Navier-Stokes and cylinder motion equations. The lift, potential, and vortex coefficients were calculated. Finally, the Strouhal number was determined. The results show that the system's behavior consists of two branches. In branch 1, the motion amplitude of the cylinder is small, but in branch 2, its amplitude is multiplied. By increasing the non-linearity of the support, the range of branch 2 becomes smaller, and the velocity of the cylinder oscillation increases. Raising the support non-linearity reduces the lift force and Strouhal number

Leveraging artificial intelligence to forecast heat transfer characteristics across diverse industries holds significant potential for improving thermal equipment design, increasing heat transfer efficiency, optimizing cooling systems, and reducing energy consumption. The main contribution and purpose of the current study is predicting the Nusselt number in the context of turbulent flow-induced vibration around a heated cylinder experiencing unconfined oscillations along both streamwise and transverse axes. The anticipation of the Nusselt number relies on transverse and streamwise displacements of the oscillating cylinder and encompasses three distinct scenarios: displacement input in the x-direction, displacement input in the y-direction, and comprehensive amalgamation of both x and y inputs. This prediction is achieved through a sophisticated deep long short-term memory network, meticulously crafted and fine-tuned using a particle swarm optimization algorithm. The results highlight the effectiveness of the optimized networks across various inputs, with the highest predictive precision observed when employing combined x and y inputs. The correlation coefficients within the test segment are as follows: 0.967 for x input, 0.961 for y input, and 0.975 for combined x and y inputs. By applying the methodology elucidated in this study, the forecasting of heat transfer characteristics for structures subjected to fluid flow emerges as a feasible possibility.

The present study numerically evaluates vortex-induced vibration (VIV) for an electrically conductive fluid around a cylinder on an elastic support. The flow is subjected to a uniform magnetic field in the z-direction to evaluate the VIV attenuation performance of this open-loop active control method. To analyze this fluid-structure interaction (FSI) problem, the finite volume method (FVM) was employed based on the SIMPLE algorithm to solve the governing continuity and momentum equations of the fluid flow and an explicit integration method to solve the motion equations of the rigid structure. Simulations were carried out at reduced velocities of 2-9 and different Stuart numbers. The simulation results demonstrated that the magnetic field was significantly effective and wholly (100%) suppressed transverse and longitudinal VIVs. A rise in the magnetic field magnitude eliminated vortex shedding for all the reduced velocities, leading to a symmetric wake. The symmetric vortex even disappeared above the critical Stuart number.

In this paper, the active flow control of flow-induced vibration of a circular cylinder placed in the isothermal channel affected by jet injection is studied. The effect of flow injection on heat transfer inside the channel has also been examined. For this purpose, three slots are placed symmetrically in the upper and lower walls of the channel at distances 0, D, and 4D where D is the diameter of the cylinder from the side surface. The main innovation of the present study is to evaluate the effectiveness of the proposed flow control method in terms of channel height. For this purpose, 6 channels with heights of 5.5D, 6D, 7D, 8D, 9D, and 10D are considered to perform fluid-solid interaction simulations. The finite element method has been used to solve the flow and energy equations. For coupling the movement of the cylinder with the flow field, the dynamic mesh method is used. Numerical results show that for all channels with different heights, jet injection, either unilaterally or bilaterally, from slot 3, has no effect on displacement because the distance of the jet from the cylinder is large. By increasing the height of the channel, the injection velocity must be increased to completely reduce the oscillations of the cylinder.

Immersed boundary method is a novel and efficient tool for solving fluid-structure interaction problems. One of important fluid-structure interaction problems is vortex-induced vibrations of cylinders. In this study, we want to introduce immersed boundary method. Philosophy, advantages, disadvantages and applications of the method will be presented. Because of wide range of applications of this method and for not losing focus, we shall limit our study only to vortex-induced vibrations. Next, details of governing equations of immersed boundary method and their discretization will be introduced. Iterative immersed boundary algorithm which has been used for vortex-induced vibrations before, will be used to solve governing equations. Finally, implementation and coding requirements will be discussed. This paper is organized in a way so readers can obtain a comprehensive understanding of the method behavior in fluid-structure interaction problems, especially vortex-induced vibrations. Considering the benefits of immersed boundary method, it has the potential to become the main method for analyzing fluid-structure interaction problems. These benefits are considerable enough that makes the implementation of the method justifiable.

In this paper, a two-dimensional numerical simulation is applied to study the Vortex-Induced Vibrations (VIV) of an elastically mounted rigid circular cylinder beneath a free surface of fluid. The effect of free surface in laminar flow (60 < Re < 130) with Fr=0.2 is investigated with considering two Gap-Ratios of 2.5, 1.5. The natural structural frequency of oscillator is assumed to match the vortex shedding frequency for a stationary cylinder at Re=100. Discretization of flow equations based on the Finite Volume method was implemented in CFD commercial software Ansys Fluent 14.0. Simulations of VIV and Free Surface of fluid flow have separately shown good agreement with previous results. This paper is the second part of an investigation about effects of Free Surface of fluid on VIV phenomena. The effects of Free Surface is investigated with using a comparison of vortex shedding modes and non-dimensional frequency diagrams for the two gap-ratios. With approaching cylinder to free surface, results shows changing type of vortex shedding modes, abatement in lock-in region, increasing Strouhal number and non-dimensional frequency ratio.

In this study, the geometrical effect of circular cylinder with different sectors on energy harvesting of vortex induced vibration is investigated numerically. According to Von Karman vortex shedding phenomenon, the flow passes over a bluff body and as the results create vibration, can use this phenomenon with energy extraction and converting it into desired energy. In this paper, the focus was on discovering a cylinder geometry with more vibration than the base cylinder (circular cylinder); for this purpose, circular cylinder with different sectors, including  ratio of 0.5, 0.6, 0.7, 0.8, 0.9, and 1 in two direction of arches frontal (AF) incoming flow and flat frontal (FF) incoming flow have been studied at Reynolds numbers of 100 and 200. Investigations have been carried out in the fluid and vibration field. In the fluid field, the aerodynamics forces are obtained on the cylinder with the help of computational fluid dynamics (CFD) and in the vibration field, by writing program in the Maple software, the displacement of the cylinder and, finally, recoverable potential power of the fluid were calculated. The results show that, at Reynolds numbers of 100 and 200, respectively, circular cylinder with and  sectors in the placement direction of FF get the maximum extraction power of fluid and compared to the circular cylinder at Reynolds numbers of 100 and 200, respectively, 3.5 and 5.3 more times power harvesting. Also, in the same sectors cylinder, the cylinder with FF placement direction always has more power generation than the cylinder with AF placement direction.

In the vortex-induced vibration the structure interacts with the fluid flow that results in the vibration of the structure and sometimes leads to the destruction of it. In this paper, the effect of the vortex-induced vibration on one and two cylinder(s) in the rotating and non-rotating states are studied, numerically. For the case of single non-rotating cylinder, the effect of the reduced velocity and damping ratio on the displacement and velocity of circular cylinder and also on the lift coefficient and its components are investigated. The cylinder displacement decreases by increasing the damping ratio. The vortex shedding pattern for all examined reduced velocity and damping ratio is in the 2S mode. In all cases, two patterns of vibration, harmonic and beating phenomena, can be observed. The maximum value of the vibration amplitude is related to the reduced velocity of 4 for ζ= 0 and the minimum is belonged to the reduced velocity of 3. For the case of rotating cylinder, it is observed that the rotation of cylinder(s) affects the vortex shedding pattern and their strength, significantly. Therefore, the fluctuation of lift coefficient and vibration of cylinder(s) are reduced considerably.

In this paper, a two-dimensional numerical simulation is applied to study the vortex-induced vibrations of an elastically mounted rigid circular cylinder beneath a free surface of fluid. The effect of free surface in laminar flow is investigated with considering two gap-ratios. The natural structural frequency of oscillator is assumed to match the vortex shedding frequency for a stationary cylinder at Re=100. Discretization of flow equations based on the Finite Volume method was implemented in computational fluid dynamics commercial software Ansys Fluent 14.0. User Defined Function hooked in the Software is given to couple the motion of cylinder to flow motion. For simulation of free surface, volume of fluid method is used. The effect of free surface is investigated with using a comparison of transverse displacement diagrams and aerodynamics coefficients diagrams for the two gap-ratios. With approaching cylinder to free surface, results show an abatement in the lock-in region and the amplitude of the oscillations and aerodynamics coefficients are changed depending on the Reynolds location branch.