Experimental electro-hydrodynamic investigation of flag-based energy harvesting in the wake of inverted C-shape cylinder (original) (raw)
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Dr. Usman Latif, 2023
In this study, the effect of asymmetric wake flow regime of two side-by-side cylindrical bluff bodies on power output is experimentally examined by using a piezoelectric flag. Different synchronization modes of the flag with wake flow are observed. It is demonstrated that the streamwise gap between the flag and cylinders (G x), and the center-to-center gap between cylinders have a significant impact on the flag's dynamical behavior that results in a fluctuation in the power output of the piezoelectric flag. The levels of output power are analyzed by varying the G x and the cross-stream or lateral gap (N/d) between the two cylinders. N/d values from 1.0 to 2.0 for different values of G x (2.0 ≤ G x ≤ 4.0) are experimentally tested. The comparison of the flapping response at each point is made to ascertain the impact of the harvester's dynamic behavior on the output energy. The power generated at each point is recorded for all cases and a comparative analysis is made to find the optimal configuration. Limited research is conducted in the past to enhance the energy output by using the bluff body with the improved wake dynamics. Hence, two cylinders are employed in a uniform flow and crosswise gap between cylinders is varied to change the characteristics of the wake region. The cylinder arrangement with N/d = 1.0, shows continuous oscillations and higher output power persisting for 2.0 ≤ G x ≤ 4.0. The monotonic rise in power output is observed till G x = 4.0. The stated configurations with N/d = 1.0 gives a significant advantage over a singlecylinder-based energy harvester as a kinetic source of fluid energy harvester from the flowing fluid. The output power became almost doubled with an increase of 95% approximately using side-by-side arrangement.
Wake flow effects on the energy harvesting characteristics of piezoelectric tandem flags
AIP, 2022
In this study, we experimentally investigate the effects of the interaction of piezoelectric flags in the tandem configuration on energy harvesting efficiency. The flags are placed in wake flow behind the bluff body and their flapping behaviors are examined. The experiments are performed in a low-speed water tunnel by varying the flow velocity and streamwise gap behind an inverted C-shape cylinder to analyze the effect of wake flow on amplitude, flapping frequency, and harvested power by the piezoelectric flags. Threshold values for energy harvesting of the streamwise gap and freestream velocity are found to be the same for both flags i.e. 1.5 and 0.18m/s, respectively. While analyzing the dynamical behaviors of the flags, inverted drafting phenomenon is observed in flags: the flapping amplitude of the rear flag is increased by excitation from the vortices and wake of the front flag. This kind of interaction helps out in boosting the energy harvesting efficiency based on the random excitations with high amplitude of rear flag. Results show, as the streamwise gap in-between the flags changes, the influence of the front flag on downstream flag alters and dynamical behavior of front flag show variation when the distance between bluff body and front flag changes. The highest power is also obtained for the rear flag at streamwise gap equals to 1.75 and freestream velocity of 0.26m/s. The tandem configuration produces 216% more power and remarkably improved the energy harvesting efficiency as compared to the single flag energy harvester.
Experimental hydrodynamic investigations on the effectiveness of inverted flag-based piezoelectric energy harvester in the wake of bluff body, 2022
The flapping motion and energy harvesting performance of an inverted flag in the wake of a bluff body are experimentally studied. The experimental measurements are carried out by changing the bending rigidity, streamwise gap (which represents the distance from the bluff body to the tip of the flag), and Reynolds number to explore their impact on the flapping dynamics and power generated by the piezoelectric flag. The optimal values of the Reynolds number, bending rigidity, and streamwise gap are determined based on the power generated. Variation in the flapping modes ranging from continuous to deflected mode is observed. The results show that the inverted flag having a high peak-to-peak amplitude is preferred for piezoelectric energy harvesting as it produces high strain energy. It is also demonstrated that the vortices shed by the upstream bluff body have a strong effect on the flapping amplitude of the downstream inverted flag. This research would help in determining the most effective streamwise position of the inverted flag behind the bluff body and bending rigidity for generating voltage at low Reynolds numbers.
Design Feasibility of a Vortex Induced Vibration Based Hydro-Kinetic Energy Harvesting System
2011
Abstract The vortex induced vibration (VIV) based power generating system discussed in this paper is a new concept in power generation from fluid flows in oceans, rivers and streams. The possibility of harnessing energy from the vibrations incurred in a bluff body due to the phenomenon known as VIV, in which motion is induced on a body facing an external flow due to the periodic irregularities in the flow caused by boundary layer separation is explored.
International Journal of Low-Carbon Technologies, 2020
Renewable energies could be a good solution to the problems associated with fossil fuels. The storage of wind energy by means of small-scale devices rather than large-scale turbines is a topic that has gained lots of interest. In this study, a compact device is proposed to harvest wind energy and transform it into electrical energy, by means of oscillations of a magnet into a coil, using the concept of vortex-induced vibration (VIV) behind a barrier. For a more comprehensive investigation, this system is studied from two viewpoints of fluid mechanics (without magnet) and power generation (with the magnet). For this purpose, an oscillating plate hinging on one side and three barriers with different geometrical shapes including cylindrical, triangular and rectangular barriers are used. In addition to the effect of barrier geometry, the impacts of various barriers dimensions, the distance between the plate and the barriers as well as inclination angle of the plate with respect to the h...
Computational analysis of inverted flag-based energy harvester in the wake of cylindrical bluff body
Ocean Engineering, 2023
In the current study, the penalty immersed boundary method (PIBM) is used to numerically analyze the flapping motion of an inverted flag, placed behind a bluff body using two-dimensional viscous flow. Direct numerical simulations (DNS) are carried out by changing the Reynolds number, bending stiffness, and streamwise gap (which represents the distance from the bluff body to the fixed end of the flag) behind the inverted D-shape cylinder to find their impact on the peak-to-peak amplitude, flapping frequency of the flag. The optimal values of the stated parameters are determined and explained in how the change in geometric and flow parameters affects the flapping behavior which has an ultimate impact on energy output. The addition of a bluff body caused the high strain due to higher bending modes and curvature in the flag. It is also shown that the alternating vortical flow structures have a strong influence on the dynamical behavior of the inverted flag placed inside the wake region of an inverted D-shape cylinder. Relationships between flow velocity, streamwise gap, and the flag's bending rigidity highlight consistent trends for the enhancement of energy production. Additionally, the lateral position of an inverted flag and its effect on vorticity and energy harvesting is discussed in detail with their power spectra to find the maximum amplitude and corresponding drag force. This research would help in concluding the optimal parameters of the inverted flag for the highest energy generation behind the bluff body.
Energies
The aim of this work is to design a piezoelectric power generation system that extracts power from the vibration of a cantilever beam. A semi-cylinder placed in a water stream and attached to the beam is excited into vortex-induced vibrations (VIV), which triggers the piezoelectric deformation. The mechanical system is modelled using parametric equations based on Hamilton’s extended principle for the cantilever beam and the modified Van der Pol model for the bluff body (the semi-cylinder). These equations are simulated using the MATLAB software. The dimensions of the model, the flow velocity and the resistance are treated as design parameters and an optimization study is conducted using MATLAB to determine the combination of optimal values at which maximum power is extracted. The key findings of this research lie in the identification of the effect of changing the design parameters on output power. In addition to the numerical simulation, a finite element analysis is carried out on ...