scholarly journals Modelling of a Flow-Induced Oscillation, Two-Cylinder, Hydrokinetic Energy Converter Based on Experimental Data

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 827
Author(s):  
Yanfang Lv ◽  
Liping Sun ◽  
Michael M. Bernitsas ◽  
Mengjie Jiang ◽  
Hai Sun
Keyword(s):  
Experimental Data ◽  
Prediction Model ◽  
Flow Velocity ◽  
Surrogate Model ◽  
Damping Ratio ◽  
Predictive Tool ◽  
Power Harvesting ◽  
Hydrokinetic Energy ◽  
Tandem Cylinders ◽  
Spacing Ratio

The VIVACE Converter consists of cylindrical oscillators in tandem subjected to transverse flow-induced oscillations (FIOs) that can be improved by varying the system parameters for a given in-flow velocity: damping, stiffness, and in-flow center-to-center spacing. Compared to a single isolated cylinder, tandem cylinders can harness more hydrokinetic energy due to synergy in FIO. Experimental and numerical methods have been utilized to analyze the FIO and energy harnessing of VIVACE. A surrogate-based model of two tandem cylinders is developed to predict the power harvesting and corresponding efficiency by introducing a backpropagation neural network. It is then utilized to reduce excessive experimental or computational testing. The effects of spacing, damping, and stiffness on harvested power and efficiency of the established prediction-model are analyzed. At each selected flow velocity, optimization results of power harvesting using the prediction-model are calculated under different combinations of damping and stiffness. The main conclusions are: (1) The surrogate model, built on extensive experimental data for tandem cylinders, can predict the cylinder oscillatory response accurately. (2) Increasing the damping ratio range from 0–0.24 to 0–0.30 is beneficial for improving power efficiency, but has no significant effect on power harvesting. (3) In galloping, a spacing ratio of 1.57 has the highest optimal harnessed power and efficiency compared with other spacing values. (4) Two tandem cylinders can harness 2.01–4.67 times the optimal power of an isolated cylinder. In addition, the former can achieve 1.46–4.01 times the efficiency of the latter. (5) The surrogate model is an efficient predictive tool defining parameters of the Converter for improved energy acquisition.

Modeling of a Hydrokinetic Energy Converter With Two Tandem Cylinders in Flow-Induced Oscillations

2020 ◽  
Author(s):  
Yanfang Lv ◽  
Michael M. Bernitsas ◽  
Sun Hai
Keyword(s):  
Bp Neural Network ◽  
Power Efficiency ◽  
Present Model ◽  
Damping Ratio ◽  
Bp Network ◽  
Power Harvesting ◽  
Hydrokinetic Energy ◽  
Tandem Cylinders ◽  
Vortex Induced Vibrations ◽  
Mass Spring

Abstract Flow Induced Oscillations (FIO) of tandem cylinders can be enhanced to harness hydrokinetic energy by varying the system parameters. In general, the Converter consists of two mass–spring–damper oscillators subjected to transverse FIOs and specifically Vortex Induced Vibrations and galloping. These FIOs are strongly influenced by variations of the inflow velocity, damping, stiffness, mass and in-flow center-to-center spacing L between two tandem cylinders. In turn, those influence the harnessed power and efficiency of the Converter. In previous experiments, the interactions between the cylinders were proven to be beneficial for the synergy of the cylinders. In this paper, modeling of tandem-cylinder converters is studied considering the Converter parameters, aiming at enhancing the cylinder synergy resulting in increased harnessed power by using a backpropagation (BP) neural network. The main conclusions are: (1) The surrogate model is constructed by a BP network using the experimental data to reduce excessive experimentation or computational inaccuracy. The harnessed power at different flow velocities is computed by the present model and is found to be consistent with experimental results not included in the modeling. (2) Increasing the damping ratio (0.20–0.30) of two tandem cylinders is conducive to improve the power efficiency, but has little effect on power harvesting. (3) In galloping, the harnessed power and its corresponding efficiency for the case of L/D = 1.57 perform at a higher level than that of bigger spacing ratios.

Two Tandem Cylinders With Turbulence Stimulation in FIV Power Conversion: CFD With Experimental Verification of Interaction

2017 ◽  
Author(s):  
Wenjun Ding ◽  
Hai Sun ◽  
Wanhai Xu ◽  
Michael M. Bernitsas
Keyword(s):  
Frequency Response ◽  
Conversion Efficiency ◽  
Stokes Equations ◽  
Damping Ratio ◽  
Power Conversion ◽  
Clean Energy ◽  
Amplitude Response ◽  
Response Frequency ◽  
Tandem Cylinders ◽  
Spacing Ratio

Flow induced vibrations of two rough, rigid, tandem-cylinders on springs are investigated for power conversion for Reynolds number 30,000 ≤ Re ≤ 120,000. Passive turbulence control (PTC) in the form of roughness strips is employed to enhance FIV and increase the power harness efficiency of the VIVACE (Vortex Induced Vibration for Aquatic Clean Energy) converter. Numerical simulations are performed using two-dimensional, Unsteady Reynolds-Averaged Navier-Stokes equations with the Spalart-Allmaras turbulence model. The center-to-center spacing ratio d / D of the two cylinders is set as 2.0 or 2.57 with mass ratio m* = 1.343 , damping ratio ζ = 0.26, and stiffness K = 1,200 N/m. Amplitude response, frequency response, interaction, energy harvesting, and conversion efficiency are presented and discussed. The main conclusions are: (1) In the VIV region at Re = 60,000, the amplitude response, frequency response, harnessed power, and power conversion efficiency of the upstream cylinder is the same for the two spacing ratios. Due to the shedding effect, the motion of the downstream cylinder for spacing ratio d/D = 2.0 is more severely suppressed than spacing ratio d/D = 2.57, which reduces the harnessed power and conversion efficiency for the downstream cylinder. (2) In the galloping region at Re = 110,000, due to the different impingement of the shed vortices on the downstream cylinder, the upstream cylinder harnesses more power and has higher energy conversion efficiency for spacing ratio d/D = 2.0 than d/D = 2.57.

The Heat Transport Capacity of Micro Heat Pipes

1998 ◽  
Vol 120 (4) ◽  
pp. 1064-1071 ◽  
Author(s):  
J. M. Ha ◽  
G. P. Peterson
Keyword(s):  
Experimental Data ◽  
Heat Pipe ◽  
Heat Transport ◽  
Heat Pipes ◽  
Original Model ◽  
Semiempirical Model ◽  
Transport Capacity ◽  
Predictive Tool ◽  
Maximum Heat ◽  
Micro Heat Pipes

The original analytical model for predicting the maximum heat transport capacity in micro heat pipes, as developed by Cotter, has been re-evaluated in light of the currently available experimental data. As is the case for most models, the original model assumed a fixed evaporator region and while it yields trends that are consistent with the experimental results, it significantly overpredicts the maximum heat transport capacity. In an effort to provide a more accurate predictive tool, a semi-empirical correlation has been developed. This modified model incorporates the effects of the temporal intrusion of the evaporating region into the adiabatic section of the heat pipe, which occurs as the heat pipe approaches dryout conditions. In so doing, the current model provides a more realistic picture of the actual physical situation. In addition to incorporating these effects, Cotter’s original expression for the liquid flow shape factor has been modified. These modifications are then incorporated into the original model and the results compared with the available experimental data. The results of this comparison indicate that the new semiempirical model significantly improves the correlation between the experimental and predicted results and more accurately represents the actual physical behavior of these devices.

Pressure, Frictional Resistance, and Flow Characteristics of the Partially Wetted Rotating Disk

1968 ◽  
Vol 90 (2) ◽  
pp. 395-404 ◽  
Author(s):  
H. N. Ketola ◽  
J. M. McGrew
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Pressure Gradient ◽  
Flow Characteristics ◽  
Frictional Resistance ◽  
Rotating Disk ◽  
Practical Applications ◽  
Stationary Wall ◽  
Spacing Ratio ◽  
Analytical Expressions

A theory of the partially wetted rotating disk is described and experimental data presented which verify the application of this theory in practical applications. Four different flow regimes may be identified according to the value of the disk Reynolds number and the spacing ratio between the disk and stationary wall. The analytical expressions for prediction of the pressure gradient developed and the frictional resistance are uniquely determined by the disk Reynolds number, spacing ratio, and the degree of wetting of the disk.

scholarly journals Flow-velocity model for hydrokinetic energy availability assessment in the Amazon

2019 ◽  
Vol 42 ◽  
pp. e45703
Author(s):  
Josias da Silva Cruz ◽  
Claudio José Cavalcante Blanco ◽  
Antônio César Pinho Brasil Junior
Keyword(s):  
Flow Velocity ◽  
Amazon Basin ◽  
Velocity Model ◽  
Amazon River ◽  
Data Series ◽  
Flow Rates ◽  
Hydrokinetic Energy ◽  
Historical Series ◽  
Flood Period ◽  
Availability Assessment

The Brazilian hydrological information network does not provide data series of daily velocities. The river velocities are important for the study of hydrokinetic potential. Therefore, the work proposes a model called flow-velocity that estimates the average daily velocity and the distribution of the velocity profile of the cross section of rivers. The model was applied to the Amazon basin, using the highest and lowest flow rates of the historical series. The highest and lowest average velocities found in the Amazon River were 2.27 m s-1 and 0.735 m s-1, respectively. The main contributors to the Amazon River presented average daily velocities close to 2.0 ms-1 for the flood period, but in the dry season these velocities did not exceed 0.5 m s-1. Thus, it was verified that the Amazon River has hydrokinetic potential throughout the year and its tributaries during the flood period.

A Prediction Model of Deflection of Fixing Thin Parts

2012 ◽  
Vol 217-219 ◽  
pp. 1526-1529
Author(s):  
Yu Mei Liu ◽  
Wen Ping Liu ◽  
Zhao Liang Jiang ◽  
Zhi Li
Keyword(s):  
Neural Network ◽  
Experimental Data ◽  
Artificial Neural Network ◽  
Prediction Model ◽  
Simulated Data ◽  
Artificial Neural ◽  
Predicted Values ◽  
Artificial Neural Network Ann ◽  
Abaqus Software

A prediction model of deflection is presented. The Artificial Neural Network (ANN) is adopted, and ANN establishes the mapping relation between the clamping forces and the position of fixing and the value of deflection. The results of simulation of Abaqus software is used for Training and querying an ANN. The predicted values are in agreement with simulated data and experimental data.

Experimental Flow-Induced Vibration Analysis of the Crossflow Past a Single Cylinder and Pairs of Cylinders in Tandem and Side-by-Side

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Roberta Fátima Neumeister ◽  
Adriane Prisco Petry ◽  
Sergio Viçosa Möller
Keyword(s):  
Vibration Amplitude ◽  
Damping Ratio ◽  
Sudden Increase ◽  
Blockage Ratio ◽  
Flow Induced Vibration ◽  
Single Cylinder ◽  
Reference Velocity ◽  
Continuous Wavelets ◽  
Constant Height ◽  
Spacing Ratio

Abstract Flow-induced vibration of a single cylinder and two cylinders in tandem and side-by-side configurations is experimentally investigated in this paper in the subcritical regime. The natural frequency of the system varied from 8.8 Hz to 46.2 Hz. The mass ratio, m*, ranged between 158 and 643 while the damping ratio, ζ, between 0.0005 and 0.009. The pairs of cylinders present a spacing ratio of 1.26 (P/D and L/D). In all cases, one and both cylinders (BV) were free to vibrate. Experiments were performed in an aerodynamic channel with a constant height and a variable width, for the evaluation of the influence of the blockage ratio (BR), using accelerometers and hot wire anemometry. The reference velocity, measured at the entrance of the test section was used to calculate the reduced velocity, Vr = U/fnD, with values from 4 to 132 and the Reynolds number between 3 × 103 and 8 × 104. The root-mean-square-values of the displacement amplitudes, Y/D, were obtained through the integration of the acceleration signals. Fourier and continuous wavelets were employed in the analysis. For a single cylinder free to vibrate, the higher amplitudes occur at two distinct reduced velocities, associated with the vibration modes of the cylinder. The vibration amplitude of a single cylinder increased as the blockage ratio increased, decreasing for the highest blockage ratio investigated. For the case of cylinders in tandem, the presence of the fixed cylinder in the wake of the cylinder free to vibrate amplifies the vibration response at high reduced velocities. When the blockage ratio is increased, a sudden increase in the vibration amplitude is observed. When both cylinders are free to vibrate, the relation between the natural frequencies of both cylinders influences the response amplitudes. In the case with two cylinders side-by-side, the vibration amplitude remains similar to a single cylinder, but when both cylinders are free to vibrate, the presence and the influence of flow bistability is observed.

Boundaries Effects on the Movements of a Sphere Immersed in a Free Surface Flow

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
D. Mirauda ◽  
A. Volpe Plantamura ◽  
S. Malavasi
Keyword(s):  
Experimental Data ◽  
Image Analysis ◽  
Free Surface ◽  
Damping Ratio ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Mass Ratio ◽  
Amplitude Response ◽  
Charge Coupled Device ◽  
A Charge

This work analyzes the influence of boundary conditions on the movements of a sphere immersed in a steady free surface flow. The sphere is free to move both in the transverse and streamwise directions and it is characterized by the values of the mass ratio m∗ equal to 1.34 and of the damping ratio ζ equal to 0.004. In all the experiments the blockage coefficient is kept constant, while the sphere is located at different distances from the free surface and from the bottom wall of the channel. The movements of the sphere have been measured by means of the image analysis of a charge coupled device camera which provides the 2D (streamwise and transverse) displacements of the sphere with a temporal resolution of 0.02 s. The experimental data show a significant influence of the boundaries on the sphere movement and highlight a different behavior of the amplitude response between the three different experimental setups considered.

scholarly journals Noninvasive calculation of the aortic blood pressure waveform from the flow velocity waveform: a proof of concept

2015 ◽  
Vol 309 (5) ◽  
pp. H969-H976 ◽  
Author(s):  
Samuel Vennin ◽  
Alexia Mayer ◽  
Ye Li ◽  
Henry Fok ◽  
Brian Clapp ◽  
...  
Keyword(s):  
Experimental Data ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Flow Velocity ◽  
Aortic Pressure ◽  
Pressure Waveform ◽  
Arterial Tree ◽  
Measured Flow ◽  
Rms Error ◽  
Measured Pressure

Estimation of aortic and left ventricular (LV) pressure usually requires measurements that are difficult to acquire during the imaging required to obtain concurrent LV dimensions essential for determination of LV mechanical properties. We describe a novel method for deriving aortic pressure from the aortic flow velocity. The target pressure waveform is divided into an early systolic upstroke, determined by the water hammer equation, and a diastolic decay equal to that in the peripheral arterial tree, interposed by a late systolic portion described by a second-order polynomial constrained by conditions of continuity and conservation of mean arterial pressure. Pulse wave velocity (PWV, which can be obtained through imaging), mean arterial pressure, diastolic pressure, and diastolic decay are required inputs for the algorithm. The algorithm was tested using 1) pressure data derived theoretically from prespecified flow waveforms and properties of the arterial tree using a single-tube 1-D model of the arterial tree, and 2) experimental data acquired from a pressure/Doppler flow velocity transducer placed in the ascending aorta in 18 patients (mean ± SD: age 63 ± 11 yr, aortic BP 136 ± 23/73 ± 13 mmHg) at the time of cardiac catheterization. For experimental data, PWV was calculated from measured pressures/flows, and mean and diastolic pressures and diastolic decay were taken from measured pressure (i.e., were assumed to be known). Pressure reconstructed from measured flow agreed well with theoretical pressure: mean ± SD root mean square (RMS) error 0.7 ± 0.1 mmHg. Similarly, for experimental data, pressure reconstructed from measured flow agreed well with measured pressure (mean RMS error 2.4 ± 1.0 mmHg). First systolic shoulder and systolic peak pressures were also accurately rendered (mean ± SD difference 1.4 ± 2.0 mmHg for peak systolic pressure). This is the first noninvasive derivation of aortic pressure based on fluid dynamics (flow and wave speed) in the aorta itself.

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