Nonlinear Analysis of an Oscillating Wave Surge Converter in Frequency Domain via Statistical Linearization

2020 ◽  
Author(s):  
Leandro S. P. da Silva ◽  
Nataliia Y. Sergiienko ◽  
Benjamin S. Cazzolato ◽  
Boyin Ding ◽  
Celso P. Pesce ◽  
...  
Keyword(s):  
Nonlinear Analysis ◽  
Frequency Domain ◽  
Wave Energy ◽  
Numerical Models ◽  
Computational Cost ◽  
Viscous Drag ◽  
Design Parameters ◽  
Statistical Linearization ◽  
Mean Power ◽  
Energy Devices

Abstract Wave energy devices operate in resonant conditions to optimize power absorption, which leads to large displacements. As a result, nonlinearities play an important role in the system dynamics and must be accounted for in the numerical models for realistic prediction of the power generated. In general, time domain (TD) simulations are employed to capture the effects of the nonlinearities. However, the computational cost associated with these simulations is considerably higher compared to linear frequency domain (FD) methods. In this regard, the following work deals with the nonlinear analysis of an oscillating wave surge converter (OWSC) in the FD via the statistical linearization (SL) technique. Four nonlinearities for the proposed device are addressed: Coulomb-like torque regulated by the direction of motion, viscous drag torque, nonlinear buoyant net torque, and parametric excitation torque modulated by the flap angle. The reliability of the SL technique is compared with nonlinear TD simulations in terms of response probability distribution and power spectrum density (PSD) of the response and torque; and mean power produced. The results have demonstrated a good agreement between TD simulations and SL, while the computation time of the SL model is approximately 3 orders of magnitude faster. As a result, SL is a valuable tool to assess the OWSC performance under various wave scenarios over a range of design parameters, and can assist the development of such wave energy converters (WECs).

Nonlinear Analysis of an Oscillating Water Column Wave Energy Device in Frequency Domain via Statistical Linearization

2019 ◽  
Author(s):  
Leandro S. P. da Silva ◽  
Celso P. Pesce ◽  
Helio M. Morishita ◽  
Rodolfo T. Gonçalves
Keyword(s):  
System Dynamics ◽  
Frequency Domain ◽  
Water Column ◽  
Wave Energy ◽  
Time Domain ◽  
Computational Cost ◽  
Operating Conditions ◽  
Statistical Linearization ◽  
Large Displacements ◽  
Oscillating Water Column

Abstract Wave energy converters (WECs) are often subject to large displacements during operating conditions. Hence, nonlinearities present in numerical methods to estimate the performance of WECs must be considered for realistic predictions. These large displacements occur when the device operates on resonant conditions, which results in maximum energy conversion. The system dynamics are usually simulated via time domain models in order to being able to capture nonlinearities. However, a high computational cost is associated with those simulations. Alternatively, the present work treats the nonlinearities in the frequency domain via Statistical Linearization (SL). The SL results are compared to the Power Spectrum Density (PSD) of time domain simulations to verify the reliability of the proposed method. In this regard, the work initiates with the derivation of the governing equations of the air-chamber and the Oscillating Water Column (OWC). Then, the SL technique is presented and applied. The SL results show a satisfactory agreement for the system dynamics, mean surface elevation, mean pressure, and mean power compared to time domain simulations. Also, the SL technique produces a rapid estimation of the response, which is an effective approach for the evaluation of numerous environmental conditions and design, and further optimization procedures.

Nonlinear Analysis of a Heaving Point Absorber in Frequency Domain via Statistical Linearization

2019 ◽  
Author(s):  
Leandro S. P. da Silva ◽  
Helio M. Morishita ◽  
Celso P. Pesce ◽  
Rodolfo T. Gonçalves
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Statistical Linearization ◽  
Mean Power ◽  
Energy Devices ◽  
Drag Forces ◽  
System A ◽  
Spectrum Density ◽  
The Time Domain ◽  
Heave Motion

Abstract The majority of wave energy devices operate close to resonant conditions to enhance energy conversion resulting in large displacements. As a result, nonlinearities significantly contribute to the dynamics of the system. A typical approach to predict the behavior of the system and power output relies on the derivation of a mathematical model in the time domain to simulate the dynamics through some numerical codes. However, a relatively high computational demand is required for those simulations. In this regard, the present work deals with the nonlinearities in the frequency domain via Statistical Linearization. Two different power-take-off systems are investigated, a linear and a hydraulic one, and their mean power calculations are derived based on the Statistical Linearization. The reliability of the method is verified against the Power Spectrum Density (PSD) of nonlinear time domain simulations. Only the heave motion is analyzed, and several nonlinearities commonly reported for Point Absorbers (PA) were considered, such as cubic stiffness, geometric nonlinearities, drag forces, and Coulomb forces. The approach employed in this work offers a reliable estimation of body dynamics for all nonlinearities considered. In addition, the present method produced a fast estimation, which can be valuable for the assessment of several designs and sea load conditions.

scholarly journals Wave Propagation in Thin-Walled Aortic Analogues

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
C. G. Giannopapa ◽  
J. M. B. Kroot ◽  
A. S. Tijsseling ◽  
M. C. M. Rutten ◽  
F. N. van de Vosse
Keyword(s):  
Experimental Data ◽  
Wave Propagation ◽  
Frequency Domain ◽  
Analytical Model ◽  
Viscoelastic Properties ◽  
Numerical Models ◽  
Computational Cost ◽  
One Dimensional ◽  
Arterial Blood

Research on wave propagation in liquid filled vessels is often motivated by the need to understand arterial blood flows. Theoretical and experimental investigation of the propagation of waves in flexible tubes has been studied by many researchers. The analytical one-dimensional frequency domain wave theory has a great advantage of providing accurate results without the additional computational cost related to the modern time domain simulation models. For assessing the validity of analytical and numerical models, well defined in vitro experiments are of great importance. The objective of this paper is to present a frequency domain analytical model based on the one-dimensional wave propagation theory and validate it against experimental data obtained for aortic analogs. The elastic and viscoelastic properties of the wall are included in the analytical model. The pressure, volumetric flow rate, and wall distention obtained from the analytical model are compared with experimental data in two straight tubes with aortic relevance. The analytical results and the experimental measurements were found to be in good agreement when the viscoelastic properties of the wall are taken into account.

Wave Energy Assessments in the Coastal Environment of Portugal Continental

2008 ◽  
Author(s):  
Eugen Rusu ◽  
C. Guedes Soares
Keyword(s):  
Wave Energy ◽  
Numerical Models ◽  
Specific Area ◽  
Wave Climate ◽  
Coastal Environment ◽  
Wave Power ◽  
Relevant Parameter ◽  
Density Spectrum ◽  
Energy Devices ◽  
Power Resources

The potential for wave energy extraction can be obtained from the analysis of the wave climate which can be determined with numerical models. The wave energy devices can be deployed in offshore, nearshore and shoreline. From this reason, it is important to be able to assess properly the spatial distribution of the wave energy in various locations from the offshore to the coastline in a specific area. The methodology proposed here considers a SWAN based wave model system focusing in the Portuguese continental coastal environment from deep water towards the nearshore. An analysis of the average and high energetic conditions was first performed for a ten-year period, between 1994 and 2003, considering the most relevant in situ measurements available in the Portuguese nearshore. In this way both the average and high energetic conditions corresponding to the Portuguese continental costal environment have been properly defined. For the most relevant average wave conditions, SWAN simulations were performed in some medium resolution areas covering the northern and central parts of Portugal continental, which are traditionally considered richer in wave power resources. The present work allows the identification of some locations in the continental coastal environment of Portugal with greater potential from the point of view of wave power resources. An important observation is related to the fact that the wave power depends on the product between the energy density spectrum and the group velocity of waves. This means that, although the significant wave height is a relevant parameter when assessing the wave power in a specific site, a location having in general higher wave heights is not necessarily also the richest in wave power.

scholarly journals Wave Propagation in Thin-Walled Aortic Analogues

2008 ◽  
Author(s):  
C. G. Giannopapa ◽  
J. M. B. Kroot
Keyword(s):  
Experimental Data ◽  
Wave Propagation ◽  
Frequency Domain ◽  
Analytical Model ◽  
Viscoelastic Properties ◽  
Numerical Models ◽  
Computational Cost ◽  
Arterial Blood Flow ◽  
One Dimensional ◽  
Arterial Blood

Research wave propagation in liquid filled vessels is often motivated by the need to understand arterial blood flow. Theoretical and experimental investigation of the propagation of waves in flexible tubes has been studied by many researchers. The analytical one dimensional frequency domain wave theory has a great advantage of providing accurate results without the additional computational cost related to the modern time domain simulation models. For assessing the validity of analytical and numerical models well defined in-vitro experiments are of great importance. The objective of this paper is to present a frequency domain transmission line analytical model based on one-dimensional wave propagation theory and validate it against experimental data obtained for aortic analogues. The elastic and viscoelastic properties of the wall are included in the analytical model. The pressure, flow and wall distention results obtained from the analytical model are compared with experimental data in two straight tubes with aortic relevance. The analytical models and the experimental measurements were found to be in good agreement when the viscoelastic properties of the wall are taken into account.

Efficient Dynamic Analysis of a Nonlinear Wave Energy Harvester Model

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Pol D. Spanos ◽  
Felice Arena ◽  
Alessandro Richichi ◽  
Giovanni Malara
Keyword(s):  
Monte Carlo ◽  
Linear System ◽  
Wave Energy ◽  
Alternative Energy ◽  
Energy Harvester ◽  
Single Point ◽  
Computational Cost ◽  
Complex Problem ◽  
Statistical Linearization ◽  
Monte Carlo Techniques

In recent years, wave energy harvesting systems have received considerable attention as an alternative energy source. Within this class of systems, single-point harvesters are popular at least for preliminary studies and proof-of-concept analyses in particular locations. Unfortunately, the large displacements of a single-point wave energy harvester are described by a set of nonlinear equations. Further, the excitation is often characterized statistically and in terms of a relevant power spectral density (PSD) function. In the context of this complex problem, the development of efficient techniques for the calculation of reliable harvester response statistics is quite desirable, since traditional Monte Carlo techniques involve nontrivial computational cost. The paper proposes a statistical linearization technique for conducting expeditiously random vibration analyses of single-point harvesters. The technique is developed by relying on the determination of a surrogate linear system identified by minimizing the mean square error between the linear system and the nonlinear one. It is shown that the technique can be implemented via an iterative procedure, which allows calculating statistics, PSDs, and probability density functions (PDFs) of the response components. The reliability of the statistical linearization solution is assessed vis-à-vis data from relevant Monte Carlo simulations. This novel approach can be a basis for constructing computationally expeditious assessments of various design alternatives.

scholarly journals Simple Controllers for Wave Energy Devices Compared

2020 ◽  
Vol 8 (10) ◽  
pp. 793
Author(s):  
Demián García-Violini ◽  
Nicolás Faedo ◽  
Fernando Jaramillo-Lopez ◽  
John V. Ringwood
Keyword(s):  
Wave Energy ◽  
Pid Controller ◽  
High Performance ◽  
Impedance Matching ◽  
Computational Cost ◽  
Numerical Algorithms ◽  
Control Engineering ◽  
Physical Constraints ◽  
Energy Devices

The design of controllers for wave energy devices has evolved from early monochromatic impedance-matching methods to complex numerical algorithms that can handle panchromatic seas, constraints, and nonlinearity. However, the potential high performance of such numerical controller comes at a computational cost, with some algorithms struggling to implement in real-time, and issues surround convergence of numerical optimisers. Within the broader area of control engineering, practitioners have always displayed a fondness for simple and intuitive controllers, as evidenced by the continued popularity of the ubiquitous PID controller. Recently, a number of energy-maximising wave energy controllers have been developed based on relatively simple strategies, stemming from the fundamentals behind impedance-matching. This paper documents this set of (5) controllers, which have been developed over the period 2010–2020, and compares and contrasts their characteristics, in terms of energy-maximising performance, the handling of physical constraints, and computational complexity. The comparison is carried out both analytically and numerically, including a detailed case study, when considering a state-of-the-art CorPower-like device.

scholarly journals The performance of the Mocean M100 wave energy converter described through numerical and physical modelling

2020 ◽  
Vol 3 (1) ◽  
pp. 11-19
Author(s):  
J. Cameron McNatt ◽  
Christopher H. Retzler
Keyword(s):  
Frequency Domain ◽  
Wave Energy ◽  
Time Domain ◽  
Numerical Models ◽  
Average Power ◽  
Physical Modelling ◽  
Wave Energy Converter ◽  
Domain Model ◽  
Energy Converter ◽  
Cost Of Energy

Mocean Energy has designed a 100-kW hinged-raft wave energy converter (WEC), the M100, which has a novel geometry that reduces the cost of energy by improving the ratios of power per size and power per torque. The performance of the M100 is shown through the outputs of frequency-domain and time-domain numerical models, which are compared with those from 1/20th scale wave-tank testing. Results show that for the undamped, frequency-domain model, there are resonant peaks in the response at 6.6 and 9.6 s, corresponding to wavelengths that are 1.9 and 3.7 times longer than the machine. With the inclusion of power-take-off and viscous damping, the power response as a function of frequency shows a broad bandwidth and a hinge flex amplitude of 12-20 degrees per meter of wave amplitude. Comparison between the time-domain model and physical data in a variety of sea states, up to a significant wave height of 4.5 m, show agreements within 10% for average power absorption, which is notable because only simple, nonlinear, numerical models were used. The M100 geometry results in a broad-banded, large amplitude response due to its asymmetric shape, which induces coupling between modes of motion.

Nonlinear Analysis of Rail Vehicle Forced Lateral Response and Stability

1979 ◽  
Vol 101 (3) ◽  
pp. 230-237 ◽  
Author(s):  
J. Karl Hedrick ◽  
A. V. Arslan
Keyword(s):  
Nonlinear Analysis ◽  
Frequency Domain ◽  
Numerical Algorithm ◽  
Design Tool ◽  
Statistical Linearization ◽  
Rail Vehicle ◽  
Rail Vehicles ◽  
Lateral Response ◽  
Wheel Profile ◽  
Track Irregularities

The method of statistical linearization is presented as a design tool for rail vehicles that is capable of including fundamental nonlinearities such as wheel profile geometry and suspension nonlinearities. The method is capable of predicting the response of the vehicle to statistical track irregularities as well as the onset of hunting. The fundamentals of the method, an efficient frequency domain numerical algorithm for stationary response, and a design example are presented. The design example illustrates the influence of wheel profile, gage, track roughness, and suspension variations on vehicle response and stability.

Nonlinear Analysis of an Oscillating Wave Surge Converter in Frequency Domain via Statistical Linearization

2021 ◽  
Author(s):  
Leandro Souza Pinheiro da Silva ◽  
Nataliia Sergiienko ◽  
Boyin Ding ◽  
Benjamin Cazzolato ◽  
Celso Pesce ◽  
...  
Keyword(s):  
Nonlinear Analysis ◽  
Frequency Domain ◽  
Statistical Linearization
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