Experimental Validation of Hydroelastic Analysis of Pontoon-, Semisubmersible- and Hybrid-Type VLFS

2008 ◽  
Author(s):  
Tomoaki Utsunomiya ◽  
Eiichi Watanabe ◽  
Tetsuya Hiraishi ◽  
Takatoshi Noguchi ◽  
Syuji Yamamoto
Keyword(s):  
Drag Force ◽  
Experimental Validation ◽  
Numerical Results ◽  
Irregular Waves ◽  
Viscous Damping ◽  
Bottom Slope ◽  
Hybrid Type ◽  
Numerical Predictions ◽  
Wave Basin ◽  
Hydroelastic Analysis

This paper presents a hydroelastic analysis of pontoon-, semisubmersible-, and hybrid-type VLFS and its experimental validation. In the analysis, the detailed configuration of the experimental model is considered by using three dimensional finite element (FE) method. Experimental models measuring 15m in length, 3m in width and 0.03–0.23m in draft (depending on whether it is the pontoon and semisubmersible part) are built. The experiment has been made in the wave-basin with the bottom-slope of 1/75. At the same time, a hydroelastic analysis is carried out using the same models as the experimental ones in a wave-basin with flat as well as slanting bottom with slope of 1/75. By comparing the numerical results and experiment, the effect of bottom slope is verified. In the analysis of the semisubmersible part, the effect of viscous damping is considered by using the drag force formula with assumed drag force coefficient of 2.0. A comparison between the experiment and the analytical results indicates that numerical results from the semisubmersible part with additional effects of viscous damping agree better with the experimental results than those without. An experiment using irregular waves is also carried out and compared with the numerical predictions. Finally, the steady drift forces are analyzed using the far-field method and compared with the experiment.

Hydroelastic Analysis and Experimental Validation of a 350,000 DWT Very Large Crude Carrier

2017 ◽  
Author(s):  
Yuan Lin ◽  
Ning Ma ◽  
Deyu Wang ◽  
Xiechong Gu
Keyword(s):  
Numerical Simulation ◽  
Experimental Validation ◽  
Irregular Waves ◽  
Strength Analysis ◽  
Response Analysis ◽  
Bending Moments ◽  
Time Histories ◽  
Hydroelastic Analysis ◽  
Hydroelastic Response ◽  
Full Loading

Hydroelastic response of Very Large Crude Carrier (VLCC), such as springing and whipping, is very important for the fatigue strength analysis. In the present paper, numerical simulation and model test are conducted simultaneously on the springing responses of a 350,000DWT VLCC. The numerical simulation results are obtained by combining 2-D strip method and 3-D Finite Element Method (FEM) in the frequency domain. Meanwhile, the segmented model tests are conducted in three conditions. Additionally, the experimental time histories of wave bending moments in regular and irregular waves are presented. In conclusion, the methods and results presented in this paper have shown that the springing would be much easier when the VLCC is in ballast condition or the full loading conditions with reduced stiffness. The springing response will happen, when the wave encounter frequency is near to the half and one third of the ship’s flexural natural frequency. The numerical method presented is available for springing response analysis quickly with acceptable accuracy.

Experimental Assessment of the Performance of CECO Wave Energy Converter in Irregular Waves

2018 ◽  
Author(s):  
Claudio A. Rodríguez ◽  
F. Taveira-Pinto ◽  
P. Rosa-Santos
Keyword(s):  
Wave Energy ◽  
Transfer Functions ◽  
Nonlinear Effects ◽  
Model Tests ◽  
Experimental Results ◽  
Irregular Waves ◽  
Scale Model ◽  
Experimental Assessment ◽  
Simplified Approach ◽  
Wave Basin

A new concept of wave energy device (CECO) has been proposed and developed at the Hydraulics, Water Resources and Environment Division of the Faculty of Engineering of the University of Porto (FEUP). In a first stage, the proof of concept was performed through physical model tests at the wave basin (Rosa-Santos et al., 2015). These experimental results demonstrated the feasibility of the concept to harness wave energy and provided a preliminary assessment of its performance. Later, an extensive experimental campaign was conducted with an enhanced 1:20 scale model of CECO under regular and irregular long and short-crested waves (Marinheiro et al., 2015). An electric PTO system with adjustable damping levels was also installed on CECO as a mechanism of quantification of the WEC power. The results of regular waves tests have been used to validate a numerical model to gain insight into different potential configurations of CECO and its performance (López et al., 2017a,b). This paper presents the results and analyses of the model tests in irregular waves. A simplified approach based on spectral analyses of the WEC motions is presented as a means of experimental assessment of the damping level of the PTO mechanism and its effect on the WEC power absorption. Transfer functions are also computed to identify nonlinear effects associated to higher waves and to characterize the range of periods where wave absorption is maximized. Furthermore, based on the comparison of the present experimental results with those corresponding to a linear numerical potential model, some discussions are addressed regarding viscous and other nonlinear effects on CECO performance.

Experimental Validation of a Wave Elevation Observer on a Floating Wind Turbine Model

2021 ◽  
Author(s):  
Simone Di Carlo ◽  
Alessandro Fontanella ◽  
Alan Facchinetti ◽  
Sara Muggiasca ◽  
Federico Taruffi ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Experimental Validation ◽  
Control Strategies ◽  
Estimation Procedure ◽  
Floating Platform ◽  
Experimental Campaign ◽  
Wave Elevation ◽  
Floating Wind Turbine ◽  
Wave Basin ◽  
Turbine Model

Abstract The scope of this work is to investigate if and how it is possible to estimate the incident wave elevation on a floating wind turbine, with the purpose of improved control strategies. A Kalman based algorithm is proposed, which receives as input the rigid motions of the floater and estimates the wave elevation hitting the floating platform. The structure of the observer is described and the estimator is tested numerically on the OC3-Hywind platform coupled with the 5-MW reference wind turbine from NREL. Limitations to the estimation procedure are discussed. Finally the algorithm is tested on experimental data coming from a wave basin experimental campaign on a floating wind turbine model. The algorithm still needs improvements, but results are encouraging in the development of this technology.

On the limitations of two- and three-dimensional linear hydroelasticity analyses applied to a fast patrol boat

2009 ◽  
Vol 223 (3) ◽  
pp. 457-478 ◽  
Author(s):  
F M Santos ◽  
P Temarel ◽  
C Guedes Soares
Keyword(s):  
Dynamic Behaviour ◽  
Transfer Functions ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Body Motion ◽  
Numerical Predictions ◽  
Dimensional Finite Element ◽  
Hydroelastic Analysis ◽  
Three Dimensional Finite Element ◽  
Wave Induced

The aim of this paper is to study the symmetric (i.e. heave and pitch motions and distortions associated with vertical bending) wave-induced dynamic behaviour of a fast patrol boat using a unified hydroelasticity analysis. This includes two- and three-dimensional structural idealizations using beam and three-dimensional finite element modelling. The fluid—flexible structure interaction is carried out using three-dimensional potential flow analysis, for both structural idealizations, based on a pulsating source singularity distribution on the mean wetted surface. The calculations are carried out in regular waves for two forward speeds (Froude numbers Fn = 0.5 and 0.63) and three heading angles, i.e. 180 (head), 135, and 90 degrees. Results from full-scale trials are also presented in order to compare rigid body motion transfer functions with numerical predictions. There are large differences between numerically predicted and measured motions, as is to be expected for this fast hull form. The paper reports that the evaluation of the dynamic behaviour of the fast patrol boat, with small length to beam ratio, by means of the unified hydroelastic analysis, shows some inherent limitations of the beamlike approach for this particular type of vessel.

Experimental Validation of a Dynamic Model for Flexible Link Mechanisms

2001 ◽  
Author(s):  
R. Caracciolo ◽  
A. Gasparetto ◽  
A. Trevisani
Keyword(s):  
Mathematical Model ◽  
Experimental Validation ◽  
Numerical Results ◽  
Test Case ◽  
Planar Mechanisms ◽  
Transient Period ◽  
Element Approach ◽  
Multi Body ◽  
The Mathematical Model ◽  
Good Agreement

Abstract This paper presents an experimental validation of a finite element approach for the dynamic analysis of flexible multi-body planar mechanisms. The mathematical model employed accounts for mechanism geometric and inertial non-linearities and considers coupling effects among rigid-body and elastic motion. A flexible five-bar linkage actuated by two electric motors is employed as a test case. Experimentally determined link absolute deformations are compared with the numerical results obtained simulating the system dynamic behavior through the mathematical model. The experimental and numerical results are in good agreement especially after the very first transient period.

Freak Wave Generation in a Wave Basin With HOSM-WG Method

2015 ◽  
Author(s):  
Hidetaka Houtani ◽  
Takuji Waseda ◽  
Wataru Fujimoto ◽  
Keiji Kiyomatsu ◽  
Katsuji Tanizawa
Keyword(s):  
Control Method ◽  
Irregular Waves ◽  
Frequency Bandwidth ◽  
Freak Waves ◽  
Freak Wave ◽  
Wave Basin ◽  
Wave Trains ◽  
Directional Wave ◽  
Wave Maker ◽  
The Difference

A method to produce freak waves with arbitrary spectrum in a fully directional wave basin is presented here. This is an extension of Waseda, Houtani and Tanizawa at OMAE 2013[1], which used “HOSM-WG” based on the higher-order spectral method (HOSM). We used the following three methods to improve the HOSM-WG in [1]: “separation of free waves from bound waves,” “using Biesel’s transfer function in wavenumber space” and “using Schaffer’s 2nd-order wave maker control method.” Modulational wave trains, freak waves in unidirectional irregular waves and freak waves in short-crested irregular waves were generated in a wave basin. The experimental results using the improved HOSM-WG were compared to the HOSM simulation, and good agreements were found. The effectiveness of the improved HOSM-WG was ascertained. We showed that the difference between HOSM-WG and HOSM simulations became larger as wave steepness, frequency bandwidth of the spectrum or directional spreading became larger.

CFD-Based Numerical Wave Basin for FPSO in Irregular Waves

2019 ◽  
Author(s):  
Aldric Baquet ◽  
Hyunchul Jang ◽  
Ho-Joon Lim ◽  
Johyun Kyoung ◽  
Nicolas Tcherniguin ◽  
...  
Keyword(s):  
Physical Model ◽  
Model Testing ◽  
The Other ◽  
Irregular Waves ◽  
Motion Responses ◽  
Wave Basin ◽  
Modeling Practices ◽  
Numerical Wave

Abstract Following the successful application of CFD-based Numerical Wave Basin (NWB) to GBS, TLP and Semisubmersible platforms [1–4], the same methodology has been applied to simulate FPSO hull motion responses to irregular waves. It has been found that the NWB modeling practices developed for the other floater types must be modified for application to an FPSO. This paper describes how the NWB modeling practices have been improved, and then compares results from NWB simulations with those from physical model testing.

Current Effects on a Moored Floating Platform in a Sea State

2008 ◽  
Author(s):  
Carl Trygve Stansberg
Keyword(s):  
Irregular Waves ◽  
Mooring Line ◽  
Viscous Effects ◽  
Floating Platform ◽  
Sea State ◽  
Scaled Model ◽  
Wave Drift ◽  
Wave Basin ◽  
Wave Drift Damping ◽  
Non Gaussian

The significance of current-induced forces and effects on a moored semisubmersible production platform in various sea state conditions is explored, with emphasis on surge motions. Experimental data from 1:55 scaled model tests in a 50m × 80m wave basin are investigated. A description of the current generation is given first. The current in the actual basin is modelled by use of a return current under a false bottom. The importance of modelling a “real” physical current for the proper reproduction of platform responses is pointed out. The semisubmersible tests are carried out with the platform in current only, in irregular waves only, and in combined waves and current conditions. The effects from the current on platform motions and mooring line tensions are investigated. Vortex-Induced motions (VIM) are observed in pure current, depending on the actual combination of current velocity and natural sway period. In combined waves and current the VIM seems to be more or less disappearing. A large effect is seen on the wave drift responses. Both drift forces, non-Gaussian properties and resulting extreme motions and line tensions are significantly increased, especially in high sea states. This is explained through a combination of wave drift damping and viscous effects. At the same time the damping is also increased, but this only partly compensates for the increased forces.

Hydroelastic response of floating elastic discs to regular waves. Part 1. Wave basin experiments

2013 ◽  
Vol 723 ◽  
pp. 604-628 ◽  
Author(s):  
F. Montiel ◽  
F. Bonnefoy ◽  
P. Ferrant ◽  
L. G. Bennetts ◽  
V. A. Squire ◽  
...  
Keyword(s):  
Processing Technique ◽  
Optical Remote Sensing ◽  
Flexural Response ◽  
Numerical Predictions ◽  
Time Harmonic ◽  
Wave Basin ◽  
Order Components ◽  
Hydroelastic Response ◽  
Innovative Techniques ◽  
Data Processing Technique

AbstractA series of wave basin experiments is reported that investigates the flexural response of one or two floating thin elastic discs to monochromatic waves. The work is motivated by numerical model validation. Innovative techniques are used to ensure the experimental configuration is consistent with the model. This demands linear motions, time-harmonic conditions, homogeneity of the plate and the restriction of horizontal motions of the disc or discs. An optical remote sensing device is employed to record the deflection of the discs accurately. Tests involving a single disc and two discs are conducted for a range of disc thicknesses, incident wave steepnesses, frequencies and, in the case of two discs, geometrical arrangements. A data processing technique is used to decompose the raw data into its spectral harmonics and filter the higher-order components. Pointwise comparisons of the linear first-order component of the experimental deflection with numerical predictions are presented. Satisfying agreement is found, although the model consistently over predicts the deflection. Disc–disc interactions are observed in the two-disc tests. A brief discussion of the shortcomings of the pointwise analysis, with associated possible sources of discrepancy, provides a link to the study reported in Part 2 (Montiel et al. J. Fluid Mech., vol. 723, 2013, pp. 629–652).

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