Coupling Effects of Sloshing and Barge Motion in Variable Bathymetry

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Yan Su
Keyword(s):  
Computational Model ◽  
Frequency Domain ◽  
Potential Theory ◽  
Experimental Results ◽  
Floating Body ◽  
Coupling Effects ◽  
External Fluid

Abstract Two partially filled tanks fixed on rectangular barge floating in variable bathymetry is studied based on the linearized potential theory in the frequency domain. The internal sloshing motion is simulated by linearized superposition of natural sloshing modes. The motion of barge is solved by matching eigenfunctions expansion in the external fluid domain. The computational model is verified by experimental results. Coupling sway and roll motions of floating body with different filling levels are compared. The effects of both inclined bottom with different slopes and hump-shaped bottom with different heights are analyzed. Viewing from the results, coupling sway and roll motions of floating body are significantly affected by the shapes of bottoms.

scholarly journals Seakeeping Tests of a FOWT in Wind and Waves: An Analysis of Dynamic Coupling Effects and Their Impact on the Predictions of Pitch Motion Response

2021 ◽  
Vol 9 (2) ◽  
pp. 179
Author(s):  
Giovanni Amaral ◽  
Pedro Mello ◽  
Lucas do Carmo ◽  
Izabela Alberto ◽  
Edgard Malta ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Dynamic Coupling ◽  
Coupling Effects ◽  
Mooring Lines ◽  
Scaled Model ◽  
Wave Basin ◽  
Domain Models ◽  
Catenary System

The present work highlights some of the dynamic couplings observed in a series of tests performed in a wave basin with a scaled-model of a Floating Offshore Wind Turbine (FOWT) with semi-submersible substructure. The model was moored by means of a conventional chain catenary system and an actively controlled fan was used for emulating the thrust loads during the tests. A set of wave tests was performed for concomitant effects of not aligned wave and wind. The experimental measurements illustrate the main coupling effects involved and how they affect the FOWT motions in waves, especially when the floater presents a non-negligible tilt angle. In addition, a frequency domain numerical analysis was performed in order to evaluate its ability to capture these effects properly. The influence of different modes of fan response, floater trim angles (changeable with ballast compensation) and variations in the mooring stiffness with the offsets were investigated in the analysis. Results attest that significant changes in the FOWT responses may indeed arise from coupling effects, thus indicating that caution must be taken when simplifying the hydrodynamic frequency-domain models often used as a basis for the simulation of FOWTs in waves and in optimization procedures for the design of the floater and mooring lines.

scholarly journals Integrated experimental-computational analysis of a liver-islet microphysiological system for human-centric diabetes research

2021 ◽  
Author(s):  
Belén Casas ◽  
Liisa Vilén ◽  
Sophie Bauer ◽  
Kajsa Kanebratt ◽  
Charlotte Wennberg Huldt ◽  
...  
Keyword(s):  
Glucose Metabolism ◽  
Computational Model ◽  
In Silico ◽  
Experimental Results ◽  
Published Data ◽  
Diabetes Research ◽  
Glucose Response ◽  
High Blood Glucose

Microphysiological systems (MPS) are powerful tools for emulating human physiology and replicating disease progression in vitro. MPS could be better predictors of human outcome than current animal models, but mechanistic interpretation and in vivo extrapolation of the experimental results remain significant challenges. Here, we address these challenges using an integrated experimental-computational approach. This approach allows for in silico representation and predictions of glucose metabolism in a previously reported MPS with two organ compartments (liver and pancreas) connected in a closed loop with circulating medium. We developed a computational model describing glucose metabolism over 15 days of culture in the MPS. The model was calibrated on an experiment-specific basis using data from seven experiments, where single-liver or liver-islet cultures were exposed to both normal and hyperglycemic conditions resembling high blood glucose levels in diabetes. The calibrated models reproduced the fast (i.e. hourly) variations in glucose and insulin observed in the MPS experiments, as well as the long-term (i.e. over weeks) decline in both glucose tolerance and insulin secretion. We also investigated the behavior of the system under hypoglycemia by simulating this condition in silico, and the model could correctly predict the glucose and insulin responses measured in new MPS experiments. Last, we used the computational model to translate the experimental results to humans, showing good agreement with published data of the glucose response to a meal in healthy subjects. The integrated experimental-computational framework opens new avenues for future investigations toward disease mechanisms and the development of new therapies for metabolic disorders.

Numerical Analysis of a Floating Body With Two-Dimensional Moonpool Including Piston Mode

2010 ◽  
Author(s):  
Jaekyung Heo ◽  
Jong-Chun Park ◽  
Moo-Hyun Kim ◽  
Weon-Cheol Koo
Keyword(s):  
Free Surface ◽  
Viscous Flow ◽  
Experimental Results ◽  
Floating Body ◽  
Navier Stokes ◽  
Linear Potential ◽  
Navier Stokes Equation ◽  
Nonlinear Potential ◽  
Heave Motion ◽  
Piston Mode

In this paper, the potential and viscous flows are simulated numerically around a 2-D floating body with a moonpool (or a small gap) with particular emphasis on the piston mode. The floating body with moonpool is forced to heave in time domain. Linear potential code is known to give overestimated free-surface heights inside the moonpool. Therefore, a free-surface lid in the gap or similar treatments are widely employed to suppress the exaggerated phenomenon by potential theory. On the other hand, Navier-Stokes equation solvers based on a FVM can be used to take account of viscosity. Wave height and phase shift inside and outside the moon-pool are computed and compared with experimental results by Faltinsen et al. (2007) over various heaving frequencies. Pressure and vorticity fields are investigated to better understand the mechanism of the sway force induced by the heave motion. Furthermore, a nonlinear potential code is utilized to compare with the viscous flow. The viscosity effects are investigated in more detail by solving Euler equations. It is found that the viscous flow simulations agree very well with the experimental results without any numerical treatment.

Coupling Effects on Synchronizability of Two-Layer Network's Projective Outer Synchronization

2017 ◽  
Vol 873 ◽  
pp. 353-357
Author(s):  
Bo Yu Feng ◽  
Zhi Hao Zhang
Keyword(s):  
Nonlinear Dynamics ◽  
Mathematical Model ◽  
Complex Network ◽  
Simulation Experiment ◽  
Small World ◽  
Experimental Results ◽  
Coupling Effects ◽  
Network Synchronization ◽  
Numerical Examples ◽  
Outer Synchronization

Based on nonlinear dynamics theory and knowledge of complex network, this paper expanded the range of two-layer network synchronization to projective outers synchronization. A mathematical model was constructed and feasibility of synchronization was demonstrated. Then we improved the model in order to study the function of different couplings [1]. Numerical examples are examined to compare the synchronizability of projective outer synchronization with different couplings. A rule called "outer small-world effect" was found due to simulation experiment. Finally, some instances were used to explain experimental results.

Discriminant DCT Feature Extraction

2006 ◽  
pp. 205-221
Author(s):  
David Zhang ◽  
Xiao-Yuan Jing ◽  
Jian Yang
Keyword(s):  
Feature Extraction ◽  
Frequency Domain ◽  
Discrete Cosine Transform ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Experimental Results ◽  
Cosine Transform ◽  
Analysis Technique

This chapter provides a feature extraction approach that combines the discrete cosine transform (DCT) with LDA. The DCT-based frequency-domain analysis technique is introduced first. Then, we describe the presented discriminant DCT approach and analyze its theoretical properties. Finally, we offer detailed experimental results and a chapter summary.

scholarly journals Numerical and Experimental Investigations of Coupling Effects in Anisotropic Elastic Rotors

1999 ◽  
Vol 5 (4) ◽  
pp. 263-271 ◽  
Author(s):  
Horst Irretier ◽  
Georges Jacquet-Richardet ◽  
Frank Reuter
Keyword(s):  
Coupling Effect ◽  
Experimental Results ◽  
Mode Shapes ◽  
Experimental Investigations ◽  
Coupling Effects ◽  
Symmetry Approach ◽  
Anisotropic Elastic ◽  
Elastic Modes ◽  
Bending Modes ◽  
The One

It is known that in elastic disc-shaft systems in particular, the one-nodal-diameter mode of the discs can be highly coupled with the bending modes of the shaft. Consequently, when the system rotates, the elastic modes of the flexible discs are coupled with the gyroscopic modes of the flexible shaft equipped with rigid discs. In the paper this coupling effect is investigated numerically and experimentally.A numerical model, based on a finite element cyclic symmetry approach, is presented. This model has been developed for studying the wheel-shaft coupling effects on the global behavior of turbomachinery rotors. In order to better illustrate the phenomenon involved and to validate the model, the method is applied here to a thin tuned and detuned circular disc mounted on an elastic shaft. Related frequency and mode shapes of the rotating assembly are discussed. Additional experimental results, based on an experimental modal analysis technique for rotating structures, are presented. Both numerical and experimental results are compared.

Fast Frequency-Domain Algorithm for Estimating the Dynamic Wind-Induced Response of Large-Span Roofs Based on Cauchy’s Residue Theorem

2018 ◽  
Vol 18 (03) ◽  
pp. 1850037 ◽  
Author(s):  
Ning Su ◽  
Zhenggang Cao ◽  
Yue Wu
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Rational Functions ◽  
Induced Response ◽  
Response Analysis ◽  
Residue Theorem ◽  
Coupling Effects ◽  
Large Span ◽  
Modal Coupling ◽  
Cauchy’S Residue Theorem

Wind-induced response analysis is an important process in the design of large-span roofs. Conventional time-domain methods are computationally more expensive than frequency-domain algorithms; however, the latter are not as accurate because of the ill-treatment of the modal coupling effects. This paper revisited the derivations of the frequency-domain algorithm and proposed a fast algorithm for estimating the dynamic wind-induced response considering duly the modal coupling effects. With the wind load cross-spectra modeled by rational functions, closed-form solutions to the frequency-domain integrals can be calculated by Cauchy’s residue theorem, rather than by numerical integration, thereby reducing the truncation errors and enhancing the efficiency of computation. The algorithm is applied to the analysis of a grandstand roof and a spherical dome. Through comparison with time domain analyses results, the algorithm is proved to be reliable. A criterion of the coupling modal combination was suggested based on the cumulative modal contribution rate of over 70%.

Grounding Experiments of a Ship Model in Water Tank

2018 ◽  
Author(s):  
Ling Zhu ◽  
Qingwen Zhou ◽  
Mingsheng Chen ◽  
Xiaoqi Chen
Keyword(s):  
Damage Assessment ◽  
Experimental Results ◽  
Ship Motions ◽  
Water Tank ◽  
Coupling Effects ◽  
Surrounding Water ◽  
Ship Model

Grounding is one of the major threats to ships under operation. In this paper, the ship model grounding experiments are conducted in a water tank to study the coupling effects of both internal mechanics and external dynamics. The influence of surrounding water on ship motions during grounding is taken into account. During testing, varying rock penetrations are considered to study the grounding damage. Experimental results such as the horizontal grounding forces and damage extents are measured and analyzed. The results show that the grounding damage depends on the rock penetration. Besides, the surrounding water of the ship model has a big influence on grounding damage assessment.

The Effects of Inner-Liquid Motion on LNG Vessel Responses

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
S. J. Lee ◽  
M. H. Kim
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Surface Profile ◽  
Ship Motion ◽  
Liquid Sloshing ◽  
Diffraction Radiation ◽  
Time Domain Simulation ◽  
Coupling Effects ◽  
The Time Domain ◽  
Vessel Motion

The coupling and interactions between ship motion and inner-tank sloshing are investigated by a potential-viscous hybrid method in the time domain. For the time-domain simulation of vessel motion, the hydrodynamic coefficients and wave forces are obtained by a potential-theory-based 3D diffraction/radiation panel program in the frequency domain. Then, the corresponding simulations of motions in the time domain are carried out using the convolution-integral method. The liquid sloshing in a tank is simulated in the time domain by a Navier–Stokes solver. A finite difference method with SURF scheme assuming the single-valued free-surface profile is applied for the direct simulation of liquid sloshing. The computed sloshing forces and moments are then applied as external excitations to the ship motion. The calculated ship motion is in turn inputted as the excitation for liquid sloshing, which is repeated for the ensuing time steps. For comparison, we independently developed a 3D panel program for linear inner-fluid motions, and it is coupled with the vessel-motion program in the frequency domain. The developed computer programs are applied to a barge-type floating production storage and offloading (FPSO) hull equipped with two partially filled tanks. The time-domain simulation results show reasonably good agreement when compared with Maritime Research Institute Netherlands (MARIN’s) experimental results. The frequency-domain results qualitatively reproduce the trend of coupling effects, but the peaks are in general overpredicted. It is seen that the coupling effects on roll motions appreciably change with filling level. The most pronounced coupling effects on roll motions are the shift or split of peak frequencies. The pitch motions are much less influenced by the inner-fluid motion compared with roll motions.

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