Numerical Analysis of the Flotation Ring of a Gravity-Type Fish Cage

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Guo-hai Dong ◽  
Shuang-hu Hao ◽  
Yun-peng Zhao ◽  
Zhi Zong ◽  
Fu-kun Gui
Keyword(s):  
Water Waves ◽  
Plane Deformation ◽  
Beam Theory ◽  
Superposition Method ◽  
Motion Equations ◽  
Modal Superposition Method ◽  
Waves Propagation ◽  
Elastic Responses ◽  
Increasing Demand ◽  
The Waves

The gravity-type fish cage is extensively applied with the increasing demand for fishery products. The flotation ring is its main load-bearing component and supports the whole cage. So it is essential to study the hydroelasticity of the flotation ring for the safety of a fish cage. An analytical method is proposed to study the elastic deformation of a simplified flotation ring subjected to water waves. The equations governing in-plane deformations are obtained according to curved beam theory, in which the modal superposition method is used to represent the in-plane deformation of an element of the ring. Then, the motion equations of the ring are built up coupled with deformation equations. The correlation between the predicted results and the experimental data is acceptable to validate the numerical modeling. Then the effect of Young’s module, radius of the ring, and wave conditions on elastic responses is discussed in terms of the prototype scale of a flotation ring. It is concluded that the deformations over the ring in the direction of waves’ propagation are the largest, and that the mooring point in the head-on direction of the waves is critical for reliability of the ring. Large deformations of the flotation ring may induce the failure of the fish cage when the storm covers it. So more attention to the hydroelasticity of the flotation ring should be paid in the design for a fish cage.

A Theoretical Analysis of Dynamic Elastic Response of a Circular Ring to Water Waves

2007 ◽  
Vol 129 (3) ◽  
pp. 211-218 ◽  
Author(s):  
G. H. Dong ◽  
S. H. Hao ◽  
Z. Zong ◽  
Y. N. Zheng
Keyword(s):  
Elastic Deformation ◽  
Water Waves ◽  
Equations Of Motion ◽  
Beam Theory ◽  
Fish Farming ◽  
Circular Ring ◽  
Open Ocean ◽  
Elastic Response ◽  
Superposition Method ◽  
Dominant Form

Fish farming in the open ocean is becoming a dominant form of fishery aquaculture due to the dramatic drop of fishery resources in near shore. Deep water anti-stormy fish cages are the most important tool for fish farming in the open ocean. The floatation ring, as a pivotal component of the fish cage, undergoes large deformations and it has been found that the floatation ring oscillates when moving in water waves. In the most serious cases, its deformation is so large it can be damaged. The floatation ring is simplified as a free circular ring, and the governing equations of motion and deformation of the ring can be built up according to the force equilibrium and curved beam theory. The numerical calculation is carried out in terms of the modal superposition method. The motion and the deformation of the ring are analyzed, and two corresponding equations in which the elastic deformations are neglected and considered are given, respectively. By comparing the results of the above two equations, we get the resonant frequencies and the frequency scope influenced by the elastic deformation. It is concluded that the influence of the deformation of the ring is very important for the oscillation of the ring, particularly the former three modes of the elastic deformation which cannot be neglected.

Structural Shape Reconstruction of FBG Flexible Plate Using Modal Superposition Method

2017 ◽  
Author(s):  
Li Li ◽  
Ben S. Zhong ◽  
Zi Y. Geng ◽  
Wei Sun
Keyword(s):  
Mode Shape ◽  
Shape Reconstruction ◽  
Displacement Sensor ◽  
Superposition Method ◽  
Flexible Plate ◽  
Structural Shape ◽  
Modal Superposition ◽  
Displacement Mode ◽  
Modal Superposition Method ◽  
Strain Data

Structural shape reconstruction is a critical issue for real-time structural health monitoring in the fields of engineering application. This paper shows how to implement structural shape reconstruction using a small number of strain data measured by fiber Bragg grating (FBG) sensors. First, the basic theory of structural shape reconstruction is introduced using modal superposition method. A transformation is derived from the measured discrete strain data to global displacement field through modal coordinate, which is the same for strain mode shape superposition and displacement mode shape superposition. Then, optimization of the sensor layout is investigated to achieve the effective reconstruction effect. Finally, structural shape reconstruction algorithm using modal superposition method is applied in experiments. The experiment results show that the reconstructed displacements match well with those measured by a laser displacement sensor and the proposed approach is a promising method for structural shape reconstruction.

Seismic Analysis of Structures With Coulomb Friction

1983 ◽  
Vol 105 (2) ◽  
pp. 171-178 ◽  
Author(s):  
V. N. Shah ◽  
C. B. Gilmore
Keyword(s):  
Rigid Body ◽  
Coulomb Friction ◽  
Seismic Event ◽  
Seismic Analysis ◽  
Equations Of Motion ◽  
Relative Displacement ◽  
Rigid Body Motion ◽  
Body Motion ◽  
Superposition Method ◽  
Modal Superposition Method

A modal superposition method for the dynamic analysis of a structure with Coulomb friction is presented. The finite element method is used to derive the equations of motion, and the nonlinearities due to friction are represented by pseudo-force vector. A structure standing freely on the ground may slide during a seismic event. The relative displacement response may be divided into two parts: elastic deformation and rigid body motion. The presence of rigid body motion necessitates the inclusion of the higher modes in the transient analysis. Three single degree-of-freedom problems are solved to verify this method. In a fourth problem, the dynamic response of a platform standing freely on the ground is analyzed during a seismic event.

scholarly journals Propagation of Surface Waves in Asphalt Pavements Generated by Different Load Impulse of Falling Weight Deflectometer

2019 ◽  
Vol 15 (1) ◽  
pp. 29-35
Author(s):  
Jozef Komačka ◽  
IIja Březina
Keyword(s):  
Surface Waves ◽  
Travel Time ◽  
Time History ◽  
Asphalt Pavements ◽  
Load Force ◽  
Falling Weight Deflectometer ◽  
Waves Propagation ◽  
Propagation Of Waves ◽  
Falling Weight ◽  
The Waves

Abstract The propagation of waves generated by load impulse of two FWD types was assessed using test outputs in the form of time history data. The calculated travel time of wave between the receiver in the centre of load and others receivers showed the contradiction with the theory as for the receivers up to 600 (900) mm from the centre of load. Therefore, data collected by the sensors positioned at the distance of 1200 and 1500 mm were used. The influence of load magnitude on the waves propagation was investigated via the different load force with approximately the same load time and vice versa. Expectations relating to the travel time of waves, depending on the differences of load impulse, were not met. The shorter travel time of waves was detected in the case of the lower frequencies. The use of load impulse magnitude as a possible explanation was not successful because opposite tendencies in travel time were noticed.

scholarly journals MACH-REFLECTION AS A DIFFRACTION PROBLEM

1976 ◽  
Vol 1 (15) ◽  
pp. 45 ◽  
Author(s):  
Udo Berger ◽  
Soren Kohlhase
Keyword(s):  
Wave Height ◽  
Incident Wave ◽  
Water Waves ◽  
Gas Dynamics ◽  
Mach Reflection ◽  
Diffraction Problem ◽  
Vertical Wall ◽  
Oblique Wave ◽  
Wave Heights ◽  
The Waves

As under oblique wave approach water waves are reflected by a vertical wall, a wave branching effect (stem) develops normal to the reflecting wall. The waves progressing along the wall will steep up. The wave heights increase up to more than twice the incident wave height. The £jtudy has pointed out that this effect, which is usually called MACH-REFLECTION, is not to be taken as an analogy to gas dynamics, but should be interpreted as a diffraction problem.

Solitons and other solutions of the long-short wave equation

2015 ◽  
Vol 25 (1) ◽  
pp. 129-145 ◽  
Author(s):  
Ghodrat Ebadi ◽  
Aida Mojaver ◽  
Sachin Kumar ◽  
Anjan Biswas
Keyword(s):  
Wave Equation ◽  
Water Waves ◽  
Soliton Solutions ◽  
Expansion Method ◽  
Short Wave ◽  
Shallow Water Waves ◽  
Content Type ◽  
Integration Techniques ◽  
Physical Phenomena ◽  
The Waves

Purpose – The purpose of this paper is to discuss the integrability studies to the long-short wave equation that is studied in the context of shallow water waves. There are several integration tools that are applied to obtain the soliton and other solutions to the equation. The integration techniques are traveling waves, exp-function method, G′/G-expansion method and several others. Design/methodology/approach – The design of the paper is structured with an introduction to the model. First the traveling wave hypothesis approach leads to the waves of permanent form. This eventually leads to the formulation of other approaches that conforms to the expected results. Findings – The findings are a spectrum of solutions that lead to the clearer understanding of the physical phenomena of long-short waves. There are several constraint conditions that fall out naturally from the solutions. These poses the restrictions for the existence of the soliton solutions. Originality/value – The results are new and are sharp with Lie symmetry analysis and other advanced integration techniques in place. These lead to the connection between these integration approaches.

Airside Velocity Measurement Above the Wind-Generated Water Waves

2007 ◽  
Author(s):  
Nasiruddin Shaikh ◽  
Kamran Siddiqui
Keyword(s):  
Water Waves ◽  
Flow Behavior ◽  
Momentum Exchange ◽  
Mean Velocity ◽  
Wind Speeds ◽  
Velocity Magnitude ◽  
Image Velocimetry ◽  
Sweeping Processes ◽  
High Level ◽  
The Waves

An experimental study conducted to investigate the airside flow behavior within the crest-trough region over wind generated water waves is reported. Two-dimensional velocity field in a plane perpendicular to the surface was measured using particle image velocimetry (PIV) at wind speeds ranging from 1.5 m s−1 to 4.4 m s−1. The results show a reduction in the mean velocity magnitude when gravity waves appear on the surface. A sequence of consecutive velocity fields has shown the bursting and sweeping processes and the flow separation above the waves. The results also indicate that the flow dynamics in the crest-trough region are significantly different than that at greater heights. High level of turbulence was observed in this region which could not be predicted from the measurements at greater heights. Thus, it is concluded that the quantitative investigation of the flow in the immediate vicinity of the interface is vital for an improved understanding of the heat, mass and momentum exchange between air and water.

Experiments on strong interactions between solitary waves

1978 ◽  
Vol 85 (3) ◽  
pp. 417-431 ◽  
Author(s):  
P. D. Weidman ◽  
T. Maxworthy
Keyword(s):  
Shallow Water ◽  
Solitary Waves ◽  
Water Waves ◽  
Vries Equation ◽  
Rectangular Channel ◽  
Quantitative Agreement ◽  
Strong Interactions ◽  
Shallow Water Waves ◽  
Qualitative And Quantitative ◽  
The Waves

Experiments on the interaction between solitary shallow-water waves propagating in the same direction have been performed in a rectangular channel. Two methods were devised to compensate for the dissipation of the waves in order to compare results with Hirota's (1971) solution for the collision of solitons described by the Kortewegde Vries equation. Both qualitative and quantitative agreement with theory is obtained using the proposed corrections for wave damping.

Experimental Investigation on Vortex-Induced Vibration of Dual Pipes With Unequal Diameters in Tandem

2020 ◽  
Author(s):  
Mengmeng Zhang ◽  
Shixiao Fu ◽  
Zhiqi Zhang ◽  
Haojie Ren ◽  
Yuwang Xu
Keyword(s):  
Vibration Frequency ◽  
Reynolds Numbers ◽  
Superposition Method ◽  
Wall Surface ◽  
Flexible Pipes ◽  
Modal Superposition Method ◽  
Out Of Plane ◽  
Single Pipe ◽  
Dominant Vibration Frequency ◽  
Significant Interference

Abstract With the massive use of buddle risers and pipelines in deep-water oil production industries, the demand to focus on the research of interference effects of dual pipe has been greatly enhanced. This paper presents interference experiments of dual flexible pipes with unequal diameters under uniform flow with Reynolds numbers ranging from 1.8E3 to 1.1E4. The pipe with larger diameter was set to be the upstream pipe. Various tandem arrangements with wall surface-to-wall surface distances being 3D to 8D were tested, where D is the smaller pipe diameter. Fiber Bragg grating (FBG) strain sensors were used to measure both in-plane and out-of-plane strain responses. Modal superposition method was applied to reconstruct IL mean displacement. Significant interference effect was found under the condition that wall-to-wall gap is smaller than 8D, where CF and IL vibration frequency ratio of downstream pipe equals to 1.0 and IL mean displacement gets smaller compared to those of single pipe in isolation. Moreover, a special ‘capture’ phenomenon, that the dominant vibration frequency and mode of downstream pipe were as the same as that of the upstream pipe subjecting to the uniform flows, was found when wall-to-wall distances were 4D and 8D.

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