Dynamics of Cage Floating Breakwater

2005 ◽  
Vol 127 (4) ◽  
pp. 331-339 ◽  
Author(s):  
K. Murali ◽  
S. S. Amer ◽  
J. S. Mani
Keyword(s):  
Rigid Body ◽  
Wave Length ◽  
Body Motion ◽  
Width Ratio ◽  
Random Wave ◽  
Relative Width ◽  
Large Wave ◽  
Floating Breakwater ◽  
Mooring Forces ◽  
Floating Breakwaters

Floating breakwaters have potential applications in protecting minor ports and harbors such as fisheries and recreational harbors, where-in stringent tranquillity requirements are not warranted. In field applications of the existing floating breakwaters, limitations are imposed due to their large relative width (ratio between breakwater width and wave length) requirements to achieve desirable tranquillity level. This relative width requirement is greater than 0.3 for the existing floating breakwaters. To overcome the above drawback associated with the existing system a new configuration for a floating breakwater is derived, which could yield the desired performance with minimum relative width requirement. The floating breakwater comprises of two pontoons rigidly connected together and each of the pontoons having a row of cylinders attached beneath, for improved performance characteristics. The laboratory tests were conducted in both regular and random wave flumes to study the dynamic behavior of the breakwater. Transmission and reflection coefficients, water surface elevations and velocities inside the cage like area provided in between the pontoons, rigid body motions floating breakwater and mooring forces were studied under regular and random waves and under the regular waves followed by a uniform current. The results proved the suitability of the floating breakwater to the field conditions even for large wave periods. In addition the variations in water particle kinematics, rigid body motion and mooring forces show nominal magnitudes when compared to the existing systems indicating the rigidness of the breakwater.

scholarly journals Hydrodynamic Performance of a Multi-Module Three-Cylinder Floating Breakwater System under the Influence of Reefs: A 3D Experimental Study

2021 ◽  
Vol 9 (12) ◽  
pp. 1364
Author(s):  
Jianting Guo ◽  
Yongbin Zhang ◽  
Chunyan Ji ◽  
Xiangqian Bian ◽  
Sheng Xu
Keyword(s):  
Wave Attenuation ◽  
Hydrodynamic Performance ◽  
Theoretical Research ◽  
Practical Significance ◽  
Large Wave ◽  
Motion Responses ◽  
Short Period ◽  
Floating Breakwater ◽  
Mooring Forces ◽  
Floating Breakwaters

As the technical and theoretical research of floating breakwaters is becoming increasingly mature, the floating breakwaters are now being utilized, especially in offshore reefs. Therefore, it is of practical significance to study the hydrodynamic performance of a multi-module floating breakwater system under the influence of reefs. In this study, a 3D model experiment was carried out on a system consisting of eight three-cylinder floating breakwater modules under the influence of reefs. A wave attenuation mesh cage was incorporated at the bottom of the model. The floating breakwater system was slack-moored in its equilibrium position, and each module was connected by elastic connectors. The reefs were modeled on a bathymetric map of existing reefs in the East China Sea. In this experiment, the wave transmission coefficients, motion responses, and mooring forces of the floating breakwater system were measured. The results showed that the three-cylinder floating breakwater in the beam waves (β = 90°) has excellent wave attenuating performance under the influence of reefs, especially for short-period waves. However, under the influence of the reef reflection wave and the shallow water effect, the motion responses in the three main stress directions of the floating breakwater were large, and there was some surge and pitch motion. Under the influence of the aggregation and superposition of reflected waves on both sides of the reefs, the peak mooring forces in the middle position of the floating breakwater system were the largest at large wave height. The three-cylinder floating breakwater exhibited satisfactory hydrodynamic performance under the influence of reefs. It has broad application prospects in offshore reefs.

Modeling and Simulations of the Motion of Bio-Inspired Micro Swimming Robots

2010 ◽  
Author(s):  
A. F. Tabak ◽  
S. Yesilyurt
Keyword(s):  
Finite Element ◽  
Rigid Body ◽  
Stokes Equations ◽  
Wave Length ◽  
Rigid Body Dynamics ◽  
Body Motion ◽  
Design Parameters ◽  
Driving Frequency ◽  
Mobility Matrix ◽  
Micro Organisms

Micro swimming robots that mimic the motion of micro organisms can carry out a variety of medical tasks including drug delivery, micro surgery and minimally invasive diagnostic tasks. Micro organisms such as spermatozoa and bacteria use their flagella to propel themselves. The artificial micro swimmer presented in this study is composed of a body that carries a medical payload, and one wave propagating tail attached to it. In this study, forces and torques exerted on the tail structure by the surrounding fluid are computed with the help of corresponding force coefficients. Rigid body dynamics computations are carried out by four-dimensional quaternion configuration to eliminate numerical error accumulation during matrix integrations, and, hence, instantaneous rotation matrix for rigid body rotation is extracted from the quaternion. Propulsive force obtained by waving tail is balanced by the drag force on the micro swimmers’ total wet surface and dynamic behavior of the micro swimmer is obtained as a rigid body motion. The effect of swimmer and waving geometry is parameterized to study the swimming behavior. Simulations carried out to explore the effect of wave length, wave amplitude, driving frequency. Translational and rotational velocities and hydrodynamic power requirements are presented for each individual set of design parameters. Validity of the model is tested by comparing the numerical results and finite element simulation results. Lastly, the model is modified to utilize the mobility matrix coefficients obtained from inertia eliminated finite element simulations governed by time dependent Navier-Stokes equations.

scholarly journals FLOATING BREAKWATER RESPONSE TO WAVE ACTION

1988 ◽  
Vol 1 (21) ◽  
pp. 162 ◽  
Author(s):  
Michael Isaacson ◽  
Ronald Byres
Keyword(s):  
Numerical Model ◽  
Experimental Testing ◽  
Diffraction Theory ◽  
Regular Waves ◽  
Transmission Coefficients ◽  
Floating Breakwater ◽  
Mooring Forces ◽  
Wave Drift Forces ◽  
Floating Breakwaters ◽  
Incident Waves

The present paper describes a study carried out to investigate floating breakwater behavior in waves. Components of the study include a field survey of floating breakwaters in British Columbia, Canada, the development of a numerical model of breakwater behavior and the experimental testing of a particular breakwater design. The numerical model has been developed to provide breakwater motions, transmission coefficients and mooring forces. The model combines linear diffraction theory for obliquely incident waves, a mooring analysis, the inclusion of viscous damping coefficients obtained from experimental or field data, and the inclusion of drag and wave drift forces for use in the static analysis of the moorings. The experiments were carried out with normally incident regular waves of different heights and periods. Preliminary results indicate that the numerical model should prove to be a useful tool in floating breakwater design.

scholarly journals RIGID BODY MOTION OF A FLOATING BREAKWATER

1984 ◽  
Vol 1 (19) ◽  
pp. 179
Author(s):  
Robert W. Miller ◽  
Derald R. Christensen
Keyword(s):  
Dynamic Response ◽  
Rigid Body ◽  
Frequency Domain ◽  
Field Measurements ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Full Scale ◽  
Body Motion ◽  
Floating Breakwater ◽  
Scale Field

Predictions of the dynamic response of a floating breakwater obtained from a frequency domain analysis are compared with full-scale field measurements. Those parameters prominently affecting accurate response predictions are identified and discussed.

scholarly journals Viscous Flow Around a Rigid Body Performing a Time-periodic Motion

2021 ◽  
Vol 23 (1) ◽  
Author(s):  
Thomas Eiter ◽  
Mads Kyed
Keyword(s):  
Rigid Body ◽  
Sobolev Spaces ◽  
Periodic Motion ◽  
Viscous Incompressible Fluid ◽  
Body Motion ◽  
Translational Velocity ◽  
Ill Posed ◽  
Homogeneous Sobolev Spaces ◽  
The Mean ◽  
Time Periodic

AbstractThe equations governing the flow of a viscous incompressible fluid around a rigid body that performs a prescribed time-periodic motion with constant axes of translation and rotation are investigated. Under the assumption that the period and the angular velocity of the prescribed rigid-body motion are compatible, and that the mean translational velocity is non-zero, existence of a time-periodic solution is established. The proof is based on an appropriate linearization, which is examined within a setting of absolutely convergent Fourier series. Since the corresponding resolvent problem is ill-posed in classical Sobolev spaces, a linear theory is developed in a framework of homogeneous Sobolev spaces.

scholarly journals Representative Transmission Coefficient for Evaluating the Wave Attenuation Performance of 3D Floating Breakwaters in Regular and Irregular Waves

2021 ◽  
Vol 9 (4) ◽  
pp. 388
Author(s):  
Huu Phu Nguyen ◽  
Jeong Cheol Park ◽  
Mengmeng Han ◽  
Chien Ming Wang ◽  
Nagi Abdussamie ◽  
...  
Keyword(s):  
Transmission Coefficient ◽  
Wave Height ◽  
Wave Attenuation ◽  
Transmitted Wave ◽  
Irregular Waves ◽  
Hydrodynamic Analysis ◽  
Evaluation Approach ◽  
Floating Breakwater ◽  
Floating Breakwaters ◽  
Evaluation Approaches

Wave attenuation performance is the prime consideration when designing any floating breakwater. For a 2D hydrodynamic analysis of a floating breakwater, the wave attenuation performance is evaluated by the transmission coefficient, which is defined as the ratio between the transmitted wave height and the incident wave height. For a 3D breakwater, some researchers still adopted this evaluation approach with the transmitted wave height taken at a surface point, while others used the mean transmission coefficient within a surface area. This paper aims to first examine the rationality of these two evaluation approaches via verified numerical simulations of 3D heave-only floating breakwaters in regular and irregular waves. A new index—a representative transmission coefficient—is then presented for one to easily compare the wave attenuation performances of different 3D floating breakwater designs.

A planar reconfigurable linear rigid-body motion linkage with two operation modes

2014 ◽  
Vol 228 (16) ◽  
pp. 2985-2991 ◽  
Author(s):  
Guangbo Hao ◽  
Xianwen Kong ◽  
Xiuyun He
Keyword(s):  
Rigid Body ◽  
Single Mode ◽  
Rigid Body Motion ◽  
Body Motion ◽  
Reference Guide ◽  
Revolute Joints ◽  
Operation Modes ◽  
Straight Line ◽  
Motion Stage ◽  
Motion Mode

A planar reconfigurable linear (also rectilinear) rigid-body motion linkage (RLRBML) with two operation modes, that is, linear rigid-body motion mode and lockup mode, is presented using only R (revolute) joints. The RLRBML does not require disassembly and external intervention to implement multi-task requirements. It is created via combining a Robert’s linkage and a double parallelogram linkage (with equal lengths of rocker links) arranged in parallel, which can convert a limited circular motion to a linear rigid-body motion without any reference guide way. This linear rigid-body motion is achieved since the double parallelogram linkage can guarantee the translation of the motion stage, and Robert’s linkage ensures the approximate straight line motion of its pivot joint connecting to the double parallelogram linkage. This novel RLRBML is under the linear rigid-body motion mode if the four rocker links in the double parallelogram linkage are not parallel. The motion stage is in the lockup mode if all of the four rocker links in the double parallelogram linkage are kept parallel in a tilted position (but the inner/outer two rocker links are still parallel). In the lockup mode, the motion stage of the RLRBML is prohibited from moving even under power off, but the double parallelogram linkage is still moveable for its own rotation application. It is noted that further RLRBMLs can be obtained from the above RLRBML by replacing Robert’s linkage with any other straight line motion linkage (such as Watt’s linkage). Additionally, a compact RLRBML and two single-mode linear rigid-body motion linkages are presented.

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