Experimental Study on Interaction Between Waves and Netting: Damping Effects and Forces

2007 ◽  
Author(s):  
Pa˚l F. Lader ◽  
Atle Jensen ◽  
Johan Kristian Sveen ◽  
Arne Fredheim ◽  
Anna Olsen ◽  
...  
Keyword(s):  
Fish Farming ◽  
Open Ocean ◽  
Wave Forces ◽  
Incoming Wave ◽  
Wave Flume ◽  
Narrow Wave ◽  
Damping Effects ◽  
University Of Oslo ◽  
Open Ocean Aquaculture ◽  
Nonlinear Energy

One of the possibilities to expand sea-based fish farming is to move the aquaculture installations away from the conflicts of the coastal zone, and into more open ocean locations. However, open ocean aquaculture puts other demands on the structures than aquaculture in sheltered locations, and in this context it is necessary to understand the behaviour of the aquaculture structures as they are exposed to large sea-loads from waves and current. Flexible netting is a main part of most sea-based aquaculture structures, and in this paper the interaction between waves and netting is studied. Experiments were conducted at the narrow wave flume facility at the University of Oslo, Norway, where several different regular wave cases were run through netting with different solidity. The wave energy was measured after the wave had passed through the net and compared with the energy of an undisturbed wave to assess the wave damping properties of the net. The vertical and horizontal forces were also measured. The findings show that the damping effects of the netting are not necessarily correlated with the wave forces, indicated complex nonlinear processes contributing to the fluid-net interaction. The amount of nonlinear energy in the wave and force waveforms is also investigated, and it is shown that the nonlinear energy in the incoming wave results in an even higher level of nonlinear components in the forces experienced by the net.

Open Ocean Aquaculture Engineering: System Design and Physical Modeling

2000 ◽  
Vol 34 (1) ◽  
pp. 41-52 ◽  
Author(s):  
David W. Fredriksson ◽  
Erik Muller ◽  
Kenneth Baldwin ◽  
M. Robinson Swift ◽  
Barbaros Celikkol
Keyword(s):  
Physical Model ◽  
New Hampshire ◽  
Open Ocean ◽  
Mooring Line ◽  
Wave Forces ◽  
Engineering System ◽  
Anchor System ◽  
Rigid Frame ◽  
Comparison Of The Results ◽  
Open Ocean Aquaculture

An open ocean aquaculture net pen system was developed and deployed for an exposed demonstration site south of the Isles of Shoals, New Hampshire in 55 meters of water. This component of the project is part of an interdisciplinary effort at the University of New Hampshire involving engineers, biologists, economists and commercial fishermen. Initially, two cages were specified for the growout of summer flounder (Paralichthys dentatus). The design process included physical model testing conducted in a wave/tow tank using 1/22.5 scale models. To select an optimum system, experiments were performed using gravity-type and central spar-type cages. Vertical taut line and catenary moorings were evaluated. Data acquisition included drag and wave forces on the cages, mooring line forces and heave, pitch and surge motion of the cages.After comparison of the results and holding a design review including outside experts, a central spar configuration was selected for both cages. This system exhibited both reduced force loadings and less extreme motion, and its rigid frame would resist volume changes under storm conditions. In the final mooring design, each cage was separately deployed using a four anchor system to ensure redundancy. A mid-depth, square, horizontal grid was employed in order to reduce anchor footprint area, which is very expensive under New Hampshire permit rules. Mooring system components were sized to meet loadings scaled up from the physical model results. The system was deployed in June of 1999 and has performed well in all weather forcing conditions to date.

scholarly journals MODEL TESTS WITH DIRECTLY REPRODUCED NATURE WAVE TRAINS

1974 ◽  
Vol 1 (14) ◽  
pp. 20 ◽  
Author(s):  
Helge Gravesen ◽  
Ebbe Fredericksen ◽  
Jens Kirkegaard
Keyword(s):  
Wave Model ◽  
Short Wave ◽  
Model Tests ◽  
Wave Forces ◽  
Wave Direction ◽  
Incoming Wave ◽  
Irregular Wave ◽  
Wave Flume ◽  
Wave Heights ◽  
Stability Of Structures

Hydraulic model tests are still recognized as the best and in many cases the only tool, indeed, for investigations of design criteria for harbours concerning a) the effect of wave disturbance on moored ships in harbour basins and at offshore terminals, b) stability of structures and wave forces on structures. Model tests with waves have until recently usually been made with regular waves varying the wave height, wave period, wave direction for each test run. An important improvement in the model technique has been the development of irregular wave generators, capable of generating waves directly from nature wave records. The following aspects are presented below 1) A discussion on the methodology of wave model tests. 2) A method for direct reproduction of nature wave records. 3) A method for determining the incoming wave heights in a short wave flume with a reflecting structure and reflection from the wave generator paddle.

The Concept of the Optimum Alignment of Discharge Pipelines Due to the Minimization of the Wave Forces

1992 ◽  
Vol 25 (9) ◽  
pp. 211-216
Author(s):  
A. Akyarli ◽  
Y. Arisoy
Keyword(s):  
Wave Height ◽  
Wave Force ◽  
Wave Forces ◽  
Wave Direction ◽  
Incoming Wave ◽  
Pipeline Route ◽  
Optimum Alignment ◽  
The Cost ◽  
Resultant Wave

As the wave forces are the function of the wave height, period and the angle between the incoming wave direction and the axis of the discharge pipeline, the resultant wave force is directly related to the alignment of the pipeline. In this paper, a method is explained to determine an optimum pipeline route for which the resultant wave force becomes minimum and hence, the cost of the constructive measures may decrease. Also, the application of this method is submitted through a case study.

scholarly journals Determination of Force Coefficients for a Submerged Rigid Breakwater under the Action of Solitary Waves

Water ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 315
Author(s):  
Francesco Aristodemo ◽  
Giuseppe Tripepi ◽  
Luana Gurnari ◽  
Pasquale Filianoti
Keyword(s):  
Solitary Waves ◽  
Pressure Sensors ◽  
Wave Forces ◽  
Wave Loads ◽  
Force Coefficients ◽  
Wave Flume ◽  
Physical Tests ◽  
The Difference ◽  
The University ◽  
Semi Empirical

We present an analysis related to the evaluation of Morison and transverse force coefficients in the case of a submerged square barrier subject to the action of solitary waves. To this purpose, two-dimensional experimental research was undertaken in the wave flume of the University of Calabria, in which a rigid square barrier was provided by a discrete battery of pressure sensors to determine the horizontal and vertical hydrodynamic forces. A total set of 18 laboratory tests was carried out by varying the motion law of a piston-type paddle. Owing to the low Keulegan–Carpenter numbers of the tests, the force regime of the physical tests was defined by the dominance of the inertia loads in the horizontal direction and of the lift loads in the vertical one. Through the use of the time series of wave forces and the undisturbed kinematics, drag, horizontal inertia, lift, and vertical inertia coefficients in the Morison and transverse semi-empirical schemes were calculated using time-domain approaches, adopting the WLS1 method for the minimization of the difference between the maximum forces and the linked phase shifts by comparing laboratory and calculated wave loads. Practical equations to calculate these coefficients as a function of the wave non-linearity were introduced. The obtained results highlighted the prevalence of the horizontal forces in comparison with the vertical ones which, however, prove to be fundamental for stability purposes of the barrier. An overall good agreement between the experimental forces and those calculated by the calibrated semi-empirical schemes was found, particularly for the positive horizontal and vertical loads. The analysis of the hydrodynamic coefficients showed a decreasing trend for the drag, horizontal inertia, and lift coefficients as a function of the wave non-linearity, while the vertical inertia coefficient underlined an initial increasing trend and a successive slight decreasing trend.

Measurement of organic loading under an open-ocean aquaculture cage, using sediment traps on the bottom

2007 ◽  
Vol 23 (6) ◽  
pp. 661-667 ◽  
Author(s):  
P. Rapp ◽  
W. R. Ramírez ◽  
J. A. Rivera ◽  
M. Carlo ◽  
R. Luciano
Keyword(s):  
Sediment Traps ◽  
Open Ocean ◽  
Organic Loading ◽  
Open Ocean Aquaculture

Tensegrity Structures in the Design of Flexible Structures for Offshore Aquaculture

2007 ◽  
Author(s):  
O̸sten Jensen ◽  
Anders Sunde Wroldsen ◽  
Pa˚l Furset Lader ◽  
Arne Fredheim ◽  
Mats Heide ◽  
...  
Keyword(s):  
Flexible Structures ◽  
Weather Conditions ◽  
High Energy ◽  
Open Ocean ◽  
Element Analysis ◽  
Tensegrity Structures ◽  
Stiffness Properties ◽  
Offshore Aquaculture ◽  
And Performance ◽  
Open Ocean Aquaculture

Aquaculture is the fastest growing food producing sector in the world. Considerable interest exists in developing open ocean aquaculture in response to a shortage of suitable, sheltered inshore locations. The harsh weather conditions experienced offshore lead to a focus on new structure concepts, remote monitoring and a higher degree of automation in order to keep the cost of structures and operations within an economically viable range. This paper proposes tensegrity structures in the design of flexible structures for offshore aquaculture. The finite element analysis program ABAQUS™ has been used to investigate stiffness properties and performance of tensegrity structures when subjected to various forced deformations and hydrodynamic load conditions. The suggested concept, the tensegrity beam, shows promising stiffness properties in tension, compression and bending, which are relevant for development of open ocean aquaculture construction for high energy environments. When designing a tensegrity beam, both pre-stress and spring stiffness should be considered to ensure the desired structural properties. A large strength to mass ratio and promising properties with respect to control of geometry, stiffness and vibration could make tensegrity an enabling technology for future developments.

Experimental Study of Wave Force Distribution on a Monopile Structure

2018 ◽  
Author(s):  
Malene H. Vested ◽  
Stefan Carstensen ◽  
Erik Damgaard Christensen
Keyword(s):  
Experimental Studies ◽  
Cost Effective ◽  
Wave Force ◽  
Offshore Wind ◽  
Irregular Waves ◽  
Force Distribution ◽  
Wave Forces ◽  
Total Force ◽  
Wave Flume ◽  
Effective Manner

As the demand for offshore wind energy continues to grow, the strive to understand the wave forces acting on the substructure of the wind turbines continues. In regard to wind turbine design, it is vital to consider not only the total wave force, but also the local wave forces. Local forces are particularly important for the design of secondary structures as e.g. mooring platforms. Typically, however, experimental studies mainly concern total forces or idealized local forces. We present here a rather simple way to measure local forces along a model monopile. The study is conducted in a wave flume of 28 m in length, in which waves are generated by a piston-type wave maker at a water depth of 0.515 m and shoal onto a bed of slope 1:25. A model monopile is installed and subjected to forcing from a series of both regular and irregular waves. In the experimental set-up, the model monopile is fixed at the bottom and the top and consists of seven independent cylindrical sections. The cylindrical sections are connected by force transducers which measure local shear, and so the associated local forces may be determined. The measured local forces are compared to the force distribution given by Morisons equation combined with linear theory and Wheeler stretching, which is a force estimate commonly used in the industry. This study shows that the total force is rather well captured by Morison’s equation. The force distribution estimated from Morison’s equation, however, shows larger discrepancies from the measured forces. This encourages for further measurements. In this study, we show that it is possible to measure force distribution on a model monopile in a simple and cost-effective manner. The aim is here to demonstrate the method and we will later present a larger body of work associated with the outcome of the measurements.

Environmental impacts of brass mesh nets on open ocean aquaculture pens in tropical marine environments

Aquaculture ◽  
2020 ◽  
Vol 524 ◽  
pp. 735266
Author(s):  
Tyler Sclodnick ◽  
Steve Sutton ◽  
Thomas Selby ◽  
Robert Dwyer ◽  
Langley Gace
Keyword(s):  
Environmental Impacts ◽  
Open Ocean ◽  
Marine Environments ◽  
Open Ocean Aquaculture

scholarly journals WAVE FORCES ON SQUARE CAISSONS

1976 ◽  
Vol 1 (15) ◽  
pp. 132 ◽  
Author(s):  
G.R. Mogridge ◽  
W.W. Jamieson
Keyword(s):  
Experimental Data ◽  
Theoretical Method ◽  
Wave Forces ◽  
Simple Method ◽  
Method Of Calculation ◽  
Wave Flume ◽  
Wide Range ◽  
Wave Heights ◽  
And Storage ◽  
Water Depths

The forces and overturning moments exerted by waves on large vertical square-section caissons have been measured in the laboratory. Each model caisson extended from the bottom of a wave flume through the water surface and was oriented either with one side perpendicular to the direction of wave propagation or turned through an angle of forty-five degrees to this position. For a given orientation, each model was tested for a range of wave heights (up to the point of breaking) for various wave periods and water depths. A digital computer was used for the acquisition, processing, plotting and storage of the experimental data. In addition to the experimental work, an approximate theoretical method is presented which allows the wave loadings on a square caisson to be estimated by means of a simple desk calculation. The experimental data shows that this simple method of calculation is reasonably accurate over a wide range of wave conditions and caisson sizes.

Sign in / Sign up

Export Citation Format

Share Document