Irregular Wave and Current Loads on a Fish Farm System

2018 ◽  
Author(s):  
Arnt G. Fredriksen ◽  
Basile Bonnemaire ◽  
Øyvind Nilsen ◽  
Leiv Aspelund ◽  
Andreas Ommundsen
Keyword(s):  
Particle Velocity ◽  
Fish Farm ◽  
Fluid Particle ◽  
Irregular Waves ◽  
Engineering Practice ◽  
Irregular Wave ◽  
Environmental Force ◽  
The Mean ◽  
Particle Velocities ◽  
Farm System

Accurate calculation of the design mooring loads on an aquaculture fish farm mooring system is often a difficult task. The fish farm system has a large horizontal extension with variable environmental conditions across the entire structure. In addition, the drag loads on the fish nets are thought to be the governing environmental force. This means that the mean position of the fish farm is a function of the mean of the fluid particle velocity squared, where the fluid particle velocity must be taken as the sum of current and wave induced fluid particle velocities. Additional offsets will be slowly varying, where the response time will depend on the total mooring stiffness. The magnitudes depend on the height and length on wave groups in the irregular sea state. The paper presents simulations of the response of such a system to a set of combined irregular waves and current conditions. The response evolution in time is discussed as well as parameters affecting the maximum responses in the systems (displacements and loads). Finally, the resulting loads on the fish farm in irregular waves are compared to loads obtained in equivalent regular waves, as this is an often used engineering practice when analyzing the response and mooring loads of a fish farm.

Diffusion in free turbulent shear flows

1957 ◽  
Vol 3 (1) ◽  
pp. 67-80 ◽  
Author(s):  
G. K. Batchelor
Keyword(s):  
Time Scales ◽  
Particle Velocity ◽  
Random Function ◽  
Shear Flows ◽  
Fluid Particle ◽  
Turbulent Shear ◽  
Mean Flow ◽  
Turbulent Shear Flows ◽  
The Mean ◽  
Stationary Random Function

This paper is concerned with some statistical properties of the displacement of a marked fluid particle released from a given position in a turbulent shear flow, and in particular with the dispersion about the mean position after a long time. It is known that the dispersion takes a simple asymptotic form when the particle velocity is a stationary random function of time, and that analogous results are obtainable when the particle velocity can be transformed to a stationary random function by suitable stretching of the velocity and time scales. The basic hypothesis of the paper is that, in steady free turbulent shear flows which are generated at a point and have a similar structure at different stations downstream, the velocity of a fluid particle exhibits a corresponding Lagrangian similarity and can be so transformed to a stationary random function.The velocity and time scales characterizing the motion of a fluid particle at time t after release at the origin are determined in terms of the powers with which the Eulerian length and velocity scales of the turbulence vary with distance x from the origin. The time scale has the same dependence on t for all jets, wakes and mixing layers (and also for decaying homogeneous turbulence) possessing the usual kind of Eulerian similarity. The dispersion of a particle in the longitudinal or mean-flow direction (and likewise that in the lateral direction in cases of two-dimensional mean flow) is found to vary with t in such a way as to be proportional to the thickness of the shear layer at the mean position of the particle. The way in which the maximum value of the mean concentration of marked fluid falls off with t (for release of a single particle) or with x (for continuous release) is also found.

scholarly journals WAVE FORCES INDUCED BY IRREGULAR WAVES ON A VERTICAL CIRCULAR CYLINDER

1978 ◽  
Vol 1 (16) ◽  
pp. 144 ◽  
Author(s):  
Hajime Ishida ◽  
Yuichi Iwagaki
Keyword(s):  
Circular Cylinder ◽  
Laboratory Experiments ◽  
Large Diameter ◽  
Small Diameter ◽  
Diffraction Theory ◽  
Irregular Waves ◽  
Wave Forces ◽  
Irregular Wave ◽  
Water Level Variations ◽  
Particle Velocities

In order to examine the irregular wave forces on a small diameter cylinder, laboratory experiments have been conducted on water particle velocities and wave forces with various kinds of irregular waves. As the results, it is indicated that the time variation and the spectral distribution of wave forces can be calculated adequately from the water level variations by using the methods proposed by Reid1' and Borgman2' respectively. Moreover, with respect to the irregular wave forces on a large diameter cylinder, a new calculation method was shown by means of applying Reid's linear filters1' to MacCamy and Fuchs's diffraction theory.

scholarly journals A NEW DESIGN METHOD OF RUBBLE MOUND STRUCTURES

1986 ◽  
Vol 1 (20) ◽  
pp. 161 ◽  
Author(s):  
Cheong-Ro Ryu ◽  
Toru Sawaragi
Keyword(s):  
Design Method ◽  
Wave Train ◽  
Wave Force ◽  
Irregular Waves ◽  
Wave Condition ◽  
Irregular Wave ◽  
The Mean ◽  
Rubble Mound ◽  
Run Up ◽  
Wave Control

A new design method of rubble mound structures with stability and wave control consideration is proposed, by which the reduction of wave reflection and run-up and increase in rubble stability are assured under the given wave conditions. Wave control and stability increasing functions due to change of the slope shape of rubble mound structures are discussed on the basis of the experimental results for regular and irregular waves. The new design formula developed here considered the allowable percentage of damage and the wave grouping effects on rubble stability using a new assumption of the mean run-sum as an index of the irregular wave force. The run-sum is defined as the energy sum of a run satisfying a critical wave condition and the mean run-sum is the mean of run-sum for a irregular wave train.

Alternative Methodologies for Subsea Flexible Strength Analysis

2018 ◽  
Author(s):  
Anskey A. Miranda ◽  
Fred P. Turner ◽  
Nigel Barltrop
Keyword(s):  
Real World ◽  
Wave Train ◽  
Irregular Waves ◽  
Wave Crest ◽  
Strength Analysis ◽  
New Wave ◽  
Regular Wave ◽  
Wave Analysis ◽  
Sea State ◽  
Irregular Wave

This paper presents a study of the analysis methodologies used to predict the most likely response of flexibles in a subsea environment, with the aim of determining an efficient and reliable prediction methodology. The most accurate method involves simulating multiple wave realisations of a real world sea state, i.e. irregular waves, and post-processing the results to determine the most probable maximum (MPM). Due to the computationally intensive nature of this approach, however, regular wave analysis is typically used to determine flexible response. This approach considers the maximum wave within a design storm at a desired period; the choice of periods may leave room for uncertainty in the conservatism of the approach. With proper screening, regular wave analysis can be a valid yet overly conservative approach resulting in over design and additional cost. However, if screened incorrectly, there is a possibility that the choice of periods could give results that are under conservative. In addition to regular wave analysis, the paper presents two alternative methodologies to determine the most likely response, with the focus on reducing the computational resources required. The first alternative is an ‘Irregular Wave Screen’ approach in which the wave train is screened at areas of interest for waves within a user defined threshold of the maximum wave height, in addition to other user defined parameters. Only waves within these parameters are simulated to determine responses. The second alternative is the ‘New Wave’ approach, which models the most probable wave elevation around the maximum wave crest. The calculated new wave is then placed at the desired location to determine responses. The responses of the Regular, Irregular Wave Screen and New Wave methodologies are compared with the Irregular MPM approach to determine their feasibility to predict the response of flexibles in a real world irregular sea state with lower computational requirements.

scholarly journals ESTIMATION OF WATER PARTICLE VELOCITIES OF SHALLOW WATER WAVES BY A MODIFIED TRANSFER FUNCTION METHOD

1986 ◽  
Vol 1 (20) ◽  
pp. 33 ◽  
Author(s):  
Hirofumi Koyama ◽  
Koichiro Iwata
Keyword(s):  
Transfer Function ◽  
Shallow Water ◽  
Approximate Method ◽  
Stream Function ◽  
Water Waves ◽  
Function Method ◽  
Finite Amplitude ◽  
Water Particle ◽  
Irregular Wave ◽  
Particle Velocities

This paper Is intended to propose a simple, yet highly reliable approximate method which uses a modified transfer function in order to evaluate the water particle velocity of finite amplitude waves at shallow water depth in regular and irregular wave environments. Using Dean's stream function theory, the linear function is modified so as to include the nonlinear effect of finite amplitude wave. The approximate method proposed here employs the modified transfer function. Laboratory experiments have been carried out to examine the validity of the proposed method. The approximate method is shown to estimate well the experimental values, as accurately as Dean's stream function method, although its calculation procedure is much simpler than that of Dean's method.

scholarly journals STATISTICAL PROPERTIES OF THE MAXIMUM RUN OF IRREGULAR SEA WAVES

1988 ◽  
Vol 1 (21) ◽  
pp. 48 ◽  
Author(s):  
Akira Kimura
Keyword(s):  
Probability Distribution ◽  
Wave Height ◽  
Probability Distributions ◽  
Confidence Regions ◽  
Statistical Properties ◽  
Irregular Waves ◽  
Sea Waves ◽  
Sea State ◽  
Irregular Wave ◽  
Distribution Of The Maximum

The probability distribution of the maximum run of irregular wave height is introduced theoretically. Probability distributions for the 2nd maximum, 3rd maximum and further maximum runs are also introduced. Their statistical properties, including the means and their confidence regions, are applied to the verification of experiments with irregular waves in the realization of a "severe sea state" in the test.

scholarly journals LABORATORY STUDY ON TWO-DIMENSIONAL BEACH TRANSFORMATION DUE TO IRREGULAR WAVES

1986 ◽  
Vol 1 (20) ◽  
pp. 102 ◽  
Author(s):  
Nubuo Mimura ◽  
Yukinori Otsuka ◽  
Akira Watanabe
Keyword(s):  
Wave Train ◽  
Irregular Waves ◽  
Two Dimensional ◽  
Beach Profile ◽  
Irregular Wave ◽  
Sand Ripple ◽  
Ripple Formation ◽  
Sand Movement ◽  
Incident Waves ◽  
Profile Change

In the present study, effects of irregular waves on two-dimensional beach transformation and related phenomena were investigated through a series of laboratory experiments. Attempts were made to determine a representative wave of irregular wave trains which controlled individual phenomenon related to the two-dimensional beach profile change. It was found that the representative wave is different for each phenomenon. For the macroscopic beach profile change, it is the mean wave which represents whole incident waves. On the other hand, some of microscopic phenomena, such as initiation of sand movement and sand ripple formation, are controlled by larger waves in the wave train selectively, of which representative wave is the significant wave.

scholarly journals Study on determination method of hydrodynamic coefficient of Marine pile foundation

2020 ◽  
Vol 143 ◽  
pp. 01021
Author(s):  
Jiang Zongnan
Keyword(s):  
Fourier Analysis ◽  
Time History ◽  
Least Square Method ◽  
Wave Force ◽  
Least Square ◽  
Irregular Waves ◽  
Hydrodynamic Coefficient ◽  
Irregular Wave ◽  
Advantages And Disadvantages ◽  
The Moment

The irregular waves are simulated by using standard spectrum. Instantaneous value method, Fourier analysis method, least square method and "harbour hydrological code" are used to determine the moment force of coefficient CM and drag coefficient CD. Then CM and CD that linearized by Borgman L.E. equation are substituted into Morison equation. The time history curve of the wave force on the pile is calculated and compared with the measured wave force data under the action of irregular wave to analyze the advantages and disadvantages of several methods to determine CM and CD. The results show that the comparison between CM and CD determined by Fourier analysis and least square method is practical.

Influence of Multidirectional Irregular Wave Sampling to Second-Order Hydroelastic Responses of VLFS

2009 ◽  
Author(s):  
Xujun Chen ◽  
Torgeir Moan ◽  
Xuefeng Tang
Keyword(s):  
Computer Time ◽  
Second Order ◽  
Irregular Waves ◽  
Floating Structure ◽  
First Order ◽  
Fluid Forces ◽  
Irregular Wave ◽  
Very Large Floating Structure ◽  
Principal Coordinates ◽  
Hydroelastic Response

Hydroelasticity theory considering the second-order fluid forces induced by the coupling of first-order wave potentials is introduced briefly in this paper. Based on this theory, four types of multidirectional irregular wave samplings are introduced, the frequency steps Δω of the four samplings are 0.04, 0.04, 0.02 and 0.01 rad/s, and the corresponding numbers of wave components N are 17, 75, 147 and 285 respectively. The result of principal coordinates and displacements of a very large floating structure (VLFS) for the four types of sampling are presented and discussed. The influence of the sampling is analyzed. The conclusions show that the sampling of the multidirectional irregular waves influence the second-order hydroelastic response of the VLFS. The accuracy and the computer time of the calculating with sampling of frequency step Δω = 0.02 rad/s are acceptable.

Optical studies on the turbulent motion of solid particles in a pipe flow

1991 ◽  
Vol 231 ◽  
pp. 665-688 ◽  
Author(s):  
James B. Young ◽  
Thomas J. Hanratty
Keyword(s):  
Diffusion Coefficient ◽  
Particle Velocity ◽  
Turbulent Diffusion ◽  
Slip Velocity ◽  
Rate Of Change ◽  
Solid Particles ◽  
Mean Square ◽  
Turbulent Diffusion Coefficient ◽  
Fluid Turbulence ◽  
The Mean

An extension of an axial viewing optical technique (first used by Lee, Adrian & Hanratty) is described which allows the determination of the turbulence characteristics of solid particles being transported by water in a pipe. Measurements are presented of the mean radial velocity, the mean rate of change radial velocity, the mean-square of the radial and circumferential fluctuations, the Eulerian turbulent diffusion coefficient, and the Lagrangian turbulent diffusion coefficient. A particular focus is to explore the influence of slip velocity for particles which have small time constants. It is found that with increasing slip velocity the magnitude of the turbulent velocity fluctuations remains unchanged but that the turbulent diffusivity decreases. The measurements of the average rate of change of particle velocity are consistent with the notion that particles move from regions of high fluid turbulence to regions of low fluid turbulence. Measurements of the root-mean-square of the fluctuations of the rate of change of particle velocity allow an estimation of the average magnitude of the particle slip in a highly turbulent flow, which needs to be known to analyse the motion of particles not experiencing a Stokes drag.

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