Average Flow Inside and Around Fish Cages With and Without Fouling in a Uniform Flow

2010 ◽  
Author(s):  
Lars Gansel ◽  
Thomas A. McClimans ◽  
Dag Myrhaug
Keyword(s):  
Flow Field ◽  
Numerical Models ◽  
Fish Farming ◽  
Reynolds Numbers ◽  
Uniform Flow ◽  
Metal Mesh ◽  
Average Flow ◽  
Fish Cages ◽  
Farming Industry ◽  
Porous Cylinders

The average flow field inside and around the bottom of porous cylinders in a uniform flow is explored using Particle Image Velocimetry (PIV). Tests were conducted on six cylinders with porosities of 0%, 30%, 60%, 75%, 82% and 90% in a flume tank where the flow field inside and around the models is time averaged over 180 seconds. The models had a height-to-diameter ratio of 3 and were made from metal mesh. The Reynolds numbers ranged from 5,000 to 20,000 based on the diameter of the models and from 75 to 300 based on the diameter of individual strands of the mesh, which corresponds to the Reynolds numbers occurring at salmon fish cage netting used along the Norwegian coast. The porosities of 82%, 75% and 60% correspond to those of a fish cage netting in Norwegian Salmon farming with no, light and heavy biofouling, respectively. The results from this study are discussed with respect to the instantaneous flow field in and around the same cylinders at identical Reynolds numbers. The focus is on the effect of porosity on the ventilation inside the cages and the vertical transports within the near wake. It is shown that heavy fouling of aquacultural nettings can lead to internal circulation inside fish cages and therefore has the potential to reduce the ventilation of the net pens dramatically. The description of the time-averaged flow field inside and around porous cylinders can be used as benchmarks to validate and adjust numerical models of the flow past porous cylinders. The results from this study can be valuable also for the fish farming industry, as bio-fouling and the reduced porosity of fish cages can be monitored and controlled directly by fish farmers.

Average Flow Inside and Around Fish Cages With and Without Fouling in a Uniform Flow

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Lars C. Gansel ◽  
Thomas A. McClimans ◽  
Dag Myrhaug
Keyword(s):  
Flow Field ◽  
Numerical Models ◽  
Fish Farming ◽  
Reynolds Numbers ◽  
Uniform Flow ◽  
Metal Mesh ◽  
Average Flow ◽  
Fish Cages ◽  
Farming Industry ◽  
Porous Cylinders

The average flow field inside and around the bottom of porous cylinders in a uniform flow is explored using particle image velocimetry (PIV). Tests were conducted on six cylinders with porosities of 0%, 30%, 60%, 75%, 82%, and 90% in a flume tank where the flow field inside and around the models is time averaged over 180 s. The models had a height-to-diameter ratio of 3 and were made from metal mesh. The Reynolds numbers ranged from 5000 to 20,000 based on the diameter of the models and from 75 to 300 based on the diameter of individual strands of the mesh, which corresponds to the Reynolds numbers occurring at salmon fish cage netting used along the Norwegian coast. The porosities of 82%, 75%, and 60% correspond to those of a fish cage netting in Norwegian salmon farming with no, light, and heavy biofouling, respectively. The results from this study are discussed with respect to the instantaneous flow field in and around the same cylinders at identical Reynolds numbers. The focus is on the effect of porosity on the ventilation inside the cages and the vertical transports within the near wake. It is shown that heavy fouling of aquacultural netting can lead to internal circulation inside fish cages and, therefore, has the potential to dramatically reduce the ventilation of the net pens. The description of the time-averaged flow field inside and around porous cylinders can be used as benchmarks to validate and adjust numerical models of the flow past porous cylinders. The results from this study can also be valuable for the fish farming industry, since bio-fouling and the reduced porosity of fish cages can be monitored and controlled directly by fish farmers.

Flow Around the Free Bottom of Fish Cages in a Uniform Flow With and Without Fouling

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Lars C. Gansel ◽  
Thomas A. McClimans ◽  
Dag Myrhaug
Keyword(s):  
Reynolds Number ◽  
Fish Farming ◽  
Distribution Patterns ◽  
Reynolds Numbers ◽  
Uniform Flow ◽  
Metal Mesh ◽  
Commercial Fish ◽  
Clean Fish ◽  
Fish Cages ◽  
Net Cages

This paper explores the flow around fish cages in a uniform flow with the focus on the flow patterns close to the bottom of the models. Towing tests were conducted with six straight cylinders with the porosities 0%, 30%, 60%, 75%, 82%, and 90%, two cylinders with an inclination of 12.5 deg, and the porosities 0% and 75% and two cylinders with an inclination of 25 deg and the porosities 0% and 75%. The models all had a height-to-diameter ratio of 3 and were made from metal mesh. The Reynolds number was 5000 based on the diameter of the models and 15 based on the diameter of individual strings of the mesh for all tests. Particle image velocimetry, a nonintrusive optical technique, was used to analyze the flow around the models in the plane of symmetry through the center of the cylinders. The porosities of 82%, 75%, and 60% correspond to those of a clean fish cage netting in Norwegian Salmon farming with no fouling, light fouling, and heavy fouling, respectively. The inclinations of 12.5 deg and 25 deg reflect the inclination of the net of a commercial fish cage in a slow and a fast current, respectively. The Reynolds number of the strings was within the range of Reynolds numbers occurring on fish cages along the Norwegian coast. The results from this study are discussed with respect to the flow around and through the same models at identical Reynolds numbers. It is shown that the inclination of the net cage and fouling of the netting have major effects on the flow pattern around fish cages. The flow around and through net cages defines the water exchange within fish cages and the distribution patterns of particles and nutrients released from a net-pen. The information provided in this study can be valuable for the fish farming industry, as the decrease of the porosity due to fouling, as well as the deformation of the netting of fish cages, can be controlled by fish farmers.

Flow Around the Free Bottom of Fish Cages in a Uniform Flow With and Without Fouling

2009 ◽  
Author(s):  
Lars C. Gansel ◽  
Thomas A. McClimans ◽  
Dag Myrhaug
Keyword(s):  
Reynolds Number ◽  
Fish Farming ◽  
Distribution Patterns ◽  
Reynolds Numbers ◽  
Uniform Flow ◽  
Metal Mesh ◽  
Commercial Fish ◽  
Clean Fish ◽  
Fish Cages ◽  
Net Cages

This paper explores the flow around fish cages in a uniform flow with the focus on the flow patterns close to the bottom of the models. Towing tests were conducted with six straight cylinders with the prosities 0%, 30%, 75%, 82% and 90%, two cylinders with an inclination of 12.5 degrees and the porosities 0% and 75% and two cylinders with an inclination of 25 degrees and the porosities 0% and 75%. The models all had a height-to-diameter ratio of 3 and were made from metal mesh. The Reynolds number was 5000 based on the diameter of the models and from 15 to 300 based on the diameter of individual strings of the mesh for all tests. Particle Image Velocimetry (PIV), a non-intrusive optical technique, was used to analyze the flow around the models in the plane of symmetry through the center of the cylinders. The porosities of 82%, 75% and 60% correspond to those of a clean fish cage netting in Norwegian Salmon farming with no fouling, light fouling and heavy fouling, respectively. The inclinations of 12.5 degrees and 25 degrees reflect the inclination of the net of a commercial fish cage in a slow and a fast current, respectively. The Reynolds number of the strings was within the range of Reynolds numbers occurring on fish cages along the Norwegian coast. The results from this study are discussed with respect to the flow around and through the same models at identical Reynolds numbers. It is shown that the inclination of the net cage and fouling of the netting have major effects on the flow pattern around fish cage. The flow around and through net cages defines the water exchange within fish cages and the distribution patterns of particles and nutrients released from a net-pen. The information provided in this study can be valuable for the fish farming industry, as the decrease of the porosity due to fouling, as well as the deformation of the netting of fish cages, can be controlled by fish farmers.

The Effects of Fish Cages on Ambient Currents

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Lars C. Gansel ◽  
Thomas A. McClimans ◽  
Dag Myrhaug
Keyword(s):  
Drag Force ◽  
Particle Image ◽  
Reynolds Numbers ◽  
Strain Gauges ◽  
Metal Mesh ◽  
Image Velocimetry ◽  
Flow Through ◽  
Fish Cages ◽  
Ambient Currents ◽  
Wake Characteristics

Experiments were carried out to measure forces on and wake characteristics downstream from fish cages. Cylinders made from metal mesh with porosities of 0%, 30%, 60%, 75%, 82%, and 90% were tested in a towing tank. The drag force was measured with strain gauges, and the flow field downstream from the models was analyzed using particle image velocimetry. The Reynolds numbers ranged from 1000–20,000 based on the model diameter and 15–300 based on the diameter of the strings of the mesh as an independent obstacle. High porosities (here, 82% and 90%) lead to low water blockage and allow a substantial amount of water to flow through the model. The data indicate that the wake characteristics change toward the wake characteristics of a solid cylinder at a porosity just below 75%. The drag force is highly dependent on the porosity for high porosities of a cylinder.

The Effects of Fish Cages on Ambient Currents

2008 ◽  
Author(s):  
Lars C. Gansel ◽  
Thomas A. McClimans ◽  
Dag Myrhaug
Keyword(s):  
Drag Force ◽  
Particle Image ◽  
Reynolds Numbers ◽  
Strain Gauges ◽  
Metal Mesh ◽  
Image Velocimetry ◽  
Flow Through ◽  
Fish Cages ◽  
Ambient Currents ◽  
Wake Characteristics

Experiments were carried out to measure forces on and wake characteristics downstream from fish cages. Cylinders made from metal mesh with porosities of 0%, 30%, 60%, 75%, 82% and 90% were tested in a towing tank. The drag force was measured with strain gauges and the flow field downstream from the models was analysed using particle image velocimetry (PIV). The Reynolds numbers ranged from 1000 to 20000 based on the model diameter and 15 to 300 based on the diameter of the strings of the mesh as an independent obstacle. High porosities (here 82% and 90%) lead to low water blockage and allow a substantial amount of water to flow through the model. The data indicate, that the wake characteristics change towards the wake characteristics of a solid cylinder at a porosity just below 75%. The drag force is highly dependent on the porosity for high porosities of a cylinder.

Towards the Understanding of Manifold Fluttering During Pendulous Installation: Flow Induced Rotation of Flat Plates in Uniform Flow

2010 ◽  
Author(s):  
Antonio Carlos Fernandes ◽  
Sina Mirzaei Sefat ◽  
Fabio Moreira Coelho ◽  
Mario Ribeiro
Keyword(s):  
Flat Plate ◽  
Rio De Janeiro ◽  
Center Of Pressure ◽  
Numerical Models ◽  
Free Fall ◽  
Reynolds Numbers ◽  
Uniform Flow ◽  
Experimental Results ◽  
Flat Plates ◽  
Drag And Lift

The pendulous installation method of a manifold has a first phase that can be considered as a free fall in water. Of course, this is not free due to the fluid action. The consequence is that the manifold may oscillate rotationally which characterizes a fluttering behavior. However, the manifold is a complex body with non-uniform shape, several modules, porosity etc. Hence, in order to improve the understanding of the fluttering, this work presents advances in the observation of flow induced rotation on a flat plate in uniform flow. This has been started experimentally and subsequently numerical models yielded a confirmation of quasi-steady observations. The experimental results were obtained at the Laborato´rio de Ondas e Correntes (LOC) [Laboratory of Waves and Current] in COPPE/Federal University of Rio de Janeiro. The drag and lift forces coefficients and the center of pressure have been obtained for angles of attack θ = 0°–90° and for different Reynolds numbers.

The Salmon Sea Fish Farming Industry in Iceland: A Review

2019 ◽  
Vol 10 (4) ◽  
Author(s):  
Arnar Bjarnason ◽  
Soffia Karen Magnúsdóttir
Keyword(s):  
Fish Farming ◽  
Farming Industry ◽  
Sea Fish

The Effect of Four Part Gap Geometry Configurations for Variable Stator Vanes in a Compressor Cascade

2012 ◽  
Author(s):  
Marcel Gottschall ◽  
Konrad Vogeler ◽  
Ronald Mailach
Keyword(s):  
Flow Field ◽  
Separated Flow ◽  
Reynolds Numbers ◽  
Compressor Cascade ◽  
Field Development ◽  
Operating Range ◽  
Rear Part ◽  
Axis Position ◽  
Stagger Angle ◽  
Variable Stator

The article describes numerical investigations on the influence of four different endwall clearance topologies for variable stator vanes to secondary flow field development and the performance of high pressure compressors. The aim of this work is to quantify the characteristics of different clearance configurations depending on the penny-axis position and the penny diameter for a typical operating range. All clearance configurations were implemented to a linear cascade of modern stator profiles. The analysis was introduced using a relative clearance size of 1.3% chord at three stagger angles and two characteristic Reynolds numbers to model the operating range on aircraft engines. 3D numerical calculations were carried out to gain information about the flow field inside the cascade. They were compared with measurements of a 5-hole-probe as well as pressure tappings on the airfoil and the endwall. The CFD shows the clearance characteristics in good agreement with the measurements for the lower and the nominal stagger angle. Small gaps in the rear part of the vane have a beneficial effect on the flow field. In contrast, a clearance in the higher loaded front part of the vane always resulted in increased losses. Otherwise, the significant enhanced performance of a rear part gap, which was measured at the higher stagger angle, was not reflected by the CFD. The reduced mixing losses and the higher averaged flow turning even compared to a configuration without a clearance are not verified with the calculations. Large flow separations at the high stagger angle result in a two to four times higher underturning of the CFD in comparison to the experiments. The clearance effects to the characteristic radial loss distribution up to 40 % bladeheight also deviate from the measurements due to heavy mixing of clearance and reversed separated flow.

scholarly journals The drag-adjoint field of a circular cylinder wake at Reynolds numbers 20, 100 and 500

2013 ◽  
Vol 730 ◽  
pp. 145-161 ◽  
Author(s):  
Qiqi Wang ◽  
Jun-Hui Gao
Keyword(s):  
Circular Cylinder ◽  
Flow Field ◽  
Unsteady Flow ◽  
Numerical Solutions ◽  
Reynolds Numbers ◽  
Adjoint Equations ◽  
Cylinder Wake ◽  
Near Wake ◽  
Navier Stokes Equation ◽  
D 20

AbstractThis paper analyses the adjoint solution of the Navier–Stokes equation. We focus on flow across a circular cylinder at three Reynolds numbers, ${\mathit{Re}}_{D} = 20, 100$ and $500$. The quantity of interest in the adjoint formulation is the drag on the cylinder. We use classical fluid mechanics approaches to analyse the adjoint solution, which is a vector field similar to a flow field. Production and dissipation of kinetic energy of the adjoint field is discussed. We also derive the evolution of circulation of the adjoint field along a closed material contour. These analytical results are used to explain three numerical solutions of the adjoint equations presented in this paper. The adjoint solution at ${\mathit{Re}}_{D} = 20$, a viscous steady state flow, exhibits a downstream suction and an upstream jet, the opposite of the expected behaviour of a flow field. The adjoint solution at ${\mathit{Re}}_{D} = 100$, a periodic two-dimensional unsteady flow, exhibits periodic, bean-shaped circulation in the near-wake region. The adjoint solution at ${\mathit{Re}}_{D} = 500$, a turbulent three-dimensional unsteady flow, has complex dynamics created by the shear layer in the near wake. The magnitude of the adjoint solution increases exponentially at the rate of the first Lyapunov exponent. These numerical results correlate well with the theoretical analysis presented in this paper.

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