Load Coefficients and Dimensions of Raschel Knitted Netting Materials in Fish Farms

2021 ◽  
Author(s):  
Heidi Moe Føre ◽  
Per Christian Endresen ◽  
Hans V. Bjelland
Keyword(s):  
Reynolds Number ◽  
Structural Design ◽  
Mathematical Expression ◽  
Fish Farming ◽  
Local Velocity ◽  
Fish Farms ◽  
Drag Coefficients ◽  
Velocity Reduction ◽  
Study Results ◽  
New Knowledge

Abstract New types of fish farms are often larger and structurally more complex than conventional fish farming structures, and associated challenges concerning safety and costs increase correspondingly. Thus, increased precision in structural design is required, with estimation of hydrodynamic loads on nets as an important topic. Today, both load coefficients for nets and measured netting dimensions are given with relatively high uncertainties. New knowledge for netting materials with high solidities as well as scaled netting commonly applied in model tests are included in the presented study. Results from towing tests and the development of a new mathematical expression for local drag coefficients (for netting twines) indicate that drag coefficients are not only dependent on solidity and Reynolds number, but may also be affected by the velocity reduction and the local velocity at the twines.

scholarly journals Normal and Tangential Drag Forces of Nylon Nets, Clean and with Fouling, in Fish Farming. An Experimental Study

Water ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 2238
Author(s):  
Yarko Niño ◽  
Kevin Vidal ◽  
Aldo Tamburrino ◽  
Luis Zamorano ◽  
Juan Felipe Beltrán ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Drag Force ◽  
Fish Farming ◽  
Operating Conditions ◽  
Relevant Parameter ◽  
Sea Lion ◽  
Drag Coefficients ◽  
Average Value ◽  
Drag Forces

Experiments in a laboratory tank have provided measurements of the normal and tangential drag forces exerted on flat nets for different flow conditions. From those forces, normal and tangential drag coefficients of the nets have been obtained as functions of the Reynolds number and the solidity index. The experiments used two types of nets employed in the operation of a cultivation center: the fish net and the sea lion net, for the clean situation and for real operating conditions, with fouling adhered to the nets. Polyethylene ropes were used to characterize the presence of fouling in the nets. The experiments were carried out to determine equations for the normal and tangential drag coefficients. For the normal drag coefficient, the equations are linear with the Reynolds number, and the coefficients of the equations are linear with the solidity index. The equations are not so accurate for the tangential drag coefficient. The Reynolds number is not a relevant parameter for this coefficient and neither is the solidity index for the fish net, but the coefficient grows slightly with it for single and double sea lion nets with fouling. The literature review on the drag forces of nets reports that the tangential drag force is around 30% of the normal drag force. This value is approximately an average value of the ratio for the sea lion net and is higher for the clean fish net in this article.

Fish farming in Denmark: environmental impact of regulative legislation

1995 ◽  
Vol 31 (10) ◽  
pp. 73-84 ◽  
Author(s):  
T. M. Iversen
Keyword(s):  
Organic Matter ◽  
Environmental Impact ◽  
Freshwater Fish ◽  
Aquatic Environment ◽  
Action Plan ◽  
Fish Farming ◽  
Fish Farms ◽  
Nitrogen And Phosphorus ◽  
Local Impact ◽  
The Impact

The main environmental problems associated with fish farming in Denmark are attributable to the dam, the “dead reach” and nutrient and organic matter discharge. The environmental regulation of fish farming in Denmark started with the Environmental Protection Act of 1974, the Statutory Order of 1985 forbidding wet feed, and the Action Plan on the Aquatic Environment of 1987. In the case of freshwater fish farms, the latter was implemented through the measures stipulated in the 1989 Statutory Order on Fish Farms. The impact of Danish legislative measures to reduce and regulate the environmental effects of freshwater fish farms can be summarized as follows: - the number of fish farms has been reduced from about 800 in 1974 to about 500 at present; - production has tripled since 1974 and has been stable since 1989; - a change from wet to dry feed has reduced the environmental impact of the farms; - the national goals of the Action Plan on the Aquatic Environment of 1987 for reducing fish farm discharges of organic matter, nitrogen and phosphorus have been fulfilled. The main remaining problems are that: - the local impact of fish farms on downstream stream quality is still much too high in about 15% of cases; - the problem of the passage of migrating invertebrates and fish is still unsolved at some farms; - the problems posed by “dead reaches” are still unsolved. It is concluded that sustainable fish farming is possible in Denmark, but with the present technology production will have to be significantly reduced.

Environmental impact of nutrients from nordic fish farming

1995 ◽  
Vol 31 (10) ◽  
pp. 61-71 ◽  
Author(s):  
M. Enell
Keyword(s):  
Major Part ◽  
Fish Farming ◽  
Fish Farms ◽  
Feed Composition ◽  
The North ◽  
Comprehensive Development ◽  
The Baltic ◽  
Inland Water Bodies ◽  
The Impact ◽  
Feed Coefficient

During the last 20 years there has been an interesting development of the Nordic fish farming, with regard to the feeding and farming technology and to the increase in production quantities. During the period 1974-1994 the production increased from 15,800 to about 250,000 tonnes/year. In 1974 the major part of the production was in Denmark, and in 1994 the major part was in Norway. The nutrient impact of fish farming on surrounding sea areas is mainly a function of the feed coefficient, the feed composition and metabolic processes in the fish. The comprehensive development of the feed composition and the feeding technology has resulted in reduced load of unmetabolized nutrients from fish farms, calculated per tonne fish produced. In 1974 the mean Nordic feed coefficient was 2.08 and in 1994 the coefficient was 1.25. Feed coefficients of 1.0-1.1 are now reported for Danish and Norwegian freshwater and marine fish farms. The nitrogen (N) and phosphorus (P) content of the feed has decreased, in addition the quality of the nutrient substances in the feed has changed, especially for N. The N content has decreased from 7.8 to 6.8% during the period 1974-1994 and the content of P has decreased from 1.7 to 0.7% during the same period. This development of the feed coefficient and the feed composition has resulted in a present load from a typical Nordic fish farm of 55 kg N and 4.8 kg P/t fish produced. The figures for 1974 were 132 kg N and 31 kg P/t fish produced. The Nordic fish farming production in 1994 resulted in a load of about 13,750 t N and about 1,200 t P on the actual recipients. The load from the Swedish, Finnish and Danish fish farming operations, with the Baltic Sea and the Skagerrak as the recipients, is negligible in comparison with other pollution sources. The quantities of N and P from the fish farming are equal to 0.5% of the atmospheric deposition on the sea surface and 3% of the atmospheric P load. Norwegian, Icelandic and the Faroe Islands fish farming operations are using the North Sea and the Norwegian Sea as the recipients. However, the nutrient load from single fish farms in certain coastal and inland water bodies can be significant and must be considered in the impact assessment together with other sources.

Growing commodity tilapia in various experimental conditions

2020 ◽  
pp. 26-36
Author(s):  
F. A. Altayeva
Keyword(s):  
Fish Farming ◽  
Biological Indicators ◽  
Fish Farms ◽  
Experimental Conditions ◽  
Fish Breeding ◽  
Closed Water ◽  
The Republic ◽  
Short Time ◽  
High Fish ◽  
Experimental Ponds

The article presents the results of growing tilapia to marketable weight in experimental sites (Chilikskoye pond pond farms LLP, KATU named after S. Seifullin JSC and Kapshagai spawning farm — 1973 LLP). In the process of carrying out research works, the methods generally accepted in fish farming, hydrochemistry, hydrobiology, hydrology, ichthyology, as well as foreign normative and technical guidelines and methodological instructions on the technology of growing commercial tilapia in industrial conditions were used. Monitoring of hydrochemical analyses of water in ponds, swimming pools, and closed water supply installations is given. Fish-breeding and biological indicators of tilapia grown in various experimental conditions are presented. The results of the studies have shown the real possibility of growing tilapia in various conditions of fish farms in Kazakhstan. Based on the results of the work, the following conclusions were made: — satisfactory fish-breeding indicators were obtained with various cultivation technologies (as when growing tilapia in polyculture and monoculture in ponds, in pools, as well as cultivation in the recirculation system); — the cultivation of tilapia in the experimental ponds of the fish farm of the Almaty region of the Republic of Kazakhstan has shown the possibility of obtaining high fish-breeding biological indicators of tilapia and the ability to grow to marketable mass in a short time; — as a result of experimental cultivation in various conditions, it was found that the survival rate was not lower than 97%; — as a result of the analysis of the profitability indices of the developed technologies, it was found that the most profitable was the technology of growing marketable tilapia products in monoculture ponds on water with a natural thermal regime in Chilik Pond Economy LLP.

PREVENTIVE MEASURES IN BREEDING FISHING FARMS: ECOLOGICAL AND VETERINARY ADDITIONS

2018 ◽  
Vol 1 (1) ◽  
pp. 84-89
Author(s):  
A. M. Naumova ◽  
◽  
L. A. Rozumnaya ◽  
A. Yu. Naumova ◽  
L. S. Loginov ◽  
...  
Keyword(s):  
Preventive Measures ◽  
Fish Farming ◽  
Fish Health ◽  
Fish Farms ◽  
Scientific Publications ◽  
Commercial Fish ◽  
Fish Products ◽  
Contagious Diseases ◽  
Veterinary Research ◽  
Significant Damage

The influence of ecological, epizootological and technological factors on fish health was studied. It is shown that disregard of environmental, technological and veterinary-sanitary requirements in the reproduction and cultivation of fish leads to the emergence of contagious and non-contagious diseases and causes significant damage to fish farming. The analysis of previously approved veterinary and sanitary rules, instructions, recommendations for breeding and commercial fish farms, as well as patent documentation and scientific publications in the field of ecological and veterinary research in fish farming is carried out. The possibility of using modern ecological and veterinary-sanitary achievements for the protection of fish health is shown. The complex system of preventive measures (organizational, environmental-technological and veterinary-sanitary), supplemented by modern ecological and veterinary achievements, in its implementation will allow to reduce losses of fish products and increase efficiency of production.

A Computational Study on Airfoils at a Low Reynolds Number

2000 ◽  
Author(s):  
Ajit Pal Singh ◽  
S. H. Winoto ◽  
D. A. Shah ◽  
K. G. Lim ◽  
Robert E. K. Goh
Keyword(s):  
Reynolds Number ◽  
Computational Analysis ◽  
Computational Study ◽  
Low Reynolds Number ◽  
Micro Air Vehicles ◽  
Reynolds Numbers ◽  
Aerodynamic Performance ◽  
Low Reynolds Numbers ◽  
Study Results ◽  
Low Reynolds

Abstract Performance characteristics of some low Reynolds number airfoils for the use in micro air vehicles (MAVs) are computationally studied using XFOIL at a Reynolds number of 80,000. XFOIL, which is based on linear-vorticity stream function panel method coupled with a viscous integral formulation, is used for the analysis. In the first part of the study, results obtained from the XFOIL have been compared with available experimental data at low Reynolds numbers. XFOIL is then used to study relative aerodynamic performance of nine different airfoils. The computational analysis has shown that the S1223 airfoil has a relatively better performance than other airfoils considered for the analysis.

scholarly journals Economics of ornamental fish farming industry in Madurai District, Tamil Nadu

2017 ◽  
Vol 64 ◽  
Author(s):  
T. Umamaheswari ◽  
M. Rajakumar ◽  
P. Chidambaram
Keyword(s):  
Tamil Nadu ◽  
Sampling Technique ◽  
Fish Farming ◽  
Ornamental Fish ◽  
Expected Profit ◽  
Profit Margin ◽  
Fish Farms ◽  
The Cost ◽  
Farming Industry ◽  
Ranking Technique

India has enormous potential for the development of ornamental fish business. Although the country has conducive environmental conditions for breeding and culture of ornamental fishes, its share in export of ornamental fishes is less than 1%. The present study was undertaken to address the constraints prevailing in ornamental fish farming. Study was carried out among 44 ornamental fish farms in Madurai District, Tamil Nadu by adopting random sampling technique. The selected farms were classified into small (<0.5 ha) and medium farms (0.5-2 ha) and the data were collected by personally interviewing the fish farmers. The study attempted to analyse the socio-economic characteristics of respondents, existing supply chain, constraints involved in ornamental fish farming, annual revenue loss due to major constraints, treatment cost and expected profit margin. Various constraints were classified as production, marketing and others and were ranked using Garrett ranking technique. Tabular and percentage analyses were used to estimate the cost of treatment, revenue loss and expected profit margin. Four types of marketing channels were observed in the study area. Disease outbreak was found to be the major constraint faced by the farmers and hence, the revenue loss was estimated for the same. The annual revenue loss was found to be higher for the small ornamental units when compared to medium farms, which showed higher profit margin than small ornamental fish farms.

scholarly journals Knowledge in (Trans)Training and the Role of Experts: Curricula, Mathematics Education and Teacher Training, 1920-2020

2020 ◽  
Vol 22 (5) ◽  
pp. 65-83
Author(s):  
Wagner Rodrigues Valente ◽  
André Francisco de Almeida ◽  
Marylúcia Cavalcante Silva
Keyword(s):  
Elementary Schools ◽  
Teacher Training ◽  
Main Question ◽  
Study Results ◽  
New Knowledge ◽  
In Trans ◽  
Teaching Programs ◽  
Changes Over Time ◽  
Over Time

Background: Mathematics for basic and elementary schools and teacher education changes over time; and their official expression is given by these documents that guide teaching work in schools. Objective: What processes and dynamics are involved in the systematisation of new knowledge in the production of curriculum references? In particular, the text focuses on mathematics for the first school years. Design: The analysis of curricular reforms, considering official documents, prioritises the role of specialists, treated as experts, considering that following the actions of these researchers it may be possible to answer the main question of the study. Results: Analysis shows that the changes that have occurred over time, from teaching programs to the current BNCC, are linked to the progressive stratification of experts who go from being a highly visible public authority to an increasing set of representatives from different social segments interested in the curricular debate. Conclusions: This stratification makes it more difficult to locate those specialists responsible for the internal organisation of the proposals with regard to teaching objects, the content of mathematics to be present in teaching and teacher training.

scholarly journals Numerical simulation and experimental research of cavitation nozzle based on equation curve

2021 ◽  
Author(s):  
Lifu Wang ◽  
Dongyan Shi ◽  
Zhixun Yang ◽  
Guangliang Li ◽  
Chunlong Ma ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Flow Field ◽  
High Speed ◽  
Quadratic Equation ◽  
Outer Contour ◽  
Study Results ◽  
Fluent Software ◽  
The Impact ◽  
Better Than

Abstract To further investigate and improve the cleaning ability of the cavitation nozzle, this paper proposes a new model that is based on the Helmholtz nozzle and with the quadratic equation curve as the outer contour of the cavitation chamber. First, the numerical simulation of the flow field in the nozzle chamber was conducted using FLUENT software to analyze and compare the impact of the curve parameters and Reynolds number on the cleaning effect. Next, the flow field was captured by a high-speed camera in order to study the cavitation cycle and evolution process. Then, experiments were performed to compare the cleaning effect of the new nozzle with that of the Helmholtz nozzle. The study results demonstrate that effective cavitation does not occur when the diameter of the cavitation chamber is too large. For the new nozzle, with the increase of the Reynolds number, the degree of cavitation in the chamber first increases and then decreases; the cleaning effect is much better than that of a traditional Helmholtz nozzle under the same conditions; the nozzle has the best cleaning effect for the stand-off distance of 300 mm.

Water Quality of Lake Iskanderkul and Its Tributaries

2020 ◽  
Vol 6 (2) ◽  
pp. 79-88
Author(s):  
Z.O. Normakhmedova ◽  
◽  
A.V. Mitusov
Keyword(s):  
Water Pollution ◽  
Water Quality ◽  
Chemical Composition ◽  
Fish Farming ◽  
Natural Phenomena ◽  
Change Dynamics ◽  
Chemical Composition Of Water ◽  
Study Results ◽  
Copper Zinc

This article presents the study results of the change dynamics in the chemical composition of water in Lake Iskanderkul and the rivers flowing into it, as well as the comparison of water quality in the water bodies of the Iskanderkul Basin and several mid-stream tributaries of the Zarafshan River. It was established that the chemical composition of water in Lake Iskanderkul and its tributaries meets the requirements of the corresponding state standard (GOST 2874-82 “Drinking Water”). However, in terms of dissolved oxygen, copper, zinc, lead and iron the water in Lake Iskanderkul does not satisfy fish farming requirements. The main water pollution sources in the area include such natural phenomena as floods, avalanches, mudslides, and rock dissolution.

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