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| Registros recuperados: 37 | |
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| Khaled, Ramez; Priour, Daniel; Billard, Jean-yves. |
| A numerical method for optimization of the cable lengths in trawls with respect to the ratio between the estimated trawl drag and the predicted catch efficiency is developed and applied. The trawl cables of interest are warps, bridles, headline and footrope. The optimization algorithm applies an ordered sequential process changing one cable length at the time. It is assumed in the predictions that the catch efficiency of the trawl is proportional with the trawl mouth area. In a case study optimizing a bottom trawl used on a research vessel by applying the new method it is predicted that it would be possible to reduce the ratio between trawl drag and catch efficiency by up to 46% by optimizing the cable lengths. Thus this would enable a considerable... |
| Tipo: Text |
Palavras-chave: Bottom trawl; Modeling; Optimization; Fuel consumption; Drag; Swept area; Mouth surface; Fish distribution. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00130/24106/22857.pdf |
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| Priour, Daniel. |
| Codends are the rear parts of trawls, which collect the catch and where most of the selectivity process occurs. Selectivity is the process by which the large sh are retained while the small ones are released. The codends applied in many sheries often consist of only one type of mesh. Therefore it is reason- able to consider these codends as being axisymmetric. Their shapes depend mainly on the volume of catch, on the shape of meshes (diamond, square, hexagonal) and on the number of meshes along and around the codend. The shape of the codends is of prime importance in order to understand the se- lectivity process. This paper presents a model of deformation of codends made up of hexagonal meshes. Two types of hexagonal meshes have been investigated: the T0... |
| Tipo: Text |
Palavras-chave: Codends; Hexagonal meshes; Trawl selectivity; Simulation; Twine tensions; Catch force. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00215/32597/31061.pdf |
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| Morvan, Barthelemy; Bles, G; Dumergue, Nicolas; Priour, Daniel. |
| The evaluation of the mesh opening stiffness of fishing nets is an important issue in assessing the selectivity of trawls. It appeared that a larger bending rigidity of twines decreases the mesh opening and could reduce the escapement of fish. Nevertheless, netting structure is complex. A netting is made up of braided twines made of polyethylene or polyamide. These twines are tied with non-symmetrical knots. Thus, these assemblies develop contact-friction interactions. Moreover, the netting can be subject to large deformation. In this study, we investigate the responses of netting samples to different types of solicitations. Samples are loaded and unloaded with creep and relaxation stages, with different boundary conditions. Then, two models have been... |
| Tipo: Text |
Palavras-chave: Numerical model; Experiments; Braided twine; Mesh opening rigidity; Large deformation.. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00348/45899/45581.pdf |
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| Priour, Daniel; Khaled, Ramez. |
| Trawls energy efficiency is greatly affected by the drag, as well as by the swept area. The drag results in an increase of the energy consumption and the sweeping influences the catch. Methods of optimisation of the trawl design have been developed in order to reduce the volume of carburant per kg of caught fish and consequently the drag per swept area of the trawl. Based on a finite element method model for flexible netting structures, the tool modifies step by step a reference design. For each step the best-modified design, in terms of drag per swept area is kept. Such optimisation can lead to a decrease of the drag or an increase of the swept area. In the second case, that could lead to an increase of fishing effort. To avoid such increase, which could... |
| Tipo: Text |
Palavras-chave: Fishing; Fuel; Fishing gear; Trawl; Optimisation; Fishing effort. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/00170/28151/26381.pdf |
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| Morvan, Barthelemy; Priour, Daniel; Guede, Zakoua; Bles, G.. |
| The evaluation of the mesh resistance to opening of fishing nets is an important issue in assessing the selectivity of trawls by numerical methods. Sala et al. (2007) proposed a method using a relatively expensive experimental device ensuring the 2D deformation of net sample. De la Prada and Gonzales (2015) proposed a simple uni-axial experimental set-up, which stretches a sample in the transverse direction of the meshes while leaving free its deformation in the normal direction. Both authors (Sala and De la Prada) assumed that the deformation is uniform in the sample. The present study aims at developing a finite element model taking into account the mesh resistance to opening of nets, allowing the simulation of non-uniform deformation. Mechanical... |
| Tipo: Text |
Palavras-chave: Netting; Mesh resistance to opening; Bending stiffness; Experiment; Numerical model. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00347/45813/49043.pdf |
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| Herrmann, Bent; Priour, Daniel; Krag, Ludvig A.. |
| FEMNET, a numerical tool based on the finite element method, was used to estimate the shapes of four different designs of trawl cod-ends during fishing operations. Compared to a traditional diamond-mesh cod-end the design differences were the following: (i) the netting orientation was turned by 90 degrees (T90), (ii) the number of meshes in the circumference was reduced by 50% or (i) and (ii) were combined. The cod-end shape estimates were then entered into the simulation tool PRESEMO, to estimate their influence on the selectivity processes in the cod-end. This enabled us to predict how these design alterations - alone or combined - may act on the selectivity of each cod-end under identical fishing conditions. For instance, we predict that for a I 10 mm... |
| Tipo: Text |
Palavras-chave: FEMNET; PRESEMO; T90; Cod end selectivity. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2588.pdf |
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| Herrmann, B; Priour, Daniel; Krag, L. |
| FEMNET, a numerical tool based on the finite element method, was applied to estimate the shapes of various diamond-mesh cod-end designs during fishing. The only design differences rest in the use of round straps of different lengths, positions and numbers. The cod-end shape estimates were then entered in the selectivity simulation tool PRESEMO to simulate the selectivity processes of the various cod-end designs under the same varying fishing conditions. This enabled us to demonstrate how one or two round straps along the cod-end axis may change the selectivity of the cod-end compared with a reference cod-end, without round straps. We predict that in cod-end designs, which comply with the EU legislation, the 50% retention length (L50) may be reduced by up... |
| Tipo: Text |
Palavras-chave: Catch weight; FEMNET; PRESEMO; Round straps; Cod end selectivity. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-1870.pdf |
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| Priour, Daniel. |
| Trawls energy efficiency is greatly affected by the drag, as well as by the swept area regarding pelagic trawls and by the swept width for bottom ones. The drag results in an increase of the energy consumption and the sweeping influences the catch. In order to reduce the drag per swept area (or width) a numerical tool dedicated to the automatic optimisation of the trawl design has been developed. Based on a finite element method model for flexible netting structures, the tool modifies step by step a reference design. For each step the best-modified design, in terms of drag per swept area (or width), is kept. Such a methodology was used in two cases: which show a 43% increase in energy efficiency regarding the pelagic trawl case and 27% for the bottom trawl... |
| Tipo: Text |
Palavras-chave: Swept width; Swept area; Drag; Fuel consumption; Optimisation; Modelling; Trawl; Fishing gears. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2009/publication-6583.pdf |
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| Germain, Gregory; Druault, Philippe; Lewandowski, Roger; Benoit, Vincent; Priour, Daniel; Billard, Jean-yves. |
| The project presented here and named HydroPêche aims to develop a tool for an Automatic optimisation of trawl in order to minimize the drag of the gear. For that purpose, different aspects are studied in order : a/ to extend the basis of experimental data on flow characteristics governing the hydrodynamic behaviour of different porous structures ; b/ to develop numerical tools to simulate more realistic flow around porous structures taking into account fluid / structure interactions; c/ to develop automatic optimisation tools to design efficient trawls in terms of energy consumption. The developed tool should provide a substantial gain on the fuel consumed of actual fishing devices while maintaining a comparable fishing efficiency. The developments made... |
| Tipo: Text |
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| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00021/13266/10313.pdf |
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| Tancray, Aurelien; Ohana, Jeremy; Priour, Daniel. |
| Ces essais se déroulent dans le cadre de la thèse du Dr LODDE sur l’impact d’une plongée sur le corps humain. Suite à un protocole bien défini, des médecins feront divers analyses sur les plongeurs avant et après immersion. 16 plongeurs ont été reçus sur 2 jours : 8 palanquées de 2. Chaque plongeur passe par des examens médicaux avant plongées : EFR, laser doppler, tension, prise de sang. Après une plongée de 40 minutes à 20m, le plongeur recommence les examens. Les médecins seront ainsi en mesure, sur un échantillon de plongeurs désignés (age, sexe, poids, taille différents), de déterminer l’influence d’une immersion sur le corps humain. |
| Tipo: Text |
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| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00343/45457/45006.pdf |
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| Sala, Antonello; Priour, Daniel; Herrmann, Bent. |
| The objective of this study was to investigate the effect on Mullus barbatus (red mullet) codend selectivity by increasing the codend mesh size or reducing the number of meshes in the codend circumference. This was performed through experimental sea trials and computer simulations. The sea trials were carried out in the Adriatic Sea using a polyamide codend in order to assess its selectivity, to record morphological (height, width and length) and population size structure parameters of red mullet (Mullus barbatus). The selectivity process in the codend was also simulated with an individual-based model (PRESEMO) and a finite element model (FEMNET) to calculate the codend shapes. By adjusting the behavioural description of red mullet in the simulation, the... |
| Tipo: Text |
Palavras-chave: Mediterranean Sea; Mullus barbatus; Red mullet; Codend shape simulation model; Trawl; Codend selectivity. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-2200.pdf |
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| Priour, Daniel; De La Prada, Amelia. |
| Measurements at sea during fishing trials on bottom trawl have revealed that the geometry of the trawl is affected by the catch. A series of 37 hauls of around 3 h were carried out during the French EFFICHALUT project. The aim of this project was to carry out improvements on the fishing gear in order to reduce energy consumption. For this project, numerous sensors were used: for bridle tension, door spread, vertical opening, and door attitude. The measurements show quite clearly that the door spread decreases and the bridle tension increases during most of the hauls. The door spread decreased by 1.35 m/h, with a standard deviation of 1.98 m/h while the top bridle tension increased by 47 kg/h, with a standard deviation of 59 kg/h. The mean catch per haul... |
| Tipo: Text |
Palavras-chave: Trawl; Data; Modeling; Door spread; Bridle tension; Catch weight. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00239/34990/33525.pdf |
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| De La Prada, Amelia; Priour, Daniel. |
| Thirty-seven hauls of a bottom trawl were carried out, as part of a national French project. These sea trials were undertaken in an area with strong currents: up to 1 knot. The measurements at sea of the bottom bridle’s tension show a clear effect of the current. Although the water speed relative to the trawl is constant, when the boat tows with current, the bottom bridle’s tension increases, and when the boat tows against the current, the bottom bridle’s tension decreases. The mean bottom bridle tension is 7840 N and increases with a slope of 1197 N for each m/s of current. The current has almost no effect on the top bridle’s tension: for a mean value of approximately 9810 N, the increment is 106 N for each m/s of current. The modelling of the trawl gear... |
| Tipo: Text |
Palavras-chave: Trawl; Data; Numerical model; Bridle tension; Bottom boundary layer; Water speed. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00266/37710/35800.pdf |
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| Registros recuperados: 37 | |
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