FR3151178A1 - SUBMERGED INSTALLATION FOR FISH FARMING COMPRISING A FLEXIBLE ENVELOPE - Google Patents

Abstract

Submerged installation (1) for fish farming, comprising an outer casing (2) made of a flexible material, said casing (2) having a general shape of revolution around a vertical axis V, said casing extending from an upper region (5) connected to a section ensuring the flotation of the installation, and a lower region (7) where it is connected to a lower rigid device (9) ensuring in particular the collection of solid materials flowing towards the bottom of the installation, the casing (2) having a region of maximum radius (Rmax) measured in a horizontal plane, characterized in that over a portion of height (13) extending from the region of maximum radius of the casing to the lower region, the profile of the casing (2), taken in a vertical plane passing through said vertical axis V is inscribed in a zone delimited by: - a first straight line (20, 30, 40, 50), vertical, passing through the point P1 of maximum radius of the casing ,- a second straight line (21, 31, 41, 51), tangent to the profile of the envelope at the connection point P2 of the envelope and the lower rigid device (9), the first and second straight lines intersecting at a point C (25, 35, 45, 55),- a circular arc (23, 33) passing through the point of maximum radius of the envelope P1, and through the connection point P2 of the envelope with the lower rigid device (9), said circular arc being tangent to the first or second straight line respectively at the point P1 of maximum radius of the envelope or the connection point P2 which is furthest from point C, and in that the profile has at each point of its height, a unit curvature determined as the curvature multiplied by the value of the maximum radius (Rmax) which varies according to the position of the point, measured by the unit length of the profile at said point relative to the length of the profile, the value of the derivative of the function giving the unit curvature relative to said unit length being less than 15. Figure for abstract: Fig 3

Description

SUBMERGED INSTALLATION FOR FISH FARMING COMPRISING A FLEXIBLE ENVELOPE

The present invention relates to an aquaculture farming device of the closed or semi-closed cage type, usable for example for fish farming in a marine, river or lake environment.

This type of device makes it possible to create a closed breeding area, preferably large and for example with a capacity of several tens of thousands of cubic meters, which can be directly installed in the natural aquatic environment, while remaining isolated from it. It makes it possible to grow algae or raise aquatic animals, such as fish, crustaceans or molluscs, until they reach a marketable size.

State of the art

Generally speaking, fish farming facilities are mainly of two types.

A first type of so-called "open" installations also called "Open Net Pens" include an envelope confining the fish made from very openwork materials, such as nets, as described in document EP 0 824 310. Such an installation has the advantage that the water is renewed by the natural flow and in particular sea currents, as well as the elimination by gravity of waste that passes through the envelope. However, these cages have the disadvantage of only being accepted for fish larger than the mesh of the net, of not protecting these same fish from substances or parasites present around the installation. In addition, they induce strong environmental interactions due to the discharge into the environment of parasite treatment products, livestock effluents, etc.

The other type of facilities called "closed or semi-closed" are designed to delimit a volume within which the fish can grow, while confining them so that they can be collected when the growth cycle is complete. This volume must be as watertight as possible, to protect the growing fish from predators and parasites present in the water in which the facility is immersed. Elements that promote the growth of the fish are also provided in this volume, whether it is their food, or food supplements or other substances with a veterinary effect. Since this volume isolates the environment in which the fish evolve, it is advisable to ensure that the water it contains is renewed and that solid waste generated by breeding is eliminated, generally by extraction in the lower part of the facility.

Different solutions have generally been proposed for enclosures in which fish to be raised are confined.

Thus, solutions have been proposed that use a rigid enclosure as illustrated in document WO 2019/035719. While such a structure has the advantage of being relatively resistant to water movements, it has many drawbacks related to its rigid nature. These include a difficulty related to its transport after assembly, or a significant manufacturing cost, combined with the complexity of declining such a structure in various dimensions. This is why there is also another type of installation, made from a flexible material, which forms an envelope delimiting the volume isolating the fish from the environment in which the installation is immersed.

This is why we note the rise of solutions in which the envelope confining the fish is made from a relatively waterproof material, typically formed by a film, or a coated textile. This envelope is generally made to adopt a shape favorable to breeding on several levels.

This type of installation therefore includes a flexible envelope associated with different components intended to ensure on the one hand buoyancy and on the other hand the overall maintenance of the shape of the envelope, to withstand the different environmental conditions (currents, waves, and pressure differences, etc.) to which the envelope is subjected. Thus, for reasons of distribution of the pressure supported by the envelope, it generally has a shape of revolution.

Furthermore, in order to collect the waste generated by fish, which is heavier than water, it is common to install equipment at the bottom of the installation to collect this waste, with a view to its removal and treatment. This collection of waste is therefore advantageously carried out at a single point, so that it is advantageous for the flexible envelope to have a shape whose section in a horizontal plane decreases as the depth increases. A conical shape, with the tip pointing downwards, is therefore particularly suitable for this function. In practice, the angle of the cone is generally determined to ensure good flow of waste by gravity, and to prevent it from accumulating on the internal surface of the envelope. Such a shape is illustrated in particular in document US 4,744,331.

Document CA 3 400 215 describes an alternative in which the envelope has a generally spherical shape. This shape nevertheless has the disadvantage of having an insufficient slope near its lowest zone, with therefore risks of sedimentation of waste.

To provide sufficient volume inside the envelope, it is produced by combining both the volume of conical geometry in the lower part, with generally a volume of cylindrical shape located in the upper part. Examples of such embodiments are in particular described in documents WO 2021/201691, US 4,798,168, US 8,770,149.

The Applicant noted that the slope breaks forming angles at the junctions between the cylindrical portion and the conical portion were the source of mechanical stresses within the membrane forming the envelope, which could be detrimental to its durability over time.

A more sophisticated form has been proposed in document US 6,443,100 which describes a fish cage whose shape is cylindrical in the upper part, conical in the lower part, near the waste extraction device, and whose intermediate part between the cylindrical zone and the conical zone is formed by a tangent rounded transition (or fillet) forming a toric sector, avoiding the presence of an angle with the aforementioned drawbacks.

The Applicant nevertheless noted that such installations had the disadvantage of exposing the membrane to significant mechanical stresses at the junctions between the different cylindrical, rounded and conical sectors. Indeed, in a vertical plane, the cylindrical and conical parts have an infinite radius of curvature, or zero curvature, whereas in the rounded portion, the radius of curvature is fixed and not zero. It therefore appears that the jumps in curvature at the transition between the cylindrical part and the rounded part on the one hand, and the rounded part and the conical part on the other hand, are the source of an increase in the stresses exerted in the fabric, with the corollary increase in the risks of tearing and/or damage or at the very least premature wear.

The invention therefore relates to a submerged installation for fish farming, comprising an outer casing made of a flexible material. This casing extends from an upper region connected to a section ensuring the flotation of the installation, and a lower region where it is connected to a lower rigid device ensuring in particular the collection of solid materials flowing towards the bottom of the installation. This casing has a general shape of revolution around a vertical axis V, and has a region of maximum radius (Rmax) measured in a horizontal plane.

The invention consists in giving the envelope a specific profile, by which the radius of curvature is controlled and continuous, and does not present local variations greater than a predetermined threshold, which would be the source of strong mechanical constraints within the membrane.

In other words, the invention consists in defining the profile of the envelope such that in the area of interest located between the region of the maximum radius and the connection of the waste extraction device, this profile remains circumscribed within a characteristic surface. This surface has two rectilinear sides formed by the vertical at the point of maximum width of the envelope on the one hand, and on the other hand, by the straight line tangent to the envelope at the point of connection to the lower extraction device. The third line which closes this surface is an arc of a circle which passes through the two specific points which are the point of maximum width of the envelope and the point of connection to the lower rigid device intended for the extraction of waste. At one of these two points, this arc of a circle is tangent to the tangent to the envelope. This will be the point of largest diameter of the envelope in the case of a cage of a rather vertically elongated shape, for which the point of intersection of the two characteristic lines is located closer to the connection to the extraction device than to the point of largest diameter. Conversely, in the case of a cage wider than it is high, the circle closing the surface against the profile will then be tangent to the level of the connection of the extraction device. The other end of the arc of the circle simply passes at the level of the other remarkable point.

Controlling the variation of the envelope curvature over this entire area is done quantitatively by normalizing the curvature and length, by determining the unit or dimensionless curvature, by multiplying the curvature at a given point by the maximum radius of the envelope, measured in a horizontal plane. At the same time, the position of the current point is also measured in a standardized way, by reporting the distance of the current from one of the ends of the envelope, and by dividing the latter by the length of the envelope over the entire area.

In practice, the geometry of such a profile can be defined in different ways, giving the profiles predetermined curve shapes.

Thus, on the portion of characteristic heights, the profile of the envelope can correspond to a clothoid curve. It is recalled that a clothoid curve is defined as a curve whose curvilinear abscissa at a given point varies, to within a proportionality factor, with the curvature of the curve at this point. Advantageously, by fixing the point of origin of measurement of the curvilinear abscissa at one end of the profile zone of interest, the curvature at this point is zero, and makes it possible to connect to a portion of zero radius of curvature, that is to say with a rectilinear profile, as for example in a cylindrical or conical region of the envelope.

In practice, the profile can be composed of several sections, each corresponding to a clothoid curve. In other words, the property of the clothoid curve, which has a continuous curvature and can increase from a zero value, can be used to ensure a connection of this portion of the profile to two zones of zero curvature, by associating two clothoid-type sections connected to each other with an identical curvature value.

Other remarkable curves can be used to produce the characteristic profile, for example spline-type curves. It is recalled that a spline curve is a curve that includes a certain number of predetermined points, between which the curve adopts a polynomial profile between each of the points. In the context of the invention, spline curves of order at least two will be chosen, so as to ensure the geometric continuity of order G2 of the curvature between each of the polynomial sections . Thus, in practice, the determination of the desired spline curve can be done by calculation, using the parameter values corresponding to the curvatures to which the characteristic portion is connected.

Other geometries can be adopted by the profile, in the characteristic area, including geometries where the curvature is reversed at one or more points of the characteristic area. Thus, the envelope is essentially convex, i.e. with a curvature oriented towards the inside of the cage. But it is also possible to have a curvature oriented towards the outside in limited areas.

The invention makes it possible to produce multiple fish cage geometries, in particular those which have a cylindrical shape in the upper part. It is in fact thus possible to continue the profile of the envelope downwards while ensuring a progressiveness of the curvature of this profile, by limiting the stresses exerted inside the fabric, due to the absence of curvature jump.

In practice, the envelope can be made from different materials, and in particular from threads, or even preferentially from a material comprising a textile core layer coated with a polymeric material.

This envelope can be made in different ways, including by assembling different spindles that extend in the direction of the height of the installation, these spindles being assembled by their facing areas, by welding in particular. Depending on the size of the cage, it is also possible to assemble the different spindles by mechanical systems such as lacing, a zipper, or even riveting...

Summary description of the figures

The manner of carrying out the invention, as well as the advantages which result therefrom, will emerge clearly from the description of the embodiments which follow, supported by the appended figures in which:

is a summary perspective view of an installation in accordance with the invention.

is a sectional view along a plane of vertical symmetry of the installation of the .

is a detailed schematic view of the profile of the envelope of the installation of the .

is a diagram illustrating the variation of the curvature of the envelope profile of the , shown as a function of the unit length of the profile.

is a similar view of the for a variant of realization.

is a view analogous to the , for another execution variant.

is a view analogous to the for the embodiment of the .

is a similar view of the for another embodiment.

is a similar view of 4 for the embodiment of the ;

In all the figures and in the remainder of the description, the scales and proportions of the various elements that are represented have been shown for information purposes in order to better understand the invention. They may differ from the actual dimensions and proportions. Furthermore, and by convention, the elements are described by considering their orientation in space in a normal use situation, that is to say with gravitational forces that require the axis of revolution of the installation to be vertical.

Detailed description

As illustrated in the , the invention relates to an installation 1 intended for fish farming and more generally for the breeding of aquatic animals. In a very simplified manner, such an installation 1 comprises an envelope 2 defining an internal volume 3 separated from the external environment 4 . This envelope extends from an upper part 5 where it can be associated with means ensuring its buoyancy 6 . In practice, the flotation means can be directly secured to the upper part of the envelope, as illustrated in . But it is also possible to provide that the envelope is connected to the flotation means by means of a rigid portion at the top of which the flotation means are secured. In the lower part 7 , the installation comprises a rigid device, intended to serve as an anchoring point for various mechanisms necessary for the proper functioning of the installation. We can notably cite the function of extracting waste likely to be generated and accumulate inside the installation, but also the renewal of the internal water by generating a circulation of water inside the envelope, but also the anchoring or ballasting of the cage so that it retains a shape appropriate for its proper functioning. These elements not having a direct relationship with the invention, they will not be described in detail, or even mentioned in the figures.

More specifically, as illustrated in the schematically, the envelope 2 extends from its upper part 5 , where it is connected to the flotation means, schematically represented by a circular flange 6 on a cylindrical portion 12 whose limit is located at the point P1 , corresponding to the lowest level where the diameter of the envelope is maximum, measured relative to the axis of revolution V. Below the point P1 , the profile of the envelope follows a curve up to the point P2 where this envelope is connected to the aforementioned rigid device 8. As already mentioned, the invention concerns the definition of the profile of the envelope 2 in the zone which connects its point of maximum diameter P1 to its point P2 of connection to the extraction device 8 .

As illustrated in the , the Applicant has identified a certain number of profiles making it possible to limit the constraints which are exerted within the envelope, in the regions where it presents variations in curvature which are obligatory for the envelope to be able to ensure both a flow of the waste which is produced, with a sufficient overall volume.

More specifically, as illustrated in the , the Applicant has defined an area, defined in the plane of symmetry of the envelope, within which the profile must be fully contained to achieve the desired effect. This area is defined as illustrated by three specific lines:
- a first line 20 is a straight line segment which is vertical, and extends downwards from the point P1 of maximum radius. This straight line is, in the case where the envelope has a cylindrical shape, above the point P1 which is in the continuity of the profile of the envelope above the point P1 ;
- a second line 21 is defined relative to the point P2 of connection of the envelope with the rigid device 8. This line 21 is also a straight line segment which is tangent to the envelope at the point P2 where the envelope connects to the rigid device 8.
- the third line 23 is an arc of a circle which connects the points P1 and P2 in order to close the characteristic zone. In the illustrated form the , this arc of a circle 23 , in addition to passing through points P1 and P2, is tangent to point P2 on line 21 , and therefore to envelope 2 .

This choice is made to take into account the fact that the relevant segment of the line 21 extending from point P2 to point 25 at the intersection with the line 20 has a length greater than the segment of the line 20 separating the same point 25 from point P1 of the start of the characteristic profile portion. Thus, since the profile of the envelope is found in the hatched zone 26 , the Applicant has found that a first condition is met so that the stresses exerted inside the membrane of the envelope are maintained below a maximum threshold.

A second condition for obtaining this effect is that the definition of the curve forms a profile inducing a limitation of the variation of the curvature along the envelope between the highest point P0 and the lowest point P2.

More precisely, this variation in curvature (defined as the inverse of the radius of curvature measured at each point) is assessed by developing a dimensionless variable to make it less dependent on the absolute dimensions of the cage. This dimensionless variable, hereinafter referred to as unit curvatureKu, is obtained by multiplying the measured curvature by the maximum radiusR _max from the envelope to the pointP1. Thus, the unit curvature measured by moving between the pointsP 0 AndP2has an absolute value less than Rmax x Kmax, where Kmax is the maximum value of curvature (in a vertical plane passing through the axis of revolution) measured over the entire height of the envelope. At the same time, in order to evaluate the variation of this unit curvature, it can be plotted on a curve such as illustrated in in which the abscissa represents the unit lengthReadat the point where the curvature is measured. This length is measured as a fraction of the total developed length of the envelope between the pointsP 0 AndP2, so that the corresponding abscissa evolves between 0 and 1.

The Applicant found that limiting the variation of this unit curvature made it possible to limit the level of stresses exerted inside the envelope. To do this, the difference in relative curvature between two points 2% apart in unit length is less than 0.30 of unit curvature. In other words, this criterion corresponds to ensuring that the derivative of the function giving the unit curvature as a function of the unit length remains less than 15. It is noted that the curvature is continuous at point P1, which marks the junction between the upper part of the envelope, cylindrical in shape in the example, and the lower part following the characteristic profile.

In the variant illustrated in the , which is analogous to the , the area 36 of the plane of symmetry in which the profile is to be contained is analogously defined between three lines. Two straight lines 20 , 31 are in the same way as for the defined as being respectively the vertical at the point P1 of maximum diameter, and the tangent to the envelope, at the point P2 of connection of the envelope to the extraction device 8. However, in this example, the point 35 forming the intersection of these two lines is closer to the point P2 than to the point P1 . In this case, the arc of a circle 33 which passes through the two points P1 and P2 is then tangent to the line 30 at the point P1 , and passes through the point P2, without necessarily being tangent to the envelope at the point P2 . This scenario is observed predominantly on envelopes which are more elongated vertically than wide horizontally.

In the variant illustrated in the , the profile of the envelope 44 takes a clothoid shape which starts at the point P1 corresponding to a point of greatest diameter of the envelope. This clothoid curve is such that the curvature increases proportionally to the developed length of the envelope, measured from the point P1 . It follows as illustrated in that the unit curvature Ku increases linearly from a zero value corresponding to the upper cylindrical part of the envelope, between points P0 and P1, to a maximum value of Kmax x Rmax at point P2 .

Of course, forms derived from this clothoid can be used, using clothoids of order N > 1

Furthermore, depending on the curvature existing at point P1 , particularly in the case where the area of the envelope located above point P1 is not cylindrical, it is possible to introduce an offset in the definition of the parameterization of the clothoid curve so that the radius at the zero curvilinear abscissa corresponding to point P1 is not itself zero, but equal to the curvature located above point P1.

This same principle can be applied to the example of the in which the curve which defines the profile of the envelope is made up of two distinct sections of two rather clothoid curves which meet at the point57. More precisely, the first section54is a clothoid curve starting at the pointP1,that is, with zero curvature inP1. Symmetrically, the second section58is also a clothoid curve whose curvature at the pointP2is also zero. The defining coefficients of these two clothoid curves are chosen so that the curvatures at the point57of the two sections54, 58, adopt the same value on both sides of this point, as illustrated in . The position of this point57where the clothoids meet can be adjusted for reasons of volume optimization, efforts or constraints related to the breeding site, by determining the parameters of each clothoid (coefficient of proportionality of the curvature with the curvilinear abscissa, order of the clothoid) appropriate.

It is clear from the above that the design of the casing of the installation according to the invention makes it possible to avoid the curvature jumps observed in the solutions of the prior art, and therefore to limit the mechanical stresses exerted inside the casing, in the vertical plane. Better resistance and an extension of the service life are thus obtained.

Claims (8)

Submerged installation (1) for fish farming, comprising an outer casing (2) made of a flexible material, said casing (2) having a general shape of revolution around a vertical axis V, said casing extending from an upper region (5) connected to a section ensuring the flotation of the installation, and a lower region (7) where it is connected to a lower rigid device (9) ensuring in particular the collection of solid materials flowing towards the bottom of the installation, the casing (2) having a region of maximum radius (R _max ) measured in a horizontal plane, characterized in that
over a height portion (13) extending from the region of maximum radius of the envelope to the lower region, the profile of the envelope (2), taken in a vertical plane passing through said vertical axis V is inscribed in a zone delimited by:
- a first straight line (20, 30, 40, 50), vertical, passing through the point P1 of maximum radius of the envelope,
- a second straight line (21, 31, 41, 51), tangent to the profile of the envelope at the connection point P2 of the envelope and the lower rigid device (9), the first and second straight lines intersecting at a point C (25, 35, 45, 55),
- a circular arc (23, 33) passing through the point of maximum radius of the envelope P1, and through the point P2 of connection of the envelope with the lower rigid device (9), said circular arc being tangent to the first or second straight line respectively at the point P1 of maximum radius of the envelope or the point P2 of connection which is furthest from point C, and in that the profile has at each point of its height, a unit curvature determined as the curvature multiplied by the value of the maximum radius (R _max ) which varies according to the position of the point, measured by the unit length of the profile at said point relative to the length of the profile, the value of the derivative of the function giving the unit curvature relative to said unit length being less than 15. Installation according to claim 1 characterized in that on said height portion, the profile (44) corresponds to a clothoid curve. Installation according to claim 2 characterized in that the profile is composed of several sections (54, 58) each corresponding to a clothoid curve. Installation according to claim 1, characterized in that on said height portion, the profile (24) corresponds to a spline curve. Installation according to claim 1, characterized in that the flexible envelope comprises a height portion having a cylindrical shape (12, 22, 32, 42, 52), located above the region of maximum radius of the envelope. Installation according to claim 1 characterized in that the envelope is made of a material comprising a textile layer coated with a polymeric material. Installation according to claim 6, characterized in that the envelope is composed of spindles (9) extending in the direction of the installation height, said spindles being assembled by their facing zones. Installation according to claim 7, characterized in that the spindles (9) are secured to each other by welding and/or by a mechanical system such as lacing, a zipper, or riveting.