AU2013276738A1

AU2013276738A1 - Structure for an underwater vehicle such as a submarine

Info

Publication number: AU2013276738A1
Application number: AU2013276738A
Authority: AU
Inventors: Christian Audoly; Xavier DAUPLAIS
Original assignee: DCNS SA
Current assignee: Naval Group SA
Priority date: 2012-06-11
Filing date: 2013-06-05
Publication date: 2015-01-15
Anticipated expiration: 2033-06-05
Also published as: PL2858892T3; FR2991661B1; BR112014031077A8; BR112014031077A2; FR2991661A1; CA2875441A1; EP2858892A1; BR112014031077B1; AU2013276738B2; IN2014DN10338A; CA2875441C; WO2013186095A1; EP2858892B1; ES2601160T3; MY168393A

Abstract

The invention relates to a structure for an underwater vehicle, which comprises a thick hull (1) that is, over at least a portion of the length thereof, generally cylindrical, and which is characterized in that the sidewalls of said structure (1) comprise, over at least a portion of the length of the cylinder, an acoustic deflection means (2) comprising, on each side of the thick hull, cladding members (2) having a V-shaped cross-section, which lie flat against the hull (1) and which are combined with said hull via a shock-absorbing and noise-damping means (6).

Description

1 Structure for an underwater vehicle such as a submarine The present invention relates to a structure for an underwater vehicle, such as a submarine strictly speaking. More specifically, the invention relates to a structure for an underwater vehicle that comprises a thick hull that has a generally cylindrical shape over at least part of its length. This structure can also comprise other parts, such as a so-called deadwood part, or a so-called submarine governor device part. Various studies have shown that for these structures, and in particular for submarines, there is a significant threat related to the evolution and proliferation of sonars, for example so-called active sonars. In order to account for this threat, studies have been conducted to reduce the target index, i.e., to increase the acoustic stealth of a submarine, including at very low frequencies. The improved stealth, in particular acoustic stealth, of a submarine can be obtained in two main ways: eliminating the sonar echo returned by the target, for example the submarine, toward the threat, i.e., the enemy active sonar, or cancelling it. Thus, the stealth of a submarine can be improved by inclining the various planar walls of its structure relative to the vertical; the sonar wave emitted by the enemy sonar is then reflected toward highly positive or highly negative sites. In most cases, the threat is in fact on sites comprised within plus or minus 100, i.e., close to the submarine. Furthermore, if the submarine comprises a semitransparent thin hull placed around the thick hull, the sonar wave is weakly transmitted, which makes it possible to mask any echoes returned by the structure and various pieces of equipment placed for example below the thin hull thereof. The stealth may also be improved by using absorbing acoustic coatings on the structure that make it possible to decrease the amplitude of the wave reflected by the thick hull of the submarine considerably. The absorbing acoustic coatings are also called anechoic coatings. The target index of a submarine is generally maximal on the broadside, i.e., for relative bearings at plus or minus 900, due to the echo returned by the cylindrical part of the hull and to a lesser extent, by the deadwood and governor device thereof. As previously indicated, the deadwood and the governor device can be treated using either of the described methods and the cylindrical hull can be treated using an anechoic coating to improve the discretion of the submarine as much as possible. However, significant difficulties arise at low and very low frequencies.

2 In effect, the anechoic coating is either very thick or not very effective. In practice, it is difficult to obtain better than 6 dB below 3 kHz, and anechoism below 1.5 kH is practically impossible. Furthermore, the use of this type of coating also raises a problem related to the installation of large side antennas for passive sonar detection. There is in fact a conflict between this use of large antennas and the installation of an anechoic coating on certain portions of the cylindrical hull. It is for example known that submarine builders have proposed installing side antennas on anechoic coatings. However, this has several drawbacks: - The anechoic coating, even in a thick layer, has a mediocre performance at very low frequencies. Furthermore, the significant compressibility of that coating based on the hydrostatic pressure is detrimental for the balance of naval architecture. - The presence of this type of coating below a side antenna deteriorates the performance thereof at low frequencies. In fact, there is no hard reflector behind the sensors of that antenna, and acoustic interferences appear due to reflections on the hull situated behind the anechoic coating. Other submarine builders have proposed using acoustic appendages in particular added on the cylindrical part of the thick hull of the submarine. However, none of these solutions are fully satisfactory, because it is difficult to simultaneously ensure good acoustic stealth of the submarine by the broadside, allow good integration of large side sonar antennas and protect against side impacts of the thick hull. The aim of the invention is therefore to resolve these problems. To that end, the invention relates to a structure for an underwater vehicle, of the type comprising a thick hull that is, over least part of its length, generally cylindrical, characterized in that the side flanks of that structure comprise, over at least part of the length of the cylinder, an acoustic deflection means comprising, on each side of the thick hull, V-shaped cladding members, which lie flat against the hull and are combined with said hull via shock absorbing and noise-damping means. According to other features of the structure according to the invention, considered alone or in combination: - the cladding members are at least partially metallic; - the cladding members are made from plates of a metal material; - the plates comprise inclined faces; - the plates have a thickness comprised between 8 and 10 mm; - the inclined faces of the plates are inclined by at least 150 relative to the vertical; 3 - the lower face of the V-shaped cladding members comprises side sonar antenna means on its outer surface; and - the lower face of the V-shaped cladding members comprises additional acoustic baffle means on its inner face. The invention will be better understood upon reading the following description, provided solely as an example and done in reference to the appended drawings, in which: - figure 1 shows a partial view of a generally cylindrical thick hull segment of an underwater vehicle according to the invention, on a side of which an acoustic deflector is installed; and - figures 2 and 3 show partial views illustrating alternative embodiments of that deflector. As illustrated in these figures, the invention relates to an underwater vehicle structure, in particular such as a submarine strictly speaking. A submarine generally comprises a thick hull that is generally cylindrical over at least part of its length, that thick hull part being designated by general reference 1 in these figures. According to the invention, the sidewalls of that cylindrical thick hull portion are provided, over at least part of their length, with an acoustic deflection means, one of which is designated by general reference 2 in these figures. Indeed, as illustrated in particular in figures 2 and 3, these acoustic deflector means comprise V-shaped cladding members on each side of the thick hull 1 which lie flat against the thick hull of the submarine and are combined with that hull through shock-absorbing and noise-damping means, one end of which is connected to the cladding member and the other end of which is connected to the hull of the submarine, for example. In these figures, one of the V-shaped cladding members that lie flat against the thick hull is designated by general reference 3 and for example comprises a metal plate with inclined faces on either side of the central ridge thereof, designated by general references 4 and 5. This metal plate for example has a thickness comprised between 8 and 10 mm. The faces of the V-shaped plate that lies flat can be inclined by an angle at least equal to 150 relative to the vertical. As previously indicated, damping means are provided between these cladding members and the rest of the hull. These means are designated by general reference 6 in these figures and for example comprise any traditional damping structure, for example with a bar, telescoping tubes or other means.

4 Several dampers are then distributed for example along the plate, between said plate and the rest of the hull. These dampers 6 thus make it possible to absorb any impacts on the sides of the thick hull, and avoid transmitting vibrations from the hull to the deflectors, which helps reduce the noise radiated by the submarine, and therefore the acoustic discretion of that submarine. Each face of the cladding member can then be formed by a portion of a planar metal material, like that designated by general reference 7 in figure 2. An acoustic coating of the soft material type, i.e., with a low acoustic impedance with a typical thickness of 20 to 30 mm, is for example provided on the inner face thereof. That coating is designated by general reference 8 in figure 2. This configuration then allows a significant reduction in the target index of the submarine on the broadside, even at very low frequencies. A reduction of 10 to 15 dB can for example be achieved at 1.5 kHz. Furthermore and as illustrated in figure 3, it is also possible to use these cladding members, and in particular the lower face 5 of the plate thereof, to install a side sonar antenna designated by general reference 10 in figure 3. This side sonar antenna then points to the negative sites, as shown by this figure. It is known that pointing toward the negative sites is more favorable in terms of signal/noise ratio. The acoustic response of the antenna in the low frequencies can also be improved by using additional baffles, as is also known. In figure 3, the side sonar antenna module is designated by general reference 10 and is therefore installed on the outer surface of the corresponding lower face 5 of the plate forming the deflection member, while the inner face thereof comprises an additional plate, for example made from steel, typically 10 to 20 mm thick, and a layer of soft material typically from 20 to 40 mm thick. This plate and layer assembly then forms an additional baffle designated by general reference 11 in this figure 3, on the inner surface of the corresponding face 5 of the plate. Of course, other embodiments of these cladding members, and in particular of the faces or planar plates making them up, and other damping means, can be considered. Thus for example, the planar parts, i.e., the faces of this deflection structure, can also be made from a composite material in order to allow mass savings, with the exception of sonar antenna receiving areas, in which these faces are necessarily made from a material with a high acoustic impedance, i.e., steel for instance.

5 The shape of the acoustic deflection structure can also come alongside the thick hull in different configurations by connecting, or not connecting, to the deck of the underwater vehicle. Furthermore, the zones situated between the cladding members and the thick hull make it possible to incorporate certain small pieces of equipment outside that hull. Likewise, it is in particular possible to pass electric cables therein, for example for the power supply and to recover signals from the side sonar antennas. Of course, other embodiments can also be considered.

Claims

1.- A structure for an underwater vehicle, of the type comprising a thick hull (1) that is, over at least part of its length, generally cylindrical, characterized in that the side flanks of that structure (1) comprise, over at least part of the length of the cylinder, an acoustic deflection means (2) comprising, on each side of the thick hull, cladding members (2) having a V-shaped section, which lie flat against the hull (1) and are combined with said hull via shock-absorbing and noise-damping means (6).

2.- The structure for an underwater vehicle according to claim 1, characterized in that the cladding members (2) are at least partially metallic.

3.- The structure for an underwater vehicle according to claim 2, characterized in that the cladding members (2) are made from plates (3) of a metal material.

4.- The structure for an underwater vehicle according to claim 3, characterized in that the plates (3) comprise inclined faces (4, 5).

5.- The structure for an underwater vehicle according to claim 4, characterized in that the plates (3) have a thickness comprised between 8 and 10 mm.

6.- The structure for an underwater vehicle according to claim 4, characterized in that the inclined faces (4, 5) of the plates (3) are inclined by at least 150 relative to the vertical.

7.- The structure for an underwater vehicle according to any one of the preceding claims, characterized in that the lower face (5) of the V-shaped cladding members (2) comprises side sonar antenna means (10) on its outer surface.

8.- The structure for an underwater vehicle according to any one of the preceding claims, characterized in that the lower face (5) of the V-shaped cladding members (2) comprises additional acoustic baffle means (11) on its inner face.