Ship with propeller, comprising an air duct

Abstract

The invention relates to a ship (10) comprising a hull (110, 115) and at least one motorised propulsion means which rotates at least one propeller (180), the ship comprising at least one air duct (145, 150) comprising at least two openings including an air intake opening (140) positioned above the waterline (190) of the ship and an air outlet opening (160, 161) positioned below the waterline of the ship and configured to direct the air flow under the hull so as to reduce the friction of the hull on the water during navigation, the respective positions of each air outlet and of each propeller on the hull being selected so that the air flow(s) directed under the hull of the ship are axially offset with respect to each propeller so as not to hinder the operation of the propellers.

Description

DESCRIPTION Title of the invention: PROPELLER-POWERED VESSEL WITH AN AIR DUCT TECHNICAL FIELD OF THE INVENTION

[0001] The present invention falls within the field of the design of hulls for propeller-driven ships.

[0002] The present invention relates more particularly to a propeller-driven ship hull equipped with at least one air duct directing an airflow from the front of the ship to under the hull of the ship and configured to minimize or prevent interference with the operation of at least one propeller by the airflow. STATE OF THE ART

[0003] Prior art describes vessels with a hull equipped with a means of forcing an airflow beneath the hull to create an air cushion that aids the vessel's gliding through the water. Such a vessel is described in U.S. patent number 3,662,700. This patent describes a hull with an air duct configured to collect an airflow through an air inlet positioned at the bow of the vessel, above the waterline at least when the vessel is in motion, and an air outlet directing the airflow onto the underside of the hull. The section of the hull receiving the airflow has an inverted V-shaped duct, the apex of which is a centrally located point beneath the hull.

[0004] The present invention aims to provide a significant improvement to the hulls of ships having an air duct of the type described above and which are propelled by the rotation of one or more propellers. OBJECTS OF THE INVENTION

[0005] The vessel that is the subject of the invention is not of the type having water wings or "foils" allowing the vessel to plane, that is to say, to lift its hull out of the water and to navigate in flight with only its foils in contact with the water. Indeed, this type of vessel does not face the technical problem of disruption to the operation of the propeller by an airflow circulating under the hull, channeled between the hull and the surface of the water flowing under the vessel.

[0006] The present invention relates to a vessel equipped with at least one engine rotating one or more propellers which are the main means of propulsion of the vessel and of which the greater part of the hull remains in contact with the water during navigation, under normal navigation conditions.

[0007] During tests on boat hulls featuring one or more air ducts, also called wind ducts, directing an airflow under the hull, the inventor discovered that the design of these vessels was not optimal. Indeed, on vessels known from the prior art, the airflow circulates along the underside of the hull, usually on a central longitudinal axis, and then escapes primarily through the stern of the boat at the propeller. The inventor observed that the continuous airflow escaping from the stern disrupts the operation of one or more propellers providing propulsion. The main objective of the present invention is to remedy this problem.

[0008] Accordingly to a first aspect, the invention relates to a vessel comprising a hull and at least one motor propulsion means rotating at least one propeller, the vessel comprising at least one air duct having at least two openings, including an air intake opening positioned above the waterline of the vessel and an air outlet opening positioned below the waterline of the vessel and configured to direct the airflow under the hull, so as to reduce the friction of the hull on the water during navigation, wherein the respective positions of each air outlet and each propeller on the hull are chosen so that the airflow(s) directed under the hull of the vessel are axially offset with respect to each propeller, so as not to interfere with their operation.

[0009] In other words, the ship is configured so that the airflow(s) generated by the at least one air duct do not overlap with the ship's propeller(s).

[0010] In other words, the respective positions of each air outlet and each propeller on the hull are chosen so that the airflow(s) directed under the hull of the ship are offset laterally relative to each propeller, so as not to interfere with their operation.

[0011] A vessel according to the invention is equipped with an air duct that generates an airflow directed from the bow of the vessel to the stern of the vessel. This airflow circulates along the lower surface of the hull, for example along a substantially A straight line corresponding to the longitudinal axis of the ship. In another example, the airflow can be channeled and directed by the shape of the hull or by means of air ducting. The airflow generated during the ship's movement can be defined as the airflow circulating under the hull at the ship's cruising speed, moving forward in a straight line, on calm seas, under normal ship operating conditions.

[0012] According to the invention, the airflow(s) directed under the hull of the vessel are axially offset from each propeller so as not to interfere with their operation. This means that the propeller(s) are positioned outside the airflow generated by at least one air duct. For example, the vessel is configured to generate two airflows circulating on either side of a centrally located propeller at the stern. In another example, the vessel is configured to generate an airflow circulating along a central longitudinal axis and has two propellers arranged on either side of the flow at the stern. It is noted that the number of airflows circulating under the hull and the number of propellers may vary from one vessel to another without deviating from the invention.

[0013] In other words, the vessel comprises a hull and at least one air duct configured to generate an airflow, the hull structure and the positioning of the at least one air duct forming a first hull surface configured to be exposed to the airflow generated by the air duct and a second hull surface configured to be less exposed to the airflow generated by the air duct than the first surface, the vessel being powered by one or more propellers mounted on the hull at the level of the second surface.

[0014] The first surface configured to be exposed to the airflow is preferably configured to direct most of the airflow along the hull towards the rear of the boat, in order to achieve a cushioning effect. Preferably, the vessel is configured so that the second surface is minimally or not at all exposed to the airflow generated by at least one air duct.

[0015] It should be noted that the first surface may not be a contiguous surface but rather formed by several distinct surfaces, distributed in several places under the hull of the ship. Similarly, the second surface is not necessarily a contiguous surface.

[0016] In this application, the ship's waterline is used as the horizontal reference line, that is, the line separating the submerged part of the ship's hull from the part above water. The determination of this line under standard load conditions and in calm seas is well known. of the trade. The waterline appears in particular on the hull lines plan of each ship under the designation 10H.

[0017] In some embodiments, the hull comprises a bow section and a stern section, the hull bottom of the bow section being lower relative to the waterline of the ship than at least part of the hull bottom of the stern section, and the air outlet of at least one duct is positioned to direct the airflow towards the stern section of the ship.

[0018] Thanks to these features, bubbles form under the hull during navigation. This effect, which occurs independently of the airflow generated by the air-to-air duct, is enhanced by the use of an air duct. These characteristics combine to further reduce friction on the ship's hull, thereby increasing the ship's speed and / or reducing its fuel consumption.

[0019] In some embodiments, the transition between the bow section and the stern section forms a shoulder and at least one air outlet is positioned at the level of said shoulder.

[0020] According to these provisions, the transition between the bow section and the stern section forms a "stair step" or "step." In other words, the ship's hull exhibits a sudden change in dimensions between the bow and stern sections.

[0021] Thanks to these arrangements, the duct can be positioned in the bow section of the hull and the air outlet can be located at the shoulder, so as to produce a flow of air propelled towards the stern section in an orientation close to horizontal.

[0022] In some embodiments, the ship includes air channeling means configured to direct the airflow under the hull.

[0023] Thanks to these arrangements, the airflow circulating under the hull can be deflected, directed or channeled along a predefined path, in particular to prevent the airflow(s) from interacting with at least one propeller.

[0024] In some embodiments, the air channeling means include at least one recess formed under the hull and the air outlet of at least one air duct is positioned to direct the airflow towards said recess.

[0025] In some embodiments, the means for channeling the airflow include at least one protrusion formed in the body of the shell and placed in the path of the airflow.

[0026] Thanks to these arrangements, the means of channeling air are formed directly in the structure of the hull.

[0027] In some embodiments, the means for channeling the airflow include at least one added element fixed to the bottom of the hull.

[0028] Thanks to these provisions, at least some of the air ducting systems can be added to the ship after its construction. These provisions are particularly useful in the case of a ship modernization process, transforming a ship into a vessel according to the invention, which will be detailed below.

[0029] In some embodiments, the means for channeling the airflow comprise at least two walls projecting from the bottom of the hull, placed longitudinally on either side of the air outlet of at least one air duct.

[0030] In some embodiments, the cross-sectional area of ​​at least one air duct is greater at the air intake opening than at the air outlet.

[0031] Preferably, the cross-sectional area of ​​at least one air duct gradually decreases between the air intake opening and the air outlet.

[0032] Thanks to these arrangements, the pressure of the propelled air at the air outlet of at least one pipe is greater than the air pressure at the outlet of a pipe of constant cross-section.

[0033] In some embodiments, at least one air duct comprises a first air duct section connecting the air intake opening to a second air duct section, said second air duct section leading to the air outlet and the second air duct section is positioned below the waterline of the ship so as to be flooded when the ship is at rest.

[0034] Thanks to these arrangements, when the ship is stationary, the second part of the air duct is flooded. The inventor observed that this feature reduces the ship's pitch, yaw, and roll when the ship is immobilized, for example, at anchor.

[0035] Preferably, the first section of the air duct has an oblique inclination relative to the ship's waterline. For example, the first section of the air duct has an inclination between 60 degrees and 30 degrees relative to the ship's waterline.

[0036] Preferably, the second air duct section is horizontal or slightly inclined relative to the ship's waterline. For example, the second air duct section has an inclination between 30 degrees and 0 degrees relative to the ship's waterline.

[0037] In some embodiments, the vessel is a ship selected from among a container ship, an oil tanker, an LNG carrier, or a large fishing vessel. In other embodiments, the vessel is smaller, for example, a pleasure craft such as a yacht or a medium- or small-tonnage fishing boat.

[0038] In some embodiments, the vessel has one or more propellers driven by a shaft rotated by an engine housed in the vessel's holds. In other embodiments, the vessel is equipped with an outboard motor.

[0039] According to a second aspect, the invention relates to a method for modernizing a ship which includes: - a stage of supplying a vessel comprising a hull and at least one means of motor propulsion rotating at least one propeller, - an installation step of at least one air duct having at least two openings, including an air intake opening positioned above the waterline of the ship and an air outlet opening positioned below the waterline of the ship and configured to direct the airflow under the hull, so as to reduce hull friction on the water during navigation, in which the respective positions of each air outlet and each propeller on the hull are chosen so that the airflow(s) directed under the hull of the ship are axially offset relative to each propeller, so as not to interfere with their operation.

[0040] The modernization process, more commonly known as "retrofitting," aims to modify an existing vessel by equipping it with at least one air intake system, thereby creating a vessel according to the invention. These modifications are advantageous because they improve the performance of an existing vessel by applying the technical features of the invention.

[0041] In some embodiments, the modernization process includes a step of installing a cover over part of the keel of the ship's hull, preferably over a section of the hull at the bow of the ship, said cover at least partially sheltering the air duct.

[0042] In some embodiments, the modernization process includes a step of installing at least one means of air ducting, configured to direct the airflow under the hull.

[0043] The modernization process is particularly applicable to large tonnage vessels, for example container ships. BRIEF DESCRIPTION OF THE FIGURES

[0044] Other advantages, purposes and special features of the invention will become apparent from the following non-limiting description of at least one particular embodiment of the vessel and modernization method covered by the present invention, with reference to the accompanying drawings, in which:

[0045] [Fig 1] schematically represents, in side view, a first particular embodiment of a vessel that is the subject of the invention

[0046] [Fig 2] represents, schematically and in rear view, the first embodiment of the ship.

[0047] [Fig 3] represents, schematically and in longitudinal section view, a second particular embodiment of a ship that is the subject of the invention.

[0048] [Fig 4] schematically represents, in three-quarter view, the rear part and the underside of the hull of a ship according to the second embodiment of the invention.

[0049] [Fig 5] represents, schematically and in three-quarter view, the rear part and the underside of the hull of a ship according to a third particular embodiment of the invention.

[0050] [Fig 6] represents, schematically and in three-quarter view, the rear part and the underside of the hull of a ship according to a fourth particular embodiment of the invention.

[0051] [Fig 7] represents, schematically and in three-quarter view, the rear part and the underside of the hull of a ship according to a fifth particular embodiment of the invention.

[0052] [Fig 8] represents, schematically, in the form of a flowchart, the steps of a particular embodiment of a ship modernization process, the subject of the invention.

[0053] The reference numbers mentioned in the figures refer to: 10, 20, 30, 40, 50 Ship 110, 210, 310 Hull bow section 112, 212, 312 Shoulder [“step”) 115, 215, 315 stern section of the hull 418, 518 Shell 231, 232, 233, 234, 335, 430, 431, 432, 433, 434, 435, 530, 531, 532, 533, 534, 535 Recess 140, 240, 340 Air intake opening 145, 245, 246, 345 First part of the air duct 150, 250, 251, 350, 450, 451, 550, 551 Second part of the air duct 160, 161, 260, 261, 360, 460, 461, 462, 463, 464, 465, 560, 561, 562, 563, 564, 565 Air outlet opening 171, 172, 173, 174 Wall (means of air channeling) 180, 280, 380, 381, 180, 580 Propeller 190, 290, 590 Ship's waterline

[0054] The steps in process 1000 are numbered with 4-digit references: 1005, 1010, 1015 and 1020. DETAILED DESCRIPTION OF THE INVENTION

[0055] The present description is given by way of non-limiting attribution, each feature of an embodiment being able to be advantageously combined with any other feature of any other embodiment.

[0056] Figures 1 and 2 illustrate a first specific embodiment of a vessel 10, the subject of the invention. Vessel 10 is a large tonnage container ship with a flat keel. The waterline 190 of vessel 10 is represented by a horizontal line.

[0057] Vessel 10 is distinguished by its two symmetrical air ducts, one on the port side and the other on the starboard side. The first air duct, 145 and 150, is shown in Figure 1. This air duct has an air intake opening 140 positioned at the bow of the vessel and above the waterline 190, and an air outlet opening 160 positioned below the vessel. Only the air outlet opening 161 of the second air duct is visible in Figure 2.

[0058] When the ship 10 is moving forward, air rushes into the air intake openings of the ducts, travels through the air ducts and is then projected from the air outlet openings, 160 and 161, towards the lower surface of the hull, 110 and 115. Since the bottom of the ship 10 is substantially flat, the airflow projected onto the bottom of the hull travels mainly longitudinally along the hull, from the bow to the stern.

[0059] It is specified at this stage that the perimeter of the air duct section gradually decreases between the air intake opening 140 and the air outlet 160. These arrangements allow the air pressure to increase at the air outlet 160.

[0060] Vessel 10 has a propeller 180 positioned centrally at the stern. Advantageously, the air outlets, 160 and 161, of the air ducts are offset from the central axis occupied by the propeller 180. As illustrated in Figure 2, the outlets of the air ducts 160 and 161 are positioned respectively in the center of the port half of Vessel 10 and in the center of the starboard half of Vessel 10. The positions of each air outlet, 160 and 161, and of the propeller on the hull are chosen so that the airflows directed under the hull of Vessel 10 are axially offset from the propeller, so as not to interfere with its operation. At the same time, the projected airflows from the air outlets 160 and 161 form an air cushion capable of reducing water friction on the hull, 110 and 115, during navigation.

[0061] Figure 1 further shows that the visible air duct comprises a first section 145 and a second section 150. The first section 145 has an air intake opening 140 at one end, and its other end is connected to one end of the second section 150. The second section 150 is connected at one end to the first section 145 and at the other end to the air outlet opening 160.

[0062] Advantageously, the second 150 section of the pipe is positioned below the ship's waterline, so that it is flooded when the ship is at rest. These arrangements help stabilize the ship by reducing pitch and roll.

[0063] Preferably, the first part 145 of the air duct has an oblique inclination relative to the waterline 190 of the ship 10. For example, the first part of the air duct has an inclination between 60 degrees and 30 degrees relative to the waterline 190 of the ship 10.

[0064] Preferably, the second part 150 of the air duct is horizontal or slightly inclined relative to the waterline 190 of the ship 10. For example, the second part 145 of the air duct has an inclination between 30 degrees and 0 degrees relative to the waterline of the ship.

[0065] Figures 1 and 2 further show that the hull of vessel 10 comprises two hull sections with distinct shapes at the bottom. The hull of vessel 10 has a bow section 110 and a stern section 115. hull bottom of the bow section 110 descends lower below the waterline 190 ship 10 than the hull bottom of the stern section 115.

[0066] In embodiments, which will be detailed below, the additional hull thickness of the bow section 110 was added to the vessel 10 after its construction, by a modernization or "retrofit" process. The additional thickness in this case corresponds to an over-hull, that is to say, a covering extending over part of the existing hull.

[0067] Advantageously, the second part 150 of the air duct is positioned in the bottom of the hull, on the rear part of the bow section.

[0068] The junction between the bow section 145 and the stern section 150 forms a shoulder 112 on the hull of the ship 10. It is noted that the air outlets, 160 and 161 of the ducts are positioned at the level of the shoulder 112. This positioning combined with the substantially horizontal orientation of the second part 150 of the air duct allows the airflow to be propelled substantially horizontally and very close to the lower surface of the hull, all along the stern section 115 of the hull.

[0069] Vessel 10 incorporates air channeling means configured to direct the airflow circulating under the hull. These air channeling means prevent the airflows propelled by the air duct outlets 160 and 161 from impacting the propeller 180. These means also help to better maintain the airflow under the hull by reducing the proportion of airflow that escapes on either side of the hull.

[0070] The air channeling means comprise, on the lower surface of the stern section 115, a plurality of walls, 171, 172, 173, and 174, projecting under the hull. Walls 171, 172, 173, and 174 are arranged longitudinally over most of the stern section 115 of the hull of the vessel 10. The air outlet 160 produces an airflow directed substantially longitudinally along the hull, and two walls, 171 and 172, are arranged on either side of the air outlet 160 so as to channel the airflow propelled from this outlet. Similarly, walls 173 and 174 are placed on either side of the air outlet 161 and channel the airflow exiting it during the navigation of the vessel 10.

[0071] The walls 171, 172, 173, and 174 are preferably formed from the same material as the hull, for example, they are steel parts. In some embodiments, the walls 171, 172, 173, and 174 are integral parts of the hull sections 10 to which they are attached. In other embodiments In practice, these are added parts attached to the hull, for example by welding, bolting or riveting.

[0072] Figures 3 and 4 show two views of a particular embodiment of a vessel 20, the subject of the invention. Vessel 20 is a light motor vessel. The material forming the hull of vessel 20 comprises, for example, polyester resin as a matrix and reinforcement made of fiberglass or carbon fiber.

[0073] The waterline 290 of the ship is represented by a horizontal line, in figure 3. The ship 20 has a forward hull section 210 and a stern hull section 215. The forward section 210 has a part which descends lower below the waterline than the stern section 215, so that a shoulder 212 is formed between the two sections.

[0074] Vessel 20 has two air ducts arranged symmetrically on the port and starboard halves of the vessel. The air duct on the port half has an air intake opening 240 leading to a first section of duct 245 which runs along the bottom of the hull to a second section of duct 250 substantially parallel to the waterline. Finally, a second section of duct 250 connects the first section of duct to an air outlet opening 260. The air duct on the starboard side of the vessel has the same mirrored structure and terminates at the air outlet 261.

[0075] Air outlets 260 and 261 emerge at shoulder 212. From each of these outlets emerges an airflow when the ship 20 moves forward at sufficient speed.

[0076] The vessel 280 has an internal or outboard type engine which rotates a propeller whose position is schematically represented in figure 4 by propeller 280. It should be noted that the respective placement of the air outlets, 260 and 261, prevents the airflow from being directed directly onto propeller 280. Indeed, propeller 280 is centrally positioned at the stern of the vessel 20 and the air outlets are positioned away from, offset from the central longitudinal axis of the vessel 20, on either side of the hull.

[0077] To better direct the airflow projected from the air outlets 260 and 261 and to prevent this airflow from interacting with the propeller 280, the vessel 20 incorporates air channeling means. These means include recesses 231, 232, 233, and 234, which act as guides to channel the airflow along the stern section 215 of the hull. These recesses also serve to reduce or prevent the escape of airflow from the sides of the vessel 20.

[0078] Figure 5 shows a third particular embodiment of a vessel 30, the subject of the invention. Vessel 30 is a small pleasure craft. It differs from vessel 20 described in Figures 3 and 4 in that it has two propellers, 380 and 381, positioned eccentrically at the stern of vessel 30, on either side of the hull. Vessel 30 is also distinguished by a single air duct 345, shown in dashed lines at the bow of vessel 30, which directs an airflow towards an air outlet 360 centrally located on the hull.

[0079] The vessel 30 has a recess 335 also arranged around a central longitudinal axis of the hull of the vessel 30. The recess 335 is a means of channeling the airflow, configured to direct the airflow substantially in a straight line towards the stern of the vessel 30, preventing the airflow from interacting with the propellers 380 and 381 and preventing or limiting an airflow towards the sides of the vessel 30.

[0080] As with the vessel 20 previously described opposite Figures 3 and 4, the hull of the vessel 30 comprises a bow section 310 and a stern section 315. The hull bottom of the stern section is lower below the waterline of the vessel than the hull bottom of the bow section, so a shoulder 312 is present between the two sections. The air outlet 360 is positioned at the level of this shoulder 312.

[0081] Figure 6 shows a fourth particular embodiment of a vessel 40, the subject of the invention. Vessel 40 is a large tonnage container ship. It differs from vessel 10 described in Figures 1 and 2 in that it has a continuous hull 418, unlike vessel 10 which has a step separating a stern hull section from a bow hull section.

[0082] Vessel 40 has two air tunnels, 450 and 451, each comprising a second section, connected to an opening at the bow of Vessel 40 via a first air tunnel section (not shown). The first air tunnel section is, for example, similar to that described in Figures 1 and 2. Each of the two air tunnels of Vessel 40 opens into three openings, 460, 461, 462, 463, 464, and 465, configured to propel an airflow along the hull 418 to produce an air lubrication effect. It should be noted that the openings, 460, 461, 462, 463, 464, and 465, are arranged on either side of a central longitudinal axis of the hull of Vessel 40.

[0083] The vessel 40 has several recesses 430, 431, 432, 433, 434 and 435, each recess being a means of channeling the airflow, configured to direct the airflow substantially in a straight line from an opening, respectively 460, 461, 462, 463, 464 and 465, towards the stern of the vessel 40, avoiding the airflow interacting with the propeller 480 of the vessel 40 and preventing or limiting an airflow towards the sides of the vessel 40.

[0084] Figure 7 shows a fifth particular embodiment of a vessel 50, the subject of the invention. Vessel 50 is a small pleasure craft; the waterline 590 of vessel 50 is represented by a horizontal line. It differs from vessel 20 described with reference to Figures 3 and 4 in that it has a continuous hull 518, unlike vessel 20, which has a step separating a stern hull section from a bow hull section.

[0085] Vessel 50 has two air tunnels similar to those described for Vessel 20. The second part, 550 and 551, of said tunnels visible in figure 7 is connected to one or more openings [not shown] located at the bow of Vessel 50, by way of a first part [not shown] of air tunnel.

[0086] Vessel 50 differs from Vessel 20 in that each air tunnel, 550 and 551, opens onto three openings, 560, 561, 562, 563, 564 and 565. Vessel 50 has several recesses 530, 531, 532, 533, 534 and 535, each recess being a means of channeling the airflow, configured to direct the airflow substantially in a straight line from an opening, respectively 560, 561, 562, 563, 564 and 565, towards the stern of Vessel 50, preventing the airflow from interacting with the propeller 580 of Vessel 50 and preventing or limiting an airflow towards the sides of Vessel 50.

[0087] Figure 7 shows an illustration in the form of a flowchart of a 1000 process for modernizing a ship.

[0088] Process 1000 includes a step 1005 of supplying a vessel comprising a hull and at least one motor propulsion means rotating at least one propeller. For example, the vessel is a flat-keeled container ship. In this case, implementing process 1000 results in a vessel of the type of vessel 10 described with reference to Figures 1 and 2.

[0089] The process 1000 includes a step 1010 of installing at least one air duct having at least two openings, including an air intake opening positioned above the waterline of the ship and an air outlet opening positioned below the waterline of the ship and configured to direct the Airflow under the hull is designed to reduce hull friction on the water during navigation. The respective positions of each air outlet and each propeller on the hull are chosen so that the airflow(s) directed under the hull of the vessel are axially offset from each propeller, thus avoiding interference with their operation.

[0090] In some embodiments, the process 1000 includes a step 1015 of installing a cover, or over-hull, covering a part of the keel of the ship's hull, preferably on a section of the hull at the bow of the ship, said cover at least partially sheltering the air duct.

[0091] In some embodiments, the process 1000 includes a step 1020 of installing at least one means of channeling air, configured to direct the airflow under the shell.

Claims

DEMANDS

1. Vessel [10, 20, 30, 40, 50) comprising a hull [110, 210, 310, 115, 215, 315, 418, 518) and at least one motor propulsion means rotating at least one propeller [180, 280, 380, 381, 480, 580), the vessel comprising at least one air duct [145, 245, 246, 345, 150, 250) comprising at least two openings including an air intake opening [140, 240) positioned above the waterline [190, 290) of the vessel and an air outlet opening [160, 161, 260, 261, 360, 460, 461, 462, 463, 464, 465, 560, 561, 562, 563, 564, 565) positioned below the ship's waterline and configured to direct airflow under the hull,in order to reduce hull friction on the water during navigation, the vessel is characterized in that the respective positions of each air outlet and each propeller on the hull are chosen so that the airflow(s) directed under the hull of the vessel are axially offset with respect to each propeller, so as not to hinder their operation.

2. Vessel [10, 20, 30) according to claim 1, wherein the hull comprises a bow section [110, 210, 310) and a stern section [115, 215, 315), the hull bottom of the bow section being lower relative to the waterline [190, 290) of the vessel than the hull bottom of the stern section, and wherein the air outlet of at least one duct is positioned to direct the airflow towards the stern section of the vessel.

3. Vessel [10, 20, 30) according to claim 2, wherein the transition between the bow section and the stern section is formed by a shoulder [112, 212, 312) on the hull of the vessel and wherein at least one air outlet is positioned at the level of said shoulder.

4. Vessel [10, 20, 30, 40, 50) according to any one of claims 1 to 3, which includes air channeling means configured to direct the airflow under the hull.

5. Vessel [10, 20, 30, 40, 50] according to claim 4, wherein the air channeling means comprise at least one recess [231, 232, 233, 234, 335, 430, 431, 432, 433, 434, 435, 530, 531, 532, 533, 534, 535] formed under the hull and wherein the air outlet of the unless an air duct is positioned to direct the airflow towards said recess.

6. Vessel according to any one of claims 4 or 5, wherein the means for channeling the airflow comprise at least one protrusion formed in the hull body and placed in the path of the airflow.

7. Vessel [10] according to any one of claims 4 to 6, wherein the means for channeling the airflow comprise at least one added element fixed to the bottom of the hull.

8. Vessel [10] according to any one of claims 4 to 7, wherein the means for channeling the airflow comprise at least two walls projecting from the bottom of the hull and placed longitudinally on either side of the air outlet of at least one air duct.

9. Vessel [10, 20, 30, 40, 50) according to any one of claims 1 to 8, wherein at least one air duct comprises a first part [145, 245, 246, 345) of air duct connecting the air intake opening to a second part [150, 250, 350, 450, 550) of air duct, said second part of air duct leading to the air outlet and wherein the second part of air duct is positioned below the waterline of the vessel so as to be flooded when the vessel is at rest.

10. A method [1000] for modernizing a ship characterized in that it comprises: - a step [1005] of supplying a vessel comprising a hull and at least one motor propulsion means rotating at least one propeller, a step [1010] of installing at least one air duct comprising at least two openings, including an air intake opening positioned above the waterline of the vessel and an air outlet opening positioned below the waterline of the vessel and configured to direct the airflow under the hull so as to reduce hull friction on the water during navigation, wherein the respective positions of each air outlet and each propeller on the hull are chosen so that the airflow(s) directed under the hull of the ship are offset axially with respect to each propeller, so as not to interfere with their operation.

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