Ship hull assembly for reducing water resistance and improving maneuverability

There is provided a hull assembly for reducing water resistance on a ship hull and improving the maneuverability on said ship. The hull assembly is mountable on a pre-existing ship hull having a bow, and a stern. The hull assembly comprises a propeller chamber for enclosing at least one propeller positioned proximate the stern of the ship hull, and a plurality of ducts attachable to an outer surface of the ship hull. The ducts extend in a longitudinal direction from a front part of the bow to the propeller chamber. The ducts have a plurality of bow openings along the bow for the water to flow directly toward the rear part of the stern, each of the ducts comprising at least one stern opening near the propeller chamber. The propeller chamber comprises two opposed chamber sides; at least one chamber opening on each of the two opposed chamber sides; and a rear opening for each of the at least one propeller.

FIELD OF THE INVENTION

The present invention generally relates to a hull assembly, and more particularly to a hull assembly that allows reducing wave making resistance and viscous drag, and improving the maneuverability of the ship.

BACKGROUND

Ship hulls are subjected to water resistance forces that lower ship performance and increase energy consumption. Wave making resistance and viscous drag represent the most important loss of energy during ship motion.

Wave making resistance reflects the energy required to displace the water in front of the ship. This energy is transmitted to the water and creates waves along the ship path. Viscous drag is a frictional force opposed to ship motion. In order to save energy and improve ship performance, a number of solutions for reducing hull resistance forces have been developed. Some of these solutions attempt to use bulbous extensions to marginally reduce wave making resistance. Other solutions attempt to use air bubble injection to reduce viscous drag. Some solutions are based on the use of external propellers on the sides of the hull in order to use front water to propel the ship.

Other solutions consist of flowing water from the front of the ship to the rear part of the ship in order to decrease the water resistance on the ship hull. For example, WO20100037253 discloses a flow conduit that communicates a forward water intake opening with a backward water discharge opening provided at the stern or at the two sides of the hull. A water communicating pipeline can also guide water from the front part of the ship to the rear part of the ship, as described in CN2350310. A screw propeller is therefore positioned at the rear part of the ship in the water communicating pipeline. In CN102285440, the displaced water is propelled through draft tubes at the rear of the ship. In a same manner, in CN101209751, a water inlet is arranged at a bow and a water outlet is arranged at a stern such that a pipeline guides water through the front and back of a ship body. WO1992022456 discloses an external conduct mounted forward of the bow and extending to the aft of the ship. In JP2014522778 a hydrodynamic duct is attached to the bow of a ship. Water flows through the duct, wave making effects and frictional resistance are reduced. In WO1982003055, the vessel has a duct through which water flows from the bow to the stern past the main part of the hull. According to WO1982003055, part of the water flows past the vessel through a duct and is used to assist forward motion of the vessel. However, none of the above mentioned document teaches features that allow for water flow control and water pressure control at different areas of the ship hull. Moreover, these solutions fail to meet the needs of industry because they alter specific aspects of optimum hull design and produce marginal results that sometime do not compensate for the complexity of integrating such solutions in the manufacturing process.

Therefore, there currently exists a need in the industry for a ship design that can eliminate the hydrodynamic resistance of wave making and viscous drag, and improve the maneuverability and sea keeping characteristics of a ship while minimizing the operational cost and the alteration of an optimum hull design.

Furthermore, it would be desirable to have a solution for the aforementioned desirable features that can be retrofitted on existing ships.

SUMMARY

It is therefore a general object of the present invention to provide a hull assembly for reducing water resistance on a ship hull, the ship hull having a bow, and a stern, said hull assembly comprising: a propeller chamber for enclosing at least one propeller, the propeller chamber positioned proximate

the stern of the ship hull, the propeller chamber comprising two opposed chamber sides; at least one chamber opening on each of the two opposed chamber sides; and a rear opening for each of the at least one propeller; and a plurality of ducts attachable to an outer surface of the ship hull, the ducts

extending in a longitudinal direction from a front part of the bow to the propeller chamber, the ducts having a plurality of bow openings along the bow for the water to flow directly toward the propeller chamber, each of the ducts comprising at least one stern opening into the propeller chamber.

In an embodiment, the ducts are transversally distributed from a waterline to a baseline of the hull at the bow, said ducts going downward toward the stern and extending under a bottom of the hull from an end part of the bow to a front part of the stern, said ducts extending toward the propeller chamber at the stern. In another embodiment, a dimension of the bow openings decreases along the longitudinal direction, from the front part of the bow toward the stern and ceases at an end of a curvature of the bow. In yet another embodiment, the dimension of the bow openings decreases along the transversal direction from the waterline down toward the baseline. In a further embodiment, the dimension of the bow openings is proportional to a volume of water expected to be displaced at the position of said bow openings.

In an embodiment, the chamber opening of each of the two opposed chamber sides is closable by a plurality of vertical door assemblies. The door assemblies can have an increasing size toward the rear part of the stern. The door assemblies can further comprise vertical closing louvers and an actuating system for controlling positioning of the closing louvers. In another embodiment, the at least one stern opening of each of the ducts opens into the propeller chamber.

In a further embodiment, the at least one stern opening of each of the ducts further comprises a closing gate, said closing gate being independently closable. In an embodiment, the hull assembly further comprises a steering nozzle attached to the rear opening. The steering nozzle can be configured to bend up to 90 degrees in a horizontal direction, both clockwise and counter clockwise. The steering nozzle can further be vertically movable.

In an embodiment, the rear opening of each of the at least one propeller is circular.

In another embodiment, when the propeller chamber encloses a plurality of propellers, the hull assembly can further comprise a closing mechanism for each of the rear openings.

In a further embodiment, the hull assembly comprises a thin extension extending forwardly from a stem of the bow for preventing water pressure leakage from one side of the bow to the other.

In another embodiment, the hull assembly comprises a plate attached horizontally along a keel of the hull for preventing an expected squat of the bow due to the low pressure created by the suction of water at said bow, and also for dampening vertical oscillation of the ship.

In an embodiment, the hull assembly is mountable on a pre-existing ship hull.

In another embodiment, the hull assembly comprises at least one water intake opening extending transversally along the width of the bottom of the hull assembly and communicating with the propeller chamber, the water intake opening being configurable between an open and a closed configuration, wherein, in the open configuration, external water flow along the bottom of the hull assembly feeds into the propeller chamber, and in the closed configuration, external water flow along the bottom of the hull assembly is circulated around and does not enter the propeller chamber.

In another embodiment of the present invention, the steering nozzle comprises a plurality of collapsible segments configurable between a collapsed configuration and an expanded configuration, wherein, in the collapsed configuration, the steering nozzle is coaxial with the rear opening and, in the expanded configuration, one side of the steering nozzle is pushed out more than an opposite side, thereby bending flow exiting from the rear opening.

DETAILED DESCRIPTION

In the following description, the same numerical references refer to similar elements. Furthermore, for the sake of simplicity and clarity, namely so as to not unduly burden the figures with several references numbers, not all figures contain references to all the components and features, and references to some components and features may be found in only one figure, and components and features of the present disclosure which are illustrated in other figures can be easily inferred therefrom. The embodiments, geometrical configurations, materials mentioned and/or dimensions shown in the figures are optional, and are given for exemplification purposes only.

In addition, although the optional configurations as illustrated in the accompanying drawings comprise various components and although the optional configurations of the ship hull as shown may consist of certain geometrical configurations as explained and illustrated herein, not all of these components and geometries are essential and thus should not be taken in their restrictive sense, i.e. should not be taken as to limit the scope of the present disclosure. It is to be understood that other suitable components and co-operations thereinbetween, as well as other suitable geometrical configurations may be used for the ship hull, and corresponding parts, as briefly explained and as can be easily inferred herefrom, without departing from the scope of the disclosure.

Referring toFIG. 1, according to a first embodiment of the present invention, there is shown a hull assembly10for reducing water resistance on a ship hull12and improving the maneuverability of the ship. The ship hull12comprises a bow14on a front region, a stern16on the rear region, a keel18on a bottom region, an outer surface, and two sides. The hull assembly10comprises a plurality of ducts20, thereafter referred to as “the ducts”, attached to an outer surface of the ship hull12, and a propeller chamber22for enclosing at least one propeller24.

In some embodiments, the ducts20extend longitudinally from the front part to the rear part of the ship, and more particularly from a front part of the bow14to a rear part of the stern16. At the bow14, the ducts20are transversally distributed from the waterline26, where the hull meets the surface of the water, to the baseline28corresponding to the lowest part of the bottom region. The ducts20can cover the entire hull area below the waterline, but can also cover any sub-part of this area as known by the person skilled in the art. Flowing water from the front of the bow14to the rear of the stern16produces a pressure gradient between the bow14and the stern16, as the water pressure at the bow14is decreased.

The ducts20comprise a plurality of bow openings30along the bow14thereby allowing the water to enter the ducts20. The duct can be perforated on the region extended from the front part of the bow14to the beam region, which is the widest point of the hull measured at the waterline. As the bow14is the front part of the ship that enters and displaces the water in front of the ship when the ship is in motion, water pressure on the hull ahead of the bow14represents a considerable resistance to the ship motion.

The bow openings30allow for the water on the front part of the ship to flow directly toward the rear of the ship. The flowing water is not displaced by the hull and the water pressure applied on the hull is reduced, thereby reducing wave making resistance. Each of the bow openings30has a dimension that can vary in function of the bow opening position. In some embodiments, the dimension of the bow openings30decreases along the transversal direction from the waterline downward to the baseline. The dimension of the bow opening is therefore larger near the waterline where a larger amount of water is expected to be displaced. In some other embodiments, the dimension of the bow openings30is predetermined and is proportional to the amount of water that is expected to be displaced by the hull at the position of said bow opening. As a larger amount of water is displaced near the waterline than near the baseline, the dimension generally decreases downwardly to the baseline. In some embodiments, the dimension of the bow openings30decreases along the longitudinal direction from the front part of the bow14(or stem) to the beam, as defined previously. Indeed, due to the curvature of the bow14, the water pressure applied on the stem of the bow14is larger than the water pressure applied on the beam, where the outer surface of the ship hull12is substantially tangential to the motion of the ship heading straightforward.

The dimension of the bow openings30can further be proportional to the expected water pressure due to the expected water displacement. The person skilled in the art will understand that the decrease of the dimension of the bow openings30in the longitudinal direction can be coupled with the decrease of the dimension of the bow openings30in the transversal direction. Each of the ducts20comprises at least one stern opening (not shown) through which the water, which has entered by the bow openings30, comes out. The ship hull12can therefore comprise as many stern openings as ducts20. The stern openings are preferably located near the propeller chamber22where at least one propeller24is enclosed. The propeller chamber22is therefore fed with the water coming from the front of the ship. Expelling water from the stern openings increases the water pressure applied at the stern16of the ship. As the water coming out from the stern openings has been removed from the bow14a pressure gradient is created, the resistance of the ship hull12is decreased and the speed of the hull increases for a same amount of consumed energy. Each of the stern openings can comprise a closing gate (not shown), which can be closable singularly and independently from the closing gate of the remaining stern openings. The closing gates allow for controlling the amount of water being sucked through the ducts20into the propeller chamber and therefore the water pressure applied to the bow14and the stern16of the ship hull12. The closing gates can also be closed singularly and independently in order to be able to close a duct that would rise above the waterline, when the ship is not loaded for example. Indeed, in case a duct rises above the waterline, air is drawn in by the low pressure in the propeller chamber and the pressure applied to the stern16of the ship decreases, thereby decreasing the pressure gradient, hindering the ship motion, lowering

the ship speed and/or increasing the energy consumption. The closing gates can also be closed partially on one side of the hull or the other, meaning that a portion of the closing gates are closed while the rest is opened on one side of the ship hull12. For example, if a portion of the closing gates is closed on the right side, the water suction at the left side will be higher than at the right

side, and the water pressure on the front left side is lower than at the front right side.

The ship thereby tends to turn or shift toward the left side.

Now referring toFIG. 2, in some embodiments, the hull assembly10also comprises a propeller chamber22. The propeller chamber22encloses one propeller24in case of a single screw ship, but can further enclose more than one propeller24, i.e. a plurality of propellers24. It can enclose two propellers24in case of a dual screw ship for example. The propeller chamber22is defined within the stern16by the right and left side of the ship hull12, the bottom of the ship hull12and the rear part of the stern16. Such parts of the ship can be extended to form the chamber and enclose the at least one propeller24. Therefore, the sides of the hull correspond to the sides of the propeller chamber22along the stern16. In some embodiments, chamber openings34are provided to the propeller chamber22. More specifically, the propeller chamber22comprises at least one chamber opening34on each of the right and left sides of the propeller chamber22. Water on the outer side of the hull can directly enter the propeller chamber22through the chamber openings34. Each of the chamber openings34is singularly, independently and partially closable, thereby allowing for the control of the amount of water entering on each opposed side of the propeller chamber22.

In some embodiments, the chamber openings34are closable by a plurality of vertical door assemblies36. Such door assemblies36can have an increasing size toward the rear part of the stern16, in order to allow a gradual increasing amount of flow into the propeller chamber along a length of the vessel towards the stern, and such that the larger downstream door assemblies are able to redirect flow that has not already been redirected by the smaller upstream door assemblies. In some preferred embodiments, the door assemblies36comprise vertical closing louvers38. The vertical louvers38can therefore have an increasing size towards the rear part of the stern16.

In some embodiments, the door assemblies36also comprise an actuating system for controlling the positioning of the vertical closing louvers38. The vertical closing louvers38can thereby be closed partially, at a predetermined angle, allowing for the control of the amount of water entering the propeller chamber22. It is understood that the door assemblies36can comprise any closing mechanism and/or controlling mechanism known by the person skilled in the art. The chamber openings34and door assemblies36help minimize the formation of a thick boundary layer on the side of the hull and therefore reduces the effect of viscous drag, in addition to a maneuvering capability they provide.

The propeller chamber22also comprises a rear opening40for each of the at least one propeller24enclosed therein. Each of the rear openings40is singularly and independently closable by a closing mechanism, thereby allowing restricting water propulsion or water suction from one of the propellers24only. Lateral maneuvers of the ship can be induced by opening only one of the rear openings40and closing the rest.

In a preferred embodiment the rear opening is circular, but the person in the art will understand that it can be of any other suitable shape and/or size.

In some embodiments, referring toFIG. 4B, the ship comprises a steering nozzle42at the rear part of the stern16, in place of a rudder. The steering nozzle42can be moved using at least on actuator, thereby enabling lateral movements of the ship. Such steering nozzle42can comprise a duct bendable up to 90 degree toward both right and left sides of the ship hull12.

In some embodiments, the steering nozzle42comprises a plurality of pipe segments adjustable and rotatable as a group with respect to each other. The pipe segments can be fitted with one or more actuators that allow moving the steering nozzle42and laterally maneuvering the ship. The steering nozzle42can be mounted to or extend from the rear opening of the propeller chamber22, and has therefore a dimension and a shape corresponding to the dimension and the shape of said rear opening. In some embodiment, the steering nozzle42comprises a circular bendable duct. However, it is understood by the person skilled in the art that such a steering nozzle42can have any suitable shape and/or size. In some embodiments, the steering nozzle42is vertically movable and acts as a trim to change the angle of the water propulsion and help the ship raise, or otherwise lower the stern. Other additional features can be added to the hull assembly10. For example, referring toFIGS. 3 and 5, in some embodiments, a thin extension44(or a stem fin) can extend forwardly from the front part of the bow14, i.e. the stem. This thin extension44at the front of the ship allows segregating the water pressure applied to the right side and the left side of the ship's bow. Pressure leakages from one side to the other side of the bow14are minimized by the extension44. The extension44will maximise the benefit of the pressure difference induced by the suction when there is a need to steer the front of the ship in a specific direction. Without the extension44, the water from the high pressure side will simply circumvent around the stem and feed the low

pressure side which will cancel the benefit.

Still referring toFIGS. 3 and 5, a plate46can also be attached horizontally along the keel of the ship hull12can prevent a possible squat effect. The low-pressure zone at the bow, which is formed by the suction of water can induce this squat effect. The squat effect results from a lower pressure underneath the ship that is therefore pulled dangerously closer to the seabed. The horizontal plate46can reduce the squat effect by increasing the horizontal surface in contact with the water and therefore preventing vertical sinking of the ship's bow toward the seabed. In other words, the plate46creates a pressure gradient where the pressure below the plate46is higher than the top where the openings are located, and such that the high pressure below the plate46will push the front up and prevent the squat effect. Vertical oscillations of the ship are also dampened by the added mass induced by the presence of the horizontal plate46along the keel, and the ship is therefore

stabilized during motion in rough water. In some further embodiments, as seen inFIG. 2, the hull assembly10can comprise at least one water intake opening50that extends along the bottom

of the hull assembly10. The intake opening50extends transversally along the width of the bottom of the hull assembly10and communicates with the propeller chamber22. In an open configuration, water can flow along the bottom of the hull and feed the propeller chamber22. The ship propulsion is therefore increased by the additional amount of water entering the propeller chamber22. This configuration can be useful when the vessel is in operational states where less water is being fed into the propeller chamber22from the ducts. In a closed configuration, the water flows along the bottom of the hull but circulates around and does not enter the propeller chamber22. Moreover, the intake opening50provides acceleration of the water layer at the bottom of the hull.

This acceleration minimises the formation of a thick boundary layer and therefore reduces the effect of viscous drag. The hull assembly10as described herein allows reducing the wave-making

resistance of the ship and the viscous drag mitigation, but also improving the ship maneuverability.

In a headway cruise scenario, as illustrated inFIG. 4A, the hull assembly10allows reducing the wave-making resistance at cruise speed. In a stationary situation, the propeller chamber22is full of water, which has entered through both the chamber openings34and the rear openings40. Once the propeller24start rotating, the water is propelled out of the propeller chamber22and a vacuum is created. As the stern openings communicate to the propeller chamber22, the vacuum causes water to be drawn from the front to the rear of the hull assembly10through the ducts20. The water, which is normally displaced by the hull, is drawn to the propeller chamber22and expelled out

by the propeller24. This creates a low pressure area52at the front part of the bow14, and this reduces the wave-making resistance responsible for slow-down of the ship and increase of energy consumption. A low pressure area54is also formed proximate the chamber openings34and door assemblies36when the door assemblies are opened. Upon activation of the propeller24and creation of vacuum in the propeller chamber22, more water at the bow14flows through the ducts20to the stern16. The water pressure is further decreased at the bow14and further

increased at the stern16, creating a high pressure area behind nozzle42and a large pressure gradient between the bow14and the stern16. Such a pressure gradient helps increasing the speed of the ship. During deceleration, the amount of water flowing through the ducts20is reduced by the reduction of the propeller24rotational speed or the decrease of the pitch of the propeller24blade. The pressure gradient and therefore the ship speed is reduced. When the propeller24is stopped, and the thrust is reversed: the water stops flowing from the bow14to the stern16and is instead reversely propelled out from the bow openings30. The water pressure gradient is therefore reversed, with a higher water pressure at the bow14and a lower water pressure at the stern16, and the ship speed is immediately reduced, until complete stop of the ship. In a complete stop configuration of the ship, viscous drag is re- introduced due to the absence of suction from the chamber openings34and the intake opening50at the bottom. The person skilled in the art will appreciate that during such maneuvers, the movement and speed of the ship are controlled by adjusting the amount of water expelled out of any one of the stern openings, chamber openings34

and rear openings40, which are singularly, independently and/or partially closable. The hull assembly10as described herein also allows for turn, lateral shift, or even complete reversal of the ship direction. The possibility of singularly, independently and/or partially close the stern, chamber and/or rear openings results in the ability to control the amount of water being sucked in from each side of the hull, and thereby allows controlling the pressure at four pressure

areas of the ship hull12, i.e. right and left sides of the bow14and right and left sides of the

stern16. The control of the pressure in those four pressure areas improves the maneuverability of the ship. For example in a right turn maneuver, as illustrated inFIG. 4B, the left stern openings of the hull are partially or entirely closed inducing more water suction from the right side and more water pressure applied on the front left side of the hull. This creates a pressure difference at the bow14, with lower pressure area56on the right side opposed to a higher pressure area58on the left side, causing the bow14to move to the right. At the same time the right chamber opening34can be closed or partially closed while the left chamber opening34stays open. Water suction on the left side of the stern16creates a pressure difference at the stern16opposed to the pressure difference at the bow14. The stern16thereby moves to the left in a coordinated turn with the bow14. In addition, the steering nozzle42can further be used for sharp turns. In the case of the right turn for example or for a complete 180 degree-rotation of the ship, the steering nozzle42is bent up to 90 degree toward the right side of the stern16. In case of a complete reversal of the ship movement, the four pressure areas and the steering nozzle42are controlled simultaneously with deceleration or stopping of the ship. The thrust is inverted and the ship, in backward motion, is maneuvered laterally by controlling the stern16, chamber, and rear openings40as well as the steering nozzle42, in a manner similar to that of the turn maneuver. Lateral shifting of the ship while maintaining the same heading direction is also possible by lowering the pressure at the side of the required lateral shift. The stern openings and the chamber opening34of the side opposed to the required lateral shift are partially closed. The ship shifts in the required lateral shift without turning. For example, a right lateral movement is achieved by partially closing the left stern openings and the left chamber opening34. In-port 180-degree turns can also be easily achieved by using the described hull assembly10. As for the turn maneuver, low pressure is imparted at two diagonally opposed pressure areas of the ship hull12while high pressure is imparted to the two other opposed pressure areas of the ship hull12. For example, for a right 180 degree rotation, low pressure is imparted to the right side of the bow14and the left side of the stern16by closing the stern openings on the left side and closing chamber opening34on the right side.

Opposed pressure gradient are therefore imparted to the bow14and the stern16. In addition, the steering nozzle42is bent 90 degree to the right. The person skilled in the art will understand that the sharpness of the turn depends on the angle of the bendable steering nozzle42as well as on the amount of water flowing through the nozzle42, which depends on the partial closing of the stern openings and of the chamber openings34.

The use of the hull assembly10as described herein also allows for lateral pier approach and lateral pier departure. In lateral approach, the steering nozzle42is bent 90 degree toward the direction opposite to the pier; the stern openings and the chamber opening34of the side of the hull opposed to the pier ship are closed. The water pressure is therefore lower on the side facing the pier, and the bow14and the stern16can move laterally and simultaneously towards the pier. The configuration for lateral departure is the exact inverse than the configuration used for lateral pier approach. Preferably, in some implementations, for the maneuvers when the nozzle42is bent 90 degrees, only one propeller is used and the idle propeller is closed to prevent water from moving through its corresponding rear openings40and disrupting the maneuver. In another embodiment of the present invention, the steering nozzle comprises a plurality of collapsible segments configurable between a collapsed configuration and an expanded configuration, wherein, in the collapsed configuration, the steering nozzle is coaxial with the rear opening and, in the expanded configuration, one side of the steering nozzle is pushed out more than an opposite side, thereby bending flow exiting from the rear opening.

Of course, the scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole. Numerous modifications could be made to the above-described embodiments without

departing from the scope of the claims, as apparent to a person skilled in the art.

Furthermore, it is apparent that this invention can apply to many other uses.