GB2457019A

GB2457019A - Propulsion system for a vessel suspended in a fluid.

Info

Publication number: GB2457019A
Application number: GB0801578A
Authority: GB
Inventors: Jonathan Evans
Original assignee: ADVANCED POWER TECHNOLOGY Ltd
Current assignee: ADVANCED POWER TECHNOLOGY Ltd
Priority date: 2008-01-29
Filing date: 2008-01-29
Publication date: 2009-08-05
Also published as: GB0801578D0

Abstract

A propulsion system for a vessel suspended in a fluid, e.g. a boat or aircraft, comprises four propulsion units 3a - d wherein each unit comprises a pipe 4 a- d which may be connected below the waterline between the sides and either the front or the rear of the hull 2 of the vessel. Each pipe comprises two conduit parts, a first conduit part 5 a - d is terminated in a side aperture 6a - d and directed at least partly transversely to the vessel. A first pair of side apertures 6a, 6b is provided on either side of a central axis 13 of the vessel and forward of a second pair 6c, 6d provided on either side of the axis. The second conduit parts 7a - d, in fluid communication with the first conduit parts, terminate in second apertures 8 a- d such that there is a fluid path through the first and second conduit parts. Each second conduit part at the second aperture is directed at least partially parallel to the central axis. A plurality of independently controllable fluid drives 9 - 11 are provided at a position on a fluid path through a second and first conduit part to a respective different one of the side apertures of a pair. There is also provided a method of maneuvering a vessel and a computer program configured to provide signals for controlling a plurality of fluid drives to perform the method of maneuvering a vessel.

Description

1 2457019

PROPULSION SYSTEM FOR A VESSEL SUSPENDED IN A FLUID

The invention relates to a propulsion system for a vessel suspended in a fluid, e.g. a boat or aircraft, including: at least four side apertures terminating respective first conduit parts directed at least partly transversely to the vessel, at least at the side apertures, a first pair of the side apertures being provided on either side of a central axis of the vessel, forward of a second pair provided on either side of the central axis; for each pair of side apertures, at least one further aperture, terminating a respective further conduit part, the further conduit part being in fluid communication with at least one of the first conduit parts terminated by a side aperture of the pair such as to establish at least one fluid path through the further conduit part and a first conduit part, each further conduit part directed at least partially parallel to the central axis at the further aperture terminating it; and a plurality of independently controllable fluid drives. S... * . S...

The invention also relates to a method of manoeuvring a vessel suspended : in a fluid, e.g. a boat or aircraft, which vessel is provided with: S...

S..... at least four side apertures terminating respective first conduit . : parts directed at least partly transversely to the vessel, at least at the side :..:: apertures, S...

a first pair of the side apertures being provided on either side of a central axis of the vessel, forward of a second pair provided on either side of the central axis; for each pair of side apertures, at least one further aperture, terminating a respective further conduit part, the further conduit part being in fluid communication with at least one of the first conduit parts terminated by a side aperture of the pair such as to establish at least one fluid path through the further conduit part and a first conduit part, and each further conduit part being directed at least partially parallel to the central axis at the further aperture terminating it; the method including controlling propulsion means for driving fluid along fluid paths through respective ones of the side apertures of a pair.

The invention also relates to a vessel for water-borne navigation.

The invention also relates to a computer programme.

GB-A-1,387,208 discloses an ocean-going barge. The barge has forward and aft longitudinal tunnels, each having oppositely disposed inboard and outboard ends. The barge has forward and aft bottom tunnels, each terminating at one end in a bottom port. The outboard end of each longitudinal tunnel terminates in an end port, and the inboard end of each longitudinal tunnel is joined to a respective bottom tunnel. The barge has transverse tunnels having oppositely disposed inboard and outboard end.

The outboard ends of the transverse tunnels terminate in side ports, and the inboard ends of the transverse tunnels respectively join the inboard end of a respective longitudinal tunnel. Forward and aft propellers are S...

mounted in the longitudinal tunnels for drawing in water in any of the respectively associated ports. The barge has engines mounted amidships in the barge for respectively driving the propellers in any combination of direction of rotation. In the drawings, the barge is disclosed as having a single propeller forwards and two propellers aft, but any combination of one or two propellers forward or aft and relatively arranged as illustrated for both position and number can be used. The control of the engine, all valves, vanes and fins can be electronically automated.

A problem of the known propulsion system will occur when propellers of a combination forward or aft are operated in opposite senses to effect a gyrating movement by expelling water on one side (e.g. one of the side ports) and drawing it in (e.g. through the associated end port). A circulating flow is established between the end ports of a pair, which pre-dominates and is rather inefficient. This is the case even when the bottom port is closed. To be able to turn more effectively in a tight spot, vanes and other types of deflectors are therefore provided. All this complicates the control of the propulsion system.

It is an object of the invention to provide a propulsion system, method of manoeuvring a vessel, vessel for waterborne navigation and computer programme of the types mentioned in the opening paragraphs that allow forwards and reverse driving, as well as precise manoeuvring on the spot using fluid drives positioned in conduits in an efficient manner.

This object is achieved by the propulsion system according to the invention, which is characterised in that fluid drives are each provided at a position on only a fluid path or paths through a further conduit part and a first conduit part to a respective different one of the side apertures of a : pair. *... * *

Because fluid drives are each provided at a position on only a fluid path or paths through a further conduit part and a first conduit part to a respective different one of the side apertures of a pair, all of the fluid :.:::. propelled by a fluid drive is expelled or drawn in through a side port in a direction commensurate with the desired sideways thrust. This in contrast to the prior art, in which a large amount of the fluid propelled by a fluid drive is directed through an end port to the other of the fluid drives and then expelled through an end port again. The propulsion system is thus more efficient, as well as being more effective in turning the vessel. By providing for each pair of side apertures, at least one further aperture, terminating a respective further conduit part directed at least partially parallel to the central axis at the further aperture terminating it, it is possible to provide sideways thrust and oppositely directed thrust in parallel to the central axis, so that the vessel can be turned without propelling it forwards or backwards. Because a further conduit part is in fluid communication with at least one of the first conduit parts terminating a side aperture of the pair such as to establish at least one fluid path from through the further conduit part and a first conduit part, the same fluid drives can be used for propulsion, forwards or backwards, as for manoeuvring. The need for vanes, rudders or the like is much reduced, to the point of being obviated.

In an embodiment of the propulsion system, fluid drives are each provided at a position on only a fluid path or paths through a further conduit part and a first conduit part to a respective different one of the side apertures of each pair.

An effect is to provide the possibility of sideways movement, i.e. transverse movement with respect to the central axis. Because the fluid .. : drives are provided on only a fluid path to one of the side apertures of a pair, the fluid drives associated with those side apertures can be driven to enhance the effect of sideways movement. Fluid flows expelled and drawn in through the further apertures cancel each other. By providing a first and a second pair, and operating the fluid drives at appropriate power settings, turning of the vessel can be prevented.

In an embodiment, the further conduit part(s) in fluid communication with the side apertures of the first pair are directed, at least at their terminating further aperture(s) in a direction at least partially opposite to the further conduit part(s) in fluid communication with the side apertures of the second pair.

An effect is to allow manoeuvring with substantially no forwards or reverse motion of the vessel. Opposing fluid flow components parallel to the central axis can be set up at the positions of the first and second pair of side apertures along the central axis. Thus, the need for further fluid drives to maintain position is obviated.

In an embodiment, each fluid path between a first side aperture of a pair and a further aperture is separate from each fluid path from a second side aperture of a pair to a further aperture.

An effect is to increase the efficiency, particular when steering during forwards or reverse motion, since fluid flows from one side aperture to the other are not established when there is a differential between the impulse imparted by the fluid drives associated with a pair of side apertures. A further effect is to make it easier to implement a control strategy, since the settings of the fluid drive or drives associated with one side aperture of the pair will not influence the throughput through the other side aperture. * *** * ***

In an embodiment, at least the first conduit parts terminated by first side apertures of a pair and the further aperture(s) with which they are respectively in fluid communication are configured such that their central :.:::. axes are arranged generally symmetrically with respect to a plane including the central axis of the vessel.

An effect is that there is generally no moment acting on the ship when the fluid drives associated with the respective side apertures of a pair are driven at equal power. Flows of fluid through the side apertures will have approximately equal impulse, as will the flows of fluid through the associated further apertures. One consequence is that implementations are made possible which have no need for vanes and rudders to keep course.

In an embodiment, on each side of the central axis, the first conduit part terminated by the side aperture of the first pair and the first conduit part terminated by the side aperture of the second pair are configured such that their central axes are arranged generally symmetrically with respect to a plane perpendicular to the central axis of the vessel.

An effect is to make it possible to effect a gyrating manoeuvre with substantially no forward or sideways movement, e.g. by operating the fluid drives associated with the side apertures of the first and second pair at equal power in opposite directions.

In an embodiment, a filter is provided at each of the first and further conduit parts, preferably over the side aperture(s) and/or the further aperture(s).

.. : According to another aspect, the method of manoeuvring a vessel * .** suspended in a fluid according to the invention is characterised by controlling fluid drives, provided each at a position on only a fluid path * or paths through a further conduit part and a first conduit part to a respective different one of the side apertures of a pair. * *. * * S *Se.

The method provides increased manoeuvrability in an effective and efficient way.

In an embodiment, the method includes the use of a propulsion system according to the invention.

According to another aspect of the invention, there is provided a vessel for water-borne navigation, provided with a propulsion system according to the invention.

In an embodiment, at least the first conduit parts terminated by side apertures of a pair and the further aperture(s) with which they are respectively in fluid communication are configured such that their central axes are arranged generally symmetrically with respect to a plane including the central axis of the vessel, and the vessel comprises a hull, the hull being configured generally symmetrically with respect to the plane including the central axis.

An effect is to allow for propulsion forwards or backwards by operating the fluid drives on opposite sides of the central axis at generally equal power. There is then generally little or no need for vanes or rudders to keep the vessel moving in a straight line. This makes the vessel more efficient.

.. : In an embodiment, on each side of the central axis, the first conduit part *...

terminated by the side aperture of the first pair and the first conduit part terminated by the side aperture of the second pair are configured such that their central axes are arranged generally symmetrically with respect S..

to a plane perpendicular to the central axis of the vessel, and the vessel comprises a hull, the hull being configured generally symmetrically with respect to the plane perpendicular to the central axis of the vessel.

An effect is to allow for substantially stationary gyrating movement, since the moment set up by operating the fluid drives is in the exact opposite direction to that caused by resistance in the water, there being substantially no residual forces.

According to another aspect of the invention, there is provided a computer programme including a set of instructions capable, when incorporated in a machine-readable medium, of causing a system having information processing capabilities and configured to provide signals for controlling a plurality of fluid drives to perform a method according to the invention.

The computer programme translates input signals indicative of manoeuvres to be carried out into settings for the fluid drives that are appropriate for carrying out the desired manoeuvres.

The invention will now be explained in further detail with reference to the accompanying drawings, in which: Fig. 1 is a schematic plan cross-sectional view of a narrow boat provided with a first version of a propulsion system; Fig. 2 is a schematic plan cross-sectional view of a narrow boat provided .. : with a second version of a propulsion system; *...

Fig. 3 is a schematic plan cross-sectional view of the narrow boat according to Fig. 1 showing the flow of water when the narrow boat is moving forwards and turning to port (to the left); Fig. 4 is a schematic plan cross-sectional view of the narrow boat :.;::. according to Fig. 1 when gyrating in an anti-clockwise sense; Fig. 5 is a schematic plan cross-section view of the narrow boat according to Fig. 1 showing the flow of water when the narrow boat is moving laterally to port (to the left); Fig. 6 is a schematic plan cross-sectional view of the narrow boat according to Fig. 1 showing the flow of water when the narrow boat is reversing; and Fig. 7 is a schematic view of a unit provided at one of four positions in the hull of the narrow boat according to Fig. 1 or2.

Canals are extremely restricted waterways requiring accurate manoeuvring into locks etc. Arrangements using propellers and rudders make narrow boats difficult to manoeuvre and are readily fouled by debris and vegetation.

A narrow boat 1 is shown schematically by way of horizontal cross-sections through its hull 2. In the embodiment of Figs. 1 and 3-6, four propulsion units 3a-3d are provided.

Each propulsion unit 3 comprises a pipe 4a-4d which is connected below the waterline between the sides and either the front or the rear of the hull 2 of the narrow boat 1. In the embodiment of Figs. 1 and 3-6, a pipe 4 comprises two parts. A first part 5 is terminated by a side aperture 6 and a further part 7 is terminated by a further aperture 8. The first and further parts 5,7 can be separated by other conduits or conduit parts in other embodiments, as long as they are in fluid communication.

They need not be substantially straight as shown, either. In yet another * * embodiment, some or all of the pipes 4 bifurcate towards the forward or aft side of the narrow boat 1. * ** * , * S...

Each pipe 4a-4d houses a shaft 9 with a propeller lOa-lOd, which, in use, draws water through the pipe 4 to discharge it at a higher velocity, thus providing thrust. In the embodiment discussed herein in detail, the drive, and thus the flow of water, is reversible. The propellers 10 are designed to provide generally equal thrust in both directions of rotation. In an embodiment, the propellers 10 have no leading edge. In the illustrated embodiment, each shaft 9 is driven by a separate motor 11. A control unit 12 computes the appropriate settings for each motor 11 in response to a control signal provided by a user and indicative of the desired strength and direction of thrust. In one embodiment, the control unit 12 is implemented in the form of an appropriately programmed computer, e.g. an embedded system. In one embodiment, the control signal forming its input is provided wirelessly from a remote location. In another embodiment, it is provided using controls mounted on the narrow boat 1, e.g. in the form of a joystick, steering wheel and power lever, etc. It is observed that another embodiment may include fluid drives in the shape of magneto-hydrodynamic propulsion units at each pipe 4. In yet another embodiment, two or more shafts 9 are powered by one motor, with a variable transmission unit allowing for independent control of the fluid impulse provided by each propeller 10.

At least where the further aperture 8 terminates the further part 7, a central axis of the pipe 4 is oriented substantially parallel to a central axis 13 of the hull 2. In another embodiment, the orientation is at least partially parallel to the central axis 13. To provide only forwards or reverse thrust, the further parts 7a,7b forming a pair at one end of the hull 2 are generally arranged to be each other's mirror image with respect to an upright plane including the central axis 13 of the hull 2. Similarly, o the first parts 5a,5b terminated by side apertures 6a,ób forming a pair are generally arranged to be each other's mirror image with respect to the :.:::. upright plane including the central axis 13. This plane also substantially coincides with a plane of symmetry of the hull 2, at least that part of the hull that, in use, is below the waterline. As a consequence, when an equal amount of thrust is provided by the propellers lOa,lOb of a pair, no moment is imparted. The narrow boat 1 can keep to a straight line without the use of rudders or vanes.

Referring to Fig. 2, a variant of a propulsion system is shown, in which a single further aperture 14 is provided for a first pair of side apertures 15a,15b. The further aperture 14 terminates a single further conduit part 16, which is in fluid communication with a first conduit part 17a terminated by a first side aperture 15a and in fluid communication with a first conduit part 17b terminated by a second side aperture 15b of the pair. Thus, two fluid paths are established from the further aperture 14: one to each side aperture 15a,15b. The two fluid paths overlap in the further conduit part 16. The fluid drives formed by electric motors 18a,18b, shafts 19a,19b and propellers 20a,20b are each provided at a position on only one of the two fluid paths. This is, of course, also the case for the embodiment of Fig. 1. As in that embodiment, a control unit 21 is configured to determine the settings for the motors 18a-18d that are required to impart a desired thrust in a desired direction.

Compared to the embodiment of Fig. 2, the embodiment of Figs. I and 3-6 is easier to control and more efficient. This is because in that embodiment, each fluid path between a first side aperture óa of, say, the first pair, and a further aperture 8a associated with that pair is separate from each fluid path between a second side aperture 6b of that pair and a further aperture 8b. The effect on the thrust in forward and lateral * * direction for a given setting of each motor 11 is given. In the embodiment of Fig. 2, some of the water flow through a side aperture 15 passes through the further aperture 14 and some passes through the other side aperture 15, depending on the setting of the other motor 18, ambient water pressures, etc. Figs. 3-6 illustrate how, in the embodiment of Fig. 1, the various rotation configurations of the motors ha-lid adjust the movement and/or direction of the narrow boat 1. The solid arrows indicate the direction of flows of water powered by the propulsion units 3a-3d that are operational.

In Fig. 3, the narrow boat 1 is manoeuvred to execute a left turn whilst moving forwards. Motors llc,lld (not shown in Fig. 3) at the rear of the narrow boat 1 both impart equal thrust by expelling water through further apertures 8c,8d oriented in a direction generally parallel to the central axis 13. The water is drawn in through associated side apertures 6c,6d in roughly equal amounts at generally equal velocities.

Thus, the second pair of propulsion units 3c,3d imparts purely forwards thrust to the narrow boat 1. Only one of the first pair of propulsion units 3a,3b is operational to expel water out through a second side aperture 6b of the forward pair. This water is drawn in through the further aperture 8b with which it is in fluid communication. The first part 5b of the pipe 4b terminated by the second side aperture 6b is oriented, at least at the second side aperture 6b in a direction partly transversely to the narrow boat 1 and partially parallel to the central axis 13 and opposite to the orientation of the further part 7b through which the fluid path on which its associated drive unit lies. An effect is to support the forwards propulsion and provide sideways motion to the front of the narrow boat 1. Manoeuvring is thus carried out relatively efficiently.

SI * S

S a **e

* In Fig. 4, the narrow boat I is shown executing a generally gyrating manoeuvre. That is to say that the narrow boat 1 turns generally about a centroid of the hull 2, without causing its displacement. Only one propulsion unit 3b,3c of each of the first and second pair is operative.

The motors llb,llc are controlled to impart a generally equal impulse to water drawn in through further apertures 8b,8c and expelled through side apertures 6b,6c. This is a relatively simple control strategy. It works because the propulsion units 3a-3d are placed generally point-symmetrically in a plane with respect to a point coinciding with or overlying the centroid of the hull 2, and because the pipes 4a-4d are of generally the same configuration. In particular, the first parts 5b,5c of the pipes 4b,4c are oriented in opposite directions and at the same angle to the central axis 13 and the further parts 7b,7c of the pipes 4b,c are oriented in opposite directions and at the same angle (namely generally QO) to the central axis 13. Thus, the components parallel to the central axis 13 of the impulse provided by the flows through the further apertures 8b,8c and side apertures 6b,6c cancel out, at least approximately. Conversely, the transverse components are additive in generating a moment about a vertical axis of the narrow boat 1.

Referring to Fig. 4, the same aspects of the configuration of the propulsion units 3a-d allow for relatively simple and efficient control of the propulsion system to bring about a purely transverse movement of the narrow boat 1. This is useful when docking or manoeuvring to enter a lock or pass through a narrow opening under a bridge, for example. Only one of each pair of propulsion units 3b,3d is operative, namely those on the same side of the central axis 13. There is substantially no forwards or reverse movement, because, on each side of the central axis 13, at . . least the first pipe part Sb terminated by the side aperture 6b of the forward pair of side apertures 6a,6b and the first pipe part 5d terminated * ** by the side aperture 6d of the aft pair of side apertures 6c,6d are *.* configured such that their central axes are arranged generally symmetrically with respect to a plane perpendicular to the central axis 13.

Thus, the components parallel to the central axis 13 of the thrusts provided by the propulsion units 3b,3d cancel out substantially. As can be seen from the arrows indicating the direction of the flow of water, the components in the transverse direction are additive. The further parts 7b,7d of the pipes 4b,4d are oriented substantially in parallel to the central axis 13 and therefore generally generate no sideways thrust.

The configuration of the propulsion system as described above enables the narrow boat 1 to be manoeuvred forwards, backwards, purely sideways, and about a generally stationary vertical axis, using only the propulsion units 3a-3d. Additional propulsion units 3 may be provided, but are not necessary. In particular, vanes or other types of deflectors of water jets are not required. This reduces the number of protruding parts on which debris or water plants can catch. The same effect is provided by mounting the propellers 10 in pipes 4. To reduce the risk of malfunction even further, grids 22,23 (Fig. 7) are provided at each of the first and further pipe parts 5,7.

These grids may be positioned slightly within the pipe parts 5,7, but are more effective when provided over the side apertures 6 and further apertures 8. The illustrated positioning of the side apertures 6 and further apertures 8 such that they are generally flush with the hull 2 already contributes to preventing debris from being caught. Providing the grids 22,23 over the apertures 6,8 then has as a consequence that they are in a position from which they are removable. A slotted and/or hinged mechanism for drawing the grids 22,23 to the surface further improves the ease of maintenance. S.. * .*

Additionally or alternatively, the propulsion system can be used to *.S reverse the flow of water through the grids 22,23 to clear them of any trapped debris. In particular, the propulsion units 3a-3d can be set to provide a balanced reverse thrust, so that the grids 22,23 are cleared, but the narrow boat 1 remains generally stationary. Thus, a powerful jet can be provided in a generally clear stretch of water, instead of a weak jet whilst the narrow boat 1 is moored.

The marine propulsion system presented herein thus allows for control of the direction of a waterborne craft with great precision in forwards, backwards and sideways direction, is generally impervious to restrictions on its operation by debris or vegetation, and is easy to clean through the use of balanced reverse thrusting of the system.

The invention is not limited to the embodiments described above, which may be varied within the scope of the accompanying claims. For example, the propulsion system may be used to power an airship. * * * S

S *5S * .1 * S

I

III

I S. * S S...

II S

S S * S.

Claims

1. Propulsion system for a vessel (1) suspended in a fluid, e.g. a boat or aircraft, including at least four side apertures (6;15) terminating respective first conduit parts (5;17) directed at least partly transversely to the vessel (1), at least at the side apertures (6;15), a first pair of the side apertures (6a,6b;15a,15b) being provided on either side of a central axis (13) of the vessel (1), forward of a second pair (6c,6d;15c,15d) provided on either side of the central axis (13); for each pair of side apertures (6;15), at least one further aperture (8;14), terminating a respective further conduit part (7;16), the further conduit part (7;16) being in fluid communication with at least one of the first conduit parts (5;17) terminated by a side aperture (6;15) of the pair such as to establish at least one fluid path through the further conduit part (7;16) and a first conduit part (5;17), each further conduit part (7;16) directed at least partially parallel to the central axis (13) at the further aperture (8;14) terminating it; and a plurality of independently controllable fluid drives (9-11;18-20), characterised in that fluid drives (9-11;18-20) are each provided at a position on only a fluid path or paths through a further conduit part (7;16) and a first conduit part (5;17) to a respective different one of the side apertures (6:15) of a pair.

2. Propulsion system according to claim 1, wherein fluid drives (9-11;18-20) are each provided at a position on only a fluid path or paths through a further conduit part (7;16) and a first conduit part (5;17) to a respective different one of the side apertures (6:15) of each pair.

3. Propulsion system according to claim I or 2, wherein the further conduit part(s) (7a,7b;16a) in fluid communication with the side apertures (6a,6b;15a,15b) of the first pair are directed, at least at their terminating further aperture(s) (8a,8b;14a) in a direction at least partially opposite to the further conduit part(s) (7c;7d;16c,16d) in fluid communication with the side apertures (6c,6d;15c,15d) of the second pair.

4. Propulsion system according to any one of the preceding claims, wherein each fluid path between a first side aperture (6a,6c) of a pair and a further aperture (8a,8c) is separate from each fluid path from a second side aperture (6b,6d) of a pair to a further aperture (8b,8d).

5. Propulsion system according to any one of the preceding claims, wherein at least the first conduit parts (5;17) terminated by first side apertures (6;15) of a pair and the further aperture(s) (8;14) with which they are respectively in fluid communication are configured such that their central axes are arranged generally symmetrically with respect to a plane including the central axis (13) of the vessel (1).

6. Propulsion system according to any one of the preceding claims, wherein, on each side of the central axis (13), the first conduit part (5a,5b;17a,17b) terminated by the side aperture (6a,6b;15a,15b) of e the first pair and the first conduit part (5c,5d;17c,17d) terminated by the side aperture (6c,6d;15c,15d) of the second pair are configured such that their central axes are arranged generally symmetrically with respect to a plane perpendicular to the central axis (13) of the vessel (1).

7. Propulsion system according to any one of the preceding claims, wherein a filter (22,23) is provided at each of the first and further conduit parts (5,7;16,17), preferably over the side aperture(s) and/or the further aperture(s).

8. Method of manoeuvring a vessel (1) suspended in a fluid, e.g. a boat or aircraft, which vessel is provided with: at least four side apertures (6;15) terminating respective first conduit parts (5;17) directed at least partly transversely to the vessel, at least at the side apertures (6:15), a first pair of the side apertures (6a, 6b;15a,15b) being provided on either side of a central axis (13) of the vessel (1), forward of a second pair (óc, ód;15c,15d) provided on either side of the central axis (13); for each pair of side apertures (6;15), at least one further aperture (8;14), terminating a respective further conduit part (7;16), the further conduit part (7;16) being in fluid communication with at least one of the first conduit parts (5;17) terminated by a side aperture (6;15) of the pair such as to establish at least one fluid path through the further conduit part (7;16) and a first conduit part (5;17), and each further conduit part (7;16) being directed at least partially parallel to the central axis (13) at the further aperture (8;14) terminating it; the method including controlling propulsion means (9-11;18-20) for ::: driving fluid along fluid paths through respective ones of the side apertures (6:15) of a pair, characterised by controlling fluid drives, provided each at a position on only a fluid

S

* path or paths through a further conduit part (7;16) and a first conduit part (5;17) to a respective different one of the side apertures (6:15) of a ***e pair. * **

9. Method according to claim 8, including the use of a propulsion system according to any one of claims 1-7.

10. Vessel for water-borne navigation, provided with a propulsion system according to any one of claims 1-7.

11. Vessel according to claim 10, wherein at least the first conduit parts (5;17) terminated by side apertures (6;15) of a pair and the further aperture(s) (8;14) with which they are respectively in fluid communication are configured such that their central axes are arranged generally symmetrically with respect to a plane including the central axis (13) of the vessel (1), and wherein the vessel comprises a hull (2), the hull (2) being configured generally symmetrically with respect to the plane including the central axis (13).

12. Vessel according to claim 10 or 11, wherein, on each side of the central axis (13), the first conduit part (5a,5b;17a,17b) terminated by the side aperture (6a,6b;15a,15b) of the first pair and the first conduit part (5c,5d;17c,17d) terminated by the side aperture of the second pair are configured such that their central axes are arranged generally symmetrically with respect to a plane perpendicular to the central axis (13) of the vessel (1), and wherein the vessel (I) comprises a hull (2), the hull (2) being configured generally symmetrically with respect to the plane perpendicular to the central axis (13) of the vessel (1).

13. Computer programme including a set of instructions capable, when S...

. : incorporated in a machine-readable medium, of causing a system (12;21) 0S having information processing capabilities and configured to provide signals for controlling a plurality of fluid drives to perform a method according to claim 8 or 9.