GB2442712A

GB2442712A - Producing a pressure potential over a body

Info

Publication number: GB2442712A
Application number: GB0620269A
Authority: GB
Inventors: Arne Kristiansen; Arne Hauglund
Original assignee: TYVIK AS
Current assignee: TYVIK AS
Priority date: 2006-10-12
Filing date: 2006-10-12
Publication date: 2008-04-16
Anticipated expiration: 2026-10-12
Also published as: WO2008044941A2; WO2008044941A3; GB0620269D0; GB2442712B

Abstract

A waterborne vessel 2 comprises a hull 4 and means for producing a pressure potential over the bow portion 6 of the hull by using streams of pressurised fluid flushed over the bow portion. The means for producing a pressure potential comprises a fluid pump and a number of tubes 8 each formed with exit ports in the form of a series of nozzles 10. The nozzles may alternatively be a series of holes, or slits or any other suitable design. The bow portion may be formed from a plurality of singly-curved, semi-cylindrical sections 12. The tubes are each disposed at the leading edge of each respective section 12. In use, pressurised fluid is discharged as streams from the nozzles, one or more of the surfaces of the sections from the respective leading edge(s), establishing a pressure potential over the sections between the leading and the trailing edges and hence over the bow. The pressurised fluid forms two effective flow streams (16, 17, Fig 2) over the bow section of the hull. Each flow stream travels over a respective half section of the bow. The two flow streams are formed by an accumulation of the individual pressurised fluid that is discharged as streams from the nozzles. The pressure potential over the hull causes the vessel to have a velocity in direction (14, Fig 2).

Description

Method. System And Apparatus For Producing A Potential Over A Body This

application concerns a method, a system and an apparatus using a hydrodynamical effect for producing a potential over a body and is concern4 particularly, although not exclusively, with an apparatus, a method and a system for the propulsion of a water borne vessel and with apparatus, a method and a system for the propulsion of an aircraft The force obtained this way, by the apparatus, method and system, is particularly useful for the propulsion and manoeuvring of ships, submarines, aeroplanes, and airships ckground Hydrodynamics concerns the relation of forces between a stream of fluid and its neighbouring fluid or body. A stream will transmit a force according to its velocity and mass density.

The lifting force of an aeroplane wing is produced by its splitting the meeting air and thus setting up two streams by its movement. As the streams follow the two sides of the wing, they get different courses and velocities The wing is lifted by the differential of the transversal forces of the streams, which, because of the speed of the aeroplane, is a relatively small differential of considerably reduced pressure, as the pressure side and the suction side are both exposed to a high air velocity.

A part of the lifting force of the wing is kinetic, produced by the vertical component of the stream induced by the angle of attack of the wing, cf the sinking of a glider The force obtained by this principle used in the present technique is currently calculated by the circulation model, as the reactive force to the centripetal force inv2fR, or by the equation describing the well known principle of Daniel Bernoulli.

These three are models, i.e. tools for calculation, while Bernoulli's equation is also a theory, i.e. a postulate concerning specific properties of reality.

The principle is referred to in a Norwegian application for patent (Arne Kristiansen: Norwegian application for patent n 19905214) and European Patent 1453726 (also Arne Kristiansen); and it is the functional principle of a patented device (Jan Inge Eielsen, Fluma AS: Norwegian patent n 305796). In practised technology, it constitutes a part of the function of aeroplane wings The application of this principle is known from an experiment with the purpose of augmenting the lift of aeroplanes at low speed Using an oblong nozzle, an added stream was drawn in between the nozzle and the surface blown. Compared to the reactive force of the stream, a thrust augmentation of 137 was attained (T.Mehus: An experimental investigation into the shape of thrust-augmenting surfaces in conjunction with Coanda-deflected jet sheets, University of Toronto, 1965.). This device is, however, not optimal, as a higher efficiency is achieved when the stream has its highest velocity close to the surface, cf the aeroplane wing. By the same way of calculation, a passenger aeroplane has a thrust augmentation of 25-4.

An optimal conversion of energy for a technical purpose presupposes that the different functions of the physical variables are separated within the apparatus. This is what is seen in Watt's placing the condenser outside the cylinder of the steam engine; and it is the principle applied when the pressure of an combustion motor is converted through a pump into pressure in a fluid Instead of producing the stream differential passively by moving the body in the fluid, it is possible to produce it actively by moving the fluid over the body. It is then possible to produce the potential by setting up a stream over one side of the body only. In this lies the reason for applying the hydrodynamical principle to marine purposes and for designing aeroplanes having other properties than those of the aeroplanes presently used The water around a ship at rest is in a hydrostatic equilibrium. The water pressure is equal to an energetic potential: Pa = N m2 = J m3. The static pressure at a given depth is constant. Any manipulation of static pressure in a fluid in the open must be indirect, by a change of the dynamical pressure. Technically, this takes place by introducing streams of water. In aeroplanes and airships, streams of air are used.

A stream or streams close to the vessel will disturb the equilibrium by reducing the local static pressure to a level calculable by Bernoulli's equation. This is equivalent to reducing the local force over the part of the surface of the vessel flushed by the streams, thus releasing the local potential of the fluid adjacent to the opposite part of the surface of the body.

In combination with the undisturbed pressure on the opposite side of the vessel, sustained streams will produce a differential of pressure relative to the potential This differential will release its potential by imparting a moment to the vessel.

This hydrodynamically produced moment is directed normally to the direction of the streams. It is useful for lift and propulsion.

When the body moves, the velocity over its opposite side, the one that is not flushed, will produce a reduced pressure and an accompanying force. As long as this pressure reduction is not as great as the ambient pressure, there will be a net force pushing the body.

The system here described is a simple apparatus which produces a technical effect by producing a pressure differential in the ambient fluid of a vessel, thus releasing a part of its potential and making it useful for lift or propulsion. It is not possible to refer to any published empirical or theoretical foundation for a calculation of its distribution of energy in the fluid, its forces, or its effects Among the references are works having a general relevance for hydrodynamical technology (B.S.Massey: Mechanics of fluids, 2'' edition, Van Nostrand Reinhold, London, 1970 and S W.Yuan Foundations of fluid mechanics, 2 edition, Prentice-Hall International, London, 1970).

Other relevant information will be found in textbooks of advanced studies, e.g marine hydrodynamics, rotating machines and thermodynamics

Prior Art

A known method and system for producing a pressure differential over a body by actively flushing one or more sides of the body, thereby establishing a low pressure region is disclosed in the European granted patent 1453726 in the name of Arne Kristiansen. This document explains that a pressure differential is created between the low pressure region and the opposite side of the body. The creation of propulsion on a body by the use of pressurised fluid from nozzles is known from US 2,108,652 to Coanda. From the apparatus described in the prior art document, T.Mehus: An experimental investigation into the shape of thrust-augmenting surfaces in conjunction with Coanda-deflected jet sheets, University of Toronto, 1965.

The effect of the flushing is a reduced pressure over a surface. In conjunction with the pressure over the opposite side of the body, this exposes it to a force, useful for lift. A sustained flushing produces a momentum, useful for propulsion, lift and manoeuvering. As seen above, this method is better than reactive devices for producing a force.

The air velocity difference over an aeroplane wing is 5-10 per cent. As long as the aeroplane velocity is above a threshold, the hydrodynamical potential of the velocity difference over the aeroplane wing will, as shown above, be more power efficient for producing lift than a reactive force can be A technically produced stream according to the method presented in European granted patent 1453726 will have its velocity limited to that of sound, even for rather slow aeroplanes. Thus, it will be possible to produce a greater specific lift.

Within this constraint, the lifting force will depend upon the power used and will permit competitive velocities of aeroplanes. By inclining the lifting body forward, it is used for propulsion and lift simultaneously. As the efficiency of jet engines is not remarkably high, propulsion by the horizontal vector of an inclined, flushed, lifling body will be more efficient This will permit slow and low-going aeroplanes. The advantages of manoeuvering by longitudinally and transversally inclinable bodies will be great, combining the versatility of the helicopter with the smaller engine installation needed for hydrodynamical lift and propulsion.

Friction and viscous resistance over the immersed surface are present at every contact between streams and surfaces, so are unavoidable in vessels.

Two other components of resistance are seen at towing a ship: an elevated pressure fore and a reduced pressure aft. By the use of a propeller, which draws water before accelerating it through its disk, the pressure around the stern is even more reduced, producing a force against the forward motion of the ship. Ahead, the bow wave signals an increased pressure, which is the energy needed in order to remove the water from the course of the ship.

These two components, the bow wave and the thrust deduction fraction, are currently seen as dynamical resistance bound to the propulsion of ships. Together, they consume 3 0-45 per ceni of the shaft power in most ships.

They may as well be seen as generic technical losses induced by the propeller.

Except a part of the reduced pressure aft, they are not bound to ship's propulsion as such The present state of ships' propulsion is one of sub-optimization, as the use of the reactive force of a propeller confers a series of constraints to the form and performance of ships. These are taken to be the conditions of ships' propulsion as such, cf the aforementioned literature The models for calculating power, velocity, and propellers' presumed optimal properties, are empirical and have a tenuous connection to physics. In order to predict the performance of a ship, a model of it is tried, and it has to be of a certain size in order for the impreciseness of the scaling factors to be overcome The propeller itself is a suboptimal reaction apparatus On the basis of physical functions, it has been possible to design an optimal propeller. It will not, however, reduce the two components of resistance bound to reactive propulsion (see Norwegian Patent number 143093).

The same relation as for aeroplanes between power applied and momentum (or first moment of mass) produced is valid for any body moved in a fluid or held against the acceleration of gravity. The hydrodynamically produced force is more power efficient than a reactive force; and it puts fewer constraints on design and performance of the vessels.

By flushing the bow, the force generated by the pressure differential between it and the longitudinal projection of the after ship will be higher than that obtainable by a propeller, since the surfaces involved are greater. This moving force is produced without an inherent loss of efficiency like that of a propeller, cf the turbulence of the propeller race.

By this technique, the ship is made into its own propulsive contrivance, leaving the water quiet behind.

A known way of producing streams over a ship's bow is to use nozzles. A technically more efficient way is to place the nozzles in the walls of two pressure vessels formed like tubes at or near the stagnation line of the surface of the body over which the pressure is to be reduced By the use of a string of nozzles in each tube, the streaming fluid is distributed over this surface. By making the tubes rotatable, the reactive force of the streams may be useful for braking and steering, which can be performed simultaneously. Braking will be possible even with large vessels On seagoing vessels, the two tubes are placed on the middle of the bow so as to distribute the streams over its curved surfaces. The position of tubes defines the leading edge of these two suction surfaces. The aft longitudinal projection of the ship defines the pressure side. Ships and ferries with a need for precise manoeuvring will have their stern formed like the bow. Tubes with nozzles are fitted correspondingly. Braking is performed by rotating the tubes ahead 900 or by flushing aft On aeroplanes, curved surfaces or movable bodies with one curved surface are flushed with air streams from tubes placed near their stagnation lines. In order to prevent the meeting stream from following the pressure side of a movable body, a plate is hinged to its leading edge and prevented from fluttering by the aid of shock absorbers.

The force generated by the pressure differential is useful for lift, propulsion, and manoeuvring. On aeroplanes, the last two are obtained by inclining the hinged bodies axially and transversally, thus using both the vertical and the horizontal components of the vector of the potential.

A ship may be interpreted as two wings put together, so that their suction sides form the bow and the sides of the ship, cj the drawing. The part of a ship corresponding to the pressure side of a wing will be the aft longitudinal projection of the ship.

The system is built on known technology. Centrifugal pumps are used at sea, thus water nozzles are the only new part of the propulsion system. Removing of particles from pump circuits is routine at sea. The system will be easily maintained.

There will be no risk of overloading motor or pump.

The system renders a high degree of security. Tubes and nozzles are less easily damaged than propellers are, as they are not protruding nor moving appendages It will be possible to isolate engines and pumps from the hull. This will impede the propagation of motor noise and vibrations in the ship.

There will be no vibrations like those generated in the stern by the pressure differences from the propeller The nozzles will not generate any low-frequency energy, but produce high-frequency sound only, which is of short range, as it is quickly damped in water.

It will be possible to reduce the quay erosion which is sometimes a problem in the ferry trade, as its possible to brake aft on arriving at the quay. At departure, the double-ended ferry is flushed at the fore end.

Since most ferry quays are open on one side, the use of catamarans will be possible.

These will have an advantageous relation between displacement, draught, capacity, and speed Two bow gates in each end will make possible the use of existing ferry quays.

Submarines may be directed downwards along a steeper angle than that now possible by the horizontal rudder alone.

As mentioned in-part above, a lowering of pressure in a fluid close to a curved surface is produced by means of a stream of fluid traversing the surface. The general relation between static and dynamic pressure was described by Bernoulli, though not its specific relation to curved surfaces.

Technically, this physical function is exploited in the wings of airplanes, which also take a part of their lift from the hydromechanical (or hydrokinetic) function of reactive force from the part of the airstream forced downwards by the angle of attack of the wing. The same is the case of screw propellers, of which, though1 most rely upon the reactive force of the acceleration of the stream for the greater part of their thrust Over a plane surface, a stream will be dissolved in turbulence. Transversely produced over a circular or otherwise curved semi-cylinder, the stream will, under a normal atmospheric pressure, be conserved through 81 , causing the pressure over its surface to drip as described in Bernoulli's and Euler's equations. This pressure drop on one side of a flushed body will release the pressure potential over the projection of its opposite side, thus imparting a moment to the body.

Fore-and-aft sails are more efficient than square sails, not foremost because of their higher aspect ratio, but because of their smaller radius of the wind trajectory over the sail's backside. This is seen especially when sailing close to the wind.

Already known, then, is the use of a curved surface for producing a moment higher than the reactive fluid-mechanical moment of momentum, cf the lifting force of an aeroplane being two or four times the reactive force of its jet engines. Producing the stream over a curved body like the upper side of an aeroplane wing or the backside of a screw propeller by moving it in the fluid of the atmosphere or the sea is known from technical history.

Instead of moving the curved body in the fluid, moving the fluid over the curved body has been proposed for aeroplane propulsion. It is known from an experiment related to VTOL-aeroplanes, from a security valve, from EP patent 1453726 and from the application for patent mentioned above in relation to Arne Kristiansen, both describing applications to ships and aeroplanes.

The possibility of producing the effect by moving the fluid has been proved with some of the known devices described The greater efficiency of the hydrodynamic function than that of the reactive mechanical (or kinetic) force is proved indirectly by its use in the wings of aeroplanes One aspect of the present invention is to utilise the aspects of the known methods and devices and to further augment the efficiency of the hydrodynamic function by optimizing the relation between the energy of the stream of fluid applied and the radius of the body flushed or blown, and by this means obtaining a higher moment, and thus a higher output of the energy used.

We have discovered that the moment and hence the force obtained, is inversely proportional to the radius of the semi-cylinder over which the stream of fluid is applied

Disclosure of the Invention

The various aspects of the invention are defined by the claims.

According to a first aspect of the present invention there is provided a method to propel a body, comprising the step of producing a pressure potential over a body by using a plurality of streams of pressunsed fluid flowing in a particular direction from fluid exit means over one or more surfaces of the body.

Preferably the plurality of streams of pressurised fluid flow in a unified direction from fluid exit means over one or more surfaces of the body.

Preferably, at the point where the stream reaches the curved surface, the direction of the stream flow will be at an angle substantially equal to or greater than 10 degrees relative to the tangent at the point where the stream reaches the curved surface.

Preferably, at the point where the stream reaches the curved surface, the direction of the stream flow will be at an angle substantially equal to or less than 30 degrees relative to the tangent at the point where the stream reaches the curved surface.

Preferably, at the point where the stream reaches the curved surface, the direction of the stream flow will be at an angle in the range of 10 to 30 degrees relative to the tangent at the point where the stream reaches the curved surface The surface of the body preferably comprises a plurality of curved sections, wherein each curved section is provided with a respective stream or streams of pressurised fluid flowing in the same general direction from the fluid exit means.

The surface of the body preferably comprises a plurality of curved sections, wherein each section is provided with a respective stream or streams of pressunsed fluid from fluid exit means.

Preferably, the power generated by the pressure potential over the body is distributed over a plurality of surfaces, each surface area being as small as technically optimum relative to the velocity of each respective applied stream of pressurised fluid.

The number of curved surfaces provided is preferably as high as feasibly achievable relative to the total power applied and/or relative to the efficiency of the exits means.

A method according to any one of the previous claims, wherein the direction of each stream is at a right angle to the axis of the respective curved surface.

Preferably, the angle between the stream or streams and the curved surface(s) is adjusted so that the respective streams are direct towards the respective surfaces at different angles, whereby to propel, to steer and to manoeuvre the body.

Each stream is preferably directed into at least one channel defined by a curved surface of the object and a guard section.

Preferably, the channel is an open sided channel defined by the curved surface of the object and an open sided curved guard section.

The channel(s) preferably extend across an arc of substantially 120 degrees.

The stream within the channel preferably has a lower fluid pressure adjacent the radially inner surface of the guard section due than the pressure adjacent the radially outer surface of the curved surface due to the difference in the respective velocities at the respective surfaces.

According to a second aspect of the present invention there is provided a system to propel, steer and manoeuvre a body, including means of producing a pressure potential over a body by using a stream or streams of pressurised fluid from fluid exit means over one or more surfaces of the body Preferably, in use the plurality of streams of pressurised fluid flow in a unified direction from fluid exit means over one or more surfaces of the body.

Preferably, at the point where the stream reaches the curved surface, the direction of the S stream flow will be at an angle in the range of 10 to 30 degrees relative to the tangent at the point where the stream reaches the curved surface.

The surface of the body preferably comprises a plurality of curved sections, wherein each section is provided with a respective stream or streams of pressurised fluid from fluid exit means Preferably for the method, the system and the technical application of the present invention, various functions may be subject to several constraints not mentioned in the known publications, such as but not limited to: 1. Each flushed or blown part of the body should preferably have a single-curved, semi-cylindrical form.

2. Its surface should preferably be produced by a directrix as part of a conic section 3 Since an inverse relation exists between the obtained moment and the radius of the surface, a given power should preferably be distributed over a number of surfaces, each as small as technically possible down to a practicable optimum relative to the velocity of the applied stream.

4. The number of semi-cylindrical surfaces should be preferably as great as possible relative to the total power applied and to the nozzle efficiency 5. The stream of fluid should be preferably directed toward the surface at a right angle to the axis of each semi-cylinder.

6. The stream should have preferably an angle of attack relative to the surface In a first embodiment of the present invention the application is a hull of a ship, the two halves of the bow section of the hull will preferably be divided into a number of separately flushed, semi-cylindrical, vertical parts. It shall be appreciated that the number of divided sections may vary depending on the characteristics of a specific vessel.

In a second embodiment of the present invention the application is curved lifting surfaces of an aeroplane, which should preferably have a number of flushed wings, or separate parts of wings, each having a relatively small upper side radius.

Brief Description of the Drawings

Embodiments of the present in the form of a vessel are illustrated in the attached figures, by way of example only, in which: Figures 1 is an isometric view of a first embodiment of the present invention and shows a half section of a hull of a water borne vessel; Figure 2 shows a plan view of the hull of the water borne vessel shown on figure 1, Figure 3 is a plan view of a second embodiment of the present invention and shows a cross section of a hull of a water borne vessel; Figure 4 is a plan view of a third embodiment of the present invention and shows a cross section of a hull of a water borne vessel; Figure 5 is a detailed plan view of a nozzle feature of the hull in figure 4, Figure 6 is a detailed front elevation view of a tube comprising a series of nozzles of the hull in figure 4; and Figure 7 is an embodiment of the nozzle feature.

With reference to the figures, a first embodiment of the present invention comprises a water borne vessel 2 comprising a hull 4 and means for producing a pressure potential over the bow portion 6 of the hull 4 by using streams of pressurised fluid flushed over the bow portion 6. The means for producing a pressure potential comprises a fluid pump (not shown) and a number of tubes 8 each formed with exit ports in the form of a series of nozzles 10. The nozzles may alternatively be a series of holes, or slits or any other suitable design. The bow portion 6 is formed from a plurality of singly-curved, semi-cylindrical sections 12. The tubes 8 are each disposed at leading edge of each respective section 12. In use, pressurised fluid is discharged as streams from nozzles 10, holes in one or more of the surfaces of the sections 12 from the respective leading edge(s), establishing a pressure potential over sections 12 between the leading and the trailing edges and hence over the bow 6. The pressurised fluid forms two effective flow streams 16, 17 over the bow section 6 of the hull 4. Each flow stream 16, 17 travels over a respective half section of the bow 6. The two flow streams are formed by an accumulation of the individual pressurised fluid that is discharged as streams from nozzles 10. The pressure potential over the hull 4 causes the vessel 2 to have a velocity indirection 14.

Each flushed or blown part of the sections 12 should preferably have a single-curved, semi-cylindrical form. The surface the sections 12 should preferably be produced by a directrix as part of a conic section. An inverse relation exists between the obtained moment and the radius of the surface, and a given power should preferably be distributed over a number of surfaces of the section 12, each as small as technically possible down to a practicable optimum relative to the velocity of the applied stream from the nozzles 10. The number of semi-cylindrical sections 12 should be preferably as great as possible relative to the total power applied and to the efficiency of the nozzle 10. The stream of fluid should be preferably directed toward the surface at a right angle to the axis of each semi-cylinder of the sections 12. The stream should have preferably an angle of attack relative to the surface of the sections 12. in order to avoid Kármán wobbling, the following edge of a flushed or blown body (e.g. a ship, or a wing) preferably should not be sharp but cut to a certain breadth At the point where the stream reaches the curved surfaces 12, the direction of the stream flow will be at an angle in the range of 10 to 30 degrees relative to the tangent at the point where the stream reaches the curved surfaces 12.

With reference to Figure 3 there is shown a second embodiment of the invention, wherein the tubes 8 that provide the streams of fluid are located between two adjacent curved surfaces 20. Each fluid stream from the respective tubes 8 exits through a longitudinal slot 22 formed by the tail end portion of one curved surface and the front portion of an adjacent curved surface The front of the bow 6 is provided with a twin curved structure 20'. The twin curved structure 20' is formed by two curved sections meeting at a point 21. Each curved section of the structure 20' has a curvature of about 30 degrees. The curved sections 20, 20' extend the substantial height of the bow 6. The run of the upstream streams of flow 16 on the port side of the hull will combine with each of the consecutive flows 16 of the respective downstream sections and the runof the upstream streams of flow 17 on the starboard side of the hull will combine with each of the consecutive flows 17 of the respective downstream sections. The arrangement of the tubes 8 within the longitudinal slots 22 helps to provide non-turbulent laminar fluid stream flows over the surface of the hull 4 With reference to Figures 4, 5 and 6, there is shown a third embodiment of the invention, wherein each of the flow streams 16, 17 are provided with a series of guard sections 24 extending from respective nozzles 10 and substantially parallel to the curved surfaces 12. The guard sections 24 are formed by opened tubular sections. The radius of each guard section 24 increases from a smaller radius at the open end 26 adjacent the respective nozzle 10 to a larger radius at the opposite end 28 of the guard 24. The guards 24 help to maintain a non-turbulent laminar fluid flow over the surface of the respective curved sections 20 and form an open barrier between the flow streams 16, 17 and the outer mass of liquid through which the hull 4 passes. The guard sections 24 are fixed to the hull 4 in such a way that they are held distant from the hull 4. The two side edges of the guard sections 24 are held distant from the hull 4 such that there is a gap between the guard section edges and the hull 4.

Figure 5 shows a detailed view of one of the tubes 8. The nozzle 10 directs the stream of flow towards the curved section 20 at an angle of 9. The angle 0 may be in the range from ten degrees to thirty degrees relative to the tangent at the point where the stream reaches the curved surface. The angle, at which the steam is directed towards the curved surface, being within the range often to thirty degrees helps to provide an improved laminar flow characteristic and a more efficient production of a pressure differential. The use of the guards will produce an additional propulsion effect on the hull due to the resultant force F of the unbalanced pressures on the radially outer internal surfaces of the guards.

With reference to Figure 7, there is shown a further embodiment of the invention wherein the tubes 8 are moveable in an arc 31 above the surface of the semi-circular section 12. This feature allows the point of contact of the streams of flows 16, 17 to be adjusted over the surface of the section 12.

It shall be appreciated that the above described apparatus and the method of its use may be suitably adapted for the producing a pressure potential over one or more curved sections of an aeroplane in order to produce a lifting force

Claims

A method to propel a body, comprising the step of producing a pressure potential over a body by using a plurality of streams of pressurised fluid flowing in a particular direction from fluid exit means over one or more surfaces of the body.
2. A method according to claim 1, wherein the plurality of streams of pressurised fluid flow in a unified direction from fluid exit means over one or more surfaces of the body
3 A method according to claim I or claim 2, wherein at the point where each stream reaches the curved surface, the direction of the stream flow will be at an angle substantially equal to or greater than 10 degrees relative to the tangent at the point where the stream reaches the curved surface.
4. A method according to claim 1 or claim 2, wherein at the point where the stream reaches the curved surface, the direction of the stream flow will be at an angle substantially equal to or less than 30 degrees relative to the tangent at the point where the stream reaches the curved surface
5. A method according to claim 1 or claim 2, wherein at the point where the stream reaches the curved surface, the direction of the stream flow will be at an angle in the range of 10 to 30 degrees relative to the tangent at the point where the stream reaches the curved surface
6. A method according to any one of claims I to 5, wherein the surface of the body comprises a plurality of curved sections, wherein each curved section is provided with a respective stream or streams of pressurised fluid flowing in the same general direction from the fluid exit means.
7. A method according to claim 6, wherein the power generated by the pressure potential over the body is distributed over a plurality of surfaces, each surface area being as small as technically optimal relative to the velocity of each respective applied stream of pressurised fluid.
8. A method according to claim 6 or claim 7, wherein the number of curved surfaces provided is as high as feasibly achievable relative to the total power applied and/or relative to the efficiency of the exits means.
9. A method according to any one of the previous claims, wherein the direction of each stream is at a right angle to the axis of the respective curved surface.
10. A method according to an one of the previous claims, wherein the angle between the stream or streams and the curved surface(s) is adjusted so that the respective streams are direct towards the respective surfaces at different angles, whereby to propel, to steer and to manoeuvre the body.
11. A method according to an one of the previous claims, wherein each stream is directed into at least one channel defined by a curved surface of the object and a guard section.
12 A method according to claim 11, wherein the channel is an open sided channel defined by the curved surface of the object and an open sided curved guard section
13. A method according to either claim 11 or claim 12, wherein the channel(s) extend across an arc of substantially 120 degrees.
14. A method according to any one of claims 11 to 13, wherein the stream within the channel has a lower fluid pressure adjacent the radially inner surface of the guard section due than the pressure adjacent the radially outer surface of the curved surface due to the difference in the respective velocities at the respective surfaces.
15. A system to propel a body, comprising means for producing a pressure potential over a body by using a plurality of streams of pressurised fluid flowing in a particular direction from fluid exit means over one or more irfaces of the body.
16. A system according to claim 15, wherein, in use the plurality of streams of pressurised fluid flow in a unified direction from fluid exit means over one or more surfaces of the body.
17 A system according to claim 15 or claim 16, wherein at the point where the stream reaches the curved surface, the direction of the stream flow will be at an angle substantially equal to or greater than 10 degrees relative to the tangent at the point where the stream reaches the curved surface.
18. A system according to claim 15 or claim 16, wherein at the point where the stream reaches the curved surface, the direction of the stream flow will be at an angle substantially equal to or less than 30 degrees relative to the tangent at the point where the stream reaches the curved surface.
19. A system according to any one of claims 15 to 18, wherein at the point where the stream reaches the curved surface, the direction of the stream flow will be at an angle in the range of 10 to 30 degrees relative to the tangent at the point where the stream reaches the curved surface.
20. A system according to any one of claims 15 to 19, wherein the surface of the body comprises a plurality of curved sections, wherein each section is provided with a respective stream or streams of pressurised fluid from fluid exit means.
21 A system according to an one of the previous claims 15 to 20, wherein the angle between the stream or streams and the curved surface(s) is adjusted so that the respective streams are direct towards the respective surfaces at different angles, whereby to propel, to steer and to manoeuvre the body.
22. A system according to any one of claims 13 to 21, characterized in that each curved surface is generally formed by a plurality of curved sections arranged side by side each other.

23 A system according to claim 22, characterized in that each curved section comprises a means for producing a pressure potential over the curved surface by using a *:::. 15 stream or streams of pressurised fluid * . S...

S

* S.. *. * .

S I..

S

S

**SSSS * S

SS SS * . S

S S

22. A system according to an one of the previous claims 15 to 21, wherein each stream is directed between at least one channel defined by a curved surface of the object and a guard section.

23. A system according to claim 22, wherein the channel is an open sided channel defined by the curved surface of the object and an open sided curved guard section.

24. A system according to either claim 22 or claim 23, wherein the channel(s) extend across an arc of substantially 120 degrees.

25. A system according to any one of claims 22 to 24, wherein the stream within the channel has a lower fluid pressure adjacent the radially inner surface of the guard section due than the pressure adjacent the radially outer surface of the curved surface due to the difference in the respective velocities at the respective surfaces.

26 A system according to any one of claims 15 to 25, wherein each curved surface is generally formed by a plurality of curved sections arranged side by side each other.

27. A system according to claim 26, wherein each curved section comprises a means for producing a pressure potential over the curved surface by using a stream or streams of presswised fluid. a ic

1. A method to propel a body, comprising the step of producing a pressure potential over a body by using a plurality of streams of pressurised fluid flowing in a particular direction from fluid exit means over one or more surfaces of the body, characterized in that each stream is directed into at least one open sided channel defined by a curved surface of the object and an open sided curved guard section.

2. A method according to claim 1, characterized in that the plurality of streams of pressurised fluid flow in a unified direction from fluid exit means over one or more surfaces of the body.

3. A method according to claim I or claim 2, characterized in that the point where each stream reaches the curved surface, the direction of the stream flow will be at an angle substantially equal to or greater than 10 degrees relative to the tangent at the point where the stream reaches the curved surface * 4. A method according to claim I or claim 2, characterized in that the point where *. 15 the stream reaches the curved surface, the direction of the stream flow will be at an angle * * substantially equal to or less than 30 degrees relative to the tangent at the point where the stream reaches the curved surface.

S

* .*S** 5. A method according to claim I or claim 2, characterized in that the point where * the stream reaches the curved surface, the direction of the stream flow will be at an angle in the range of 10 to 30 degrees relative to the tangent at the point where the stream reaches the curved surface. S. **

: * 6. A method according to any one of claims Ito 5, characterized in that the surface of the body comprises a plurality of curved sections, wherein each curved section is provided with a respective stream or streams of pressurised fluid flowing in the same general direction from the fluid exit means.

7. A method according to claim 6, characterized in that the power generated by the pressure potential over the body is distributed over a plurality of surfaces, each surface area being as small as technically optimal relative to the velocity of each respective applied stream of pressurised fluid.

8. A method according to claim 6 or claim 7, characterized in that the number of curved surfaces provided is as high as feasibly achievable relative to the total power applied and/or relative to the efficiency of the exits means.

9. A method according to any one of the previous claims, characterized in that the direction of each stream is at a right angle to the axis of the respective curved surface.

C

10. A method according to an one of the previous claims, characterized in that the angle between the stream or streams and the curved surface(s) is adjusted so that the respective streams are direct towards the respective surfaces at different angles, whereby to propel, to steer and to manoeuvre the body.

11. A method according to claim 1, characterized in that the channel(s) extend across an arc of substantially 120 degrees.

12. A method according to claim 11, characterized in that the stream within the channel has a lower fluid pressure adjacent the radially inner surface of the guard section due than the pressure adjacent the radially outer surface of the curved surface due to the difference in the respective velocities at the respective surfaces.

13. A system to propel a body, comprising means for producing a pressure potential over a body by using a plurality of streams of pressurised fluid flowing in a particular direction from fluid exit means over one or more surfaces of the body, characterized in that each stream is directed between at least one open sided channel defined by a curved surface of the object and an open sided curved guard section. * **

14. A system according to claim 13, characterized in that, in use the plurality of streams of pressurised fluid flow in a unified direction from fluid exit means over one or more surfaces of the body.

* .**** * . 15. A system according to claim 13 or claim 14, characterized in that the point where :" 20 the stream reaches the curved surface, the direction of the stream flow will be at an angle substantially equal to or greater than 10 degrees relative to the tangent at the point where * the stream reaches the curved surface. ** **

* 16 A system according to claim 13 or claim 14, characterized in that the point where the stream reaches the curved surface, the direction of the stream flow will be at an angle substantially equal to or less than 30 degrees relative to the tangent at the point where the stream reaches the curved surface.

17 A system according to any one of claims 13 to 16, characterized in that the point where the stream reaches the curved surface, the direction of the stream flow will be at an angle in the range of 10 to 30 degrees relative to the tangent at the point where the stream reaches the curved surface.

18. A system according to any one of claims 13 to 17, characterized in that the surface of the body comprises a plurality of curved sections, wherein each section is provided with a respective stream or streams of pressurised fluid from fluid exit means.

19. A system according to an one of the previous claims 13 to 18, characterized in that the angle between the stream or streams and the curved surface(s) is adjusted so that ( the respective streams are direct towards the respective surfaces at different angles, whereby to propel, to steer and to manoeuvre the body.

20. A system according to claim 13, characterized in that the channel(s) extend across an arc of substantially 120 degrees.

21 A system according to any one of claims 13 to 20, characterized in that the stream within the channel has a lower fluid pressure adjacent the radially inner surface of the guard section due than the pressure adjacent the radially outer surface of the curved surface due to the difference in the respective velocities at the respective surfaces.