DEVICE FOR REDUCING THE ENTRY OF FLUID INTO A TUNNEL

Abstract

The device for controlling the flow of fluid passing in front of an orifice or cavity produced in the hull of a vessel has at least one deflector (5) rigidly fixed to the wall of the vessel upstream of the orifice or cavity. This deflector has a planar inner face directed towards the hull of the vessel and a curved outer face which is highly convex upstream and tapered downstream.

Description

The present invention relates to a device greatly reducing, or even avoiding, the entry of a fluid, generally a liquid, into a tunnel. In particular, the invention relates to a device enabling—during the normal forwards movement of a vessel—the entry of the water into the tunnel of a bow thruster of this vessel to be greatly reduced or avoided. The presence of a housing, of a recess and, naturally, of a bow thruster tunnel greatly disrupts the normal movement of boats and ships equipped therewith, because this interruption in the hull of the vessel causes eddies, turbulence and a significant drag, reducing the speed of movement of the vessel and absorbing a large amount of the propulsion power.

In order to avoid these disadvantages it has been proposed to close off—during normal movement of the vessel—the orifices in the hull which give access to the transverse tunnel in which the bow thruster/thrusters is/are housed, using sliding or pivoting shutters controlled by motors. These systems are not only expensive but are also very delicate because their correct operation can be hampered by seaweed and rubbish of all kinds, and they thus require frequent and difficult maintenance.

The object of the present invention is to propose a device for controlling the flow of fluid passing in front of one or more orifices in the hull of a vessel, in particular at the orifices giving access to the transverse tunnel enclosing the bow thruster/thrusters, in order to reduce the volume of fluid which flows along the hull of the vessel during its normal movement entering or leaving this tunnel in order to greatly reduce or avoid any eddying, drag or turbulence phenomena, which is simple, strong and requires only little or no maintenance. An object of the present invention is the production of such a device for controlling the flow of fluid passing in front of an orifice or cavity in the hull of a vessel.

The object of the present invention is a device for controlling the fluid passing in front of the orifices in the hull of a vessel, in particular those giving access to the transverse tunnel enclosing the bow thruster/thrusters, tending to obviate the disadvantages of the above-mentioned existing devices and permitting the object stated above to be achieved. This device for controlling the flow of fluid passing in front of an orifice or cavity in the hull of a vessel is characterised by the features listed in claim 1.

The attached drawing illustrates—schematically and by way of example—an embodiment of the device in accordance with the invention.

FIG. 1 is a schematic vertical partial cross-sectional view perpendicular to the longitudinal axis of the vessel, passing through the axis of the bow thruster tunnel.

FIG. 2 is a partial view of the hull of the vessel in line with the arrow A of FIG. 1.

FIG. 3 is a cross-section along the line III-III of FIG. 2.

FIG. 4 is a cross-sectional detail on a larger scale showing the device.

FIG. 5 illustrates on a larger scale a transverse cross-sectional view of the shapes forming a deflector.

The attached drawing shows very schematically the hull 1 of a vessel through which a bow tunnel 2 passes in the transverse direction, in which tunnel one or more bow thrusters 3 are mounted. At its ends this bow tunnel 2 has orifices 4 passing through the hull 1 of the vessel and issuing entirely into the water. The cross-section of this bow tunnel 2 is generally circular and its ends can be flared. The bow tunnel 2 is filled with the fluid surrounding the hull 1 of the vessel. When the vessel manoeuvres in order to dock, for example, or in order to leave its position at the quay, the bow thruster 3 is started up, which causes a displacement in the fluid inside the bow tunnel transverse to the longitudinal axis of the vessel, which makes it possible to move this vessel in order to bring it closer to, or move it further away from, the mooring quay.

When the vessel is sailing normally the bow thruster is stopped and, if no provision is made otherwise, turbulence is created in the proximity of the openings or orifices 4 of the bow tunnel, turbulence which creates a significant amount of drag. This drag reduces the speed of the vessel and causes excess consumption of fuel in propelling the vessel.

The object of the device in accordance with the invention is to control the flow of fluid passing in front of the orifices 4 of the bow tunnel 2 in order to reduce or avoid entry of the fluid into this tunnel 2 and reduce or eliminate any turbulence and drag owing to the flow of the fluid in front of these orifices 4.

This device for controlling the flow of the fluid in front of the orifices of the bow tunnel 4 of the hull 1 of a vessel has at least one deflector 5 rigidly fixed to the hull 1 of the vessel upstream of the orifice 4 and extending over a distance greater than or at least equal to the diameter of this orifice 4. This deflector 5 has, in cross-section, a planar inner face 6 disposed facing the hull 1 of the vessel and a convex outer face 7. The thickness of the deflectors increases greatly in the upstream part 8 to then decrease slowly in the direction of the downstream part and to terminate in a strongly tapered manner forming a downstream edge 9.

This deflector 5 is rigidly fixed to the hull 1 of the vessel with the aid of supports 10 welded, bolted or fixed in any other manner to the hull 1 of the vessel.

The device preferably has two deflectors 5 disposed on either side of the orifice 4 of the bow tunnel 2. In this case the distance L separating the downstream edge 9 of the upstream deflector 5 from the upstream edge of the downstream deflector 5a is substantially equal to, slightly less or greater than, the diameter of the orifice 4 of the bow tunnel 2.

The inner planar surface 6 of the deflectors 5 and 5a is substantially parallel to the hull 1 of the vessel. In one variation the inner face 6 of the upstream deflector 5 forms a slight angle with the surface of the hull 1 of the vessel so that its downstream edge 9 is further away from this hull than its front edge is. In this case the front edge of the downstream deflector 5a is closer to the hull 1 of the vessel than the downstream edge 9 of this downstream deflector 5a is.

Thus the passage produced between the upstream deflector 5 and the hull increases in the direction of the orifice 4 and narrows for the downstream deflector 5a.

In the case where the device for controlling the flow of fluid has only one deflector, the downstream deflector 5a is omitted.

If a bow orifice has a diameter of the order of 1 m, the length 1 of the deflector/deflectors 5 would be of the order of 1.1 m, its depth P of the order of 15 to 40 cm and its thickness e of the order of 15 to 30 mm.

When the device has two deflectors, one 5 upstream and the other 5a downstream, the depth P of the upstream deflector is preferably greater than that of the downstream deflector.

When the vessel is moving forward in the direction of the arrow B, from a certain speed which is lower than the cruising speed of the vessel, the flow of fluid between the deflector/deflectors 5 and the hull 1 of the vessel is controlled and modified. It becomes uniform and controlled and forms a liquid wall in front of the orifice 4 of the bow tunnel, preventing the fluid from entering it or at least greatly reducing the entrance of fluid into the said orifice. This makes it possible to reduce or eliminate turbulence in the fluid at this location and to reduce the drag of the vessel very substantially.

The device of the invention is simple, inexpensive, fixed to the hull of the vessel and requires only a little maintenance while making it possible to avoid drag and turbulence in the fluid owing to the presence of the bow tunnel orifices and thus to reduce the resistance to the forward movement of the vessel.

The device described can be used to control the flow of fluid passing in front of any type of orifice or cavity formed in the hull of a vessel.

Claims

1. Device for controlling the flow of fluid passing in front of an orifice or cavity produced in the hull of a vessel, characterised in that it has at least one deflector (5) rigidly fixed to the wall of the vessel upstream of the orifice or cavity; in that this deflector has a planar inner face directed towards the hull of the vessel and a curved outer face which is highly convex upstream and tapered downstream.

2. Device as claimed in claim 1, characterised in that it has a second deflector of a similar shape to the first, disposed downstream of the orifice or cavity.

3. Device as claimed in claim 1, characterised in that the planar inner face of the deflector is parallel to the hull of the vessel.

4. Device as claimed in claim 1, characterised in that the planar inner face of the deflector forms an angle with the hull of the vessel so as to create a space between this face and the hull which narrows or increases in the direction of the orifice or cavity.

5. Device as claimed in claim 2, characterised in that the distance separating the upstream and downstream deflectors is substantially equal to the diameter of the orifice or cavity.

6. Device as claimed in claim 2, characterised in that the planar inner face of the deflector is parallel to the hull of the vessel.

7. Device as claimed in claim 2, characterised in that the planar inner face of the deflector forms an angle with the hull of the vessel so as to create a space between this face and the hull which narrows or increases in the direction of the orifice or cavity.