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(11) | EP 2 182 120 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Overflow dam and method for maintaining a water level at one side of the dam |
| (57) An overflow dam for maintaining a first water level at a first side of the dam, said
first water level being higher than the second water level at the second side of the
dam, wherein water from the first side of the dam may flow over the dam to the second
side of the dam, wherein said dam comprises an element extending at the second side
of the dam, said element having an upper surface which is at approximately the same
height as said second water level, such, that said water flowing over said dam lands
on said element.
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[0001] The invention relates to an overflow dam for maintaining a first water level at a first side of the dam, said first water level being higher than the second water level at the second side of the dam, wherein water from the first side of the dam may flow over the dam to the second side of the dam.
[0002] It is noted that an overflow dam is to be understood as any contracted waterway, such as a weir, a lock, a sluice or an abutment for a bridge over a river. A sill in a hole of a dike burst is likewise to be understood as an overflow dam.
[0003] An overflow dam is generally known. A disadvantage of the known dams is that the water flow pattern downstream from the dam is such that people or animals being in the direct hydraulic sphere of influence of the dam have a high risk of getting drown.
[0004] It is an object of the invention to provide a dam that reduces the risk of people or animals getting drown in the direct hydraulic sphere of influence of the dam. Further objects of the invention are that the dam is reliable and/or cheap and/or easy to install and/or adaptable and/or functions automatically.
[0005] In order to accomplish the above object, an overflow dam of the kind referred to in the introduction is characterized in that said dam comprises an element extending at the second side of the dam, said element having an upper surface which is at substantially, or approximately, the same height as said second water level, such, that said water flowing over said dam lands on said element. An advantage of such an element is that it affects the water flow pattern downstream from the dam, also known as a hydraulic jump, such, that people or animals being present in the direct hydraulic sphere of influence of the dam can easily leave this area, thereby reducing the risk of getting drown.
[0006] In a preferred embodiment said dam comprises attaching means for attaching said element to said second side of the overflow dam. Said attaching means have the advantage that the element will remain at the dam in a fixed position with respect to the stream direction.
[0007] In a further preferred embodiment said dam is a hingeable dam, wherein said attaching means comprise a hinge for hingeably attaching said element to said second side of the dam, such, that said element is hingeable around the longitudinal axis of said dam. Such a hingeable dam is movable between a vertical position and a more horizontal position and because of the hingeable attachment of said element to said dam, said element will remain in a more or less horizontal position for every position of the dam, such, that the element affects the flow pattern most effectively.
[0008] In a further preferred embodiment said attaching means comprise guiding means for guidingly attaching said element to said second side of the dam, such, that said element is movable in a vertical direction for adapting to said second water level. An advantage of an element that adapts to said second water level is that said upper surface of said element will remain at approximately the same height as said second water level, even when this level varies in time.
[0009] Preferably, said element has a buoyancy, such, that in accordance with the pressure of said water flowing over said dam and landing onto said element and in accordance with said second water level, said upper surface of said element is maintained at approximately the same height as said second water level. An advantage thereof is that the element will easily and/or automatically remain at the same height as said second water level.
[0010] In another preferred embodiment sealing means are provided between said element and said second side of said dam. The sealing means seal a free space between the element and the dam, such, that limbs or the like of people or animals that are in the proximity of the dam, cannot get stuck between the dam and the element. Also said slab prevents water from flowing through the element and the dam, thereby further reducing the hydraulic jump at the downstream side of the element. Preferably, said sealing means comprise a neoprene slab.
[0011] In another preferred embodiment said element is shaped as a plate. An element in the form of a plate has the advantage that is light compared to the size of its upper surface, such that the element will easily adapt to the height of the second water level.
[0012] The invention also relates to a method for maintaining a first water level at a first side of an overflow dam, said first water level being higher than a second water level at the second side of the dam, wherein water from the first side of the dam flows over the dam to the second side of the dam.
[0013] The invention will now be explained in more detail with reference to figures illustrated in a drawing, wherein:
- figure 1 is a cross section of an overflow dam;
- figure 2 is a cross section of an overflow dam according to a first embodiment;
- figure 3 is a cross section of an overflow dam according to a second embodiment;
- figure 4 is a top view of an overflow dam according to a third embodiment; and
- figure 5 is a cross section of the dam of figure 4.
[0014] In figure 1 an overflow dam 1 according to the prior art is shown. Upstream of the dam 1, a first water level 2 is maintained, which first water level 2 is higher than a second water level 3 at the downstream side of the dam 1. Downstream flowing water flows over the dam 1 to the downstream side of the dam 1 in a vertical direction, as is shown by flow lines 4. When the water hits the bottom 5 of the basin or the river bed, the water is deflected horizontally along the bottom 5 until the water is deflected upwards by the stagnant water 6. This upward deflection is stronger when a stream breaker 7 is used. After being deflected upwards, the water splits and flows both upstream 8 and downstream 9 of the stagnant water 6. As is shown by flow lines 4, this creates a circulating flow of water at the upstream side 8 of the stagnant water 6, which flow pattern is called a submerged hydraulic jump. A person or an animal ending up in this circulating flow cannot easily escape and may drown.
[0015] In figure 2 an overflow dam 1 in the form of a movable weir is shown. A plate 10 extends at the downstream side of the dam 1, such, that the upper surface of the plate 10 is at approximately the same height as said second water level 3. As is shown in the area 11 above the plate 10, the water flowing over the dam 1 lands on the plate 10 and is deflected in the horizontal direction over the plate 10. As is shown by flow lines 4, a circulating water flow is thus created at the downstream side 12 of the plate 10, which circulating flow is weaker than the circulating flow occurring at the dam of figure 1. This flow pattern is a normal hydraulic jump of a harmless kind, and any person or animal ending up there can easily or even automatically escape from the hydraulic jump to the water that is flowing away further upstream 13. The plate 10 is preferably dimensioned such that substantially all the water flowing over the dam 1 will land on the plate 10.
[0016] As is shown in figure 2, plate 10 is hingeably connected to dam 1 by means of a hinge 14. This is advantageously in this embodiment in which the dam 1 has the form of a hingeable weir, which is attached at the bottom of the weir by a hinge, and which is movable between a vertical position and a more horizontal position, because the plate will then remain in a substantially horizontal position even when the dam 1 is moved in either direction towards or from the bottom 5.
[0017] In figure 3 an overflow dam 1 is shown with a plateau 15 extending at the downstream side of the dam 1. As is clear from figure 3, the upper surface of the plateau 15 is at approximately the same height as said second water level 3. The water will flow in substantially the same manner as described above for the dam of figure 2, as is shown by flow lines 4. Such a plateau 15 can be conveniently used for dams that have a more or less constant second water level 3 at their downstream sides. Also, multiple plateaus 15 can be used depending on the geometrical structure of the dam 1. Preferably, said plateau 15 is a fixed construction.
[0018] In figures 4 and 5 an overflow dam 1 in the form of a hingeable weir is shown. A plate 10 extends at the downstream side of the dam 1, such, that the upper surface of the plate 10 is at approximately the same height as said second water level 3. As shown in figures 4 and 5, the dam 1 comprises guiding cables or guiding rods 16 that are vertically mounted at both sides of the downstream side of dam 1, such, that the guiding rods 16 are separated from each other by a horizontal distance. Plate 10 is hingeably attached to the guiding rods 16 by use of hinge 14, which is advantageous because dam 1 is a hingeable weir as described before. Hinge 14 can be a rubber strip. Plate 10 is freely movable in a vertical direction over the guiding rods 16, so that the height of plate 10 can be adapted to said second water level 3, in accordance with both the upstream water level 2 as the downstream water level 3. This is advantageous when said second water level 3 varies in time. Preferably, plate 10 has a buoyancy, such, that in accordance with the pressure of said water flowing over said dam 1 and landing onto the plate 10 and in accordance with said second water level 3, said upper surface of said plate 10 is maintained at approximately the same height as said second water level 3. In this manner the plate 10 will easily and automatically adapt to the second water level 3. The buoyancy of the plate 10 can be easily adapted to requirements by choosing a suitable material and/or volume. Preferably, the density of said plate 10 is as low as possible, so that the upper surface of plate 10 will easily remain at the second water level 3. Even more preferably, said plate 10 is made of PE, and also preferably the plate has a hollow core.
[0019] Preferably, a neoprene slab 17 is provided between the plate 10 and the dam 1 so that the free space between the plate 10 and dam 1 is sealed, such, that limbs or the like of a person or animal that is in the proximity of the dam 1, cannot get stuck between the dam 1 and the plate 10. The guiding rods 16 can be provided in this slab 17.
[0021] Preferred embodiments eliminate the risk of drowning at weirs. Preferred embodiments relate to a device for protecting a weir such that the risk of humans and/or animals being drowned upon falling into the water within the direct hydraulic range of influence of the weir is eliminated. The term 'weir' as used herein is understood to mean all contracted waterways. Examples of weirs are: a dam, a lock, an abutment for a bridge across a river. Likewise, a threshold in a hole of a dike breach can be regarded as a weir.
[0022] Such a device is of importance to humans and animals that are exposed to the risk of drowning upon falling into the water within the range of influence of a weir.
[0024] Another object of preferred embodiments is to provide such a device which meets high reliability standards, which is inexpensive to acquire, easy to install, self-adjusting and which functions fully automatically.
[0025] To realise the above and other objects, preferred embodiments provide a device which influences a so-called (submerged) hydraulic jump, also known as "surface eddy" or "roller" in the literature, caused by the transition from supercritical flow to sub-critical flow, such that it eliminates the risk of drowning for humans and/or animals that have fallen into the water, said device comprising: a flow element which is present, possibly floating, in the flow behind (downstream of) the weir; possible floating means, which give the flow element a degree of buoyancy corresponding to the hydraulic boundary conditions of the weir; a fastening construction, which keeps the flow element correctly positioned relative to the weir and the current hydraulic flow profile; means which prevent any injuries sustained by humans or animals as a result of getting trapped or other injuries sustained as a result of coming into contact with the flow element and/or the weir.
[0026] In one embodiment of a device, a floating plate is attached to an overflow-type dam, which plate forms an additional "step" as it were. Said additional "step" is positioned approximately at the level of the downstream water level. The water that flows over the dam first lands on said "step", resulting in a supercritical flow in horizontal direction. Said supercritical flow flows from the "step", resulting in a hydraulic jump (surface eddy) of a harmless kind.
[0027] A device according to the embodiment automatically adjusts itself to the varying water levels, both upstream and downstream, within the design criteria that need to be defined for each individual version.
[0028] A device according to the embodiment can be adapted to any weir dam by using the correct dimensions.
[0030] A device according to the embodiment is to that end provided with a fastening construction which fixes the flow element relative to the dam in the direction of flow but which provides the necessary freedom of movement in the other directions so as to enable the element to adjust itself automatically to the prevailing conditions. The fastening construction is to that end built up of, for example, at least two guide cables or guide rods, which are fixed to the dam on either side thereof and over which one guide for each guide cable or guide rod, which guide forms part of the flow element, can freely move upwards or downwards.
[0031] A device according to the embodiment can be adapted as regards the required buoyancy through a suitable selection of the materials and the volume of the element. The buoyancy must correspond to the pressure of the falling water.
[0032] For protection reasons, a device according to the embodiment is provided with, for example, a neoprene slab between the flow element and the dam gate, which closes off the free space in such a manner that limbs or other body parts cannot get trapped between the flow element and the dam gate. Furthermore, the guide bushes of the fastening construction can be incorporated in said slab.
[0033] In a second embodiment of a device, the flow element consists of a fixed construction in the form of a platform.
[0034] With a device according to the second embodiment, the water level downstream of the dam must not vary too much.
[0035] With a device according to the second embodiment, one or more platforms may be used, depending on the geometric configuration of the dam.
[0036] Figure 1 is a longitudinal sectional view, which schematically shows the flow pattern behind a weir. This schematic view shows how a water layer flowing back can hold objects floating on the surface, including humans and animals, and shows the risk of drowning. The figure shows the submerged hydraulic jump and the outflow.
[0037] Figure 2 is a longitudinal sectional view, which shows the flow pattern behind a weir in which a flow element is present. As the figure shows, a surface eddy (hydraulic jump) of a harmless kind is formed. In the figure a supercritical flow over the flow element, the submerged hydraulic jump, and the outflow are shown.
[0038] Figure 3 is a longitudinal sectional view, which shows the flow pattern behind a weir in which a fixed platform is installed. The figure also shows how a surface eddy of a harmless kind is formed. In the figure a supercritical flow over the flow element, the submerged hydraulic jump, and the outflow are shown.
[0039] Figure 4 is a top plan view of an embodiment in which the flow element is configured as a floating plate attached to the weir (in this case an adjustable dam) by means of two rods and a hinge mechanism. In the figure the (existing) adjustable dam, the rod for guiding the plate in vertical direction, the rubber fastening strip, and the flow element are shown.
[0040] Figure 5 is a longitudinal sectional view A-A of the embodiment shown in figure 4. In the figure the rod for guiding the plate in vertical direction, the rubber fastening strip, and the flow element are shown.
[0041] Preferred embodiments relate to a weir as known from the literature, and are characterised by a device which influences a so-called (submerged) hydraulic jump caused by the transition from supercritical flow to sub-critical flow, such that it eliminates the risk of drowning for humans and/or animals who have fallen into the water, said device comprising: a flow element which is present, possibly floating, in the flow behind (downstream of) the weir; possible floating means, which give the flow element a degree of buoyancy corresponding to the hydraulic boundary conditions of the weir; a fastening construction, which keeps the flow element correctly positioned relative to the weir and the current hydraulic flow profile; means which prevent any injuries sustained by humans or animals as a result of getting trapped or other injuries sustained as a result of coming into contact with the flow element and/or the weir.
[0042] Preferably the flow element forms an additional "step", as it were, which is disposed approximately at the level of the downstream water level, wherein the falling water that flows over the weir first is deflected in horizontal direction, such that said supercritical flow causes a harmless hydraulic jump.
[0043] Preferably the device is characterised by a flow element which automatically adjusts itself to the varying water levels, both upstream and downstream, within the design criteria.
[0044] Preferably the device is characterised in that the flow element can be adapted to any weir as regards its dimensions.
[0045] Preferably the device is characterised in that the device can be used with fixed dams as well as with adjustable dams, both of the overflow type.
[0046] Preferably the device is characterised in that there is no risk of humans and/or animals getting trapped or sustaining other injuries upon coming into contact with the flow element.
[0047] Preferably the device is characterised in that the flow profile consists of one or more platforms behind the weir.
[0048] The invention is not restricted to the embodiments described above and as shown in the figures, but it also extends to other preferred embodiments that fall within the scope of the appended claims. It is clear that the plate and/or the plateau can be adapted to overflow dams of different size by changing the size of the plate and/or the plateau. Also, it is clear that the plate and/or the plateau are applicable to both adjustable and fixed weirs.
1. An overflow dam for maintaining a first water level at a first side of the dam, said
first water level being higher than the second water level at the second side of the
dam, wherein water from the first side of the dam may flow over the dam to the second
side of the dam, characterized in that said dam comprises an element extending at the second side of the dam, said element
having an upper surface which is at approximately the same height as said second water
level, such, that said water flowing over said dam lands on said element.
2. The overflow dam according to claim 1, wherein said dam comprises attaching means
for attaching said element to said second side of the overflow dam.
3. The overflow dam according to claim 2, wherein said dam is a hingeable dam, and wherein
said attaching means comprise a hinge for hingeably attaching said element to said
second side of the dam, such, that said element is hingeable around the longitudinal
axis of said dam.
4. The overflow dam according to claim 2 or 3, wherein said attaching means comprise
guiding means for guidingly attaching said element to said second side of the dam,
such, that said element is movable in a vertical direction for adapting to said second
water level.
5. The overflow dam according to claim 3 or 4, wherein the element has a buoyancy, such,
that in accordance with the pressure of said water flowing over said dam and landing
onto said element and in accordance with said second water level, said upper surface
of said element is maintained at approximately the same height as said second water
level.
6. The overflow dam according to any of the preceding claims 2-5, wherein sealing means
are provided between said element and said second side of said dam.
7. The overflow dam according to claim 6, wherein said sealing means comprise a neoprene
slab.
8. The overflow dam according to any of the preceding claims 1-7, wherein the element
is shaped as a plate.
9. A method for maintaining a first water level at a first side of an overflow dam, said
first water level being higher than a second water level at the second side of the
dam, wherein water from the first side of the dam flows over the dam to the second
side of the dam, characterized in that said dam comprises an element extending at the second side of the dam, said element
having an upper surface which is at approximately the same height as said second water
level, such, that said water flowing over said dam lands on said element.