AU2005203918A1 - Apparatus for generating a counter-current flow - Google Patents

Description

WO 2005/066436 PCT/AU2005/000017 "Apparatus for Generating a Counter-Current Flow" Field of the Invention The present invention relates to an apparatus for generating a counter-current in a swimming pool or another recreational water body. In use a swimmer is able to 5 swim against the counter-current over a widely varying range of speeds. Background Art The following discussion of the background to the invention is intended to assist with facilitating an understanding of the invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any 10 of the material referred to was published, known or part of the common general knowledge or state of the art as at the priority date of the application. Some existing counter-current swimming pools relate to the generation of an exercise or counter-current across the full width of the pool, over a cross-sectional area exceeding the cross sectional profile of a swimmer by at least a factor of ten. 15 The energy demand of such systems is considered excessive, from an economical as well as from an environmental perspective. DE 2222594 (Hoppe) discloses such a system where the exercise current is generated across the full width of the pool. By virtue of the side walls being specifically tapered to diverge outwardly in a downstream direction, at an angle of 20 less than or equal to six degrees, the counter-current diverges outwardly, across the width of the pool, at the same taper angle. The flow velocity does not decrease significantly in the downstream direction because of the small, specific and critical size of the taper angle. Accordingly, the pool body needs to be relatively long, well in excess of 5 m so as to allow for different rates of progress 25 of the swimmer through the water. The above comments regarding energy demands and length of the pool body also apply in the case of the systems disclosed in US 5,005,228 (Mermelstein) and WO 2005/066436 PCT/AU2005/000017 -2 GB 2296861 (Newbery) with, in the latter case, the additional drawback that the water is discharged into pool in the form of a relatively narrow jet that impacts upon the swimmer. The mechanical provisions required to create and deflect the required current 5 means that the systems are not portable and cover almost the entire length of the pool. Consequently these systems can only be installed in existing pools at relatively high cost. Some existing counter-current pools generate the required water flow using a system of nozzles. This requires a pump with a high pressure head and energy 10 demand. If driven electrically the pump would need to draw its power from the main electricity grid or another source that is able to supply large amounts of power. With regard to the problem of installation, pool owners who would wish to convert their pool into an counter-current pool, having a system of nozzles, would find it 15 difficult to do so without incurring the relatively high cost of external excavation adjacent to the pool and installing a system of nozzles into in the wall of the pool. Another problem encountered by nozzle systems is that they cannot be easily detached from the pool body and deployed in another pool. A further problem encountered by nozzle systems is the fact that the high kinetic 20 energy with which the water emanates from the nozzles is destroyed, creating a highly turbulent flow with reduced buoyancy and, consequently, a reduced level of comfort for the swimmer, This is similar to the difficulty of trying to swim in white water streams. Yet another problem arises in that the swimmer has to guard against being swept 25 sideways away from the counter-current. It is against this background and the problems and difficulties associated therewith that the present invention has been developed.

WO 2005/066436 PCT/AU2005/000017 -3 Disclosure of the Invention According to a first aspect of the invention there is provided an apparatus for generating a counter-current flow in a body of water contained within a reservoir, the apparatus comprising: a flow path having an intake for drawing water from the 5 body of water, and a discharge for returning the water drawn through the intake to the reservoir in the form of the counter-current against which a swimmer can swim; and water propulsion means for generating water flow along the flow path from the intake to the discharge; the arrangement being that the counter-current has an initial width smaller than the width of the reservoir and diverges laterally 10 away from the swimmer in a manner whereby the divergence is substantially unrestrained, causing the velocity of the water to decrease relatively rapidly in the downstream direction, enabling the swimmer to vary his or her swimming rate over a substantial range without his or her distance from the discharge varying by more than a few metres. 15 Preferably the divergence of the counter-current is substantially unrestrained both horizontally and vertically. The water propulsion means may be capable of generating a water flow of about 250 litres per second at and energy demand not exceeding about 1.5 kW. To generate such a flow rate, with prior art nozzle type systems, a gross pumping 20 rate in the order of 15kW would be required. Thus in arrangements of the present invention, and in contrast to existing nozzle systems, it is realistically possible to power the water propulsion means electrically by direct current at low voltage. This serves to effectively eliminate any risk of electrocution to the swimmer. Furthermore by drawing the voltage from batteries coupled to solar panels the 25 system does not have to draw power from the communal electricity grid. This has environmental benefits as well as a greater reducing effect on operating costs. Preferably the flow path includes a conduit. The conduit may have a gradually converging inlet and a gradually diverging outlet, respectively upstream and downstream of the propulsion means. In these arrangements the conduit may be 30 hydro-dynamically streamlined in accordance with the so-called Venturi principle.

WO 2005/066436 PCT/AU2005/000017 -4 As a consequence the pressure build-up provided by the propulsion means does not have to significantly exceed the kinetic head of the flow at the outlet of the apparatus, which by implication means that the head loss is relatively minimal. For an outflow velocity not exceeding 1.8 m/s, the kinetic head loss would 5 preferably not exceed approximately 0.15 m. Conservatively increasing that figure by 100% to allow for energy losses at the inlet and within the conduit, the total head loss would not exceed 0.3 m. At a flow rate of 250 litres per second, this would render a net power demand of 750 W. Assuming with regard to a worst case scenario, that the efficiency of the 10 propulsion means would only be 50%, this means that the gross power drawn would as a result not exceed about 1.5 kW. Preferably the apparatus is adapted for the generation of water flow along the flow path from the intake to the discharge, without a substantial increase in water pressure at a relatively low energy demand. 15 The counter-current may diverge laterally away from the swimmer in a manner whereby the flow velocity of a section of the counter-current, taken across the counter-current away from the swimmer, has a curved profile in which the flow is fastest at the centre of the flow. Advantageously this renders a slightly higher kinetic head at the centreline, as a consequence of which the corresponding 20 reduction in piezometric head causes a lateral force on the swimmer towards the centreline. This 'self centring' effect may be enhanced by a simple elastic tether system that further biases the swimmer towards the centreline without inhibiting his or her stroking action. Thus in one arrangement the apparatus may include a system comprising an elastic tether and a device for attachment of the tether to 25 the swimmer, the tether for extending across the reservoir and for being coupled to the device for attachment of the tether to the swimmer such that the tether biases a swimmer in the device for attachment towards the centre of the counter current.

WO 2005/066436 PCT/AU2005/000017 -5 Preferably the propulsion means comprises a propeller-type or rotary-type thruster that is driven electrically or hydraulically to gently accelerate the flow such that the counter-current has an acceptable level of turbulence. The required power would preferably be supplied by batteries recharged by a solar panel system with the 5 voltage restricted to an extent necessary to protect the swimmer from harm and/or electrocution. Thus the apparatus may include batteries and a solar panel system configured to supply power to the water propulsion means without any risk of electrocution or harm to the swimmer. The propulsion means may be fully submerged, ensuring that, in addition to the 10 suppression of noise, the energy converted into heat while generating the water flow is fully utilised in raising the temperature of the pool water. This further enhances the energy efficiency of the apparatus in that it has a reducing effect on the amount of energy to be drawn from other sources for the purpose of raising the temperature of the water to a certain comfort level. 15 The inlet and outlet of the conduit may each be provided with a barrier such as protective rod type screens for preventing the swimmer from coming into direct contact with the propulsion means and also for preventing the entry of foreign objects. The conduit and/or discharge of the apparatus preferably contain flow conditioning 20 means such as at least one plate type flow partitioner for straightening and smoothing the flow. Preferably the apparatus can be secured to the reservoir by means of weights and the stability of the apparatus in use is enhanced by the presence of stabilising hydro-dynamic forces generated during the operation of the apparatus. This may 25 eliminate the need to fix the apparatus to the reservoir by means of fasteners such as bolts, screws, toggles or other mechanical means. The apparatus may include mounting means for mounting the apparatus adjacent a wall of the reservoir. The mounting means may include a buoyancy chamber for floating on or near the surface of the water, the buoyancy chamber being coupled WO 2005/066436 PCT/AU2005/000017 -6 to the conduit such that the conduit and outlet thereof rises and falls with the level of the water in the pool. In arrangements of the invention the mounting means may include a base arranged to rest on the a surface adjacent the upper periphery of the reservoir. 5 The conduit may be suspended therefrom such that the intake and outlet of the conduit are below the level of the water thereby obviating the need to fix the apparatus in place by means of mechanical fasteners. In particular forms of the invention the stability of the apparatus is further enhanced by a horizontal reaction force, directed towards the wall of the pool 10 adjacent the apparatus, created from the flow path having a bend from which the counter-current is discharged. The apparatus may be portable, in whole or in part, for easy installation and removal as well as for easy transfer between pools. The apparatus may be externally attached to or integrated into the wall of a prefabricated and/or existing 15 pool during its manufacturing stage. Advantageously, in preferred arrangements of the invention, the apparatus is configured so that a 80% reduction in flow velocity is accomplished at about 2.5 m from the discharge means. The initial width of the counter-current may be slightly greater than the shoulder width of the swimmer and in preferred embodiments 20 may be about 1 m. Brief Description of the Drawings The invention will be better understood by reference to the following description of various specific embodiments thereof as shown in the accompanying drawings in which: 25 Figure 1 is a plan view of a the counter-current provided by an apparatus in. accordance with a first embodiment of the invention; WO 2005/066436 PCT/AU2005/000017 -7 Figure 2 is a vertical section view of the counter-current illustrated in Figure 1 taken along the plane designated A-A in the direction of the arrows. Figure 3 is a plan view of a second embodiment of the invention with swimmer being positioned off-centre. 5 Figure 4 is a vertical section view.of the embodiment illustrated in Figure 3 taken along the plane designated A-A in the direction of the arrows. Figure 5 is a schematic side view of apparatus illustrated in Figure 1; Figure 6 is a schematic front view of the apparatus shown in Figure 5; Figure 7 is a schematic side view of another embodiment of the invention; 10 Figure 8 is a front view of the embodiment shown in Figure 7; Figures 9. and 10 are side and front views of further embodiment of the invention; and Figures 11 and 12 are side and front views of yet another embodiment. Best Mode(s) for Carrying Out the Invention 15 Referring to Figures 1 and 2 there is shown a first embodiment of the invention in which a counter current apparatus I discharges a counter-current flow 2 into a swimming pool 3. The apparatus I has a flow path providing a discharge 4 with a breadth 5 not much larger than the body width 6 of a fast swimmer 7 and an outflow depth 9 not 20 exceeding the swimmer's body depth 10. The flow 2 diverges laterally away from the swimmer 7 along approximate flow boundary lines 11 and vertically away from the swimmer along approximate flow boundary line 12.

WO 2005/066436 PCT/AU2005/000017 -8 As a consequence the flow velocity decreases rapidly in a downstream direction from approximately 1.8 m/s at discharge 4 (at a rate of flow 2 of approximately 250 litres per second) to approximately 1.2 m/s at the location of fast, free-style swimmer 7, and further downstream to approximately 0.4 m/s at the location of a 5 slow, breast stroking swimmer 8, with the distance 13 between the discharge 4 and fast swimmer 7 not exceeding I m and the distance 14 between fast swimmer 7 and slow swimmer 8 not exceeding 1.5 m. These values are of course preferred. The cross sectional area of the flow at the location of swimmer 7 dictates that the 10 flow rate be about 250 litres per second to provide a flow velocity of about 1.2 m/s. Given that outlet depth 15 does not exceed 0.4 m and the body length of swimmer 8 does not exceed 2 m, the required minimum length 16 of the pool 3 along axis line A-A does not exceed 5 m. 15 To allow the boundary flow lines 11 to diverge in an unrestricted manner over at least until the position of swimmer 8 , the width 5 of the discharge 4is 1 m and the lateral distance from the side edge of the apparatus 1 to the nearest lateral side wall of pool 3 is at least 0.5 m. The initial width of the counter-current 2 is 1 m or slightly greater than the shoulder width of the swimmer 7. 20 Thus the flow 2 has initial width 5 at discharge 4 smaller than the width of the pool 3 that diverges laterally away from the swimmer 7 in a manner whereby the divergence is substantially unrestrained causing the velocity of the water to decrease relatively rapidly in a downstream direction. This enables the swimmer 7 to vary his or her swimming rate over a substantial range without his or her 25 distance from the discharge varying by more than a few metres. Thus if swimmer 7 was to vary his swimming rate to a breast-stroke, that is swim at a slower speed, the swimmer 7 would be pushed back to the location of swimmer 8. In this arrangement the flow velocity of the flow 2 experience by swimmer 7 is about 1.4 ms 1 while the flow velocity experienced by swimmer 8 is about 0.4 ms 1

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WO 2005/066436 PCT/AU2005/000017 -9 The flow velocity decreases at a relatively low level of turbulence, creating a smooth swimming flow. In Figure 1 there is shown a cross-section 17 of the velocity of flow 2 across the pool. The direction of the arrows in cross-section 17 indicate the divergence of 5 the flow 2 while the length of the arrows shows that the flow velocity has a curved profile in which the flow is fastest at the centre. The curved velocity profile causes the kinetic energy of the flow 2 to be higher at the centreline A-A than at the flow boundaries 11. This renders a slight water level depression across the counter-current away from the swimmer (perpendicularly to line A-A) and as a 10 consequence a lateral centralizing force 18 will be exerted on a swimmer when located sideways from the centreline. In a second embodiment of the invention shown in Figures 3 and 4 the centralising force 18 is enhanced with the use of an elastic tether 20 mounted across the counter-current flow 2 with a clipping hook 21 attached to it at its 15 mid-point. The elastic tether 20 has its end points fixed at the edges of pool 3 by means of weights 23 and hook 21 is clipped onto a waist belt 24 that is attached to the swimmer. The elastic tether 20 renders a further centralizing force 25 without inhibiting the arm motion of the swimmer 19. The centralizing force 25 increases in linear proportion to the lateral distance of swimmer 19 from centre 20 line A-A. The apparatus I shown in Figures 1 and 2 is shown in more detail in Figures 5 and 6. Referring now to those Figures it can be seen that the apparatus I comprises a flow path 22 having an intake 28 through which water is drawn from the pool 3, and a discharge 4 from which counter-current 2 is ejected into the pool 25 3. A water propulsion means, in the form of a propeller 26 and a hydraulically or electrically powered motor 27, is located between the intake 28 and discharge 4. The propeller 26 generates a water flow along a flow path 22 extending from the intake 28 to the discharge 4 without a substantial increase in water pressure and at a relatively low energy demand. The flow path 22 includes a conduit 29.

WO 2005/066436 PCT/AU2005/000017 -10 As can be seen from Figure 6 the conduit 29 is hydro-dynamically streamlined in accordance with the so-called Venturi principle, having a gradually converging inlet at the intake 28 and a gradually diverging outlet at the discharge 4. In an alternate embodiment shown in Figures 7 and 8 the water propulsion means 5 is provided in the form of a rotor 30 with vanes 31. The flow path 22 in the alternate embodiment includes two branches 22', 22". By having two branches 20' and 20" better use is made of the Venturi effect. Depending on the location of rotor 30, conduit 34 can be single or bisected. Referring with particular reference to Figure 6, the conduit 29 includes a number 10 of plate type flow partitions or vanes 46 that direct the water towards the discharge 4. The vanes 46 serve to eliminate (or at least dissipate) the rotary "cork screw" component of the flow generated by the rotating action of the thruster blades. The vanes 46 are accordingly used for straightening and smoothing the flow 2 and for minimization of energy demand. 15 The apparatus 1 includes mounting means 50 comprising a weight 42 and pair of rods 41. The conduit 29 is slidably mounted to the rods 41 such that with the use of a buoyancy chamber 39 the system is able to maintain the upper level of the discharge 4 just below the (variable) water level in the pool. Given that the flow path 22 moves from vertical to horizontal there is provided a 20 reaction force 43 that is directed into the adjacent side wall of pool 3. The reaction force 43 assists with the stabilization of the system. The upward reaction force is effectively cancelled by the opposite force being exerted on the propeller 26. For safety, a barrier in the form of a rod type protection screen 44 is provided 25 across the intake 28 while a similar protection screen 45 is provided across discharge 4. An alternate arrangement is shown in Figures 9 and 10. In this arrangement a rotor 35 with vanes 36 is driven by a rotary motor 37.

WO 2005/066436 PCT/AU2005/000017 -11 Yet another embodiment of the invention is shown in Figures 11 and 12. In this arrangement the apparatus I has been physically attached to or incorporated into the outside of an pre-existing pool 3 or during its manufacturing, or after installation. 5 It will be understood that various changes may be made to the form, details, arrangement and proportion of the various parts and steps without departing form the spirit and scope of the invention. Modifications and variations such as would be apparent to the skilled addressee are, at the very least, considered to fall within the scope of the invention, of which the preferred embodiments described 10 herein are specific example. With the arrangements described the problem of conventional counter-current pools not being able to readily allow a change in swimming rate of a swimmer has been addressed. With the invention, a swimmer in order to be able to swim continuously is no longer forced to maintain a constant rate that is sufficient to 15 counteract the force being applied to him or her by the counter-current. This achieved over a relatively short distance by having the divergence of the flow relatively substantially unrestrained such that the flow velocity relatively rapidly decreases with an acceptable level of turbulence. TPortable systems described have a relatively efficient energy economy with a 20 consumption in the order of 10% of the energy usage of existing pool flow systems at a similar flow rate. Additional benefits include energy loss recovery by submerging the propulsion means so that the heat generated is used to heat the water to a higher water temperature and versatility in providing an autonomous unit that is either free standing (above or in ground) or floating in an existing pool, 25 or, alternatively, an auxiliary unit that hangs off the side of an existing pool. Throughout the specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. 30

Claims (24)

1. An apparatus for generating a counter-current flow in a body of water contained within a reservoir, the apparatus comprising: a flow path having an intake for drawing water from the body of water, and a discharge for returning 5 the water drawn through the intake to the reservoir in the form of the counter current against which a swimmer can swim; and water propulsion means for generating water flow along the flow path from the intake to the discharge; the arrangement being that the counter-current has an initial width smaller than the width of the reservoir and diverges laterally away from the swimmer in a 10 manner whereby the divergence is substantially unrestrained, causing the velocity of the water to decrease relatively rapidly in the downstream direction, enabling the swimmer to vary his or her swimming rate over a substantial range without his or her distance from the discharge varying by more than a few metres. 15

2. An apparatus as claimed in claim I wherein divergence of the counter-current is substantially unrestrained both horizontally and vertically.

3. An apparatus as claimed in claim 1 wherein the flow path includes a conduit having a gradually converging inlet and a gradually diverging outlet between which the water propulsion means is located. 20

4. An apparatus as claimed in claim 3 wherein the conduit is hydro-dynamically streamlined in accordance with the so-called Venturi principle to reduce energy demand.

5. An apparatus as claimed in claim I wherein the apparatus is adapted for the generation of water flow along the flow path from the intake to the discharge, 25 without a substantial increase in water pressure at a relatively low energy demand. WO 2005/066436 PCT/AU2005/000017 -13

6. An apparatus as claimed in claim 1 wherein the power drawn from the water propulsion means, at a flow rate of about 250 litres per second, does not exceed about 1.5 kW.

7. An apparatus as claimed in claim 1 wherein the apparatus includes batteries 5 and a solar panel system configured to supply power to the water propulsion means without any risk of electrocution or harm to the swimmer.

8. An apparatus as claimed in claim I wherein the counter-current diverges laterally away from the swimmer in a manner whereby the flow velocity of a section of the counter-current, taken across the counter-current away from the 10 swimmer, has a curved profile in which the flow is fastest at the centre of the flow.

9. An apparatus as claimed in claim 8 including a system comprising an elastic tether and a device for attachment of the tether to the swimmer, the tether for extending across the reservoir and for being coupled to the device for 15 attachment of the tether to the swimmer such that the tether can bias a swimmer in the device for attachment towards the centre of the counter current.

10. An apparatus as claimed in claim I wherein the apparatus can be secured to the reservoir by means of weights and the stability of the apparatus in use is 20 enhanced by the presence of stabilising hydro-dynamic forces generated during the operation of the apparatus.

11. An apparatus as claimed in claim I wherein the apparatus includes a conduit that at least in part defines the flow path, the conduit having a gradually converging inlet and a gradually diverging outlet that are both provided with a 25 protective barrier for preventing the swimmer from coming into direct contact with the propulsion means and for preventing the entry of foreign objects.

12. An apparatus as claimed in claim 1 wherein the apparatus includes mounting means for mounting the apparatus adjacent a wall of the reservoir, the WO 2005/066436 PCT/AU2005/000017 - 14 mounting means including a buoyancy chamber for floating on or near the surface of the water, the buoyancy chamber being coupled to the conduit such that the conduit and outlet thereof rises and falls with the level of the water in the pool. 5

13. An apparatus as claimed in claim 1, which as a whole or in parts, is portable, allowing for easy installation, removal and storage as well as easy transfer between pools.

14. An apparatus as claimed in claim 1 including flow conditioning means such as at least one plate type flow partitioner for straightening and smoothing the flow 10 so as to further enhance the energy efficiency of the apparatus.

15. A counter-current swimming apparatus for providing a counter-current in a counter-current swimming pool, the apparatus comprising a conduit having an inlet and an outlet and being configured such that a propulsion means can be positioned between the inlet and outlet for providing water through the conduit 15 to a discharge means for subsequent discharge, the discharge means for forming the counter-current by discharging a flow of water into the pool, against which a swimmer is able to swim, the apparatus being configured such that the flow has initial width smaller than the width of the pool and diverges outwardly away from the swimmer in a manner whereby the 20 divergence is substantially unrestrained such that the flow velocity relatively rapidly decreases without high turbulence thereby allowing a swimmer to swim at any one of a number of different rates, over a relatively short distance.

16. A counter-current swimming apparatus as claimed in claim 15 wherein the apparatus is configured so that a 80% reduction in flow velocity is 25 accomplished at about 2.5 m from the discharge means.

17. A counter-current swimming apparatus as claimed in claim 15 wherein the conduit is divided into a plurality of chambers that channel the flow to limit turbulence and are of an elongate cross section so as limit energy losses and pressure build up. WO 2005/066436 PCT/AU2005/000017 -15

18. A counter-current swimming apparatus as claimed in claim 15 wherein the conduit is hydro-dynamically streamlined in accordance with the venturi-principle to increase the efficiency of the propulsion means in generating the flow. 5

19. A counter-current swimming apparatus as claimed in claim 15 wherein the apparatus is configured so that the flow diverges outwardly towards the bottom of the pool as well as outwardly towards sides of the pool.

20. A counter-current swimming apparatus as claimed in claim 15 wherein the counter current apparatus is portable and includes mounting means for 10 mounting the apparatus adjacent a wall of the pool.

21. A counter-current swimming apparatus as claimed in claim 20 wherein the mounting means includes a float means for floating on or near the surface of the water and the discharge means is coupled to the float means such that in use the discharge means rises and falls with the level of the water in the pool. 15

22. A apparatus substantially as described herein with reference to the accompanying drawings.

23. A counter-current swimming pool incorporating an apparatus according to any one of the preceding claims.

24. A counter-current swimming pool substantially as described herein with 20 reference to the accompanying drawings.