GB2222074A - Circulating water pool - Google Patents

Abstract

A circulating water pool comprising upper passage (3), a lower passage (4) and curved front and rear passages (5, 6) which are connected together to form a loop around which water is circulated by impeller(s) (9), is provided with one or more arcuate guide vanes (29) in curved front passage (5), the guide vanes being arranged to form channels which generally increase in cross-sectional area from their upstream ends to their downstream ends with their maximum cross- sectional areas being at a point intermediate said ends and the spacings between the vanes generally increasing radially. The arrangement of vanes stabilises water flow to the upper passage. The pool may be used as a swimming pool or testing tank for models of ships or offshore structure. <IMAGE>

Description

CIRCULATING WATER POOLS The present invention relates to a circulating water pool in which a "working section" of smoothly flowing water is provided which may be used for learning how to swim or for intensive swimming training under the supervision of a coach or instructor.

Alternatively, the pool may be used as a testing tank for models of ships, offshore structures and the like.

Pools in which water is forced to circulate around a closed loop lying in a vertical plane are known.

Such pools generally have a window through which a swimmer may be observed for teaching purposes.

Two known circulating water pools will now be described with reference to Figures 1 and 2 of the accompanying drawings in which Figure 1 is a side sectional view of one type of known circulating water pool and Figure 2 is a similar view of another known circulating water pool.

The vertical circulating water pool shown in Figure 1 includes a main body or housing 1 mounted on a foundation 2 and comprises an upper water passage 3, a lower water passage 4 and front and rear passages 5' and 6' which deflect the water flow and connect the upper and lower water passages 3 and 4. One or both side walls of the main body 1 has a plurality of observation windows 7 along the upper water passage 3 and a portion of the top of the upper water passage is cut away, whereby an observation section 8 is defined.

An impeller 9 which causes water to circulate around the loop is located in the lower water passage 4 near its upstream end and is driven by a motor 10 located outside the main body 1. Guide vanes 11 are securely positioned in the front and rear curved passages 5 and 6 in order to effect a smooth change in direction of the water flow.

When the impeller 9 is driven by the motor 10 it forces water to circulate around the path defined by the passages 3,4,5 and 6.

In a water pool of the type described above, the front water flow deflection portion 5, which changes the direction of the water flow from the impeller, has two square corners at its outer edge. A set of short guide vanes 11 is disposed at each corner. The vanes of each set are arranged along a line approximately bisecting the angle of the associated corner and are spaced at equal intervals along it. The rotation or deflection of the water caused by the guide vanes causes it to have an outward component of movement due to the action of centrifugal force. In order to change this outwardly deflected water flow into a uniform parallel flow in the upper water passage 3, particularly in the observation section 8, a pressure chamber 12 of enlarged cross-sectional area is formed at the upstream end of the upper water passage 3.The pressure chamber 12 has three-dimensionally curved surfaces to reduce the cross-section of the passage to that of the upper passage 3. A nozzle-shaped portion extends upwardly from the upper surface of the pressure chamber 12 and communicates with a vacuum pump 13 arranged to reduce the pressure in the chamber and prevent a free water surface from forming in the chamber. Part of the upper water passage 3 along the length of the observation section 8 has a free water surface which is of course normally at atmospheric pressure. There is thus a pressure gradient between the free water surface and the water in the chamber 12 which results in standing or stationary waves being created in the upper water passage 3 along the observation section 8.Such standing or stationary waves, which are a serious problem in circulating water pools, are controlled by placing a horizontal wavesuppressing plate 14 at the water surface at the upstream end of the observation section 8. The combination of the plate 14 and the nozzle portion of the pressure chamber 12 produces a boundary layer which causes the flow rate to drop by about 20% along the observation section 8. In order to compensate for the decrease in flow rate, a surface accelerating device 15 is positioned between the pressure chamber 12 and the wave-suppressing plate 14.

In an attempt to solve the problems referred to above, a circulating water pool as shown in Figure 2 has been devised. The front and rear end of the main body 1 are curved to define the curved water passages 5 and 6 and a rounded protuberance 36 is formed at the upstream end of the bottom 3' of the upper water passage 3 to prevent turbulence as the flow passes through the front curved portion 5.

The protuberance 36 is to some extent effective in preventing separation or turbulence of the flow but the downstream end of the protuberance inevitably forms a step with the flat bottom 3' which results in a localised reversal of the flow. Furthermore, because of the variations in depth associated with this construction, the uniformity of the flow along the observation section 8 of the upper passage 3 is impaired and standing waves tend to be induced at the free water surface.

It is an object of the invention to provide a circulating water pool in which the above problems are substantially eliminated or reduced.

According to the present invention a circulating water pool comprises upper and lower passages joined by curved front and rear passages to form a loop and water-circulating means located in the lower passage adapted to cause water to flow around the loop through the lower passage, the front passage, the upper passage and the rear passage sequentially, the front passage containing one or more arcuate guide vanes which divide it into two or more channels, each channel having a larger cross-sectional area at its downstream end than at its upstream end and a still larger cross-sectional area at a point intermediate its ends, the crosssectional area of the outer channel or channels at any radial line being greater than that of the channel inside it.In this embodiment, in which there is not necessarily the diverging portion in the lower passage, the water flow is stabilised by the relative disposition of the guide vanes which ensure that the water flow in the upper passage is both non-turbulent and of uniform velocity profile in the vertical direction.

Each guide vane and the outer wall defining the front passage preferably include part-circular portions with centres of curvature which are offset from each other. The divider which separates the upper and lower passages preferably also has a part-circular end directed towards the outer wall of the front passage.

The various centres of curvature preferably all lie on a straight line and it is further preferred that the guide vanes and the outer wall of the front passage include a straight section at each end.

A specific embodiment of the present invention will now be described by way of example with reference to Figures 3 to 5 of the accompanying drawings, in which:- Figure 3 is a side sectional view of an embodiment of the present invention; Figure 4 is a detailed view illustrat-ing the arrangement of the wave guide shown in Figure 3; and Figure 5 is a detailed view illustrating a practical arrangement of a wave guide shown in Figure 4.

The same reference numerals are used to designate similar parts throughout the Figures.

In Figures 3 to 5, the upper water passage 3 is, for instance, about 2m in width and about 1m in depth (height) to enable the upper water passage to be used as a swimming course and the lower water passage 4, for instance, about 2m in width and about one-third thereof, that is about 666mm, in height. The operation of the circulating water pool can be carried out effectively with the use of only three small diameter impellers 9.

As may be seen from Figure 4, a coordinate system is defined in which the line connecting the outlet and inlet ends of the front curved water passage 5 forms the Y axis and the centre line between the lower boundary of the upper water passage 3 and the upper boundary of the lower water passage 4 forms the X axis.

The front curved plate 28 defining the outer edge of the curved passage 5 is semi-circular, when viewed in side elevation, centered on the point 08. The straight line connecting the centre of curvature 8 with the intersection (origin) of the X and Y axes is expressed by the formula y = -ax (where x < 0).

Disposed within the front curved water passage 5 are one or more guide vanes 29, in this case three vanes 29.1, 29.2 and 29.3 which are generally similar to those in the first embodiment. The guide vanes are of arcuate shape, and in this case part-circular, in side section and have centres of curvature 05, 6 and 07. The centres of curvature lie on the line joining the point 8 to the origin with the equation y = -ax (where x < O). The guide vanes are arranged such that the radial distance between successive guide vanes increases with increasing distance from the origin.

The centres of curvature are positioned such that at the outlet end of the front water passage 5 the radial distance between each adjacent pair of guide vanes is greater than at the inlet end of the water passage 5.

At either end of each guide vane is a horizontal portion which serves to increase the linearity of the water flow.

More specifically, the guide vanes 29.1, 29.2 and 29.3 are made of sheet metal such as stainless steel and are welded in the relative positions shown in Figure 5.

When the impellers 9, which are disposed in the lower passage 4 which is of less height than the upper water passage 3, are driven by the motors 10 the water in the lower water passage 4 is forced to flow into the front water passage 5 constituted by the channels 30,31,32 and 33 defined by the guide vanes 29.1, 29.2 and 29.3.

The channels 30,31,32 and 33 defined by the guide vanes 29 increase in width from a5, a6, a7 and a8, respectively at the inlet end to C5, c6, c7 and c8 at the point where they cross the straight line y = -ax and then gradually decrease to widths b5, b6, b7 and b8, respectively, at the outlets of the channels 30,31,32 and 33.

It follows from the above that the velocity of the flow passing through the channels 30,31,32 and 33 will decrease as the water flows through the section of increasing cross-sectional area and slight turbulence may occur. The water flow is however then compressed as it enters the zone 35 of decreasing cross-sectional area and this results in a slight increase in the velocity and the elimination of turbulence. The flows from the outlets of the channels has substantially equal head losses thereby resulting in a uniform distribution of the flow velocity over the height of the upper water passage 3.

Thus turbulence is substantially eliminated and the velocity profile in the upper passage is substantially constant. The lower passage may be of smaller cross-sectional area than the upper passage and this permits relatively small or low power water impellers to be used. In addition, many of the components which are conventionally required in such pools, e.g. a pressure chamber, vacuum pump and wave suppressing plate, are no longer required.

Claims (5)

1. A circulating water pool comprising upper and lower passages joined by curved front and rear passages to form a loop and water-circulating means located in the lower passage adapted to cause water to flow around the loop through the lower passage, the front passage, the upper passage and the rear passage sequentially, the front passage containing one or more arcuate guide vanes which divide into two or more channels, each channel having a larger cross-sectional area at its downstream end than at its upstream end and a still larger cross-sectional area at a point intermediate its ends, the cross-sectional area of the outer channel or channels at any radial line being greater than that of the channel inside it.

2. A pool as claimed in claim 1 in which each guide vane and the outer wall of the front passage include part-circular portions with centres of curvature which are offset from each other.

3. A pool as claimed in claim 2 in which the centres of curvature all lie on a straight line.

4. A pool as claimed in any one of claims 1 to 3 in which the guide vanes and the outer wall of the front passage include a straight section at each end.

5. A circulating water pool substantially as specifically herein described with reference to Figures 3 to 5 accompanying drawings.