GB2222075A

GB2222075A - Circulating water pool

Info

Publication number: GB2222075A
Application number: GB8909704A
Authority: GB
Inventors: Osamu Teratsuji; Keiichi Nishimura; Yoshiro Moriya; Yukihiko Ueda
Original assignee: IHI Corp
Current assignee: IHI Corp
Priority date: 1988-08-22
Filing date: 1989-04-27
Publication date: 1990-02-28
Anticipated expiration: 2009-04-27
Also published as: GB8909704D0; GB2222075B; JPH0257276A

Abstract

A circulating water pool comprising upper passage (3), lower passage (4) and curved front and rear passages (5, 6) which are connected together to form a loop, and one or more motor-driven impellers (9) for circulating water around the loop, the lower passage including a diverging portion (17) of increasing cross-sectional area in the direction of flow and the front passage having a substantially uniform cross-sectional area over its length which is substantially equal to that of the downstream end of diverging position (17). The lower passage may have a converging portion (18) upstream of the impeller(s). Guide vanes (20) may be located in passages (5, 6). The pool may be used as a swimming pool or as a testing tank for models of ships or offshore structures. <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 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 water passages connected by front and rear water passages to form a loop and water-circulating means located in the lower passage adapted to cause water to flow around the loop, the lower water passage including a diverging portion of increasing cross-sectional area in the direction of flow, the water circulating means being located in the vicinity of the upstream end.of the diverging portion, the front passage having a substantially uniform crosssectional area over its length which is substantially equal to that of the downstream end of the diverging portion of the lower passage and that of the upstream end of the upper passage.Thus the cross-sectional area of the loop is maintained substantially constant from the downstream end of the lower passage to the upstream end of the upper passage and this results in a uniform velocity profile in the upper passage and permits various of the features of the known pools referred to above to be omitted. In practice, the loop is likely to be of constant width and thus the references above to the cross-sectional areas of the various portions of the loop are equivalent to references to the height or depth of the various passages.

The diverging portion of the lower passage is defined by upper and lower surfaces of which at least one and optionally both are inclined to the horizontal.

The lower passage preferably also includes a converging portion of decreasing cross-sectional area in the direction of flow arranged upstream of the diverging portion. The lower passage may also include a portion of constant cross-sectional area downstream of the diverging portion.

Two specific embodiments 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 illustrating the arrangement of the wave guide shown in Figure 3; Figure 5 is a side sectional view of a modification of the pool of Figures 3 and 4.

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

The circulating water pool shown in Figure 3 has an upper water passage 3 of height H1, front and rear curved water passages 5 and 6 each having a width W1 and a lower water passage 4 which is separated from the upper passage by a divider 23 and has a non-uniform cross-sectional area but is symmetrical about a horizontal plane through the axis of the lower water passage 4. The passages 3,4,5 and 6 are connected together to form a continuous loop in the vertical plane around which, in use, water flows clockwise, as seen in Figure 3. The upper and lower water passages are separated by an elongate divider with semi-circular ends. The lower water passage 4 includes a parallelsided section 16 of reduced height H2 at the upstream and downstream ends of which are converging and diverging sections 18 and 17, respectively. These have heights H4 and H3 respectively at their larger ends.

The dimensions H4 and H3 are substantially equal to H1.

Downstream of the diverging section 17 is a parallel sided section 19 of height H3.

One or more impellers 9 are disposed side by side in the straight parallel sided section 16 and are driven by a motor or motors 10.

Disposed within the front and rear curved water passages 5 and 6 are a plurality of guide vanes 20 which are arranged such that the distances between adjacent pairs increase with increasing radial distance of the vanes from the inner surfaces of the curved water passages 5 and 6. In this embodiment the following conditions are satisfied: a1 = b1 a2 = b2, a3 = b3 and a4 = b4, where a1 : the distance between the upper plate 21 of the straight pipe section 19 and the first guide vane 20.1; a2 : the distance on the inlet side between the first guide vane 20.1 and the second guide vane 20.2; a3 : the distance on the inlet side between the second guide vane 20.2 and the third guide vane 20.3; a4 : the distance between the third guide vane 20.3 and the bottom plate 22 of the straight pipe section 19; b1 : the distance between the bottom plate 23 of the upper water passage 3 and the first guide vane 20.1; b2 : the distance on the outlet side between the first and second guide vanes 20.1 and 20.2; b3 : the distance on the outlet side between the second and third guide vanes 20.2 and 20.3; and b4 : the distance between the third guide vane 20.3 and the outer plate 24 of the upper water passage 3.

In use, water is caused to circulate by the impeller or impellers and due to the geometry of the lower passage the water accelerates in the section 18, enters section 16 through which it flows at constant velocity and decelerates out into the diverging section 17 where the height of the flow path progressively changes from H2 to H3 which is substantially the same as the width of the curved water passage 5 which in turn is substantially equal to H1.

The radial distances between the guide vanes 20.1, 20.2 and 20.3 in the curved water passage 5 are constant over the length of the water passage 5. The function of the guide vanes is to preserve the laminar nature of the flow in the water passage 5. The head losses in the curved channels between the guide vanes are thus kept substantially equal thereby resulting in the water flow through the upper water passage 3 having a uniform flow rate distribution over its height.

The water flow from the upper passage 3 enters the rear curved water passage 6 and from there flows into the converging section 18 where it is accelerated by the impeller or impellers 9.

In Figure 5 a modified form of the pool of Figure 3 is shown which is substantially similar in most respects and differs from it only in that in the lower water passage 4 the converging and diverging sections 25 and 26 are defined by a horizontal lower surface 27 and inclined upper surfaces so that the passage 4 is not symmetrical about a horizontal plane. The inclined upper surface of the diverging section 26 preferably extends at an angle of less than 60 to the horizontal.

Downstream of the diverging section 26 is a parallel sided section 19 of constant cross-sectional area.

In this modification, the arrangement of the guide vanes is substantially the same as in Figures 3 and 4 and the water again flows into the upper passage 3 with substantially equal head losses. As a result the water flow passing through the upper water passage 3 has a uniform flow rate distribution in the vertical direction. The construction of the diverging section 26 which is defined by a lower horizontal surface and an upper inclined surface further improves the uniformity of the distribution of the water velocity over the height of the flow in the upper water passage 3.

The circulating pool and the modification thereof described above have a lower passage with a converging section followed by a diverging section at the upstream end of which there are one or more impellers. The impellers are thus placed at an area of reduced crosssectional area which enables impellers of reduced size and thus reduced cost to be used. The height of the downstream end of the diverging section of the lower passage 4, the height of the upstream end of the upper passage 3 and the width or breadth of the curved passage 5 are all substantially equal and this coupled with the fact that the spacing of adjacent guide vanes is constant over their length means that standing or stationary waves are suppressed, the head losses between adjacent pairs of guide vanes are substantially equal, the flow is maintained laminar and the velocity profile over the height of the upper passage is maintained constant.

Claims

1. Circulating water pool comprising upper and lower water passages joined by front and rear water passages to form a loop and water-circulating means located in the lower passage adapted to cause water to flow around the loop, the lower water passage including a diverging portion of increasing cross-sectional area in the direction of flow, the water-circulating means being located in the vicinity of the upstream end of the diverging portion, the front passage having a substantially uniform cross-sectional area over its length which is substantially equal to that of the downstream end of the diverging portion of the lower passage and that of the upstream end of the upper passage.

2. A pool as claimed in claim 1 in which the upper surface of the diverging portion is inclined to the horizontal and the lower surface is horizontal.

3. A pool as claimed in claim 1 in which the upper and lower surfaces of the diverging portion are inclined to the horizontal.

4. A pool as claimed in any one of the preceding claims in which the lower passage includes a converging portion of decreasing cross-sectional area in the direction of flow, the converging portion being arranged upstream of the diverging portion.

5. A pool as claimed in any one of the preceding claims in which the lower passage includes a portion of constant cross-sectional area downstream of the diverging portion.

6. A circulating water pool substantially as specifically herein described with reference to Figures 3 and 4 or Figure 5 or Figures 6 to 8 of the accompanying drawings.