US2605616A - Apparatus for recovering the hydraulic energy of a high velocity flow of water under free surface conditions - Google Patents

Description

Au 5, 1952 P. F. DANEL 2,605,616

APPARATUS FOR RECOV'ELEWIKB'- THE HYDRAULIC ENERGY OF A HIGH OF WATER UNDER FREE SURFACE CONDITIONS ELOCITY FLOW 2 SHEETS-SHEET 1 Filed Feb. 1948 INVENTOR.

BY wM HTTUR EYS Aug. 5, 1952 P. F. DANEL 2,605,616

APPARATUS FOR RECOVERING THE HYDRAULIC ENERGY OF A HIGH ACE CONDI VELOCITY FLOW OF WATER UNDER FREE SURF TIONS Filed Feb. 19, 1948 2 SHEETS-SHEET' 2 Fly- 5 A Fig.7

INVENTOR fikrm 11" 174 we] ATTORNEYS Patented Aug. 5, 1952 APPARATUS FOR- RECOVERING THE HY- DRAULIC ENERGY OF A HIGH VELOCITY FLOW OF WATER UNDER FREE SURFACE CONDITIONS Pierre Francois Danel, Grenoble, France, assignor to Ateliers Neyret-Beylier & Piccard-Pictet, Grenoble, France, a corporation of the French Republic Application February 19, 1948, Serial No. 9,396 In France October 9, 1946 Section 1, Public Law 690, August 8, 1946, Patent expires October 9, 1966 7 Claims.

The present invention has for an object to provide a means permitting the transformation of kinetic energy of a high velocity fiow of water in an open channel or under free surface conditions into potential energy with a small loss of such energy.

Various procedures are already known for bringing about this transformation or recuperation. The best known is that involving the production of a, hydraulic jump. This method, however, has the disadvantage that there is a substantial loss of'head.

It has likewise been sought to utilize the kinetic energy of the water to make it go up an opposed slope in such manner as to lead it graduallyto the level of recuperation that is desired.

Unfortunately, when the inclination of the bottom of the channel goes up again, the depth of the water increases at the bottom of the slope and the torrential fiow slackens while rapidly approaching a condition of critical velocity. Even before this transition there is risk that a hydraulic jump will occur and prevent the phenomenon from taking place. However, useful I results are attained in the following manner:

An opposing slope allows the flow to go up again until a certain point beyond which it becomes impossible to go further without bringing about a hydraulic jump. If the bottom is then gradually flattened so .as to establish a slightly roundedor sloping .sill, the resulting divergence in a vertical plane causes the water topass along and over this flattened portion orrsill without slackening the now to the point where a condition favorable to hydraulic jump will be created in the area at the bottom or foot of the slope, i. e., the foot of the. opposed slope on the upstream side of the sill. Consequently, a good recovery of energy is possible under these conditions. After passing the sill the water level may thengo up again to a point adjacent the plane of the head. While this method will insure a satisfactory recovery of the potential energy under ideal conditions, it has the drawback that a stable flow in that part of the channel along and over the rounded sill or crest is difiicult to realize in practice.

The present invention has for an object to improve the stability of such recovery systems and, in particular, to utilize to the maximum the principle of the opposed slope in downstream position with respect to the portion of a flu me or other channel through which a. torrential fiow is caused to travel without tending to a hydraulic jump condition.

My invention is based on my observation that a fiow of water passing at high velocity or under conditions of torrential flow from a downwardly inclined channel or fiume on to an opposed upwardly inclined slope, i. e.,- a channel section inclined upwardly in the direction of the downstream portion of the channel, may be caused to travel upwardly along such opposed slope in a suitable manner without tendency to hydraulic jump by arranging the side walls of the channel in the opposed slope portion thereof so that they gradually diverge in the downstream direction from the bottom end of such opposed slope to the downstream end thereof. The divergence of the side walls should be varied in such manner so as to conserve to the fiow its torrential character, i. e., so that the flow velocity is alwaysv greater than the wave velocity. As otherwise expressed the Froude number of the flow should always have a clearly defined value greater than one. As in the prior system previously described the opposed slope may be associated with a slightly rounded or sloping sill over which the water is passed from the opposed slope thus insuring the recovery of the remainder of the recoverable energy.

The arrangement of my invention whereby diverging side walls are substituted in the opposed sloping portion of the channel for the parallel side walls heretofore used has the advantage of insuring that the water may be delivered in torrential fiow to a definitely higher plane than with the use of parallel walls.

The recovery on the sloping sill is therefore of less importance than in the prior system, which is a definite advantage for the stability of the flow. The sloping sill may even be suppressed if it is not desired to obtain a maximum recovery.

The invention has numerous applications in situations where it is desired to obtain a substantial lowering of the water level while at the same time recovering in potential form the veloc-' ity energy by causing the water level to rise up again almost to the initial level.

In order to better understand the invention there are given hereinafter several examples of modes of its application supported by the accompanying drawings in which:

Fig. 1 is a view in part longitudinal section and pa side. elevation of achannel section embodying the invention and introduced ,into a hydraulic conduit of conventional form;

Fig. 2 is a plan View of the arrangementof Fig. 1;

Fig. 3 is a View in part side'elevation and part longitudinal section of another "form'iof water passage utilizing the invention;

Fig. 4 is a half plan view of the channel portion of the structure of Fig. 3; i Y I Figs. 5 and 6 are, respectively, similar views as those of Figs. 3 and 4 showing the application of the invention to a Venturi channel.

Fig. '7 is a part longitudinal sectionand part side elevation showing the application-ofthe" invention to a module and check gate construction of a type employed in distributing irrigation Waters.

It is often desirable to obtain the maximum rate of flow through a hydraulic channel, as for example, inemptying drainage basins of a temporary. nature such as used in evacuating floods; etc.

v :Thefunctioning. of these canals or conduits leading fromdrainagebasins, whether in open L "channel or under pressure involves generally the diverting of the flow to the bed or" a river and consequently at a point imposed by the water level therein.

The present invention malies possible to lower the water level in such drainage basins at a relatively high rate and under conditions utilizing atorrential rate of floweven though the difference betweenthe level in the drainage basin andthefwater level in the river at'the point where the waters are diverted to it is relatively small. gThis is made possiblebecause according to theinventio'n the water may be discharged from the drainage basin at a torrential rate of flow even though the water so discharged has to be elevated again to a level approaching that of-the drainage basin in order to eifect the discharge into the river at the water level obtained therein. Among other resulting advantages the dams customarily employed for impounding flood waters may be made of diminished height while at the same time effecting thetemporary impounding of such flood waters.

InjFig. 1 is shown at l the outlet of the drainage channel through which water passes underconditions of. torrential flow, at the opposed upwardly inclined slope with divergent walls corresponding to 3 (Fig; 2), at 4 the raised sill o'rcrest and at 5 a downward slope of'low incline. The surface of the waterfollows sub stantially the line indicated by 2 in Fig. 1 passing through the critical depth in the neighborhood of the crest. [It does not produce a hydraulic jump characteristic and the recovery of energy continues on the down slope 5. For example, one may calculate thedivergence of the Walls in" such a way that the Froude number (V /gh) which measures the torrential character- (velocity head) of the flow remains constant and clearly more than 1. In these conditions, the depth of the water noticeably decreases in approaching the raised sill or crest 3.

The flow is produced in the way described hereinonly for a certain range of discharge rates above a certain minimum" rate" of flow.

"rate of discharge remains low. If it tends to increase anew, the hydraulic jump will disappear, and the diverging channel will function again as it did before. In Fig. 3 and the following figures the downward slope that extends beyond the raised crest and permits the further recovery of the energy is not shown, but it will be understood that this slope will ordinarily be provided and in that case it may be the same as that in Fig. 1. On the other hand, when a maximum recovery is not desired, the final downward slope may be omitted and the sill or crest 4 is designed without special precautions with respect to the contour of the succeeding portions .of the channel or its mouth. Either of the two arrangements above may be applied in all of the modifications herein described.

Figs. 3 and 4 show the invention applied in a channel provided with a sharply downwardly, inclined weir designed to create a torrential flowing of the water from thedrainage' space or. basin. When the velocity head of the water is sufficiently reat to insure the torrential flow, the flow takes then the form indicated in full line on Fig. 3.

This disposition may advantageously be utilized in the case of a water take-off passage which is required to function .only in periods of low water. The diverting sill is arranged for example in the side wall of a canal. The water take-off is then placed, for example, at I. It will thus be seen that the water take-off ceases to function when the level upstream is raised tobring about a marked increase in the velocity head. This corresponds to periods of floods and permits the removal of materials such as gravel, pebbles, etc., encumbering the flow at such-times without danger that they'will pass into or plug the take-off I, which, for example, may be normally used to conduct irrigation waters to points of distribution. In normal periods the flow establishes itself through the passage 1 due to the filling up of the space 8 following the change to a hydraulic jump condition. The level of the water establishes itself at the level indicated by the clotted line and the water take-off passage 7 discharges normally. 7

Figs. 5 and 6 show how the invention may be utilized in measuring the volume of the discharge. It is knownthat in a given channel the critical depth of the flow is uniquely a function of the discharge. Therefore, the measurement of this depth constitutes a measure of the discharge. This method of measurement has already been used in Venturi channels that present a raised bottom or crest and a narrowing at the point of critical depth. Unfortunately, the energy recovery of standard canals is insuificient and such formsof apparatus remain of little use in spite of their simplicity because of the considerable waste of energythat is produced. The present invention maybe applied to this type of measuring apparatus with a minimum loss of energy. The height or critical depth of the water is Incasured at Q.

Fig. 7 shows an application of the invention in a'module or flow controlling device of the type which includes a rounded and downwardly inclined dividing crest or sill surmounted'by an adjustable inclined metal plate I9, behind which the water level may rise. The discharge of this type of apparatus is practically constant when the level upstream is held between two designated adjacent points. This apparatus is very useful for maintaining constant the discharge through a water take-off". As heretofore employed a hydraulic jump has been relied on to recover the velocity energy. In cases where large volumes of water are to be discharged, the dimensions of the hydraulic jump become such that an undue waste of energy will occur in most cases if a single apparatus is employed. This is why the apparatus is usually divided into a great number of small distinct modules. This is at the same time a complication and an advantage, for this allows of exact regulation of the discharge at the desired value by opening at will a selected number of sluiceways.

Nevertheless in many cases, it becomes desirable to decrease the number of these sluiceways. The present invention by augmenting the possible recovery of the velocity energy thereby notably improves the functioning of a single module and likewise makes it possible to eliminate a certain number of the installations as compared with the number heretofore considered necessary.

It is also to be understood that the module and check plate of Fig. '7 may beassociated withany one whatsoever of the widening channels of opposed slope of other figures of the drawing and in particular in association with that including a take-off passage shown in Fig. 3.

The invention is by no means limited to the specific embodiments described. It is applicable in various other forms that will suggest themselves to one versed in the art who desires to re cover the greater part of the energy of a torrential flow,

I claim:

1. An apparatus for recovering the kinetic energy of a torrentially flowing stream of water in the form of potential energy or hydraulic head comprising an open fiume receiving such flowing stream and having in the receiving portion thereof an inclination downstream sufficient to insure that the water will travel therealong at a velocity in excess of the critical velocity, and a second fiume portion leading from the downstream end of said receiving portion to an elevated point of discharge approximating th height of the bottom of the fiume at the entrance thereof, said second portion having confining side walls diverging gradually from one another in the direction toward said point of discharge, the divergence of said walls being within the range where the flow velocity of th water passing therebetween is greater than the wave velocity thereof.

2. An open control flume for normally conducting water from an upstream sourc of supply to a water take-off conduit and for automatically diverting water away from said take-off during conditions of substantially increased hydraulic head at said upstream source, comprising a downwardly inclined channel leading from said source of supply and merging at its lower end with an oppositely inclined channel constituting point of discharge, said oppositely inclined chan- '6 nel having confining sid walls which diverge gradually from one another in the direction toward said point of discharge, and said fiume having an ofi-take passage in the side wall thereof adjacent the point of merger of said channel portions, said off-take being spaced from the bottom of said channel sufficiently to permit water p ssing along the channel at a velocity greater than the critical velocity to pass beneath said off-take.

3. An open flume for conducting water from an upstream source of supply to a distant point without large loss of potential head which comprises a rounded sill extending upwardly from the bottom of the flume channel and presenting inclined surfaces respectively facing upstream and downstream therefrom, said inclined surface facing downstream having an inclination sufficient toinsure that water passing thereover will maintain a flow velocity in excess of the wave velocity in traveling thereover, and said fiume having a second channel portion communicating with and inclined upwardly from the bottom of said downstream facing surface of said sill in the downstream direction, said second channel portion having side walls diverging gradually from one another in the downstream direction at an angle within the range where the flow velocity of the water passing therebetween may be maintained greater than the wave velocity thereof.

4. An apparatus according to claim 3, wherein the wails of the channel opposite the downstream facing surface of said sill gradually converge in the downstream direction and cooperate with the diverging side walls of the second channel portion to form a Venturi throat in said channel.

5. An apparatus according to claim 1, wherein the downstream inclined flow-receiving portion or" said fiume is associated at its upper end with a check gate cooperating therewith to control the discharge of water to said flow-receiving portion from an impounded body of water.

6. Apparatus for recovering the kinetic energy of a torrentially flowing stream of water in the form of potential energy, comprising a conduit for discharging such a torrentially flowing stream, a divergent open flume section having its inlet connected to the discharge end of the conduit to receive water therefrom, said open fiume section having a bed whose elevation increases gradually in the downstream direction and a sill at its outlet over which the water is discharged, the divergence of said open flume section being so related to the depth'as to maintain the velocity of flow greater than the wave velocity throughout said fiume section.

7. Apparatus for recovering the kinetic energy of a torrentially flowing stream of Water according to claim 6, including a second open flume section connected to said first-mentioned section to receive the discharge therefrom, said second section having a bed whose elevation decreases in the downstream direction.

PIERRE FRANCOIS DANEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 991,907 Stickney May 9, 1911 2,025,722 Camp Dec. 31, 1935

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