inlet location to tank 1

[drain]

Hi,
1) We're designing a 1250m3, 2-cell un-baffled rectangular ground level concrete tank, 3.6m is the TWL. We're debating the issues of inlet location with respect to water turnover and chlorine residual. We've currently got our inlet discharging through an elbow downward at TWL. Any comments?

2) This issue concerns the tank's overflow discharge. Ten State Standards wants 1 -2 feet above grade for visibility. We've got Dept of Fisheries to satisfy that we're not putting chlorinated water into the creeks. Similar to item 1), but now we want vaporization, would a splash pad cause enough vaporization of chlorine to occur?

 

[drain]

I agree

 

[barryadamson]

Several years ago, we did a series of tests in a hydraulic lab to model reservoir flows based on various inlet & outlet locations. The reservoirs were up to 200 m square & up to 10 m deep & used for balancing storage in a large water distribution system. Several conclusions were made: -
* wind direction on open topped reservoirs dictated the circulation pattern irrespective of the inlets
* outlet location made very little difference in the flow pattern
* inlet location (both in plan & elevation) had the major impact (especially the velocity)
* at one stage in a reservoir, to mix an artesian water (hot) with ground water (nutrients) & dam water (sometimes some algae), we used a 'jet pump' where we directed the hot artesian flow in a pipe down the reservoir slope & into a submerged cone & a short length of (larger) pipe. This appeared to mix very well
* inlet velocity was the major contribution to flow patterns
* an inlet in the centre of one wall (in plan) at top water level, developed two large circular circular flow patterns. Not as effective as a bottom inlet
* an inlet located in a corner, if the flow was directed along a wall, a large circular flow pattern was developed, but if the flow was directed diagonally, two circular patterns developed (some dead spots)
* tests were also done for inlet location on models of tanks (for 1,000 to 5,000 cub m tanks) & the best location of an inlet was just above the top water level & directed circumferentially, causing a slow (but steady) circular pattern that spiralled downwards to the outlet with no dead spots
* this inlet (just above water level) means that there is a constant head on the pumps. If this is not required (lower tank levels mean lower pump head & higher flows) then the inlets are brought up under the footing & directed circumferentially up at an angle. Good circulation develops
regards
barrya

 

[drain]

Barry, who did you do the tests for?

 

[barryadamson]

You surprised me - seeing that the last comment was in May, I didn't think that you would still be interested in more info & I didn't expect you to answer.
The hydraulic tests were done for a major water utility in the State of Western Australia.
Regards
barrya