water running over a border
water running over a border
(OP)
Maybe a wrong forum to post it.
If so please redirect me.
A swimming pool will have all around it a leveled border.
Width 4.4 meter , length 13 meter
The pump can deliver 35 m3/hour.
The water will overflow all around the border.
Now the one million dollar question.
HOW MUCH WILL THE WATER RISE FROM THE BORDER??
If so please redirect me.
A swimming pool will have all around it a leveled border.
Width 4.4 meter , length 13 meter
The pump can deliver 35 m3/hour.
The water will overflow all around the border.
Now the one million dollar question.
HOW MUCH WILL THE WATER RISE FROM THE BORDER??





RE: water running over a border
A = Perimeter P X Depth D
D = Q / (V X P)
Mike McCann
MMC Engineering
RE: water running over a border
Mike McCann
MMC Engineering
RE: water running over a border
You left out what the edge is like. How wide is the edge?
If it's like a tile width you're supposed to bring the velocity across the weir to this party too.
Keith Cress
kcress - http://www.flaminsystems.com
RE: water running over a border
Mike McCann
MMC Engineering
RE: water running over a border
RE: water running over a border
Mike McCann
MMC Engineering
RE: water running over a border
RE: water running over a border
Mike McCann
MMC Engineering
RE: water running over a border
Bending I do not know yet , it is at the shop.
RE: water running over a border
A swimming pool will have all around it a leveled border.
Width 4.4 meter , length 13 meter.
RE: water running over a border
htt
http://www.engineeringcivil.com/weirs.html
RE: water running over a border
Well, over 34.8m weir, a measly 35m3/hr translates to only:
35/3600m3/s or
0.01m3/s
About 2mm of flow over the edge.
Keith Cress
kcress - http://www.flaminsystems.com
RE: water running over a border
I want to ask a further more.
How I can made a small scale prototype.
I was thinking on a a small tank , but I guess I need to keep the area perimeter ratio.
1st case, and not a prototype ,
If for the same perimeter say 36 m ,to work with round numbers,I have 13m length and 5m wide= 65 m2 area, and for 35 m3/hour the water speed is 0.000270062 m/seg , but If I keep the perimeter changing the side sizes, speed will increase , thus the over flow will be great.
m3/h m3/seg
flow 35 0.009722222
meter meter m2 meter m/seg
lenght wide area perimeter speed
13 5 65 36 0.000149573
17 1 17 36 0.000571895
17.9 0.1 1.79 36 0.005431409
17.95 0.05 0.8975 36 0.01083256
Attached is the xls
Then the given formula seem to be not the best suited.
Hydraulics was and, seem to be,a empirical solution science, despite the modern software, as if I'm not wrong , they use the same Darcy-Weisbach formula, and others.
So how can I design a prototype?
My intention, is to build small pool and start pumping up water until I get the desired overflow, the scale the flow to meet the new poll overflow.
My final purpose is to calculate the flow need for any overflow at any pool I have to build.
Thanks again.
RE: water running over a border
RE: water running over a border
So it is like when you let flow water in a round hose, it reach a overflow , but if you squeeze it , for the same flow , the overflow will increase.
As far as I see on text books , weir formula are for open channel , and in this case I consider the pool as a big pipe.
Of course I can be wrong.
How can I build a scaled prototype?
Shall I consider the prototype to have the same HYDRAULIC RATIO??
If so , when I know the flow at the model , how I rescale it to get the real pump flow value ?
RE: water running over a border
www.
RE: water running over a border
Then I fit a pump and increase flow to have the same overflow I want to have at the 34.8 m weir.
I scale by 0.01 or 100 ,
So what will be the flow for the real pool's pump?
RE: water running over a border
Another thought here is that the 45 degree backslope at the interior of the pool rim will have an impact on the flow and depth, and that the "sharp crested" condition is only an approximation since, realistically, there is a small radius to the bend thast will increase the flow.
If you need an exact solution, then a livfesize model would be appropriate here, with, say a 3 foot weir width for the flow. You should be able to back in the Q and depth at the weir you will get with this setup. I do not think that a reduced model will give you the accurate depth measurement that you seek.
Mike McCann
MMC Engineering
RE: water running over a border
Keith Cress
kcress - http://www.flaminsystems.com
RE: water running over a border
Another reference gives me the following equation:
q=Kh3/2
where K is a dimensional constant depending only on fluid density (and the gravitational constant) and q is q=Q/b (b=width of weir or pool perimeter in the present case). So the formula above is confirmed.
In conclusion, if the goal is to keep the same crest height in the model as in the actual pool, then simply Q/b must be kept constant.
prex
http://www.xcalcs.com : Online engineering calculations
http://www.megamag.it : Magnetic brakes and launchers for fun rides
http://www.levitans.com : Air bearing pads
RE: water running over a border
I have to ask you , please understand my point of view.
1._ It is not a open channel weir.
In a open channel, weir it is only one side , 2 sides are the channel border , and the 4th is the water upward the channel, so the the water is constrain in 3 sides.
2._ The pool area is the same as a BIG HUGE pipe end standing vertical, so its border is horizontal, and water overflow all over the border, there is no constrain.
Some where I see the way to size flow by the height the water rise in a open vertical end pipe.
3._ guess it is a circle pipe , it will have the hydraulic radius as Hr = pi*r*r/2*pi*r or Hr= r/2
4._ Now for a rectangle with the same wet perimeter as the pipe, but with a 1.5 m side by 0.07 m have the same perimeter 3.14 m but the area is 0.105 m2 so the Hr = 0.0334 m . and for the same flow 35m3/h the speed is 138.88m/s, it is only a sample calculation, maybe it can not be a real case , as speed is 500 km/hr.
5.- So it can not behave the same way for a given flow,
it is evident that in the rectangular shape the water will rise upper than in the round pipe.
RE: water running over a border
prex
http://www.xcalcs.com : Online engineering calculations
http://www.megamag.it : Magnetic brakes and launchers for fun rides
http://www.levitans.com : Air bearing pads
RE: water running over a border
What is a circular vertical thank ,15 m diameter , when it is fill by the botton end.
The same used at oil industrie to hold fluids.
Is or is not a pipe?
Will fluid overflow by its border or not, when the fluid reach the border.
RE: water running over a border
The point is that this is not the correct model to calculate the height of the crest going beyond the border, as the velocity in your BIG HUGE pipe is negligible with respect to the velocity of the overflowing water and has no influence on crest height.
prex
http://www.xcalcs.com : Online engineering calculations
http://www.megamag.it : Magnetic brakes and launchers for fun rides
http://www.levitans.com : Air bearing pads
RE: water running over a border
Thanks