# Flow rate in open channel

1. Mar 28, 2016

### foo9008

1. The problem statement, all variables and given/known data
I was told that the flow rate in open system at 2 points in the pipe system are not the same, is it true??

2. Relevant equations

3. The attempt at a solution

2. Mar 29, 2016

### SteamKing

Staff Emeritus
Who knows? You talk about open systems, then you mention pipe systems. We weren't there when you were told something vaguely related to flows, so you'll have to provide us with more details and context for the statement in the OP.

3. Mar 29, 2016

### foo9008

i mean open pipe system . The example of pipe is shown in the picture

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4. Mar 29, 2016

### haruspex

The two points are very different. One is in then middle of the flow, while the other is at the entrance to a pipe that, ultimately leads nowhere.
Clearly the flow at the second point must eventually taper off to zero.

5. Mar 29, 2016

### foo9008

so , for this type of open pipe , the flow rate at 2 point are not the same ?

6. Mar 29, 2016

### haruspex

Not sure what you mean by a "type" of open pipe. It's not the type of pipe, it's the obstruction placed in the flow.

7. Mar 30, 2016

### foo9008

why this is not a type of pipe ? for open pipe system, teh flow rate at any 2 points of the pipe , wouldnt be the same , right ?

8. Mar 30, 2016

### haruspex

As I wrote, I'm not sure what you mean by a type of pipe. The presence of another pipe (the curved one) inserted into it does not, to me, make it a different type of pipe, merely a different arrangement. If I have two dogs of the same type, but one is chained up, I know which one will run faster. If you put obstructions in a flow then clearly the flow will not be the same at all points.

9. Mar 30, 2016

### foo9008

sorry , i left out something , the 'pipe' that inserted to the horizontal pipe is piezometer , which is used to measure pressure between 2 points... so , are the flow rate at 2 points same ?

10. Mar 30, 2016

### haruspex

The flow rate at the entrance to the piezometer clearly cannot be typical of the flow in the rest of the pipe. The water will flow into the piezometer only until the backpressure matches the pressure in the flow. At that point, no more water is flowing into it, so the flow right at its entrance must be zero.

11. Mar 31, 2016

### foo9008

do you mean when the water start flowing in , the flow rate at that instance may be equal to the flow rate at the rest of pipe , byt after sometime , water will stop flowing when the backpressure matches the pressure in the flow.so , at that instance , the flow rate reduced to 0 ?

12. Mar 31, 2016

Yes.