My Math Forum water flow problem

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March 23rd, 2018, 10:04 AM   #1
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water flow problem

Figure above shows a path of water pipe being measured in litre/seconds.

a) Create and solve the linear equation to find the quantity of water flow that may occur.
b) If water flow through AB is 5 litre/min, what will happen at other pipe branches?
c) What is the minimum and maximum water flow that may occur at each pipe branches?
d) Lets say if water flow is always positive. What is defined if the water flow is negative, imagine if it happen. Create a diagram to defined it.
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 March 23rd, 2018, 10:55 AM #2 Senior Member   Joined: Jun 2015 From: England Posts: 915 Thanks: 271 OK so what have you been taught about waterflow in pipes, branches and junctions (nodes)? Have you tried to write any equations using this?
 March 23rd, 2018, 07:28 PM #3 Newbie   Joined: Mar 2018 From: Singapore Posts: 5 Thanks: 0 is my equation correct? 20-f2=f1 10+f2=f3 f1+f3=30
March 24th, 2018, 01:52 AM   #4
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Quote:
 Originally Posted by carlluis is my equation correct? 20-f2=f1 10+f2=f3 f1+f3=30
Yes you have three correct equations for three unknowns so you can solve there.

However you will help yourself if you lay the problem out properly, particularly as you have further questions to answer.

Node equations:

At any node total flowing in = total flowing out.

or Total in - Total out = 0

So at A

20 -f1 - f2 = 0

At B

10 + f2 - f3 = 0

At C

f1 + f3 -30 = 0

Last edited by studiot; March 24th, 2018 at 01:57 AM.

 March 24th, 2018, 02:06 AM #5 Newbie   Joined: Mar 2018 From: Singapore Posts: 5 Thanks: 0 ok. thanks fr help. how about question C and D?
March 24th, 2018, 04:12 AM   #6
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Quote:
 Originally Posted by carlluis ok. thanks fr help. how about question C and D?
So this is where the statement of why you have written down the node equation as justification for your work.

Quote:
 At any node total flowing in = total flowing out.
There is a fixed flow into and out of the network of 30 units.

c)

So consider node A

The total flow is always the sum of 20, f1 and f2

What happens to the other flows if f1 is reduced to zero ?

What happens to the other flows if f2 is reduced to zero?

d)

The flows f1, f2 and f3 are the way you might have labelled the diagram to find them, with the arrows point in an assumed ( guessed ) direction.

If you get a negative value it means that the value is correct but the direction is wrong so you must reverse the arrow.

Now you can answer the question at node A

What happens if f3 is reduced to zero?

Last edited by studiot; March 24th, 2018 at 04:15 AM.

 March 28th, 2018, 05:00 PM #7 Newbie   Joined: Mar 2018 From: Singapore Posts: 5 Thanks: 0 can you show me detail on how to obtain f1, f2 and f3 for question 1.a). because i cant get any value by using gauss method

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