# find velocity in pipe

Watch
Announcements

Page 1 of 1

Go to first unread

Skip to page:

water flows from flow tank at A through cat iron pipeline to free surface at B . Given friction factor , f = 0.023, kinematic viscosity = 1.02 x10^-6 (m^2 0 /s , coefficient of losses for entrance , bend , valve = 0.5 , 0.9 and 10 . in this question , i am asked to find the velocity , flow rate , type of flow and pressure at A .for the first part , i'm asked to find the velocity . The flow rate is not given , how could the velocity be found ? Since Q = Av ,

i assume the flow as laminar at first , where reynold number less than 2000 ,so i have f = 64 / Re0.023 = 64(1.02 x10^-6)/ 1000 / ( 1000 x v x 150x10^-3) , v = 2.08x10^-8 , is my answer correct ? my reynold number is rather samll , which is 3.05 only , is it possible ?

i assume the flow as laminar at first , where reynold number less than 2000 ,so i have f = 64 / Re0.023 = 64(1.02 x10^-6)/ 1000 / ( 1000 x v x 150x10^-3) , v = 2.08x10^-8 , is my answer correct ? my reynold number is rather samll , which is 3.05 only , is it possible ?

0

reply

Report

#3

I'll have a look at this later, but I wouldn't assume laminar flow.

In terms of Bernoulli's equation, you know the pressure in the tank, you can assume the velocity is zero, and you know the elevation difference. That might be enough to calculate an entrance velocity for the pipe. You can also workout the pressure at that point, too.

In terms of Bernoulli's equation, you know the pressure in the tank, you can assume the velocity is zero, and you know the elevation difference. That might be enough to calculate an entrance velocity for the pipe. You can also workout the pressure at that point, too.

0

reply

(Original post by

I'll have a look at this later, but I wouldn't assume laminar flow.

In terms of Bernoulli's equation, you know the pressure in the tank, you can assume the velocity is zero, and you know the elevation difference. That might be enough to calculate an entrance velocity for the pipe. You can also workout the pressure at that point, too.

**Smack**)I'll have a look at this later, but I wouldn't assume laminar flow.

In terms of Bernoulli's equation, you know the pressure in the tank, you can assume the velocity is zero, and you know the elevation difference. That might be enough to calculate an entrance velocity for the pipe. You can also workout the pressure at that point, too.

0

reply

Report

#5

(Original post by

the problem is the pressure at A is unknown , so in the berboulli's equation , we would have 2 unknown , which are velocity and pressure at A , how to solve this ?

**wilson dang**)the problem is the pressure at A is unknown , so in the berboulli's equation , we would have 2 unknown , which are velocity and pressure at A , how to solve this ?

0

reply

(Original post by

A is open to the air is it not?

**Smack**)A is open to the air is it not?

Sent from my C6502 using Tapatalk

0

reply

Report

#7

(Original post by

We can see from figure, it is closed tank, right??

Sent from my C6502 using Tapatalk

**wilson dang**)We can see from figure, it is closed tank, right??

Sent from my C6502 using Tapatalk

0

reply

Well, I havre PA and v2 as unknown in an equation, how to solve this?

0

reply

(Original post by

If the tank is not open to the atmosphere and the air in it is pressurised, then ignore any atmospheric effects and just go by the gauge pressure of the water to calculate the velocity, flow rate and type of flow.

**Smack**)If the tank is not open to the atmosphere and the air in it is pressurised, then ignore any atmospheric effects and just go by the gauge pressure of the water to calculate the velocity, flow rate and type of flow.

Sent from my C6502 using Tapatalk

0

reply

Report

#10

(Original post by

Since b is open to atmosphere, so atmospheric pressure act on it., so I take atmospheric pressure =0

Sent from my C6502 using Tapatalk

**wilson dang**)Since b is open to atmosphere, so atmospheric pressure act on it., so I take atmospheric pressure =0

Sent from my C6502 using Tapatalk

0

reply

(Original post by

If B is open to the atmosphere, surely you can assume that A is also at atmospheric pressure, as taking gauge pressures only works when both sides are at the same atmospheric pressure as the two atmospheric pressures cancel out.

**Smack**)If B is open to the atmosphere, surely you can assume that A is also at atmospheric pressure, as taking gauge pressures only works when both sides are at the same atmospheric pressure as the two atmospheric pressures cancel out.

0

reply

Report

#12

(Original post by

ya , B is open to atmosphere , so stmospheric pressure act on it .... but b , the pressure act on it is not atmospheric pressure right ? since it's closed....

**wilson dang**)ya , B is open to atmosphere , so stmospheric pressure act on it .... but b , the pressure act on it is not atmospheric pressure right ? since it's closed....

0

reply

(Original post by

If the air can flow freely from the tank to the atmosphere then the air, and hence tank, could be said to be at atmospheric pressure. If there was no air in the tank and it was not pressurised then there would be no atmospheric pressure acting in it. But it appears you have to calculate the pressure at A as the last part of the question... I would clarify with your lecturer.

**Smack**)If the air can flow freely from the tank to the atmosphere then the air, and hence tank, could be said to be at atmospheric pressure. If there was no air in the tank and it was not pressurised then there would be no atmospheric pressure acting in it. But it appears you have to calculate the pressure at A as the last part of the question... I would clarify with your lecturer.

0

reply

Report

#14

(Original post by

so , the pressure at A is atmospheric pressure or pressurized pressure ????

**wilson dang**)so , the pressure at A is atmospheric pressure or pressurized pressure ????

0

reply

(Original post by

As per my post, you need to clarify this with your lecturer.

**Smack**)As per my post, you need to clarify this with your lecturer.

Sent from my C6502 using Tapatalk

0

reply

Report

#16

(Original post by

If that is pressurized pressure, then the question can't be done, right???

Sent from my C6502 using Tapatalk

**wilson dang**)If that is pressurized pressure, then the question can't be done, right???

Sent from my C6502 using Tapatalk

0

reply

X

Page 1 of 1

Go to first unread

Skip to page:

### Quick Reply

Back

to top

to top