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Hello, I'm new here - so apologies in advance if this is in the wrong place, also I haven't done physics for a few years prior to the course I just started - and I've never tried to write out formula in computer text, so apologies in advance again if everything I write is completely wrong! :tongue2:

A Farmer builds a water storage tank

[PLAIN]http://img408.imageshack.us/img408/6195/irrigationsystem.jpg [Broken]

The water is fed via a

Water Density: 1000kg/m3

Bernoulli's Equation:

Darcy Formula:

Moody Diagram

Right then, I've been asked to find the water flow rate, which I'm presuming means the

I haven't been given the

I've made a few assumptions with the Bernoulli Equation, which are that the

As well as this I've assumed that the

So at the moment, my

However I understand that this equation isn't full, as I also have to take into account the

So in order to accurately find the

But the

So in order to use the

Which somewhat puts me at a dead end.

Another route I was thinking of using to find the

However the only other

You can probably tell by now that I'm completely stumped by this - and as far as I know I'm probably doing it all completely wrong (it seems no matter what I try to do I always end up with a missing variable), so any help would be very much appreciated.

(Updated to include picture.)

## Homework Statement

A Farmer builds a water storage tank

**12m**above ground, as shown below:[PLAIN]http://img408.imageshack.us/img408/6195/irrigationsystem.jpg [Broken]

The water is fed via a

**200m**long,**125mm**diameter pipe to a field for irrigation purposes. The pipe has a friction factor of**0.008**. Using the K data below, show that the**water flow rate**(kg/s) in the pipe is approximately**26kg/s**__Data:__**K Factors:**Tank Exit 0.5, Bends 0.9 (x2), Valve 1.0 (Total: 3.3)Water Density: 1000kg/m3

## Homework Equations

Bernoulli's Equation:

*(P_1/ρ*g) + (V_1^/2*g) + z1 = (P_2/ρ*g) + (V_2^/2*g) + z2*Darcy Formula:

*H_f = 4*f*(L/D)*(V^/2*g)*Moody Diagram

## The Attempt at a Solution

Right then, I've been asked to find the water flow rate, which I'm presuming means the

**mass flow rate**(kg/s) - so in order to find that I need the**volume flow rate**, and in order to find that I need the**velocity**I haven't been given the

**velocity**in the original problem, however I think I need to use the**Bernoulli Equation**in order to find the**velocity**.I've made a few assumptions with the Bernoulli Equation, which are that the

**pressure at point 1**(the water tank) is atmospheric (**101325pa**) - because on the picture the tank looks to be open to atmosphere, I've also assumed that the**pressure at point 2**(the end of the pipe) is also atmospheric (**101325pa**) because the pipe is leading to a field.As well as this I've assumed that the

**velocity at point 1**is approximately**0m/s**(because the water is going from a large tank into a small pipe)So at the moment, my

**Bernoulli equation**looks like:*(101325 / (1000 x 9.81)) + (0^ / (2 x 9.81)) + 12 = (101325 / (1000 x 9.81)) + (V_2^ / (2 x 9.81)) + 0*However I understand that this equation isn't full, as I also have to take into account the

**friction (head loss)**, which would change the**Bernoulli equation**into:*(P_1/ρ*g) + (V_1^/2*g) + z1 = (P_2/ρ*g) + (V_2^/2*g) + z2 + h_f*So in order to accurately find the

**velocity**using the**Bernoulli equation**, I have to also take into account the**Head loss**?But the

**Darcy Formula**is:*H_f = 4*f*(L/D)*(V^/2*g)*So in order to use the

**Darcy Formula**I have to know the**velocity**- but I don't know the**velocity**(as that's what I'm trying to find)? - Unless there's a way of finding the**head loss**without knowing the**velocity**?Which somewhat puts me at a dead end.

Another route I was thinking of using to find the

**velocity**was to use the**Moody Diagram**to try to find the**Reynolds number**, then using*Re=(ρ*V*D)/μ*to find the**velocity**(as I know all the other values.)However the only other

**Moody diagram**value I know is the**Friction Factor**of**0.008**, and I'm unable to find the**Relative roughness**(k/D) as the problem doesn't state what sort of pipe is being used (so I can't find the roughness.)You can probably tell by now that I'm completely stumped by this - and as far as I know I'm probably doing it all completely wrong (it seems no matter what I try to do I always end up with a missing variable), so any help would be very much appreciated.

(Updated to include picture.)

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