# Calculating Fluid Flow: Help with Q, A1, A2, Delta h, g & C

• tomtomtom1
In summary, the equation relates flow rates of fluids, Q, to area, A1 & A2, delta h, gravity, and discharge coefficient, C_d.
tomtomtom1
Hello all

I was hooping someone could help shed some light on the following:-

I have the equation shown below:

This equation relates to flow rates of fluids.

I know:-
Q = flow rate
A1 & A2 = Area
Delta h = Difference in Head Loss
g = Gravity

But what does C relate to or even mean?

Can anyone working in the field of hydro engineering or working with fluid flow help?

Thank you.

It looks a lot like this orifice flow equation:

Which is derived here: https://www.efunda.com/formulae/fluids/calc_orifice_flowmeter.cfm. I have not gone through the derivation myself, so don't know if swapping A1 and A2 changes it to match yours. Yours has head loss, which is equal to ##\Delta p / \rho##. The ##C_d## would be the discharge coefficient. Good search terms are orifice flow equation and orifice discharge coefficient.

The following are standard reference books that have sections on orifice calculations:
Perry's Chemical Engineers Handbook is currently in the 8th Edition. My 5th Edition has orifices, so the 8th should also.
Marks' Standard Handbook for Mechanical Engineers is currently in the 12th Edition. My 8th Edition has orifices, so the 12th should also.
Unit Operations of Chemical Engineering by McCabe and Smith is currently in the 7th Edition. My 3rd Edition has orifices, so the 7th should also.
And THE definitive source: ASME Fluid Meters Their Theory and Application. It's 273 pages of more than most people ever want to know about orifice, venturi, and other types of fluid meters.

Any of the above references is a better, and more complete, source of orifice flowmeter information than any of the web sites that I found. It makes a difference whether the flow is incompressible, compressible, or sonic. And these sources go into the details of which equation to use in each case.

Nitpick: It's head loss or pressure drop or pressure difference, but not difference in head loss.

Can you provide the source of your equation?

## 1. What is fluid flow and why is it important to calculate?

Fluid flow is the movement of a liquid or gas through a system or object. It is important to calculate because it helps us understand and predict the behavior of fluids in various situations, such as in pipes, pumps, and engines.

## 2. What is Q and how is it related to fluid flow?

Q, also known as flow rate, is the volume of fluid that passes through a given point in a certain amount of time. It is directly related to fluid flow, as it represents the amount of fluid that is moving through a system.

## 3. How do I calculate A1 and A2 in fluid flow?

A1 and A2 refer to the cross-sectional areas of the fluid flow at two different points in a system. To calculate these, you will need to measure the diameter or radius of the pipe or object at each point and use the formula A = πr^2 to find the area.

## 4. What is Delta h and how does it affect fluid flow?

Delta h, also known as the change in height or head, is the difference in height between two points in a fluid system. It affects fluid flow by creating a pressure difference, which causes the fluid to move from a higher to a lower height.

## 5. What do g and C represent in fluid flow calculations?

g represents the acceleration due to gravity, which is a constant value of 9.8 m/s^2. C, also known as the discharge coefficient, is a dimensionless factor that accounts for the efficiency of a system in converting potential energy into kinetic energy. It is often determined experimentally and varies depending on the type of system.

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