# Calculate Reynolds Number for 0.3m Diameter Pipe Flow

• tomwilliam
In summary, the Reynolds number for a pipe with a diameter of 0.3m and water flow rate of 71 m/s is estimated to be approximately 27 million. This suggests that the flow is likely to be turbulent. Possible sources of error include using the pipe diameter as the length and potential inaccuracies in the calculated flow speed. However, a similar result was obtained using an online Reynolds number calculator.
tomwilliam

## Homework Statement

Estimate a reynolds number for a pipe of 0.3m internal diameter, carrying water at a rate of 71 m/s, and say what that says about the likely nature of the flow.

## Homework Equations

Re = (density x L x velocity of flow)/coefficient of dynamic viscosity for water
Viscosity of water = 8.9 x 10^-4 kg/m s
density of water = 1000 kg/m^3

## The Attempt at a Solution

Well, I have produced a result of some 27 million, which seems excessive to me. Possible mistakes: I used the diameter of the pipe as L. Also, the flow speed is something I calculated in a previous question, so could potentially be wrong. The speed is just due to potential energy coming from a reservoir exactly 500m higher up, where pressure is atmospheric only.
Does anything sound wrong with this solution? I have no reference for typical reynolds numbers in these situations...

I got a similar result.

Thanks - In that case I'd better check that I've got the right flow speed for a height difference of 500m and a diameter of 0.3m.

I just used one of those on-line RN calculators--I got 23.9 million which is close, esp in the world of Reynolds numbers--certainly the answer to the next question will be the same.

## 1. What is the formula for calculating Reynolds Number for 0.3m Diameter Pipe Flow?

The formula for calculating Reynolds Number for 0.3m Diameter Pipe Flow is Re = (ρ*V*D)/µ, where Re is the Reynolds Number, ρ is the density of the fluid, V is the velocity of the fluid, D is the diameter of the pipe, and µ is the viscosity of the fluid.

## 2. How do you determine the density and viscosity of the fluid?

The density and viscosity of the fluid can be determined through laboratory experiments or by consulting a fluid properties table based on the type of fluid being used in the pipe flow.

## 3. What units should be used for the inputs in the Reynolds Number formula?

The inputs in the Reynolds Number formula should be in SI units: density (kg/m^3), velocity (m/s), diameter (m), and viscosity (Pa*s).

## 4. What is the significance of Reynolds Number in pipe flow?

Reynolds Number is an important dimensionless quantity that helps determine the type of flow (laminar or turbulent) in a pipe and predicts the behavior of the fluid in the pipe. It is also used to determine the pressure drop and pumping power required for the fluid flow.

## 5. What is the range of Reynolds Number for laminar and turbulent flow in a 0.3m diameter pipe?

In general, a Reynolds Number below 2300 indicates laminar flow, while a Reynolds Number above 4000 indicates turbulent flow. In the range of 2300-4000, the flow can be either laminar or turbulent, and this transition zone is known as the critical zone.

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