# Reynolds 10^5 & Hazen-Williams Friction Model: Is There a Problem?

• Clausius2
In summary, the Hazen-Williams friction model may fail in a hydraulic circuit due to its empirical nature and limited applicability under certain conditions. It has been shown to provide unrealistic results in some cases, and other models such as Darcy may need to be considered as alternatives.
Clausius2
Gold Member
Is there some reason for Hazen-Williams friction model to failure in a hydraulic circuit?.

I have simulated an hydraulic system in a commercial code, and this model is the unique which gives stupid results like infinite volumetric rates. The Reynolds is about 10^5.

My reference as well as the website here (http://www.piping-toolbox.com/6_797.html) show that you are right on the edge of $$R_e$$ for using Hazen-Williams. Also, are you possibly outside the realm of this:
Note that the Hazen-Williams formula is empirical and lacks physical basis. Be aware that the roughness constants are based on "normal" condition with approximately 1 m/s (3 ft/sec).

I guess after we discount those two notions, the model will have to go under the microscope. Is there any way to compare your model to Darcy?

Last edited:
FredGarvin said:
My reference as well as the website here (http://www.piping-toolbox.com/6_797.html) show that you are right on the edge of $$R_e$$ for using Hazen-Williams. Also, are you possibly outside the realm of this:

I guess after we discount those two notions, the model will have to go under the microscope. Is there any way to compare your model to Darcy?

It doesn't help too much, but thanks anyway .

The problem is I have to switch between friction models when calculating an hydraulic installation, but this model is the unique which spends the longer computational time and gives unbelievable results. I was searching for same sort of conditions in which this formula is applicable, but I haven't found nothing interesting for justifying this fact.

## What is the Reynolds 10^5 & Hazen-Williams Friction Model?

The Reynolds 10^5 & Hazen-Williams Friction Model is a mathematical equation used to calculate the frictional resistance of water flowing through a pipe. It takes into account factors such as pipe roughness, flow rate, and pipe diameter to determine the head loss in the system.

## How accurate is the Reynolds 10^5 & Hazen-Williams Friction Model?

The accuracy of the model depends on the specific conditions of the system. It is generally considered to be accurate for systems with a Reynolds number between 10^5 and 10^8. However, it may not be as accurate for systems with very high or very low flow rates.

## What are the limitations of the Reynolds 10^5 & Hazen-Williams Friction Model?

One of the main limitations of the model is that it does not take into account the effects of turbulence in the flow. It also assumes that the pipe is smooth and the flow is steady, which may not always be the case in real-world systems. Additionally, it may not be accurate for systems with non-Newtonian fluids or complex geometries.

## In what situations should the Reynolds 10^5 & Hazen-Williams Friction Model be used?

The model is commonly used in engineering and design projects for water distribution systems, as well as in the analysis of open channel flow. It is a good option for relatively simple systems with moderate flow rates and smooth pipes.

## Are there alternative models to the Reynolds 10^5 & Hazen-Williams Friction Model?

Yes, there are several other models that can be used to calculate head loss in a pipe or channel, such as the Darcy-Weisbach equation or the Manning equation. The choice of model depends on the specific characteristics of the system and the desired level of accuracy.

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