Gas Flow, Weir Flow, and AI Accuracy in Flow Calculations

LMNO Engineering newsletters

2026
February 9, 2026. Gas Flow Calculators
March 27, 2026. Artificial Intelligence (AI) and Flow Calculations

LMNO Engineering, Research, and Software, Ltd.
The fluid flow calculations website: https://www.LMNOeng.com
7860 Angel Ridge Rd. Athens, Ohio 45701 USA (740) 707-2614
LMNO@LMNOeng.com

Newsletter. February 9, 2026.

Gas Flow Calculators

Since we have many gas flow calculators for different purposes, I will describe their applications.

https://www.LMNOeng.com/Flow/weymouth.php - This calculator determines flow rate and pressure loss in long, constant diameter gas transmission pipelines that extend for several miles or kilometers. It incorporates gas compressibility and captures how changes in pressure affect both gas density and velocity within a pipeline of fixed diameter.

https://www.LMNOeng.com/Gas/choke.php - This calculator models choked compressible gas flow from a tank to a pipe with discharge to the atmosphere or a reservoir. It determines velocity, Mach number, temperature, pressure, and density at the pipe inlet and outlet.

https://www.LMNOeng.com/Gas/GasLeakRate.php - This calculator predicts the steady flow rate of a gas from a leak in a pipeline or tank that remains at constant pressure. It models both sonic and subsonic conditions.

https://www.LMNOeng.com/Depressure/gas-tank-depressurization-time.php - This is our newest calculator, which we added in 2025. It determines the time for a tank to depressurize. It models both isothermal and isentropic flow conditions for both sonic and subsonic flow. It also includes tabular and graphical results of pressure versus time as the tank depressurizes.

https://www.LMNOeng.com/Flow/SmallOrificeGas.php and https://www.LMNOeng.com/Flow/OrificeGas.php - These two calculators are for orifice flow meters for measuring gas flow rate in a pipe. They offer dropdown menus to compute flow rate, pressure drop, or diameter sizing. SmallOrificeGas is for pipe diameter less than 5 cm while OrificeGas is for 5 cm or larger.

https://www.LMNOeng.com/Flow/GasFlow.php - This handy calculator converts between gas volumetric and mas flow rates.

https://www.LMNOeng.com/Flow/GasViscosity.php - This calculator computes the viscosity for various gases based on their temperature.

Please let me know if questions. Thank you for your interest in the LMNO Engineering newsletter,

Ken Edwards, Ph.D., P.E. (Owner/Engineer)
LMNO Engineering, Research, and Software, Ltd.
https://www.LMNOeng.com LMNO@LMNOeng.com

You received this free newsletter because you requested it at our website. If you no longer wish to receive it, send a message stating
"Discontinue Newsletter" to LMNO@LMNOeng.com.

Artificial Intelligence (AI) and Flow Calculations

Artificial Intelligence (AI) seems to be the first result to appear on Google and other search engines. It also is widely promoted by companies for use by their employees.

If, like me, you have tested AI against known results for scientific calculations, then you may be aware of its arithmetic limitations. Most AI programs do not actually do arithmetic. They simply have crowd-sourced the vast amount of information on the worldwide web and rely on pattern prediction. AI is programmed to look for the next most-likely character in a word or in a number. Only some AI programs have computer code (e.g. python) built into their algorithms. Most do not perform actual arithmetic in the same way one would use a calculator or spreadsheet.

For example, I typed the following into Copilot:.

Water flows over a 70 degree V-notch weir. The head on the weir is 1 foot. What is the flow rate in cubic meters per second?

Copilot correctly converted 1 ft to 0.3048 m. It used the correct flow equation:

Q = C (8/15) tan (θ/2) (2g)^0.5 H^2.5

It selected a reasonable discharge coefficient C of 0.58. It correctly used degrees in the tangent function and correctly computed the individual terms. However, it computed 0.10 m³/s for the flow rate. Unfortunately, 0.10 m³/s is incorrect.

Q = (0.58) (8/15) tan(70^o/2) [(2)(9.81 m/s²)]^0.5 (0.3048 m)^2.5 = 0.0492 m³/s

When I put the same question into Google, Google showed the result using its Gemini AI program. Gemini presented the answer of 0.0496 m³/s which is pretty good considering that AI does not actually perform arithmetic.

We have a free V-notch weir calculator, so feel free to run your own tests https://www.LMNOeng.com/Weirs/vweir.php

Note that the equation on our page uses the U.S. Bureau of Reclamation form of the flow equation where (8/15) (2g)^0.5 is combined into one term having a value of 4.28 (where g has units of ft/s²).

I encourage everyone to check the results of AI programs. AI can be very useful, but can make serious mistakes jeopardizing the feasibility and safety of projects.

Please let me know if questions. Thank you for your interest in the LMNO Engineering newsletter,

Ken Edwards, Ph.D., P.E. (Owner/Engineer)
LMNO Engineering, Research, and Software, Ltd.
https://www.LMNOeng.com LMNO@LMNOeng.com

You received this free newsletter because you requested it at our website. If you no longer wish to receive it, send a message stating
"Discontinue Newsletter" to LMNO@LMNOeng.com.

LMNO Engineering, Research, and Software, Ltd.
7860 Angel Ridge Rd. Athens, Ohio 45701 USA Phone: (740) 707‑2614
LMNO@LMNOeng.com https://www.LMNOeng.com