# How to calculate the required SimScale Inlet velocity and Air property values in order to match Mach and Reynolds Numbers of wind tunnel conditions

When using NACA0012 experimental data from NASA TM4074, it has proven difficult to determine suitable values for SimScale Inlet velocities and Air properties such that the Reynolds Number and Mach Number for a Simulation Run match the Re and Mach of the wind tunnel data.

Recently I have come across this article which describes the necessary equations and techniques which can be used to help in this matter:
Andrew Ning ReMatching.pdf

Using the article, I have created a spreadsheet that allows the user to enter the Chord, a desired Mach, Re, Temp and Density which outputs the Inlet Speed and Kinematic Viscosity for SimScale use.

Here is an image of my spreadsheet with input values set so that I can see if the spreadsheet matches the NASA Re calculator :

And here is the NASA Re calculator whose output seems to match my above spreadsheet values :

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And finally, here is my spreadsheet with input values that give me SimScale values to match exactly the Re 3.9M and Mach 0.15 of the NASA TM4074 tunnel run on the NACA0012 data that I want to verify with my SimScale CFD project:

As long as our Temp and Pressure values are inside the range of Temps and Pressures that the Langley LTPT Tunnel can achieve, then these are the required inputs for SimScale use

With a geometry file that has a 1m chord, my inputs to SimScale to match Re3.9M and M0.15 under T and P conditions that are obtainable at Langley are:

1. Inlet Velocity 58.924 m/sec
2. Air Density 1.2280 kg/m^3
3. Kinematic Viscosity 1.5109E-5 m^2/sec

You can find my spreadsheet file in this Google Drive folder (and other goodies )

# I think that might be good advice for all my future external CFD simulations!

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Good job (again) Dale! Will definitely go over it if I have the time! Maybe someone else can make use out of it in the meantime.

Cheers and thanks for sharing!

Jousef

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This is just a topic bump to see if anyone will go over it and report back here on my spreadsheetsâ€™ validity.