rhoCentralFoam velocity definition
 

Hi guys,
I'm new to the forum and openFOAM. I've been following a youtube tutorial on the supersonic wedge case using rhoCentralFoam: https://www.youtube.com/watch?v=6jLn5cSCkd8

It seems they're specifying the airflow velocity in the boundary conditions at 5m/s. However, once the simulation has been executed the resulting Mach number is calculated to be about 5.
My question is, how does 5 m/s translate to Mach 5? Are they manipulating the Reynolds number?

Thanks!

Hello,

the local speed of sound depends on the specific gas constant, temperature and isentropic coefficient. As you change the fluid properties, you can achieve Ma = 1 at conditions like U = 1m/s and T = 1K.

Just have a look at the settings in the thermophysicalProperties file in the constant folder.

Kind regards,

Martin

Thank you Martin- that makes sense.
So, am I correct to assume the specific gas constant is calculated from the gas constant and molar mass; and the isentropic coefficient is 1.4 (for ideal gas)?
Also, does this case simulate an actual real-life gas (molar mass 11.6403 kg/mol; Cp =2.5) or are these numbers just randomly defined to simulate high Mach with low U conditions?
Thanks again!
Greg