Initial/Boundary Conditions Setup

Cases
1

A few quick general questions:

When defining your initial and boundary conditions. How do you scale your parameters such that u = 1, etc? For example, in the test case for triangular airfoil, we have:
[soln-bcs-inlet]
type = char-riem-inv
rho = 1
u = 1
v = 0
w = 0
p = 31.74603174603175

What exactly does this mean? If we were converting to metric, how would this apply? Also, how are you able to determine Mach number of flow if there is no temperature input?

2

We typically scale geometry characteristic length, density, and velocity to 1 and set the pressure/viscosity to obtain the correct Mach and Reynolds numbers. For Mach, M = u/c = u/sqrt(gamma*P/rho), which gives us P = rho * u^2/(gamma * M^2) which equals 1/(gamma*M^2) if density and velocity are 1. Similarly, Re = rho * u * L / mu so mu = rho * u * L / Re which equals 1/Re if your density, velocity, and geometry characteristic length are 1.

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