Turns a PDE into an ODE to make it easier to solve. It is dimensionless. Used in the similarity-transformation.
Where is penetration depth thickness, is time to reach that depth, and is thermal diffusivity.
Covered in section 5.7 and in ME3304 S24 Lecture Note (2) Conduction.
6E - Class 2 - Transient Heat Transfer 2024-02-26 17_38_48 7A - 2nd Class 2024-02-26 17_38_49