Although not exactly a structured course or lessons, FEATool has been designed to be a very easy to use toolbox for physics simulations and learning by experimentation and trial and error with built-in tutorials (currently free license for home use during the lockdowns [1]), for fluid flow and heat transfer the simpler CFDTool might be more appropriate with an even simpler interface that "hides" the underlying PDEs [2].

[1] https://www.featool.com [2] https://www.cfdtool.com