Can anyone provide clarification on the following plot

[R_AP_22]

Homework Statement

I was given a plot and a citation, but not too much clarification on what it represents. I believe it is describing mass transfer in a boundary layer.

Can anyone clarify

Homework Equations

J. P. Hartnett and E. R. G. Eckert, Trans. ASME, 13, 247 (1957).

The Attempt at a Solution

 

[Chestermiller]

I think it represents mass transfer in flow past a flat plate in which mass is also being introduced by flow through the porous plate.