essence of upwinding
 

I EVER believed that upwinding is an effective means to introduce numerical dissipation into the scheme. It is also this numerical dissipation that makes upwinding diserable in shock capturing.

-Are these claims correct?

However, as we known, Lax-Friedrichs is a contral method, and it is more dissipative than the first-order upwind scheme.

How to justify the effect of upwinding of a numerical scheme? For dissipation or for the correct influence domain?

Re: essence of upwinding
 

Both claims are correct!

In my opinion, dissipation and influence domain go hand in hand (please read my post below yours, which tries to explain inviscid drag).