LaxFriedrichs flux
Have anyone a paper which explain how laxfriedrich(approximate riemann solver) is derived?
Also if we suppose that (u+) is the values of a volume , (u) the values of neighbour volumes and F the flux then the laxfriedrichs flux gives: F=0.5*( (F+) + (F) )  a*( (u)  (u+) ) This is applied by all faces of a initial volume regardless of its outward unit vector? 
There's nothing too fancy about the LFflux....its the average, penalized by the jump to add a strong dissipative constant.... not sure about the original paper, anybody has a hint???
you compute your F by the formula given above, and then do int (F*n) dx to take the normal into account... hope this helps a bit! 
Yes , sure. The third term is the dissipative term. Simply , i did not know if it has a complex theory under of it (due to appearance of eigenvectors as dissipative multiplier). With other words, i want to learn what assumptions do for to solve approximate the Riemann problem and finally result at this simply relation.
For other cases as HLLC or HLL there is a assumption on a number of waves. Here? 
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