[effort8]

Hello?

I would like to ask boundary condition of 2D Burgers equation.
I consider following equation.

U_{t} + ( (1/2)U^2 )_{x} + ( (1/2)U^2 )_{y} = 0

with the Riemann initial value

U(x,y,0)= 2.0 (x<0), 1.0 (x>0)

I guess that left and right boundary value is 2.0, 1.0 respectively.
But what is the top and bottom boundary condition?