[cfdnewb123]

For example for a 2D system,
dU/dt + dF/dx + dG/dy =0

For directional splitting in each time step (assume Euler method), I need to use a 1D Riemann solver to calculate F to update U before applying the 1D Riemann solver to compute G and update U.

But what about unsplit method? Is it just one 2D Riemann solver to compute both F and G and thus, I only need to update U once?

In that case, the difference just lies in the type of Riemann solver used?