The test case geometry is a simple 2-D diverging duct. The bottom surface is flat. The top surface is flat for the first two inches, slopes upward linearly for the next four inches, then is flat for the last two inches. Thus there are straight inlet and exit sections, each two inches long, and a diverging middle section four inches long.

There is subsonic inflow at the inlet, and subsonic outflow at the exit. The top and bottom surfaces are inviscid (slip) walls.