Zones 1 and 2 are the bottom and top halves of the upstream half of the duct, and zone 3 is the downstream half of the duct. The y = 0 symmetry plane is the lower boundary of zones 1 and 3. Thus, the upper boundary of zone 1 couples to the lower boundary of zone 2, and the downstream boundaries of zones 1 and 2 both couple to the upstream boundary of zone 3.

Last updated 2 May 2003