[ano]

I am using the Sajben transonic diffuser problem from the NASA verification & validation data base for validation. Many studies are available on this, but (or because of this) the inlet boundary condition is quite unclear to me.

The total pressure and temperature are given and most authors assume that Mach M=0.9. The different boundary conditions in SI units are attached for different studies.

When I set static pressure, static temperature and the velocity at the inlet to Julianne Dudeks values, I got the built up of a boundary layer at the inlet, which resulted in a local acceleration and shock immediately behind the inlet. When I set static pressure, static temperature and zero gradient velocity, I get a Mach number around M=0.5 and similar results.

In the Mach contours by Wuethrich, Ye and Dudek, it seems as M=0.5 at the inlet, which is much below M=0.9:
Ye, Dotre, 2012
Wuethrich, 2007, Fig 4.11
Dudek, Carlson, 2017, Fig. 1

I find this confusing that people say M=0.9 at the inlet, but get M=0.5.

Does anyone have an explanation for it? Is this a convention I am not aware of to say that M=0.9 at the inlet and only use it to calculate pressure and temperature?


(There are also some other inconsistencies in the table, but my main concern is the one above)