I have been set a task to compare the differences between open circuit and closed-circuit wind tunnels, this I have managed to achieve. However, the task also asks to carry out a comparison of values.
(I have calculated values for the convergent-divergent section of the open return wind tunnel but we aren't given anything about a closed return wind tunnel, it's a theoretical question asking how the values would differ to those that might be found in a closed return wind tunnel of similar working section dimensions).

I myself would assume that the upstream velocity is lower in a closed return tunnel? Also resulting in the upstream pressure being higher in the closed return tunnel.

Would love some advice.