Siren Design and Evaluation in Mud Flow Loops and Wind Tunnels - Measurement While Drilling Signal Analysis, Optimization and Design - page 230

Figure 9.2a. Short wind tunnel test system.
Figure 9.2b. Long wind tunnel system with pressure transducers
(see Figure 1.5b.1 for additional photos).
Gridding constraints and computer resources, for example, introduce errors
which do not allow the finest details of the flow to be modeled accurately;
however, the computer models are useful in identifying which engineering
concepts are worthy of more detailed experimental study. Properties related to
torque and open-closed stability, which are weakly dependent on viscous effects,
could be and were modeled quickly using the steady approaches of Chapter 7.