Siren Design and Evaluation in Mud Flow Loops and Wind Tunnels - Measurement While Drilling Signal Analysis, Optimization and Design - page 236

9.2 Short wind tunnel design
Siren testing need not be complicated or expensive. The sophistication
apparent in the system of Figure 9.2a is often not necessary. Short wind tunnels
are easily designed and fabricated - it is their use that is subject to subtlety. We
emphasize that mud sirens, turbines and strainers which are to be tested should
be built to full scale, and that the inner diameter of the plastic test section should
be identical to the inner diameter of the drill collar. The siren or turbine, plus
the central hub it is mounted on, should replicate that used in the MWD collar.
If different sections of plastic pipe are joined, care should be taken to prevent
leaks at the seams (and at blower-pipe junctions) since these would lead to
measurement errors for volume flow rates. The test sections should be made of
clear plastic tubing with non-reflective surfaces so that digital camera pictures of
test setups and flow visualization results (e.g., thread orientations) can be easily
obtained. The board upon which the wind tunnel is mounted should be painted
with black non-reflective paint to facilitate photographic and movie
documentation. Thus a digital camera, and preferably, a digital movie camera
and also a tripod, should be a permanent part of the wind tunnel system. The
basic wind tunnel, in its most rudimentary form, is illustrated in Figure 9.3 and
can be built for several hundred dollars.
Figure 9.3. Short wind tunnel in horizontal table-top position.