Siren Design and Evaluation in Mud Flow Loops and Wind Tunnels - Measurement While Drilling Signal Analysis, Optimization and Design - page 228

9.1.3 Background, early short wind tunnel.
Whereas the “long wind tunnel” is used to evaluate pulser acoustic signal
strength, wave propagation, reflections, telemetry schemes, constructive and
destructive wave interference, surface signal processing schemes, and so on, the
“short wind tunnel” is used to study properties like mud siren torque and power,
turbine torque and power properties, strainer erosion, jamming due to debris,
viscous flow separation, streamline pattern, and so on.
Because fluid compressibility and sound reflections are unimportant for
these purposes at typical mud pump flow rates, the wind tunnel does not need to
be long. It can be short, say ten feet or less, just long enough that three-
dimensional blower inlet and outlet end effects are unimportant. The author's
earliest wind tunnel is shown in Figure 9.1 for historical purposes. This 1980s
vintage design met only the bare minimum requirements for “wind” and
“tunnel,” with a simple squirrel cage blower attached to plastic tubes mounted
on a table-top - a very crude design, built for several hundred dollars literally
overnight, which nonetheless proved useful for testing. Its importance, of
course, was strategic, setting the groundwork for the methods described in
Chapter 1 that have since been adopted by numerous organizations.
Figure 9.1. Very early (historical) short wind tunnel.
Wind tunnel usage in downhole applications was widely adopted soon after
its initial usage. In “Flow Distribution in a Tricone Jet Bit Determined from
Hot-Wire Anemometry Measurements,” SPE Paper No. 14216, by A.A.
Gavignet, L.J. Bradbury and F.P. Quetier, presented at the 1985 SPE Annual
Technical Conference and Exhibition in Las Vegas, and in “Flow Distribution in
a Roller Jet Bit Determined from Hot-Wire Anemometry Measurements,” by
A.A. Gavignet, L.J. Bradbury and F.P. Quetier, SPE Drilling Engineering,
March 1987, pp. 19-26, the investigators, following ideas suggested by the lead
author, showed how very detailed flow properties can be obtained using
aerospace wind measurement methods. The reader is referred to these papers
for descriptions of the improved set-ups. For siren and turbine test objectives,
however, the three-dimensional methods developed there are not necessary.