Measurement While Drilling, 2nd Edition

Chapter 9Siren Design and Evaluation in Mud Flow Loops and Wind Tunnels

We developed “short wind tunnel” analysis methods from a turbine design perspective in Chapter 8. In fact, we showed how from two simple measurements, namely, those for stall-torque and no-load rotation rate, each of which can be taken in minutes in inexpensive wind tunnels powered by simple blowers, the complete turbine torque and power versus rpm curves can be obtained for drilling mud of any density flowing at any speed. Here, we describe short wind tunnel design and test techniques further, in support of earlier turbine development ideas.

We also introduce mud siren design in short wind tunnels, in particular, analysis methods for stable-closed versus stable open, static versus dynamic torque, and erosion evaluation. “Short wind tunnels” are short, say, five to ten feet, and are used for hydraulic testing of properties that are independent of compressibility, e.g., torque, power, erosion, flow visualization, approximate viscous pressure drops and losses. On the other hand, acoustic properties like signal strength, harmonic content, and constructive and destructive wave interference, require not only longer wind tunnels that allow accurate simulation of wave interactions and reflections, but more sophisticated math models for data reduction, interpretation and extrapolation.

We will develop ideas for “intermediate length wind tunnels,” which are typically 100-200 feet, and also, for “long wind tunnels” ...