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University of Wyoming

UW Technologies Available for Licensing


Technology Disclosure: 03-024 A Dynamic Resonant Surface Fluidic Shear Stress Sensor


Background

Although it has been studied for more than 100 years, the measurement of fluctuating wall shear stress is one of the great unsolved problems in fluid mechanics. The inability to measure both mean and fluctuating shear stress limits our understanding of basic flows and inhibits the development of flow control applications. Unfortunately, the development of a calibrated sensor capable of measuring fluctuating shear stress is still elusive. Even the expected improvements in sensors developed with new materials and manufacturing processes over the past 15 years (mostly through miniaturization) have not come to pass because of the problems that arise when working in smaller scales (like reduced transduction signal to noise). In short, simply taking the conventional concepts and making them smaller has not worked to expectations.

This creates a need for a robust, calibrated shear stress sensor capable of providing mean and fluctuating shear stress measurements in all kinds of flows (attached, separated, dirty, opaque, variable or unknown composition, etc.).


Summary

Researchers in the University of Wyoming’s Mechanical Engineering Department have designed and constructed a prototype for a shear stress sensor based on an entirely new sensing approach. Specifically, our researchers employ a resonant dynamic sensor. Dynamic systems operating at or near resonance are very sensitive to small changes in forces. This sensor is specifically designed such that shear stress on the surface of the sensor acts to dampen the resonant system. By measuring changes in the resonance, the surface shear stress can be determined. The benefits of this new design over static force balance sensors are immediately apparent. Other forces, such as pressure differences across the sensor due to pressure gradients, do not affect the dynamic motion and thus do not affect the sensitivity to surface shear stress. All told, our device has high sensitivity to shear stress, low sensitivity to other forces (like pressure gradients), high bandwidth, small size, good temporal resolution, the ability to be assembled into multi-directional arrays, and the ability to be combined with actuators in a closed-loop system. This type of device can measure fluctuating wall shear stress in challenging environments (dusty), and on all kinds of surfaces, a task that has not been accomplished in the past. University of Wyoming researchers are currently obtaining excellent results with the prototype device under open-loop and closed-loop operation. These results were presented in two papers at the 24th AIAA Aerodynamic Measurement Technology conference to be held in Portland Oregon June 28th 2004.  The University of Wyoming also has a pending patent on this technology 2004/106844.
 

Applications

An instrument that can measure shear stress on a wall can be applied to virtually any application that involves fluids moving past a surface. Potential applications include pipelines, airplanes, and even the human body to measure wall shear stress on arteries. Researchers feel that this technology has many applications in the aerospace, chemical, and bio-medical industries.

If you would like to know how your company can assist in its continued development, or even license the technology for commercial use feel free to contact Davona Douglass. We would be happy to discuss this opportunity with you further and provide you with more detailed information.


References

Zhang, W.D. Armstrong, W.R. Lindberg, and J.W. Naughton, “Numerical Model of a Dynamic Resonant Shear Stress Sensor,” AIAA Paper 2004-2395.

W. D. Armstrong, A. Singhal, and J.W. Naughton, “A Dynamic Resonant Shear Stress Sensor,” AIAA Paper 2004-2608