Recent Innovations in Wall Shear Stress Sensor Technologies

Etebari, Ali

doi:10.2174/2212797610801010022

Cited by 11 publications

(2 citation statements)

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“…The absence of electronic connections at the device location mitigates susceptibility to electromagnetic interference (EMI). 12 Environmental factors such as humidity and temperature can cause measurement drifts in the capacitive and piezoresistive techniques. The challenge for optical techniques is to develop a robust package capable of wall shear stress measurements in realworld applications.…”

Section: Introductionmentioning

confidence: 99%

A miniaturized optical package for wall shear stress measurements in harsh environments

et al. 2014

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We report the development of a time-resolved direct wall shear stress senor using an optical moiré transduction technique for harsh environments. The floating-element sensor is a lateral-position sensor that is micromachined to enable sufficient bandwidth and to minimize spatial aliasing. The optical transduction approach offers several advantages over electrical-based floating element techniques including immunity from electromagnetic interference and the ability to operate in a conductive fluid medium. Packaging for optical sensors presents significant challenges. The bulky nature and size of conventional free-space optics often limit their use to an optical test bench, making them unsuitable for harsh environments. The optical package developed in this research utilizes an array of optical fibers mapped over the moiré fringe. The fiber bundle approach results in a robust package that reduces the overall size of the optics, mitigates vibration between the sensor and optoelectronics and enables in situ measurement. The optical package for sampling the amplified moiré fringe is evaluated using bench top test setups. An optical test bench is constructed to simulate the movement of the moiré fringe on the floating element. High-resolution images of the optical fringe and optical fibers are combined in simulation to model the lateral displacement of the fringe. The performance of several fringe estimation algorithms are studied and evaluated. Based on the optical study, the optical package and post-processing algorithms are implemented on an actual device. Initial device characterization using this approach results in a device sensitivity of 12.4 nm/Pa.

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Section: Introductionmentioning

confidence: 99%

A miniaturized optical package for wall shear stress measurements in harsh environments

et al. 2014

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“…Measurement of the shear stress at a wall in a fluid is indispensable for understanding the flow dynamics and for its active control. 1 Many flow phenomena involve small-scale structures, such as a boundary layer. The boundary layer thickness decreases as the Reynolds number of the flow increases.…”

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confidence: 99%

Flexible MEMS Shear Stress Sensor with Improved Performance for Wind Tunnel Measurements

Wang

Fan

et al. 2019

J. Electrochem. Soc.

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This paper describes a flexible micro-electro-mechanical system (MEMS) shear stress sensor, fabricated on a polyimide substrate using sputtering and a lift-off technique. The width of the nickel thermistor is minimized to several microns by an optimized manufacture process. The performance of the nickel thermistor is notably enhanced by heat-treatment during the fabrication. The sensor's characteristics are tested, including the temperature coefficient of resistance (TCR), time constant (cutoff frequency), and sensitivity. As a result of the optimized fabrication and the appropriate annealing heat-treatment, the TCR of the nickel thermistor is high, which has a considerable effect on the sensitivity; these techniques and results are an improvement on results in literature. The cutoff frequency test and sensitivity calibrations of the sensor were performed in a wind tunnel. The results show that the improved sensor with higher TCR and smaller size can be used in wind tunnel measurements effectively.

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Application of the Electrodiffusion Method to Measure Wall Shear Stress: Integrating Theory and Practice

et al. 2014

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The electrodiffusion method has been used in fluid dynamic research for the past 50 years. It allows the measurement of wall shear stress, a crucial parameter, e.g., for the cleaning of membrane modules used in water filtration. Various authors have published articles dealing with the theory behind this technique. But no paper collects all the knowledge assembled over five decades of application. Here, comprehensive summary of the theory of steady flow, unsteady flow, and transient voltage step experiments is given. Factors influencing the accuracy of the measurements are discussed. Furthermore, a new approach to calibrate the system from voltage step experiments is introduced, and practical issues related to its application in flow measurements are discussed for an exemplary signal response to a near‐wall flow.

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Recent Innovations in Wall Shear Stress Sensor Technologies

Cited by 11 publications

References 0 publications

A miniaturized optical package for wall shear stress measurements in harsh environments

A miniaturized optical package for wall shear stress measurements in harsh environments

Flexible MEMS Shear Stress Sensor with Improved Performance for Wind Tunnel Measurements

Application of the Electrodiffusion Method to Measure Wall Shear Stress: Integrating Theory and Practice

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