MEMS flexible thermal flow sensors for measurement of unsteady flow above a pitching wind turbine blade

Leu, Tzong Shyng; Yu, J.M.; Miau, Jiun‐Jih; Chen, S.J.

doi:10.1016/j.expthermflusci.2016.04.018

Cited by 29 publications

(24 citation statements)

References 31 publications

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“…However, they suffer from heat losses through the substrate on which the metallic wire is deposited. Various materials have thus been used to increased thermal insulation such as silicon nitride [16], glass [17] or flexible polymer ( [18], [19], [20]). These sensors, easy to mount flush to the wall, are often used for detecting flow separations and for wall shear stress measurement.…”

Section: Figure 1: (A) Schematic Of a Flow Separation On An Airfoil Lmentioning

confidence: 99%

High temperature gradient calorimetric wall shear stress micro-sensor for flow separation detection

Ghouila-Houri

Gallas

Garnier

et al. 2017

Sensors and Actuators A: Physical

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The paper describes and discusses the design and testing of an efficient and high-sensitive calorimetric thermal sensor to measure simultaneously the magnitude and the direction of wall shear stress in aerodynamic flows. The main technical application targeted is the back flow and the flow separation detection for active flow control. The measurement principle is based on the flow-induced forced heat convection transfer on a heater element. The sensor is micro-structured with three parallel substrate-free wires presenting a high aspect ratio and supported by periodic perpendicular SiO2 micro-bridges ensuring a mechanical toughness and a thermal insulation relatively to the bulk substrate with high thermal inertia. The central wire is made of a multilayer structure (Au/TiSiO2/Ni/Pt/Ni/Pt/Ni/SiO2) and is composed of a heater element (Au/Ti) and a thermistor (Ni/Pt/Ni/Pt/Ni) enabling to measure the heater temperature. The upstream and downstream wires are thermistors enabling to operate in the calorimetric mode. This design provides a high temperature gradient and a homogeneous temperature distribution along the wires. The sensor operates in both constant current mode and constant temperature mode, with a feedback on current enabled by uncoupling heating and measure. Welded on a flexible printed circuit, the sensor was flush mounted on the wall of a turbulent boundary layer wind tunnel. The experiments, conducted in both attached and separated flow configurations, demonstrate the sensor sensitivity to the wall shear stress up to 2.4 Pa and the ability of the sensor to perform flow direction sensing for back-flow detection in a separated flow configuration.

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Section: Figure 1: (A) Schematic Of a Flow Separation On An Airfoil Lmentioning

confidence: 99%

High temperature gradient calorimetric wall shear stress micro-sensor for flow separation detection

Ghouila-Houri

Gallas

Garnier

et al. 2017

Sensors and Actuators A: Physical

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“…In the study of Chabert et al [18] on the same model, the direct measurements from the hot-films were not enough to detect the separation and skewness and kurtosis calculations were needed. Other works, like the ones of Jiang et al [10] and Leu et al [4], needed the RMS value to accurately detect if the flow is separated or not. The main advantage of the present calorimetric MEMS transducers lies in the direct and accurate detection of separation thanks to the measurement of both the amplitude and sign of the wall shear stress.…”

Section: Active Flow Separation Control Experimentsmentioning

confidence: 99%

“…The array successfully detected the flow separation point. Leu et al [4] studied a pitching wind turbine blade equipped with 25 MEMS hot-films. All of them detected separation by mean values of output voltage but they needed the RMS value to get more precision.…”

Section: Introductionmentioning

confidence: 99%

High temperature gradient micro-sensors array for flow separation detection and control

Ghouila-Houri¹,

Talbi²,

Viard³

et al. 2019

Smart Mater. Struct.

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This paper reports the use of an array of calorimetric micro-sensors that perform bidirectional measurement of wall shear stress, for flow separation detection and control. The sensors design is hot-wire like with three parallel micro wires suspended over a micro-cavity and mechanically supported using periodic perpendicular micro-bridges. The micro-sensors were implemented on a flexible packaging and characterized in a turbulent boundary layer wind tunnel on a flat plate. An array of twelve microsensors were then implemented in a flap model designed for active flow control experiments and equipped with pulsed jet actuators. The work included the design and manufacturing of appropriate miniaturized electronics. Without control, the microsensors successfully detected the natural flow separation and the flow separation point moving from the trailing edge to the leading edge as the angle of the flap increased. Finally, the micro-sensors characterized the efficiency of the active flow control for avoiding separation.

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“…Most studies on thermal flow MEMS sensors present the sensor calibration in flat plate configuration and just a few of them use the MEMS sensors to detect complex flows such as flow separation (Xu 2003 [21], Buder 2008 [3], Leu 2016 [11]). Xu et al (Xu 2003 [21]) used a cylinder model with an array of MEMS hot-film sensors.…”

Section: Introductionmentioning

confidence: 99%

Unsteady flows measurements using a calorimetric wall shear stress micro-sensor

et al. 2019

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A microscale low power high temperature gradient calorimetric (HTGC) sensor measuring both mean and fluctuating bidirectional wall shear stress is presented. The micromachined sensor is composed of three freestanding 3 µm × 1 mm micro-wires mechanically supported using perpendicular micro-bridges. The static and dynamic characterisations were performed in a turbulent boundary layer wind tunnel on a flat plate configuration, and compared to the one obtained with a conventional hot-film probe. The results demonstrated that the calorimetric sensor behaves similarly to the hot-film in constant temperature anemometry with nonetheless lower power consumption and better spatial resolution and temporal response. Additionally, its calorimetric measurement detected the direction of the wall shear stress component orthogonal to the wires, corresponding to the shear stress sign in 2D flows. The

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MEMS flexible thermal flow sensors for measurement of unsteady flow above a pitching wind turbine blade

Cited by 29 publications

References 31 publications

High temperature gradient calorimetric wall shear stress micro-sensor for flow separation detection

High temperature gradient calorimetric wall shear stress micro-sensor for flow separation detection

High temperature gradient micro-sensors array for flow separation detection and control

Unsteady flows measurements using a calorimetric wall shear stress micro-sensor

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