MEMS-based pressure and shear stress sensors for turbulent flows

Löfdahl, Lennart; Gad‐el‐Hak, Mohamed

doi:10.1088/0957-0233/10/8/302

Cited by 140 publications

(85 citation statements)

References 73 publications

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“…Micro-machined flow sensors can be divided into two groups, based on different measurement methods: 'direct' measurement or 'indirect' measurement [6]. For direct measurement of wall shear stress, sensors usually use a floating element that is displaced laterally by the tangential viscous forces in the flow.…”

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

confidence: 99%

“…For example, micro-fences using a cantilever structure and piezoresistors are presented in [10]; the exploitation of optical resonances such as whispering gallery modes of dielectric microspheres is proposed in [11] (for which the optical resonance shifts with radial deformations of the spheres due to the shear stress); the deflection of micro-pillars is presented in [12] and thermal-based sensors are presented in the next paragraphs of the present paper. The physical principle used in these latter consists in taking advantage of the convective heat transfer between an electrically heated resistor and a surrounding cooler fluid [6]. As they do not involve a mechanical moving part, thermal flow sensors are widely adopted when dealing with fluid dynamics including laminar or turbulent flows.…”

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

confidence: 99%

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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%

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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“…Indirect shear-stress sensors are temperature-resistance transducers that operate on heat transfer analogies. Recently, Lo¨fdahl and Gad-el-Hak (1999) presented a review of MEMS pressure and shear-stress sensors for turbulent flows. Naughton and Sheplak (2002) expanded that contribution by providing an updated list of references and discussing some of the current misconceptions and controversies involving the use of MEMS-based shear-stress sensors for quantitative measurements.…”

Section: Performing Organization Name(s) and Address(es)mentioning

confidence: 99%

Dynamic calibration technique for thermal shear-stress sensors with mean flow

et al. 2005

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This paper presents the development of a dynamic calibration technique for thermal shear-stress sensors using acoustic plane wave excitation. The technique permits the independent variation in the mean and fluctuating shear stresses. The theoretical development and the practical implementation of the technique are presented. The studied configuration has the capability to dynamically calibrate shear-stress sensors up to 20 kHz. An illustrative application of this technique to an uncompensated silicon micromachined thermal shear-stress sensor operated in constant current mode is discussed. Specifically, the sensor has been statically calibrated over a range of wall shear stress from 7 to 80 mPa. A dynamic calibration of the sensor over a range of 2-12 mPa has been performed up to 7 kHz.

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“…This procedure is commonly called "electronic test" and is a widely accepted evaluation method for hot wire anemometers. Winter [10], Haritonidis [2], Naughton and Sheplak [11], and Löfdahl and Gad-el Hak [12] have presented studies that show that actual time responses of thermal shear stress sensors cannot be predicted by electronic tests alone, and therefore tests based on the variation of flow conditions must be applied. For this purpose we used a relatively simple rotating disk shear stress calibrator.…”

Section: Experimental Arrangementmentioning

confidence: 99%

Wall shear stress hot film sensor for use in gases

Osorio¹,

Silin²

2011

J. Phys.: Conf. Ser.

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-The dynamic response of a hot-wire anemometer: III. Voltage-perturbation versus velocity-perturbation testing for near-wall hot-wire/film probes B C Khoo, Y T Chew, C J Teo et al. Abstract. The purpose of this work is to present the construction and characterization of a wall shear stress hot film sensor for use in gases made with MEMS technology. For this purpose, several associated devices were used, including a constant temperature feedback bridge and a shear stress calibration device that allows the sensor performance evaluation. The sensor design adopted here is simple, economical and is manufactured on a flexible substrate allowing its application to curved surfaces. Stationary and transient wall shear stress tests were carried on by means of the calibration device, determining its performance for different conditions. IntroductionThe study of shear stress on the walls that make the boundary of a flow is an area of great interest in Fluid Mechanics and Heat Transfer. However its measurement is complex and is generally limited to experimental models. The measurement of wall shear stresses is relevant when studying the drag of blunt or aerodynamic objects, the pressure drop through conduits, the convective heat transfer of surfaces exposed to flows, etc., but it can also be used to detect the passage of fluid-dynamic structures such as hairpin vortices, vortex shearing behind obstacles or large scale coherent structures. Having a good temporal resolution in this kind of devices is of great interest, one reason for this is that the fluctuations of wall shear are relevant in the understanding of the flow and its effect on walls. In turbulent flows, the fluctuations of shear stress reach values as high as 0.46 of the mean wall shear stress [6]. The second reason is that a slow sensor exposed to a turbulent flow yields average measurement values that do not agree with the mean shear stress. That is, the average introduced by a slow sensor is not satisfactory, requiring therefore a turbulent calibration, i.e. a calibration under the same turbulence intensity that will be found in the case to be measured. To avoid such difficulties, it is necessary to obtain measurements with good temporal resolution and eventually to estimate the average value a posteriori.A technique for wall shear stress measurement that stands out for its simplicity of implementation and accuracy is the use of thermal sensors. Thermal sensors are heaters whose electrical resistance is a function of temperature, which in turn depends on the convection heat transfer between the sensor and the flow. A trend evident in all the measurement techniques of wall shear stress is that the sensors have their sensing areas ever smaller in order to improve the temporal and spatial resolution. In this process of miniaturization micro-electro-mechanical systems (MEMS) manufacturing technology has played a central role in shear stress sensor technology [7]. MEMS technology is based on the same technology developed for semiconductor device fabrication and is w...

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MEMS-based pressure and shear stress sensors for turbulent flows

Cited by 140 publications

References 73 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

Dynamic calibration technique for thermal shear-stress sensors with mean flow

Wall shear stress hot film sensor for use in gases

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