Detecting boundary-layer separation point with a micro shear stress sensor array

Liu, Kui; Yuan, Weizheng; Deng, Jinjun; Ma, Binghe; Jiang, Chengyu

doi:10.1016/j.sna.2006.11.008

Cited by 20 publications

(14 citation statements)

References 3 publications

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“…however, most of them will greatly interfere with fluid flow during measurement (Zhang et al 2008). Miniaturized shear stress sensors fabricated using MeMS technology offer superior spatial resolution, fast time response and minimized interference with fluid flow (liu and Yuan 2007;liu and Zhu 2009;Beutel et al 2013a). Therefore, MeMS sensors will play an important role for studying gaseous or liquid fluid flows experimentally.…”

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confidence: 99%

Improved sensitivity of micro thermal sensor for underwater wall shear stress measurement

Zhu

Jiang

et al. 2014

Microsyst Technol

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Knowledge of such wall shear stress is essential for understanding the dynamics of the fluid flow, and its measurement holds great importance for investigating and controlling wall-bound turbulence and flow separation (Bellhouse and Schultz 1966;Goldstein 1996;Kimura et al. 1999;lin et al. 2005;Wang et al. 2007;Sturm et al. 2012). Presently, there are many measurement techniques for shear stress. however, most of them will greatly interfere with fluid flow during measurement (Zhang et al. 2008). Miniaturized shear stress sensors fabricated using MeMS technology offer superior spatial resolution, fast time response and minimized interference with fluid flow (liu and Yuan 2007;liu and Zhu 2009;Beutel et al. 2013a). Therefore, MeMS sensors will play an important role for studying gaseous or liquid fluid flows experimentally.Micro thermal shear stress sensors are based on measurement of heat transfer from a heated thin-film element to the fluid flow (Osorio and Silin 2011). constant current (cc) mode can be used to drive them. There are many reported thermal shear-stress sensors working in cc mode. The shear-stress sensitivity of a micromachined thermal shear stress sensor reported by chang liu is 15 mV/Pa at a power consumption of 12 mW (I = 2 ma) when the shear stress input was about 0.2 Pa (liu et al. 1994). Mark Sheplak has presented a characterization of a silicon-micromachined thermal shear-stress sensor (Sheplak et al. 2002). The sensitivity of this sensor is 11 mV/Pa at a power consumption of 9 mW (I = 10 ma) when the shear stress input was about 0.2 Pa.In this paper, we studied how to improve sensitivity of thermal shear stress sensor working underwater with allowable drive currents. They were obtained by analyzing I-V characteristic and output voltage-shear stress relationship. and they were be allied to drive the sensor in two different shear stress input ranges to explore the advancement of sensitivity.Abstract Drive current is an important parameter of thermal shear stress sensor. Increasing drive current is helpful for enhancing its sensitivity. however, there must be an allowable drive current for the sake of safe working temperature of the sensor. how to make full use of drive current to increase the sensor's sensitivity working underwater was studied. If the allowable drive current in still water and the current in stream water are used to drive the sensor in lower and higher shear stress input ranges, respectively, sensitivity of the sensor will be enhanced with the sensor working under a safe temperature. The both currents were separately determined by analyzing I-V characteristic and output voltage-shear stress relationship. We can improve the sensor's sensitivity from 11.8 to 27.5 mV/Pa when shear stress input was 0.4 Pa.

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confidence: 99%

Improved sensitivity of micro thermal sensor for underwater wall shear stress measurement

Zhu

Jiang

et al. 2014

Microsyst Technol

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“…First approaches of thermal flow sensors on flexible substrates have been done by Buder et al [7,8], Tan et al [9,10] and Liu et al [11]. Buder et al present a hot-wire anemometer being realized by placing either one or two freestanding nickel wires on a 125 m thick polyimide foil.…”

Section: Flexible Flow Sensors -State Of the Artmentioning

confidence: 99%

“…In this work an Au/Cr heater is deposited on a polyimide film with a thickness of 25 m. The sensing element is then mounted in an inner wall surface of a straight tube and works with the anemometric measurement principle, too. In Liu et al a platinum thin film resistor is placed on a silicon nitride/polyimide foil with a thickness of the polyimide film of 50 m [11]. The sensor is assembled as an array and used for detection of a boundary layer separation.…”

Section: Flexible Flow Sensors -State Of the Artmentioning

confidence: 99%

“…This approach is, however, expensive and might impact the flow channel's structural health. For those issues a wide setup of thermal flow sensor approaches on flexible substrates can be found in literature [7][8][9][10][11]. These approaches have in common that the sensors' characteristics are reduced due to their substrate modification which is often coming along with a sensor design differing from the ideal one.…”

Section: Introductionmentioning

confidence: 99%

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Membrane-based thermal flow sensors on flexible substrates

Sturm¹,

Lang²

2013

Sensors and Actuators A: Physical

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“…presents a shear stress sensor based on the anemometric principle: A hot wire on a polyimide foil is heated up by a constant electrical current and the voltage measured giving information about the current temperature of the wire. The occurrence of a fluid flow on the sensor will reduce the temperature, which can be seen as change of voltage of the sensor [12]. In [13] a hot wire (here a polysilicon heater on a silicon nitride membrane) is used as well.…”

Section: Thermal Flow Sensors For Flow Separation Detection—a State Omentioning

confidence: 99%

Boundary Layer Separation and Reattachment Detection on Airfoils by Thermal Flow Sensors

Sturm

Dumstorff

Busche

et al. 2012

Sensors

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A sensor concept for detection of boundary layer separation (flow separation, stall) and reattachment on airfoils is introduced in this paper. Boundary layer separation and reattachment are phenomena of fluid mechanics showing characteristics of extinction and even inversion of the flow velocity on an overflowed surface. The flow sensor used in this work is able to measure the flow velocity in terms of direction and quantity at the sensor's position and expected to determine those specific flow conditions. Therefore, an array of thermal flow sensors has been integrated (flush-mounted) on an airfoil and placed in a wind tunnel for measurement. Sensor signals have been recorded at different wind speeds and angles of attack for different positions on the airfoil. The sensors used here are based on the change of temperature distribution on a membrane (calorimetric principle). Thermopiles are used as temperature sensors in this approach offering a baseline free sensor signal, which is favorable for measurements at zero flow. Measurement results show clear separation points (zero flow) and even negative flow values (back flow) for all sensor positions. In addition to standard silicon-based flow sensors, a polymer-based flexible approach has been tested showing similar results.

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Detecting boundary-layer separation point with a micro shear stress sensor array

Cited by 20 publications

References 3 publications

Improved sensitivity of micro thermal sensor for underwater wall shear stress measurement

Improved sensitivity of micro thermal sensor for underwater wall shear stress measurement

Membrane-based thermal flow sensors on flexible substrates

Boundary Layer Separation and Reattachment Detection on Airfoils by Thermal Flow Sensors

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