The enhanced sensitivity of pitot tubes at low Reynolds number

IF 2.3 3区工程技术 Q2 ENGINEERING, MECHANICAL

Flow Measurement and Instrumentation Pub Date : 2024-11-20 DOI:10.1016/j.flowmeasinst.2024.102750

Keld R. Rasmussen , Jens Jacob Iversen , Jonatan Merrison

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Abstract

Pitot tubes are commonly used for measuring flow velocity in air and other fluids. The aim of this experimental study was to link flow conditions and geometry to the differential pressure response (Δp) of pitot tubes. Based on outer diameter the pitot tube Reynolds number (Re_D) ranges from less than 1 (molecular regime) to more than 100 (inertial regime). This large range in Reynolds number was achieved by varying the pitot tube outer diameter in the range 0.4–10 mm, the air density from 0.006 to 1.2 kg/m³ and the air velocity from 0.25 to 30 m/s and by operating pitot tubes within a recirculating low pressure wind tunnel down to a pressure of 0.5 mbar as well as performing comparative observation in an open circuit wind tunnel. For the smallest Re_D, viscous forces enhance Δp giving the smallest micro-pitot tubes superior functionality especially at low pressure. The small diameter of the micro-pitot tubes can also allow measurements close to a wall within the boundary layer. Measurements of Δp for Re_D between approximately 0.08 and 1000 agree well with an analytical model derived by Muriel Barker in 1922 while they agree less well or even poorly with more recent models. At the lowest Re_D the maximum enhancement of Δp was observed to be a factor of 65. The enhancement became undetectable for Re_D larger than approximately 70. At the lowest air density and the smallest pitot tube inner diameter possible effects due to slip were observed.

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在低雷诺数条件下提高皮托管的灵敏度

皮托管常用于测量空气和其他流体中的流速。本实验研究的目的是将流动条件和几何形状与皮托管的压差响应 (Δp)联系起来。根据外径，皮托管雷诺数 (ReD) 从小于 1（分子系统）到大于 100（惯性系统）不等。要实现如此大范围的雷诺数，需要在 0.4-10 毫米的范围内改变皮托管外径，在 0.006 至 1.2 公斤/立方米的范围内改变空气密度，在 0.25 至 30 米/秒的范围内改变空气速度，在压力低至 0.5 毫巴的再循环低压风洞中操作皮托管，以及在开式循环风洞中进行比较观测。对于最小的 ReD，粘滞力会增强 Δp，从而使最小的微型皮托管具有卓越的功能，尤其是在低压条件下。微坑管的小直径还允许在边界层内靠近管壁进行测量。ReD 在大约 0.08 到 1000 之间时，Δp 的测量结果与 Muriel Barker 在 1922 年得出的分析模型非常吻合，而与最新模型的吻合程度较低，甚至很差。据观测，在最低 ReD 时，Δp 的最大增强为 65 倍。当 ReD 大于约 70 时，就无法检测到增强。在空气密度最低、皮托管内径最小的情况下，可能会出现滑移效应。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Flow Measurement and Instrumentation 工程技术-工程：机械

CiteScore

4.30

自引率

13.60%

发文量

123

审稿时长

6 months

期刊介绍： Flow Measurement and Instrumentation is dedicated to disseminating the latest research results on all aspects of flow measurement, in both closed conduits and open channels. The design of flow measurement systems involves a wide variety of multidisciplinary activities including modelling the flow sensor, the fluid flow and the sensor/fluid interactions through the use of computation techniques; the development of advanced transducer systems and their associated signal processing and the laboratory and field assessment of the overall system under ideal and disturbed conditions. FMI is the essential forum for critical information exchange, and contributions are particularly encouraged in the following areas of interest: Modelling: the application of mathematical and computational modelling to the interaction of fluid dynamics with flowmeters, including flowmeter behaviour, improved flowmeter design and installation problems. Application of CAD/CAE techniques to flowmeter modelling are eligible. Design and development: the detailed design of the flowmeter head and/or signal processing aspects of novel flowmeters. Emphasis is given to papers identifying new sensor configurations, multisensor flow measurement systems, non-intrusive flow metering techniques and the application of microelectronic techniques in smart or intelligent systems. Calibration techniques: including descriptions of new or existing calibration facilities and techniques, calibration data from different flowmeter types, and calibration intercomparison data from different laboratories. Installation effect data: dealing with the effects of non-ideal flow conditions on flowmeters. Papers combining a theoretical understanding of flowmeter behaviour with experimental work are particularly welcome.