Velocity calibration relationships for hot-wire anemometry

Bruun, Hans Henrik; Al-Kayiem, Hussain H.; Fardad, A A

doi:10.1088/0022-3735/21/2/020

Cited by 56 publications

(30 citation statements)

References 10 publications

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“…The hot-wire sensor was calibrated in the test section and a fifth order polynomial fit to the voltage response of the hot-wire was used to interpolate velocity data between calibration points. 43 Based on the method employed by Watmuff 13 for hot-wire measurements in a separation bubble, the zero velocity voltage used in the calibration was taken as the absolute minimum voltage measured over the sample duration with the wind tunnel off. At each measurement station, the hot-wire signal was sampled at 5 kHz.…”

Section: Methodsmentioning

confidence: 99%

Separated shear layer transition over an airfoil at a low Reynolds number

2012

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Shear layer development over a NACA 0018 airfoil at a chord Reynolds number of 100 000 was investigated using a combination of flow visualization, velocity field mapping, surface pressure fluctuation measurements, and stability analysis. The results provide a detailed description of shear layer transition on an airfoil at low Reynolds numbers. An extensive comparison of measured surface pressure and velocity fluctuations demonstrated that time-resolved surface pressure sensor arrays can be used to identify the presence of flow separation, estimate the extent of the separated flow region, and measure disturbance growth rate spectra in significantly less time than is required by conventional techniques. Surface pressure sensor measurements of disturbance growth rate, wave number, and convection speed are found to compare well with predictions of linear stability theory, supporting the claim that convection speeds measured in separation bubbles over low Reynolds number airfoils are associated with wave packets of growing disturbances propagating through the shear layer. Through a comparison of measured convection speeds in this investigation and prior low Reynolds number airfoil experiments, it is shown that disturbance convection speeds of between 30% and 50% of the edge velocity are typical for this type of flow, consistent with phase speed estimates from previous analytical studies on transitional separation bubbles. Modal RMS velocity profiles were measured and found to be reasonably predicted by stability theory. The results suggest that, even for the relatively thick NACA 0018 airfoil profile, disturbance development over the majority of the laminar separated shear layer is primarily governed by a linear inviscid mechanism. C 2012 American Institute of Physics. [http://dx.

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Section: Methodsmentioning

confidence: 99%

Separated shear layer transition over an airfoil at a low Reynolds number

2012

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“…22 To achieve an accurate calibration we use an ex situ calibration procedure depicted in Fig. 13 providing a well-known uniform velocity profile.…”

Section: Velocity Measurementsmentioning

confidence: 99%

The CoLaPipe—The new Cottbus large pipe test facility at Brandenburg University of Technology Cottbus-Senftenberg

König

Zanoun

Öngüner

et al. 2014

Review of Scientific Instruments

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The CoLaPipe is a novel test facility at the Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology Cottbus-Senftenberg (BTU Cottbus-Senftenberg), set up to investigate fully developed pipe flow at high Reynolds numbers (Re(m) ⩽ 1.5 × 10(6)). The design of the CoLaPipe is closed-return with two available test sections providing a length-to-diameter ratio of L/D = 148 and L/D = 79. Within this work, we introduce the CoLaPipe and describe the various components in detail, i.e., the settling chamber, the inlet contraction, the blower, bends, and diffusers as well as the cooling system. A special feature is the numerically optimized contraction design. The applications of different measuring techniques such as hot-wire anemometry and static pressure measurements to quantitatively evaluate the mean flow characteristics and turbulence statistics are discussed as well. In addition, capabilities and limitations of available and new pipe flow facilities are presented and reconsidered based on their length-to-diameter ratio, the achieved Reynolds numbers, and the resulting spatial resolution. Here, the focus is on the facility design, the presentation of some basic characteristics, and its contribution to a reviewed list of specific questions still arising, e.g., scaling and structural behavior of turbulent pipe flow as well as the influence of the development length on turbulence investigations.

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“…(6) has been solved by a Taylor series expansion method [11] and values of g found using this method relate U to E up to a power of 5.7. Alternative forms of calibration relations have been proposed and compared [12,7], including King's law, i.e., Eq. (4).…”

Section: Thermal Anemometer Compensationmentioning

confidence: 99%

“…(4). The comparison of [12] is based on airspeed data greater than 1 m/s, and hence does not include the low airspeed range of interest for this study. Hence the results are not directly related.…”

Section: Thermal Anemometer Compensationmentioning

confidence: 99%

Evaluation of a prototype thermal anemometer for use in low airspeed drying measure calculations

Martin

Grant

Ringwood

2002

Flow Measurement and Instrumentation

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An indicator of the drying rate of an airflow is the product of airspeed and humidity ratio (or vapour pressure) deficit. Significant sensor errors are present in both the high relative humidity and low airspeed ranges. Also, the margin for error is small relative to the desired drying measure for mushroom growth. The objective of this study was to evaluate the suitability of a low-cost prototype anemometer for use in a mushroom growth environment. A calibrated thermal anemometer was used as a performance reference for the prototype airspeed sensor. Case studies were carried out on two prototype airspeed sensors to determine suitability for use in this drying measure application. The study required the construction of a custom wind tunnel to produce a unidirectional airflow. The sensors (housed in the wind tunnel) were evaluated in an environmental chamber over the range of relevant temperatures. Results show promise for the future application of the prototype sensors subject to the sensors being thermally compensated. Reduction in the cost of a low velocity anemometer by an order of magnitude, would facilitate their purchase and subsequent use for airspeed control by the grower, thus broadening the range of control variables available to the grower.  2002 Elsevier Science Ltd. All rights reserved.

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Velocity calibration relationships for hot-wire anemometry

Cited by 56 publications

References 10 publications

Separated shear layer transition over an airfoil at a low Reynolds number

Separated shear layer transition over an airfoil at a low Reynolds number

The CoLaPipe—The new Cottbus large pipe test facility at Brandenburg University of Technology Cottbus-Senftenberg

Evaluation of a prototype thermal anemometer for use in low airspeed drying measure calculations

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