The Calibration And Operation Of Hot Wire Anemometers
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The Calibration And Operation Of Hot Wire Anemometers
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Author : K. C. Watts
language : en
Publisher:
Release Date : 1973
The Calibration And Operation Of Hot Wire Anemometers written by K. C. Watts and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1973 with Hot-wire anemometer categories.
Development Of An Automated Calibration System For Hotwire Anemometers
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Author : Constantin Schosser
language : en
Publisher: diplom.de
Release Date : 2010-01-22
Development Of An Automated Calibration System For Hotwire Anemometers written by Constantin Schosser and has been published by diplom.de this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010-01-22 with Technology & Engineering categories.
Inhaltsangabe:Introduction: In experimental fluid dynamic measurements hot-wire anemometry is used to record information about flow fields. Furthermore one can obtain the magnitude, the direction and even the time dependant behaviour of the fluid flow, if multiple-wire probes are in operation. The hot-wire measurement technique is based on the convective heat transfer from a heated element to the fluid flow, which is actually proportional to the velocity of the flow. So HWA is an indirect measurement technique. There are miscellaneous sensors which work properly in water or other liquids, air or in gas flows. As an example, Fig. 1.1 shows a cross-wire probe in a fluid flow, which can detect the velocity and its direction in two components, if the main flow direction is in one plane (2D flow). Predominantly HWA is a research tool for turbulent flow studies, especially transient procedures. Turbulence models have to be built to represent the characteristics of the flow in numerical simulations (CFD). Therefore only detailed experimental measurements lead to reliable information about the local velocity of a turbulent flow. This can be provided by HWA on the basis of its very high spatial and temporal resolution. Although the development of HWA started at the beginning of the 19th century and new techniques like PIV or LDA (direct methods) have been established, it is still a common device in all wind tunnel labs. The analogue output signal can be optimized by filters before signal processing. It can also be deployed to arrange a spectrum analysis, due to the high temporal resolution. Moreover, unlike the digital devices the analogue signal is densely packed. The range of application is large and leads from sub- and supersonic flows, the independency of the medium to high-temperature measurements. HWA is also affordable in contrast to LDA and PIV systems. In spite of these advantages the natural contamination of the hot-wire probe increases by and by, since the particles in the fluid flow mature themselves to the probe and finally isolate it. As this effect of disturbance causes measuring errors, the hot-wire probes have to be calibrated at frequent intervals - best before and after every data acquisition series. However, HWA is an intrusive measurement technique, thus disturbing the flow. Another disadvantage is that it is not applicable in separation and backward flow regions. The aim of this thesis is to develop an automated calibration system to [...]
Fundamentals Of Hot Wire Anemometry
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Author : Charles G. Lomas
language : en
Publisher: Cambridge University Press
Release Date : 2011-06-09
Fundamentals Of Hot Wire Anemometry written by Charles G. Lomas and has been published by Cambridge University Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011-06-09 with Science categories.
This 1985 book provides a summary of the theory and practice of the hot wire anemometer, an instrument used to measure the speed of fluid flow. Many techniques and uses of this instrument are discussed in detail. The author considers such topics as probe fouling, probe design, and circuit design, as well as the thermodynamics of heated wires and thin films. He also discusses measurements of turbulence, shear flows, vorticity, temperature, combined temperature and velocity, two-phase flows, and compressible flows for measurements in air, water, mercury, blood, glycerine, oil, luminous gases, and polymer solutions. The book concludes with a section on the pulsed wire anemometer and other wake-sensing anemometers. This book assumes a familiarity with basic fluid mechanics. However, mathematical descriptions occur near the end of each chapter thus allowing those with a limited mathematical background to make use of the practical details at the beginning of each chapter.
Hot Wire Anemometry
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Author : Anthony Edward Perry
language : en
Publisher: Oxford University Press, USA
Release Date : 1982
Hot Wire Anemometry written by Anthony Edward Perry and has been published by Oxford University Press, USA this book supported file pdf, txt, epub, kindle and other format this book has been release on 1982 with Language Arts & Disciplines categories.
Development Of An Autonomous Single Point Calibration For A Constant Voltage Hot Wire Anemometer
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Author : Ryan Christopher Murphy
language : en
Publisher:
Release Date : 2015
Development Of An Autonomous Single Point Calibration For A Constant Voltage Hot Wire Anemometer written by Ryan Christopher Murphy and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with Hot-wire anemometer categories.
Traditionally, the measurement of turbulence has been conducted using hot-wire anemometry. This thesis presents the implementation of a constant voltage hot-wire anemometer for use with the Boundary Layer Data System (BLDS). A hot-wire calibration apparatus has been developed that is capable of operation inside a vacuum chamber and flow speeds up to 50 m/s. Hot-wires operated with a constant-voltage anemometer (CVA) were calibrated at absolute static pressures down to 26 kPa. A thermal/electrical model for a hot-wire and the CVA circuit successfully predicted the measured CVA output voltage trend at reduced pressure environments; however, better results were obtained when the Nusselt number was increased. A calibration approach that required only one measured flow speed was developed to allow autonomous calibrations of a CVA hot-wire. The single-point calibration approach was evaluated through comparison with the experimental data from the vacuum chamber over a range of 14-50 m/s and at pressures from 26 to 100 kPa. The thermal-electrical model was used to make predictions of CVA output voltage and the corresponding flow speed for conditions that could not be replicated within a laboratory. The first set of predictions were made for conditions from 7.5 to 100 kPa, at a constant temperature of 250C, within a flight speed range of 40 to 150 m/s. Single-point calibrations were developed from these predictions. Additionally, the thermal-electrical model was used to predict hot-wire response for a change in temperature of 250C at 26 kPa and the single-point calibration developed for the pressure range 7.5 to 100 kPa was tested for its ability to adjust. The temperature variation at a single pressure of 26 kPa proved that the single-point function was capable of adapting to off-standard temperatures with the largest deviations of +/- 7% in the mid-range velocities. With a temperature drop, the deviations were below 5%. The second set of thermal-electrical predictions involved conditions for altitude from 0 to 18 km at flow speeds from 40 to 150 m/s. A single-point calibration was developed for altitude conditions. Furthermore, to test the single-point calibration the thermal-electrical model was used to predict hot-re response for a temperature variation of 250C at 18 km. The single-point calibration developed for altitude proved that it was capable of adjusting to a temperature variation of 250C with maximum deviations of about 5% at mid-range velocities. It is proposed that the single-point calibration approach could be employed for CVA measurements with the Boundary Layer Data System (BLDS) to allow hot-wire data to be acquired autonomously during flight tests.
Calibration Methods For A Constant Voltage Anemometer Operated Hot Wire In A Hypersonic Flow
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Author :
language : en
Publisher:
Release Date : 2003
Calibration Methods For A Constant Voltage Anemometer Operated Hot Wire In A Hypersonic Flow written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003 with categories.
The calibration of measurements made with a CVA-operated hot-wire, in a quiet hypersonic wind tunnel, are examined. Two calibration methods are evaluated. The first calibration method is based on the ratio of the power dissipated in the hot-wire and the difference between the hot- and cold-wire resistances. The second method is based on the traditional semi-empirical heat transfer relation for a heated wire in supersonic/hypersonic flow. The mean mass flux and total temperature derived from the calibration methods show overall good agreement with Navier-Stokes predictions. In general, the first method gives better results across the boundary layer. However, limitations in the calibration data meant no definitive assessment of the capability to yield fluctuation measurements could be made. The recently derived sensitivity coefficients for a CVA-operated hot-wire are used to obtain fluctuation measurements. Also, the fluctuating diagram method is used to evaluate the performance of the NASA Langley Mach 6 quiet tunnel and to detail the characteristics of the fluctuations in the laminar hypersonic boundary layer. Within the boundary layer, profiles of the measured rms fluctuations and the fluctuation diagrams show that the intensityof the boundary layer disturbance fluctuations are most intense in the vicinity of the critical layer. The static pressure fluctuations derived from the fluctuation diagrams verify that the fluctuations are less than 0.2%. This observation confirms previous qualitative observations of the performance of the Mach 6 quiet nozzle.
A Calibration Technique For A Hot Wire Probe Vector Anemometer
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Author : James Scheiman
language : en
Publisher:
Release Date : 1982
A Calibration Technique For A Hot Wire Probe Vector Anemometer written by James Scheiman and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1982 with Hot-wire anemometer categories.
A Hot Wire Anemometer For Measuring Air Flow Through Engine Radiators
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Author : Carl George Frederick Zobel
language : en
Publisher:
Release Date : 1925
A Hot Wire Anemometer For Measuring Air Flow Through Engine Radiators written by Carl George Frederick Zobel and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1925 with Air flow categories.
Calibration And Optimization Of Constant Voltage Hot Wire Anemometer In Hypersonic Flows
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Author :
language : en
Publisher:
Release Date : 2003
Calibration And Optimization Of Constant Voltage Hot Wire Anemometer In Hypersonic Flows written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003 with categories.
Freestream and boundary layer measurements are made in a supersonic flow using both constant temperature (CTA) and constant voltage (CVA) anemometry. The performance of both anemometers is systematically made by operating the same hot-wire under identical conditions and applying post-test software corrections to the fluctuating measurements. In the case of the CVA the in situ time constant of the hot wire is measured to compensate the measured CVA output. The measurements show that when the signal-to-noise ratio is greater than one for both systems, the results are in very good agreement. The measurements of turbulence intensities are also in good agreement with previous studies. However the frequency at which noise dominates is lower for the CTA. Thus the CVA bandwidth is very much larger than that of the CTA. The amplitude roll-off at high frequencies is as theoretically expected. Thus it is desirable to obtain new quantitative turbulence measurements with larger bandwidth using the CVA. A rapid and automated stepping of the wire overheats is also developed for the CVA. This is an advancement over previous works that employed CTA, as the latter approach has a different bandwidth at each overheat, whereas the CVA has a fixed bandwidth. The rapid scanning method is then used to obtain calibrated measurements in a short duration wind tunnel.
A Calibration Procedure For The Measurement Of Transverse Vorticity Using Hot Wire Anemometry
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Author : Casey Lynn Klewicki
language : en
Publisher:
Release Date : 1983
A Calibration Procedure For The Measurement Of Transverse Vorticity Using Hot Wire Anemometry written by Casey Lynn Klewicki and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1983 with Hot-wire anemometer categories.