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Investigation of the Operating Properties of the Leakage Current Anemometer

Description: "Freedom from inertia, erosion of electrodes, and reaction make the leakage current particularly appropriate for the measurement of flow velocities in gases. Apparatus previously described has now been improved by reducing the size of the electrodes by one -thousandth, as is necessary aerodynamically, and by increasing the magnitude of the current from 1000 to 10,000 times; the latter result was obtained.by use of mercury high-pressure lamps set up at the one focal point of an ellipsoidal reflector with the cathodes arranged at the other focal point or by use of suitable X-ray radiation. Families of calibration curves were taken with a number of vivid tests conditions of the greatest variety and the operating properties of the instrument were widely elucidated by calculation of the sensitivity to fluctuation; this was done at first for operation at stationary conditions only; due to the freedom from inertia the instationary conditions were thus also given" (p. 1).
Date: October 1947
Creator: Fucks, Wilhelm
Partner: UNT Libraries Government Documents Department

Measurement of the arithmetic mean velocity of a pulsating flow of high velocity by the hot-wire method

Description: Report presenting an experimental method of measuring both the arithmetic mean velocity and the instantaneous velocity of pulsating flow and with the instruments developed for this purpose. A circuit for a hot-wire anemometer usable for fluctuating flow is described.
Date: April 1946
Creator: Weske, John R.
Partner: UNT Libraries Government Documents Department

Calibration and lag of a Friez type cup anemometer

Description: "Tests on a Friez type cup anemometer have been made in the variable density wind tunnel of the Langley Memorial Aeronautical Laboratory to calibrate the instrument and to determine its suitability for velocity measurements of wind gusts. The instrument was calibrated against a Pitot-static tube placed directly above the anemometer at air densities corresponding to sea level, and to an altitude of approximately 6000 feet. Air-speed acceleration tests were made to determine the lag in the instrument reading. The calibration results indicate that there should be an altitude correction. It is concluded that the cup anemometer is too sluggish for velocity measurements of wind gusts" (p. 1).
Date: June 1930
Creator: Pinkerton, Robert M.
Partner: UNT Libraries Government Documents Department

Heat-Loss Characteristics of Hot-Wire Anemometers at Various Densities in Transonic and Supersonic Flow

Description: Note presenting an experimental investigation of the heat-loss characteristics of heated fine wires suitable for use as anemometers in turbulence research. The effects of each of the several variables on the heat-loss characteristics of both normally oriented and swept wires were measured. The temperature-loading effects were found to cause large sensitivity differences between constant-temperature and constant-current operation.
Date: May 1955
Creator: Spangenberg, W. G.
Partner: UNT Libraries Government Documents Department

Investigation of Pitot tubes

Description: Report describes the principles of operation and characteristics of some of the instruments which have been devised or used to measure both low and high speeds of aeroplanes. Since the pitot tube is the instrument which has been most commonly used in the United States and Great Britain as a speedometer for aeroplanes, it is treated first and somewhat more fully than the others.
Date: 1917
Creator: Herschel, W. H. & Buckingham, E.
Partner: UNT Libraries Government Documents Department

The measurement of fluctuations of air speed by the hot-wire anemometer

Description: "The hot-wire anemometer suggests itself as a promising method for measuring the fluctuating air velocities found in turbulent flow. The only obstacle is the presence of a lag due to the limited energy input which makes even a fairly small wire incapable of following rapid fluctuations with accuracy. This paper gives the theory of the lag and describes an experimental arrangement for compensating for the lag for frequencies up to 100 or more per second when the amplitude of the fluctuation is not too great. An experimental test of the accuracy of compensation and some results obtained with the apparatus in a wind-tunnel air stream are described. While the apparatus is very bulky in its present form, it is believed possible to develop a more portable arrangement" (p. 359).
Date: January 8, 1929
Creator: Dryden, H. L. & Kuethe, A. M.
Partner: UNT Libraries Government Documents Department

Auxiliary equipment and techniques for adapting the constant-temperature hot-wire anemometer to specific problems in air-flow measurements

Description: Report presenting the constant-temperature hot-wire anemometer amplifier and accessories have been developed to provide an instrument with wide frequency response, good stability, and ease of operation. Techniques are described using the equipment to study periodic phenomena such as surge, rotating stall, and wake surveys in centrifugal- and axial-flow compressors.
Date: November 1952
Creator: Laurence, James C. & Landes, L. Gene
Partner: UNT Libraries Government Documents Department

Improved apparatus for the measurement of fluctuations of air speed in turbulent flow

Description: This report describes recent improvements in the design of the equipment associated with the hot-wire anemometer for the measurement of fluctuating air speeds in turbulent air flow, and presents the results of some experimental investigations dealing with the response of the hot wire to speed fluctuations of various frequencies. Attempts at measuring the frequency of the fluctuations encountered in the Bureau of Standards' 54-inch wind tunnel are also reported. In addition, the difficulties encountered in the use of such apparatus and the precautions found helpful in avoiding them are discussed.
Date: 1934
Creator: Mock, W. C., Jr. & Dryden, H. L.
Partner: UNT Libraries Government Documents Department

Investigation of a 0.6 hub-tip radius-ratio transonic turbine designed for secondary-flow study 4: rotor loss patterns as determined by hot-wire anemometers with rotor operating in a circumferentially uniform inlet flow field

Description: Report discussing the use of hot-wire anemometers to measure circumferential traces of specific-mass-flow variation for various radial positions at the rotor exit. Results regarding the rotor blade-wake traces, relative total-pressure ratio, and centrifuging of low-momentum fluid are provided.
Date: May 20, 1958
Creator: Kofskey, Milton G. & Allen, Hubert W.
Partner: UNT Libraries Government Documents Department

Methods of Recording Rapid Wind Changes

Description: "The purpose of our research was to determine the rapid changes of air currents which impose varying stresses on the wings of airplanes. We attempted to express in figures the turbulence of the air, which perhaps plays some role in the behavior of airplanes in flight, as well as in the realization of certain methods of gliding flight. This is the reason which led us to conceive and develop the experimental equipment (hot-wire anemometer) described herein" (p. 1).
Date: November 1932
Creator: Magnan, A.
Partner: UNT Libraries Government Documents Department

A hot-wire circuit with very small time lag

Description: A circuit for a hot-wire anemometer for the measurement of fluctuating flow is presented in the present report. The principal elements of the circuit are a Wheatstone bridge, one branch of which is the hot wire; and an electronic amplifier and a current regulator for the brief current which in combination maintain the bridge balance constant. Hence the hot wire is kept at practically constant resistance and temperature, and the time lag caused by thermal inertia of the wire is thereby reduced. Through the addition of a nonlinear amplifying stage the reading of the instrument has been rendered proportional to the velocity. A discussion of certain characteristics of the circuit and the results of related calibrating tests are given.
Date: February 1943
Creator: Weske, John R.
Partner: UNT Libraries Government Documents Department

Response of Homogeneous and Two-Material Laminated Cylinders to Sinusoidal Environmental Temperature Change, With Applications to Hot-Wire Anemometry and Thermocouple Pyrometry

Description: Note presenting an investigation of the problem of the responses of homogeneous and two-material laminated cylinders to sinusoidal environmental temperature changes. The results are applicable to situations in which small heat-transfer coefficient changes occur in the absence or presence of environmental temperature changes.
Date: September 1955
Creator: Lowell, Herman H. & Patton, Norman
Partner: UNT Libraries Government Documents Department

Use of a Hot-Wire Anemometer in Shock-Tube Investigations

Description: Note presenting the use of the hot-wire anemometer as an instrument for experimental investigations of the transient flow phenomena in a shock tube. The response of a hot-wire to a transient step-function type of change in flow conditions is studied and a criterion for predicting the right compensation is theorized and experimentally verified.
Date: December 1954
Creator: Dosanjh, Darshan Singh
Partner: UNT Libraries Government Documents Department

Empirical Method for Frequency Compensation of the Hot-Wire Anemometer

Description: Note presenting a description of the improvements in the design of equipment associated with the hot-wire anemometer for the measurement of fluctuating-air flow quantities. An improved technique and an electronic circuit for the frequency compensation of a hot wire are presented.
Date: June 1947
Creator: Runyan, Raymond A. & Jeffries, Robert J.
Partner: UNT Libraries Government Documents Department

Carbon Dioxide Flux Measurement Systems (CO2Flux) Handbook

Description: The Southern Great Plains (SGP) carbon dioxide flux (CO2 flux) measurement systems provide half-hour average fluxes of CO2, H2O (latent heat), and sensible heat. The fluxes are obtained by the eddy covariance technique, which computes the flux as the mean product of the vertical wind component with CO2 and H2O densities, or estimated virtual temperature. A three-dimensional sonic anemometer is used to obtain the orthogonal wind components and the virtual (sonic) temperature. An infrared gas analyzer is used to obtain the CO2 and H2O densities. A separate sub-system also collects half-hour average measures of meteorological and soil variables from separate 4-m towers.
Date: January 1, 2005
Creator: Fischer, M
Partner: UNT Libraries Government Documents Department

IMPROVED WIND AND TURBULENCE MEASUREMENTS USING A LOW-COST 3-D SONIC ANEMOMETER AT A LOW-WIND SITE

Description: A year of data from sonic anemometer and mechanical wind sensors was analyzed and compared at a low-wind site. Results indicate that 15-minute average and peak 1-second wind speeds (u) from the sonic agree well with data derived from a co-located cup anemometer over a wide range of speeds. Wind direction data derived from the sonic also agree closely with those from a wind vane except for very low wind speeds. Values of standard deviation of longitudinal wind speed ({sigma}{sub u}) and wind direction fluctuations ({delta}{sub {theta}}) from the sonic and mechanical sensors agree well for times with u > 2 ms{sup -1} but show significant differences with lower u values. The most significant differences are associated with the standard deviation of vertical wind fluctuations ({sigma}{sub w}): the co-located vertical propeller anemometer yields values increasingly less than those measured by the sonic anemometer as u decreases from 2.5 approaching 0 ms{sup -1}. The combination of u over-estimation and under-estimation of {sigma}{sub w} from the mechanical sensors at low wind speeds causes considerable under-estimation of the standard deviation of vertical wind angle fluctuations ({sigma}{sub {phi}}), an indicator of vertical dispersion. Calculations of {sigma}{sub {phi}} from sonic anemometer measurements are typically 5{sup o} to 10{sup o} higher when the mechanical instruments indicate that {sigma}{sub {phi}} < 5{sup o} or so. The errors in both the propeller anemometer and cup anemometer, caused by their inability to respond to higher frequency (smaller scale) turbulent fluctuations, can therefore lead to large (factors of 2 to 10 or more) errors in the vertical dispersion during stable conditions with light winds.
Date: May 11, 2007
Creator: Bowen, B
Partner: UNT Libraries Government Documents Department

Preliminary survey of compressor rotor-blade wakes and other flow phenomena with a hot-wire anemometer

Description: Report presenting the use of a hot-wire anemometer to study the tip-region flow phenomena at the exit of a single-stage transonic compressor rotor. The flow phenomena were recorded as a film which is available as a supplement to the report. Results regarding overall results of hot-wire measurements, quantitative results from hot-wire measurements, and some concluding remarks are provided.
Date: June 26, 1956
Creator: Fessler, Theodore E. & Hartmann, Melvin J.
Partner: UNT Libraries Government Documents Department

Measurement of Truck Cab Flow in Support of Wind Turbine Testing

Description: This report describes an experiment to measure the airflow over a truck cab that can be used to conduct steady-state tests on an 8-kW wind turbine. The cab airflow measurements were made to document the turbine inflow for analytical models. The airflow measurements were made with an array of anemometers positioned to represent the turbine rotor disk. The data showed that the influence of the truck cab was primarily in the lower sector of the rotor disk. The influence was negligible in the rest of the rotor disk.
Date: December 17, 1998
Creator: Larwood, S. M. (National Renewable Energy Laboratory); Acker, B. & Sencenbaugh, J. (Windlite Corporation)
Partner: UNT Libraries Government Documents Department

Design and Applications of Hot-Wire Anemometers for Steady-State Measurements at Transonic and Supersonic Airspeeds

Description: Note presenting an investigation of the design requirements and heat-transfer characteristics of exposed-wire instruments to be used for steady-state measurements at transonic and supersonic speeds. Design criterions, construction details, and typical response behavior are presented.
Date: July 1950
Creator: Lowell, Herman H.
Partner: UNT Libraries Government Documents Department

Measurement of Gas and Liquid Velocities in an Air-Water Two-Phase Flow using Cross-Correlation of Signals from a Double Senor Hot-Film Probe

Description: Local gas and liquid velocities are measured by cross-correlating signals from a double sensor hot-film anemometer probe in pure water flow and air water two-phase flow. The gas phase velocity measured in two-phase flow agrees with velocity data obtained using high-speed video to within +/-5%. A turbulent structure, present in the liquid phase, allows a correlation to be taken, which is consistent with the expected velocity profiles in pure liquid flow. This turbulent structure is also present in the liquid phase of a two-phase flow system. Therefore, a similar technique can be applied to measure the local liquid velocity in a two-phase system, when conditions permit.
Date: February 19, 2002
Creator: Gurau, B.; Vassalo, P. & Keller, K.
Partner: UNT Libraries Government Documents Department

Vapor core turbulence in annular two-phase flow

Description: This paper reports a new technique to measure vapor turbulence in two-phase flows using hot-film anemometry. Continuous vapor turbulence measurements along with local void fraction, droplet frequency, droplet velocity and droplet diameter were measured in a thin, vertical duct. By first eliminating the portion of the output voltage signal resulting from the interaction of dispersed liquid droplets with the HFA sensor, the discrete voltage samples associated with the vapor phase were separately analyzed. The data revealed that, over the range of liquid droplet sizes and concentrations encountered, the presence of the droplet field acts to enhance vapor turbulence. In addition, there is evidence that vapor turbulence is significantly influenced by the wall-bounded liquid film. The present results are qualitatively consistent with the limited data available in the open literature.
Date: June 1, 1998
Creator: Trabold, T. A. & Kumar, R.
Partner: UNT Libraries Government Documents Department

Bubble dispersion and interphase coupling in a free-shear layer

Description: Bubble-turbulence interaction in a two dimension free shear layer is analyzed experimentally, investigating the influence of the large coherent structures present in the mixing region. A dilute, dispersed system of micro-bubbles is added to one side of a horizontal two stream water tunnel. Phase Doppler anemometry and other optical flow diagnostics were used to provide size and velocity information which was conditionally averaged with respect to the Kelvin-Helmholtz rollers in the shear layer. Measurement of the kinetic energy budget associated with these large scales of the underlying flowfield show it to be significantly inhomogeneous (ranging from KE generation to destruction) near the region of maximum velocity RMS. Issues associated with the use of optical flow diagnostics applied to such a flowfield are discussed.
Date: December 1, 1995
Creator: Rightley, P.M. & Lasheras, J.C.
Partner: UNT Libraries Government Documents Department