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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

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

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

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

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

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


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

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

Deployment Notes for Sodars at the Stevens Institute of Technology during the March 2005 Urban Dispersion Program Field Campaign (MSG05)

Description: This report documents the deployment of two sodars at the Stevens Institute of Technology (SIT) in Hoboken, New Jersey, during the March 2005 Madison Square Garden Urban Dispersion Field Campaign (MSG05) conducted in the vicinity of Madison Square Garden in Midtown Manhattan. One sodar was a Scintec MFAS sodar that was operated on a dock along the Hudson River. This sodar was only operated during Intensive Observation Periods (IOPs). The other sodar was an AeroVironment (AV) Model 3000 MiniSodar that was located on top of the Howe Center at SIT. This sodar was operated continually, but there were data quality issues in the lowest three and upper seven range gates during non-IOP periods. The IOP data from the AeroVironment was reprocessed so that only data from the lowest three and highest seven range gates was removed. Measurements from both sodars were compared to measurements made using a propeller and vane anemometer that was also located on top of the Howe Center. This report also describes the quality control methods applied to data from each sodar and the structure of the data files available. The agreement between the sodars is generally good, and we recommend using either the AV data or the Scintec data during the two IOPs, bearing in mind that there are some differences in the measured wind direction above 150 m MSL.
Date: August 1, 2006
Creator: Berg, Larry K. & Allwine, K Jerry
Partner: UNT Libraries Government Documents Department

Comparison of wind speed and turbulence measurements made by a hot-film probe and a bivane in the atmospheric surface layer

Description: Two independent systems for determining wind speed and turbulence levels are being used in an on-shore diffusion study on Long Island near Brookhaven National Laboratory. Results obtained from the two instrument systems are compared to illustrate the differences in the measured values of the vector wind, mean wind speed, variance, turbulence level and energy spectra. Details of the physical characteristics and relative advantages of a commercial Vector Vane and a three-dimensional hot-film sensor are also presented. Measurements of the mean wind speed and the turbulence level compared well. The Vector Vane underestimated spectral densities for frequencies above 1 hertz. (auth)
Date: April 30, 1974
Creator: SethuRaman, S. & Brown, R.M.
Partner: UNT Libraries Government Documents Department

Modeling and testing of a thermal transient anemometer

Description: The Thermal Transient Anemometer (TTA) is a fluid mass flow measuring device which utilizes a thermocouple as a probe. The probe is periodically heated by an electric current pulse through the thermocouple junction, and the measured rate of cooling between pulses is related to the local mean flow velocity. The standard thermocouple sensor provides an inexpensive flow probe which is durable, rugged, and capable of satisfactory operation in hostile environments. The TTA was developed and patented in prototype form by Instrument Development for Applied Physics (IDAP), a small US company. IDAP has tested the TTA and shown that the measurement principle is valid. However, there is a need to refine the prototype so that the TTA becomes a commercially viable instrument. The main concern is to reduce the heating current to the TTA so that battery-powered operation is possible. To do this, a probe needs to be developed such that only the region local to the thermocouple junction is heated, rather than the entire length of the wire. There area number of ways that this might be done, and IDAP has worked with ARi Industries, a thermocouple manufacturer, to develop probe designs that would have this characteristic, and at the same time would retain the ruggedness and ease of manufacture of a standard thermocouple. The purpose of this CRADA was to investigate these designs with a view to their possible commercial development. The starting point was to develop a computer model of the TTA as it currently exists, i.e., the prototype configuration, and to compare the results with experimental data. Good agreement between model and data was obtained, thus allowing new designs to be analyzed with some confidence.
Date: October 1, 1996
Creator: Page, R.J.
Partner: UNT Libraries Government Documents Department

Evaluation of a new sonic anemometer for routine monitoring and emergency response applications

Description: Recently, several new sonic anemometers have become available for routine wind measurements. Sonic anemometers avoid many problems associated with the traditional rotating anemometer and vane sets- inertia of moving parts, bearing wear, contamination from dust and ice, frequent maintenance. Without a starting threshold, the sonic anemometer also produces more accurate measurements of wind direction and sigma theta at very low wind speeds. We illustrate these advantages by comparing 20 days of observations from a new sonic anemometer with data from existing cup and vane sensors at the 10-m level of Lawrence Livermore National Laboratory`s meteorological tower.
Date: February 1, 1997
Creator: Gouveia, F.J & Baskett, R.L.
Partner: UNT Libraries Government Documents Department

Interfacial Refraction Through Curved and Plane-Layered Media

Description: Two laser beam tracing codes, AXIAL and CYLINDER, have been written to determine a laser beam path through plane and cylindrical interfaces. For cylindrical interfaces, an equation set was derived which describes the path of the laser beam. For plane interfaces, it was not possible to derive a single equation set. Instead, it was necessary to divide the domain up into small elements or regions. The laser beam path was then determined by calculating the path of the laser beam through each region. AXIAL and CYLINDER can be used to determine where an LDA should be positioned so that velocity measurements can be made at a specified point.
Date: July 17, 2001
Creator: Kehoe, A.B.
Partner: UNT Libraries Government Documents Department

The Long-Term Inflow and Structural Test Program

Description: The Long-term Inflow and Structural Test (LIST) program is collecting long-term, continuous inflow and structural response data to characterize the extreme loads on wind turbines. A heavily instrumented Micon 65/13M turbine with SERI 8-m blades is being used as the first test turbine for this test program. This turbine and its two sister turbines are located in Bushland, TX a test site that exposes the turbines to a wind regime that is representative of a Great Plains commercial site. The turbines and their inflow are being characterized with 60 measurements: 34 to characterize the inflow, 19 to characterize structural response, and 7 to characterize the time-varying state of the turbine. The primary characterization of the inflow into the LIST turbine relies upon an array of five sonic anemometers. These three-axis anemometers are placed approximately 2-diameters upstream of the turbine in a pattern designed to describe the inflow. Primary characterization of the structural response of the turbine uses several sets of strain gauges to measure bending loads on the blades and the tower and two accelerometers to measure the motion of the nacelle. Data from the various instruments are sampled at a rate of 30 Hz using a newly developed data acquisition system that features a time-synchronized continuous data stream that is telemetered from the turbine rotor. The data, taken continuously, are automatically divided into 10-minute segments and archived for analysis. Preliminary data are presented to illustrate the operation of the turbine and the data acquisition and analysis system.
Date: October 17, 2000
Partner: UNT Libraries Government Documents Department

LIST/BMI Turbines Instrumentation and Infrastructure

Description: In support of two major SNL programs, the Long-term Inflow and Structural Test (LIST) program and the Blade Manufacturing Initiative (BMI), three Micon 65/13M wind turbines have been erected at the USDA Agriculture Research Service (ARS) center in Bushland, Texas. The inflow and structural response of these turbines are being monitored with an array of 60 instruments: 34 to characterize the inflow, 19 to characterize structural response and 7 to characterize the time-varying state of the turbine. The primary characterization of the inflow into the LIST turbine relies upon an array of five sonic anemometers. Primary characterization of the structural response of the turbine uses several sets of strain gauges to measure bending loads on the blades and the tower and two accelerometers to measure the motion of the nacelle. Data are sampled at a rate of 30 Hz using a newly developed data acquisition system. The system features a time-synchronized continuous data stream and telemetered data from the turbine rotor. This paper documents the instruments and infrastructure that have been developed to monitor these turbines and their inflow.
Date: June 1, 2001
Partner: UNT Libraries Government Documents Department

Effects of axial heat conduction and material properties on the performance characteristics of a thermal transient anemometer probe

Description: This paper describes an investigation of the axial heat transfer within a thermal transient anemometer probe. A previous study, evaluated the performance characteristics of a thermal transient anemometer system. The study revealed discrepancies between a simplified theory and test results in the development of a universal calibration curve for probes of varying diameters. Although the cause of these discrepancies were left uncertain due to an inadequate theoretical model, the study suggested that axial conduction within the probe could account for the deviations. In this paper, computer simulations are used to further investigate axial heat conduction within the probes. The effect on calibration of axial variations of material properties along the probes is also discussed. Results from the computer simulation are used in lieu of the theoretical model used in the previous study to develop a satisfactory universal calibration curve. The computer simulations provide evidence that there is significant axial heat conduction within the probes, and that this was the cause of the discrepancies noted in the previous study.
Date: July 1, 1995
Creator: Bailey, J.L.; Page, R.J. & Acharya, M.
Partner: UNT Libraries Government Documents Department

Subcooled Boiling Near a Heated Wall

Description: Experimental measurements of void fraction, bubble frequency, and velocity are obtained in subcooled R-134a flowing over a heated flat plate near an unheated wall and compared to analytical predictions. The measurements were obtained for a fixed system pressure and mass flow rate (P = 2.4 MPa and w = 106 kg/hr) at various inlet liquid temperatures. During the experiments, electrical power was applied at a constant rate to one side of the test section. The local void fraction data, acquired with a hot-film anemometer probe, showed the existence of a significant peak near the heated wall and a smaller secondary peak near the unheated wall for the larger inlet subcoolings. Local vapor velocity data, taken with the hot-film probe and a laser Doppler velocimeter, showed broad maxima near the centerline between the heated and unheated plates. Significant temperature gradients near the heated wall were observed for large inlet subcooling. Bubble size data, inferred from measurements of void fraction, bubble frequency and vapor velocity, when combined with the measured bubble chord length distributions illustrate the transition from pure three dimensional spherical to two-dimensional planar bubble flow, the latter being initiated when the bubbles fill the gap between the plates. These various two-phase flow measurements were used for development of a multidimensional, four-field calculational method; comparisons of the data to the calculations show reasonable agreement.
Date: October 27, 2000
Creator: Trabold, T.A.; Maneri, C.C.; Vassallo, P.F. & Considine, D.M.
Partner: UNT Libraries Government Documents Department

Effects of Temporal Wind Patterns on the Value of Wind-GeneratedElectricity at Different Sites in California and the Northwest

Description: Wind power production varies on a diurnal and seasonal basis. In this paper, we use wind speed data from three different sources to assess the effects of wind timing on the value of electric power from potential wind farm locations in California and the Northwestern United States. By ''value'', we refer to either the contribution of wind power to meeting the electric system's peak loads, or the financial value of wind power in electricity markets. Sites for wind power projects are often screened or compared based on the annual average power production that would be expected from wind turbines at each site (Baban and Parry 2001; Brower et al. 2004; Jangamshetti and Rau 2001; Nielsen et al. 2002; Roy 2002; Schwartz 1999). However, at many locations, variations in wind speeds during the day and year are correlated with variations in the electric power system's load and wholesale market prices (Burton et al. 2001; Carlin 1983; Kennedy and Rogers 2003; Man Bae and Devine 1978; Sezgen et al. 1998); this correlation may raise or lower the value of wind power generated at each location. A number of previous reports address this issue somewhat indirectly by studying the contribution of individual wind power sites to the reliability or economic operation of the electric grid, using hourly wind speed data (Fleten et al.; Kahn 1991; Kirby et al. 2003; Milligan 2002; van Wijk et al. 1992). However, we have not identified any previous study that examines the effect of variations in wind timing across a broad geographical area on wholesale market value or capacity contribution of those different wind power sites. We have done so, to determine whether it is important to consider wind-timing when planning wind power development, and to try to identify locations where timing would have a more positive or ...
Date: August 4, 2006
Creator: Fripp, Matthias & Wiser, Ryan
Partner: UNT Libraries Government Documents Department