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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Improvement of vertical velocity statistics measured by a Doppler lidar through comparison with sonic anemometer observations

Since turbulence measurements from Doppler lidars are being increasingly used within wind energy and boundary-layer meteorology, it is important to assess and improve the accuracy of these observations. While turbulent quantities are measured by Doppler lidars in several different ways, the simplest and most frequently used statistic is vertical velocity variance ( w ' 2 ) from zenith stares. But, the competing effects of signal noise and resolution volume limitations, which respectively increase and decrease w ' 2 , reduce the accuracy of these measurements. Herein, an established method that utilises the autocovariance of the signal to remove noise is evaluated and its skill in correcting for volume-averaging effects in the calculation of w ' 2 is also assessed. In addition, this autocovariance technique is further refined by defining the amount of lag time to use for the most accurate estimates of w ' 2 . And through comparison of observations from two Doppler lidars and sonic anemometers on a 300 m tower, the autocovariance technique is shown to generally improve estimates of w ' 2 . After the autocovariance technique is applied, values of w ' 2 from the Doppler lidars are generally in close agreement ( R 2 ≈ 0.95 -0.98) with those calculated from sonic anemometer measurements.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2012

Motion-Corrected 3D Sonic Anemometer for Tethersondes and Other Moving Platforms

To date, it has not been possible to apply 3D sonic anemometers on tethersondes or similar atmospheric research platforms due to the motion of the supporting platform. A tethersonde module including both a 3D sonic anemometer and associated motion correction sensors has been developed, enabling motion-corrected 3D winds to be measured from a moving platform such as a tethersonde. Blimps and other similar lifting systems are used to support tethersondes meteorological devices that fly on the tether of a blimp or similar platform. To date, tethersondes have been limited to making basic meteorological measurements (pressure, temperature, humidity, and wind speed and direction). The motion of the tethersonde has precluded the addition of 3D sonic anemometers, which can be used for high-speed flux measurements, thereby limiting what has been achieved to date with tethersondes. The tethersonde modules fly on a tether that can be constantly moving and swaying. This would introduce enormous error into the output of an uncorrected 3D sonic anemometer. The motion correction that is required must be implemented in a low-weight, low-cost manner to be suitable for this application. Until now, flux measurements using 3D sonic anemometers could only be made if the 3D sonic anemometer was located on a rigid, fixed platform such as a tower. This limited the areas in which they could be set up and used. The purpose of the innovation was to enable precise 3D wind and flux measurements to be made using tether - sondes. In brief, a 3D accelerometer and a 3D gyroscope were added to a tethersonde module along with a 3D sonic anemometer. This combination allowed for the necessary package motions to be measured, which were then mathematically combined with the measured winds to yield motion-corrected 3D winds. At the time of this reporting, no tethersonde has been able to make any wind measurement other than a basic wind speed and direction measurement. The addition of a 3D sonic anemometer is unique, as is the addition of the motion-correction sensors.

Bognar, John↗
NASA NTRS1976

Trailing anemometer for low airspeed calibration

A propeller-type trailing airspeed anemometer system is described for low airspeed (M not exceeding 0.2) calibration which has improved accuracy and is easy to implement as compared to most methods currently in use. The trailing anemometer system consists of the trailing anemometer itself, a deployment mechanism, and an operator's control box. The trailing anemometer is a small low-drag brass body provided with tail fins for self-alignment with the airstream. The rotational speed of a small six-bladed low-inertia propeller is sensed with a miniature self-generating tachometer inside the anemometer. A very satisfactory airspeed calibration can be made with this device in which true airspeed can be measured to within 1 knot. Results from flight calibration of an aircraft and trail-back characteristics of the anemometer and cable are included. The operating speed range of the designed cable-anemometer combination is 7 to 165 knots.

Fisher, B. D.↗
DOE OSTI2017

Identification of tower-wake distortions using sonic anemometer and lidar measurements

The eXperimental Planetary boundary layer Instrumentation Assessment (XPIA) field campaign took place in March through May 2015 at the Boulder Atmospheric Observatory, utilizing its 300 m meteorological tower, instrumented with two sonic anemometers mounted on opposite sides of the tower at six heights. This allowed for at least one sonic anemometer at each level to be upstream of the tower at all times and for identification of the times when a sonic anemometer is in the wake of the tower frame. Other instrumentation, including profiling and scanning lidars aided in the identification of the tower wake. Here we compare pairs of sonic anemometers at the same heights to identify the range of directions that are affected by the tower for each of the opposing booms. The mean velocity and turbulent kinetic energy are used to quantify the wake impact on these first- and second-order wind measurements, showing up to a 50% reduction in wind speed and an order of magnitude increase in turbulent kinetic energy. Comparisons of wind speeds from profiling and scanning lidars confirmed the extent of the tower wake, with the same reduction in wind speed observed in the tower wake, and a speed-up effect around the wake boundaries. Wind direction differences between pairs of sonic anemometers and between sonic anemometers and lidars can also be significant, as the flow is deflected by the tower structure. Comparisons of lengths of averaging intervals showed a decrease in wind speed deficit with longer averages, but the flow deflection remains constant over longer averages. Furthermore, asymmetry exists in the tower effects due to the geometry and placement of the booms on the triangular tower. An analysis of the percentage of observations in the wake that must be removed from 2 min mean wind speed and 20 min turbulent values showed that removing even small portions of the time interval due to wakes impacts these two quantities. Furthermorew, a vast majority of intervals have no observations in the tower wake, so removing the full 2 or 20 min intervals does not diminish the XPIA dataset.

17 WIND ENERGY↗
NASA NTRS2004

SiC-Based Miniature High-Temperature Cantilever Anemometer

The figure depicts a miniature cantilever-type anemometer that has been developed as a prototype of compact, relatively nonintrusive anemometers that can function at temperatures up to 600 C and that can be expected to be commercially mass-producible at low cost. The design of this anemometer, and especially the packaging aspect of the design, is intended to enable measurement of turbulence in the high-temperature, high-vibration environment of a turbine engine or in any similar environment. The main structural components of the anemometer include a single-crystal SiC cantilever and two polycrystalline SiC clamping plates, all made from chemical-vapor-deposited silicon carbide. Fabrication of these components from the same basic material eliminates thermal-expansion mismatch, which has introduced spurious thermomechanical stresses in cantilever-type anemometers of prior design. The clamping plates are heavily oxidized to improve electrical insulation at high temperature. A cavity that serves as a receptacle for the clamped end of the cantilever is etched into one end of one clamping plate. Trenches that collectively constitute a socket for a multipin electrical plug (for connection to external electronic circuitry) are etched into the opposite end of this clamping plate. Metal strips for electrical contact are deposited on one face of the other clamping plate. Piezoresistive single-crystal SiC thin-film strain gauges are etched in the n-type SiC epilayer in a Wheatstone-bridge configuration. Metal contact pads on the cantilever that extend into the clamping-receptacle area, are obtained by deposition and patterning using standard semiconductor photolithography and etching methods. The cantilever and the two clamping plates are assembled into a sandwich structure that is then clamped in a stainless-steel housing. The Wheatstone- bridge carrying SiC cantilever with the metal contact pads on the piezoresistors is slid into the receptacle in the bottom clamping plate. The top clamping plate is brought into contact with the bottom plate so that the narrow section of the metal strips on the top clamp plate aligns with the metal contact pads on the cantilever. When the parts are clamped together, the metal strips provide electrical connections between the Wheatstone-bridge contact points and the sides the trenches that constitute the socket for the multipin electrical plug. Hence, to connect the Wheatstone bridge to external circuitry for processing of the anemometer readout, one need only insert the plug in the socket. In operation, the cantilever end of the stainless-steel housing is mounted flush with an engine wall and the unclamped portion of the cantilever is exposed into the flow. The cantilever is deflected in direct proportion to the force induced by component of flow parallel to the engine wall and perpendicular to the broad exposed face of the cantilever. The maximum strain on the cantilever occurs at the clamped edge and is measured by the piezoresistors, which are located there. The corresponding changes in resistance manifest themselves in the output of the Wheatstone bridge.

Okojie, Robert S.↗
NASA NTRS1974

Anemometers for Mars

An investigation is conducted concerning the problems involved in the conduction of wind measurements on the planet Mars, taking into account the currently known characteristics of the Martian atmosphere. Problems introduced by the presence of the lander are examined. The suitability of several different types of anemometers for making the measurements is discussed, giving attention to rotating anemometers, sonic anemometers, ion tracers, drag force anemometers, pitot tubes, and thermal anemometers.

Henry, R. M.↗
NASA NTRS1988

The Design and Use of a Temperature-Compensated Hot-Film Anemometer System for Boundary-Layer Flow Transition Detection on Supersonic Aircraft

An airborne temperature-compensated hot-film anemometer system has been designed, fabricated, and used to obtain in-flight airfoil boundary-layer flow transition data by the NASA Ames-Dryden Flight Research Facility. Salient features of the anemometer include near constant sensitivity over the full flight envelope, installation without coaxial wiring, low-noise outputs, and self-contained signal conditioning with dynamic and steady-state outputs. The small size, low-power dissipation, and modular design make the anemometer suitable for use in modern high-performance research aircraft. Design of the temperature-compensated hot-film anemometer and its use for flow transition detection on a laminar flow flight research project are described. Also presented are data gathered in flight which is representative of the temperature-compensated hot-film anemometer operation at subsonic, transonic, and supersonic flight conditions.

Chiles, Harry R.↗
NASA NTRS1977

A suspended anemometer system for measuring true airspeed on low-speed airplanes

A suspended anemometer system for calibrating pitot-static systems on low speed research airplanes is described. The anemometer measures true airspeed when suspended beneath the airplane on a long cable in regions of undisturbed air. The electrical output of the propeller driven tachometer is a sine wave, the frequency of which is proportional to true airspeed. The anemometer measures true airspeed over a range from 20 to 60 m/sec at altitudes to 3000 m, with an accuracy of + or - 0.5 percent of full scale range. This accuracy is exclusive of errors in the recording system. The stability of the suspended system was investigated and was found adequate in the airspeed range. For the purpose of determining the location of the anemometer relative to the airplane, a method is given for calculating the shape assumed by the deployed cable.

Kershner, D. D.↗
NASA NTRS1995

Laser Anemometer Measurements of the Three-Dimensional Rotor Flow Field in the NASA Low-Speed Centrifugal Compressor

A laser anemometer system was used to provide detailed surveys of the three-dimensional velocity field within the NASA low-speed centrifugal impeller operating with a vaneless diffuser. Both laser anemometer and aerodynamic performance data were acquired at the design flow rate and at a lower flow rate. Floor path coordinates, detailed blade geometry, and pneumatic probe survey results are presented in tabular form. The laser anemometer data are presented in the form of pitchwise distributions of axial, radial, and relative tangential velocity on blade-to-blade stream surfaces at 5-percent-of-span increments, starting at 95-percent-of-span from the hub. The laser anemometer data are also presented as contour and wire-frame plots of throughflow velocity and vector plots of secondary velocities at all measurement stations through the impeller.

Hathaway, Michael D.↗
DOE OSTI2013

The Wind Powering America Anemometer Loan Program: A Retrospective

This white paper details the history, mechanics, status, and impact of the Native American Anemometer Loan Program (ALP) conducted by the U.S. Department of Energy's Wind Powering America (WPA) initiative. Originally conceived in 2000 and terminated (as a WPA activity) at the end of FY 2011, the ALP has resulted in the installation of anemometers at 90 locations. In addition, the ALP provided support for the installation of anemometers at 38 additional locations under a related ALP administered by the Western Area Power Administration.

17 WIND ENERGY↗
NASA NTRS1930

Calibration and Lag of a Friez Type Cup Anemometer

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.

INSTRUMENTS - ANEMOMETERS - FRIEZ↗
DOE OSTI2015

Laser Doppler anemometer signal processing for blood flow velocity measurements

A new method for analysing the signal in a laser Doppler anemometer based on the differential scheme is proposed, which provides the flow velocity measurement in strongly scattering liquids, particularly, blood. A laser Doppler anemometer intended for measuring the absolute blood flow velocity in animal and human near-surface arterioles and venules is developed. The laser Doppler anemometer signal structure is experimentally studied for measuring the flow velocity in optically inhomogeneous media, such as blood and suspensions of scattering particles. The results of measuring the whole and diluted blood flow velocity in channels with a rectangular cross section are presented. (laser applications and other topics in quantum electronics)

42 ENGINEERING↗
NASA NTRS1996

Calibration of Hot Wire Anemometers. (Latest Citations from the Aerospace Database)

The bibliography contains citations concerning calibration methods and measurement correction schemes for hot wire anemometers. Coverage includes static and dynamic calibration of sensors having single, multiple, cross, and ring wire configurations. Correction methods to account for yaw angle, low-velocity flow, microgravity, wall proximity, and highly fluctuating turbulence, velocity, or temperature are covered. Correction methods are also referenced for installations having multiple sensors. Hot film and laser anemometers, and the use of anemometers in specific industrial and aerospace applications are extensively covered in separate biblographies. (Contains 50-250 citations and includes a subject term index and title list.)

HOT WIRE ANEMOMETERS↗
NASA NTRS2020

Development of a Venus Surface Wind Sensor Based on a Miniature Drag-Force Anemometer

To better understand the atmospheric structure and dynamics on the Venus surface and provide input to climate models, there is a need to measure the wind velocity and direction on the surface and track changes over extended periods. A wind sensor based on a miniature drag-force anemometer is being developed to meet the challenges for wind measurements and operational requirements on the surface of Venus. The sensor materials are chosen to enhance durability and prevent reactivity with the Venus surface atmosphere. Advantages of this approach include that it is independent on variable heat transfer, has been matured in other harsh environment applications,and has a low mass and power requirement. This report describes demonstration of this miniature drag-force anemometer integrated with high temperature electronics in simulated Venus surface environment. Prototype drag-force anemometers were demonstrated integrated with an operational amplifier recording transient effects in a simulated Venus surface environment. For multidirectional wind monitoring, the sensors are small enough to be deployed orthogonally as a three-dimensional array on a small arm or mast

wind measurement↗
NASA NTRS1977

Miniature drag-force anemometer

A miniature drag-force anemometer is described which is capable of measuring dynamic velocity head and flow direction. The anemometer consists of a silicon cantilever beam 2.5 mm long, 1.5 mm wide, and 0.25 mm thick with an integrated diffused strain-gage bridge, located at the base of the beam, as the force measuring element. The dynamics of the beam are like those of a second-order system with a natural frequency of about 42 kHz and a damping coefficient of 0.007. The anemometer can be used in both forward and reversed flow. Measured flow characteristics up to Mach 0.6 are presented along with application examples including turbulence measurements.

Krause, L. N.↗
NASA NTRS1978

A flight evaluation of a trailing anemometer for low-speed calibrations of airspeed systems on research aircraft

Research airspeed systems on three low-speed general aviation airplanes were calibrated by the trailing anemometer method. Each airplane was fitted with an NASA pitot-static pressure tube mounted on either a nose or wing boom. The uncalibrated airspeed systems contained residual static-pressure position errors which were too large for high-accuracy flight research applications. The trailing anemometer calibration was in agreement with the tower flyby calibration for the one aircraft for which the comparison was made. The continuous deceleration technique for the trailing anemometer method offers reduced test time with no appreciable loss of accuracy for airspeed systems with pitot-static system lag characteristics similar to those described.

Fisher, B. D.↗
NASA NTRS1977

Miniature drag force anemometer

A miniature drag force anemometer is described which is capable of measuring dynamic velocity head and flow direction. The anemometer consists of a silicon cantilevered beam 2.5 mm long, 1.5 mm wide, and 0.25 mm thick with an integrated diffused strain gage bridge, located at the base of the beam, as the force measuring element. The dynamics of the beam are like that of a second order system with a natural frequency of about 42 kHz and a damping coefficient of 0.007. The anemometer can be used in both forward and reversed flow. Measured flow characteristics up to Mach 0.6 are presented along with application examples including turbulence measurements.

Krause, L. N.↗