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

NASA Technical Reports Server (NTRS)

Bognar, John

2012-01-01

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.

Laser Doppler anemometer signal processing for blood flow velocity measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borozdova, M A; Fedosov, I V; Tuchin, V V

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. (lasermore » applications and other topics in quantum electronics)« less

An Alternative to EPA Method 9 -- Field Validation of the Digital Opacity Compliance System (DOCS)

DTIC Science & Technology

2005-03-15

at the completion of the Phase I and Phase II DOCS field demonstration. These included the following 1) anemometer, 2) sling psychrometer , 3) Abney...anemometer (Eastern Technical Associates, Inc.) Sky conditions Visual observation Relative Humidity Sling Psychrometer (Eastern Technical Associates...least have access to a range of climatic monitoring equipment including the following 1) anemometer, 2) sling psychrometer , 3) Abney Level (sun angle

Effects of precipitation on sonic anemometer measurements of turbulent fluxes in the atmospheric surface layer

NASA Astrophysics Data System (ADS)

Zhang, Rongwang; Huang, Jian; Wang, Xin; Zhang, Jun A.; Huang, Fei

2016-06-01

Effects caused by precipitation on the measurements of three-dimensional sonic anemometer are analyzed based on a field observational experiment conducted in Maoming, Guangdong Province, China. Obvious fluctuations induced by precipitation are observed for the outputs of sonic anemometer-derived temperature and wind velocity components. A technique of turbulence spectra and cospectra normalized in the framework of similarity theory is utilized to validate the measured variables and calculated fluxes. It is found that the sensitivity of sonic anemometer-derived temperature to precipitation is significant, compared with that of the wind velocity components. The spectra of wind velocity and cospectra of momentum flux resemble the standard universal shape with the slopes of the spectra and cospectra at the inertial subrange, following the -2/3 and -4/3 power law, respectively, even under the condition of heavy rain. Contaminated by precipitation, however, the spectra of temperature and cospectra of sensible heat flux do not exhibit a universal shape and have obvious frequency loss at the inertial subrange. From the physical structure and working principle of sonic anemometer, a possible explanation is proposed to describe this difference, which is found to be related to the variations of precipitation particles. Corrections for errors of sonic anemometer-derived temperature under precipitation is needed, which is still under exploration.

Extending the frequency of response of lightly damped second order systems: Application to the drag force anemometer

NASA Technical Reports Server (NTRS)

Fralick, G. C.

1982-01-01

It is shown that a conventional electronic frequency compensator does not provide adequate compensation near the resonant frequency of a lightly damped second order system, such as the drag force anemometer. The reason for this is discussed, and a simple circuit modification is presented which overcomes the difficulty. The improvement is shown in theoretical frequency response curves as well as in the experimental results from some typical drag force anemometers.

Statistical analysis of low level atmospheric turbulence

NASA Technical Reports Server (NTRS)

Tieleman, H. W.; Chen, W. W. L.

1974-01-01

The statistical properties of low-level wind-turbulence data were obtained with the model 1080 total vector anemometer and the model 1296 dual split-film anemometer, both manufactured by Thermo Systems Incorporated. The data obtained from the above fast-response probes were compared with the results obtained from a pair of Gill propeller anemometers. The digitized time series representing the three velocity components and the temperature were each divided into a number of blocks, the length of which depended on the lowest frequency of interest and also on the storage capacity of the available computer. A moving-average and differencing high-pass filter was used to remove the trend and the low frequency components in the time series. The calculated results for each of the anemometers used are represented in graphical or tabulated form.

On cup anemometer rotor aerodynamics.

PubMed

Pindado, Santiago; Pérez, Javier; Avila-Sanchez, Sergio

2012-01-01

The influence of anemometer rotor shape parameters, such as the cups' front area or their center rotation radius on the anemometer's performance was analyzed. This analysis was based on calibrations performed on two different anemometers (one based on magnet system output signal, and the other one based on an opto-electronic system output signal), tested with 21 different rotors. The results were compared to the ones resulting from classical analytical models. The results clearly showed a linear dependency of both calibration constants, the slope and the offset, on the cups' center rotation radius, the influence of the front area of the cups also being observed. The analytical model of Kondo et al. was proved to be accurate if it is based on precise data related to the aerodynamic behavior of a rotor's cup.

Atmospheric Characterization During Super-Resolution Vision System Developmental Testing

DTIC Science & Technology

2013-05-01

local time each day of the test. RM Young 81000 sonic anemometers were located at 0-, 800-, and 1800-m target points at 1.5-m elevation to provide point...estimates of C2n. Sonic anemometer data were also collected at a 0-km tower at several levels, providing a vertical turbulence profile. Turbulence...Atmospheric Instrumentation and Analysis 8 4. Estimation of C2n from Sonic Anemometer Data 11 5. Data Plots 14 6. Derived Results 32 7. Conclusions 36 8

Accurate Monitoring and Fault Detection in Wind Measuring Devices through Wireless Sensor Networks

PubMed Central

Khan, Komal Saifullah; Tariq, Muhammad

2014-01-01

Many wind energy projects report poor performance as low as 60% of the predicted performance. The reason for this is poor resource assessment and the use of new untested technologies and systems in remote locations. Predictions about the potential of an area for wind energy projects (through simulated models) may vary from the actual potential of the area. Hence, introducing accurate site assessment techniques will lead to accurate predictions of energy production from a particular area. We solve this problem by installing a Wireless Sensor Network (WSN) to periodically analyze the data from anemometers installed in that area. After comparative analysis of the acquired data, the anemometers transmit their readings through a WSN to the sink node for analysis. The sink node uses an iterative algorithm which sequentially detects any faulty anemometer and passes the details of the fault to the central system or main station. We apply the proposed technique in simulation as well as in practical implementation and study its accuracy by comparing the simulation results with experimental results to analyze the variation in the results obtained from both simulation model and implemented model. Simulation results show that the algorithm indicates faulty anemometers with high accuracy and low false alarm rate when as many as 25% of the anemometers become faulty. Experimental analysis shows that anemometers incorporating this solution are better assessed and performance level of implemented projects is increased above 86% of the simulated models. PMID:25421739

Fast-response cup anemometer features cosine response

NASA Technical Reports Server (NTRS)

Frenzen, P.

1968-01-01

Six-cup, low-inertia anemometer combines high resolution and fast response with a unique ability to sense only the horizontal component of the winds fluctuating rapidly in three dimensions. Cup assemblies are fabricated of expanded polystyrene plastic.

1991 LLWAS anemometer test program

DOT National Transportation Integrated Search

1992-01-01

Performance tests of anemometers under icing and snow conditions were conducted during 1990-1991 on the test field at : Rochester, MN and in icing chambers and wind tunnels at Sterling, VA. These tests were done for the FAA LLWAS program : to test se...

Atmospheric turbulence affects wind turbine nacelle transferfunctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

St. Martin, Clara M.; Lundquist, Julie K.; Clifton, Andrew

Despite their potential as a valuable source of individual turbine power performance and turbine array energy production optimization information, nacelle-mounted anemometers have often been neglected because complex flows around the blades and nacelle interfere with their measurements. This work quantitatively explores the accuracy of and potential corrections to nacelle anemometer measurements to determine the degree to which they may be useful when corrected for these complex flows, particularly for calculating annual energy production (AEP) in the absence of other meteorological data. Using upwind meteorological tower measurements along with nacelle-based measurements from a General Electric (GE) 1.5sle model, we calculate empiricalmore » nacelle transfer functions (NTFs) and explore how they are impacted by different atmospheric and turbulence parameters. This work provides guidelines for the use of NTFs for deriving useful wind measurements from nacelle-mounted anemometers. Corrections to the nacelle anemometer wind speed measurements can be made with NTFs and used to calculate an AEP that comes within 1 % of an AEP calculated with upwind measurements. We also calculate unique NTFs for different atmospheric conditions defined by temperature stratification as well as turbulence intensity, turbulence kinetic energy, and wind shear. During periods of low stability as defined by the Bulk Richardson number ( RB), the nacelle-mounted anemometer underestimates the upwind wind speed more than during periods of high stability at some wind speed bins below rated speed, leading to a more steep NTF during periods of low stability. Similarly, during periods of high turbulence, the nacelle-mounted anemometer underestimates the upwind wind speed more than during periods of low turbulence at most wind bins between cut-in and rated wind speed. Based on these results, we suggest different NTFs be calculated for different regimes of atmospheric stability and turbulence for power performance validation purposes.« less

Atmospheric turbulence affects wind turbine nacelle transferfunctions

DOE PAGES

St. Martin, Clara M.; Lundquist, Julie K.; Clifton, Andrew; ...

2017-06-02

Despite their potential as a valuable source of individual turbine power performance and turbine array energy production optimization information, nacelle-mounted anemometers have often been neglected because complex flows around the blades and nacelle interfere with their measurements. This work quantitatively explores the accuracy of and potential corrections to nacelle anemometer measurements to determine the degree to which they may be useful when corrected for these complex flows, particularly for calculating annual energy production (AEP) in the absence of other meteorological data. Using upwind meteorological tower measurements along with nacelle-based measurements from a General Electric (GE) 1.5sle model, we calculate empiricalmore » nacelle transfer functions (NTFs) and explore how they are impacted by different atmospheric and turbulence parameters. This work provides guidelines for the use of NTFs for deriving useful wind measurements from nacelle-mounted anemometers. Corrections to the nacelle anemometer wind speed measurements can be made with NTFs and used to calculate an AEP that comes within 1 % of an AEP calculated with upwind measurements. We also calculate unique NTFs for different atmospheric conditions defined by temperature stratification as well as turbulence intensity, turbulence kinetic energy, and wind shear. During periods of low stability as defined by the Bulk Richardson number ( RB), the nacelle-mounted anemometer underestimates the upwind wind speed more than during periods of high stability at some wind speed bins below rated speed, leading to a more steep NTF during periods of low stability. Similarly, during periods of high turbulence, the nacelle-mounted anemometer underestimates the upwind wind speed more than during periods of low turbulence at most wind bins between cut-in and rated wind speed. Based on these results, we suggest different NTFs be calculated for different regimes of atmospheric stability and turbulence for power performance validation purposes.« less

A method for obtaining distributed surface flux measurements in complex terrain

NASA Astrophysics Data System (ADS)

Daniels, M. H.; Pardyjak, E.; Nadeau, D. F.; Barrenetxea, G.; Brutsaert, W. H.; Parlange, M. B.

2011-12-01

Sonic anemometers and gas analyzers can be used to measure fluxes of momentum, heat, and moisture over flat terrain, and with the proper corrections, over sloping terrain as well. While this method of obtaining fluxes is currently the most accurate available, the instruments themselves are costly, making installation of many stations impossible for most campaign budgets. Small, commercial automatic weather stations (Sensorscope) are available at a fraction of the cost of sonic anemometers or gas analyzers. Sensorscope stations use slow-response instruments to measure standard meteorological variables, including wind speed and direction, air temperature, humidity, surface skin temperature, and incoming solar radiation. The method presented here makes use of one sonic anemometer and one gas analyzer along with a dozen Sensorscope stations installed throughout the Val Ferret catchment in southern Switzerland in the summers of 2009, 2010 and 2011. Daytime fluxes are calculated using Monin-Obukhov similarity theory in conjunction with the surface energy balance at each Sensorscope station as well as at the location of the sonic anemometer and gas analyzer, where a suite of additional slow-response instruments were co-located. Corrections related to slope angle were made for wind speeds and incoming shortwave radiation measured by the horizontally-mounted cup anemometers and incoming solar radiation sensors respectively. A temperature correction was also applied to account for daytime heating inside the radiation shield on the slow-response temperature/humidity sensors. With these corrections, we find a correlation coefficient of 0.77 between u* derived using Monin-Obukhov similarity theory and that of the sonic anemometer. Calculated versus measured heat fluxes also compare well and local patterns of latent heat flux and measured surface soil moisture are correlated.

MEASUREMENT OF MOTION CORRECTED WIND VELOCITY USING AN AEROSTAT LOFTED SONIC ANEMOMETER

EPA Science Inventory

An aerostat-lofted, sonic anemometer was used to determine instantaneous 3 dimensional wind velocities at altitudes relevant to fire plume dispersion modeling. An integrated GPS, inertial measurement unit, and attitude heading and reference system corrected the wind data for th...

Compact rotating cup anemometer

NASA Technical Reports Server (NTRS)

Wellman, J. B.

1968-01-01

Compact, collapsible rotating cup anemometer is used in remote locations where portability and durability are factors in the choice of equipment. This lightweight instrument has a low wind-velocity threshold, is capable of withstanding large mechanical shocks while in its stowed configuration, and has fast response to wind fluctuations.

Flow disturbance due to presence of the vane anemometer

NASA Astrophysics Data System (ADS)

Bujalski, M.; Gawor, M.; Sobczyk, J.

2014-08-01

This paper presents the results of the preliminary experimental investigations of the disturbance of velocity field resulting from placing a vane anemometer in the analyzed air flow. Experiments were conducted in a wind tunnel with a closed loop. For the measurement process, Particle Image Velocimetry (PIV) method was used to visualize the flow structure and evaluate the instantaneous, two-dimensional velocity vector fields. Regions of inflow on the vane anemometer as well as flow behind it were examined. Ensemble averaged velocity distribution and root-mean-square (RMS) velocity fluctuations were determined. The results below are presented in the form of contour-velocity maps and profile plots. In order to investigate velocity fluctuations in the wake of vane anemometer with high temporal resolution hot-wire anemometry (HWA) technique was used. Frequency analysis by means of Fast Fourier Transform was carried out. The obtained results give evidence to a significant spatially and temporally complex flow disturbance in the vicinity of analyzed instrument.

A high-performance constant-temperature hot-wire anemometer

NASA Technical Reports Server (NTRS)

Watmuff, Jonathan H.

1994-01-01

A high-performance constant-temperature hot-wire anemometer has been designed based on a system theory analysis that can be extended to arbitrary order. A motivating factor behind the design was to achieve the highest possible frequency response while ensuring overall system stability. Based on these considerations, the design of the circuit and the selection of components is discussed in depth. Basic operating instructions are included in an operator's guide. The analysis is used to identify operating modes, observed in all anemometers, that are misleading in the sense that the operator can be deceived by interpreting an erroneous frequency response. Unlike other anemometers, this instrument provides front panel access to all the circuit parameters which affect system stability and frequency response. Instructions are given on how to identify and avoid these rather subtle and undesirable operating modes by appropriate adjustment of the controls. Details, such as fabrication drawings and a parts list, are provided to enable others to construct the instrument.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCaffrey, Katherine; Quelet, Paul T.; Choukulkar, Aditya

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 pairsmore » 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.« less

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

DOE PAGES

McCaffrey, Katherine; Quelet, Paul T.; Choukulkar, Aditya; ...

2017-02-02

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 pairsmore » 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.« less

Feasibility study of transit photon correlation anemometer for Ames Research Center unitary wind tunnel plan

NASA Technical Reports Server (NTRS)

Mayo, W. T., Jr.; Smart, A. E.

1979-01-01

A laser transit anemometer measured a two-dimensional vector velocity, using the transit time of scattering particles between two focused and parallel laser beams. The objectives were: (1) the determination of the concentration levels and light scattering efficiencies of naturally occurring, submicron particles in the NASA/Ames unitary wind tunnel and (2) the evaluation based on these measured data of a laser transit anemometer with digital correlation processing for nonintrusive velocity measurement in this facility. The evaluation criteria were the speeds at which point velocity measurements could be realized with this technique (as determined from computer simulations) for given accuracy requirements.

Hot film wall shear instrumentation for compressible boundary layer transition research

NASA Technical Reports Server (NTRS)

Schneider, Steven P.

1992-01-01

Experimental and analytical studies of hot film wall shear instrumentation were performed. A new hot film anemometer was developed and tested. The anemometer performance was not quite as good as that of commercial anemometers, but the cost was much less and testing flexibility was improved. The main focus of the project was a parametric study of the effect of sensor size and substrate material on the performance of hot film surface sensors. Both electronic and shock-induced flow experiments were performed to determine the sensitivity and frequency response of the sensors. The results are presented in Michael Moen's M.S. thesis, which is appended. A condensed form of the results was also submitted for publication.

Mathematical Analysis of the Effect of Rotor Geometry on Cup Anemometer Response

PubMed Central

Sanz-Andrés, Ángel; Sorribes-Palmer, Félix

2014-01-01

The calibration coefficients of two commercial anemometers equipped with different rotors were studied. The rotor cups had the same conical shape, while the size and distance to the rotation axis varied. The analysis was based on the 2-cup positions analytical model, derived using perturbation methods to include second-order effects such as pressure distribution along the rotating cups and friction. The comparison with the experimental data indicates a nonuniform distribution of aerodynamic forces on the rotating cups, with higher forces closer to the rotating axis. The 2-cup analytical model is proven to be accurate enough to study the effect of complex forces on cup anemometer performance. PMID:25110735

Comparison of two- and three-dimensional flow computations with laser anemometer measurements in a transonic compressor rotor

NASA Technical Reports Server (NTRS)

Chima, R. V.; Strazisar, A. J.

1982-01-01

Two and three dimensional inviscid solutions for the flow in a transonic axial compressor rotor at design speed are compared with probe and laser anemometers measurements at near-stall and maximum-flow operating points. Experimental details of the laser anemometer system and computational details of the two dimensional axisymmetric code and three dimensional Euler code are described. Comparisons are made between relative Mach number and flow angle contours, shock location, and shock strength. A procedure for using an efficient axisymmetric code to generate downstream pressure input for computationally expensive Euler codes is discussed. A film supplement shows the calculations of the two operating points with the time-marching Euler code.

AVOSS Windline at Dallas/Ft. Worth Airport Volume 2 Data Base of Ground-Based Anemometer Measurements of Wake Vortices

DOT National Transportation Integrated Search

2001-05-01

A 259-meter windline, with horizontal and vertical single-axis anemometers mounted on 9-meter poles, was installed at the Dallas/Ft. Worth Airport under the approach to Runway 17C, as part of NASA's Aircraft VOrtex Spacing System (AVOSS) development ...

Four spot laser anemometer and optical access techniques for turbine applications

NASA Astrophysics Data System (ADS)

Wernet, Mark P.

A time-of-flight anemometer (TOFA) system utilizing a spatial lead-lag filter for bipolar pulse generation has been constructed and tested. This system, called a four-spot laser anemometer, was specifically designed for use in high-speed, turbulent flows in the presence of walls or surfaces. The TOFA system uses elliptical spots to increase the flow acceptance angle to be comparable with that of a fringe-type anemometer. The tightly focused spots used in the four spot yield excellent flare light rejection capabilities. Good results have been obtained to 75 microns normal to a surface, with an f/2.5 collection lens. This system is being evaluated for use in a warm turbine facility. Results from both a particle-lag velocity experiment and boundary layer profiles will be discussed. In addition, an analysis of the use of curved windows in a turbine casing will be presented. Curved windows, matching the inner radius of the turbine casing, preserve the flow conditions, but introduce astigmatic aberrations. A correction optic was designed that virtually eliminates these astigmatic aberrations throughout the intrablade survey region for normal incidence.

Four spot laser anemometer and optical access techniques for turbine applications

NASA Astrophysics Data System (ADS)

Wernet, Mark P.

A time-of-flight anemometer (TOFA) system, utilizing a spatial lead-lag filter for bipolar pulse generation was constructed and tested. This system, called a Four Spot Laser Anemometer, was specifically designed for use in high speed, turbulent flows in the presence of walls or surfaces. The TOFA system uses elliptical spots to increase the flow acceptance angle to be comparable with that of a fringe type anemometer. The tightly focused spots used in the Four Spot yield excellent flare light rejection capabilities. Good results were obtained to 75 microns normal to a surface, with a f/2.5 collecting lens. This system is being evaluated for use in a warm turbine facility. Results from both a particle lag velocity experiment and boundary layer profiles will be discussed. In addition, an analysis of the use of curved windows in a turbine casing will be presented. Curved windows, matching the inner radius of the turbine casing, preserve the flow conditions, but introduce astigmatic aberrations. A correction optic was designed that virtually eliminates these astigmatic aberrations throughout the intrablade survey region for normal incidence.

Four spot laser anemometer and optical access techniques for turbine applications

NASA Technical Reports Server (NTRS)

Wernet, Mark P.

1987-01-01

A time-of-flight anemometer (TOFA) system utilizing a spatial lead-lag filter for bipolar pulse generation has been constructed and tested. This system, called a four-spot laser anemometer, was specifically designed for use in high-speed, turbulent flows in the presence of walls or surfaces. The TOFA system uses elliptical spots to increase the flow acceptance angle to be comparable with that of a fringe-type anemometer. The tightly focused spots used in the four spot yield excellent flare light rejection capabilities. Good results have been obtained to 75 microns normal to a surface, with an f/2.5 collection lens. This system is being evaluated for use in a warm turbine facility. Results from both a particle-lag velocity experiment and boundary layer profiles will be discussed. In addition, an analysis of the use of curved windows in a turbine casing will be presented. Curved windows, matching the inner radius of the turbine casing, preserve the flow conditions, but introduce astigmatic aberrations. A correction optic was designed that virtually eliminates these astigmatic aberrations throughout the intrablade survey region for normal incidence.

Four spot laser anemometer and optical access techniques for turbine applications

NASA Technical Reports Server (NTRS)

Wernet, Mark P.

1987-01-01

A time-of-flight anemometer (TOFA) system, utilizing a spatial lead-lag filter for bipolar pulse generation was constructed and tested. This system, called a Four Spot Laser Anemometer, was specifically designed for use in high speed, turbulent flows in the presence of walls or surfaces. The TOFA system uses elliptical spots to increase the flow acceptance angle to be comparable with that of a fringe type anemometer. The tightly focused spots used in the Four Spot yield excellent flare light rejection capabilities. Good results were obtained to 75 microns normal to a surface, with a f/2.5 collecting lens. This system is being evaluated for use in a warm turbine facility. Results from both a particle lag velocity experiment and boundary layer profiles will be discussed. In addition, an analysis of the use of curved windows in a turbine casing will be presented. Curved windows, matching the inner radius of the turbine casing, preserve the flow conditions, but introduce astigmatic aberrations. A correction optic was designed that virtually eliminates these astigmatic aberrations throughout the intrablade survey region for normal incidence.

Atmospheric Effects on Radio Frequency (RF) Wave Propagation in a Humid, Near-Surface Environment

DTIC Science & Technology

2010-03-01

additional IR temperature and Campbell water temperature probes, as well as a 3-D sonic anemometer, pyranometer , and LI-COR open path gas analyzer for...Zonen CNR-1 pyranometer . Lastly, the Campbell sonic anemometer (CSAT3) and LI- COR (CS7500) were extended 2.5 meters over the water from an

Four-Spot Time-Of-Flight Laser Anemometer For Turbomachinery

NASA Technical Reports Server (NTRS)

Wernet, Mark P.; Skoch, Gary J.

1995-01-01

Two-color, four-spot time-of-flight laser anemometer designed for measuring flow velocity within narrow confines of small centrifugal compressor. Apparatus well suited for measuring fast (typical speeds 160 to 700 m/s), highly turbulent gas flows in turbomachinery. Other potential applications include measurement of gas flows in pipelines and in flows from explosions.

Optimization of fringe-type laser anemometers for turbine engine component testing

NASA Technical Reports Server (NTRS)

Seasholtz, R. G.; Oberle, L. G.; Weikle, D. H.

1984-01-01

The fringe type laser anemometer is analyzed using the Cramer-Rao bound for the variance of the estimate of the Doppler frequency as a figure of merit. Mie scattering theory is used to calculate the Doppler signal wherein both the amplitude and phase of the scattered light are taken into account. The noise from wall scatter is calculated using the wall bidirectional reflectivity and the irradiance of the incident beams. A procedure is described to determine the optimum aperture mask for the probe volume located a given distance from a wall. The expected performance of counter type processors is also discussed in relation to the Cramer-Rao bound. Numerical examples are presented for a coaxial backscatter anemometer.

Design and Study of a Low-Cost Laboratory Model Digital Wind Power Meter

ERIC Educational Resources Information Center

Radhakrishnan, Rugmini; Karthika, S.

2010-01-01

A vane-type low-cost laboratory model anemometer cum power meter is designed and constructed for measuring low wind energy created from accelerating fluids. The constructed anemometer is a device which records the electrical power obtained by the conversion of wind power using a wind sensor coupled to a DC motor. It is designed for its…

All sonic anemometers need to correct for transducer and structural shadowing in their velocity measurements

Treesearch

John M. Frank; William J. Massman; Edward Swiatek; Herb A. Zimmerman; Brent E. Ewers

2016-01-01

Sonic anemometry is fundamental to all eddy-covariance studies of surface energy and ecosystem carbon and water balance. Recent studies have shown that some nonorthogonal anemometers underestimate vertical wind. Here it is hypothesized that this is due to a lack of transducer and structural shadowing correction. This is tested with a replicated intercomparison...

A Bayesian model to correct underestimated 3-D wind speeds from sonic anemometers increases turbulent components of the surface energy balance

Treesearch

John M. Frank; William J. Massman; Brent E. Ewers

2016-01-01

Sonic anemometers are the principal instruments in micrometeorological studies of turbulence and ecosystem fluxes. Common designs underestimate vertical wind measurements because they lack a correction for transducer shadowing, with no consensus on a suitable correction. We reanalyze a subset of data collected during field experiments in 2011 and 2013 featuring two or...

Characteristics of Turbulent Airflow Deduced from Rapid Surface Thermal Fluctuations: An Infrared Surface Anemometer

NASA Astrophysics Data System (ADS)

Aminzadeh, Milad; Breitenstein, Daniel; Or, Dani

2017-12-01

The intermittent nature of turbulent airflow interacting with the surface is readily observable in fluctuations of the surface temperature resulting from the thermal imprints of eddies sweeping the surface. Rapid infrared thermography has recently been used to quantify characteristics of the near-surface turbulent airflow interacting with the evaporating surfaces. We aim to extend this technique by using single-point rapid infrared measurements to quantify properties of a turbulent flow, including surface exchange processes, with a view towards the development of an infrared surface anemometer. The parameters for the surface-eddy renewal (α and β ) are inferred from infrared measurements of a single-point on the surface of a heat plate placed in a wind tunnel with prescribed wind speeds and constant mean temperatures of the surface. Thermally-deduced parameters are in agreement with values obtained from standard three-dimensional ultrasonic anemometer measurements close to the plate surface (e.g., α = 3 and β = 1/26 (ms)^{-1} for the infrared, and α = 3 and β = 1/19 (ms)^{-1} for the sonic-anemometer measurements). The infrared-based turbulence parameters provide new insights into the role of surface temperature and buoyancy on the inherent characteristics of interacting eddies. The link between the eddy-spectrum shape parameter α and the infrared window size representing the infrared field of view is investigated. The results resemble the effect of the sampling height above the ground in sonic anemometer measurements, which enables the detection of larger eddies with higher values of α . The physical basis and tests of the proposed method support the potential for remote quantification of the near-surface momentum field, as well as scalar-flux measurements in the immediate vicinity of the surface.

Wind tunnel test of Teledyne Geotech model 1564B cup anemometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parker, M.J.; Addis, R.P.

1991-04-04

The Department of Energy (DOE) Environment, Safety and Health Compliance Assessment (Tiger Team) of the Savannah River Site (SRS) questioned the method by which wind speed sensors (cup anemometers) are calibrated by the Environmental Technology Section (ETS). The Tiger Team member was concerned that calibration data was generated by running the wind tunnel to only 26 miles per hour (mph) when speeds exceeding 50 mph are readily obtainable. A wind tunnel experiment was conducted and confirmed the validity of the practice. Wind speeds common to SRS (6 mph) were predicted more accurately by 0--25 mph regression equations than 0--50 mphmore » regression equations. Higher wind speeds were slightly overpredicted by the 0--25 mph regression equations when compared to 0--50 mph regression equations. However, the greater benefit of more accurate lower wind speed predictions accuracy outweight the benefit of slightly better high (extreme) wind speed predictions. Therefore, it is concluded that 0--25 mph regression equations should continue to be utilized by ETS at SRS. During the Department of Energy Tiger Team audit, concerns were raised about the calibration of SRS cup anemometers. Wind speed is measured by ETS with Teledyne Geotech model 1564B cup anemometers, which are calibrated in the ETS wind tunnel. Linear regression lines are fitted to data points of tunnel speed versus anemometer output voltages up to 25 mph. The regression coefficients are then implemented into the data acquisition computer software when an instrument is installed in the field. The concern raised was that since the wind tunnel at SRS is able to generate a maximum wind speed higher than 25 mph, errors may be introduced in not using the full range of the wind tunnel.« less

Wind tunnel test of Teledyne Geotech model 1564B cup anemometer

NASA Astrophysics Data System (ADS)

Parker, M. J.; Addis, R. P.

1991-04-01

The Department of Energy (DOE) Environment, Safety, and Health Compliance Assessment (Tiger Team) of the Savannah River Site (SRS) questioned the method by which wind speed sensors (cup anemometers) are calibrated by the Environmental Technology Section (ETS). The Tiger Team member was concerned that calibration data was generated by running the wind tunnel to only 26 miles per hour (mph) when speeds exceeding 50 mph are readily obtainable. A wind tunnel experiment was conducted and confirmed the validity of the practice. Wind speeds common to SRS (6 mph) were predicted more accurately by 0-25 mph regression equations than 0-50 mph regression equations. Higher wind speeds were slightly overpredicted by the 0-25 mph regression equations when compared to 0-50 mph regression equations. However, the greater benefit of more accurate lower wind speed predictions accuracy outweigh the benefit of slightly better high (extreme) wind speed predictions. Therefore, it is concluded that 0-25 mph regression equations should continue to be utilized by ETS at SRS. During the Department of Energy Tiger Team audit, concerns were raised about the calibration of SRS cup anemometers. Wind speed is measured by ETS with Teledyne Geotech model 1564B cup anemometers, which are calibrated in the ETS wind tunnel. Linear regression lines are fitted to data points of tunnel speed versus anemometer output voltages up to 25 mph. The regression coefficients are then implemented into the data acquisition computer software when an instrument is installed in the field. The concern raised was that since the wind tunnel at SRS is able to generate a maximum wind speed higher than 25 mph, errors may be introduced in not using the full range of the wind tunnel.

Three component laser anemometer measurements in an annular cascade of core turbine vanes with contoured end wall

NASA Technical Reports Server (NTRS)

Goldman, Louis J.; Seasholtz, Richard G.

1988-01-01

The three mean velocity components were measured in a full-scale annular turbine stator cascade with contoured hub end wall using a newly developed laser anemometer system. The anemometer consists of a standard fringe configuration using fluorescent seed particles to measure the axial and tangential components. The radial component is measured with a scanning confocal Fabry-Perot interferometer. These two configurations are combined in a single optical system that can operate simultaneously in a backscatter mode through a single optical access port. Experimental measurements were obtained both within and downstream of the stator vane row and compared with calculations from a three-dimensional inviscid computer program. In addition, detailed calibration procedures are described that were used, prior to the experiment, to accurately determine the laser beam probe volume location relative to the cascade hardware.

Hot wire anemometer measurements in the unheated air flow tests of the SRB nozzle-to-case joint

NASA Technical Reports Server (NTRS)

Ramachandran, N.

1988-01-01

Hot-Wire Anemometer measurements made in the Solid Rocket Booster (SRB) nozzle-to-case joint are discussed. The study was undertaken to glean additional information on the circumferential flow induced in the SRB nozzle joint and the effect of this flow on the insulation bonding flaws. The tests were conducted on a full-scale, 2-D representation of a 65-in long segment of the SRB nozzle joint, with unheated air as the working fluid. Both the flight Mach number and Reynolds number were matched simultaneously and different pressure gradients imposed along the joint face were investigated. Hot-wire anemometers were used to obtain velocity data for different joint gaps and debond configurations. The procedure adopted for hot-wire calibration and use is outlined and the results from the tests summarized.

How well can we measure the vertical wind speed? Implications for fluxes of energy and mass

Treesearch

John Kochendorfer; Tilden P. Meyers; John Frank; William J. Massman; Mark W. Heuer

2012-01-01

Sonic anemometers are capable of measuring the wind speed in all three dimensions at high frequencies (10­50 Hz), and are relied upon to estimate eddy-covariance-based fluxes of mass and energy over a wide variety of surfaces and ecosystems. In this study, wind-velocity measurement errors from a three-dimensional sonic anemometer with a nonorthogonal transducer...

European Scientific Notes. Volume 33, Number 5,

DTIC Science & Technology

1979-05-31

Towers I and III will also have six anemometers. Turbulence meas- urements will be carried out with three- dimensional sonic anemometers, a bivane and a...project management sions, and atmospheric infrasonic waves. of S. Ullaland of the Univ. of Bergen The auroral x-ray fluxes are measured in Norway. The...omnidirectional x-ray fluxes and electric fields, VLF emissions, and electric fields contains one uncol- and atmospheric infrasonic waves. limated x-ray

Low-speed airspeed calibration data for a single-engine research-support aircraft

NASA Technical Reports Server (NTRS)

Holmes, B. J.

1980-01-01

A standard service airspeed system on a single engine research support airplane was calibrated by the trailing anemometer method. The effects of flaps, power, sideslip, and lag were evaluated. The factory supplied airspeed calibrations were not sufficiently accurate for high accuracy flight research applications. The trailing anemometer airspeed calibration was conducted to provide the capability to use the research support airplane to perform pace aircraft airspeed calibrations.

Adaptive control of turbulence intensity is accelerated by frugal flow sampling.

PubMed

Quinn, Daniel B; van Halder, Yous; Lentink, David

2017-11-01

The aerodynamic performance of vehicles and animals, as well as the productivity of turbines and energy harvesters, depends on the turbulence intensity of the incoming flow. Previous studies have pointed at the potential benefits of active closed-loop turbulence control. However, it is unclear what the minimal sensory and algorithmic requirements are for realizing this control. Here we show that very low-bandwidth anemometers record sufficient information for an adaptive control algorithm to converge quickly. Our online Newton-Raphson algorithm tunes the turbulence in a recirculating wind tunnel by taking readings from an anemometer in the test section. After starting at 9% turbulence intensity, the algorithm converges on values ranging from 10% to 45% in less than 12 iterations within 1% accuracy. By down-sampling our measurements, we show that very-low-bandwidth anemometers record sufficient information for convergence. Furthermore, down-sampling accelerates convergence by smoothing gradients in turbulence intensity. Our results explain why low-bandwidth anemometers in engineering and mechanoreceptors in biology may be sufficient for adaptive control of turbulence intensity. Finally, our analysis suggests that, if certain turbulent eddy sizes are more important to control than others, frugal adaptive control schemes can be particularly computationally effective for improving performance. © 2017 The Author(s).

Overview of and first observations from the TILDAE High-Altitude Balloon Mission

NASA Astrophysics Data System (ADS)

Maruca, Bennett A.; Marino, Raffaele; Sundkvist, David; Godbole, Niharika H.; Constantin, Stephane; Carbone, Vincenzo; Zimmerman, Herb

2017-04-01

Though the presence of intermittent turbulence in the stratosphere has been well established, much remains unknown about it. In situ observations of this phenomenon, which have provided the greatest details of it, have mostly been achieved via sounding balloons (i.e., small balloons which burst at peak altitude) carrying constant-temperature hot-wire anemometers (CTAs). The Turbulence and Intermittency Long-Duration Atmospheric Experiment (TILDAE) was developed to test a new paradigm for stratospheric observations. Rather than flying on a sounding balloon, TILDAE was incorporated as an add-on experiment to the payload of a NASA long-duration balloon mission that launched in January 2016 from McMurdo Station, Antarctica. Furthermore, TILDAE's key instrument was a sonic anemometer, which (relative to a CTA) provides better-calibrated measurements of wind velocity and a more robust separation of velocity components. During the balloon's ascent, TILDAE's sonic anemometer provided atmospheric measurements up to an altitude of about 18 km, beyond which the ambient air pressure was too low for the instrument to function properly. Efforts are currently underway to scientifically analyze these observations of small-scale fluctuations in the troposphere, tropopause, and stratosphere and to develop strategies for increasing the maximum operating altitude of the sonic anemometer.

A comparison of a coaxial focused laser Doppler system in atmospheric measurements

NASA Technical Reports Server (NTRS)

Karaki, S.

1973-01-01

Measurements of atmospheric velocities and turbulence with the laser Doppler system were obtained, and the results compared with cup anemometer and hot-wire measurements in the same wind field. The laser Doppler velocimeter (LDV) is described along with the test procedures. It was found that mean values determined from the LDV data are within 5% of other anemometer data for long time periods, and the LDV measures higher velocities.

Silicon Carbide High Temperature Anemometer and Method for Assembling the Same

NASA Technical Reports Server (NTRS)

Okojie, Robert S. (Inventor); Fralick, Gustave C. (Inventor); Saad, George J. (Inventor)

2003-01-01

A high temperature anemometer includes a pair of substrates. One of the substrates has a plurality of electrodes on a facing surface, while the other of the substrates has a sensor cavity on a facing surface. A sensor is received in the sensor cavity, wherein the sensor has a plurality of bondpads, and wherein the bond pads contact the plurality of electrodes when the facing surfaces are mated with one another. The anemometer further includes a plurality of plug-in pins, wherein the substrate with the cavity has a plurality of trenches with each one receiving a plurality of plug-in pins. The plurality of plug-in pins contact the plurality of electrodes when the substrates are mated with one another. The sensor cavity is at an end of one of the substrates such that the sensor partially extends from the substrate. The sensor and the substrates are preferably made of silicon carbide.

Comparison of surface wind stress measurements - Airborne radar scatterometer versus sonic anemometer

NASA Technical Reports Server (NTRS)

Brucks, J. T.; Leming, T. D.; Jones, W. L.

1980-01-01

Sea surface wind stress measurements recorded by a sonic anemometer are correlated with airborne scatterometer measurements of ocean roughness (cross section of radar backscatter) to establish the accuracy of remotely sensed data and assist in the definition of geophysical algorithms for the scatterometer sensor aboard Seasat A. Results of this investigation are as follows: Comparison of scatterometer and sonic anemometer wind stress measurements are good for the majority of cases; however, a tendency exists for scatterometer wind stress to be somewhat high for higher wind conditions experienced in this experiment (6-9 m/s). The scatterometer wind speed algorithm tends to overcompute the higher wind speeds by approximately 0.5 m/s. This is a direct result of the scatterometer overestimate of wind stress from which wind speeds are derived. Algorithmic derivations of wind speed and direction are, in most comparisons, within accuracies defined by Seasat A scatterometer sensor specifications.

Performance and analysis of a three-dimensional nonorthogonal laser Doppler anemometer

NASA Technical Reports Server (NTRS)

Snyder, P. K.; Orloff, K. L.; Aoyagi, K.

1981-01-01

A three dimensional laser Doppler anemometer with a nonorthogonal third axis coupled by 14 deg was designed and tested. A highly three dimensional flow field of a jet in a crossflow was surveyed to test the three dimensional capability of the instrument. Sample data are presented demonstrating the ability of the 3D LDA to resolve three orthogonal velocity components. Modifications to the optics, signal processing electronics, and data reduction methods are suggested.

Thermal Remote Anemometer Device

NASA Technical Reports Server (NTRS)

Heyman, Joseph S.; Heath, D. Michele; Winfree, William P.; Miller, William E.; Welch, Christopher S.

1988-01-01

Thermal Remote Anemometer Device developed for remote, noncontacting, passive measurement of thermal properties of sample. Model heated locally by scanning laser beam and cooled by wind in tunnel. Thermal image of model analyzed to deduce pattern of airflow around model. For materials applications, system used for evaluation of thin films and determination of thermal diffusivity and adhesive-layer contact. For medical applications, measures perfusion through skin to characterize blood flow and used to determine viabilities of grafts and to characterize tissues.

Wind speed statistics for Goldstone, California, anemometer sites

NASA Technical Reports Server (NTRS)

Berg, M.; Levy, R.; Mcginness, H.; Strain, D.

1981-01-01

An exploratory wind survey at an antenna complex was summarized statistically for application to future windmill designs. Data were collected at six locations from a total of 10 anemometers. Statistics include means, standard deviations, cubes, pattern factors, correlation coefficients, and exponents for power law profile of wind speed. Curves presented include: mean monthly wind speeds, moving averages, and diurnal variation patterns. It is concluded that three of the locations have sufficiently strong winds to justify consideration for windmill sites.

Experimental Investigation of the Robinson-Type Cup Anemometer

NASA Technical Reports Server (NTRS)

Brevoort, M J; Joyner, U T

1936-01-01

This report presents the results of wind tunnel tests on a Robinson-type anemometer. The investigation covered force measurements on individual cups, as well as static and dynamic torque measurements and calibrations on complete cup wheels. In the tests on individual cups 5 cup forms were used and in the measurements on complete cup wheels 4 cup wheels with 3 arm lengths for each cup wheel were tested. All the results are presented in graphical form.

Assessment and Computerized Modeling of the Environmental Deposition of Military Smokes

DTIC Science & Technology

1990-10-05

assumption of randomness implies that past knowl- I edge has no bearing on the occurrence of any f, ture event1, the probability distribution of finding...of these levels, the wind speed was measured with a Gill three-cup anemometer. This anemometer consists of a vertical bearing -mounted spindle with...first class of instruments we have the ý-gage, the piezoelectric microbalance, and the tapered element oscillating microbalance. Other types of real-time

Urban Turbulence Velocity Spectra From JU2003 Observation

DTIC Science & Technology

2014-12-01

55.8(F), 69.7(G), and 83.2(H) m above ground level (AGL). The sonic anemometers (R.M. Young model 81000) measured 3 wind components and temperature at a... Sonic anemometer data taken using Lawrence Livermore National Laboratory’s 83 m pseudo tower from JU2003 are analyzed. We present the results of...atmospheric boundary layer over flat terrains have been well studied (Busch and Panofsky, 1968; Panofsky and Dutton, 1984; Kaimal and Finnigan

Fast-Response Fiber-Optic Anemometer with Temperature Self-Compensation

DTIC Science & Technology

2015-05-18

be considered to be a function of time only. With a heating source within the sensor, the model for LSA is expressed as [13], ( ) ( ),s w s s shA ... shA C Vρ , in the exponent of the transient term in RHS of Eq. (7) characterizes the response time of the anemometer. Conversion of the temperature...circulator, and the reflected signal night was acquired by a high-speed spectrometer (Ibsen Photonics, I-MON 256 USB) which was connected to a computer

Mid-Term Progress Report on the Development of Army Closed Cycle Circulator (CCC) System.

DTIC Science & Technology

1979-09-20

installation of the rotor assembly. The compressor shaft is sealed with a Crane Type 28 Kinetic Wedge gas seal for positive static sealing. A unitized...Pressure ratio 1.91 Horsepower 134 R (Molecular weight 18.67) 82.76 The compressor is fitted with a Crane Packing Company Type 28 gas seal. This seal...simply reading a digital voltmeter which is hooked up to the anemometer. The only preparation that the anemometer requires is that the operating

A 4-spot time-of-flight anemometer for small centrifugal compressor velocity measurements

NASA Technical Reports Server (NTRS)

Wernet, Mark P.; Skoch, Gary J.

1992-01-01

The application of laser anemometry techniques in turbomachinery facilities is a challenging dilemma requiring an anemometer system with special qualities. Here, we describe the use of a novel laser anemometry technique applied to a small 4.5 kg/s, 4:1 pressure ratio centrifugal compressor. Sample velocity profiles across the blade pitch are presented for a single location along the rotor. The results of the intra-blade passage velocity measurements will ultimately be used to verify CFD 3-D viscous code predictions.

A 4-spot time-of-flight anemometer for small centrifugal compressor velocity measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wernet, M.P.; Skoch, G.J.

1992-07-01

The application of laser anemometry techniques in turbomachinery facilities is a challenging dilemma requiring an anemometer system with special qualities. Here, we describe the use of a novel laser anemometry technique applied to a small 4.5 kg/s, 4:1 pressure ratio centrifugal compressor. Sample velocity profiles across the blade pitch are presented for a single location along the rotor. The results of the intra-blade passage velocity measurements will ultimately be used to verify CFD 3-D viscous code predictions.

Acquisition of Turbulence Data Using the DST Group Constant-Temperature Hot-Wire Anemometer System

DTIC Science & Technology

2015-10-01

fluctuations in the low-speed wind tunnel at DST Group. The use of both single- wire and crossed- wire (2 wire ) probes is described. Areas covered include a...fluid-flow studies, including testing of models of aircraft, ships and submarines in wind and water tunnels. Hot- wire anemometers and associated hot...spectra of velocity fluctuations in the low-speed wind tunnel at DST Group. The use of both single- wire and crossed- wire (2 wires ) probes is

Three-component laser anemometer measurement systems

NASA Technical Reports Server (NTRS)

Goldman, Louis J.

1991-01-01

A brief overview of the different laser anemometer (LA) optical designs available is presented. Then, the LA techniques that can be used to design a three-component measurement system for annular geometries are described. Some of the facility design considerations unique to these LA systems are also addressed. Following this, the facilities and the LA systems that were used to successfully measure the three components of velocity in the blading of annular-flow machines are reviewed. Finally, possible LA system enhancements and future research directions are presented.

Laser transit anemometer measurements of a JANNAF nozzle base velocity flow field

NASA Technical Reports Server (NTRS)

Hunter, William W., Jr.; Russ, C. E., Jr.; Clemmons, J. I., Jr.

1990-01-01

Velocity flow fields of a nozzle jet exhausting into a supersonic flow were surveyed. The measurements were obtained with a laser transit anemometer (LTA) system in the time domain with a correlation instrument. The LTA data is transformed into the velocity domain to remove the error that occurs when the data is analyzed in the time domain. The final data is shown in velocity vector plots for positions upstream, downstream, and in the exhaust plane of the jet nozzle.

SiC-Based Miniature High-Temperature Cantilever Anemometer

NASA Technical Reports Server (NTRS)

Okojie, Robert S.; Fralick, Gustave; Saad, George J.

2004-01-01

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.

A comparison of disturbance levels measured in hypersonic tunnels using a hot-wire anemometer and a pitot pressure probe.

NASA Technical Reports Server (NTRS)

Stainback, P. C.; Wagner, R. D.

1972-01-01

Disturbance levels were measured in the test section of a Mach 5 blowdown jet using a constant-current, hot-wire anemometer and a pressure transducer. The disturbance levels, measured by the two instruments and normalized by local mean values, agreed within about 30%, with the pitot data higher than the hot-wire data. The rms disturbance levels measured with the hot-wire anemometer and converted to pitot pressures using a quasi-steady flow analysis, were about two-thirds the levels measured with the pitot probe. The variation of the normalized rms disturbance levels with stagnation pressure indicated that transition occurred in the boundary layer on the nozzle wall and influenced the outputs of the instruments located at the exit of the nozzle when the total pressure was about 35 N/sq cm. Below this pressure the disturbance levels decreased markedly. At higher pressures the disturbances were predominantly aerodynamic noise generated by the turbulent boundary layer on the nozzle wall.

Thermal transient anemometer

DOEpatents

Bailey, James L.; Vresk, Josip

1989-01-01

A thermal transient anemometer having a thermocouple probe which is utilized to measure the change in temperature over a period of time to provide a measure of fluid flow velocity. The thermocouple probe is located in the fluid flow path and pulsed to heat or cool the probe. The cooling of the heated probe or the heating of the cooled probe from the fluid flow over a period of time is measured to determine the fluid flow velocity. The probe is desired to be locally heated near the tip to increase the efficiency of devices incorporating the probe.

Planarised optical fiber composite using flame hydrolysis deposition demonstrating an integrated FBG anemometer.

PubMed

Holmes, Christopher; Gates, James C; Smith, Peter G R

2014-12-29

This paper reports for the first time a planarised optical fiber composite formed using Flame Hydrolysis Deposition (FHD). As a way of format demonstration a Micro-Opto-Electro-Mechanical (MOEMS) hot wire anemometer is formed using micro-fabrication processing. The planarised device is rigidly secured to a silicon wafer using optical quality doped silica that has been deposited using flame hydrolysis and consolidated at high temperature. The resulting structure can withstand temperatures exceeding 580K and is sensitive enough to resolve free and forced convection interactions at low fluid velocity.

Turbulence fluxes and variances measured with a sonic anemometer mounted on a tethered balloon

NASA Astrophysics Data System (ADS)

Canut, Guylaine; Couvreux, Fleur; Lothon, Marie; Legain, Dominique; Piguet, Bruno; Lampert, Astrid; Maurel, William; Moulin, Eric

2016-09-01

This study presents the first deployment in field campaigns of a balloon-borne turbulence probe, developed with a sonic anemometer and an inertial motion sensor suspended below a tethered balloon. This system measures temperature and horizontal and vertical wind at high frequency and allows the estimation of heat and momentum fluxes as well as turbulent kinetic energy in the lower part of the boundary layer. The system was validated during three field experiments with different convective boundary-layer conditions, based on turbulent measurements from instrumented towers and aircraft.

Method for making a hot wire anemometer and product thereof

NASA Technical Reports Server (NTRS)

Milkulla, V. (Inventor)

1977-01-01

A hot wire anemometer probe is described that includes a ceramic body supporting two conductive rods parallel to each other. The body has a narrow edge surface from which the rods protrude. A probe wire is welded to the rods and extends along the edge surface. A ceramic adhesive is used to secure the probe wire to the surface so that the probe wire is rigid. A method for fabricating the probe is also described in which the body is molded and precisely shaped by machining techniques before the probe wires are installed.

Evaluation of Probe-Induced Flow Distortion of Campbell CSAT3 Sonic Anemometers by Numerical Simulation

NASA Astrophysics Data System (ADS)

Huq, Sadiq; De Roo, Frederik; Foken, Thomas; Mauder, Matthias

2017-10-01

The Campbell CSAT3 sonic anemometer is one of the most popular instruments for turbulence measurements in basic micrometeorological research and ecological applications. While measurement uncertainty has been characterized by field experiments and wind-tunnel studies in the past, there are conflicting estimates, which motivated us to conduct a numerical experiment using large-eddy simulation to evaluate the probe-induced flow distortion of the CSAT3 anemometer under controlled conditions, and with exact knowledge of the undisturbed flow. As opposed to wind-tunnel studies, we imposed oscillations in both the vertical and horizontal velocity components at the distinct frequencies and amplitudes found in typical turbulence spectra in the surface layer. The resulting flow-distortion errors for the standard deviations of the vertical velocity component range from 3 to 7%, and from 1 to 3% for the horizontal velocity component, depending on the azimuth angle. The magnitude of these errors is almost independent of the frequency of wind speed fluctuations, provided the amplitude is typical for surface-layer turbulence. A comparison of the corrections for transducer shadowing proposed by both Kaimal et al. (Proc Dyn Flow Conf, 551-565, 1978) and Horst et al. (Boundary-Layer Meteorol 155:371-395, 2015) show that both methods compensate for a larger part of the observed error, but do not sufficiently account for the azimuth dependency. Further numerical simulations could be conducted in the future to characterize the flow distortion induced by other existing types of sonic anemometers for the purposes of optimizing their geometry.

Field intercomparison of prevailing sonic anemometers

NASA Astrophysics Data System (ADS)

Mauder, Matthias; Zeeman, Matthias J.

2018-01-01

Three-dimensional sonic anemometers are the core component of eddy covariance systems, which are widely used for micrometeorological and ecological research. In order to characterize the measurement uncertainty of these instruments we present and analyse the results from a field intercomparison experiment of six commonly used sonic anemometer models from four major manufacturers. These models include Campbell CSAT3, Gill HS-50 and R3, METEK uSonic-3 Omni, R. M. Young 81000 and 81000RE. The experiment was conducted over a meadow at the TERENO/ICOS site DE-Fen in southern Germany over a period of 16 days in June of 2016 as part of the ScaleX campaign. The measurement height was 3 m for all sensors, which were separated by 9 m from each other, each on its own tripod, in order to limit contamination of the turbulence measurements by adjacent structures as much as possible. Moreover, the high-frequency data from all instruments were treated with the same post-processing algorithm. In this study, we compare the results for various turbulence statistics, which include mean horizontal wind speed, standard deviations of vertical wind velocity and sonic temperature, friction velocity, and the buoyancy flux. Quantitative measures of uncertainty, such as bias and comparability, are derived from these results. We find that biases are generally very small for all sensors and all computed variables, except for the sonic temperature measurements of the two Gill sonic anemometers (HS and R3), confirming a known transducer-temperature dependence of the sonic temperature measurement. The best overall agreement between the different instruments was found for the mean wind speed and the buoyancy flux.

A Hot-Polymer Fiber Fabry–Perot Interferometer Anemometer for Sensing Airflow

PubMed Central

Lee, Cheng-Ling; Liu, Kai-Wen; Luo, Shi-Hong; Wu, Meng-Shan; Ma, Chao-Tsung

2017-01-01

This work proposes the first hot-polymer fiber Fabry–Perot interferometer (HPFFPI) anemometer for sensing airflow. The proposed HPFFPI is based on a single-mode fiber (SMF) endface that is attached to a UV-cured polymer to form an ultracompact fiber Fabry–Perot microcavity. The proposed polymer microcavity was heated using a low-cost chip resistor with a controllable dc driving power to achieve a desired polymer’s steady-state temperature (T) that exceeds the T of the surrounding environment. The polymer is highly sensitive to variations of T with high repeatability. When the hot polymer was cooled by the measured flowing air, the wavelength fringes of its optical spectra shifted. The HPFFPI anemometers have been experimentally evaluated for different cavity lengths and heating power values. Experimental results demonstrate that the proposed HPFFPI responses well in terms of airflow measurement. A high sensitivity of 1.139 nm/(m/s) and a good resolution of 0.0088 m/s over the 0~2.54 m/s range of airflow were achieved with a cavity length of 10 μm and a heating power of 0.402 W. PMID:28869510

The spectrum of wind speed fluctuations encountered by a rotating blade of a wind energy conversion system

NASA Astrophysics Data System (ADS)

Connell, J. R.

1982-01-01

The results of anemometer, hot-wire anemometer, and laser anemometer array and crosswind sampling of wind speed and turbulence in an area swept by intermediate-to-large wind turbine blades are presented, with comparisons made with a theoretical model for the wind fluctuations. A rotating frame of reference was simulated by timing the anemometric readings at different points of the actuator disk area to coincide with the moment a turbine blade would pass through the point. The hot-wire sensors were mounted on an actual rotating boom, while the laser scanned the wind velocity field in a vertical crosswind circle. The midfrequency region of the turbulence spectrum was found to be depleted, with energy shifted to the high end of the spectrum, with an additional peak at the rotation frequency of the rotor. A model is developed, assuming homogeneous, isotropic turbulence, to reproduce the observed spectra and verify and extend scaling relations using turbine and atmospheric length and time scales. The model is regarded as useful for selecting wind turbine hub heights and rotor rotation rates.

Stratified Turbulence Measurements in Complex Terrain Using Hot-film Probes and a Collocated Sonic Anemometer

NASA Astrophysics Data System (ADS)

Hocut, C.; Kit, E.; Liberzon, D.; Fernando, H. J. S.; Materhorn Team

2014-11-01

In the fall of 2012 and spring 2013, the Mountain Terrain Atmospheric Modeling and Observations Program (MATERHORN) conducted extensive field experiments at the Granite Mountain Atmospheric Science Testbed (GMAST), US Army Dugway Proving Grounds (DPG), Utah. This provided a unique opportunity to deploy tower mounted three-dimensional hot-film combo probes, consisting of sonic anemometers collocated with hot-film anemometers able to respond to the wind direction. The combo probes follow mean winds using a feedback control loop and use a Neural Network to calibrate the hot-films in-situ. Once calibrated, these probes can handle a vast range of background flow conditions and scales from mesoscale flow down to the Kolmogorov scale. Of particular interest are the observed variation in velocity spectra during the evenings. Sometimes the velocity spectra shows the turbulence is Kolmogorov and is isotropic at small scales while in other spectra there is evidence of turbulence production at finer scales. An explanation on different spectral shapes will be presented as well as the relevant length/time scales of the production events. Funded by ONR Grant N00014-11-1-0709.

Laser anemometer using a Fabry-Perot interferometer for measuring mean velocity and turbulence intensity along the optical axis in turbomachinery

NASA Technical Reports Server (NTRS)

Seasholtz, R. G.; Goldman, L. J.

1982-01-01

A technique for measuring a small optical axis velocity component in a flow with a large transverse velocity component is presented. Experimental results are given for a subsonic free jet operating in a laboratory environment, and for a 0.508 meter diameter turbine stator cascade. Satisfactory operation of the instrument was demonstrated in the stator cascade facility with an ambient acoustic noise level during operation of about 105 dB. In addition, the turbulence intensity measured with the interferometer was consistent with previous measurements taken with a fringe type laser anemometer.

Thermal transient anemometer

DOEpatents

Bailey, J.L.; Vresk, J.

1989-07-18

A thermal transient anemometer is disclosed having a thermocouple probe which is utilized to measure the change in temperature over a period of time to provide a measure of fluid flow velocity. The thermocouple probe is located in the fluid flow path and pulsed to heat or cool the probe. The cooling of the heated probe or the heating of the cooled probe from the fluid flow over a period of time is measured to determine the fluid flow velocity. The probe is desired to be locally heated near the tip to increase the efficiency of devices incorporating the probe. 12 figs.

Method for fabricating a microscale anemometer

NASA Technical Reports Server (NTRS)

Liu, Chang (Inventor); Chen, Jack (Inventor)

2008-01-01

Method for fabricating a microscale anemometer on a substrate. A sacrificial layer is formed on the substrate, and a metal thin film is patterned to form a sensing element. At least one support for the sensing element is patterned. The sacrificial layer is removed, and the sensing element is lifted away from the substrate by raising the supports, thus creating a clearance between the sensing element and the substrate to allow fluid flow between the sensing element and the substrate. The supports are raised preferably by use of a magnetic field applied to magnetic material patterned on the supports.

Corona anemometry for qualitative measurement of reversing surface flow with application to separation control by external excitation

NASA Technical Reports Server (NTRS)

Durbin, P. A.; Mckinzie, D. J.

1987-01-01

An corona anemometer which detects gas flow by the displacement of an ion beam is described, and experiments are performed using the anemometer to investigate the active control of diffusor separation by periodic forcing. The apparatus is applied to the separated flow over a rearward facing ramp. An oscillating vane is attached to the surface near the separation point. It is suggested that the enhancement in turbulent energy produced by the oscillating vane is due to drastic modification of the wake shear flow, and not to vane-produced turbulence.

Comparison between 1-minute and 15-minute averages of turbulence parameters

NASA Technical Reports Server (NTRS)

Noble, John M.

1993-01-01

Sonic anemometers are good instruments for measuring temperature and wind speed and are fast enough to calculate the temperature and wind structure parameters used to calculate the variance in the acoustic index of refraction. However, the turbulence parameters are typically 15-minute averaged point measurements. There are several problems associated with making point measurements and using them to represent a turbulence field. Some of the sonic anemometer data analyzed from the Joint Acoustic Propagation Experiment (JAPE) conducted during July 1991 at DIRT Site located at White Sands Missile Range, New Mexico, are examined.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koracin, D.; Kaplan, M.; Smith, C.

The main objectives of this project were to conduct a tall-tower and sodar field campaign in complex terrain, investigate wind properties relevant to wind energy assessment, and evaluate high-resolution models with fixed and adaptive grid structures. Two 60-m towers at Virginia Peak ridges near Washoe Valley, Nevada, were instrumented with cup and vane anemometers as well as sonic anemometers, and an acoustic sounder (hereafter sodar) was installed near one of the towers. The towers were located 2,700 m apart with a vertical distance of 140 m elevation between their bases. Each tower had a downhill exposure of rolling complex terrain,more » with the nearby valley floor 3,200 m to the west and 800 m below the summit. Cup anemometers were installed at both towers at 20, 40, and 60 m, wind vanes at 20 and 60 m, and sonic anemometers at 20 and 60 m. The sodar measurements were nominally provided every 10 m in vertical distance from 40 to 200 m with the quality of the data generally decreasing with height. Surface air temperature, atmospheric pressure, and radiation measurements were conducted at 1.5 m AGL at both of the towers. Although the plan was to conduct a 1-year period of data collection, we extended the period (October 5, 2012 through February 24, 2014) to cover for possible data loss from instrument or communication problems. We also present a preliminary analysis of the towers and sodar data, including a detailed inventory of available and missing data as well as outliers. The analysis additionally includes calculation of the Weibull parameters, turbulence intensity, and initial computation of wind power density at various heights.« less

Height extrapolation of wind data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mikhail, A.S.

1982-11-01

Hourly average data for a period of 1 year from three tall meteorological towers - the Erie tower in Colorado, the Goodnoe Hills tower in Washington and the WKY-TV tower in Oklahoma - were used to analyze the wind shear exponent variabiilty with various parameters such as thermal stability, anemometer level wind speed, projection height and surface roughness. Different proposed models for prediction of height variability of short-term average wind speeds were discussed. Other models that predict the height dependence of Weilbull distribution parameters were tested. The observed power law exponent for all three towers showed strong dependence on themore » anemometer level wind speed and stability (nighttime and daytime). It also exhibited a high degree of dependence on extrapolation height with respect to anemometer height. These dependences became less severe as the anemometer level wind speeds were increased due to the turbulent mixing of the atmospheric boundary layer. The three models used for Weibull distribution parameter extrapolation were he velocity-dependent power law model (Justus), the velocity, surface roughness, and height-dependent model (Mikhail) and the velocity and surface roughness-dependent model (NASA). The models projected the scale parameter C fairly accurately for the Goodnoe Hills and WKY-TV towers and were less accurate for the Erie tower. However, all models overestimated the C value. The maximum error for the Mikhail model was less than 2% for Goodnoe Hills, 6% for WKY-TV and 28% for Erie. The error associated with the prediction of the shape factor (K) was similar for the NASA, Mikhail and Justus models. It ranged from 20 to 25%. The effect of the misestimation of hub-height distribution parameters (C and K) on average power output is briefly discussed.« less

Flow field measurements around a Mars lander model using hot film anemometers under simulated Mars surface conditions

NASA Technical Reports Server (NTRS)

Greene, G. C.; Keafer, L. S., Jr.; Marple, C. G.; Foughner, J. T., Jr.

1972-01-01

Results are presented from a wind-tunnel investigation of the flow field around a 0.45-scale model of a Mars lander. The tests were conducted in air at values of Reynolds number equivalent to those anticipated on Mars. The effects of Reynolds number equivalent to those anticipated on Mars. The effects of Reynolds number, model orientation with respect to the airstream, and the position of a dish-type antenna on the flow field were determined. An appendix is included which describes the calibration and operational characteristics of hot-film anemometers under simulated Mars surface conditions.

Techniques used in the F-14 variable-sweep transition flight experiment

NASA Technical Reports Server (NTRS)

Anderson, Bianca Trujillo; Meyer, Robert R., Jr.; Chiles, Harry R.

1988-01-01

This paper discusses and evaluates the test measurement techniques used to determine the laminar-to-turbulent boundary layer transition location in the F-14 variable-sweep transition flight experiment (VSTFE). The main objective of the VSTFE was to determine the effects of wing sweep on the laminar-to-turbulent transition location at conditions representative of transport aircraft. Four methods were used to determine the transition location: (1) a hot-film anemometer system; (2) two boundary-layer rakes; (3) surface pitot tubes; and (4) liquid crystals for flow visualization. Of the four methods, the hot-film anemometer system was the most reliable indicator of transition.

Measurements of Wind Velocity and Direction Using Acoustic Reflection against Wall

NASA Astrophysics Data System (ADS)

Saito, Ikumi; Wakatsuki, Naoto; Mizutani, Koichi; Ishii, Masahisa; Okushima, Limi; Sase, Sadanori

2008-05-01

The measurements of wind velocity and direction using an acoustic reflection against a wall are described. We aim to measure the spatial mean wind velocity and direction to be used for an air-conditioning system. The proposed anemometer consists of a single wall and two pairs of loudspeakers (SP) and microphones (MIC) that form a triangular shape. Two sound paths of direct and reflected waves are available. One is that of the direct wave and the other is that of the wave reflected on the wall. The times of flights (TOFs) of the direct and reflected waves can be measured using a single MIC because there is a difference in the TOF between direct and reflected waves. By using these TOFs, wind velocity and direction can be calculated. In the experiments, the wind velocities and directions were measured in a wind tunnel by changing the wind velocity. The wind direction was examined by changing the setup of the transducers. The measured values using the proposed and conventional anemometers agreed with each other. By using the wave reflected against a wall, wind velocities and directions can be measured using only two pairs of transducers, while four pairs are required in the case of conventional anemometers.

Laser transit anemometer measurements on a slender cone in the Langley unitary plan wind tunnel

NASA Technical Reports Server (NTRS)

Humphreys, William M., Jr.; Hunter, William W., Jr.; Covell, Peter F.; Nichols, Cecil E., Jr.

1990-01-01

A laser transit anemometer (LTA) system was used to probe the boundary layer on a slender (5 degree half angle) cone model in the Langley unitary plan wind tunnel. The anemometer system utilized a pair of laser beams with a diameter of 40 micrometers spaced 1230 micrometers apart to measure the transit times of ensembles of seeding particles using a cross-correlation technique. From these measurements, boundary layer profiles around the model were constructed and compared with CFD calculations. The measured boundary layer profiles representing the boundary layer velocity normalized to the edge velocity as a function of height above the model surface were collected with the model at zero angle of attack for four different flow conditions, and were collected in a vertical plane that bisected the model's longitudinal center line at a location 635 mm from the tip of the forebody cone. The results indicate an excellent ability of the LTA system to make velocity measurements deep into the boundary layer. However, because of disturbances in the flow field caused by onboard seeding, premature transition occurred implying that upstream seeding is mandatory if model flow field integrity is to be maintained. A description and results of the flow field surveys are presented.

An investigation of the open-loop amplification of a Reynolds number dependent process by wave distortion

NASA Technical Reports Server (NTRS)

Ventrice, M. B.; Purdy, K. R.

1974-01-01

The response of a constant-temperature hot-wire anemometer to sinusoidal and distorted sinusoidal acoustic oscillations is examined. The output of the anemometer is dependent upon the Reynolds number of the flow over the wire. The response is a measure of the interaction between the anemometer output and the acoustic pressure in the neighborhood of the wire. It is an open-loop prediction of the characteristics of actual closed-loop operation of a system. If the open-loop response is large enough, unstable closed-loop operation is predicted. The study was motivated by a need to investigate the stability limits of liquid-propellant rockets when perturbed by pressure oscillations. The sinusoidal and distorted sinusoidal acoustic oscillations used for this study are the same as those characteristic of unstable rocket combustion. Qualitatively, the results are similar--the response of the system to pure sinusoidal acoustic vibration of the fluid surrounding the wire is small, even when the magnitude of the acoustic pressure is quite large; but the response can be increased by as much as an order of magnitude with respect to the sinusoidal case by the addition of distortion. The amplitude and phase of the distortion component, relative to the fundamental component, are the dominant factors in the increase in the response.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bonin, Timothy A.; Newman, Jennifer F.; Klein, Petra M.

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. However, 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 skillmore » in correcting for volume-averaging effects in the calculation of w' 2 is also assessed. Additionally, this autocovariance technique is further refined by defining the amount of lag time to use for the most accurate estimates of w' 2. 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.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bonin, Timothy A.; Newman, Jennifer F.; Klein, Petra M.

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 skillmore » 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.« less

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

DOE PAGES

Bonin, Timothy A.; Newman, Jennifer F.; Klein, Petra M.; ...

2016-12-06

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 skillmore » 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.« less

Impact of different eddy covariance sensors and set-up on the annual balance of CO2 and fluxes of CH4 and latent heat in the Arctic

NASA Astrophysics Data System (ADS)

Goodrich, J. P.; Zona, D.; Gioli, B.; Murphy, P.; Burba, G. G.; Oechel, W. C.

2015-12-01

Expanding eddy covariance measurements of CO2 and CH4 fluxes in the Arctic is critical for refining the global C budget. Continuous measurements are particularly challenging because of the remote locations, low power availability, and extreme weather conditions. The necessity for tailoring instrumentation at different sites further complicates the interpretation of results and may add uncertainty to estimates of annual CO2 budgets. We investigated the influence of different sensor combinations on FCO2, latent heat (LE), and FCH4, and assessed the differences in annual FCO2 estimated with different instrumentation at the same sites. Using data from four sites across the North Slope of Alaska, we resolved FCO2 and FCH4 to within 5% using different combinations of open- and closed-path gas analyzers and within 10% using heated and non-heated anemometers. A continuously heated anemometer increased data coverage relative to non-heated anemometers while resulting in comparable annual FCO2, despite over-estimating sensible heat fluxes by 15%. We also implemented an intermittent heating strategy whereby activation only when ice or snow blockage of the transducers was detected. This resulted in comparable data coverage (~ 60%) to the continuously heated anemometer, while avoiding potential over-estimation of sensible heat and gas fluxes. We found good agreement in FCO2 and FCH4 from two closed-path and one open-path gas analyzer, despite the need for large spectral corrections of closed-path fluxes and density and temperature corrections to open-path sensors. However, data coverage was generally greater when using closed-path, especially during cold seasons (36-40% vs 10-14% for the open path), when fluxes from Arctic regions are particularly uncertain and potentially critical to annual C budgets. Measurement of Arctic LE remains a challenge due to strong attenuation along sample tubes, even when heated, that could not be accounted for with spectral corrections.

Basic principles and recent observations of rotationally sampled wind

NASA Technical Reports Server (NTRS)

Connell, James R.

1995-01-01

The concept of rotationally sampled wind speed is described. The unusual wind characteristics that result from rotationally sampling the wind are shown first for early measurements made using an 8-point ring of anemometers on a vertical plane array of meteorological towers. Quantitative characterization of the rotationally sampled wind is made in terms of the power spectral density function of the wind speed. Verification of the importance of the new concept is demonstrated with spectral analyses of the response of the MOD-OA blade flapwise root bending moment and the corresponding rotational analysis of the wind measured immediately upwind of the MOD-OA using a 12-point ring of anemometers on a 7-tower vertical plane array. The Pacific Northwest Laboratory (PNL) theory of the rotationally sampled wind speed power spectral density function is tested successfully against the wind spectrum measured at the MOD-OA vertical plane array. A single-tower empirical model of the rotationally sampled wind speed is also successfully tested against the measurements from the full vertical plane array. Rotational measurements of the wind velocity with hotfilm anemometers attached to rotating blades are shown to be accurate and practical for research on winds at the blades of wind turbines. Some measurements at the rotor blade of a MOD-2 turbine using the hotfilm technique in a pilot research program are shown. They are compared and contrasted to the expectations based upon application of the PNL theory of rotationally sampled wind to the MOD-2 size and rotation rate but without teeter, blade bending, or rotor induction accounted for. Finally, the importance of temperature layering and of wind modifications due to flow over complex terrain is demonstrated by the use of hotfilm anemometer data, and meteorological tower and acoustic doppler sounder data from the MOD-2 site at Goodnoe Hills, Washington.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Newman, Jennifer F.; Clifton, Andrew

Currently, cup anemometers on meteorological towers are used to measure wind speeds and turbulence intensity to make decisions about wind turbine class and site suitability; however, as modern turbine hub heights increase and wind energy expands to complex and remote sites, it becomes more difficult and costly to install meteorological towers at potential sites. As a result, remote-sensing devices (e.g., lidars) are now commonly used by wind farm managers and researchers to estimate the flow field at heights spanned by a turbine. Although lidars can accurately estimate mean wind speeds and wind directions, there is still a large amount ofmore » uncertainty surrounding the measurement of turbulence using these devices. Errors in lidar turbulence estimates are caused by a variety of factors, including instrument noise, volume averaging, and variance contamination, in which the magnitude of these factors is highly dependent on measurement height and atmospheric stability. As turbulence has a large impact on wind power production, errors in turbulence measurements will translate into errors in wind power prediction. The impact of using lidars rather than cup anemometers for wind power prediction must be understood if lidars are to be considered a viable alternative to cup anemometers.In this poster, the sensitivity of power prediction error to typical lidar turbulence measurement errors is assessed. Turbulence estimates from a vertically profiling WINDCUBE v2 lidar are compared to high-resolution sonic anemometer measurements at field sites in Oklahoma and Colorado to determine the degree of lidar turbulence error that can be expected under different atmospheric conditions. These errors are then incorporated into a power prediction model to estimate the sensitivity of power prediction error to turbulence measurement error. Power prediction models, including the standard binning method and a random forest method, were developed using data from the aeroelastic simulator FAST for a 1.5 MW turbine. The impact of lidar turbulence error on the predicted power from these different models is examined to determine the degree of turbulence measurement accuracy needed for accurate power prediction.« less

FIRE_AX_SOF_SUR_MET

Atmospheric Science Data Center

2015-11-25

... Buoy Instrument:  Barometer Sonic Anemometer Thermistor Spatial Coverage:  (34.60, ... Earthdata Search Parameters:  Dry Bulb Temperature Pressure Sea Surface Temperature Wet Bulb Temperature ...

Evaluation of scintillometery measurements of fluxes of momentum and sensible heat in the roughness sublayer

NASA Astrophysics Data System (ADS)

Sugawara, Hirofumi; Inagaki, Atsushi; Roth, Matthias; Kanda, Manabu

2016-11-01

Scintillometer measurements of turbulent fluxes of momentum and sensible heat in the roughness sublayer over a regular array of cubes in an outdoor environment were tested with direct measurement from sonic anemometers. The dissipation rate, ɛ, and temperature structure parameter, C T 2 , obtained from the scintillometer agreed well with those from four sonic anemometers located along the scintillometer path. The fluxes measured by the scintillometer also corresponded well to those from the line-averaged eddy covariance approach, although this agreement was greatly influenced by the choice of the zero-plane displacement length and the form of the similarity function used in the scintillometer software. A guide for choosing the appropriate similarity function for the urban roughness sublayer is proposed.

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

NASA Astrophysics Data System (ADS)

Bonin, Timothy A.; Newman, Jennifer F.; Klein, Petra M.; Chilson, Phillip B.; Wharton, Sonia

2016-12-01

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. However, 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. Additionally, this autocovariance technique is further refined by defining the amount of lag time to use for the most accurate estimates of w'2. 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 (R2 ≈ 0.95 - 0.98) with those calculated from sonic anemometer measurements.

Wind observations above an urban river using a new lidar technique, scintillometry and anemometry.

PubMed

Wood, C R; Pauscher, L; Ward, H C; Kotthaus, S; Barlow, J F; Gouvea, M; Lane, S E; Grimmond, C S B

2013-01-01

Airflow along rivers might provide a key mechanism for ventilation in cities: important for air quality and thermal comfort. Airflow varies in space and time in the vicinity of rivers. Consequently, there is limited utility in point measurements. Ground-based remote sensing offers the opportunity to study 3D airflow in locations which are difficult to observe with conventional approaches. For three months in the winter and spring of 2011, the airflow above the River Thames in central London was observed using a scanning Doppler lidar, a scintillometer and sonic anemometers. First, an inter-comparison showed that lidar-derived mean wind-speed estimates compare almost as well to sonic anemometers (root-mean-square error (rmse) 0.65-0.68 ms(-1)) as comparisons between sonic anemometers (0.35-0.73 ms(-1)). Second, the lidar duo-beam operating strategy provided horizontal transects of wind vectors (comparison with scintillometer rmse 1.12-1.63 ms(-1)) which revealed mean and turbulent airflow across the river and surrounds; in particular, channelled airflow along the river and changes in turbulence quantities consistent with the roughness changes between built and river environments. The results have important consequences for air quality and dispersion around urban rivers, especially given that many cities have high traffic rates on roads located on riverbanks. Copyright © 2012 Elsevier B.V. All rights reserved.

Comparing Multiple Evapotranspiration-calculating Methods, Including Eddy Covariance and Surface Renewal, Using Empirical Measurements from Alfalfa Fields in the Sacramento-San Joaquin River Delta

NASA Astrophysics Data System (ADS)

Clay, J.; Kent, E. R.; Leinfelder-Miles, M.; Lambert, J. J.; Little, C.; Paw U, K. T.; Snyder, R. L.

2016-12-01

Eddy covariance and surface renewal measurements were used to estimate evapotranspiration (ET) over a variety of crop fields in the Sacramento-San Joaquin River Delta during the 2016 growing season. However, comparing and evaluating multiple measurement systems and methods for determining ET was focused upon at a single alfalfa site. The eddy covariance systems included two systems for direct measurement of latent heat flux: one using a separate sonic anemometer and an open path infrared gas analyzer and another using a combined system (Campbell Scientific IRGASON). For these methods, eddy covariance was used with measurements from the Campbell Scientific CSAT3, the LI-COR 7500a, the Campbell Scientific IRGASON, and an additional R.M. Young sonic anemometer. In addition to those direct measures, the surface renewal approach included several energy balance residual methods in which net radiation, ground heat flux, and sensible heat flux (H) were measured. H was measured using several systems and different methods, including using multiple fast-response thermocouple measurements and using the temperatures measured by the sonic anemometers. The energy available for ET was then calculated as the residual of the surface energy balance equation. Differences in ET values were analyzed between the eddy covariance and surface renewal methods, using the IRGASON-derived values of ET as the standard for accuracy.

NARSTO EPA SS BALTIMORE JHU MET DATA

Atmospheric Science Data Center

2018-04-09

... Meteorological Station Instrument:  Temperature Probe Humidity Probe Cup Anemometer Rain Gauge Sonic ...   E arthdata Search Parameters:  Air Temperature Humidity Surface Winds Precipitation Amount Heat Flux ...

Laser anemometer measurements in a transonic axial-flow fan rotor

NASA Technical Reports Server (NTRS)

Strazisar, Anthony J.; Wood, Jerry R.; Hathaway, Michael D.; Suder, Kenneth L.

1989-01-01

Laser anemometer surveys were made of the 3-D flow field in NASA rotor 67, a low aspect ratio transonic axial-flow fan rotor. The test rotor has a tip relative Mach number of 1.38. The flowfield was surveyed at design speed at near peak efficiency and near stall operating conditions. Data is presented in the form of relative Mach number and relative flow angle distributions on surfaces of revolution at nine spanwise locations evenly spaced from hub to tip. At each spanwise location, data was acquired upstream, within, and downstream of the rotor. Aerodynamic performance measurements and detailed rotor blade and annulus geometry are also presented so that the experimental results can be used as a test case for 3-D turbomachinery flow analysis codes.

Metallic hot wire anemometer. [for high speed wind tunnel tests

NASA Technical Reports Server (NTRS)

Lemos, F. R. (Inventor)

1977-01-01

A hot wire anemometer is described which has a body formed of heat resistant metal such as an alloy high in nickel content which supports a probe wire disposed in a V groove in the body. The V groove contains a high temperature ceramic adhesive that partially encompasses the downstream side of the probe wire. Mechanical and electrical connection to the probe wire is achieved through conductive support rods that are constructed of the same high temperature metal, insulation between the body and the conductor rods being provided by a coating of an oxide of the same material which coating is formed in situ. The oxide coating insulates the conductor rods from the body, mechanically fixes the conductors within the body, and maintains its integrity at elevated temperatures.

Field intercomparison of six different three-dimensional sonic anemometers

NASA Astrophysics Data System (ADS)

Mauder, Matthias; Zeeman, Matthias

2017-04-01

Although sonic anemometers have been used extensively for several decades in micrometeorological and ecological research, there is still some scientific debate about the measurement uncertainty of these instruments. This is due to the fact that an absolute reference for the measurement of turbulent wind fluctuations in the free atmosphere does not exist. In view of this lack we have conducted a field intercomparison experiment of six commonly used sonic anemometers from four major manufacturers. The models included Campbell CSAT3, Gill HS-50 and R3, METEK uSonic-3 Omni, R.M. Young 81000 and 81000RE. The experiment was conducted over a meadow at the TERENO/ICOS site De-Fen in southern Germany over a period of 16 days in June of 2016 in preparation of the ScaleX campaign. The measurement height was 3 m for all sensors, which were separated by 9 m from each other, each on its own tripod, in order to limit contamination of the turbulence measurements by neighbouring structures as much as possible. Moreover, the data were filtered for potentially disturbed wind sectors, and the high-frequency data from all instruments were treated with the same post-processing algorithm. In this presentation, we compare the results for various turbulence statistics from all sensors. These include mean horizontal wind speed, standard deviations of vertical wind velocity and sonic temperature, friction velocity and the covariance between vertical wind velocity and sonic temperature. Quantitative measures of uncertainty were derived from these results. We find that biases and regression intercepts are generally very small for all sensors and all computed variables, except for the temperature measurements of the two Gill sonic anemometers (HS and R3), which are known to suffer from a transducer-temperature dependence of the sonic temperature measurement. The comparability of the instruments is not always as good, which means that there is some scatter but the errors compensate at least partly. The best overall agreement between the different instruments was found for the variables "mean wind speed" and "buoyancy flux", which reflects that the sensors are optimized for measuring these quantities.

Anemometer calibrator

NASA Technical Reports Server (NTRS)

Bate, T.; Calkins, D. E.; Price, P.; Veikins, O.

1971-01-01

Calibrator generates accurate flow velocities over wide range of gas pressure, temperature, and composition. Both pressure and flow velocity can be maintained within 0.25 percent. Instrument is essentially closed loop hydraulic system containing positive displacement drive.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strons, Philip; Bailey, James L.

Anemometer readings alone cannot provide a complete picture of air flow patterns at an open gloveport. Having a means to visualize air flow for field tests in general provides greater insight by indicating direction in addition to the magnitude of the air flow velocities in the region of interest. Furthermore, flow visualization is essential for Computational Fluid Dynamics (CFD) verification, where important modeling assumptions play a significant role in analyzing the chaotic nature of low-velocity air flow. A good example is shown Figure 1, where an unexpected vortex pattern occurred during a field test that could not have been measuredmore » relying only on anemometer readings. Here by, observing and measuring the patterns of the smoke flowing into the gloveport allowed the CFD model to be appropriately updated to match the actual flow velocities in both magnitude and direction.« less

Laser Doppler semiconductor anemometry of vortex flow behind the vane wheel rotor of the water turbine

NASA Astrophysics Data System (ADS)

Meledin, V.; Anikin, Yu.; Bakakin, G.; Glavniy, V.; Dvoinishnikov, S.; Kulikov, D.; Naumov, I.; Okulov, V.; Pavlov, V.; Rakhmanov, V.; Sadbakov, O.; Mostovskiy, N.; Ilyin, S.

2006-05-01

For hydrodynamic examinations of the turbid three-phase streams with air bubbles and with a depth more than 500 mm for the first time it is developed 2D Laser Doppler Semiconductor Anemometer LADO5-LMZ. Anemometer signal processor base on <> and new procedure of adaptive selection of Doppler frequency. Complex testing of method and measuring tools have been done. Outcomes of full-scale experiments on diagnostic of nonstationary flow behind the vane wheel rotor in draught tube of the Frensis water turbine are presented from optimum regimes of activity to forced. Water discharge which has been calculated from water turbine universal performance model and calculated by measuring axial velocity profiles was compared. It is shown that the maximum aggregate error of definition of the consumption does not exceed 5%.

Field Intercomparison of Six Sifferent Three-dimensional Sonic Anemometers

NASA Astrophysics Data System (ADS)

Zeeman, M. J.; Mauder, M.

2016-12-01

Although sonic anemometers have been used extensively for several decades in micrometeorological and ecological research, there is still some scientific debate about the measurement uncertainty of these instruments. This is due to the fact that an absolute reference for the measurement of turbulent wind fluctuations in the free atmosphere does not exist. In view of this lack we have conducted a field intercomparison experiment of six commonly used sonic anemometers from four major manufacturers. The models included Campbell CSAT3, Gill HS-50 and R3, METEK uSonic-3 Omni, R.M. Young 81000 and 81000RE. The experiment was conducted over a meadow at the TERENO/ICOS site De-Fen in southern Germany over a period of 16 days in June of 2016 in preparation of the ScaleX campaign. The measurement height was 3 m for all sensors, which were separated by 9 m from each other, each on its own tripod, in order to limit contamination of the turbulence measurements by neighbouring structures as much as possible. Moreover, the data were filtered for potentially disturbed wind sectors, and the high-frequency data from all instruments were treated with the same post-processing algorithm. In this presentation, we compare the results for various turbulence statistics from all sensors. These include mean horizontal wind speed, standard deviations of vertical wind velocity and sonic temperature, friction velocity and the covariance between vertical wind velocity and sonic temperature. Quantitative measures of uncertainty, such as bias and comparability are derived from these results.

Wind Gust Measurement Techniques-From Traditional Anemometry to New Possibilities.

PubMed

Suomi, Irene; Vihma, Timo

2018-04-23

Information on wind gusts is needed for assessment of wind-induced damage and risks to safety. The measurement of wind gust speed requires a high temporal resolution of the anemometer system, because the gust is defined as a short-duration (seconds) maximum of the fluctuating wind speed. Until the digitalization of wind measurements in the 1990s, the wind gust measurements suffered from limited recording and data processing resources. Therefore, the majority of continuous wind gust records date back at most only by 30 years. Although the response characteristics of anemometer systems are good enough today, the traditional measurement techniques at weather stations based on cup and sonic anemometers are limited to heights and regions where the supporting structures can reach. Therefore, existing measurements are mainly concentrated over densely-populated land areas, whereas from remote locations, such as the marine Arctic, wind gust information is available only from sparse coastal locations. Recent developments of wind gust measurement techniques based on turbulence measurements from research aircraft and from Doppler lidar can potentially provide new information from heights and locations unreachable by traditional measurement techniques. Moreover, fast-developing measurement methods based on Unmanned Aircraft Systems (UASs) may add to better coverage of wind gust measurements in the future. In this paper, we provide an overview of the history and the current status of anemometry from the perspective of wind gusts. Furthermore, a discussion on the potential future directions of wind gust measurement techniques is provided.

Assessment of Planetary-Boundary-Layer Schemes in the Weather Research and Forecasting Model Within and Above an Urban Canopy Layer

NASA Astrophysics Data System (ADS)

Ferrero, Enrico; Alessandrini, Stefano; Vandenberghe, Francois

2018-03-01

We tested several planetary-boundary-layer (PBL) schemes available in the Weather Research and Forecasting (WRF) model against measured wind speed and direction, temperature and turbulent kinetic energy (TKE) at three levels (5, 9, 25 m). The Urban Turbulence Project dataset, gathered from the outskirts of Turin, Italy and used for the comparison, provides measurements made by sonic anemometers for more than 1 year. In contrast to other similar studies, which have mainly focused on short-time periods, we considered 2 months of measurements (January and July) representing both the seasonal and the daily variabilities. To understand how the WRF-model PBL schemes perform in an urban environment, often characterized by low wind-speed conditions, we first compared six PBL schemes against observations taken by the highest anemometer located in the inertial sub-layer. The availability of the TKE measurements allows us to directly evaluate the performances of the model; results of the model evaluation are presented in terms of quantile versus quantile plots and statistical indices. Secondly, we considered WRF-model PBL schemes that can be coupled to the urban-surface exchange parametrizations and compared the simulation results with measurements from the two lower anemometers located inside the canopy layer. We find that the PBL schemes accounting for TKE are more accurate and the model representation of the roughness sub-layer improves when the urban model is coupled to each PBL scheme.

Wind Gust Measurement Techniques—From Traditional Anemometry to New Possibilities

PubMed Central

2018-01-01

Information on wind gusts is needed for assessment of wind-induced damage and risks to safety. The measurement of wind gust speed requires a high temporal resolution of the anemometer system, because the gust is defined as a short-duration (seconds) maximum of the fluctuating wind speed. Until the digitalization of wind measurements in the 1990s, the wind gust measurements suffered from limited recording and data processing resources. Therefore, the majority of continuous wind gust records date back at most only by 30 years. Although the response characteristics of anemometer systems are good enough today, the traditional measurement techniques at weather stations based on cup and sonic anemometers are limited to heights and regions where the supporting structures can reach. Therefore, existing measurements are mainly concentrated over densely-populated land areas, whereas from remote locations, such as the marine Arctic, wind gust information is available only from sparse coastal locations. Recent developments of wind gust measurement techniques based on turbulence measurements from research aircraft and from Doppler lidar can potentially provide new information from heights and locations unreachable by traditional measurement techniques. Moreover, fast-developing measurement methods based on Unmanned Aircraft Systems (UASs) may add to better coverage of wind gust measurements in the future. In this paper, we provide an overview of the history and the current status of anemometry from the perspective of wind gusts. Furthermore, a discussion on the potential future directions of wind gust measurement techniques is provided. PMID:29690647

Intermittent turbulence events observed with a sonic anemometer and minisodar during CASES99.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coulter, R. L.; Doran, J. C.

The Cooperative Air Surface Exchange Study 1999 (CASES99), designed to investigate in detail the nocturnal boundary layer (NBL) of the atmosphere with particular emphasis on turbulence and turbulence events, took place during October 1999, within the Atmospheric Boundary Layer Experiments (ABLE) region east of Wichita KS. The principal measurement site was a heavily instrumented 2-km square located near Leon (LE), KS, but additional sites at Smileyberg (SM) and Beaumont (BE) were also used. The authors augmented the normal ABLE measurements at Beaumont (radar wind profiler, minisodar, 10-m meteorological tower, precipitation gauge) with a sonic anemometer mounted on the tower, 7more » m above the surface. For this campaign, the minisodar data were saved in single-pulse mode with no averaging. The Beaumont site is within gently rolling rangeland used primarily for grazing. The site is on a flat plain rising gradually to the east.The Flint Hills escarpment, located approximately 2 km to the east, marks the highest point in, and the eastern boundary of, the Walnut River watershed. Although most terrain features are subtle, terrain effects on atmospheric flows are still possible, particularly in stable conditions. The intent was to observe turbulence and, hopefully, turbulence events with the sonic anemometer and minisodar. The horizontal extent of these occurrences can be studied by including the Beaumont data with those obtained at the Leon site. In this report the authors are concerned with the occurrence of intermittent turbulence.« less

The 2d-LCA as an alternative to x-wires

NASA Astrophysics Data System (ADS)

Puczylowski, Jaroslaw; Hölling, Michael; Peinke, Joachim

2015-11-01

The 2d-Laser Cantilever Anemometer (2d-LCA) is an innovative sensor for two-dimensional velocity measurements in fluids. It uses a micostructured cantilever made of silicon and SU-8 as a sensing element and is capable of performing mesurements with extremly high temporal resolutions up to 150kHz. The size of the cantilever defines its spatial resolution, which is in the order of 150 μm only. Another big feature is a large angular range of 180° in total. The 2d-LCA has been developed as an alternative measurement method to x-wires with the motivation to create a sensor that can operate in areas where the use of hot-wire anemometry is difficult. These areas include measurements in liquids and in near-wall or particle-laden flows. Unlike hot-wires, the resolution power of the 2d-LCA does not decrease with increasing flow velocity, making it particularly suitable for measurements in high speed flows. Comparative measurements with the 2d-LCA and hot-wires have been carried out in order to assess the performance of the new anemometer. The data of both measurement techniques were analyzed using the same stochastic methods including a spectral analysis as well as an inspection of increment statistics and structure functions. Furthermore, key parameters, such as mean values of both velocity components, angles of attack and the characteristic length scales were determined from both data sets. The analysis reveals a great agreement between both anemometers and thus confirms the new approach.

2d-LCA - an alternative to x-wires

NASA Astrophysics Data System (ADS)

Puczylowski, Jaroslaw; Hölling, Michael; Peinke, Joachim

2014-11-01

The 2d-Laser Cantilever Anemometer (2d-LCA) is an innovative sensor for two-dimensional velocity measurements in fluids. It uses a micostructured cantilever made of silicon and SU-8 as a sensing element and is capable of performing mesurements with extremly high temporal resolutions up to 150 kHz. The size of the cantilever defines its spatial resolution, which is in the order of 150 μm only. Another big feature is a large angular range of 180° in total. The 2d-LCA has been developed as an alternative measurement method to x-wires with the motivation to create a sensor that can operate in areas where the use of hot-wire anemometry is difficult. These areas include measurements in liquids and in near-wall or particle-laden flows. Unlike hot-wires, the resolution power of the 2d-LCA does not decrease with increasing flow velocity, making it particularly suitable for measurements in high speed flows. Comparative measurements with the 2d-LCA and hot-wires have been carried out in order to assess the performance of the new anemometer. The data of both measurement techniques were analyzed using the same stochastic methods including a spectral analysis as well as an inspection of increment statistics and structure functions. Furthermore, key parameters, such as mean values of both velocity components, angles of attack and the characteristic length scales were determined from both data sets. The analysis reveals a great agreement between both anemometers and thus confirms the new approach.

Potential accuracy of methods of laser Doppler anemometry in the single-particle scattering mode

NASA Astrophysics Data System (ADS)

Sobolev, V. S.; Kashcheeva, G. A.

2017-05-01

Potential accuracy of methods of laser Doppler anemometry is determined for the singleparticle scattering mode where the only disturbing factor is shot noise generated by the optical signal itself. The problem is solved by means of computer simulations with the maximum likelihood method. The initial parameters of simulations are chosen to be the number of real or virtual interference fringes in the measurement volume of the anemometer, the signal discretization frequency, and some typical values of the signal/shot noise ratio. The parameters to be estimated are the Doppler frequency as the basic parameter carrying information about the process velocity, the signal amplitude containing information about the size and concentration of scattering particles, and the instant when the particles arrive at the center of the measurement volume of the anemometer, which is needed for reconstruction of the examined flow velocity as a function of time. The estimates obtained in this study show that shot noise produces a minor effect (0.004-0.04%) on the frequency determination accuracy in the entire range of chosen values of the initial parameters. For the signal amplitude and the instant when the particles arrive at the center of the measurement volume of the anemometer, the errors induced by shot noise are in the interval of 0.2-3.5%; if the number of interference fringes is sufficiently large (more than 20), the errors do not exceed 0.2% regardless of the shot noise level.

Highway measurements of vehicle-induced turbulence (VIT) and enhanced mixing in the surface layer

NASA Astrophysics Data System (ADS)

Miller, S. J.; Gordon, M.; Staebler, R. M.; Li-Chee-Ming, J.; Taylor, P.

2016-12-01

Motor vehicles generate vehicle-induced turbulence (VIT) while in motion, which affects the mixing and transport of emitted trace gases, heat and momentum. During July, 2016 a 40Hz sonic anemometer (ATI) and a co-located 20Hz open path CO2/H2O gas analyzer (LICOR) were assembled and driven on highways in the Greater Toronto Area. An ultra-high sensitivity aerosol spectrometer was employed to measure the total number concentration of particles between 60 and 1000nm at the position of the gas analyzer and sonic anemometer. A video camera with GPS capabilities was also utilized to assess the surrounding features while chasing a specific vehicle type. The following distance of each chased vehicle is calculated as a function of pixel location, with the back edge of each followed vehicle being identified as the initial contrast between the vehicle's shadow and the roadway. Combining the sonic anemometer data with the GPS data allows turbulence statistics to be developed and correlations with vehicle type and following distance to be examined. Vehicle-induced turbulence is assessed using turbulent kinetic energy (TKE), a measure of turbulent mixing, which maximizes near the followed vehicle and decreases with increasing following distance. Vehicle exhaust plumes are identified using the measured CO2 concentration. The CO2 concentration data in conjunction with TKE and turbulent fluxes are used to explore the potential impacts of vehicle-induced turbulence on atmospheric mixing within the surface layer.

Automatic tracking of wake vortices using ground-wind sensor data

DOT National Transportation Integrated Search

1977-01-03

Algorithms for automatic tracking of wake vortices using ground-wind anemometer : data are developed. Methods of bad-data suppression, track initiation, and : track termination are included. An effective sensor-failure detection-and identification : ...

40 CFR 1065.225 - Intake-air flow meter.

Code of Federal Regulations, 2012 CFR

2012-07-01

... concentrations, if the same signal is used in a chemical-balance calculation to determine work from brake... tube, or a hot-wire anemometer. Note that your overall system for measuring intake-air flow must meet...

Ground Wind Vortex Sensing System Calibration Tests

DOT National Transportation Integrated Search

1980-02-01

This report describes the collection of data related to the calibration of two systems for detecting and tracking aircraft wake vortices. The systems tested were the propeller anemometer Ground Wind Vortex Sensing System and the Pulsed Acoustic Vorte...

Anemometer array and meteorological data : May 1998 SOCRATES test

DOT National Transportation Integrated Search

1999-06-01

In support of the Federal Aviation Administration, the Volpe National Transportation Systems Center (Volpe Center) is conducting an evaluation of a laser based system concept called SOCRATES to determine its possible application in detecting potentia...

Motion of Aircraft Wake Vortices in Ground Effect.

DOT National Transportation Integrated Search

2000-04-01

This report addresses the wake-turbulence separation standards for close-spaced parallel runways. Ground-wind anemometer data collected at Kennedy (landing) and O'Hare (takeoff) airports are analyzed to assess the lateral transport probability for wa...

Estimating mechanical blood trauma in a centrifugal blood pump: laser Doppler anemometer measurements of the mean velocity field.

PubMed

Pinotti, M; Paone, N

1996-06-01

A laser Doppler anemometer (LDA) was used to obtain the mean velocity and the Reynolds stress fields in the inner channels of a well-known centrifugal vaneless pump (Bio-pump). Effects of the excessive flow resistance against which an occlusive pump operates in some surgical situations, such as cardiopulmonary bypass, are illustrated. The velocity vector field obtained from LDA measurements reveals that the constraint-forced vortex provides pumping action in a restricted area in the core of the pump. In such situations, recirculating zones dominate the flow and consequently increase the damage to blood cells and raise the risk of thrombus formation in the device. Reynolds normal and shear stress fields were obtained in the entry flow for the channel formed by two rotating cones to illustrate the effects of flow disturbances on the potential for blood cell damage.

Estimating Mechanical Blood Trauma in a Centrifugal Blood Pump: Laser Doppler Anemometer Measurements of the Mean Velocity Field.

PubMed

Pinotti, Marcos; Paone, Nicola

1996-05-01

A laser Doppler anemometer (LDA) was used to obtain the mean velocity and the Reynolds stress fields in the inner channels of a well-known centrifugal vaneless pump (Bio-pump). Effects of the excessive flow resistance against which an occlusive pump operates in some surgical situations, such as cardiopulmonary bypass, are illustrated. The velocity vector field obtained from LDA measurements reveals that the constraint-forced vortex provides pumping action in a restricted area in the core of the pump. In such situations, recirculating zones dominate the flow and consequently increase the damage to blood cells and raise the risk of thrombus formation in the device. Reynolds normal and shear stress fields were obtained in the entry flow for the channel formed by two rotating cones to illustrate the effects of flow disturbances on the potential for blood cell damage. © 1996 International Society for Artificial Organs.

Development of buried wire gages for measurement of wall shear stress in Blastane experiments

NASA Technical Reports Server (NTRS)

Murthy, S. V.; Steinle, F. W.

1986-01-01

Buried Wire Gages operated from a Constant Temperature Anemometer System are among the special types of instrumentation to be used in the Boundary Layer Apparatus for Subsonic and Transonic flow Affected by Noise Environment (BLASTANE). These Gages are of a new type and need to be adapted for specific applications. Methods were developed to fabricate Gage inserts and mount those in the BLASTANE Instrumentation Plugs. A large number of Gages were prepared and operated from a Constant Temperature Anemometer System to derive some of the calibration constants for application to fluid-flow wall shear-stress measurements. The final stage of the calibration was defined, but could not be accomplished because of non-availability of a suitable flow simulating apparatus. This report provides a description of the Buried Wire Gage technique, an explanation of the method evolved for making proper Gages and the calibration constants, namely Temperature Coefficient of Resistance and Conduction Loss Factor.

Flow visualization methods for field test verification of CFD analysis of an open gloveport

DOE PAGES

Strons, Philip; Bailey, James L.

2017-01-01

Anemometer readings alone cannot provide a complete picture of air flow patterns at an open gloveport. Having a means to visualize air flow for field tests in general provides greater insight by indicating direction in addition to the magnitude of the air flow velocities in the region of interest. Furthermore, flow visualization is essential for Computational Fluid Dynamics (CFD) verification, where important modeling assumptions play a significant role in analyzing the chaotic nature of low-velocity air flow. A good example is shown Figure 1, where an unexpected vortex pattern occurred during a field test that could not have been measuredmore » relying only on anemometer readings. Here by, observing and measuring the patterns of the smoke flowing into the gloveport allowed the CFD model to be appropriately updated to match the actual flow velocities in both magnitude and direction.« less

Updates from the AmeriFlux Management Project Tech Team

NASA Astrophysics Data System (ADS)

Biraud, S.; Chan, S.; Dengel, S.; Polonik, P.; Hanson, C. V.; Billesbach, D. P.; Torn, M. S.

2017-12-01

The goal of AmeriFlux is to develop a network of long-term flux sites for quantifying and understanding the role of the terrestrial biosphere in global climate and environmental change. The AmeriFlux Management Program (AMP) Tech Team at LBNL strengthens the AmeriFlux Network by (1) standardizing operational practices, (2) developing calibration and maintenance routines, and (3) setting clear data quality goals. In this poster we will present results and recent progress in three areas: IRGA intercomparison experiment in cooperation with UC Davis, and main manufacturers of sensors used in the AmeriFlux network (LI-COR, Picarro, and Campbell Scientific). Gill sonic anemometers characterization in collaboration with John Frank and Bill Massman (US Forest Service) following the discovery of a significant firmware problem in commonly used Gill Sonic anemometer, Unmanned aerial systems (UAS), and sensors systematically used at AmeriFlux sites to improve site characterization.

The Effect of Turbulence on the Drag of Flat Plates

NASA Technical Reports Server (NTRS)

Schubauer, G B; Dryden, H L

1937-01-01

in determining the effect of turbulence on the forces exerted on bodies in the air stream of a wind tunnel, it is commonly assumed that the indications of the standard Pitot-static tube used to determine the air speed are not dependent on the turbulence. To investigate the truth of this assumption, the drag of a normally exposed flat plate, the difference in pressure between the front and rear of a thin circular disk, the rate of rotation of a vane anemometer, and the pressure developed by a standard Pitot-static tube were measured in an air stream for several conditions of turbulence. The results may be interpreted as indicating that there is no appreciable effect of turbulence on the vane anemometer and the standard pitot-static tube, but that there is small effect on the drag of a flat plate and the pressure difference between front and rear of a disk.

Fiber-optic anemometer based on single-walled carbon nanotube coated tilted fiber Bragg grating.

PubMed

Zhang, Yang; Wang, Fang; Liu, Zigeng; Duan, Zhihui; Cui, Wenli; Han, Jie; Gu, Yiying; Wu, Zhenlin; Jing, Zhenguo; Sun, Changsen; Peng, Wei

2017-10-02

In this work, a novel and simple optical fiber hot-wire anemometer based on single-walled carbon nanotubes (SWCNTs) coated tilted fiber Bragg grating (TFBG) is proposed and demonstrated. For the hot-wire wind speed sensor design, TFBG is an ideal in-fiber sensing structure due to its unique features. It is utilized as both light coupling and temperature sensing element without using any geometry-modified or uncommon fiber, which simplifies the sensor structure. To further enhance the thermal conversion capability, SWCNTs are coated on the surface of the TFBG instead of traditional metallic materials, which have excellent thermal characteristics. When a laser light is pumped into the sensor, the pump light propagating in the core will be easily coupled into cladding of the fiber via the TFBG and strongly absorbed by the SWCNTs thin film. This absorption acts like a hot-wire raising the local temperature of the fiber, which is accurately detected by the TFBG resonance shift. In the experiments, the sensor's performances were investigated and controlled by adjusting the inherent angle of the TFBG, the thickness of SWCNTs film, and the input power of the pump laser. It was demonstrated that the developed anemometer exhibited significant light absorption efficiency up to 93%, and the maximum temperature of the local area on the fiber was heated up to 146.1°C under the relatively low pump power of 97.76 mW. The sensitivity of -0.3667 nm/(m/s) at wind speed of 1.0 m/s was measured with the selected 12° TFBG and 1.6 μm film.

A directional cylindrical anemometer with four sets of differential pressure sensors

NASA Astrophysics Data System (ADS)

Liu, C.; Du, L.; Zhao, Z.

2016-03-01

This paper presents a solid-state directional anemometer for simultaneously measuring the speed and direction of a wind in a plane in a speed range 1-40 m/s. This instrument has a cylindrical shape and works by detecting the pressure differences across diameters of the cylinder when exposed to wind. By analyzing our experimental data in a Reynolds number regime 1.7 × 103-7 × 104, we figure out the relationship between the pressure difference distribution and the wind velocity. We propose a novel and simple solution based on the relationship and design an anemometer which composes of a circular cylinder with four sets of differential pressure sensors, tubes connecting these sensors with the cylinder's surface, and corresponding circuits. In absence of moving parts, this instrument is small and immune of friction. It has simple internal structures, and the fragile sensing elements are well protected. Prototypes have been fabricated to estimate performance of proposed approach. The power consumption of the prototype is less than 0.5 W, and the sample rate is up to 31 Hz. The test results in a wind tunnel indicate that the maximum relative speed measuring error is 5% and the direction error is no more than 5° in a speed range 2-40 m/s. In theory, it is capable of measuring wind up to 60 m/s. When the air stream goes slower than 2 m/s, the measuring errors of directions are slightly greater, and the performance of speed measuring degrades but remains in an acceptable range of ±0.2 m/s.

1.5 μm lidar anemometer for true air speed, angle of sideslip, and angle of attack measurements on-board Piaggio P180 aircraft

NASA Astrophysics Data System (ADS)

Augere, B.; Besson, B.; Fleury, D.; Goular, D.; Planchat, C.; Valla, M.

2016-05-01

Lidar (light detection and ranging) is a well-established measurement method for the prediction of atmospheric motions through velocity measurements. Recent advances in 1.5 μm Lidars show that the technology is mature, offers great ease of use, and is reliable and compact. A 1.5 μm airborne Lidar appears to be a good candidate for airborne in-flight measurement systems. It allows measurements remotely, outside aircraft aerodynamic disturbance, and absolute air speed (no need for calibration) with great precision in all aircraft flight domains. In the framework of the EU AIM2 project, the ONERA task has consisted of developing and testing a 1.5 μm anemometer sensor for in-flight airspeed measurements. The objective of this work is to demonstrate that the 1.5 μm Lidar sensor can increase the quality of the data acquisition procedure for aircraft flight test certification. This article presents the 1.5 μm anemometer sensor dedicated to in-flight airspeed measurements and describes the flight tests performed successfully on-board the Piaggio P180 aircraft. Lidar air data have been graphically compared to the air data provided by the aircraft flight test instrumentation (FTI) in the reference frame of the Lidar sensor head. Very good agreement of true air speed (TAS) by a fraction of ms-1, angle of sideslip (AOS), and angle of attack (AOA) by a fraction of degree were observed.

Surface Renewal: Micrometeorological Measurements Avoiding the Sonic Anemometer

NASA Astrophysics Data System (ADS)

Suvocarev, K.; Reba, M. L.; Runkle, B.

2016-12-01

Surface renewal (SR) is micrometeorological technique that has been suggested as an inexpensive alternative to eddy covariance (EC). While it was originally dependent on a calibration coefficient (α), a recent approach by Castellví (2004) showed that SR can be used as a stand-alone method where α is estimated using similarity theory. This "self-calibration" method is suitable for measuring different scalar fluxes under all stability conditions (Castellví et. al, 2008). According to the same authors, SR does not demand a sonic anemometer as only the horizontal wind speed is necessary to arrive to α values. Therefore, it is more affordable and applicable in both roughness and inertial sub-layers which makes this method less stringent to fetch requirements (Castellví, 2012). The SR method has not yet been tested when the equipment is reduced to scalar measurements and a simple anemometer (RM Young 5103 Wind Monitor Sensor). Here, our objective was to test this approach over temperature, H2O, CO2 and CH4 time series. When EC is taken as a reference for a comparison, our initial results show that all fluxes measured by SR are higher than corresponding reference fluxes. The portion of overestimation is in the range of typical values reported by SR literature. Still, more research will be done to improve its understanding as the correlation between flux measurements is very high. The SR method seems to be promising in avoiding the use of sonic anemometry (and related errors) while maintaining fewer fetch requirements and the possibility to yield observations from all wind directions.

Wind data from Memphis airport

DOT National Transportation Integrated Search

1997-06-01

A 1300-foot array of horizontal and vertical single-axis anemometers was installed at the Memphis, TN Airport on 10- and 13-foot poles under the approach to Runway 727. One-minute average measurements were recorded continuously from mid August 1995 t...

Wind data from Kennedy Airport

DOT National Transportation Integrated Search

1997-06-01

A 700-foot array of horizontal and vertical single-axle anemometers was installed at New York's Kennedy Airport on 30-foot poles under the approach to Runway 31R. One-minute average measurements were recorded continuously, with a few breaks, from Sep...

Measurements of wake vortices interacting with the ground

DOT National Transportation Integrated Search

2005-09-01

Although wake vortices are known to decay more rapidly near the ground than away from the ground, the details of the ground interaction are not well understood. Propeller anemometer arrays located under the approach path have been used to study vorte...

HARVESTING ROADSIDE WIND ENERGY

EPA Science Inventory

For the first question, we have tried different routes to reach the Pennsylvania Department of Transportation (PennDOT) and request permission to attach an anemometer on the guardrails along Interstate I-81. However, due to the lack of current policy guiding such activities, P...

November 1996 Kennedy Airport Wake Vortex Test : Sensor Evaluation

DOT National Transportation Integrated Search

1997-08-01

In November 1996, a number of wake vortex and meteorological sensors were operated simultaneously in the middle marker region of Runway 31R at New York's Kennedy Airport. The vortex sensors included: 1)ground-based anemometer array, 2) cw 10-micron l...

Aircraft wake vortex takeoff tests at O'Hare International Airport

DOT National Transportation Integrated Search

1994-08-01

Three wake vortex measurement systems (anemometer, acoustic doppler, and laser : doppler) were used to collect wake vortex data from aircraft departing Runway 22L at : Chicago's O'Hare airport for nine months in 1980. The data were analyzed to determ...

OPTMAIN- A FORTRAN CODE FOR THE CALCULATION OF PROBE VOLUME GEOMETRY CHANGES IN A LASER ANEMOMETRY SYSTEM CAUSED BY WINDOW REFRACTION

NASA Technical Reports Server (NTRS)

Owen, A. K.

1994-01-01

The laser anemometer has provided the fluid dynamicist with a powerful tool for nonintrusively measuring fluid velocities. One of the more common types of laser anemometers, the laser fringe anemometer, divides a single laser beam into two parallel beams and then focuses them on a point in space called the "probe volume" (PV) where the fluid velocity is measured. Many applications using this method for measuring fluid velocities require the observation of fluids through a window. The passage of the laser beams through materials having different indices of refraction has the following effects: 1) the position of the probe volume will change; 2) the beams will uncross, i.e., no longer lie in the same plane at the probe volume location; and 3) for nonflat plate windows, the crossing angle of the two beams will change. OPTMAIN uses a ray tracing technique, which is not restricted to special cases, to study the changes in probe volume geometry and position due to refraction effects caused by both flat and general smooth windows. Input parameters are the indices of refraction on both sides of the window and of the window itself, the window shape, the assumed position of the probe volume and the actual position of the focusing lens relative to the window, the orientation of the plane which contains the laser beams, the beam crossing angle, and the laser beam wavelength. OPTMAIN is written in FORTRAN 77 for interactive execution. It has been implemented on a DEC VAX 11/780 under VMS 5.0 with a virtual memory requirement of 50K. OPTMAIN was developed in 1987.

Performance evaluation of Teledyne Geotech bivane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Addis, R.P.

1986-05-13

The new production prototype bivane manufactured by Teledyne Geotech underwent tests to evaluate its performance and determine its suitability as a replacement for obsolete instrumentation presently on the SRP meteorological towers. The bivane performs well for routine observations for emergency response, as well as for most routine plume dispersion research to be conducted at SRL for the foreseeable future. It should also be suitable for providing an accurate and reliable meteorological data base for engineering and meteorological applications for the next ten years. The bivane was tested in a wind tunnel where its Damping Ratio was found to be 0.30more » (azimuth) and 0.29 (elevation), which contrasts with 0.4 claimed by the manufacturer's preliminary specifications. Although the measured damping is less than the optimum value (0.43), it is estimated that the bivane will be able to measure the turbulent parameters (standard deviation of azimuth and elevation) used in the SRP emergency response codes, within 8%. The bivane's suitability as a research tool for measuring turbulent fluxes was determined by comparison with results from a sonic anemometer. The mean bivane momentum flux measurements were within 5% of those of the sonic, averaged over all measured flux intensities, and within 10% of the sonic for fluxes less than or equal to -0.05 m/sup 2//s/sup 2/. During periods of low fluxes, such as may occur under stable nocturnal conditions, a higher damping ratio (approx. 0.4) and a smaller natural wavelength would improve the bivane response to high frequency turbulence. The cup anemometer paired with the bivane, also performed well in the tests. An intercomparison of wind speeds with those measured by the sonic anemometer showed a mean difference of only 1 cm/s (0.02 mph).« less

AVOSS Windline at Dallas/Ft. Worth Airport Volume 1 Installation and Operation

DOT National Transportation Integrated Search

2001-05-01

A 259-meter windline, with horizontal and vertical single-axis anemometers mounted on 9-meter poles, was installed at the Dallas/Ft. Worth Airport under the approach to Runway 17C, as part of NASA's Aircraft Vortex Spacing System (AVOSS) development ...

Evaluation of the watchdog weather station to reduce drift from MDOT spray trucks.

DOT National Transportation Integrated Search

2015-09-01

Wind speed data collected with the Spectrum Watchdog Sprayer Station were compared to data : recorded with a Young 05103-5 anemometer at the Rodney R. Foil Plant Science Research : Center on the Mississippi State University campus June and July, 2014...

Basic Weather Facts Study Texts for Students.

ERIC Educational Resources Information Center

Ontario Ministry of the Environment, Toronto.

This pamphlet offers information to teachers and students concerning basic facts about weather and how to construct simple weather measurement devices. Directions, necessary materials, procedures, and instructions for use are given for four weather predicting instruments: wind vane, rain gauge, barometer, anemometer. Information is provided on…

A comparison of selected vertical wind measurement techniques on basis of the EUCAARI IMPACT observations

NASA Astrophysics Data System (ADS)

Arabas, S.; Baehr, C.; Boquet, M.; Dufournet, Y.; Pawlowska, H.; Siebert, H.; Unal, C.

2009-04-01

The poster presents a comparison of selected methods for determination of the vertical wind in the boundary layer used during the EUCAARI IMPACT campaign that took place in May 2008 in The Netherlands. The campaign covered a monthlong intensified ground-based and airborne measurements in the vicinity of the CESAR observatory in Cabauw. Ground-based vertical wind remote sensing was carried out using the Leosphere WindCube WLS70 IR Doppler lidar, Vaisala LAP3000 radar wind-profiler and the TUDelft TARA S-band radar. In-situ airborne measurements were performed using an ultrasonic anemometer (on the ACTOS helicopter underhung platform) and a 5-hole pressure probe (on the SAFIRE ATR-42 airplane radome). Several in-situ anemometers were deployed on the 200-meter high tower of the CESAR observatory. A summary of the characteristics and principles of the considered techniques is presented. A comparison of the results obtained from different platforms depicts the capabilities of each technique and highlights the time, space and velocity resolutions.

Measured and predicted rotor performance for the SERI advanced wind turbine blades

NASA Astrophysics Data System (ADS)

Tangler, J.; Smith, B.; Kelley, N.; Jager, D.

1992-02-01

Measured and predicted rotor performance for the Solar Energy Research Institute (SERI) advanced wind turbine blades were compared to assess the accuracy of predictions and to identify the sources of error affecting both predictions and measurements. An awareness of these sources of error contributes to improved prediction and measurement methods that will ultimately benefit future rotor design efforts. Propeller/vane anemometers were found to underestimate the wind speed in turbulent environments such as the San Gorgonio Pass wind farm area. Using sonic or cup anemometers, good agreement was achieved between predicted and measured power output for wind speeds up to 8 m/sec. At higher wind speeds an optimistic predicted power output and the occurrence of peak power at wind speeds lower than measurements resulted from the omission of turbulence and yaw error. In addition, accurate two-dimensional (2-D) airfoil data prior to stall and a post stall airfoil data synthesization method that reflects three-dimensional (3-D) effects were found to be essential for accurate performance prediction.

The measurement of sperm motility by the fibre optic Doppler anemometer as a prediction of bovine fertility

NASA Astrophysics Data System (ADS)

Bullock, J. G.; Ross, D. A.

The fibre optic Doppler anemometer (FODA) has been used to develop an accurate quantitative method of routinely assessing bull fertility. This method is of importance to the artificial insemination industry because the present qualitative estimation, performed by viewing semen using a microscope, can only set broad limits of quality. Laser light from the FODA was directed into diluted semen samples and the back scattered light was measured. A digital correlator was used to calculate the signal correlation of the back scattered light. The resultant data curves were interpreted in terms of the collective motility and swimming speed of the spermatozoa using a microcomputer. These two parameters are accepted as being indicative of fertility. The accuracy of this method is demonstrated by examination of results obtained in an experiment where enzymes, thought to alter fertility, were added to semen. The effect of the enzymes on the swimming speed and motility was clearly demonstrated.

An investigation of the open-loop amplification of Reynolds number dependent processes by wave distortion

NASA Technical Reports Server (NTRS)

Purdy, K. R.; Ventrice, M. B.; Fang, J.

1972-01-01

Analytical and experimental studies were initiated to determine if the response of a constant temperature hot wire anemometer to acoustic oscillations could serve as an analog to the response of the drop vaporization burning rate process to acoustic oscillations, and, perhaps, also as an analog to any Reynolds number dependent process. The motivation behind this study was a recent analytical study which showed that distorted acoustic oscillations could amplify the open-loop response of vaporization limited combustion. This type of amplification may be the cause of unstable combustion in liquid propellant rocket engines. The analytical results obtained for the constant temperature anemometer are similar in nature to those previously obtained for vaporization limited combustion and indicate that the response is dependent on the amount and type of distortion as well as other factors, such as sound pressure level, Mach number and hot wire temperature. Preliminary results indicate qualitative agreement between theory and experiment.

Overview of the TILDAE High-Altitude Balloon Mission

NASA Astrophysics Data System (ADS)

Godbole, N. H.; Maruca, B.; Marino, R.; Sundkvist, D. J.; Constantin, S.; Zimmerman, H.; Carbone, V.

2016-12-01

Though the presence of intermittent turbulence in the stratosphere has been well established, much remains unknown about it. In situ observations of this phenomenon, which have provided the greatest detail of it, have typically been achieved via sounding balloons (i.e., small balloons which burst at peak altitude) carrying constant-temperature "hot wire" anemometers (CTAs). The Turbulence and Intermittency Long-Duration Atmospheric Experiment (TILDAE) was developed to test a new paradigm for stratospheric observations. Rather than flying on a sounding balloon, TILDAE was incorporated as an "add-on" experiment to the payload of a NASA long-duration balloon mission that launched in January, 2016 from McMurdo Station, Antarctica. Furthermore, TILDAE's key instrument was a sonic anemometer, which (relative to a CTA) provides better-calibrated measurements of wind velocity and more-robust separation of velocity components. This presentation focuses on the technical details of TILDAE's instrumentation and the performance thereof during its flight. Potential design improvements for future flights are also discussed.

Ground-Based Measurements of the Wake Vortex Characteristics of a B-747 Aircraft in Various Configurations

DOT National Transportation Integrated Search

1978-12-01

A Boeing 747 aircraft flew 54 passes at low altitude over ground based sensors. Vortex velocities were measured by a laser Doppler velocimeter, an array of monostatic acoustic sounders, and an array of propeller anemometers. Flow visualization of the...

3D turbulence measurements using three intersecting Doppler LiDAR beams: validation against sonic anemometry

NASA Astrophysics Data System (ADS)

Carbajo Fuertes, Fernando; Valerio Iungo, Giacomo; Porté-Agel, Fernando

2013-04-01

Nowadays communities of researchers and industry in the wind engineering and meteorology sectors demand extensive and accurate measurements of atmospheric boundary layer turbulence for a better understanding of its role in a wide range of onshore and offshore applications: wind resource evaluation, wind turbine wakes, meteorology forecast, pollution and urban climate studies, etc. Atmospheric turbulence has been traditionally investigated through sonic anemometers installed on meteorological masts. However, the setup and maintenance of instrumented masts is generally very costly and the available location for the measurements is limited by the fixed position and height of the facility. In order to overcome the above-mentioned shortcomings, a measurement technique is proposed, based on the reconstruction of the three-dimensional velocity vector from simultaneous measurements of three intersecting Doppler wind LiDARs. This measuring technique presents the main advantage of being able to measure the wind velocity at any point in space inside a very large volume, which can be set and optimized for each test. Furthermore, it is very flexible regarding its transportation, installation and operation in any type of terrain. On the other hand, LiDAR measurements are strongly affected by the aerosol concentration in the air, precipitation, and the spatial and temporal resolution is poorer than that of a sonic anemometer. All this makes the comparison between these two kinds of measurements a complex task. The accuracy of the technique has been assessed by this study against sonic anemometer measurements carried out at different heights on the KNMI's meteorological mast at Cabauw's experimental site for atmospheric research (CESAR) in the Netherlands. An early uncertainty analysis shows that one of the most important parameters to be taken into account is the relative angles between the intersecting laser beams, i.e., the position of each LiDAR on the terrain and their elevation and azimuth angles. Following this analysis, different LiDAR layouts have been tested, e.g., one vertical beam and the other two almost horizontal, all three equidistant with the same elevation angle, etc. Preliminary results show different degrees of agreement between the proposed technique and the sonic anemometers depending on the LiDARs layout, which is in agreement with the uncertainty analysis carried out. The best configurations show a good agreement for the three components of the velocity and turbulence spectra, thus proving the ability of the technique to measure accurately atmospheric turbulence, consolidating it as a very interesting alternative to meteorological masts for many different applications.

Comparisons of Measurements Made Using Two Sodars in an Urban Environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berg, Larry K.; Reynolds, R. M.; Allwine, K Jerry

2006-02-01

A Scintec MFAS sodar and an AeroVironment Model 3000 Mini-sodar were operated at the Stevens Institute of Technology (SIT) during the Urban Dispersion Program’s New York City field campaign that was conducted between 7 March and 21 March 2005. The Scintec sodar was located on a dock on the Hudson River. The AeroVironment sodar was located on the roof of the Howe Center, a 17-story building located near the Hudson River. The AeroVironment sodar was approximately 90 m above the Scintec, and the horizontal separation of the two units was approximately 350 m. The Scintec MFAS sodar and the AeroVironmentmore » mini sodar operate at different frequencies, with the AeroVironment operating at a much higher frequency. Because of these differences, different range gate spacing were selected for each instrument. The range gate spacing used with Scintec MFAS sodar was particularly course to try to probe deeper into the boundary layer. In addition to these two sodars, a meteorological tower was located at the top of the Howe Center. The original experimental plan called for us to operate the Scintec sodar on top the Howe Center, but there was significant ambient noise that degraded the performance. Therefore, the AeroVironment sodar was placed on the building top, while the Scintec MFAS sodar was moved to a dock near the Hudson River. Unfortunately, this location was close to a number of student dormitories, so the sodar could only be operated during Intensive Operations Periods (IOPs). Detailed comparisons of the wind speed and wind direction measured by both sodars and the propeller anemometer have been completed for each IOP. At a height of 100 m above the river (very close to the height of the Howe Center), the wind speed measured by the propeller anemometer and the two sodars were very close. During both IOPs there were times when the wind direction measured by the AeroVironment sodar was much different than the wind direction measured by the Scintec MFAS sodar and the propeller anemometer. At a height of 200 m above the Hudson River, the wind speed measured by the Scintec MFAS sodar was significantly smaller than the wind speed measured using the AeroVironment sodar. At this height, there were also large differences in the wind directions measured by the two sodars, with the wind direction measured by the Scintec being closer to the wind direction measured by the propeller anemometer mounted on top of the Howe Center.« less

Velocity profile development for a poultry facility acid scrubber

USDA-ARS?s Scientific Manuscript database

Determination of the air velocity profile for 12 experimental configurations (ECs) of an acid scrubber was carried out using an equal area traverse method with a vane axial anemometer. Four velocity profile plots were created for each configuration to determine the four optimal ECs. ECs were selecte...

Surface Meteorological Station - ANL 10m, (1) Sonics, (1) EBBR, Physics site-3 - Raw Data

DOE Data Explorer

Muradyan, Paytsar

2017-10-23

Sonic anemometers from Physics Site-3 and Site-9 provide wind components and virtual temperature. The energy balance Bowen ratio (EBBR) station at Physics site-3 provides measurements of the surface fluxes of latent and sensible heat, net radiation, and surface soil heat flux.

Surface Meteorological Station - ANL 10m, (1) Sonic, Physics site-9 - Raw Data

DOE Data Explorer

Muradyan, Paytsar

2017-10-23

Sonic anemometers from Physics Site-3 and Site-9 provide wind components and virtual temperature. The energy balance Bowen ratio (EBBR) station at Physics site-3 provides measurements of the surface fluxes of latent and sensible heat, net radiation, and surface soil heat flux.

Surface Meteorological Station - ANL 10m, (1) Sonics, (1) EBBR, Physics site-3 - Reviewed Data

DOE Data Explorer

Muradyan, Paytsar

2018-03-14

Sonic anemometers from Physics Site-3 and Site-9 provide wind components and virtual temperature. The energy balance Bowen ratio (EBBR) station at Physics site-3 provides measurements of the surface fluxes of latent and sensible heat, net radiation, and surface soil heat flux.

Surface Meteorological Station - ANL 10m, (1) Sonic, Physics site-9 - Reviewed Data

DOE Data Explorer

Muradyan, Paytsar

2018-03-14

Sonic anemometers from Physics Site-3 and Site-9 provide wind components and virtual temperature. The energy balance Bowen ratio (EBBR) station at Physics site-3 provides measurements of the surface fluxes of latent and sensible heat, net radiation, and surface soil heat flux.

Flow Dynamics In Eccentrically Rotating Flasks Used For Dispersant Effectiveness Testing

EPA Science Inventory

The evaluation of dispersant effectiveness used for oil spills is commonly done using tests conducted in laboratory flasks. We used a Hot Wire Anemometer (HWA) to characterize mixing dynamics in the Swirling Flask (SF) and the Baffled Flask (BF), the latter is being considered b...

Analysis of Ground-Wind Vortex Sensing System Data from O'Hare International Airport

DOT National Transportation Integrated Search

1980-09-01

From July 1976 through September 1977, aircraft wake vortex data were collected on the approach to runways 14R, 27R, and 32L at O'Hare International Airport. The vortices from over 21,000 aircraft were tracked using the propeller anemometer Ground-Wi...

EVALUATION OF MIXING ENERGY IN LABORATORY FLASKS USED FOR DISPERSANT EFFECTIVENESS TESTING

EPA Science Inventory

The evaluation of dispersant effectiveness used for oil spills is commonly done using tests conducted in laboratory flasks. The success of a test relies on replication of the conditions at sea. We used a hot wire anemometer to characterize the turbulence characteristics in the s...

75 FR 81313 - Petitions for Modification of Existing Mandatory Safety Standards

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-27

... for methane, oxygen, and carbon monoxide concentrations using an approved hand-held device; (iv) measure air quantity using an appropriately calibrated anemometer. Methane gas or other harmful, noxious... percent methane above the previous reading or a 10 percent unplanned change in the airflow quantity from...

NEW VERSATILE AEROSOL GENERATION SYSTEM DEVELOPED FOR USE IN A LARGE WIND TUNNEL

EPA Science Inventory

A new aerosol generation system was developed to accommodate a variety of research activities performed within a large wind tunnel. Because many of the velocity measurements are taken in the wind tunnel with a laser Doppler anemometer (LDA), it is necessary to maintain an aero...

Wind adjustment factors for predicting fire behavior in three fuel types in Alaska.

Treesearch

Rodney A. Norum

1983-01-01

Factors for adjusting wind velocities from the 20-foot standard anemometer height down to an average wildfire midflame height (3.5 ft for the fuels studied) are given for exposed, partially sheltered, and sheltered fuels in Alaska. The values are suitable for predicting wildfire behavior.

Mars Acoustic Anemometer

NASA Astrophysics Data System (ADS)

Banfield, D. J.

2012-12-01

We have developed a very high performance anemometer (wind gauge) for use at Mars. This instrument has great scientific as well as strategic reasons to be included on all future missions to the surface of Mars. We will discuss why we set out to develop this instrument, as well as why the previous wind sensors for Mars are insufficient to meet the scientific and strategic needs at Mars. We will also discuss how the instrument works, and how it differs from terrestrial counterparts. Additionally, we will discuss the current status of the instrument. Measuring winds at Mars is important to better understand the atmospheric circulation at Mars, as well as exchange between the surface and atmosphere. The main conduit of transport of water, and hence its current stability at any particular location on Mars is controlled by these atmospheric motions and the exchange between surface and atmosphere. Mars' large-scale winds are moderately well understood from orbital observations, but the interaction with the surface can only be addressed adequately in situ. Previous anemometers have been 2-D (with the exception of REMS on MSL) and slow response (typically <1Hz), and relatively low sensitivity/accuracy (>1 m/s). Our instrument is capable of fully 3-D measurements, with fast response (>20 Hz) and great sensitivity/accuracy (~3 cm/s). This significant step forward in performance is important for the surface-atmosphere exchanges of heat, momentum and volatiles. In particular, our instrument could directly measure the heat and momentum fluxes between surface and atmosphere using eddy-flux techniques proven terrestrially. When combined with a fast response volatile analysis instrument (e.g., a TLS) we can also measure eddy fluxes of volatile transport. Such a study would be nearly impossible to carry out with preceding anemometers sent to Mars with insufficient response time and sensitivity to adequately sample the turbulent eddies. Additionally, our instrument, using acoustics is far less susceptible to contaminating influences as other techniques (e.g., hot wire/hot film) that have been used for anemometry at Mars. Our instrument is conceptually derived from the commercial terrestrial sonic anemometers, but uses specialized acoustic transducers to optimally couple with the low density martian air as well as survive the extreme temperature swings on Mars. Additionally, we use sophisticated signal processing to extract as much information as possible in the low S/N environment that is achievable at Mars. We have developed our instrument through to TRL 5, proving it in a martian wind tunnel in Denmark. We found wind speed sensitivities and precision to be of order 3 cm/s, and with appropriate calibration, accuracy can be similar, even when operating at 20-100 Hz. We will also test this instrument at 120,000' altitude (i.e., equivalent to Mars atmospheric density) as an autonomous package on a stratospheric balloon. We are currently developing a TRL 6 version of the instrument that will be tested once again in the Denmark Mars Wind Tunnel. We expect our flight configuration instrument to be about 1 kg, including a 1.5m mast. It will also draw about 2-3W of power. This instrument is now ready to be proposed for future Mars missions, where we believe it will make a significant contribution and a step forward in Mars atmospheric science.

Design and Calibration of an Inexpensive Digital Anemometer

ERIC Educational Resources Information Center

Hernandez-Walls, R.; Rojas-Mayoral, E.; Baez-Castillo, L.; Rojas-Mayoral, B.

2008-01-01

An inexpensive and easily implemented device to measure wind velocity is proposed. This prototype has the advantage of being able to measure both the speed and the direction of the wind in two dimensions. The device utilizes a computational interface commonly referred to as a "mouse." The mouse proposed for this prototype contains an…

Handbook of Supersonic Aerodynamics. Section 20. Wind Tunnel Instrumentation and Operation

DTIC Science & Technology

1961-01-01

colored Wratten gelatin filters are mounted in a suitable holder with the sides of the strips parallel and close enough to prevent light from passing...Knoblork, F. D., "A Hot-Wire Anemometer Developed for Full-Scale 0 Airship Measurements," The Daniel Guggenheim Airship Inst., pp. 58-61, 1935. 619

40 CFR 1065.245 - Sample flow meter for batch sampling.

Code of Federal Regulations, 2010 CFR

2010-07-01

... rates or total flow sampled into a batch sampling system over a test interval. You may use the... rates or total raw exhaust flow over a test interval. (b) Component requirements. We recommend that you... averaging Pitot tube, or a hot-wire anemometer. Note that your overall system for measuring sample flow must...

Parametric study of beam refraction problems across laser anemometer windows

NASA Technical Reports Server (NTRS)

Owen, A. K.

1986-01-01

The experimenter is often required to view flows through a window with a different index of refraction than either the medium being observed or the medium that the laser anemometer is immersed in. The refraction that occurs at the window surfaces may lead to undesirable changes in probe volume position or beam crossing angle and can lead to partial or complete beam uncrossing. This report describes the results of a parametric study of this problem using a ray tracing technique to predict these changes. The windows studied were a flat plate and a simple cyclinder. For the flat-plate study: (1) surface thickness, (2) beam crossing angle, (3) bisecting line - surface normal angle, and (4) incoming beam plane surface orientation were varied. For the cylindrical window additional parameters were also varied: (1) probe volume immersion, (2) probe volume off-radial position, and (3) probe volume position out of the R-theta plane of the lens. A number of empirical correlations were deduced to aid the interested reader in determining the movement, uncrossing, and change in crossing angle for a particular situation.

A parametric study of the beam refraction problems across laser anemometer windows

NASA Technical Reports Server (NTRS)

Owen, Albert K.

1986-01-01

The experimenter is often required to view flows through a window with a different index of refraction than either the medium being observed or the medium that the laser anemometer is immersed in. The refraction that occurs at the window surfaces may lead to undesirable changes in probe volume position or beam crossing angle and can lead to partial or complete beam uncrossing. This report describes the results of a parametric study of this problem using a ray tracing technique to predict these changes. The windows studied were a flat plate and a simple cylinder. For the flat-plate study: (1) surface thickness, (2) beam crossing angle, (3) bisecting line - surface normal angle, and (4) incoming beam plane surface orientation were varied. For the cylindrical window additional parameters were also varied: (1) probe volume immersion, (2) probe volume off-radial position, and (3) probe volume position out of the r-theta plane of the lens. A number of empirical correlations were deduced to aid the reader in determining the movement, uncrossing, and change in crossing angle for a particular situations.

Instantaneous velocity measurement of AC electroosmotic flows by laser induced fluorescence photobleaching anemometer with high temporal resolution

NASA Astrophysics Data System (ADS)

Zhao, Wei; Yang, Fang; Qiao, Rui; Wang, Guiren; Rui Qiao Collaboration

2015-11-01

Understanding the instantaneous response of flows to applied AC electric fields may help understand some unsolved issues in induced-charge electrokinetics and enhance performance of microfluidic devices. Since currently available velocimeters have difficulty in measuring velocity fluctuations with frequency higher than 1 kHz, most experimental studies so far focus only on the average velocity measurement in AC electrokinetic flows. Here, we present measurements of AC electroosmotic flow (AC-EOF) response time in microchannels by a novel velocimeter with submicrometer spatial resolution and microsecond temporal resolution, i.e. laser-induced fluorescence photobleaching anemometer (LIFPA). Several parameters affecting the AC-EOF response time to the applied electric signal were investigated, i.e. channel length, transverse position and solution conductivity. The experimental results show that the EOF response time under a pulsed electric field decreases with the reduction of the microchannel length, distance between the detection position to the wall and the conductivity of the solution. This work could provide a new powerful tool to measure AC electrokinetics and enhance our understanding of AC electrokinetic flows.

Aerosol and trace gas flux measurements from a mobile car platform on the highway

NASA Astrophysics Data System (ADS)

Gordon, M.; Miller, S. J.; Staebler, R. M.; Taylor, P.

2016-12-01

Mobile flux measurements of aerosols and trace gases at the surface can provide valuable information about the vertical transport of these compounds from near-surface sources. These measurements can be complimentary to stationary tower measurements or elevated mobile measurements from aircraft and unmanned aerial systems (UAS). In July, 2016 a mobile platform (Toyota Highlander), outfitted with a sonic anemometer (ATI), an open path CO2/H2O analyzer (Licor), and an ultrafine particle sizer (DMT), was driven on highways as part of a chasing study to investigate vehicle-induced turbulence and mixing. The open path analyzer and particle sizer inlet were co-located with the anemometer in order to investigate the feasibility of making flux measurements of heat, momentum, water vapour, CO2, and sub-micron aerosols on the highway. These highway flux measurements are compared to stationary platform measurements made upwind and downwind of the highway. Statistical and spectral analyses are used to demonstrate the validity of the mobile measurements. Uncertainties due to flow distortion around the vehicle, under-sampling, and heterogeneity of the vertical temperature and concentrations are investigated and discussed.

Laser transit anemometer and Pitot probe comparative measurements in a sharp cone boundary layer at Mach 4

NASA Technical Reports Server (NTRS)

Hunter, W. W., Jr.; Ocheltree, S. L.; Russ, C. E., Jr.

1991-01-01

Laser transit anemometer (LTA) measurements of a 7 degree sharp cone boundary layer were conducted in the Air Force/AEDC Supersonic Tunnel A Mach 4 flow field. These measurements are compared with Pitot probe measurements and tricone theory provided by AEDC staff. Measurements were made both in laminar and turbulent boundary layers of the model. Comparison of LTA measurements with theory showed agreement to better than 1 percent for the laminar boundary layer cases. This level of agreement was obtained after small position corrections, 0.01 to 0.6 mm, were applied to the experimental data sets. Pitot probe data when compared with theory also showed small positioning errors. The Pitot data value was also limited due to probe interference with the flow near the model. The LTA turbulent boundary layer data indicated a power law dependence of 6.3 to 6.9. The LTA data was analyzed in the time (Tau) domain in which it was obtained and in the velocity domain. No significant differences were noted between Tau and velocity domain results except in one turbulent boundary layer case.

Calculation of tip clearance effects in a transonic compressor rotor

NASA Technical Reports Server (NTRS)

Chima, R. V.

1996-01-01

The flow through the tip clearance region of a transonic compressor rotor (NASA rotor 37) was computed and compared to aerodynamic probe and laser anemometer data. Tip clearance effects were modeled both by gridding the clearance gap and by using a simple periodicity model across the ungridded gap. The simple model was run with both the full gap height, and with half the gap height to simulate a vena-contracta effect. Comparisons between computed and measured performance maps and downstream profiles were used to validate the models and to assess the effects of gap height on the simple clearance model. Recommendations were made concerning the use of the simple clearance model. Detailed comparisons were made between the gridded clearance gap solution and the laser anemometer data near the tip at two operating points. The computer results agreed fairly well with the data but overpredicted the extent of the casing separation and underpredicted the wake decay rate. The computations were then used to describe the interaction of the tip vortex, the passage shock, and the casing boundary layer.

Field Micrometeorological Measurements, Process-Level Studies and Modeling of Methane and Carbon Dioxide Fluxes in a Boreal Wetland Ecosystem

NASA Technical Reports Server (NTRS)

Verma, S. B.; Arkebauer, T. J.; Ullman, F. G.; Valentine, D. W.; Parton, W. J.; Schimel, D. S.

1998-01-01

The main instrumentation platform consisted of eddy correlation sensors mounted on a scaffold tower at a height of 4.2 m above the peat surface. The sensors were attached to a boom assembly which could be rotated into the prevailing winds. The boom assembly was mounted on a movable sled which, when extended, allowed sensors to be up to 2 m away from the scaffolding structure to minimize flow distortion. When retracted, the sensors could easily be installed, serviced or rotated. An electronic level with linear actuators allowed the sensors to be remotely levelled once the sled was extended. Two instrument arrays were installed. A primary (fast-response) array consisted of a three-dimensional sonic anemometer, a methane sensor (tunable diode laser spectrometer), a carbon dioxide/water vapor sensor, a fine wire thermocouple and a backup one-dimensional sonic anemometer. The secondary array consisted of a one-dimensional sonic anemometer, a fine wire thermocouple and a Krypton hygrometer. Descriptions of these sensors may be found in other reports (e.g., Verma; Suyker and Verma). Slow-response sensors provided supporting measurements including mean air temperature and humidity, mean horizontal windspeed and direction, incoming and reflected solar radiation, net radiation, incoming and reflected photosynthetically active radiation (PAR), soil heat flux, peat temperature, water-table elevation and precipitation. A data acquisition system (consisting of an IBM compatible microcomputer, amplifiers and a 16 bit analog-to-digital converter), housed in a small trailer, was used to record the fast response signals. These signals were low-pass filtered (using 8-pole Butterworth active filters with a 12.5 Hz cutoff frequency) and sampled at 25 Hz. Slow-response signals were sampled every 5 s using a network of CR21X (Campbell Scientific, Inc., Logan Utah) data loggers installed in the fen. All signals were averaged over 30-minute periods (runs).

Momentum and particle transport in a nonhomogenous canopy

NASA Astrophysics Data System (ADS)

Gould, Andrew W.

Turbulent particle transport through the air plays an important role in the life cycle of many plant pathogens. In this study, data from a field experiment was analyzed to explore momentum and particle transport within a grape vineyard. The overall goal of these experiments was to understand how the architecture of a sparse agricultural canopy interacts with turbulent flow and ultimately determines the dispersion of airborne fungal plant pathogens. Turbulence in the vineyard canopy was measured using an array of four sonic anemometers deployed at heights z/H 0.4, 0.9, 1.45, and 1.95 where z is the height of the each sonic and H is the canopy height. In addition to turbulence measurements from the sonic anemometers, particle dispersion was measured using inert particles with the approximate size and density of powdery mildew spores and a roto-rod impaction trap array. Measurements from the sonic anemometers demonstrate that first and second order statistics of the wind field are dependent on wind direction orientation with respect to vineyard row direction. This dependence is a result of wind channeling which transfers energy between the velocity components when the wind direction is not aligned with the rows. Although the winds have a strong directional dependence, spectra analysis indicates that the structure of the turbulent flow is not fundamentally altered by the interaction between wind direction and row direction. Examination of a limited number of particle release events indicates that the wind turning and channeling observed in the momentum field impacts particle dispersion. For row-aligned flow, particle dispersion in the direction normal to the flow is decreased relative to the plume spread predicted by a standard Gaussian plume model. For flow that is not aligned with the row direction, the plume is found to rotate in the same manner as the momentum field.

Sonic flow distortion experiment

NASA Astrophysics Data System (ADS)

Peters, Gerhard; Kirtzel, Hans-Jürgen; Radke, Jürgen

2017-04-01

We will present results from a field experiment with multiple sonic anemometers, and will address the question about residual errors of wind tunnel based calibrations that are transferred to atmospheric measurements. Ultrasonic anemometers have become standard components of high quality in-situ instrumentations, because of the long term calibration stability, fast response, wide dynamic range, and various options of built in quality control. On the downside of this technology is the fact that the sound transducers and the carrying structure represent obstacles in the flow causing systematic deviations of the measured flow from the free flow. Usually, the correction schemes are based on wind tunnel observations of the sonic-response as function of angle of attack under stationary conditions. Since the natural atmospheric flow shows turbulence intensities and scales, which cannot be mimicked in a wind tunnel, it is suspected that the wind-tunnel based corrections may be not (fully) applicable to field data. The wide spread use of sonic anemometers in eddy flux instrumentations for example in the frame of EuroFlux, AmeriFlux or other international observation programs has therefore prompted a - still controversial - discussion of the significance of residual flow errors. In an attempt to quantify the flow distortion in free field conditions, 12 identical 3-component sonics with 120 degree head symmetry were operated at the north margin of an abandoned airfield. The sonics were installed in a straight line in WE-direction at 2.6 m height with a mutual distance of 3 meters and with an azimuth increment of the individual sonics of 11 degrees. Synchronous raw data were recorded with 20 Hz sample rate. Data of about 12 hours with southerly winds (from the relatively flat airfield) were analyzed. Statistical homogeneity of the wind field in the range of the instruments line was assumed, but a variable finite turbulent decay constant was accounted for, which was estimated from the data. The free field flow distortion estimates will be discussed in comparison with wind tunnel observations.

Field evaluation of open and closed-path CO2 flux systems over asphalt surface

NASA Astrophysics Data System (ADS)

Bogoev, I.; Santos, E.

2016-12-01

Eddy covariance (EC) is a widely used method for quantifying surface fluxes of heat, water vapor and carbon dioxide between ecosystems and the atmosphere. A typical EC system consists of an ultrasonic anemometer measuring the 3D wind vector and a fast-response infrared gas analyzer for sensing the water vapor and CO2 density in the air. When using an open-path analyzer that detects the constituent's density in situ a correction for concurrent air temperature and humidity fluctuations must be applied, Webb et al. (1980). In environments with small magnitudes of CO2 flux (<5µmol m-2 s-1) and in the presence of high sensible heat flux, like wintertime over boreal forest, open-path flux measurements have been challenging since the magnitude of the density corrections are as large as the uncorrected CO2 flux itself. A new technology merging the sensing paths of the gas analyzer and the sonic anemometer has been recently developed. This new integrated instrument allows a direct measurement of CO2 mixing ratio in the open air and has the potential to improve the quality of the temperature related density corrections by synchronously measuring the sensible heat flux in the optical path of the gas analyzer. We evaluate the performance and the accuracy of this new sensor over a large parking lot with an asphalt surface where the CO2 fluxes are considered low and the interfering sensible heat fluxes are above 200 Wm-2. A co-located closed-path EC system is used as a reference measurement to examine any systematic biases and apparent CO2 uptake observed with open-path sensors under high sensible heat flux regimes. Half-hour mean and variance of CO2 and water vapor concentrations are evaluated. The relative spectral responses, covariances and corrected turbulent fluxes using a common sonic anemometer are analyzed. The influence of sensor separation and frequency response attenuation on the density corrections is discussed.

Microscale out-of-plane anemometer

NASA Technical Reports Server (NTRS)

Liu, Chang (Inventor); Chen, Jack (Inventor)

2005-01-01

A microscale out-of-plane thermal sensor. A resistive heater is suspended over a substrate by supports raised with respect to the substrate to provide a clearance underneath the resistive heater for fluid flow. A preferred fabrication process for the thermal sensor uses surface micromachining and a three-dimensional assembly to raise the supports and lift the resistive heater over the substrate.

WIND TUNNEL INVESTIGATION OF THE RESPONSE OF A SONIC ANEMOMETER

EPA Science Inventory

An Applied Technology Inc. (ATI) sonic of the type used by J. C. Kaimal at the Boulder Tower was tested in the large wind tunnel at the U.S. EPA Fluid Modeling Facility. The wind tunnel is approximately 6 ft high, 10 ft wide with a test section bed 60 ft long. The air speed in th...

Local isotropy and refractive index fluctuations in the surface layer of the atmosphere

NASA Technical Reports Server (NTRS)

Portman, D. J.

1969-01-01

Theoretical and experimental evidence for the existence of local isotropy is briefly examined and conflicting results are found. Recent measurements of temperature spectra support earlier hot wire anemometer and optical scintillation measurements that show little evidence of local isotropy at 1 to 1.5 meters over an extensive uniform and level grass covered field.

Intensity, Scale, and Spectra of Turbulence in Mixing Region of Free Subsonic Jet

NASA Technical Reports Server (NTRS)

Laurence, James C

1956-01-01

Report presents the results of the measurements of intensity of turbulence, the longitudinal and lateral correlation coefficients, and the spectra of turbulence in a 3.5-inch-diameter free jet measured with hot-wire anemometers at exit Mach numbers from 0.2 to 0.7 and Reynolds numbers from 192,000 to 725,000.

Study of Airflow Out of the Mouth During Speech.

ERIC Educational Resources Information Center

Catford, J.C.; And Others

Airflow outside the mouth is diagnostic of articulatory activities in the vocal tract, both total volume-velocity and the distribution of particle velocities over the flow-front being useful for this purpose. A system for recording and displaying both these types of information is described. This consists of a matrix of l6 hot-wire anemometer flow…

Quantification of absolute blood velocity using LDA

NASA Astrophysics Data System (ADS)

Borozdova, M. A.; Fedosov, I. V.; Tuchin, V. V.

2018-04-01

We developed novel schematics of a Laser Doppler anemometer where measuring volume is comparable with the red blood cell (RBC) size and a small period of interference fringes improves device resolution. The technique was used to estimate Doppler frequency shift at flow velocity measurements. It has been shown that technique is applicable for measurements in whole blood.

Insensitivity of single particle time domain measurements to laser velocimeter 'Doppler ambiguity.'

NASA Technical Reports Server (NTRS)

Johnson, D. A.

1973-01-01

It is shown that single particle time domain measurements in high speed gas flows obtained by a laser velocimeter technique developed for use in wind tunnels are not affected by the so-called 'Doppler ambiguity.' A comparison of hot-wire anemometer and laser velocimeter measurements taken under similar flow conditions is used for the demonstration.

How to make a wind-movement recorder from any spare drum-type recorder

Treesearch

Irvin C. Reigner

1964-01-01

The automatic recording of wind movement is sometimes essential to experiments in forestry and watershed-management research. Wind-movement data are often obtained by periodic reading of the anemometer dial, but occasionally data are required for variable intervals and at times when observations cannot be made easily. Instruments designed to record wind movement are...

Evaluation of Tower Shadowing on Anemometer Measurements at Los Alamos National Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruggeman, David Alan

2016-06-14

The objective of this study is to evaluate the effect of tower shadowing from the meteorology towers at LANL during 2014. This study is in response to the Department of Energy Meteorological Coordinating Council visit in 2015 that recommended an evaluation of any biases in the wind data introduced by the tower and boom alignment at all meteorology towers.

Additional Studies on Clothing Treatments for Personal Protection against Biting Flies

DTIC Science & Technology

1979-09-01

length Jackets with attached hoods, the separate hoods were made of mesh fabric consisting of polyester filaments that give some abrasion resistance and...conditions was carried out using a sling psychrometer and anemometer to give data on dry-bulb temperature, relative humidity and wind speed. Insect specimens...treated the experimental items. Mrs. J. Whalen made the Jackets and hoods. UNCLASSIFIED

Analysis of inadvertent microprocessor lag time on eddy covariance results

Treesearch

Karl Zeller; Gary Zimmerman; Ted Hehn; Evgeny Donev; Diane Denny; Jeff Welker

2001-01-01

Researchers using the eddy covariance approach to measuring trace gas fluxes are often hoping to measure carbon dioxide and energy fluxes for ecosystem intercomparisons. This paper demonstrates a systematic microprocessor- caused lag of 20.1 to 20.2 s in a commercial sonic anemometer-analog-to-digital datapacker system operated at 10 Hz. The result of the inadvertent...

Atmospheric stability analysis over statically and dynamically rough surfaces

NASA Astrophysics Data System (ADS)

Maric, Emina; Metzger, Meredith; Singha, Arindam; Sadr, Reza

2011-11-01

The ratio of buoyancy flux to turbulent kinetic energy production in the atmospheric surface layer is investigated experimentally for air flow over two types of surfaces characterized by static and dynamic roughness. In this study, ``static'' refers to the time-invariant nature of naturally-occurring roughness over a mud/salt playa; while, ``dynamic'' refers to the behavior of water waves along an air-water interface. In both cases, time-resolved measurements of the momentum and heat fluxes were acquired from synchronized 3D sonic anemometers mounted on a vertical tower. Field campaigns were conducted at two sites, representing the ``statically'' and ``dynamically'' rough surfaces, respectively: (1) the SLTEST facility in Utah's western desert, and (2) the new Doha airport in Qatar under construction along the coast of the Persian Gulf. Note, at site 2, anemometers were located directly above the water by extension from a tower secured to the end of a 1 km-long pier. Comparisons of the Monin-Obukhov length, flux Richardson number, and gradient Richardson number are presented, and discussed in the context of the observed evolution of the turbulent spectra in response to diurnal variations of atmospheric stability. Supported by the Qatar National Research Fund.

Laser anemometer measurements and computations in an annular cascade of high turning core turbine vanes

NASA Technical Reports Server (NTRS)

Goldman, Louis J.; Seasholtz, Richard G.

1992-01-01

An advanced laser anemometer (LA) was used to measure the axial and tangential velocity components in an annular cascade of turbine stator vanes designed for a high bypass ratio engine. These vanes were based on a redesign of the first-stage stator, of a two-stage turbine, that produced 75 degrees of flow turning. Tests were conducted on a 0.771 scale model of the engine size stator. The advanced LA fringe system was designed to employ thinner than usual laser beams resulting in a 50-micron-diameter probe volume. Window correction optics were used to ensure that the laser beams did not uncross in passing through the curved optical access port. Experimental LA measurements of velocity and turbulence were obtained both upstream, within, and downstream of the stator vane row at the design exit critical velocity ratio of 0.896 at the hub. Static pressures were also measured on the vane surface. The measurements are compared, where possible with calculations from a 3-D inviscid flow analysis. The data are presented in both graphic and tabulated form so that they may be readily used to compare against other turbomachinery computations.

Statistical and wavelet analysis of the ATTO experiment in Amazonia rainforest

NASA Astrophysics Data System (ADS)

Bolzan, Mauricio

The study of the turbulence over a roughness surface is the most important subject in exchange of the gases between surface and atmosphere. This fact turns most important over surfaces like the Amazonia rainforest due its importance on local and regional climate. The Amazon Tall Tower Observatory - ATTO started its in February, 2012, with 10 dimensional ultrasonic anemometers bi and tri, in an 80 m tower of height. These anemometers were positioned in 78 m; 70 m; 62 m; 41 m; 57 m; 50 m; 45 m; 36 m; 30 m and 23 m of height and collected data were sampled at 1 Hz, 4 Hz and 10 Hz. The quadrant analysis and Wavelet transform were used to study the behavior of the Coherent Structure (CSs) over the Amazonia forest canopy in different atmospheric stability conditions. The results showed a fairly unique feature of the vertical wind profile near and below the inflection point. According to observations, the geometry of the canopy and terrain contributed to main influences for this aerodynamic effect of wind profile, as well as for the formation of coherent structures like "rolls" on the forest canopy in ATTO-CLAIRE site.

Reviews Book: Voyage to the Heart of the Matter: The ATLAS Experiment at CERN Equipment: SEP Spectroscope Books: Quantum Gods / The Universe Places to visit: The Royal Institution of Great Britain Book: What is this Thing Called Science? Book: Don't be Such a Scientist: Talking Substance in the Age of Style Equipment: La Crosse Anemometer Book: Wonder and Delight Web Watch

NASA Astrophysics Data System (ADS)

2010-05-01

WE RECOMMEND SEP Spectroscope Flatpacked classroom equipment for pupils aged 10 and over Quantum Gods Book attacks spiritualism and religion with physics The Universe Study of whether physics alone can explain origin of universe La Crosse Anemometer Handheld monitor is packed with useful features Wonder and Delight Essays in science education in honour of Eric Rogers WORTH A LOOK Voyage to the Heart of the Matter: The ATLAS Experiment at CERN Pop-up book explains background to complex physics The Royal Institution of Great Britain RI museum proves interesting but not ideal for teaching What is this Thing Called Science? Theory and history of science in an opinionated study Don't be Such a Scientist: Talking Substance in the Age of Style Explanation of how science is best communicated to the public WEB WATCH Particle physics simulations vary in complexity, usefulness and how well they work

Eddy-correlation measurements of fluxes of CO 2 and H 2O above a spruce stand

NASA Astrophysics Data System (ADS)

Ibrom, A.; Schütz, C.; Tworek, T.; Morgenstern, K.; Oltchev, A.; Falk, M.; Constantin, J.; Gravenhorst, G.

1996-12-01

Atmospheric fluxes of CO 2 and H 2O above a mature spruce stand ( Picea abies (L.) Karst.) have been investigated using the eddy- correlation technique. A closed path sensor adapted to the special requirements of long-term studies has been developed and tested. Field measurements have been performed since April 1995. Estimates of fetch showed a very narrow source area dimension under instable stratification (≤ 200 m). Fetch requirements at night are not met in some directions. Energy balance closure was influenced systematically by the wind direction indicating a substantial attenuation of the vertical wind motion by the tower (up to 40 %). Even for optimal flow directions, energy balance closure was about 88%. Intercomparison of the used ultra sonic anemometer (USAT-3) with a GILL - anemometer showed systematically lower values of vertical wind speed fluctuations (13 %). Average CO 2-fluxes ranged between -13 at noon to 3 μ mol m-2, s-1 at night in summer. In November and December the stand released CO 2 on a daily basis. A preliminary estimate of the cumulative net carbon balance over the observed period of 9 months is 4-5 t, Cha-1.

Some experiments in swirling flows: Detailed velocity measurements of a vortex breakdown using a laser Doppler anemometer. Ph.D. Thesis - Cornell Univ. Final Report

NASA Technical Reports Server (NTRS)

Faler, J. H.

1976-01-01

The results of an experimental study of spiraling flows in a slightly diverging, circular duct are reported. Seven types of flow disturbances were observed. In addition to the spiral and axisymmetric vortex breakdowns and the double helix mode, four other forms were identified and are reported. The type and axial location of the disturbance depended on the Reynolds and circulation numbers of the flow. Detailed velocity measurements were made by using a laser Doppler anemometer. Measurements made far upstream of any disturbance showed that the introduction of swirl resulted in the formation of a high axial velocity jet centered around the vortex center. A mapping of the velocity field of a so-called axisymmetric breakdown, formed at a Reynolds number of 2560, revealed that the recirculation zone is a two-celled structure, with four stagnation points on the vortex axis marking the axial extremes of the concentric cells. The dominant feature of the flow inside the bubble was the strong, periodic velocity fluctuations. Existing theoretical models do not predict the two-celled structure and the temporal velocity fluctuations that were observed.

Development of a New Methodology for Computing Surface Sensible Heat Fluxes using Thermal Imagery

NASA Astrophysics Data System (ADS)

Morrison, T. J.; Calaf, M.; Fernando, H. J.; Price, T. A.; Pardyjak, E.

2017-12-01

Current numerical weather predication models utilize similarity to characterize momentum, moisture, and heat fluxes. Such formulations are only valid under the ideal assumptions of spatial homogeneity, statistical stationary, and zero subsidence. However, recent surface temperature measurements from the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) Program on the Salt Flats of Utah's West desert, show that even under the most a priori ideal conditions, heterogeneity of the aforementioned variables exists. We present a new method to extract spatially-distributed measurements of surface sensible heat flux from thermal imagery. The approach consists of using a surface energy budget, where the ground heat flux is easily computed from limited measurements using a force-restore-type methodology, the latent heat fluxes are neglected, and the energy storage is computed using a lumped capacitance model. Preliminary validation of the method is presented using experimental data acquired from a nearby sonic anemometer during the MATERHORN campaign. Additional evaluation is required to confirm the method's validity. Further decomposition analysis of on-site instrumentation (thermal camera, cold-hotwire probes, and sonic anemometers) using Proper Orthogonal Decomposition (POD), and wavelet analysis, reveals time scale similarity between the flow and surface fluctuations.

Free-flow variability on the Jess and Souza Ranches, Altamont Pass. [Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nierenberg, R.

1988-04-25

A central monitoring computer was installed on each ranch. The computers were connected by communication cables to 50 turbines on the Souza Ranch and 150 turbines on the Jess Ranch. Anemometers were installed on every other turbine on 12-foot booms at 35 feet above ground level (AGL). Spacing between anemometers was approximately 200 feet in the crosswind direction by 500 feet in the parallel direction. A total of 23 turbines on the Souza Ranch was instrumented in this fashion, as well as two multi-level meteorological towers. On the Jess Ranch, 77 turbines were instrumented; about half at 35 feet AGLmore » and half at 50 feet AGL, plus four additional towers. Wind data were collected for approximately a 100 hour period on each ranch. All turbines were shut down during these periods so that no turbine wakes would be present. The data periods were selected by the meteorologist to insure that they occurred during typical spring-summer flow regimes. The terrain features upwind of the site appear to play as significant a role in the flow variability as terrain features within the site.« less

Free-flow variability on the Jess and Souza Ranches, Altamont Pass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nierenberg, R.

1988-04-25

A central monitoring computer was installed on each ranch. The computers were connected by communication cables to 50 turbines on the Souza Ranch and 150 turbines on the Jess Ranch. Anemometers were installed on every other turbine on 12-foot booms at 35 feet above ground level (AGL). Spacing between anemometers was approximately 200 feet in the crosswind direction by 500 feet in the parallel direction. A total of 23 turbines on the Souza Ranch was instrumented in this fashion, as well as two multi-level meteorological towers. On the Jess Ranch, 77 turbines were instrumented; about half at 35 feet AGLmore » and half at 50 feet AGL, plus four additional towers. Wind data were collected for approximately a 100 hour period on each ranch. All turbines were shut down during these periods so that no turbine wakes would be present. The data periods were selected by the meteorologist to insure that they occurred during typical spring-summer flow regimes. The terrain features upwind of the site appear to play as significant a role in the flow variability as terrain features within the site.« less

Characterizing the Turbulent Wind Flow Near a Wind Barrier Using a Data Set Collected with an Array of Sonic Anemometers

DTIC Science & Technology

2009-05-01

2009 Approved for public release; distribution unlimited. NOTICES...Approved for public release; distribution unlimited. ii REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188 Public reporting burden...D’Arcy, Scott Elliott, Thomas Truong, and Michael Davalos 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) U.S. Army

Winnebago Resource Study. Cooperative Research and Development Final Report, CRADA Number CRD-09-329

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jimenez, A.; Robichaud, R.

2015-03-01

Since 2005 the NREL Native American Tall Tower Loan program has assisted Native American tribes to assess their wind resource by lending tall (30m - 50m) anemometer. This program has allowed tribes a lower risk way to gather financeable wind data for potential utility scale wind energy projects. These projects offer Tribes a significant economic development opportunity.

REMOTE RECORDING ANNULAR VANE ASSEMBLY

DOEpatents

Wehmann, G.

1963-06-25

A weather vane apparatus is described which is capable of movement in horizontal and vertical planes. Associated with the vane are tangent potentiometers, commutators, and other electrical apparatus for deriving electrical output voltages as a function of the wind direction. The apparatus is particularly adapted for use with an anemometer to provide an electrical output indicating the amount and direction of an up or down draft. (AEC)

A Novel Low-Power-Consumption All-Fiber-Optic Anemometer with Simple System Design.

PubMed

Zhang, Yang; Wang, Fang; Duan, Zhihui; Liu, Zexu; Liu, Zigeng; Wu, Zhenlin; Gu, Yiying; Sun, Changsen; Peng, Wei

2017-09-14

A compact and low-power consuming fiber-optic anemometer based on single-walled carbon nanotubes (SWCNTs) coated tilted fiber Bragg grating (TFBG) is presented. TFBG as a near infrared in-fiber sensing element is able to excite a number of cladding modes and radiation modes in the fiber and effectively couple light in the core to interact with the fiber surrounding mediums. It is an ideal in-fiber device used in a fiber hot-wire anemometer (HWA) as both coupling and sensing elements to simplify the sensing head structure. The fabricated TFBG was immobilized with an SWCNT film on the fiber surface. SWCNTs, a kind of innovative nanomaterial, were utilized as light-heat conversion medium instead of traditional metallic materials, due to its excellent infrared light absorption ability and competitive thermal conductivity. When the SWCNT film strongly absorbs the light in the fiber, the sensor head can be heated and form a "hot wire". As the sensor is put into wind field, the wind will take away the heat on the sensor resulting in a temperature variation that is then accurately measured by the TFBG. Benefited from the high coupling and absorption efficiency, the heating and sensing light source was shared with only one broadband light source (BBS) without any extra pumping laser complicating the system. This not only significantly reduces power consumption, but also simplifies the whole sensing system with lower cost. In experiments, the key parameters of the sensor, such as the film thickness and the inherent angle of the TFBG, were fully investigated. It was demonstrated that, under a very low BBS input power of 9.87 mW, a 0.100 nm wavelength response can still be detected as the wind speed changed from 0 to 2 m/s. In addition, the sensitivity was found to be -0.0346 nm/(m/s) under the wind speed of 1 m/s. The proposed simple and low-power-consumption wind speed sensing system exhibits promising potential for future long-term remote monitoring and on-chip sensing in practical applications.

Calibration, Data Acquisition, and Post Analysis of Turbulent Fluid Flow in a Calibration Jet Using Hot-wire Anemometry

NASA Technical Reports Server (NTRS)

Moreno, Michelle

2004-01-01

The Turbine Branch concentrates on the following areas: Computational Fluid Dynamics (CFD), and implementing experimental procedures to obtain physical modeling data. Hot-wire Anemometry is a valuable tool for obtaining physical modeling data. Hot-wire Anemometry is likely to remain the principal research tool for most turbulent air/gas flow studies. The Hot-wire anemometer consists of a fine wire heated by electric current. When placed in a fluid stream, the hot-wire loses heat to the fluid by forced convection. In forced convection, energy transfer is due to molecular motion imposed by an extraneous force moving fluid parcels. When the hot-wire is in "equilibrium", the rate of heat input to the wire is equal to the rate of heat loss at the wire ends. The equality between heat input and heat loss is the basis for King s equation, which relates the electrical parameters of the hot-wire to the flow parameters of the fluid. Hot-wire anemometry is based on convective heat transfer from a heated wire element placed in a fluid flow. Any change in the fluid flow condition that affects the heat transfer from the heated element will be detected virtually instantaneously by a constant-temperature Hot-wire anemometry system. The system implemented for this research is the IFA 300. The system is a fully-integrated, thermal anemometer-based system that measures mean and fluctuating velocity components in air, water, and other fluids. It also measures turbulence and makes localized temperature measurements. A constant-temperature anemometer is a bridge and amplifier circuit that controls a tiny wire at constant temperature. As a fluid flow passes over the heated sensor, the amplifier senses the bridge off-balance and adjusts the voltage to the top of the bridge, keeping the bridge in balance. The voltage on top of the bridge can then be related to the velocity of the flow. The bridge voltage is sensitive to temperature as well as velocity and so the built-in thermocouple circuit can be attached to a thermocouple that can measure the fluid temperature. Additional information is included in the original extended abstract.

Effect of the Continuous Traverse Trajectory and Dynamic Error of the Vane Anemometer on the Accuracy of Average Velocity Measurements at the Cross-Section of the Mine Heading - Model-Based Testing

NASA Astrophysics Data System (ADS)

Jamróz, Paweł

2014-12-01

This paper discusses the problem of measuring the average velocity at the cross-section of mine heading with the use of the continuous traverse method. Based on model testing, it has been shown that measurement signals, obtained along the traversing trajectory, belong to the group of non-stationary signals. The methodology of the traversing method measurements, with the aspect of capabilities of measuring instruments used for that purpose, has been analysed. Results of simulation tests concerning the dynamic response of a vane anemometer to the measurement signal for selected trajectories of the continuous traverse have been presented. For this purpose, a velocity profile presenting an expanded stream of undisturbed air flow in the excavation has been used. Attention has been paid to the problem of selecting an adequate trajectory of anemometer movement, as the value of the velocity measured at the cross-section depends on the trajectory W artykule poruszono problem pomiarów prędkości średniej w przekroju wyrobiska kopalnianego z wykorzystaniem metody trawersu ciągłego. Na podstawie badań modelowych wykazano, że sygnały pomiarowe, które uzyskuje się wzdłuż trajektorii trawersowania należą do grupy sygnałów niestacjonarnych. Przeanalizowano metodologię przeprowadzania pomiarów metodą trawersowania w aspekcie możliwości pomiarowych wykorzystywanych w tym celu urządzeń pomiarowych. Przedstawiono wyniki badań symulacyjnych dynamicznej odpowiedzi anemometru skrzydełkowego na sygnał pomiarowy dla wybranych trajektorii trawersu ciągłego. W tym celu wykorzystano profil prędkości przedstawiający rozwiniętą strugę niezakłóconego przepływu powietrza w chodniku. Zwrócono uwagę na problem doboru odpowiedniej trajektorii przemieszczania anemometru, od której zależy wartość mierzonej prędkości średniej w przekroju.

Terrain forcing and thermal winds in a mountain pass

NASA Astrophysics Data System (ADS)

Clifton, A.; Daniels, M. H.; Lehning, M.

2010-12-01

As the European wind market matures, energy prospectors are increasingly looking to more challenging terrain and conditions, for example those found in the mountains and passes of the Alps. These locations present very different technical challenges to those found in the flatter plains of Northern Europe, the US midwest or offshore. There is little public data available on wind regimes in these areas, and what information there is is not often examined in conjunction with other data for the same area. Consequently it is difficult to estimate the effect of terrain or surface cover on the wind resource. We present selected data collected in a mountain pass during the winter of 2009 / 2010. Data were collected on site at 36, 54 and 77m above ground using sonic anemometers, and at the surface using small portable weather stations. Preliminary analysis of data from the sonic anemometers shows that flow in the pass is often low shear compared to an unconstrained boundary layer, although the log law using mean velocities does fit around half of the data that was collected. However, the applicability of the log law is questionable as calculated roughness lengths are of a similar order of magnitude to the measurement height. Further analysis of the sonic anemometer data does not suggest an equilibrium flux layer. Flow is generally along the major axis of the pass, indicating that the terrain acted to channel flow, compared to synoptic conditions. Larger-scale data from numerical weather prediction models is also available. These data are analysed in conjunction with simulations using the regional weather prediction model, ARPS, to show both the impact of terrain and surface heat fluxes on the wind profiles at different points in the pass. We use our data and results to show the potential effects on flow characteristics at typical wind turbine disk heights in the pass. We also suggest how future wind resource measurement and modeling campaigns in similar locations might be modified to help identify thermal and terrain effects on the wind resources.

A comparison of calibration techniques for hot-wires operated in subsonic compressible slip flows

NASA Technical Reports Server (NTRS)

Jones, Gregory S.; Stainback, P. C.; Nagabushana, K. A.

1992-01-01

This paper focuses on the correlation of constant temperature anemometer voltages to velocity, density, and total temperature in the transonic slip flow regime. Three different calibration schemes were evaluated. The ultimate use of these hot-wire calibrations is to obtain fluctuations in the flow variables. Without the appropriate mean flow sensitivities of the heated wire, the measurements of these fluctuations cannot be accurately determined.

Technical Training on High-Order Spectral Analysis and Thermal Anemometry Applications

NASA Technical Reports Server (NTRS)

Maslov, A. A.; Shiplyuk, A. N.; Sidirenko, A. A.; Bountin, D. A.

2003-01-01

The topics of thermal anemometry and high-order spectral analyses were the subject of the technical training. Specifically, the objective of the technical training was to study: (i) the recently introduced constant voltage anemometer (CVA) for high-speed boundary layer; and (ii) newly developed high-order spectral analysis techniques (HOSA). Both CVA and HOSA are relevant tools for studies of boundary layer transition and stability.

Curriculum Package: Junior High - Middle School Science Lessons. [A Visit to the Louisville, Kentucky Airports: Standiford and Bowman Fields.

ERIC Educational Resources Information Center

Squires, Frances H.

This science curriculum was written for teachers of children in junior high or middle school. It contains science activities for the following lessons: (1) Anemometers and Wind Speed; (2) Up! Up! and Away; (3) Jet Lag--Time Zones; (4) Inventors; (5) Model Rocketry; (6) Geometry and Kites; and (7) Super Savers. In lesson one, students construct an…

Note: Improving long-term stability of hot-wire anemometer sensors by means of annealing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lundström, H., E-mail: hans.lundstrom@hig.se

2015-08-15

Annealing procedures for hot-wire sensors of platinum and platinum-plated tungsten have been investigated experimentally. It was discovered that the two investigated sensor metals behave quite differently during the annealing process, but for both types annealing may improve long-term stability considerably. Measured drift of sensors both without and with prior annealing is presented. Suggestions for suitable annealing temperatures and times are given.

JPRS Report, Science & Technology, USSR: Electronics & Electrical Engineering.

DTIC Science & Technology

1988-12-14

of Angle Measurement on Orientation of Porro Prism in Interferometer [G. A. Lenkova; AVTOMETRIYA, No 2, Mar-Apr 88] 33 Laser-Doppler Anemometer With...Measurement on Orientation of Porro Prism in Interferometer 18600122e Novosibirsk A VTOMETRIYA in Russian No 2, Mar-Apr 88 (manuscript received 19...identical Porro prisms being mounted rigidly on a common support and sym- metrically with respect to the axis of rotation. The range of measurable

Evaluation of a Tethered Kite Anemometer.

DTIC Science & Technology

1981-02-01

Solar Eclipse , Part I - Atmospheric Sciences Laboratory Field Program Summary," ASL-TR-0059, May 1980 131. Miller, Walter B., "User’s Guide for Passive...the smaller kite and 500 m with the larger version. Therefore, the kite has been evaluated with reference to methods of obtaining winds to equivalent...advantage over remote sensors where noise can be mistakenly identified as signal , and complex mathematical algorithms are often required to obtain

Three dimensional laser Doppler velocimeter turbulence measurements in a pipe flow

NASA Technical Reports Server (NTRS)

Fuller, C. E., III; Cliff, W. C.; Huffaker, R. M.

1973-01-01

The mean and turbulent u, v, and w components of a gaseous fully developed turbulent pipe flow were measured with a laser Doppler velocimeter system. Measurements of important system parameters are presented and discussed in relation to the measurement accuracy. Simultaneous comparisons of the laser Doppler and hot wire anemometer measurements in the turbulent flow provided evidence that the two systems were responding to the same flow phenomena.

The 1991 LLWAS anemometer test program

NASA Astrophysics Data System (ADS)

Phillips, Charles O.; Burnham, David; Jacobs, Leo; Hazen, David

1992-09-01

Performance tests of anemometers under icing and snow conditions were conducted during 1990-1991 on the test field at Rochester, MN and in icing chambers and wind tunnels at Sterling, VA. These tests were done for the FAA Low Level Windshear Alert System (LLWAS) program to test sensors for the next phase of LLWAS. Sensors from ten manufacturers were accepted into the test program from the respondents to the Commerce Business Daily. These sensors were required first to pass an icing chamber test in order to be field tested. The field tests lasted from Nov. 1990 to Jul. 1991. Afterwards, all sensors were sent to Sterling, VA for wind tunnel tests in September 1991. All units from the eight manufacturers that passed the icing chamber test were in the field test. A propeller/vane sensor that failed the icing chamber test was put in the field as a reference. All the units that passed were not affected by icing during the field test although a mechanical unit was affected by snow during one event. The propeller/vane was affected by icing during one event. Wind tunnel tests were done to check starting thresholds and calibration anomalies found in the field. It was concluded that there is no one winning technology that could be found from the tests.

The Temporal Resolution of Laser Induced Fluorescence Photobleaching Anemometer

NASA Astrophysics Data System (ADS)

Zhao, Wei; Yang, Fang; Wang, Guiren

2014-11-01

Recently, in microfluidics, electrokinetic flows are widely used on micromixer designing. However, there is unfortunately no valid velocimeter today that can measure the random velocity fluctuation at high temporal and spatial resolution simultaneously in the complicated flow circumstance. We recently introduced laser induced fluorescence photobleaching anemometer (LIFPA), which has been successfully used in the measurement of velocity field in AC electrically driven microflow. Here, we theoretically study the temporal resolution (TR) of and experimentally verify, LIFPA can have simultaneously ultrahigh temporal (~4 μs) and spatial (~203 nm) resolution and can measure velocity fluctuation up to at least 2 kHz, whose corresponding wave number is about 6 × 106 1/m in an electrokinetically forced unsteady flow in microfluidics. The measurement of LIFPA is also compared with the widely used micro Particle Imaging Velocimetry (μPIV). We found, at the inlet, due to multiple uncertainties, the velocity fluctuations by μPIV exhibits apparently smaller values than that by LIFPA. But at downstreams, where velocity fluctuation is much lower than at the inlet and the uncertainties of complicated electric field on particles becomes smaller, LIFPA and μPIV indicate similar measurement. The work was supported by NSF under grant no. CAREER CBET-0954977 and MRI CBET-1040227, respectively.

Validation of a CFD Model by Using 3D Sonic Anemometers to Analyse the Air Velocity Generated by an Air-Assisted Sprayer Equipped with Two Axial Fans

PubMed Central

García-Ramos, F. Javier; Malón, Hugo; Aguirre, A. Javier; Boné, Antonio; Puyuelo, Javier; Vidal, Mariano

2015-01-01

A computational fluid dynamics (CFD) model of the air flow generated by an air-assisted sprayer equipped with two axial fans was developed and validated by practical experiments in the laboratory. The CFD model was developed by considering the total air flow supplied by the sprayer fan to be the main parameter, rather than the outlet air velocity. The model was developed for three air flows corresponding to three fan blade settings and assuming that the sprayer is stationary. Actual measurements of the air velocity near the sprayer were taken using 3D sonic anemometers. The workspace sprayer was divided into three sections, and the air velocity was measured in each section on both sides of the machine at a horizontal distance of 1.5, 2.5, and 3.5 m from the machine, and at heights of 1, 2, 3, and 4 m above the ground The coefficient of determination (R2) between the simulated and measured values was 0.859, which demonstrates a good correlation between the simulated and measured data. Considering the overall data, the air velocity values produced by the CFD model were not significantly different from the measured values. PMID:25621611

Improved observations of turbulence dissipation rates from wind profiling radars

DOE PAGES

McCaffrey, Katherine; Bianco, Laura; Wilczak, James M.

2017-07-20

Observations of turbulence dissipation rates in the planetary boundary layer are crucial for validation of parameterizations in numerical weather prediction models. However, because dissipation rates are difficult to obtain, they are infrequently measured through the depth of the boundary layer. For this reason, demonstrating the ability of commonly used wind profiling radars (WPRs) to estimate this quantity would be greatly beneficial. During the XPIA field campaign at the Boulder Atmospheric Observatory, two WPRs operated in an optimized configuration, using high spectral resolution for increased accuracy of Doppler spectral width, specifically chosen to estimate turbulence from a vertically pointing beam. Multiplemore » post-processing techniques, including different numbers of spectral averages and peak processing algorithms for calculating spectral moments, were evaluated to determine the most accurate procedures for estimating turbulence dissipation rates using the information contained in the Doppler spectral width, using sonic anemometers mounted on a 300 m tower for validation. Furthermore, the optimal settings were determined, producing a low bias, which was later corrected. Resulting estimations of turbulence dissipation rates correlated well ( R 2 = 0.54 and 0.41) with the sonic anemometers, and profiles up to 2 km from the 449 MHz WPR and 1 km from the 915 MHz WPR were observed.« less

Improved observations of turbulence dissipation rates from wind profiling radars

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCaffrey, Katherine; Bianco, Laura; Wilczak, James M.

Observations of turbulence dissipation rates in the planetary boundary layer are crucial for validation of parameterizations in numerical weather prediction models. However, because dissipation rates are difficult to obtain, they are infrequently measured through the depth of the boundary layer. For this reason, demonstrating the ability of commonly used wind profiling radars (WPRs) to estimate this quantity would be greatly beneficial. During the XPIA field campaign at the Boulder Atmospheric Observatory, two WPRs operated in an optimized configuration, using high spectral resolution for increased accuracy of Doppler spectral width, specifically chosen to estimate turbulence from a vertically pointing beam. Multiplemore » post-processing techniques, including different numbers of spectral averages and peak processing algorithms for calculating spectral moments, were evaluated to determine the most accurate procedures for estimating turbulence dissipation rates using the information contained in the Doppler spectral width, using sonic anemometers mounted on a 300 m tower for validation. Furthermore, the optimal settings were determined, producing a low bias, which was later corrected. Resulting estimations of turbulence dissipation rates correlated well ( R 2 = 0.54 and 0.41) with the sonic anemometers, and profiles up to 2 km from the 449 MHz WPR and 1 km from the 915 MHz WPR were observed.« less

Hot-Film and Hot-Wire Anemometry for a Boundary Layer Active Flow Control Test

NASA Technical Reports Server (NTRS)

Lenahan, Keven C.; Schatzman, David M.; Wilson, Jacob Samuel

2013-01-01

Unsteady active flow control (AFC) has been used experimentally for many years to minimize bluff-body drag. This technology could significantly improve performance of rotorcraft by cleaning up flow separation. It is important, then, that new actuator technologies be studied for application to future vehicles. A boundary layer wind tunnel was constructed with a 1ft-x-3ft test section and unsteady measurement instrumentation to study how AFC manipulates the boundary layer to overcome adverse pressure gradients and flow separation. This unsteady flow control research requires unsteady measurement methods. In order to measure the boundary layer characteristics, both hot-wire and hot-film Constant Temperature Anemometry is used. A hot-wire probe is mounted in the flow to measure velocity while a hot-film array lays on the test surface to measure skin friction. Hot-film sensors are connected to an anemometer, a Wheatstone bridge circuit with an output that corresponds to the dynamic flow response. From this output, the time varying flow field, turbulence, and flow reversal can be characterized. Tuning the anemometers requires a fan test on the hot-film sensors to adjust each output. This is a delicate process as several variables drastically affect the data, including control resistance, signal input, trim, and gain settings.

Validation of a CFD model by using 3D sonic anemometers to analyse the air velocity generated by an air-assisted sprayer equipped with two axial fans.

PubMed

García-Ramos, F Javier; Malón, Hugo; Aguirre, A Javier; Boné, Antonio; Puyuelo, Javier; Vidal, Mariano

2015-01-22

A computational fluid dynamics (CFD) model of the air flow generated by an air-assisted sprayer equipped with two axial fans was developed and validated by practical experiments in the laboratory. The CFD model was developed by considering the total air flow supplied by the sprayer fan to be the main parameter, rather than the outlet air velocity. The model was developed for three air flows corresponding to three fan blade settings and assuming that the sprayer is stationary. Actual measurements of the air velocity near the sprayer were taken using 3D sonic anemometers. The workspace sprayer was divided into three sections, and the air velocity was measured in each section on both sides of the machine at a horizontal distance of 1.5, 2.5, and 3.5 m from the machine, and at heights of 1, 2, 3, and 4 m above the ground The coefficient of determination (R2) between the simulated and measured values was 0.859, which demonstrates a good correlation between the simulated and measured data. Considering the overall data, the air velocity values produced by the CFD model were not significantly different from the measured values.

Structure of the nocturnal boundary layer over a complex terrain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parker, M.J.; Raman, S.

The complex nature of the nocturnal boundary layer (NBL) has been shown extensively in the literature Project STABLE was conducted in 1988 to study NBL turbulence and diffusion over the complex terrain of the Savannah River Site (SRS) near Augusta, Georgia. The third night of the study was particularly interesting because of the unusual phenomena observed in the structure of the NBL. Further analyses of microscale and mesoscale data from this night are presented using data from SRS network of eight 61 m towers over 900 km{sup 2}, from six launches of an instrumented tethersonde, from permanent SRL meteorological instrumentationmore » at seven levels of the 304 m (1,000 ft) WJBF-TV tower near SRS, and additional data collected at 36 m (CC) by North Carolina State University (NCSU) including a one dimensional sonic anemometer, fine wire thermocouple, and a three dimensional propeller anemometer. Also, data from the nearby Plant Vogtle nuclear power plant observation tower and the National Weather Service at Augusta`s Bush Field (AGS) are presented. The passage of a mesoscale phenomenon, defined as a microfront (with an explanation of the nomenclature used), and a vertical composite schematic of the NBL which shows dual low level wind maxima, dual inversions, and a persistent, elevated turbulent layer over a complex terrain are described.« less

Structure of the nocturnal boundary layer over a complex terrain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parker, M.J.; Raman, S.

The complex nature of the nocturnal boundary layer (NBL) has been shown extensively in the literature Project STABLE was conducted in 1988 to study NBL turbulence and diffusion over the complex terrain of the Savannah River Site (SRS) near Augusta, Georgia. The third night of the study was particularly interesting because of the unusual phenomena observed in the structure of the NBL. Further analyses of microscale and mesoscale data from this night are presented using data from SRS network of eight 61 m towers over 900 km{sup 2}, from six launches of an instrumented tethersonde, from permanent SRL meteorological instrumentationmore » at seven levels of the 304 m (1,000 ft) WJBF-TV tower near SRS, and additional data collected at 36 m (CC) by North Carolina State University (NCSU) including a one dimensional sonic anemometer, fine wire thermocouple, and a three dimensional propeller anemometer. Also, data from the nearby Plant Vogtle nuclear power plant observation tower and the National Weather Service at Augusta's Bush Field (AGS) are presented. The passage of a mesoscale phenomenon, defined as a microfront (with an explanation of the nomenclature used), and a vertical composite schematic of the NBL which shows dual low level wind maxima, dual inversions, and a persistent, elevated turbulent layer over a complex terrain are described.« less

Structure of the nocturnal boundary layer over a complex terrain

NASA Astrophysics Data System (ADS)

Parker, M. J.; Raman, S.

The complex nature of the nocturnal boundary layer (NBL) has been shown extensively in the literature Project STABLE was conducted in 1988 to study NBL turbulence and diffusion over the complex terrain of the Savannah River Site (SRS) near Augusta, Georgia. The third night of the study was particularly interesting because of the unusual phenomena observed in the structure of the NBL. Further analyses of microscale and mesoscale data from this night are presented using data from SRS network of eight 61 m towers over 900 sq km, from six launches of an instrumented tethersonde, from permanent SRL meteorological instrumentation at seven levels of the 304 m (1,000 ft) WJBF-TV tower near SRS, and additional data collected at 36 m (CC) by North Carolina State University (NCSU) including a one dimensional sonic anemometer, fine wire thermocouple, and a three dimensional propeller anemometer. Also, data from the nearby Plant Vogtle nuclear power plant observation tower and the National Weather Service at Augusta's Bush Field (AGS) are presented. The passage of a mesoscale phenomenon, defined as a microfront (with an explanation of the nomenclature used), and a vertical composite schematic of the NBL which shows dual low level wind maxima, dual inversions, and a persistent, elevated turbulent layer over a complex terrain are described.

Response of Ocean Circulation to Different Wind Forcing in Puerto Rico and US Virgin Islands

NASA Astrophysics Data System (ADS)

Solano, Miguel; Garcia, Edgardo; Leonardi, Stafano; Canals, Miguel; Capella, Jorge

2013-11-01

The response of the ocean circulation to various wind forcing products has been studied using the Regional Ocean Modeling System. The computational domain includes the main islands of Puerto Rico, Saint John and Saint Thomas, located on the continental shelf dividing the Caribbean Sea and the Atlantic Ocean. Data for wind forcing is provided by an anemometer located in a moored buoy, the Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS) model and the National Digital Forecast Database (NDFD). Hindcast simulations have been validated using hydrographic data at different locations in the area of study. Three cases are compared to quantify the impact of high resolution wind forcing on the ocean circulation and the vertical structure of salinity, temperature and velocity. In the first case a constant wind velocity field is used to force the model as measured by an anemometer on top of a buoy. In the second case, a forcing field provided by the Navy's COAMPS model is used and in the third case, winds are taken from NDFD in collaboration with the National Centers for Environmental Prediction. Validated results of ocean currents against data from Acoustic Doppler Current Profilers at different locations show better agreement using high resolution wind data as expected. Thanks to CariCOOS and NOAA.

An Examination of the Quality of Wind Observations with Smartphones

NASA Astrophysics Data System (ADS)

Hintz, Kasper; Vedel, Henrik; Muñoz-Gomez, Juan; Woetmann, Niels

2017-04-01

Over the last years, the number of devices connected to the internet has increased significantly making it possible for internal and external sensors to communicate via the internet, opening up many possibilities for additional data for use in the atmospheric sciences. Vaavud has manufactured small anemometer devices which can measure wind speed and wind direction when connected to a smartphone. This work examines the quality of such crowdsourced Handheld Wind Observations (HWO). In order to examine the quality of the HWO, multiple idealised measurement sessions were performed at different sites in different atmospheric conditions. In these sessions, a high-precision ultrasonic anemometer was installed to work as a reference measurement. The HWO are extrapolated to 10 m in order to compare these to the reference observations. This allows us to examine the effect of stability correction in the surface layer and the quality of height extrapolated HWO. The height extrapolation is done using the logarithmic wind profile law with and without stability correction. Furthermore, this study examines the optimal ways of using traditional observations and numerical models to validate HWO. In order to do so, a series of numerical reanalysis have been run for a period of 5 months to quantise the effect of including crowdsourced HWO in a traditional observation dataset.

Atmospheric Turbulence Estimates from a Pulsed Lidar

NASA Technical Reports Server (NTRS)

Pruis, Matthew J.; Delisi, Donald P.; Ahmad, Nash'at N.; Proctor, Fred H.

2013-01-01

Estimates of the eddy dissipation rate (EDR) were obtained from measurements made by a coherent pulsed lidar and compared with estimates from mesoscale model simulations and measurements from an in situ sonic anemometer at the Denver International Airport and with EDR estimates from the last observation time of the trailing vortex pair. The estimates of EDR from the lidar were obtained using two different methodologies. The two methodologies show consistent estimates of the vertical profiles. Comparison of EDR derived from the Weather Research and Forecast (WRF) mesoscale model with the in situ lidar estimates show good agreement during the daytime convective boundary layer, but the WRF simulations tend to overestimate EDR during the nighttime. The EDR estimates from a sonic anemometer located at 7.3 meters above ground level are approximately one order of magnitude greater than both the WRF and lidar estimates - which are from greater heights - during the daytime convective boundary layer and substantially greater during the nighttime stable boundary layer. The consistency of the EDR estimates from different methods suggests a reasonable ability to predict the temporal evolution of a spatially averaged vertical profile of EDR in an airport terminal area using a mesoscale model during the daytime convective boundary layer. In the stable nighttime boundary layer, there may be added value to EDR estimates provided by in situ lidar measurements.

Forced Internal Waves in the Arctic Ocean.

DTIC Science & Technology

1980-05-01

AND CONCLUSIONS. .. ................. 223 REFERENCES. .. ........................... 237 APPENDICES A. APS SENSOR CALIBRATION AND DATA PROCESSING...and the anemometer mast with sensors at 2 m and 4 m. 7 (1974a), McPhee (1974) and Smith (1978), was to be used to measure tur- bulent flow in the...boundary layer and to detect any velocity fluctua- tions that might occur in the upper pycnocline. Data from all sensors was to be fed to a NOVA 1200

Fiber-Optic Anemometer Based on Silicon Fabry-Perot Interferometer

DTIC Science & Technology

2015-11-05

finding vast applications in all kinds of industrial processes, such as process control, food quality surveillance, wind turbines , environment...stronger flow ( wind ), which induces a decrease in the optical path of the silicon FPI, which lead to blueshifts the output spectrum. A higher wind ...Experimental results demonstrate that a wavelength shift -0.574 nm was observed for a wind speed of 4 m/s. Better sensitivity is to be expected when

Reply to comment by Mauder on "How well can we measure the vertical wind speed? Implications for fluxes of energy and mass"

Treesearch

John Kochendorfer; Tilden P. Meyers; John M. Frank; William J. Massman; Mark W. Heuer

2013-01-01

In Kochendorfer et al. (Boundary-Layer Meteorol 145:383-398, 2012, hereafter K2012) the vertical wind speed (w) measured by a non-orthogonal three-dimensional sonic anemometer was shown to be underestimated by 12%. Turbulent statistics and eddycovariance fluxes estimated using w were also affected by this underestimate in w. Methodologies used in K2012 are clarified...

Near-wall turbulence alteration through thin streamwise riblets

NASA Technical Reports Server (NTRS)

Wilkinson, Stephen P.; Lazos, Barry S.

1987-01-01

The possibility of improving the level of drag reduction associated with near-wall riblets is considered. The methodology involves the use of a hot-wire anemometer to study various surface geometries on small, easily constructed models. These models consist of small, adjacent rectangular channels on the wall aligned in the streamwise direction. The VITA technique is modified and applied to thin-element-array and smooth flat-plate data and the results are indicated schematically.

True eddy accumulation and eddy covariance methods and instruments intercomparison for fluxes of CO2, CH4 and H2O above the Hainich Forest

NASA Astrophysics Data System (ADS)

Siebicke, Lukas

2017-04-01

The eddy covariance (EC) method is state-of-the-art in directly measuring vegetation-atmosphere exchange of CO2 and H2O at ecosystem scale. However, the EC method is currently limited to a small number of atmospheric tracers by the lack of suitable fast-response analyzers or poor signal-to-noise ratios. High resource and power demands may further restrict the number of spatial sampling points. True eddy accumulation (TEA) is an alternative method for direct and continuous flux observations. Key advantages are the applicability to a wider range of air constituents such as greenhouse gases, isotopes, volatile organic compounds and aerosols using slow-response analyzers. In contrast to relaxed eddy accumulation (REA), true eddy accumulation (Desjardins, 1977) has the advantage of being a direct method which does not require proxies. True Eddy Accumulation has the potential to overcome above mentioned limitations of eddy covariance but has hardly ever been successfully demonstrated in practice in the past. This study presents flux measurements using an innovative approach to true eddy accumulation by directly, continuously and automatically measuring trace gas fluxes using a flow-through system. We merge high-frequency flux contributions from TEA with low-frequency covariances from the same sensors. We show flux measurements of CO2, CH4 and H2O by TEA and EC above an old-growth forest at the ICOS flux tower site "Hainich" (DE-Hai). We compare and evaluate the performance of the two direct turbulent flux measurement methods eddy covariance and true eddy accumulation using side-by-side trace gas flux observations. We further compare performance of seven instrument complexes, i.e. combinations of sonic anemometers and trace gas analyzers. We compare gas analyzers types of open-path, enclosed-path and closed-path design. We further differentiate data from two gas analysis technologies: infrared gas analysis (IRGA) and laser spectrometry (open path and CRDS closed-path laser spectrometers). We present results of CO2 and H2O fluxes from the following six instruments, i.e. combinations of sonic anemometers/gas analyzers (and methods): METEK-uSonic3/Picarro-G2301 (TEA), METEK-uSonic3/LI-7500 (EC), Gill-R3/LI-6262 (EC), Gill-R3/LI-7200 (EC), Gill-HS/LI-7200 (EC), Gill-R3/LGR-FGGA (EC). Further, we present results of much more difficult to measure CH4 fluxes from the following three instruments, i.e. combinations of sonic anemometers/gas analyzers (and methods): METEK-uSonic3/Picarro-G2301 (TEA), Gill-R3/LI-7700 (EC), Gill-R3/LGR-FGGA (EC). We observed that CO2, CH4 and H2O fluxes from the side-by-side measurements by true eddy accumulation and eddy covariance methods correlated well. Secondly, the difference between the TEA and EC methods using the same sonic anemometer but different gas analyzer was often smaller than the mismatch of the various side-by-side eddy covariance measurements using different sonic anemometers and gas analyzers. Signal-to-noise ratios of CH4 fluxes from the true eddy accumulation system system were superior to both eddy covariance sensors (open-path LI-7700 and closed-path CRDS LGR-FGGA sensors). We conclude that our novel implementation of the true eddy accumulation method demonstrated high signal-to-noise ratios, applicability to slow-response gas analyzers, small power consumption and direct proxy-free ecosystem-scale trace gas flux measurements of CO2, CH4 and H2O. The current results suggest that true eddy accumulation would be suitable and should be applied as the method-of-choice for direct flux measurements of a large number of atmospheric constituents beyond CO2 and H2O, including isotopes, aerosols, volatile organic compounds and other trace gases for which eddy covariance might not be a viable alternative. We will further develop true eddy accumulation as a novel approach using multiplexed systems for spatially distributed flux measurements.

Three-Dimensional Venturi Sensor for Measuring Extreme Winds

NASA Technical Reports Server (NTRS)

Zysko, Jan A.; Perotti, Jose M.; Amis, Christopher; Randazzo, John; Blalock, Norman; Eckhoff, Anthony

2003-01-01

A three-dimensional (3D) Venturi sensor is being developed as a compact, rugged means of measuring wind vectors having magnitudes of as much as 300 mph (134 m/s). This sensor also incorporates auxiliary sensors for measuring temperature from -40 to +120 F (-40 to +49 C), relative humidity from 0 to 100 percent, and atmospheric pressure from 846 to 1,084 millibar (85 to 108 kPa). Conventional cup-and-vane anemometers are highly susceptible to damage by both high wind forces and debris, due to their moving parts and large profiles. In addition, they exhibit slow recovery times contributing to an inaccurately high average-speed reading. Ultrasonic and hot-wire anemometers overcome some of the disadvantages of the cup and-vane anemometers, but they have other disadvantageous features, including limited dynamic range and susceptibility to errors caused by external acoustic noise and rain. In contrast, the novel 3D Venturi sensor is less vulnerable to wind damage because of its smaller profile and ruggedness. Since the sensor has no moving parts, it provides increased reliability and lower maintenance costs. It has faster response and recovery times to changing wind conditions than traditional systems. In addition, it offers wide dynamic range and is expected to be relatively insensitive to rain and acoustic energy. The Venturi effect in this sensor is achieved by the mirrored double-inflection curve, which is then rotated 360 to create the desired detection surfaces. The curve is optimized to provide a good balance of pressure difference between sensor ports and overall maximum fluid velocity while in the shape. Four posts are used to separate the two shapes, and their size and location were chosen to minimize effects on the pressure measurements. The 3D Venturi sensor has smart software algorithms to map the wind pressure exerted on the surfaces of the design. Using Bernoulli's equation, the speed of the wind is calculated from the differences among the pressure readings at the various ports. The direction of the wind is calculated from the spatial distribution and magnitude of the pressure readings. All of the pressure port sizes and locations have been optimized to minimize measurement errors and to reside in areas demonstrating a stable pressure reading proportional to the velocity range.

Turbulent Flow and Sand Dune Dynamics: Identifying Controls on Aeolian Sediment Transport

NASA Astrophysics Data System (ADS)

Weaver, C. M.; Wiggs, G.

2007-12-01

Sediment transport models are founded on cubic power relationships between the transport rate and time averaged flow parameters. These models have achieved limited success and recent aeolian and fluvial research has focused on the modelling and measurement of sediment transport by temporally varying flow conditions. Studies have recognised turbulence as a driving force in sediment transport and have highlighted the importance of coherent flow structures in sediment transport systems. However, the exact mechanisms are still unclear. Furthermore, research in the fluvial environment has identified the significance of turbulent structures for bedform morphology and spacing. However, equivalent research in the aeolian domain is absent. This paper reports the findings of research carried out to characterise the importance of turbulent flow parameters in aeolian sediment transport and determine how turbulent energy and turbulent structures change in response to dune morphology. The relative importance of mean and turbulent wind parameters on aeolian sediment flux was examined in the Skeleton Coast, Namibia. Measurements of wind velocity (using sonic anemometers) and sand transport (using grain impact sensors) at a sampling frequency of 10 Hz were made across a flat surface and along transects on a 9 m high barchan dune. Mean wind parameters and mass sand flux were measured using cup anemometers and wedge-shaped sand traps respectively. Vertical profile data from the sonic anemometers were used to compute turbulence and turbulent stress (Reynolds stress; instantaneous horizontal and vertical fluctuations; coherent flow structures) and their relationship with respect to sand transport and evolving dune morphology. On the flat surface time-averaged parameters generally fail to characterise sand transport dynamics, particularly as the averaging interval is reduced. However, horizontal wind speed correlates well with sand transport even with short averaging times. Quadrant analysis revealed that turbulent events with a positive horizontal component, such as sweeps and outward interactions, were responsible for the majority of sand transport. On the dune surface results demonstrate the development and modification of turbulence and sediment flux in key regions: toe, crest and brink. Analysis suggests that these modifications are directly controlled by streamline curvature and flow acceleration. Conflicting models of dune development, morphology and stability arise when based upon either the dynamics of measured turbulent flow or mean flow.

1991 LLWAS Anemometer Test Program.

DTIC Science & Technology

1992-09-01

the enhanced LLWAS system installed there detected a violent microburst and prevented the loss of a Continental flight on final approach . Because of... balance of the heat provided by eight radiant heaters located on a one-foot diameter around the metal cup and vane assembly. HYDRO-TECH MODEL WS-3, WD...first chamber test, the Qualimetrics sensor had been modified with the addition of a 40- or 50-watt heater to the rain hood of the sensor. This heat

Determination of Momentum Flux Using a Bivane and Cup Anemometer

DTIC Science & Technology

1992-12-01

race. In many situations, these transfers have a direct impact on the statc of the atmosphere as well as on plant and animal life . One specific...explanatory. The middle region is the buoyancy subrange, where the slope approaches -2.0. A gap is usually detected after the buoyancy subrange...However, a delicate balance must be reached, as over- filtering distorts the slope in this region. 138 6.2.1. Horizontal Wind Component The power

A Design Procedure for Minimizing Propeller-Induced Vibration in Hull Structural Elements.

DTIC Science & Technology

1979-09-01

Propeller," 12th International Towing Tank Conference, Rome, 1969. 46. Van Manen , J. D., "The Effect of Cavitation on the Interaction Be- tween Propeller...The wake, when determined in absence of the propeller, is called the nominal wake field. Van Oossanen [8) points out that it is becoming...wire anemometer and the laser-Doppler anomometer. These are discussed briefly in a paper by van Gent and van Oossanen [11. 4. Estimate Longitudinal

PTC and Partner Products in the Creation of a Hurricane Wind Sensor

NASA Technical Reports Server (NTRS)

Randazzo, John; Voska, N. (Technical Monitor)

2002-01-01

This viewgraph presentation provides information on the development of a wind sensor for use during hurricanes. The objectives of this presentation are: (1) Educate the user unfamiliar with the modules as to what is available/lacking; (2) Share where some changes could be made; (3) Look at alternative approaches made possible by new releases/modules; (4) Use feedback to improve processes/approaches. The current pad wind sensors are cup-and-vane type anemometers.

Velocity Measurement Systems for a Low-speed Wind Tunnel

DTIC Science & Technology

2015-04-29

Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 wind tunnel PIV hot wire particle image velocimetry REPORT DOCUMENTATION PAGE 11. SPONSOR...Velocity Measurement Systems for a Low-speed Wind Tunnel Report Title Funds were provided by the ARO for the purchase of TSI hot- wire anemometer equipment...implemented. In the summer of 2011, the focus of the summer camp was on wind turbines , and for the last two summers, the STEM outreach camp has studied

Field Operational and Environmental Evaluation of the Automated Integrated Surveying Instrument (AISI). Volume 2

DTIC Science & Technology

1988-04-01

2M - sub go, or empNm, anl arn rftle a dm sIected rme 4( eserih (AM’ me (a s -el. Useful f(o work ia m Joh. wft um bemiauris. * EF az Q~, The guss...with calibrated eauior-er 3 Recorder Honeywell ENV 6047 D 4-20-87 10-20-87 Sand and Dust Recorder Leeds & Northrop E 6034 D 4-15-87 10-15-87 Anemometer

EURAMET project No. 1225: intercomparsion of very low air speed standard facilities (0.05 m/s to 1 m/s)

NASA Astrophysics Data System (ADS)

Pachinger, Dietmar; De Huu, Marc; Mueller, Harald; Care, Isabelle; Frederiksen, John; Piccato, Aline; Bertasiene, Agne

2017-01-01

For the first time a EURAMET comparison of standard facilities in the field of low air speed is presented. The air velocities range from 0.05 m/s up to 1 m/s. Two different thermal anemometers are used as Transfer Standards (TS), namely a ball-type and a planar-type anemometer. Due to their construction it is possible to analyze different components of the flow vector. Orientation-dependent measurements which are investigated in addition might also deliver information concerning the components of the flow vector. A Comparison Reference Value (CRV) is calculated with the help of the chi-squared test according to the procedure A presented by Cox [1] [2] and the degree of equivalence of the laboratory data to the CRV is determined. Both TS show reasonable results and a high degree of equivalence. Furthermore the degree of equivalence of the laboratory data to each other is investigated in detail. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

CCM.FF-K3.2011: Final report for the CIPM key comparison of air speed, 0.5 m/s to 40 m/s

NASA Astrophysics Data System (ADS)

Müller, Harald; Caré, Isabelle; Lucas, Peter; Pachinger, Dietmar; Kurihara, Noboru; Lishui, Cui; Su, Chun-Min; Shinder, Iosif; Spazzini, Pier Giorgio

2017-01-01

The CCM.FF-K3.2011 comparison was organized for the purpose of determination of the degree of equivalence of the national standards for air speed over the range 0.5 m/s to 40 m/s. An ultrasonic anemometer and a Laser Doppler anemometer were used as transfer standards. Nine laboratories from three RMOs participated between July 2013 and July 2015—EURAMET: PTB, Germany; LNE-CETIAT, France; INRIM, Italy; VSL, The Netherlands; E+E, Austria; SIM: NIST, USA; APMP: NMIJ/AIST, Japan; NIM, China; CMS/ITRI, Chinese Taipei. The measurements were provided at ambient conditions. All results of independent participants were used in the determination of the key comparison reference value (KCRV) and the uncertainty of the KCRV. The reference value was determined at each air speed separately following `procedure A' presented by M G Cox. The degree of equivalence with the KCRV was calculated for each air speed and laboratory. Almost all reported results were consistent with the KCRV. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Characterization of vertical aerosol flows by single particle mass spectrometry for micrometeorological analysis

NASA Astrophysics Data System (ADS)

Gelhausen, Elmar; Hinz, Klaus-Peter; Schmidt, Andres; Spengler, Bernhard

2011-10-01

A single particle mass spectrometer LAMPAS 2 (Laser Mass Analyzer for Particles in the Airborne State) was combined with an ultrasonic anemometer to provide a measurement system for monitoring environmental substance exchange as caused by emission/deposition of aerosol particles. For this study, 681 mass spectra of detected particles were sorted into groups of similarity by a clustering algorithm leading to five classes of different particle types. Each single mass spectrum was correlated to corresponding anemometer data (vertical wind vector and wind speed) in a time-resolved analysis. Due to sampling constraints time-resolution was limited to 36 s, as a result of transition time distributions through the sampling tube. Vertical particle flow (emission/deposition) was determined for all particles based on these data as acquired during a measuring campaign in Giessen, Germany. For a selected particle class a detailed up- and downwards flow consideration was performed to prove the developed approach. Particle flow of that class was dominated by an emission trend as expected. The presented combination of single-particle mass spectrometry and ultrasonic anemometry provides for the possibility to correlate chemical particle data and wind data in a distinct assignment for the description of turbulent particle behavior near earth surface. Results demonstrate the ability to apply the method to real micrometeorological systems, if sampling issues are properly considered for an intended time resolution.

Wind Measurements from Arc Scans with Doppler Wind Lidar

DOE PAGES

Wang, H.; Barthelmie, R. J.; Clifton, Andy; ...

2015-11-25

When defining optimal scanning geometries for scanning lidars for wind energy applications, we found that it is still an active field of research. Our paper evaluates uncertainties associated with arc scan geometries and presents recommendations regarding optimal configurations in the atmospheric boundary layer. The analysis is based on arc scan data from a Doppler wind lidar with one elevation angle and seven azimuth angles spanning 30° and focuses on an estimation of 10-min mean wind speed and direction. When flow is horizontally uniform, this approach can provide accurate wind measurements required for wind resource assessments in part because of itsmore » high resampling rate. Retrieved wind velocities at a single range gate exhibit good correlation to data from a sonic anemometer on a nearby meteorological tower, and vertical profiles of horizontal wind speed, though derived from range gates located on a conical surface, match those measured by mast-mounted cup anemometers. Uncertainties in the retrieved wind velocity are related to high turbulent wind fluctuation and an inhomogeneous horizontal wind field. Moreover, the radial velocity variance is found to be a robust measure of the uncertainty of the retrieved wind speed because of its relationship to turbulence properties. It is further shown that the standard error of wind speed estimates can be minimized by increasing the azimuthal range beyond 30° and using five to seven azimuth angles.« less

A novel five-wire micro anemometer with 3D directionality for low speed air flow detection and acoustic particle velocity detecting capability

NASA Astrophysics Data System (ADS)

Li, Zhe; Chang, Wenhan; Gao, Chengchen; Hao, Yilong

2018-04-01

In this paper, a novel five-wire micro-fabricated anemometer with 3D directionality based on calorimetric principle is proposed, which is capable of measuring low speed airflow. This structure is realized by vertically bonding two different dies, which can be fabricated on the same wafer resulting in a simple fabrication process. Experiments on speed lower than 200 mm s-1 are conducted, showing good repeatability and directionality. The speed of airflow is controlled by the volumetric flow rate. The measured velocity sensitivity is 9.4 mV · s m-1, with relative direction sensitivity of 37.1 dB. The deviation between the expected and the measured directivity is analyzed by both theories and simulations. A correction procedure is proposed and turns out to be useful to eliminate this deviation. To further explore the potential of our device, we expose it to acoustic plane waves in a standing wave tube, showing consistent planar directivity of figure of eight. The measured velocity sensitivity at 1 kHz and 120 dBC is 4.4 mV · s m-1, with relative direction sensitivity of 27.0 dB. By using the correction method proposed above, the maximum angle error is about  ±2°, showing its good directionality accuracy.

Laser anemometer measurements and computations for transonic flow conditions in an annular cascade of high turning core turbine vanes

NASA Technical Reports Server (NTRS)

Goldman, Louis J.

1993-01-01

An advanced laser anemometer (LA) was used to measure the axial and tangential velocity components in an annular cascade of turbine stator vanes operating at transonic flow conditions. The vanes tested were based on a previous redesign of the first-stage stator in a two-stage turbine for a high-bypass-ratio engine. The vanes produced 75 deg of flow turning. Tests were conducted on a 0.771-scale model of the engine-sized stator. The advanced LA fringe system employed an extremely small 50-micron diameter probe volume. Window correction optics were used to ensure that the laser beams did not uncross in passing through the curved optical access port. Experimental LA measurements of velocity and turbulence were obtained at the mean radius upstream of, within, and downstream of the stator vane row at an exit critical velocity ratio of 1.050 at the hub. Static pressures were also measured on the vane surface. The measurements are compared, where possible, with calculations from a three-dimensional inviscid flow analysis. Comparisons were also made with the results obtained previously when these same vanes were tested at the design exit critical velocity ratio of 0.896 at the hub. The data are presented in both graphical and tabulated form so that they can be readily compared against other turbomachinery computations.

Statistics of atmospheric turbulence within a natural black spruce forest canopy

NASA Astrophysics Data System (ADS)

Amiro, B. D.; Davis, P. A.

1988-08-01

Turbulence statistics were measured in a natural black-spruce forest canopy in southeastern Manitoba, Canada. Sonic anemometers were used to measure time series of vertical wind velocity ( w), and cup anemometers to measure horizontal wind speed ( s), above the canopy and at seven different heights within the canopy. Vertical profiles were measured during 25 runs on eight different days when conditions above the canopy were near-neutral. Profiles of s and of the standard deviation (Σ w ) of w show relatively little scatter and suggest that, for this canopy and these stability conditions, profiles can be predicted from simple measurements made above the canopy. Within the canopy, a negative skewness and a high kurtosis of the w-frequency distributions indicate asymmetry and the persistence of large, high-velocity eddies. The Eulerian time scale is only a weak function of height within the canopy. Although w-power spectra above the canopy are similar to those in the free atmosphere, we did not observe an extensive inertial subrange in the spectra within the canopy. Also, a second peak is present that is especially prominent near the ground. The lack of the inertial subrange is likely caused by the presence of sources and sinks for turbulent kinetic energy within our canopy. The secondary spectral peak is probably generated by wake turbulence caused by form drag on the wide, horizontal spruce branches.

Non-Destructive Impermeability Testing of Land-Based Sewage Systems (zerstoerungsfreie dichtheitspruefung con grundstuecksentwaesserungsleitungen)

DTIC Science & Technology

2001-01-01

CYberdeckungsh6he zunehmen. Ffr die Stabilitdt des Str ~mungszustandes ist dagegen ein weniger empfindlicher Ansaugstutzen von Vorteil, weil geringe Schwankungen im...Gerinnestr() mung mit einem Laser-Doppler- Anemometer und einem Pitot-Rohr Ltd. BD Dipl.-Ing. B. Ftirmaier M6glichkeiten der Verwertung von HausmUll und...GrundstticksentwAsserungsleitungen ISBN 3-486-26517-2 * diese Hefte k6nnen beim Oldenbourg Industrieverlag GmbH, Rosenheimer Str . 145, 81671 MUnchen bezogen werden (Preis pro Heft: 35,00 DM, Stand 2001)

Radionuclide counting technique for measuring wind velocity and direction

NASA Technical Reports Server (NTRS)

Singh, J. J. (Inventor)

1984-01-01

An anemometer utilizing a radionuclide counting technique for measuring both the velocity and the direction of wind is described. A pendulum consisting of a wire and a ball with a source of radiation on the lower surface of the ball is positioned by the wind. Detectors and are located in a plane perpendicular to pendulum (no wind). The detectors are located on the circumferene of a circle and are equidistant from each other as well as the undisturbed (no wind) source ball position.

The Ecological Impact of Beach Nourishment with Dredged Materials on the Intertidal Zone at Bogue Banks, North Carolina.

DTIC Science & Technology

1983-03-01

speedy recovery largely depended on recruitment from pelagic la 1 stocks. It also seemed to indicate that high turbidities associated with rishment can...Electronic Anemometer (model number BT), and salinity was measured using an American Optical Goldberg refrac- toaster. Wind direction and wave height of the...Isle beaches, January 1977 to September 1978. 26 Salinities at both beaches were similar. They were lower (averaging around 33 parts per thousand)in

Study of the structure of turbulent shear flows at supersonic speeds and high Reynolds number

NASA Technical Reports Server (NTRS)

Smits, A. J.; Bogdonoff, S. M.

1984-01-01

A major effort to improve the accuracies of turbulence measurement techniques is described including the development and testing of constant temperature hot-wire anemometers which automatically compensate for frequency responses. Calibration and data acquisition techniques for normal and inclined wires operated in the constant temperature mode, flow geometries, and physical models to explain the observed behavior of flows are discussed, as well as cooperation with computational groups in the calculation of compression corner flows.

KCMP Minnesota Tall Tower Nitrous Oxide Inverse Modeling Dataset 2010-2015

DOE Data Explorer

Griffis, Timothy J. [University of Minnesota; Baker, John; Millet, Dylan; Chen, Zichong; Wood, Jeff; Erickson, Matt; Lee, Xuhui

2017-01-01

This dataset contains nitrous oxide mixing ratios and supporting information measured at a tall tower (KCMP, 244 m) site near St. Paul, Minnesot, USA. The data include nitrous oxide and carbon dioxide mixing ratios measured at the 100 m level. Turbulence and wind data were measured using a sonic anemometer at the 185 m level. Also included in this dataset are estimates of the "background" nitrous oxide mixing ratios and monthly concentration source footprints derived from WRF-STILT modeling.

Crossed hot-wire data acquisition and reduction system

NASA Technical Reports Server (NTRS)

Westphal, R. V.; Mehta, R. D.

1984-01-01

The report describes a system for rapid computerized calibration acquisition, and processing of data from a crossed hot-wire anemometer is described. Advantages of the system are its speed, minimal use of analog electronics, and improved accuracy of the resulting data. Two components of mean velocity and turbulence statistics up to third order are provided by the data reduction. Details of the hardware, calibration procedures, response equations, software, and sample results from measurements in a turbulent plane mixing layer are presented.

Fuel-injector/air-swirl characterization

NASA Technical Reports Server (NTRS)

Mcvey, J. B.; Kennedy, J. B.; Russell, S.

1988-01-01

Experimental data on the characteristics of the spray produced by a gas-turbine engine airblast fuel injector are reported. The data acquired include the mass-flux distribution measured by use of a high-resolution spray patternator; the gas-phase velocity field measured by use of a two-component laser Doppler velocimeter, and the liquid droplet size and velocity distributions measured by use of a single-component phase-Doppler anemometer. The data are intended for use in assessments of two-phase flow computational methods as applied to combustor design procedures.

Joint Aircraft Survivability Program Final Test Report for the Acoustic Fire Suppression Project JASP-TR-14-05

DTIC Science & Technology

2016-09-01

focus of early research was the effects of acoustics on droplet burning in turbine engines and combustion chambers.5,21–23 The results of this... Wire Anemometer. Time-resolved mass readings were made using a model MS4002S Mettler Toledo Precision Balance. 5. Acoustic Extinction This section...nanotube sound projectors. Nanotechnology. 2013;24(23):235501. 40. Hu L, Liu S, Xu Y, Li D. A wind tunnel experimental study on burning rate

Lidar for Wind and Optical Turbulence Profiling

NASA Astrophysics Data System (ADS)

Fastig, Shlomo; Porat, Omer; Englander, Abraham; Sprung, Detlev; Stein, Karin U.; Sucher, Erik

2018-04-01

A field campaign for the comparison investigation of systems to measure wind and optical turbulence profiles was conducted in northern Germany. The experimental effort was to compare the performance of the LIDAR, SODAR-RASS and ultrasonic anemometers for the measurement of the above mentioned atmospheric parameters. Soreq's LIDAR is a fiber laser based system demonstrator for the vertical profiling of the wind and turbulence, based on the correlation of aerosol density variations. It provides measurements up to 350m with 20m resolution.

MEMS testing and applications in automotive and aerospace industries

NASA Astrophysics Data System (ADS)

Ma, Zhichun; Chen, Xuyuan

2009-05-01

MEMS technology combines micromachining and integrated circuit fabrication technologies to produce highly reliable MEMS transducers. This paper presents an overview of MEMS transducers applications, particularly in automotive and aerospace industries, which includes inertia sensors for safety, navigation, and guidance control, thermal anemometer for temperature and heat-flux sensors in engine applications, MEMS atomizers for fuel injection, and micromachined actuators for flow control applications. Design examples for the devices in above mentioned applications are also presented and test results are given.

The design and instrumentation of the Purdue annular cascade facility with initial data acquisition and analysis

NASA Technical Reports Server (NTRS)

Stauter, R. C.; Fleeter, S.

1982-01-01

Three dimensional aerodynamic data, required to validate and/or indicate necessary refinements to inviscid and viscous analyses of the flow through turbomachine blade rows, are discussed. Instrumentation and capabilities for pressure measurement, probe insertion and traversing, and flow visualization are reviewed. Advanced measurement techniques including Laser Doppler Anemometers, are considered. Data processing is reviewed. Predictions were correlated with the experimental data. A flow visualization technique using helium filled soap bubbles was demonstrated.

Investigation of the Development of Laminar Boundary-Layer Instabilities along a Blunted Cone

DTIC Science & Technology

1988-12-01

taps, having approximate diameters of 0.064 in., were connected by tubing either to one-psid Druck ® or 2.5-psid ESP transducers of the Tunnel B...surveys of the model boundary layer using a 15-psid Druck transducer calibrated for 10- psid fu l l scale. The small size of the pi tot probe (Section...of freedom greater than 3D . Estimates of the measured data uncertainties for this test, including the basic hot-wire anemometer measurements

Measurements of Ocean Surface Turbulence and Wave-Turbulence Interactions (PREPRINT)

DTIC Science & Technology

2008-02-19

measurements described here were obtained from a Þeld experiment conducted from R /P 1In the case of gas transfer, these molecular layers can also be at the...ßux data. The eddy covariance sys- tem included a three-axis anemometer/thermometer (Campbell CSAT 3), an open path infrared hygrometer/CO2 sensor...boom of R /P FLIP approximately 18 m from the hull at an elevation of 13 m above mean sea level (MSL). The infrared optical system was set-up with the

Shipboard Turbulence Measurements of the Marine Atmospheric Boundary Layer from Hires Experiment

DTIC Science & Technology

2012-07-01

TURBULENCE MEASUREMENTS OF THE MARINE ATMOSPHERIC BOUNDARY LAYER FROM HIRES EXPERIMENT John Kalogiros 1* , Q. Wang 2 , R . J. Lind 2 , T...Bodega Bay (Fig. 1). In- situ and sodar turbulence measurements were collected onboard R /V Robert Gordon Sproul (about 35 m length and 9.5 m...crow nest (middle of the ship, ship mast). The principal sensors installed on each mast were: CSAT -3 sonic anemometer and a CS7500 - LiCor LI7500

Processing techniques for correlation of LDA and thermocouple signals

NASA Astrophysics Data System (ADS)

Nina, M. N. R.; Pita, G. P. A.

1986-11-01

A technique was developed to enable the evaluation of the correlation between velocity and temperature, with laser Doppler anemometer (LDA) as the source of velocity signals and fine wire thermocouple as that of flow temperature. The discontinuous nature of LDA signals requires a special technique for correlation, in particular when few seeding particles are present in the flow. The thermocouple signal was analog compensated in frequency and the effect of the value of time constant on the velocity temperature correlation was studied.

Velocity precision measurements using laser Doppler anemometry

NASA Astrophysics Data System (ADS)

Dopheide, D.; Taux, G.; Narjes, L.

1985-07-01

A Laser Doppler Anemometer (LDA) was calibrated to determine its applicability to high pressure measurements (up to 10 bars) for industrial purposes. The measurement procedure with LDA and the experimental computerized layouts are presented. The calibration procedure is based on absolute accuracy of Doppler frequency and calibration of interference strip intervals. A four-quadrant detector allows comparison of the interference strip distance measurements and computer profiles. Further development of LDA is recommended to increase accuracy (0.1% inaccuracy) and to apply the method industrially.

Flight Test Measurement Techniques for Laminar Flow. Volume 23(Les techniques de mesure en vol des ecoulements laminaires)

DTIC Science & Technology

2003-10-01

Chapter 1 – Introduction 1-1 Chapter 2 – Boundary Layer Transition and Laminar Flow Concepts 2-1 2.1 Transition Mechanisms and Transition Prediction 2...Laminar flow control LSTM Lehrstuhl für Strömungsmechanik der Universität Erlangen LWK Laminarwindkanal Stuttgart L2F Laser two-focus anemometer MMO...2.1 Transition mechanisms and transition prediction Modern transonic transport aircraft are characterized by a swept wing resulting in high cruise

Helicity in the atmospheric boundary layer

NASA Astrophysics Data System (ADS)

Kurgansky, Michael; Koprov, Boris; Koprov, Victor; Chkhetiani, Otto

2017-04-01

An overview is presented of recent direct field measurements at the Tsimlyansk Scientific Station of A.M. Obukhov Institute of Atmospheric Physics in Moscow of turbulent helicity (and potential vorticity) using four acoustic anemometers positioned, within the atmospheric surface-adjacent boundary layer, in the vertices of a rectangular tetrahedron, with an approximate 5 m distance between the anemometers and a 5.5 m elevation of the tetrahedron base above the ground surface (Koprov, Koprov, Kurgansky and Chkhetiani. Izvestiya, Atmospheric and Oceanic Physics, 2015, Vol.51, 565-575). The same ideology was applied in a later field experiment in Tsimlyansk with the tetrahedron's size of 0.7 m and variable elevation over the ground from 3.5 to 25 m. It is illustrated with examples of the statistical distribution of instantaneous (both positive and negative) turbulent helicity values. A theory is proposed that explains the measured mean turbulent helicity sign, including the sign of contribution to helicity from the horizontal and vertical velocity & vorticity components, respectively, and the sign of helicity buoyant production term. By considering a superposition of the classic Ekman spiral solution and a jet-like wind profile that mimics a shallow breeze circulation over a non-uniformly heated Earth surface, a possible explanation is provided, why the measured mean turbulent helicity sign is negative. The pronounced breeze circulation over the Tsimlyansk polygon which is located nearby the Tsimlyansk Reservoir was, indeed, observed during the measurements period. Whereas, essentially positive helicity is injected into the boundary layer from the free atmosphere in the Northern Hemisphere.

Ground deposition of liquid droplets released from a point source in the atmospheric surface layer

NASA Astrophysics Data System (ADS)

Panneton, Bernard

1989-05-01

A series of field experiments is presented in which the ground deposition of liquid droplets, 120 and 150 micrometers in diameter, released from a point source at 7 meters above the ground level, was measured. A detailed description of the experimental technique is provided, and the results are presented and compared to the predictions of a few models. A new rotating droplet generator is described. Droplets are produced by the forced breakup of capillary liquid jets and droplet coalescence is inhibited by the rotational motion of the spray head. A system for analyzing spray samples was developed. This is a specialized image analysis system based on an electronic digitizing camera which measures the area and perimeter of stains left by dyed droplets collected on Kromekote cards. A complete set of meteorological data supports the ground-deposition data. The turbulent air velocities at two levels above the ground and the temperature of the air at one level were measured with one sonic anemometer and a sonic anemometer-thermometer. The vertical heat and momentum fluxes were estimated using the eddy-correlation technique. The two-dimensional deposition patterns are presented in the form of plots of contours of constant density, normalized arcwise distributions and crosswind integrated distributions. Models of the crosswind integrated deposit from Godson, Csanady, Walker, Bache and Sayer, and Wilson et al., are evaluated. The results indicate that the Wilson et al random walk model is adequate for predicting the ground deposition of the 150 micrometer droplets.

Helicity and potential vorticity in the surface boundary layer turbulence

NASA Astrophysics Data System (ADS)

Chkhetiani, Otto; Kurgansky, Michael; Koprov, Boris; Koprov, Victor

2016-04-01

An experimental measurement of all three components of the velocity and vorticity vectors, as well as the temperature and its gradient, and potential vorticity, has been developed using four acoustic anemometers. Anemometers were placed at vertices of a tetrahedron, the horizontal base of which was a rectangular triangle with equal legs, and the upper point was exactly above the top of the right angle. The distance from the surface to the tetrahedron its base was 5.5 m, and the lengths of legs and a vertical edge were 5 m. The measurements were carried out of total duration near 100 hours both in stable and unstable stratification conditions (at the Tsimlyansk Scientific Station in a uniform area of virgin steppe 700 x 650 m, August 2012). A covariance-correlation matrix for turbulent variations in all measured values has been calculated. In the daytime horizontal and vertical components of the helicity are of the order of -0.03 and +0.01 m s-2, respectively. The nighttime signs remain unchanged, but the absolute values are several times smaller. It is confirmed also by statistics of a relative helicity. The cospectra and spectral correlation coefficients have been calculated for all helicity components. The time variations in the components of "instantaneous" relative helicity and potential vorticity are considered. Connections of helicity with Monin-Obukhov length and the wind vertical profile structure are discussed. This work was supported by the Russian Science Foundation (Project No 14-27-00134).

Observational study of atmospheric surface layer and coastal weather in northern Qatar

NASA Astrophysics Data System (ADS)

Samanta, Dhrubajyoti; Sadr, Reza

2016-04-01

Atmospheric surface layer is the interaction medium between atmosphere and Earth's surface. Better understanding of its turbulence nature is essential in characterizing the local weather, climate variability and modeling of turbulent exchange processes. The importance of Middle East region, with its unique geographical, economical and weather condition is well recognized. However, high quality micrometeorological observational studies are rare in this region. Here we show experimental results from micrometeorological observations from an experimental site in the coastal region of Qatar during August-December 2015. Measurements of winds are obtained from three sonic anemometers installed on a 9 m tower placed at Al Ghariyah beach in northern Qatar (26.08 °N, 51.36 °E). Different surface layer characteristics is analyzed and compared with earlier studies in equivalent weather conditions. Monthly statistics of wind speed, wind direction, temperature, humidity and heat index are made from concurrent observations from sonic anemometer and weather station to explore variations with surface layer characteristics. The results also highlights potential impact of sea breeze circulation on local weather and atmospheric turbulence. The observed daily maximum temperature and heat index during morning period may be related to sea breeze circulations. Along with the operational micrometeorological observation system, a camera system and ultrasonic wave measurement system are installed recently in the site to study coastline development and nearshore wave dynamics. Overall, the complete observational set up is going to provide new insights about nearshore wind dynamics and wind-wave interaction in Qatar.

Coastal Land Air Sea Interaction: "the" beach towers

NASA Astrophysics Data System (ADS)

MacMahan, J. H.; Koscinski, J. S.; Ortiz-Suslow, D. G.; Haus, B. K.; Thornton, E. B.

2016-12-01

As part of the Coastal Land Air Sea Interaction (CLASI) experiment, an alongshore array of 6-m high towers instrumented with ultrasonic 3D anemometers and temperature-relative humidity sensors were deployed at five sandy beaches near the high-tide line in Monterey Bay, CA, in May-June 2016. A cross-shore array of towers was also deployed from within the active surfzone to the toe of the dune at one beach. In addition, waves and ocean temperature were obtained along the 10m isobath for each beach. The dissipative surfzone was O(80m) wide. The wave energy varies among the beaches owing to sheltering and refraction by the Monterey Canyon and headlands. The tides are semi-diurnal mixed, meso-tidal with a maximum tidal range of 2m. This results in a variable beach width from the tower to the tidal line. Footprint analysis for estimating the source region for the turbulent momentum fluxes, suggests that the observations represent three scenarios described as primarily ocean, mixed beach and ocean, and primarily beach. The direct-estimate of the atmospheric stability by the sonic anemometer suggest that all of the beaches are mostly unstable except for a few occurrences in the evening during low wind conditions. The onshore neutral drag coefficient (Cd) estimated at 10m heights is 3-5 times larger than open ocean estimates. Minimal variability was found in Cd based on the footprint analysis. Beach-specific spatial variability in Cd was found related to atmospheric stability and wave energy.

Preliminary analysis of the Nocturnal Atmospheric Boundary Layer during the experimental campaign CIBA 2008

NASA Astrophysics Data System (ADS)

Yagüe, C.; Maqueda, G.; Ramos, D.; Sastre, M.; Viana, S.; Serrano, E.; Morales, G.; Ayarzagüena, B.; Viñas, C.; Sánchez, E.

2009-04-01

An Atmospheric Boundary Layer campaign was developed in Spain along June 2008 at the CIBA (Research Centre for the Lower Atmosphere) site which is placed on a fairly homogeneous terrain in the centre of an extensive plateau (41°49' N, 4°56' W). Different instrumentation at several levels was available on a new 10m meteorological mast, including temperature and humidity sensors, wind vanes and cup anemometers, as well as one sonic anemometer. Besides, two quartz-based microbarometers were installed at 50 and 100m on the main permanent 100m tower placed at CIBA. Three additional microbarometers were deployed on the surface on a triangular array of approximately 200 m side, and a tethered balloon was used in order to record vertical profiles of temperature, wind and humidity up to 1000m. Finally, a GRIMM particle monitor (MODEL 365), which can be used to continuously measure each six seconds simultaneously the PM10, PM2.5 and PM1 values, was deployed at 1.5m. This work will show some preliminary results from the campaign CIBA 2008, analysing the main physical processes present in the atmospheric Nocturnal Boundary Layer (NBL), the different stability periods observed and the corresponding turbulent parameters, as well as the coherent structures detected. The pressure perturbations measured from the surface and tower levels make possible to study the main wave parameters from wavelet transform, and compared the structures detected by the microbarometers with those detected in the wind and particles records.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Piper, M; Lundquist, J K

Some recent investigations have begun to quantify turbulence and dissipation in frontal zones to address the question of what physical mechanism counteracts the intensification of temperature and velocity gradients across a developing front. Frank (1994) examines the turbulence structure of two fronts that passed a 200m instrumented tower near Karlsruhe, Germany. In addition to showing the mean vertical structure of the fronts as they pass the tower, Frank demonstrates that there is an order of magnitude or more increase in turbulent kinetic energy across the frontal zone. Blumen and Piper (1999) reported turbulence statistics, including dissipation rate measurements, from themore » MICROFRONTS field experiment, where high-frequency turbulence data were collected from tower-mounted hotwire and sonic anemometers in a cold front and in a density current. Chapman and Browning (2001) measured dissipation rate in a precipitating frontal zone with high-resolution Doppler radar. Their measurements were conducted above the surface layer, to heights of 5km. The dissipation rate values they found are comparable to those measured in Kennedy and Shapiro (1975) in an upper-level front. Here, we expand on these recent studies by depicting the behavior of the fine scales of turbulence near the surface in a frontal zone. The primary objective of this study is to quantify the levels of turbulence and dissipation occurring in a frontal zone through the calculation of kinetic energy spectra and dissipation rates. The high-resolution turbulence data used in this study are taken during the cold front that passed the MICROFRONTS site in the early evening hours of 20 March 1995. These new measurements can be used as a basis for parameterizing the effects of surface-layer turbulence in numerical models of frontogenesis. We present three techniques for calculating the dissipation rate: direct dissipation technique, inertial dissipation technique and Kolmogorov's four-fifths law. Dissipation rate calculations using these techniques are employed using data from both the sonic and hotwire anemometers, when possible. Unfortunately, direct calculations of {var_epsilon} were not possible during a part of the frontal passage because the high wind speeds concurrent with the frontal passage demand very high frequency resolution, beyond that possible with the hotwire anemometer, for direct {var_epsilon} calculations. The calculations resulting from these three techniques are presented for the cold front as a time series. Quantitative comparisons of the direct and indirect calculation techniques are also given. More detail, as well as a discussion of energy spectra, can be found in Piper & Lundquist(2004).« less

Analysis of urban boundary layer flow and turbulence parameters on the basis of an experimental campaign in Turin city

NASA Astrophysics Data System (ADS)

Trini Castelli, S.; Falabino, S.; Mortarini, L.; Ferrero, E.; Richiardone, R.; Anfossi, D.

2010-09-01

The flow and turbulence structure of the atmospheric boundary layer above urban areas is significantly perturbed by the density and distribution of buildings and other obstacles, by the thermal effect of the so-called ‘urban heat island' and by the possible presence of topographical inhomogeneities. A thorough investigation of the characteristics of the flow and turbulence in urban canopy was pursued both with an experimental approach, carrying out an intensive observational field campaign and analysing the observed data, and evaluating the boundary layer and turbulence parameterisations, which are used in the numerical meteorological and air pollution models. The experimental activity was carried out along a continuous 15-months observational period at four measurement sites, located in the city of Turin. Here we analyse the data gathered at a 25 m mast, displaced at one of the measuring stations and equipped with sonic anemometers at 5 m, 9 m, 25 m height. Close to the mast, a station measuring solar radiation, humidity and temperature at ground level was also active. Since Turin is characterised both by a complex urban fabric and by a very frequent low wind regime, the dataset allows also investigating and estimating the boundary layer parameters in the peculiar conditions of low wind speed. With regard to the dataset, a stationary test singled out that each anemometer recorded about 25-30% of stationary data, but only the 9% of data were simultaneously stationary at the three anemometers. Concerning the stability for the whole dataset, a neutral stratification developed in only the 3% of the cases, while the percentages raise to the 47% and 50% respectively for the stable and the unstable cases. In some cases different stability conditions occurred at different levels, this peculiarity was investigated. At the three levels the distributions of the observed horizontal turbulent velocity fluctuations do not present remarkable differences, whereas the vertical component assumes rather different values. Considering the whole observed data set, low wind speeds, here defined as speed values less than 1.5 m/s, occurred in more than 90% of the cases. A comprehensive analysis of the observed wind velocity and turbulent velocity fluctuations, of the calculated stability parameters, surface layer parameters and boundary layer height is illustrated and discussed. A comparison of the measured wind standard deviation profiles as a function of stability with the values predicted by literature parameterisations for flat undisturbed terrain is also presented.

Data Analysis of the NOAA-GIT (National Oceanic and Atmospheric Administration-Georgia Institute of Technology) Millimeter-Wave Propagation Experiment Near Flatville, Illinois.

DTIC Science & Technology

1985-08-01

nearby Lyman-a hygrometer with another wire ther- mometer within its gap, a prop-vane anemometer, and a psychrometer for mean temperature and...0.39-Hz pulse, the psychrometer gives six commutation cycles repeated at the 25-Hz rate. A commutation cycle consists of data from the wet and dry...bulbs and two reference values, four quantities in all. The psychrometer then returns toward thermal equilibrium until the next 0.39-Hz pulse calls for

Comparison of the bidirectional reflectance distribution function of various surfaces

NASA Astrophysics Data System (ADS)

Fernandez, Rene; Seasholtz, Richard G.; Oberle, Lawrence G.; Kadambi, Jaikrishnan R.

1989-04-01

This paper describes the development and use of a system to measure the bidirectional reflectance distribution function (BRDF) of various surfaces. The BRDF measurements are to be used in the analysis and design of optical measurement systems such as laser anemometers. An Ar-ion laser (514 nm) was the light source. Preliminary results are presented for eight samples: two glossy black paints, two flat black paints, black glass, sand-blasted Al, unworked Al, and a white paint. A BaSO4 white reflectance standard was used as the reference sample throughout the tests.

Potential errors in using one anemometer to characterize the wind power over an entire rotor disk

NASA Technical Reports Server (NTRS)

Simon, R. L.

1982-01-01

Wind data collected at four levels on a 90-m tower in a prospective wind farm area are used to evaluate how well the 10-m wind speed data with and without intermittent vertical profile measurements compare with the 90-m tower data. If a standard, or even predictable, wind speed profile existed, there would be no need for a large, expensive tower. This cost differential becomes even more significant if several towers are needed to study a prospective wind farm.

Rotor wake characteristics of a transonic axial flow fan

NASA Technical Reports Server (NTRS)

Hathaway, M. D.; Gertz, J.; Epstein, A.; Strazisar, A. J.

1985-01-01

State of the art turbomachinery flow analysis codes are not capable of predicting the viscous flow features within turbomachinery blade wakes. Until efficient 3D viscous flow analysis codes become a reality there is therefore a need for models which can describe the generation and transport of blade wakes and the mixing process within the wake. To address the need for experimental data to support the development of such models, high response pressure measurements and laser anemometer velocity measurements were obtained in the wake of a transonic axial flow fan rotor.

A chamber design for closed ecological systems research

NASA Technical Reports Server (NTRS)

Schwartzkopf, H.; Stofan, P. E.

1981-01-01

A single-plant growth chamber is described which is closed with respect to nutrient and gas flows, in order to serve as a tool in the investigation of control over biological systems. Such control procedures are essential for the use of biological components in the development of a closed ecological life support system (CELSS). The chamber's design consists of two concentric clear plastic cylinders equipped with aeroponic feed tubing, a supporting platform for the plant and a set of sensors that includes an anemometer, thermistors, pressure and strain gauges, and humidity sensors.

Geographically distributed environmental sensor system

DOEpatents

French, Patrick; Veatch, Brad; O'Connor, Mike

2006-10-03

The present invention is directed to a sensor network that includes a number of sensor units and a base unit. The base station operates in a network discovery mode (in which network topology information is collected) in a data polling mode (in which sensed information is collected from selected sensory units). Each of the sensor units can include a number of features, including an anemometer, a rain gauge, a compass, a GPS receiver, a barometric pressure sensor, an air temperature sensor, a humidity sensor, a level, and a radiant temperature sensor.

Sound and fluctuating disturbance measurements in the settling chamber and test section of a small, Mach 5 wind tunnel

NASA Technical Reports Server (NTRS)

Anders, J. B.; Stainback, P. C.; Beckwith, I. E.; Keefe, L. R.

1975-01-01

Disturbance measurements were made using a hot-wire anemometer and piezoelectric pressure transducers in the settling chamber and free stream of a small Mach 5 wind tunnel. Results from the two instruments are compared and acoustical disturbances in the settling chamber are discussed. The source of the test-section noise is identified as nozzle-wall waviness at low Reynolds numbers and as eddy-Mach-wave radiation from the turbulent boundary layer on the nozzle wall at high Reynolds numbers.

Air/Sea Transfer of Gases and Aerosols

DTIC Science & Technology

2003-09-30

of tubing from the boom at the western end of the pier. The boom housed the inlet and a Campbell CSAT sonic anemometer, which measured three...with the return flow from breaking waves onshore. 0 5 10 15 20 25 30 35 40 45 50 0 1 2 3 4 5 6 7 U10 (m/s) k 6 00 (c m /h r ) this study wanninkof...ultimately result in improved algorithms relating the state of the air/sea interface to remotely sensed properties. REFERENCES Bandy, A, R ., D

Long-range, noncoherent laser Doppler velocimeter.

PubMed

Bloom, S H; Kremer, R; Searcy, P A; Rivers, M; Menders, J; Korevaar, E

1991-11-15

An experimental demonstration of a long-range, noncoherent laser Doppler velocimeter (LDV) is presented. The LDV detects incoming Doppler-shifted signal photons by using the sharp spectral absorption features in atomic or molecular vapors. The edge of the absorption feature is used to convert changes in frequency to large changes in transmission. Preliminary measurements of wind velocity using seeded aerosols showed that the LDV results agreed with mechanical anemometer measurements to within the accuracy of the LDV measurements. With optimization the LDV will provide accurate range-resolved and vibration-tolerant wind-speed measurements at large distances.

Evaluation of turbulence measurement techniques from a single Doppler lidar

NASA Astrophysics Data System (ADS)

Bonin, Timothy A.; Choukulkar, Aditya; Brewer, W. Alan; Sandberg, Scott P.; Weickmann, Ann M.; Pichugina, Yelena L.; Banta, Robert M.; Oncley, Steven P.; Wolfe, Daniel E.

2017-08-01

Measurements of turbulence are essential to understand and quantify the transport and dispersal of heat, moisture, momentum, and trace gases within the planetary boundary layer (PBL). Through the years, various techniques to measure turbulence using Doppler lidar observations have been proposed. However, the accuracy of these measurements has rarely been validated against trusted in situ instrumentation. Herein, data from the eXperimental Planetary boundary layer Instrumentation Assessment (XPIA) are used to verify Doppler lidar turbulence profiles through comparison with sonic anemometer measurements. For 17 days at the end of the experiment, a single scanning Doppler lidar continuously cycled through different turbulence measurement strategies: velocity-azimuth display (VAD), six-beam scans, and range-height indicators (RHIs) with a vertical stare.Measurements of turbulence kinetic energy (TKE), turbulence intensity, and stress velocity from these techniques are compared with sonic anemometer measurements at six heights on a 300 m tower. The six-beam technique is found to generally measure turbulence kinetic energy and turbulence intensity the most accurately at all heights (r2 ≈ 0.78), showing little bias in its observations (slope of ≈ 0. 95). Turbulence measurements from the velocity-azimuth display method tended to be biased low near the surface, as large eddies were not captured by the scan. None of the methods evaluated were able to consistently accurately measure the shear velocity (r2 = 0.15-0.17). Each of the scanning strategies assessed had its own strengths and limitations that need to be considered when selecting the method used in future experiments.

Laser Anemometer Measurements of the Flow Field in a 4:1 Pressure Ratio Centrifugal Impeller

NASA Technical Reports Server (NTRS)

Skoch, G. J.; Prahst, P. S.; Wernet, M. P.; Wood, J. R.; Strazisar, A. J.

1997-01-01

A laser-doppler anemometer was used to obtain flow-field velocity measurements in a 4:1 pressure ratio, 4.54 kg/s (10 lbm/s), centrifugal impeller, with splitter blades and backsweep, which was configured with a vaneless diffuser. Measured through-flow velocities are reported for ten quasi-orthogonal survey planes at locations ranging from 1% to 99% of main blade chord. Measured through-flow velocities are compared to those predicted by a 3-D viscous steady flow analysis (Dawes) code. The measurements show the development and progression through the impeller and vaneless diffuser of a through-flow velocity deficit which results from the tip clearance flow and accumulation of low momentum fluid centrifuged from the blade and hub surfaces. Flow traces from the CFD analysis show the origin of this deficit which begins to grow in the inlet region of the impeller where it is first detected near the suction surface side of the passage. It then moves toward the pressure side of the channel, due to the movement of tip clearance flow across the impeller passage, where it is cut by the splitter blade leading edge. As blade loading increases toward the rear of the channel the deficit region is driven back toward the suction surface by the cross-passage pressure gradient. There is no evidence of a large wake region that might result from flow separation and the impeller efficiency is relatively high. The flow field in this impeller is quite similar to that documented previously by NASA Lewis in a large low-speed backswept impeller.

Long-range distributed optical fiber hot-wire anemometer based on chirped-pulse ΦOTDR.

PubMed

Garcia-Ruiz, Andres; Dominguez-Lopez, Alejandro; Pastor-Graells, Juan; Martins, Hugo F; Martin-Lopez, Sonia; Gonzalez-Herraez, Miguel

2018-01-08

We demonstrate a technique allowing to develop a fully distributed optical fiber hot-wire anemometer capable of reaching a wind speed uncertainty of ≈ ±0.15m/s (±0.54km/h) at only 60 mW/m of dissipated power in the sensing fiber, and within only four minutes of measurement time. This corresponds to similar uncertainty values than previous papers on distributed optical fiber anemometry but requires two orders of magnitude smaller dissipated power and covers at least one order of magnitude longer distance. This breakthrough is possible thanks to the extreme temperature sensitivity and single-shot performance of chirped-pulse phase-sensitive optical time domain reflectometry (ΦOTDR), together with the availability of metal-coated fibers. To achieve these results, a modulated current is fed through the metal coating of the fiber, causing a modulated temperature variation of the fiber core due to Joule effect. The amplitude of this temperature modulation is strongly dependent on the wind speed at which the fiber is subject. Continuous monitoring of the temperature modulation along the fiber allows to determine the wind speed with singular low power injection requirements. Moreover, this procedure makes the system immune to temperature drifts of the fiber, potentially allowing for a simple field deployment. Being a much less power-hungry scheme, this method also allows for monitoring over much longer distances, in the orders of 10s of km. We expect that this system can have application in dynamic line rating and lateral wind monitoring in railway catenary wires.

High-quality eddy-covariance CO2 budgets under cold climate conditions

NASA Astrophysics Data System (ADS)

Kittler, Fanny; Eugster, Werner; Foken, Thomas; Heimann, Martin; Kolle, Olaf; Göckede, Mathias

2017-08-01

This study aimed at quantifying potential negative effects of instrument heating to improve eddy-covariance flux data quality in cold environments. Our overarching objective was to minimize heating-related bias in annual CO2 budgets from an Arctic permafrost system. We used continuous eddy-covariance measurements covering three full years within an Arctic permafrost ecosystem with parallel sonic anemometers operation with activated heating and without heating as well as parallel operation of open- and closed-path gas analyzers, the latter serving as a reference. Our results demonstrate that the sonic anemometer heating has a direct effect on temperature measurements while the turbulent wind field is not affected. As a consequence, fluxes of sensible heat are increased by an average 5 W m-2 with activated heating, while no direct effect on other scalar fluxes was observed. However, the biased measurements in sensible heat fluxes can have an indirect effect on the CO2 fluxes in case they are used as input for a density-flux WPL correction of an open-path gas analyzer. Evaluating the self-heating effect of the open-path gas analyzer by comparing CO2 flux measurements between open- and closed-path gas analyzers, we found systematically higher CO2 uptake recorded with the open-path sensor, leading to a cumulative annual offset of 96 gC m-2, which was not only the result of the cold winter season but also due to substantial self-heating effects during summer. With an inclined sensor mounting, only a fraction of the self-heating correction for vertically mounted instruments is required.

Crossflow vorticity sensor

NASA Technical Reports Server (NTRS)

Holmes, Bruce J. (Inventor); Carraway, Debra L. (Inventor); Holmes, Harlan K. (Inventor); Moore, Thomas C. (Inventor)

1988-01-01

A crossflow vorticity sensor for the detection of crossflow vorticity characteristics is described. The sensor is comprised of crossflow sensors which are noninvasively adhered to a swept wing laminar surface either singularly, in multi-element strips, in polar patterns, or in orthogonal patterns. These crossflow sensors are comprised of hot-film sensor elements which operate as a constant temperature anemometer circuit to detect heat transfer rate changes. Accordingly, crossflow vorticity characteristics are determined via cross-correlation. In addition, the crossflow sensors have a thickness which does not exceed a maximum value h in order to avoid contamination of downstream crossflow sensors.

Testing of the anemometer circuit: Data report

NASA Technical Reports Server (NTRS)

Moen, Michael J.

1992-01-01

The following text discusses results from the electronic step testing and the beginning of velocity step testing in the shock tube. It should be kept in mind that frequency response is always measured as the time from the beginning of the event to the minimum (positive inflection) of the 'bucket' that immediately follows the response. This report is not a complete account of the results from square wave testing. Some data is still in the process of being analyzed and efforts are being made to fit the data to both Freymuth's third order theory and modelled responses from SPICE circuit simulation software.

Rectangular subsonic jet flow field measurements

NASA Technical Reports Server (NTRS)

Morrison, Gerald L.; Swan, David H.

1990-01-01

Flow field measurements of three subsonic rectangular cold air jets are presented. The three cases had aspect ratios of 1x2, 1x4 at a Mach number of 0.09 and an aspect ratio of 1x2 at a Mach number of 0.9. All measurements were made using a 3-D laser Doppler anemometer system. The data includes the mean velocity vector, all Reynolds stress tensor components, turbulent kinetic energy and velocity correlation coefficients. The data are presented in tabular and graphical form. No analysis of the measured data or comparison to other published data is made.

An Experimental Study of Plunging Liquid Jet Induced Air Carryunder and Dispersion

DTIC Science & Technology

1991-12-24

the ’ greenhouse ’ effect (ie, the absorption of CO2 by the oceans), and a number of other important maritime-related applications. In particular, the air entrainment process due to the breaking bow waves of surface ships may cause long (ie, up to 5 km in length) wakes. Naturally easily detectable wakes are undesirable for naval warships. In the present study plunging liquid jet experiments were performed and detailed Laser Doppler Anemometer (LDA) data were taken of the phasic velocity field and the void fraction distribution in the induced two-phase

Comparison of the bidirectional reflectance distribution function of various surfaces

NASA Technical Reports Server (NTRS)

Fernandez, Rene; Seasholtz, Richard G.; Oberle, Lawrence G.; Kadambi, Jaikrishnan R.

1988-01-01

Described is the development and use of a system to measure the Bidirectional Reflectance Distribution Function (BRDF) of various surfaces. The BRDF measurements are used in the analysis and design of optical measurement systems, such as laser anemometers. An argon ion laser (514 nm) is the light source. Preliminary results are presented for eight samples: two glossy black paints, two flat black paints, black glass, sand blasted aluminum, unworked aluminum, and a white paint. A BaSO4 white reflectance standard was used as the reference sample throughout the tests. The reflectance characteristics of these surfaces are compared.

Improved Apparatus for the Measurement of Fluctuations of Air Speed in Turbulent Flow

NASA Technical Reports Server (NTRS)

Mock, W C , Jr; Dryden, H L

1934-01-01

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.

Boundary Layer Measurements on Slender Blunt Cones at Free-Stream Mach Number 8

DTIC Science & Technology

1979-12-01

34 Angle of a t t a c k , deg Model c o n f i g u r a t i o n d e s i g n a t i o n Center of rotation~ tunnel centerline axial station about...ft/sec X Axial location located from virtual apex of 7-deg cone model, in. ZA ZP ZT ~ . . = ° Anemometer-probe height, distance to probe...300 psla at Math number 6, and 50 to 900 psia at Math number 8, with air supplied by the VKF main compressor plant. Stagnation temperatures sufficient

The complex of optical methods for study of gas-liquid jets

NASA Astrophysics Data System (ADS)

Poplavski, S. V.; Boiko, V. M.

2017-10-01

A set of optical methods for studying the dispersion and dynamics of liquids in high-speed gas jets was realized. Four optical methods were used: shadow imaging, PIV method, Laser Doppler Anemometer (LDA), a method for recording the dispersity of a spray by angular scattering of light. With the example of a supersonic coaxial jet with a central fluid supply, a technique is developed that makes it possible to obtain not only the sum of the data by four methods but new critical data on the structure of the two-phase flow, such as the concentration distributions of the spray.

Oahu wind power survey, first report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramage, C.S.; Daniels, P.A.; Schroeder, T.A.

1977-05-01

A wind power survey has been conducted on Oahu since summer 1975. At seventeen potentially windy sites, calibrated anemometers and wind vanes were installed and recordings made on computer-processable magnetic tape cassettes. From monthly mean wind speeds--normalized by comparing with Honolulu Airport means winds--it was concluded that about 23 mi/hr represented the highest average annual wind speed likely to be attained on Oahu and that the Koko Head and Kahuku areas gave the most promise for wind energy generation. Diurnal variation of the wind in these areas roughly parallels diurnal variation of electric power demand.

Multifractal Analysis of the Small Time-Scale Boundary-Layer Characteristics of the Wind: the Anisotropy and Extremes

NASA Astrophysics Data System (ADS)

Fitton, G. F.; Tchiguirinskaia, I.; Schertzer, D. J.; Lovejoy, S.

2012-12-01

Under various physical conditions (mean temperature and velocity gradients, stratification and rotation) atmospheric turbulent flows remain intrinsically anisotropic. The immediate vicinity of physical boundaries rises to a greater complexity of the anisotropy effects. In this paper we address the issue of the scaling anisotropy of the wind velocity fields within the atmospheric boundary layer (ABL). Under the universal multifractal (UM) framework we compare the small time-scale (0.1 to 1,000 seconds) boundary-layer characteristics of the wind for two different case studies. The first case study consisted of a single mast located within a wind farm in Corsica, France. Three sonic anemometers were installed on the mast at 22, 23 and 43m, measuring three-dimensional wind velocity data at 10Hz. Wakes, complex terrain and buoyancy forces influenced the measurements. The second case study (GROWIAN experiment in Germany) consisted of an array of propeller anemometers measuring wind speed inflow data at 2.5Hz over flat terrain. The propeller anemometers were positioned vertically at 10, 50, 75, 100, 125 and 150m with four horizontal measurements taken at 75, 100 and 125m. The spatial distribution allowed us to calculate the horizontal and vertical shear structure functions of the horizontal wind. Both case studies are within a kilometre from the sea. For the first case study (10Hz measurements in a wind farm test site) the high temporal resolution of the data meant we observed Kolmogorov scaling from 0.2 seconds (with intermittency correction) right up to 1,000 seconds at which point a scaling break occurred. After the break we observed a scaling power law of approximately 2, which is in agreement with Bolgiano-Obukhov scaling theory with intermittency correction. However, for the second case study (2.5Hz on flat terrain) we only observed Kolmogorov scaling from 6.4 seconds (also with intermittency correction). The spectra of horizontal velocity components remain anisotropic over high frequencies, where u1 most scales as Bolgiano-Obukhov and u2 scales as Kolmogorov. The scaling law of the vertical shears of the horizontal wind in the array varied from Kolmogorov to Bolgiano-Obukhov with height depending on the condition of stability. We interpret the results with the UM anisotropic model that greatly enhances our understanding of the ABL structure. Comparing the two case studies we found in both cases the multifractality parameter of about 1.6, which remains close to the estimates obtained for the free atmosphere. From the UM parameters, the exponent of the power law of the distribution of the extremes can be predicted. Over small scales, this exponent is of about 7.5 for the wind velocity, which is a crucial result for applications within the field of wind energy.

Study of a Wake Recovery Mechanism in a High-Speed Axial Compressor Stage

NASA Technical Reports Server (NTRS)

VanZante, Dale E.

1998-01-01

This work addresses the significant differences in compressor rotor wake mixing loss which exist in a stage environment relative to a rotor in isolation. The wake decay for a rotor in isolation is due solely to viscous dissipation which is an irreversible process and thus leads to a loss in both total pressure and efficiency. Rotor wake decay in the stage environment is due to both viscous mixing and the inviscid strain imposed on the wake fluid particles by the stator velocity field. This straining process, referred to by Smith (1993) as recovery, is reversible and for a 2D rotor wake leads to an inviscid reduction of the velocity deficit of the wake. A model for the rotor wake decay process is developed and used to quantify the viscous dissipation effects relative to those of inviscid wake stretching. The model is verified using laser anemometer measurements acquired in the wake of a transonic rotor operated in isolation and in a stage configuration at near peak efficiency and near stall operating conditions. Additional insight is provided by a time-accurate 3D Navier-Stokes simulation of the compressor stator flow field at the corresponding stage loading levels. Results from the wake decay model exhibit good agreement with the experimental data. Data from the model, laser anemometer measurements, and numerical simulations indicate that for the rotor/stator spacing used in this work, which is typical of core compressors, rotor wake straining (stretching) is the primary decay process in the stator passage with viscous mixing playing only a minor role. The implications of these results on compressor stage design are discussed.

Design and use of a sparged platform for energy flux measurements over lakes

NASA Astrophysics Data System (ADS)

Gijsbers, S.; Wenker, K.; van Emmerik, T.; de Jong, S.; Annor, F.; Van De Giesen, N.

2012-12-01

Energy flux measurements over lakes or reservoirs demand relatively stable platforms. Platforms can not be stabilized by fixing them on the bottom of the lake when the water body is too deep or when water levels show significant fluctuations. We present the design and first operational results of a sparged platform. The structure consists of a long PVC pipe, the sparge, which is closed at the bottom. On the PVC pipe rests an aluminum frame platform that carries instrumentation and solar power panel. In turn, the platform rests partially on a large inflated tire. At the bottom of the PVC pipe, lead weights and batteries were placed to ensure a very low point of gravity to minimize wave impact on the platform movement. The tire ensures a large second moment of the water plane. The overall volume of displacement is small in this sparged design. The combination of large second momentum of the water plane and small displacement ensure a high placement of the metacenter. The distance between the point of gravity and the metacenter is relatively long and the weight is large due to the weights and batteries. This ensures that the eigenfrequency of the platform is very low. The instrumentation load consisted of a WindMaster Pro (sonic anemometer for 3D wind speed and air temperature to perform eddy covariance measurements of sensible heat flux), a NR Lite (net radiometer), and air temperature and relative humidity sensors. The platform had a wind vane and the sparge could turn freely around its anchor cable to ensure that the anemometer always faced upwind. A compass in the logger completed this setup. The stability was measured with an accelerometer. In addition to the design and its stability, some first energy flux results will be presented.

An Analysis of Peak Wind Speed Data from Collocated Mechanical and Ultrasonic Anemometers

NASA Technical Reports Server (NTRS)

Short, David A.; Wells, Leonard A.; Merceret, Francis J.; Roeder, William P.

2005-01-01

This study focuses on a comparison of peak wind speeds reported by mechanical and ultrasonic anemometers at Cape Canaveral Air Force Station and Kennedy Space Center (CCAFS/KSC) on the east central coast of Florida and Vandenberg Air Force Base (VAFB) on the central coast of California. The legacy mechanical wind instruments on CCAFS/KSC and VAFB weather towers are being changed from propeller-and-vane (CCAFS/KSC) and cup-and-vane (VAFB) sensors to ultrasonic sensors under the Range Standardization and Automation (RSA) program. The wind tower networks on KSC/CCAFS and VAFB have 41 and 27 towers, respectively. Launch Weather Officers, forecasters, and Range Safety analysts at both locations need to understand the performance of the new wind sensors for a myriad of reasons that include weather warnings, watches, advisories, special ground processing operations, launch pad exposure forecasts, user Launch Commit Criteria (LCC) forecasts and evaluations, and toxic dispersion support. The Legacy sensors measure wind speed and direction mechanically. The ultrasonic RSA sensors have no moving parts. Ultrasonic sensors were originally developed to measure very light winds (Lewis and Dover 2004). The technology has evolved and now ultrasonic sensors provide reliable wind data over a broad range of wind speeds. However, because ultrasonic sensors respond more quickly than mechanical sensors to rapid fluctuations in speed, characteristic of gusty wind conditions, comparisons of data from the two sensor types have shown differences in the statistics of peak wind speeds (Lewis and Dover 2004). The 45th Weather Squadron (45 WS) and the 30 WS requested the Applied Meteorology Unit (AMU) to compare data from RSA and Legacy sensors to determine if there are significant differences in peak wind speed information from the two systems.

A computer controlled signal preprocessor for laser fringe anemometer applications

NASA Technical Reports Server (NTRS)

Oberle, Lawrence G.

1987-01-01

The operation of most commercially available laser fringe anemometer (LFA) counter-processors assumes that adjustments are made to the signal processing independent of the computer used for reducing the data acquired. Not only does the researcher desire a record of these parameters attached to the data acquired, but changes in flow conditions generally require that these settings be changed to improve data quality. Because of this limitation, on-line modification of the data acquisition parameters can be difficult and time consuming. A computer-controlled signal preprocessor has been developed which makes possible this optimization of the photomultiplier signal as a normal part of the data acquisition process. It allows computer control of the filter selection, signal gain, and photo-multiplier voltage. The raw signal from the photomultiplier tube is input to the preprocessor which, under the control of a digital computer, filters the signal and amplifies it to an acceptable level. The counter-processor used at Lewis Research Center generates the particle interarrival times, as well as the time-of-flight of the particle through the probe volume. The signal preprocessor allows computer control of the acquisition of these data.Through the preprocessor, the computer also can control the hand shaking signals for the interface between itself and the counter-processor. Finally, the signal preprocessor splits the pedestal from the signal before filtering, and monitors the photo-multiplier dc current, sends a signal proportional to this current to the computer through an analog to digital converter, and provides an alarm if the current exceeds a predefined maximum. Complete drawings and explanations are provided in the text as well as a sample interface program for use with the data acquisition software.

Wind Ressources in Complex Terrain investigated with Synchronized Lidar Measurements

NASA Astrophysics Data System (ADS)

Mann, J.; Menke, R.; Vasiljevic, N.

2017-12-01

The Perdigao experiment was performed by a number of European and American universities in Portugal 2017, and it is probably the largest field campaign focussing on wind energy ressources in complex terrain ever conducted. 186 sonic anemometers on 50 masts, 20 scanning wind lidars and a host of other instruments were deployed. The experiment is a part of an effort to make a new European wind atlas. In this presentation we investigate whether scanning the wind speed over ridges in this complex terrain with multiple Doppler lidars can lead to an efficient mapping of the wind resources at relevant positions. We do that by having pairs of Doppler lidars scanning 80 m above the ridges in Perdigao. We compare wind resources obtained from the lidars and from the mast-mounted sonic anemometers at 80 m on two 100 m masts, one on each of the two ridges. In addition, the scanning lidar measurements are also compared to profiling lidars on the ridges. We take into account the fact that the profiling lidars may be biased due to the curvature of the streamlines over the instrument, see Bingol et al, Meteorolog. Z. vol. 18, pp. 189-195 (2009). We also investigate the impact of interruptions of the lidar measurements on the estimated wind resource. We calculate the relative differences of wind along the ridge from the lidar measurements and compare those to the same obtained from various micro-scale models. A particular subject investigated is how stability affects the wind resources. We often observe internal gravity waves with the scanning lidars during the night and we quantify how these affect the relative wind speed on the ridges.

Sensors for Using Times of Flight to Measure Flow Velocities

NASA Technical Reports Server (NTRS)

Fralick, Gutave; Wrbanek, John D.; Hwang, Danny; Turso, James

2006-01-01

Thin-film sensors for measuring flow velocities in terms of times of flight are undergoing development. These sensors are very small and can be mounted flush with surfaces of airfoils, ducts, and other objects along which one might need to measure flows. Alternatively or in addition, these sensors can be mounted on small struts protruding from such surfaces for acquiring velocity measurements at various distances from the surfaces for the purpose of obtaining boundary-layer flow-velocity profiles. These sensors are related to, but not the same as, hot-wire anemometers. Each sensor includes a thin-film, electrically conductive loop, along which an electric current is made to flow to heat the loop to a temperature above that of the surrounding fluid. Instantaneous voltage fluctuations in segments of the loop are measured by means of electrical taps placed at intervals along the loop. These voltage fluctuations are caused by local fluctuations in electrical resistance that are, in turn, caused by local temperature fluctuations that are, in turn, caused by fluctuations in flow-induced cooling and, hence, in flow velocity. The differential voltage as a function of time, measured at each pair of taps, is subjected to cross-correlation processing with the corresponding quantities measured at other pairs of taps at different locations on the loop. The cross-correlations yield the times taken by elements of fluid to travel between the pairs of taps. Then the component of velocity along the line between any two pairs of taps is calculated simply as the distance between the pairs of taps divided by the travel time. Unlike in the case of hot-wire anemometers, there is no need to obtain calibration data on voltage fluctuations versus velocity fluctuations because, at least in principle, the correlation times are independent of the calibration data.

The surface renewal method for better spatial resolution of evapotranspiration measurements

NASA Astrophysics Data System (ADS)

Suvocarev, K.; Fischer, M.; Massey, J. H.; Reba, M. L.; Runkle, B.

2017-12-01

Evaluating feasible irrigation strategies when water is scarce requires measurements or estimations of evapotranspiration (ET). Direct observations of ET from agricultural fields are preferred, and micrometeorological methods such as eddy covariance (EC) provide a high quality, continuous time series of ET. However, when replicates of the measurements are needed to compare irrigation strategies, the cost of such experiments is often prohibitive and limits experimental scope. An alternative micrometeorological approach to ET, the surface renewal (SR) method, may be reduced to a thermocouple and a propeller anemometer (Castellvi and Snyder, 2009). In this case, net radiation, soil and sensible heat flux (H) are measured and latent heat flux (an energy equivalent for ET) is estimated as the residual of the surface energy-balance equation. In our experiment, thermocouples (Type E Fine-Wire Thermocouple, FW3) were deployed next to the EC system and combined with mean horizontal wind speed measurements to obtain H using SR method for three weeks. After compensating the temperature signal for non-ideal frequency response in the wavelet half-plane and correcting the sonic anemometer for the flow distortion (Horst et al., 2015), the SR H fluxes compared well to those measured by EC (r2 = 0.9, slope = 0.92). This result encouraged us to install thermocouples over 16 rice fields under different irrigation treatments (continuous cascade flood, continuous multiple inlet rice irrigation, alternate wetting and drying, and furrow irrigation). The EC measurements with net radiometer and soil heat flux plates are deployed at three of these fields to provide a direct comparison. The measurement campaign will finish soon and the data will be processed to evaluate the SR approach for ET estimation. The results will be used to show better spatial resolution of ET measurements to support irrigation decisions in agricultural crops.

Exploring the influence of surface waves in the carbon dioxide transfer velocity between the ocean and atmosphere in the coastal region

NASA Astrophysics Data System (ADS)

Ocampo-Torres, Francisco Javier; Francisco Herrera, Carlos; Gutiérrez-Loza, Lucía; Osuna, Pedro

2016-04-01

Field measurements have been carried out in order to better understand the possible influence of ocean surface waves in the transfer of carbon dioxide between the ocean and atmosphere in the coastal zone. The CO2 fluxes are being analysed and results are shown in a contribution by Gutiérrez-Loza et al., in this session. Here we try to highlight the findings regarding the transfer velocity (kCO2) once we have incorporated direct measurements of carbon dioxide concentration in the water side. In this study direct measurements of CO2 fluxes were obtained with an eddy covariance tower located in the shoreline equipped with an infrared open-path gas analyzer (LI-7500, LI-COR) and a sonic anemometer (R3-100 Professional Anemometer, Gill Instruments), both at about 13 m above the mean sea level, and sampling at 20 Hz. For some period of time simultaneous information of waves was recorded with a sampling rate of 2 Hz using an Acoustic Doppler Current Profiler (Workhorse Sentinel, Teledyne RD Instruments) at 10 m depth and 350 m away from the tower. Besides, recently the concentration of CO2 in water has also been recorded making use of a SAMI-CO2 instrument. A subtle effect of the wave field is detected in the estimated kCO2. Looking into details of the surface currents being detected very near the air-sea interface through an ADPC, a certain association can be found with the gas transfer velocity. Furthermore, some of the possible effects of breaking wave induced turbulence in the coastal zone is to be addressed. This work represents a RugDiSMar Project (CONACYT 155793) contribution. The support from CB-2011-01-168173 CONACYT project is greatly acknowledged.

A Study of Variations in Atmospheric Turbulence Kinetic Energy on a Sandy Beach

NASA Astrophysics Data System (ADS)

Koscinski, J. S.; MacMahan, J. H.; Wang, Q.; Thornton, E. B.

2016-12-01

A 6-m high, meteorological tower consisting six evenly spaced ultrasonic anemometers and temperature-relative humidity sensors was deployed at the high tide line on sandy, wave-dissipative, meso-tidal beach in southern Monterey Bay, CA in October 2015. The micro-meteorology study focus is to explore the momentum fluxes and turbulent kinetic energy influenced by the interaction between an intensive wave-breaking surf zone and a sandy beach associated with onshore & cross-shore winds, diurnal heating, and differences in ocean-air temperatures. The tower was deployed for approximately 1-month and experienced diurnal wind variations and synoptic storm events with winds measuring up to 10 m/s and an air temperature range of 5-28 oC. This beach environment was found to be primarily unstable in thermal stratification indicating that the air temperature is colder than underlying surface, either the ocean or the sandy beach. The drag coefficient was found to be dependent upon the atmospheric stability. Direct-estimates of atmospheric stability were obtained with the sonic anemometer. The direct estimates are a ratio of w*/u*, where the w*, vertically scaled buoyancy velocity, is greater than u*, horizontally scaled friction velocity. Hypotheses for the enhanced buoyancy are 1) diurnal heating of the sandy beach, 2) warmer ocean temperatures relative to air temperatures, and 3) the wave breaking within the surf zone. Further exploration into these hypotheses is conducted by using vertical tower sensor pairs for estimating the temporal variability of the mechanical shear production and buoyancy production terms in turbulent kinetic energy budget. These results are part of the Coastal Land Air Sea Interaction (CLASI) experiment.

Analysis of the Uncertainty in Wind Measurements from the Atmospheric Radiation Measurement Doppler Lidar during XPIA: Field Campaign Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Newsom, Rob

2016-03-01

In March and April of 2015, the ARM Doppler lidar that was formerly operated at the Tropical Western Pacific site in Darwin, Australia (S/N 0710-08) was deployed to the Boulder Atmospheric Observatory (BAO) for the eXperimental Planetary boundary-layer Instrument Assessment (XPIA) field campaign. The goal of the XPIA field campaign was to investigate methods of using multiple Doppler lidars to obtain high-resolution three-dimensional measurements of winds and turbulence in the atmospheric boundary layer, and to characterize the uncertainties in these measurements. The ARM Doppler lidar was one of many Doppler lidar systems that participated in this study. During XPIA themore » 300-m tower at the BAO site was instrumented with well-calibrated sonic anemometers at six levels. These sonic anemometers provided highly accurate reference measurements against which the lidars could be compared. Thus, the deployment of the ARM Doppler lidar during XPIA offered a rare opportunity for the ARM program to characterize the uncertainties in their lidar wind measurements. Results of the lidar-tower comparison indicate that the lidar wind speed measurements are essentially unbiased (~1cm s-1), with a random error of approximately 50 cm s-1. Two methods of uncertainty estimation were tested. The first method was found to produce uncertainties that were too low. The second method produced estimates that were more accurate and better indicators of data quality. As of December 2015, the first method is being used by the ARM Doppler lidar wind value-added product (VAP). One outcome of this work will be to update this VAP to use the second method for uncertainty estimation.« less

An Experimental Study of Synthetic Jets from Rectangular Orifices

NASA Technical Reports Server (NTRS)

Milanovic, Ivana M.

2003-01-01

During the past two summers Professor Milanovic conducted Wind tunnel experiments on steady jets-in-cross-flow and synthetic jets. In her anticipated visit during the upcoming summer, she will continue and complete the research on synthetic jets involving 2-dimensional orifices of different aspect ratio as well as inclined slots. In addition, experiments will be conducted on pulsatile jets-in-cross-flow. The pulsation will be provided via an oscillating valve at controllable frequencies. The experiment will involve mainly hot-wire anemometer measurements in the low-speed wind tunnel. Overall goal will be to obtain database and investigate flow control strategies. The research will be of fundamental nature.

The Analysis of Turbulent Flow by Hot Wire Signals. Ph.D. Thesis - Physikalische Ingenieurvissenschaft der Technischen Univ., 1981

NASA Technical Reports Server (NTRS)

Bartenwerfer, M.

1982-01-01

When measuring velocities in turbulent gas flow, approximation signal analysis with hot wire anemometers having one and two wire probes are used. A numeric test of standard analyses shows the resulting systemmatic error increases quickly with increasing turbulent intensity. Since it also depends on the turbulence structure, it cannot be corrected. The use of such probes is thus restricted to low turbulence. By means of three wire probes (in two dimensional flows with X wire probes) in principle, instantaneous values of velocity can be determined, and an asymmetric arrangement of wires has a theoretical advantage.

Hot Film Velocity Measurements Downstream of a Swept Backward-Facing Step

DTIC Science & Technology

1990-08-01

WR ~4’ nol w of tdl. O64" $l"uwe. suite 424 i lV~lZdO . 00 to effice at UAqeww0fl" S4 aud ’mpeom t, 0edUOM ’l~c 004 S~ a lleq~k Dc 2010). I. AGENCY USE ...Velocity measurements were made using a single component hot film anemometer. Results from this study indicate the following: the flow in the recirculation...velocity component parallel to the step face retains a finite magnitude. Coles’ law of the wall and wake was used to corralate the data from this study. The

Three dimensional flow field measurements of a 4:1 aspect ratio subsonic jet

NASA Technical Reports Server (NTRS)

Morrison, G. L.; Swan, D. H.

1989-01-01

Flow field measurements for a subsonic rectangular cold air jet with an aspect ratio of 4:1 (12.7 x 50.8 mm) at a Mach number of 0.09 and Re of 100,000 have been carried out using a three-dimensional laser Doppler anemometer system. Mean velocity measurements show that the jet width spreads more rapidly along the minor axis than along the major axis. The outward velocities, however, are not significantly different for the two axes, indicating the presence of enhanced mixing along the minor axis. The jet slowly changes from a rectangular jet to a circular jet as the flow progresses downstream.

A new method for aerodynamic test of high altitude propellers

NASA Astrophysics Data System (ADS)

Gong, Xiying; Zhang, Lin

A ground test system is designed for aerodynamic performance tests of high altitude propellers. The system is consisted of stable power supply, servo motors, two-component balance constructed by tension-compression sensors, ultrasonic anemometer, data acquisition module. It is loaded on a truck to simulate propellers' wind-tunnel test for different wind velocities at low density circumstance. The graphical programming language LABVIEW for developing virtual instrument is used to realize the test system control and data acquisition. Aerodynamic performance test of a propeller with 6.8 m diameter was completed by using this system. The results verify the feasibility of the ground test method.

Effect of Contraction on Turbulence and Temperature Fluctuations Generated by a Warm Grid

NASA Technical Reports Server (NTRS)

Mills, Robert R., Jr.; Corrsin, Stanley

1959-01-01

Hot-wire anemometer measurements were made of several statistical properties of approximately homogeneous and isotropic fields of turbulence and temperature fluctuations generated by a warm grid in a uniform airstream sent through a 4-to-1 contraction. These measurements were made both in the contraction and in the axisymmetric domain farther downstream. In addition to confirming the well-known turbulence anisotropy induced by strain, the data show effects on the skewnesses of both longitudinal velocity fluctuation (which has zero skewness in isotropic turbulence) and its derivative. The concomitant anisotropy in the temperature field accelerates the decay of temperature fluctuations.

An investigation of the motion of small particles as related to the formulation of zero gravity experiments. [experimental design using laser doppler velocimetry

NASA Technical Reports Server (NTRS)

Sastry, V. S.

1980-01-01

The nature of Brownian motion and historical theoretical investigations of the phenomemon are reviewed. The feasibility of using a laser anemometer to perform small particle experiments in an orbiting space laboratory was investigated using latex particles suspended in water in a plastic container. The optical equipment and the particle Doppler analysis processor are described. The values of the standard deviation obtained for the latex particle motion experiment were significantly large compared to corresponding velocity, therefore, their accuracy was suspect and no attempt was made to draw meaningful conclusions from the results.

Near wakes of advanced turbopropellers

NASA Technical Reports Server (NTRS)

Hanson, D. B.; Patrick, W. P.

1989-01-01

The flow in the wake of a model single rotation Prop-Fan rotor operating in a wind tunnel was traversed with a hot-wire anemometer system designed to determine the 3 periodic velocity components. Special data acquisition and data reduction methods were required to deal with the high data frequency, narrow wakes, and large fluctuating air angles in the tip vortex region. The model tip helical Mach number was 1.17, simulating the cruise condition. Although the flow field is complex, flow features such as viscous velocity defects, vortex sheets, tip vortices, and propagating acoustic pulses are clearly identified with the aid of a simple analytical wake theory.

Characteristics of turbulence in boundary layer with zero pressure gradient

NASA Technical Reports Server (NTRS)

Klebanoff, P S

1955-01-01

The results of an experimental investigation of a turbulent boundary layer with zero pressure gradient are presented. Measurements with the hot-wire anemometer were made of turbulent energy and turbulent shear stress, probability density and flattening factor of u-fluctuation (fluctuation in x-direction), spectra of turbulent energy and shear stress, and turbulent dissipation. The importance of the region near the wall and the inadequacy of the concept of local isotropy are demonstrated. Attention is given to the energy balance and the intermittent character of the outer region of the boundary layer. Also several interesting features of the spectral distribution of the turbulent motions are discussed.

Laser anemometer measurements in an annular cascade of core turbine vanes and comparison with theory

NASA Technical Reports Server (NTRS)

Goldman, L. J.; Seashultz, R. G.

1982-01-01

Laser measurements were made in an annular cascade of stator vanes operating at an exit critical velocity ratio of 0.78. Velocity and flow angles in the blade to blade plane were obtained at every 10 percent of axial chord within the passage and at 1/2 axial chord downstream of the vanes for radial positions near the hub, mean and tip. Results are presented in both plot and tabulated form and are compared with calculations from an inviscid, quasi three dimensional computer program. The experimental measurements generally agreed well with these theoretical calculations, an indication of the usefulness of this analytic approach.

Flow interaction and noise from a counter rotating propeller

NASA Technical Reports Server (NTRS)

Chung, Jin-Deog; Walls, James L.; Nagel, Robert T.

1991-01-01

The aerodynamic interaction between the forward and rear rotors in a counter rotating propeller (CRP) system, has been examined using a conditional sampling technique applied to three-dimensional thermal anemometer data. The technique effectively freezes the rotors in any desired relative position and provides the inter-rotor flow field. Axial, radial and circumferential mean flow between rotors is shown relative to the 'fixed' forward rotor for various 'fixed' aft rotor positions. Acoustic far field noise data have also been collected for the same operating conditions. The acoustic results are presented with emphasis on the blade passing frequencies and interaction tone of the CRP.

A wind model for an elevated STOL-port configuration

NASA Technical Reports Server (NTRS)

Peterka, J. A.; Cermak, J. E.

1974-01-01

Measurements of mean velocity magnitude and direction as well as three-dimensional turbulence intensity were made in the flow over a model of an elevated STOL-port. A 1:300 scale model was placed in a wind tunnel flow simulating the mean velocity profile and turbulence characteristics of atmospheric winds over a typical city environment excluding detailed wake structures of possible nearby buildings. Hot-wire anemometer measurements of velocity and turbulence were made along approach and departure paths of aircraft operating on the runway centerline and at specified lateral distances from the centerline. Approach flow directions simulated were 0 and 30 degrees to the runway centerline.

The effect of free-stream turbulence on heat transfer from a flat plate

NASA Technical Reports Server (NTRS)

Sugawara, Sugao; Sato, Takashi; Komatsu, Hiroyasu; Osaka, Hiroichi

1958-01-01

Turbulence was generated by using screens, and the turbulence percentage was measured by a hot-wire anemometer both in the boundary layer and the free stream. The local heat-transfer coefficient was measured at 12 locations along the plate for the cases of various turbulence levels. The transition Reynolds number from laminar to turbulent flow decreases as the main-stream turbulence level increases. In the range of laminar heat transfer the effect of turbulence in the main flow was not great, but in the range of turbulent heat transfer the heat-transfer coefficient increases according to the increase of turbulence.

Procedure for Determining Turbulence Length Scales Using Hotwire Anemometry

NASA Technical Reports Server (NTRS)

El-Gabry, Lamyaa A.; Thurman, Douglas R.; Poinsatte, Philip E.

2014-01-01

Hotwire anemometers are used to measure instantaneous velocity from which the mean velocity and the velocity fluctuation can be determined. Using a hotwire system, it is possible to deduce not only the velocity components and their fluctuation but to also analyze the energy spectra and from that the turbulence length scales. In this experiment, hotwire anemometry is used to measure the flow field turbulence for an array of film cooling holes. The objective of this paper is to document the procedure that is used to reduce the instantaneous velocity measurements to determine the turbulence length scales using data from the film-cooling experiments to illustrate the procedure.

A study of stability effects in forested terrain

NASA Astrophysics Data System (ADS)

Desmond, Cian J.; Watson, Simon

2014-12-01

Data from four well instrumented met masts located in heavily forested European sites in different locations and terrain types are examined. Seven stability metrics are applied to the data sets and a novel method is used to identify the metric which most consistently identifies stability events of importance for wind energy generation. It was found that the Obukhov length, as calculated by fast response sonic anemometer, provides the most reliable results in these highly complex sites. It was also found that non-neutral stabilities can be expected a significant portion of the time for wind speeds of less than 10 m/s at the considered sites.

Tests of a robust eddy correlation system for sensible heat flux

NASA Astrophysics Data System (ADS)

Blanford, J. H.; Gay, L. W.

1992-03-01

Sensible heat flux estimates from a simple, one-propeller eddy correlation system (OPEC) were compared with those from a sonic anemometer eddy correlation system (SEC). In accordance with similarity theory, the performance of the OPEC system improved with increasing height of the sensor above the surface. Flux totals from the two systems at sites with adequate fetch were in excellent agreement after frequency response corrections were applied. The propeller system appears suitable for long periods of unattended measurement. The sensible heat flux measurements can be combined with net radiation and soil heat flux measurements to estimate latent heat as a residual in the surface energy balance.

Results of tests CS4 and CS5 to investigate dynamic loads and pressures on 0.03-scale models (Ax1319-3/4 and 45-0) of mated 747 cam and space shuttle orbiter in the Boeing transonic wind tunnel

NASA Technical Reports Server (NTRS)

1976-01-01

A 0.03-scale model of the 747 CAM/Orbiter was tested in an 8 x 12 foot transonic wind tunnel. Dynamic loads, pressure, and empennage flow field data were obtained using pressure transducers, strain gages, and a split film anemometer. The test variables included Mach number, angle of attack, sideslip angle, orbiter tailcone on and off, orbiter partial tailcone, orbiter nozzle air scoops, orbiter body flap angle, and orbiter elevon angle.

A Method of Estimating Low Turbulence Levels in Near Real Time Using Laser Anemometry

NASA Technical Reports Server (NTRS)

Goldman, Louis J.; Seasholtz, Richard G.

2004-01-01

Laser anemometry was used to make two independent measurements of the flow velocity by capturing individual Doppler signals with high-speed digitizing boards. The two independent measurements were cross-correlated to reduce the contribution of photo detector shot noise on the frequency determination and subsequently on the turbulence estimate. In addition, criteria were developed to eliminate "bad" Doppler bursts from the data set, which then allowed reasonable low turbulence estimates to be made. The laser anemometer measurements were obtained at the inlet of an annular cascade and at the exit of a flow calibration nozzle and were compared with hot-wire data.

The structure of turbulence in fully developed pipe flow

NASA Technical Reports Server (NTRS)

Laufer, John

1954-01-01

Measurements, principally with a hot-wire anemometer, were made in fully developed turbulent flow in a 10-inch pipe at speeds of approximately 10 and 100 feet per second. Emphasis was placed on turbulence and conditions near the wall. The results include relevant mean and statistical quantities, such as Reynolds stresses, triple correlations, turbulent dissipation, and energy spectra. It is shown that rates of turbulent-energy production, dissipation, and diffusion have sharp maximums near the edge of the laminar sublayer and that there exist a strong movement of kinetic energy away from this point and an equally strong movement of pressure energy toward it.

Averaging interval selection for the calculation of Reynolds shear stress for studies of boundary layer turbulence.

NASA Astrophysics Data System (ADS)

Lee, Zoe; Baas, Andreas

2013-04-01

It is widely recognised that boundary layer turbulence plays an important role in sediment transport dynamics in aeolian environments. Improvements in the design and affordability of ultrasonic anemometers have provided significant contributions to studies of aeolian turbulence, by facilitating high frequency monitoring of three dimensional wind velocities. Consequently, research has moved beyond studies of mean airflow properties, to investigations into quasi-instantaneous turbulent fluctuations at high spatio-temporal scales. To fully understand, how temporal fluctuations in shear stress drive wind erosivity and sediment transport, research into the best practice for calculating shear stress is necessary. This paper builds upon work published by Lee and Baas (2012) on the influence of streamline correction techniques on Reynolds shear stress, by investigating the time-averaging interval used in the calculation. Concerns relating to the selection of appropriate averaging intervals for turbulence research, where the data are typically non-stationary at all timescales, are well documented in the literature (e.g. Treviño and Andreas, 2000). For example, Finnigan et al. (2003) found that underestimating the required averaging interval can lead to a reduction in the calculated momentum flux, as contributions from turbulent eddies longer than the averaging interval are lost. To avoid the risk of underestimating fluxes, researchers have typically used the total measurement duration as a single averaging period. For non-stationary data, however, using the whole measurement run as a single block average is inadequate for defining turbulent fluctuations. The data presented in this paper were collected in a field study of boundary layer turbulence conducted at Tramore beach near Rosapenna, County Donegal, Ireland. High-frequency (50 Hz) 3D wind velocity measurements were collected using ultrasonic anemometry at thirteen different heights between 0.11 and 1.62 metres above the bed. A technique for determining time-averaging intervals for a series of anemometers stacked in a close vertical array is presented. A minimum timescale is identified using spectral analysis to determine the inertial sub-range, where energy is neither produced nor dissipated but passed down to increasingly smaller scales. An autocorrelation function is then used to derive a scaling pattern between anemometer heights, which defines a series of averaging intervals of increasing length with height above the surface. Results demonstrate the effect of different averaging intervals on the calculation of Reynolds shear stress and highlight the inadequacy of using the total measurement duration as a single block average. Lee, Z. S. & Baas, A. C. W. (2012). Streamline correction for the analysis of boundary layer turbulence. Geomorphology, 171-172, 69-82. Treviño, G. and Andreas, E.L., 2000. Averaging Intervals For Spectral Analysis Of Nonstationary Turbulence. Boundary-Layer Meteorology, 95(2): 231-247. Finnigan, J.J., Clement, R., Malhi, Y., Leuning, R. and Cleugh, H.A., 2003. Re-evaluation of long-term flux measurement techniques. Part I: Averaging and coordinate rotation. Boundary-Layer Meteorology, 107(1): 1-48.

Expanding Spatial and Temporal Coverage of Arctic CH4 and CO2 Fluxes

NASA Astrophysics Data System (ADS)

Murphy, P.; Oechel, W. C.; Moreaux, V.; Losacco, S.; Zona, D.

2013-12-01

Carbon storage and exchange in Arctic ecosystems is the subject of intensive study focused on determining rates, controls, and mechanisms of CH4 and CO2 fluxes. The Arctic contains more than 1 Gt of Carbon in the upper meter of soil, both in the active layer and permafrost (Schuur et al., 2008; Tarnocai et al., 2009). However, the annual pattern and controls on the release of CH4 is inadequately understood in Arctic tundra ecosystems. Annual methane budgets are poorly understood, and very few studies measure fluxes through the freeze-up cycle during autumn months (Mastepanov et al., 2008; Mastepanov et al., 2010; Sturtevant et al., 2012). There is no known, relatively continuous, CH4 flux record for the Arctic. Clearly, the datasets that currently exist for budget calculations and model parameterization and verification are inadequate. This is likely due to the difficult nature of flux measurements in the Arctic. In September 2012, we initiated a research project towards continuous methane flux measurements along a latitudinal transect in Northern Alaska. The eddy-covariance (EC) technique is challenging in such extreme weather conditions due to the effects of ice formation and precipitation on instrumentation, including gas analyzers and sonic anemometers. The challenge is greater in remote areas of the Arctic, when low power availability and limited communication can lead to delays in data retrieval or data loss. For these reasons, a combination of open- and closed-path gas analyzers, and several sonic anemometers (including one with heating), have been installed on EC towers to allow for cross-comparison and cross-referencing of calculated fluxes. Newer instruments for fast CH4 flux determination include: the Los Gatos Research Fast Greenhouse Gas Analyzer and the Li-Cor LI-7700. We also included the self-heated Metek Class-A uSonic-3 Anemometer as a new instrument. Previously existing instruments used for comparison include the Li-Cor LI-7500; Li-Cor LI-7200; Gill WindmasterPro; Gill R3; Campbell Scientific CSAT-3, and METEK USA-1. To prevent gaps in data due to poor weather, we developed a temperature control system to allow de-icing of the sonic instrument based on data quality. Enclosures were also created to support equipment that was not designed for outdoor use. A similar temperature control system was implemented to maintain stable conditions in the enclosures. Five existing EC towers on the north slope of Alaska, in Barrow, Atqasuk, and Ivotuk, are used to obtain CH4 and CO2 fluxes, and allow a comparison of fluxes across sensor type and design. Here we present the instrument set-up and some of the preliminary eddy covariance CH4 and CO2 flux data, which might prove very useful as guidelines for further flux measurements in northern high latitudes.

Fringe localization requirements for three-dimensional flow visualization of shock waves in diffuse-illumination double-pulse holographic interferometry

NASA Technical Reports Server (NTRS)

Decker, A. J.

1982-01-01

A theory of fringe localization in rapid-double-exposure, diffuse-illumination holographic interferometry was developed. The theory was then applied to compare holographic measurements with laser anemometer measurements of shock locations in a transonic axial-flow compressor rotor. The computed fringe localization error was found to agree well with the measured localization error. It is shown how the view orientation and the curvature and positional variation of the strength of a shock wave are used to determine the localization error and to minimize it. In particular, it is suggested that the view direction not deviate from tangency at the shock surface by more than 30 degrees.

Shear layer excitation, experiment versus theory

NASA Technical Reports Server (NTRS)

Bechert, D. W.; Stahl, B.

1984-01-01

The acoustical excitation of shear layers is investigated. Acoustical excitation causes the so-called orderly structures in shear layers and jets. Also, the deviations in the spreading rate between different shear layer experiments are due to the same excitation mechanism. Measurements in the linear interaction region close to the edge from which the shear layer is shed are examined. Two sets of experiments (Houston 1981 and Berlin 1983/84) are discussed. The measurements were carried out with shear layers in air using hot wire anemometers and microphones. The agreement between these measurements and the theory is good. Even details of the fluctuating flow field correspond to theoretical predictions, such as the local occurrence of negative phase speeds.

Effects of blade-vane ratio and rotor-stator spacing of fan noise with forward velocity

NASA Astrophysics Data System (ADS)

Woodward, R. P.; Glaser, F. W.

1981-08-01

A research fan stage was acoustically tested in an anechoic wind tunnel with a 41 m/sec tunnel flow. Two stator vane numbers giving cut-on and cut-off conditions were tested at three rotor-stator spacings ranging from about 0.5 to 2.0 rotor chords. These two stators were designed for similar aerodynamic performance. Hot film anemometer turbulence measurements were made at the leading edge of the stator for each spacing. The cut-off criterion strongly controlled the fundamental tone level at all spacings. The trends with spacing of the wake defect upwash component at the stator tip showed good agreement with the corresponding cut-on acoustic tone levels.

Estimation of the sea surface's two-scale backscatter parameters

NASA Technical Reports Server (NTRS)

Wentz, F. J.

1978-01-01

The relationship between the sea-surface normalized radar cross section and the friction velocity vector is determined using a parametric two-scale scattering model. The model parameters are found from a nonlinear maximum likelihood estimation. The estimation is based on aircraft scatterometer measurements and the sea-surface anemometer measurements collected during the JONSWAP '75 experiment. The estimates of the ten model parameters converge to realistic values that are in good agreement with the available oceanographic data. The rms discrepancy between the model and the cross section measurements is 0.7 db, which is the rms sum of a 0.3 db average measurement error and a 0.6 db modeling error.

Wind shear over the Nice Côte d'Azur airport: case studies

NASA Astrophysics Data System (ADS)

Boilley, A.; Mahfouf, J.-F.

2013-09-01

The Nice Côte d'Azur international airport is subject to horizontal low-level wind shears. Detecting and predicting these hazards is a major concern for aircraft security. A measurement campaign took place over the Nice airport in 2009 including 4 anemometers, 1 wind lidar and 1 wind profiler. Two wind shear events were observed during this measurement campaign. Numerical simulations were carried out with Meso-NH in a configuration compatible with near-real time applications to determine the ability of the numerical model to predict these events and to study the meteorological situations generating an horizontal wind shear. A comparison between numerical simulation and the observation dataset is conducted in this paper.

Wind shear over the Nice Côte d'Azur airport: case studies

NASA Astrophysics Data System (ADS)

Boilley, A.; Mahfouf, J.-F.

2013-04-01

The Nice Côte d'Azur international airport is subject to horizontal low-level wind shears. Detecting and predicting these hazards is a major concern for aircraft security. A measurement campaign took place over the Nice airport in 2009 including 4 anemometers, 1 wind lidar and 1 wind profiler. Two wind shear events were observed during this measurement campaign. Numerical simulations were carried out with Meso-NH in a configuration compatible with near-real time applications to determine the ability of the numerical model to predict these events and to study the meteorological situations generating a horizontal wind shear. A comparison between numerical simulation and the observation dataset is conducted in this paper.

Event-based measurement of boundary-layer winds and topographic effects with a small unmanned aircraft system (sUas)

NASA Astrophysics Data System (ADS)

Riddell, K.; Hugenholtz, C.

2012-12-01

Numerical models are invaluable tools for developing and testing hypotheses about interactions and feedbacks between wind and topography. However, field-based measurements are equally important for building and enhancing confidence in model output. Several field methods are available, including conventional approaches using tall masts equipped with an array of anemometers, as well as weather balloons, but few methods are able to match the level of detail available in model simulations of topographically-modified windflow. Here we propose an alternative method that may enhance numerical models. The method involves a small unmanned aircraft system (sUas) equipped with a meteorological sensor payload. The sUas is a two blade helicopter that weighs 5.5 kg, and has a length of 1.32 m. We designed a simple measurement and control system using an Arduino micro-controller, which acquired measurements at pre-defined coordinates autonomously. The entire survey was pre-configured and uploaded to the aircraft, effectively avoiding the need for manual aircraft operation and data collection. We collected raw measurements at each waypoint, yielding a point cloud of windspeed data. During test flights the sUas was able to maintain a stable position (± 0.6 m vertical and horizontal) in wind speeds up to 50 km/h. We used the raw data to map the wind speed-up ratio relative to a reference anemometer. Although it would be preferable to acquire continuous measurements at each waypoint, the sUas method only provides a snapshot of wind at each location. However, despite this limitation, the sUas does fill a void in terms of spatial measurements within the boundary layer. It may be possible to enhance this method in the future through deployment of sUas swarms that measure wind concurrently at many locations. Furthermore, other sensors can be deployed on sUas for measuring aeolian processes such as dust.

A Comparison of Wind Speed Data from Mechanical and Ultrasonic Anemometers

NASA Technical Reports Server (NTRS)

Short, D.; Wells, L.; Merceret, F.; Roeder, W. P.

2006-01-01

This study compared the performance of mechanical and ultrasonic anemometers at the Eastern Range (ER; Kennedy Space Center and Cape Canaveral Air Force Station on Florida's Atlantic coast) and the Western Range (WR; Vandenberg Air Force Base on California's Pacific coast). Launch Weather Officers, forecasters, and Range Safety analysts need to understand the performance of wind sensors at the ER and WR for weather warnings, watches, advisories, special ground processing operations, launch pad exposure forecasts, user Launch Commit Criteria (LCC) forecasts and evaluations, and toxic dispersion support. The current ER and WR weather tower wind instruments are being changed from the current propeller-and-vane (ER) and cup-and-vane (WR) sensors to ultrasonic sensors through the Range Standardization and Automation (RSA) program. The differences between mechanical and ultrasonic techniques have been found to cause differences in the statistics of peak wind speed in previous studies. The 45th Weather Squadron (45 WS) and the 30th Weather Squadron (30 WS) requested the Applied Meteorology Unit (AMU) to compare data between RSA and current sensors to determine if there are significant differences. Approximately 3 weeks of Legacy and RSA wind data from each range were used in the study, archived during May and June 2005. The ER data spanned the full diurnal cycle, while the WR data was confined to 1000-1600 local time. The sample of 1-minute data from numerous levels on 5 different towers on each range totaled more than 500,000 minutes of data (482,979 minutes of data after quality control). The 10 towers were instrumented at several levels, ranging from 12 ft to 492 ft above ground level. The RSA sensors were collocated at the same vertical levels as the present sensors and typically within 15 ft horizontally of each another. Data from a total of 53 RSA ultrasonic sensors, collocated with present sensors were compared. The 1-minute average wind speed/direction and the 1-second peak wind speed/direction were compared.

Ground Deposition of Liquid Droplets Released from a Point Source in the Atmospheric Surface Layer.

NASA Astrophysics Data System (ADS)

Panneton, Bernard

1989-09-01

A series of field experiments is presented in which the ground deposition of liquid droplets, 120 and 150 μm in diameter, released from a point source at 7 meters above the ground level, was measured. A detailed description of the experimental technique is provided, and the results are presented and compared to the predictions of a few models. A new rotating droplet generator is described. Droplets are produced by the forced breakup of capillary liquid jets and droplet coalescence is inhibited by the rotational motion of the spray head. A system for analyzing spray samples has been developed. This is a specialized image analysis system based on an electronic digitizing camera which measures the area and perimeter of stains left by dyed droplets collected on Kromekote^{rm TM } cards. A complete set of meteorological data supports the ground-deposition data. The turbulent air velocities at two levels above the ground and the temperature of the air at one level were measured with one sonic anemometer and a sonic anemometer-thermometer. The vertical heat and momentum fluxes were estimated using the eddy-correlation technique. The two-dimensional deposition patterns are presented in the form of plots of contours of constant density, normalized arcwise distributions and crosswind integrated distributions. The arcwise distributions follow a Gaussian distribution whose standard deviation is evaluated using a modified Pasquill's beta technique. Models of the crosswind integrated deposit from Godson, Csanady, Walker, Bache and Sayer, and Wilson et al are evaluated. The results indicate that the Wilson et al random walk model is adequate for predicting the ground deposition of the 150 μm droplets. In one case, where the ratio of the droplet settling velocity to the mean wind speed was largest, Walker's model proved to be adequate. Otherwise, none of the models were acceptable in light of our experimental data.

On the spatial coherence of temperature within and above a vineyard under drainage conditions

NASA Astrophysics Data System (ADS)

Everard, K.; Giometto, M. G.; Christen, A.; Oldroyd, H. J.; Parlange, M. B.

2017-12-01

We show that turbulent exchange within vineyards under nighttime drainage conditions is controlled by large-scale coherent structures arising from a mixing-layer type instability at the canopy top, h. A combination of measurements and large-eddy simulations (LESs) are here used to characterize the onset and development of such structures as a function of the approaching wind angle over an organized canopy during drainage flows. Measurements were carried out over a west-facing 7° vineyard slope near Oliver, BC, Canada in the Okanagan Valley between July 5 and July 22, 2016. The vineyard canopy had an average height of h = 2.3 m, with parallel rows oriented in the local downslope direction (i.e. east-west). The set-up consisted of an array of five vertically arranged ultrasonic anemometers at z/h = 0.19, 0.39, 0.65, 1.02, and 2.06, and a 2-D grid of 40 fine-wire thermocouples arranged at the same heights as the ultrasonic anemometer array on 8 separate masts extending in the upslope direction at locations up to x/h = 13.91 from the flux tower. To complement observations, pressure-driven open-channel flow LESs are performed over a regular domain where vegetation is accounted for via a space dependent drag force. The drainage flow regime is emulated via a tuned pressure-gradient forcing, and different approaching wind angles are considered. Linear stability analyses show that the most unstable mode at the canopy top strongly depends on the approaching wind angle. Space-lagged correlations from measurements show that the lifetime of such eddies within the canopy also depends on the approaching wind direction, with longer lifetimes observed when wind angles are directed along the vine-rows. LESs are compared with measured quantities to ensure matching, and then used to investigate in detail the influence of the above-canopy wind vectors on eddy lifetimes. The impact of the observed coherent structures on momentum and heat exchange coefficients are also discussed.

Design, Validation, and Testing of a Hot-Film Anemometer for Hypersonic Flow

NASA Astrophysics Data System (ADS)

Sheplak, Mark

The application of constant-temperature hot-film anemometry to hypersonic flow has been reviewed and extended in this thesis. The objective of this investigation was to develop a measurement tool capable of yielding continuous, high-bandwidth, quantitative, normal mass-flux and total -temperature measurements in moderate-enthalpy environments. This research has produced a probe design that represents a significant advancement over existing designs, offering the following improvements: (1) a five-fold increase in bandwidth; (2) true stagnation-line sensor placement; (3) a two order-of-magnitude decrease in sensor volume; and (4) over a 70% increase in maximum film temperature. These improvements were achieved through substrate design, sensor placement, the use of high-temperature materials, and state -of-the-art microphotolithographic fabrication techniques. The experimental study to characterize the probe was performed in four different hypersonic wind tunnels at NASA-Langley Research Center. The initial test consisted of traversing the hot film through a Mach 6, flat-plate, turbulent boundary layer in air. The detailed static-calibration measurements that followed were performed in two different hypersonic flows: a Mach 11 helium flow and Mach 6 air flow. The final test of this thesis consisted of traversing the probe through the Mach 6 wake of a 70^ circ blunt body. The goal of this test was to determine the state (i.e., laminar or turbulent) of the wake. These studies indicate that substrate conduction effects result in instrumentation characteristics that prevent the hot-film anemometer from being used as a quantitative tool. The extension of this technique to providing quantitative information is dependent upon the development of lower thermal-conductivity substrate materials. However, the probe durability, absence of strain gauging, and high bandwidth represent significant improvements over the hot-wire technique for making qualitative measurements. Potential uses for this probe are: frequency identification for resonant flows, transition studies, turbulence detection for quiet-tunnel development and reattaching turbulent shear flows, and qualitative turbulence studies of shock-wave/turbulent boundary layer interactions.

Evaluation of probe-induced flow distortion of Campbell CSAT3 sonic anemometers by numerical simulation

NASA Astrophysics Data System (ADS)

Mauder, M.; Huq, S.; De Roo, F.; Foken, T.; Manhart, M.; Schmid, H. P. E.

2017-12-01

The Campbell CSAT3 sonic anemometer is one of the most widely used instruments for eddy-covariance measurement. However, conflicting estimates for the probe-induced flow distortion error of this instrument have been reported recently, and those error estimates range between 3% and 14% for the measurement of vertical velocity fluctuations. This large discrepancy between the different studies can probably be attributed to the different experimental approaches applied. In order to overcome the limitations of both field intercomparison experiments and wind tunnel experiments, we propose a new approach that relies on virtual measurements in a large-eddy simulation (LES) environment. In our experimental set-up, we generate horizontal and vertical velocity fluctuations at frequencies that typically dominate the turbulence spectra of the surface layer. The probe-induced flow distortion error of a CSAT3 is then quantified by this numerical wind tunnel approach while the statistics of the prescribed inflow signal are taken as reference or etalon. The resulting relative error is found to range from 3% to 7% and from 1% to 3% for the standard deviation of the vertical and the horizontal velocity component, respectively, depending on the orientation of the CSAT3 in the flow field. We further demonstrate that these errors are independent of the frequency of fluctuations at the inflow of the simulation. The analytical corrections proposed by Kaimal et al. (Proc Dyn Flow Conf, 551-565, 1978) and Horst et al. (Boundary-Layer Meteorol, 155, 371-395, 2015) are compared against our simulated results, and we find that they indeed reduce the error by up to three percentage points. However, these corrections fail to reproduce the azimuth-dependence of the error that we observe. Moreover, we investigate the general Reynolds number dependence of the flow distortion error by more detailed idealized simulations.

Assessing Near-surface Heat, Water Vapor and Carbon Dioxide Exchange Over a Coastal Salt-marsh

NASA Astrophysics Data System (ADS)

Bogoev, I.; O'Halloran, T. L.; LeMoine, J.

2017-12-01

Coastal ecosystems play an important role in mitigating the effects of climate change by storing significant quantities of carbon. A growing number of studies suggest that vegetated estuarine habitats, specifically salt marshes, have high long-term rates of carbon sequestration, perhaps even higher than mature tropical and temperate forests. Large amounts of carbon, accumulated over thousands of years, are stored in the plant materials and sediment. Improved understanding of the factors that control energy and carbon exchange is needed to better guide restoration and conservation management practices. To that end, we recently established an observation system to study marsh-atmosphere interactions within the North Inlet-Winyah Bay National Estuarine Research Reserve. Near-surface fluxes of heat, water vapor (H2O) and carbon dioxide (CO2) were measured by an eddy-covariance system consisting of an aerodynamic open-path H2O / CO2 gas analyzer with a spatially integrated 3D sonic anemometer/thermometer (IRGASON). The IRGASON instrument provides co-located and highly synchronized, fast response H2O, CO2 and air- temperature measurements, which eliminates the need for spectral corrections associated with the separation between the sonic anemometer and the gas analyzer. This facilitates calculating the instantaneous CO2 molar mixing ratio relative to dry air. Fluxes computed from CO2 and H2O mixing ratios, which are conserved quantities, do not require post-processing corrections for air-density changes associated with temperature and water vapor fluctuations. These corrections are particularly important for CO2, because they could be even larger than the measured flux. Here we present the normalized frequency spectra of air temperature, water vapor and CO2, as well as their co-spectra with the co-located vertical wind. We also show mean daily cycles of sensible, latent and CO2 fluxes and analyze correlations with air/water temperature, wind speed and light availability.

Operation in the turbulent jet field of a linear array of multiple rectangular jets using a two-dimensional jet (Variation of mean velocity field)

NASA Astrophysics Data System (ADS)

Fujita, Shigetaka; Harima, Takashi

2016-03-01

The mean flowfield of a linear array of multiple rectangular jets run through transversely with a two-dimensional jet, has been investigated, experimentally. The object of this experiment is to operate both the velocity scale and the length scale of the multiple rectangular jets using a two-dimensional jet. The reason of the adoption of this nozzle exit shape was caused by the reports of authors in which the cruciform nozzle promoted the inward secondary flows strongly on both the two jet axes. Aspect ratio of the rectangular nozzle used in this experiment was 12.5. Reynolds number based on the nozzle width d and the exit mean velocity Ue (≅ 39 m / s) was kept constant 25000. Longitudinal mean velocity was measured using an X-array Hot-Wire Probe (lh = 3.1 μm in diameter, dh = 0.6 mm effective length : dh / lh = 194) operated by the linearized constant temperature anemometers (DANTEC), and the spanwise and the lateral mean velocities were measured using a yaw meter. The signals from the anemometers were passed through the low-pass filters and sampled using A.D. converter. The processing of the signals was made by a personal computer. Acquisition time of the signals was usually 60 seconds. From this experiment, it was revealed that the magnitude of the inward secondary flows on both the y and z axes in the upstream region of the present jet was promoted by a two-dimensional jet which run through transversely perpendicular to the multiple rectangular jets, therefore the potential core length on the x axis of the present jet extended 2.3 times longer than that of the multiple rectangular jets, and the half-velocity width on the rectangular jet axis of the present jet was suppressed 41% shorter compared with that of the multiple rectangular jets.

Assessing the Impact of Different Measurement Time Intervals on Observed Long-Term Wind Speed Trends

NASA Astrophysics Data System (ADS)

Azorin-Molina, C.; Vicente-Serrano, S. M.; McVicar, T.; Jerez, S.; Revuelto, J.; López Moreno, J. I.

2014-12-01

During the last two decades climate studies have reported a tendency toward a decline in measured near-surface wind speed in some regions of Europe, North America, Asia and Australia. This weakening in observed wind speed has been recently termed "global stilling", showing a worldwide average trend of -0.140 m s-1 dec-1 during last 50-years. The precise cause of the "global stilling" remains largely uncertain and has been hypothetically attributed to several factors, mainly related to: (i) an increasing surface roughness (i.e. forest growth, land use changes, and urbanization); (ii) a slowdown in large-scale atmospheric circulation; (iii) instrumental drifts and technological improvements, maintenance, and shifts in measurements sites and calibration issues; (iv) sunlight dimming due to air pollution; and (v) astronomical changes. This study proposed a novel investigation aimed at analyzing how different measurement time intervals used to calculate a wind speed series can affect the sign and magnitude of long-term wind speed trends. For instance, National Weather Services across the globe estimate daily average wind speed using different time intervals and formulae that may affect the trend results. Firstly, we carried out a comprehensive review of wind studies reporting the sign and magnitude of wind speed trend and the sampling intervals used. Secondly, we analyzed near-surface wind speed trends recorded at 59 land-based stations across Spain comparing monthly mean wind speed series obtained from: (a) daily mean wind speed data averaged from standard 10-min mean observations at 0000, 0700, 1300 and 1800 UTC; and (b) average wind speed of 24 hourly measurements (i.e., wind run measurements) from 0000 to 2400 UTC. Thirdly and finally, we quantified the impact of anemometer drift (i.e. bearing malfunction) by presenting preliminary results (1-year of paired measurements) from a comparison of one new anemometer sensor against one malfunctioned anenometer sensor due to old bearings.

Multifractal Analysis of Velocity Vector Fields and a Continuous In-Scale Cascade Model

NASA Astrophysics Data System (ADS)

Fitton, G.; Tchiguirinskaia, I.; Schertzer, D.; Lovejoy, S.

2012-04-01

In this study we have compared the multifractal analyses of small-scale surface-layer wind velocities from two different datasets. The first dataset consists of six-months of wind velocity and temperature measurements at the heights 22, 23 and 43m. The measurements came from 3D sonic anemometers with a 10Hz data output rate positioned on a mast in a wind farm test site subject to wake turbulence effects. The location of the test site (Corsica, France) meant the large scale structures were subject to topography effects that therefore possibly caused buoyancy effects. The second dataset (Germany) consists of 300 twenty minute samples of horizontal wind velocity magnitudes simultaneously recorded at several positions on two masts. There are eight propeller anemometers on each mast, recording velocity magnitude data at 2.5Hz. The positioning of the anemometers is such that there are effectively two grids. One grid of 3 rows by 4 columns and a second of 5 rows by 2 columns. The ranges of temporal scale over which the analyses were done were from 1 to 103 seconds for both datasets. Thus, under the universal multifractal framework we found both datasets exhibit parameters α ≈ 1.5 and C1 ≈ 0.1. The parameters α and C1, measure respectively the multifractality and mean intermittency of the scaling field. A third parameter, H, quantifies the divergence from conservation of the field (e.g. H = 0 for the turbulent energy flux density). To estimate the parameters we used the ratio of the scaling moment function of the energy flux and of the velocity increments. This method was particularly useful when estimating the parameter α over larger scales. In fact it was not possible to obtain a reasonable estimate of alpha using the usual double trace moment method. For each case the scaling behaviour of the wind was almost isotropic when the scale ranges remained close to the sphero-scale. For the Corsica dataset this could be seen by the agreement of the spectral exponents of the order of 1.5 for all three components. Given we have only the horizontal wind components over a grid for the Germany dataset the comparable probability distributions of horizontal and vertical velocity increments shows the field is isotropic. The Germany dataset allows us to compare the spatial velocity increments with that of the temporal. We briefly mentioned above that the winds in Corsica were subject to vertical forcing effects over large scales. This means the velocity field scaled as 11/5 i.e. Bolgiano-Obukhov instead of Kolmogorov's. To test this we were required to invoke Taylor's frozen turbulence hypothesis since the data was a one point measurement. Having vertical and horizontal velocity increments means we can further justify the claims of an 11/5 scaling law for vertical shears of the velocity and test the validity of the Taylor's hypothesis. We used the results to first simulate the velocity components using continuous in-scale cascades and then discuss the reconstruction of the full vector fields.

United States Naval Academy Polar Science Program's Visual Arctic Observing Buoys; The IceGoat

NASA Astrophysics Data System (ADS)

Woods, J. E.; Clemente-Colon, P.; Nghiem, S. V.; Rigor, I.; Valentic, T. A.

2012-12-01

The U.S. Naval Academy Oceanography Department currently has a curriculum based Polar Science Program (USNA PSP). Within the PSP there is an Arctic Buoy Program (ABP) student research component that will include the design, build, testing and deployment of Arctic Buoys. Establishing an active, field-research program in Polar Science will greatly enhance Midshipman education and research, as well as introduce future Naval Officers to the Arctic environment. The Oceanography Department has engaged the USNA Ocean Engineering, Systems Engineering, Aerospace Engineering, and Computer Science Departments and developed a USNA Visual Arctic Observing Buoy, IceGoat1, which was designed, built, and deployed by midshipmen. The experience gained through Polar field studies and data derived from these buoys will be used to enhance course materials and laboratories and will also be used directly in Midshipman independent research projects. The USNA PSP successfully deployed IceGoat1 during the BROMEX 2012 field campaign out of Barrow, AK in March 2012. This buoy reports near real-time observation of Air Temperature, Sea Temperature, Atmospheric Pressure, Position and Images from 2 mounted webcams. The importance of this unique type of buoy being inserted into the U.S. Interagency Arctic Buoy Program and the International Arctic Buoy Programme (USIABP/IABP) array is cross validating satellite observations of sea ice cover in the Arctic with the buoys webcams. We also propose to develop multiple sensor packages for the IceGoat to include a more robust weather suite, and a passive acoustic hydrophone. Remote cameras on buoys have provided crucial qualitative information that complements the quantitative measurements of geophysical parameters. For example, the mechanical anemometers on the IABP Polar Arctic Weather Station at the North Pole Environmental Observatory (NPEO) have at times reported zero winds speeds, and inspection of the images from the NPEO cameras have showed frosting on the camera during these same periods indicating that the anemometer has temporarily frozen up. Later when the camera lens clears, the anemometers resume providing reasonable wind speeds. The cameras have also provided confirmation of the onset of melt and freeze, and indications of cloudy and clear skies. USNA PSP will monitor meteorological and oceanographic parameters of the Arctic environment remotely via its own buoys. Web cameras will provide near real time visual observations of the buoys current positions, allowing for instant validation of other remotes sensors and modeled data. Each buoy will be developed with at a minimum a meteorological sensor package in accordance with IABP protocol (2m Air Temp, SLP). Platforms will also be developed with new sensor packages to possibly include, wind speed, ice temperature, sea ice thickness, underwater acoustics, and new communications suites (Iridium, Radio). The uniqueness of the IceGoat is that it is based on the new AXIB buoy designed by LBI, Inc. that has a proven record of being able to survive in the harsh marginal ice zone environment. IceGoat1 will be deployed in the High Arctic during the USCGC HEALY cruise in late August 2012.

Role of post-field raw data processing: a multi-site and full factorial uncertainty analysis

NASA Astrophysics Data System (ADS)

Sabbatini, Simone; Fratini, Gerardo; Arriga, Nicola; Papale, Dario

2013-04-01

Uncertainties in the Eddy Covariance flux measurements are a fundamental issue not yet completely solved. The complexity of the method, involving many, not standardized processing steps is one among the source of such uncertainty. The goal of our work is to quantify uncertainties deriving from post-field raw data processing, needed to calculate fluxes from collected turbulence measurements. The methodology we propose is a full-factorial design, performed using as factors a number of selected processing steps. We applied this approach to 15 European flux stations representative of different ecosystems (forests, croplands and grasslands), climates (Mediterranean, Nordic, arid and humid) and instrumental setups (e.g. open vs. closed path systems). Then we processed one year of raw data from each of the selected stations so as to cover all possible combinations of the available options (levels) relative to all the critical processing steps, i.e: angle of attack correction; coordinate rotation; trend removal; time lag compensation; low- and high- frequency spectral correction; correction for air density fluctuations; and length of the flux averaging interval. The software we used is EddyPro™. At last we calculated the cumulative NEE (response) for each process, and performed an analysis of variance of the factorial design. In addition to the global uncertainty, from this statistical approach we obtain information about the factors that most contribute to the uncertainties, and also the most relevant two-level interactions between factors. Here we present partial results from the first sites analysed. For the beech forest of Sorø, Denmark (Gill R2 anemometer and closed path GA, tube length = 50 m) the factor that most contributes to the variance in 2007 (40.4 %) is the trend removal, with an uncertainty of 7.5%. It is followed by the angle of attack (16.1 % of the total variability, uncertainty 3.5 %) and the interaction between trend removal and time lag compensation (11.42 % of variance explained). The overall uncertainty is about 8.7 % (cumulative NEE = -440.22 ± 38.36 g C m-2 year-1). The Oak forest of Roccarespampani, Italy (Metek anemometer and closed path GA, tube length = 22 m) was a sink in 2006. The coordinate rotation has the main influence on the variance (46.14 %, against an uncertainty of 4 %), then comes the average interval with 17.34 % (unc. 2 %), and their interaction (9.70 % of variance explained). The total uncertainty is 4.8 % (NEE = -515.19 ± 24.7 g C m-2 year-1). The mixed forest of Norunda, Sweden, in the year 2008 is a source of CO2 (Metek anemometer and closed path GA, tube length = 8 m). For this site we found a strong influence of the coordinate rotation (74.02 %, with an uncertainty of 32.5 %), while the trend removal explains the 17.41 % of the variance (unc. 15 %), against a total uncertainty of about 26.8 % (155.04 ± 41.50 g C m-2 year-1).

An eddy covariance study of a spruce beetle outbreak on summertime evapotranspiration and ecosystem CO2 exchange and winter sublimation dynamics

NASA Astrophysics Data System (ADS)

Frank, John Michael

Water and carbon cycles are important from ecosystem to global scales because of their feedbacks with climate change and natural disturbance. In order to quantify both primary and compensating responses in an ecosystem under disturbance, an approach that observes the ecosystem in its entirety is preferred. In recent decades, the eddy covariance technique has become ubiquitous in modern ecosystem studies because its fundamental measurement scale integrates across an ecosystem. Yet, across flux networks a trend towards energy imbalance has implicated a systematic bias in these measurements that has no mechanistic explanation. This dissertation concentrates on a historical transducer shadowing correction for sonic anemometers, the fundamental instrument in eddy covariance studies, and whether the omission of it can explain these underestimated ecosystem fluxes. It then focuses on the response of water and carbon processes in a subalpine spruce-fir forest in southeastern Wyoming, USA that experienced 80% forested basal area mortality following a spruce beetle outbreak. To evaluate an uncertainty in eddy covariance measurements, a novel experiment is devised to test the consistency to which an omnidirectional sonic anemometer can measure the three dimensions, to compare of the effect of different designs and different manufacturers to link an underestimate in vertical wind velocity to the lack of transducer shadowing correction, and to construct a Bayesian model to estimate the three dimensional shadowing correction required to fix the problem. Results show that at the 60% of ecosystem flux sites in North American that use this equipment, their ecosystem flux measurements are probably underestimated by 8-12%. During the growing season, the change in ecosystem processes due to disturbance are explained through the physiological response of dying spruce trees and their observed mortality. Evapotranspiration declines immediately following the attack because of hydraulic failure due to the spruce beetle associated blue-stain fungi. In response, impacted spruce trees regulate their stomatal conductance and ecosystem photosynthesis declines slightly. A few years later these trees die and ecosystem photosynthesis falls by 50%. During winter, a Bayesian analysis shows a fundamental preference for ecosystem sublimation to originate from the canopy, which in combination with the loss of canopy and limited ability to intercept fresh snowfall, has led to substantially less total sublimation because of the outbreak. Because the ecosystem’s response to disturbance can be explained through physiological processes at the organism scale, this work provides an opportunity to test hypotheses about bottom up approaches and offers new insights into hydrological and ecological models. The anemometer error investigation and Bayesian analyses provide new tools to examine ecological phenomena that are uncertain or where no standard of “truth” is available. By demonstrating an ecosystem response that can be explained by the dominate species, implementing a two source energy and canopy mass model to explain ecosystem sublimation, investigating a prevalent error in the majority of eddy covariance systems, and advancing statistical analysis from which all of these processes can be inferred, this work as a whole is applicable to nearly all terrestrial ecosystem studies.

Advanced Exploration Technologies: Micro and Nano Technologies Enabling Space Missions in the 21st Century

NASA Technical Reports Server (NTRS)

Krabach, Timothy

1998-01-01

Some of the many new and advanced exploration technologies which will enable space missions in the 21st century and specifically the Manned Mars Mission are explored in this presentation. Some of these are the system on a chip, the Computed-Tomography imaging Spectrometer, the digital camera on a chip, and other Micro Electro Mechanical Systems (MEMS) technology for space. Some of these MEMS are the silicon micromachined microgyroscope, a subliming solid micro-thruster, a micro-ion thruster, a silicon seismometer, a dewpoint microhygrometer, a micro laser doppler anemometer, and tunable diode laser (TDL) sensors. The advanced technology insertion is critical for NASA to decrease mass, volume, power and mission costs, and increase functionality, science potential and robustness.

A method for coupling a parameterization of the planetary boundary layer with a hydrologic model

NASA Technical Reports Server (NTRS)

Lin, J. D.; Sun, Shu Fen

1986-01-01

Deardorff's parameterization of the planetary boundary layer is adapted to drive a hydrologic model. The method converts the atmospheric conditions measured at the anemometer height at one site to the mean values in the planetary boundary layer; it then uses the planetary boundary layer parameterization and the hydrologic variables to calculate the fluxes of momentum, heat and moisture at the atmosphere-land interface for a different site. A simplified hydrologic model is used for a simulation study of soil moisture and ground temperature on three different land surface covers. The results indicate that this method can be used to drive a spatially distributed hydrologic model by using observed data available at a meteorological station located on or nearby the site.

Characterization of sprays

NASA Technical Reports Server (NTRS)

Chigier, N.; Mao, C.-P.

1984-01-01

It is pointed out that most practical power generation and propulsion systems involve the burning of different types of fuel sprays, taking into account aircraft propulsion, industrial furnaces, boilers, gas turbines, and diesel engines. There has been a lack of data which can serve as a basis for spray model development and validation. A major aim of the present investigation is to fill this gap. Experimental apparatus and techniques for studying the characteristics of fuel sprays are discussed, taking into account two-dimensional still photography, cinematography, holography, a laser diffraction particle sizer, and a laser anemometer. The considered instruments were used in a number of experiments, taking into account three different types of fuel spray. Attention is given to liquid fuel sprays, high pressure pulsed diesel sprays, and coal-water slurry sprays.

Turbulent flow structures and aeolian sediment transport over a barchan sand dune

NASA Astrophysics Data System (ADS)

Wiggs, G. F. S.; Weaver, C. M.

2012-03-01

The turbulent structure of airflow over a barchan sand dune is determined using quadrant analysis of wind velocity data derived from sonic anemometers. Results indicate an increased frequency of ejection and sweep events in the toe region of the dune, characteristic of the turbulent bursting process. In contrast, at the crest there was a significant increase in the occurrence of outward interactions. Combined with high frequency saltation data our analyses show that turbulent structures characterised by a positive streamwise fluctuating velocity (+u‧ sweeps at the toe and outward interactions at the crest) have a dominant influence on sand transport on the dune, together accounting for up to 83% and 95% of transporting events at the toe and crest respectively.

Eddy-Covariance and auxiliary measurements, NGEE-Barrow, 2012-2013

DOE Data Explorer

Torn, Margaret; Billesbach, Dave; Raz-Yaseef, Naama

2014-03-24

The EC tower is operated as part of the Next Generation Ecosystem Experiment-Arctic (NGEE) at Barrow, Alaska. The tower is collecting flux data from the beginning of the thaw season, early June, and until conditions are completely frozen, early November. The tower is equipped with a Gill R3-50 Sonic Anemometer, LI-7700 (CH4) sensor, a LI-7500A (CO2/H2O) sensor, and radiation sensors (Kipp and Zonen CNR-4 (four component radiometer), two LiCor LI-190 quantum sensors (PAR upwelling and downwelling), and a down-looking Apogee SI-111 infrared radiometer (surface temperature)). The sensors are remotely controlled, and communication with the tower allows us to retrieve information in real time.

Spatial correlation of atmospheric wind at scales relevant for large scale wind turbines

NASA Astrophysics Data System (ADS)

Bardal, L. M.; Sætran, L. R.

2016-09-01

Wind measurements a short distance upstream of a wind turbine can provide input for a feedforward wind turbine controller. Since the turbulent wind field will be different at the point/plane of measurement and the rotor plane the degree of correlation between wind speed at two points in space both in the longitudinal and lateral direction should be evaluated. This study uses a 2D array of mast mounted anemometers to evaluate cross-correlation of longitudinal wind speed. The degree of correlation is found to increase with height and decrease with atmospheric stability. The correlation is furthermore considerably larger for longitudinal separation than for lateral separation. The integral length scale of turbulence is also considered.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Herman, R.; O’Brien, S.

Using our own prototype sensor arrays that were deployed to collect microclimate data, we were able to visualize distinct differences in temperature, wind speed, and humidity over very small ranges of distance. We collected data across four polygons within the Barrow Environmental Observatory site. Our prototype microclimate arrays were based on an Arduino microcontroller, DS18B20 temperature sensors, DHT11 relative humidity/temperature sensors, and Vernier anemometers. Data were obtained in a small grid pattern with four sensors spaced 60 cm apart along the x-axis, and moved at 60 cm increments along a y-line across a polygon. Overlaying bird nest location with suchmore » data has allowed us to better answer our research question, “How do Arctic birds choose where to nest to maximize fitness in harsh Arctic environments?”« less

Observation of organized structure in turbulent flow within and above a forest canopy

NASA Technical Reports Server (NTRS)

Gao, W.; Shaw, R. H.; Paw u, K. T.

1989-01-01

Data obtained with seven triaxial sonic anemometer/thermometers and three Lyman-alpha hygrometers at an experimental site in Ontario, Canada reveal the coherent occurrence of ramp patterns of temperature and humidity at several levels within and above the deciduous forest considered. The ramps appear most clearly in the middle and upper portion of the forest, and near the top of the forest they are composed of a weak ejecting motion transporting warm and/or moist air out of the forest, followed by strong sweeps of cool and/or dry air penetrating into the canopy. In the middle and upper parts of the canopy, the sweeps are found to conduct a large proportion of the overall transfer between the forest and the lower atmosphere, with a lesser contribution from ejections.

A quiet tunnel investigation of hypersonic boundary-layer stability over a cooled, flared cone

NASA Technical Reports Server (NTRS)

Blanchard, Alan E.; Selby, Gregory V.; Wilkinson, Stephen P.

1996-01-01

A flared-cone model under adiabatic and cooled-wall conditions was placed in a calibrated, low-disturbance Mach 6 flow and the stability of the boundary layer was investigated using a prototype constant-voltage anemometer. The results were compared with linear-stability theory predictions and good agreement was found in the prediction of second-mode frequencies and growth. In addition, the same 'N = 10' criterion used to predict boundary-layer transition in subsonic, transonic, and supersonic flows under low freestream noise conditions was found to be applicable for the hypersonic flow regime as well. Under cooled-wall conditions, a unique set of spectral data was acquired that documents the linear, nonlinear, and breakdown regions associated with the transition of hypersonic flow under low-noise conditions.

Community wind electrical power case study: Muir Beach. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bluhm, R.; Freebairn-Smith, R.

1979-10-01

Muir Beach experiences relatively steady northwest coastal winds. Recordings at anemometer stations have indicated wind speeds averaging 10 to 12 mph over the year. This compares favorably with the minimum of 8 to 9 mph generally considered necessary for feasible wind-electric generation. Given the town's wind environment, a 100 kW wind turbine of the kind planned could provide an annual output of about 150,000 kWh, or about one-eighth of Muir Beach's projected need. Especially promising for Muir Beach are other potential sites at higher elevations on neighboring Mt. Tamalpais, where federal records indicate annual average speeds of 18 mph. Eachmore » 100 kW wind turbine sited there could conservatively yield at least double and perhaps triple the output of the first system.« less

A radionuclide counting technique for measuring wind velocity. [drag force anemometers

NASA Technical Reports Server (NTRS)

Singh, J. J.; Khandelwal, G. S.; Mall, G. H.

1981-01-01

A technique for measuring wind velocities of meteorological interest is described. It is based on inverse-square-law variation of the counting rates as the radioactive source-to-counter distance is changed by wind drag on the source ball. Results of a feasibility study using a weak bismuth 207 radiation source and three Geiger-Muller radiation counters are reported. The use of the technique is not restricted to Martian or Mars-like environments. A description of the apparatus, typical results, and frequency response characteristics are included. A discussion of a double-pendulum arrangement is presented. Measurements reported herein indicate that the proposed technique may be suitable for measuring wind speeds up to 100 m/sec, which are either steady or whose rates of fluctuation are less than 1 kHz.

Detailed flow measurements in a centrifugal compressor vaneless diffuser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pinarbasi, A.; Johnson, M.W.

1994-07-01

Hot-wire anemometer measurements have been made in the vaneless diffuser of a 1-m-dia low-speed backswept centrifugal compressor using a phase lock loop technique. Radial, tangential, and axial velocity measurements have been made on eight measurement planes through the diffuser. The flow field at the diffuser entry clearly shows the impeller jet-wake flow pattern and the blade wakes. The passage wake is located on the shroud side of the diffuser and mixes out slowly as the flow moves through the diffuser. The blade wakes, on the other hand, distort and mix out rapidly in the diffuser. Contours of turbulent kinetic energymore » are also presented on each of the measurement stations, from which the regions of turbulent mixing can be deduced.« less

Effect of high environmental temperature on semen parameters among fertile men.

PubMed

Momen, M Nabil; Ananian, Fredrick B; Fahmy, Ibrahim M; Mostafa, Taymour

2010-04-01

To evaluate the effect of high environmental occupational temperature on semen parameters of fertile men. Prospective. Steel-casting plant. Ninety fertile workers exposed to a high temperature compared with 40 fertile workers working under ordinary conditions as control subjects. Measurement of scrotal temperature by invagination thermometry, air temperature, relative humidity by aspirated psychrometer, radiant heat by globe thermometer, air velocity by light vane anemometer, and semen analysis. Scrotal temperature and semen analysis. Nonsignificant difference was found between the two groups regarding their scrotal temperature. Also, nonsignificant differences were demonstrated regarding semen analysis parameters being in the normozoospermic range. Under high environmental temperature, semen parameters were within normozoospermic levels owing to body acclimatization mechanisms. Copyright 2010 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.

Laser Doppler technology applied to atmospheric environmental operating problems

NASA Technical Reports Server (NTRS)

Weaver, E. A.; Bilbro, J. W.; Dunkin, J. A.; Jeffreys, H. B.

1976-01-01

Carbon dioxide laser Doppler ground wind data were very favorably compared with data from standard anemometers. As a result of these measurements, two breadboard systems were developed for taking research data: a continuous wave velocimeter and a pulsed Doppler system. The scanning continuous wave laser Doppler velocimeter developed for detecting, tracking and measuring aircraft wake vortices was successfully tested at an airport where it located vortices to an accuracy of 3 meters at a range of 150 meters. The airborne pulsed laser Doppler system was developed to detect and measure clear air turbulence (CAT). This system was tested aboard an aircraft, but jet stream CAT was not encountered. However, low altitude turbulence in cumulus clouds near a mountain range was detected by the system and encountered by the aircraft at the predicted time.

Experimental measurements of unsteady turbulent boundary layers near separation

NASA Technical Reports Server (NTRS)

Simpson, R. L.

1982-01-01

Investigations conducted to document the behavior of turbulent boundary layers on flat surfaces that separate due to adverse pressure gradients are reported. Laser and hot wire anemometers measured turbulence and flow structure of a steady free stream separating turbulent boundary layer produced on the flow of a wind tunnel section. The effects of sinusoidal and unsteadiness of the free stream velocity on this separating turbulent boundary layer at a reduced frequency were determined. A friction gage and a thermal tuft were developed and used to measure the surface skin friction and the near wall fraction of time the flow moves downstream for several cases. Abstracts are provided of several articles which discuss the effects of the periodic free stream unsteadiness on the structure or separating turbulent boundary layers.

The entrainment rate for a row of turbulent jets. M.S. Thesis Final Report

NASA Technical Reports Server (NTRS)

Gordon, Eliott B.; Greber, Isaac

1990-01-01

Entrainment rates for a row of isothermal circular air jets issuing into a quiescent environment are found by integrating velocity distributions measured by a linearized hot-wire anemometer. Jet spacing to jet diameter ratios of 2.5, 5, 10, and 20 are studied at jet Reynold's numbers ranging from 5110 to 12070. Velocity distributions are determined at regular downstream intervals at axial distances equal to 16.4 to 164 jet diameters from the jet source. The entrainment rates for the four spacing configurations vary monotonically with increasing spacing/diameter between the limiting case of the slot jet entrainment rate (where the jet spacing to diameter ratio is zero) and the circular jet entrainment rate (in which the spacing to diameter ratio is infinity).

Experimental validation of alternate integral-formulation method for predicting acoustic radiation based on particle velocity measurements.

PubMed

Ni, Zhi; Wu, Sean F

2010-09-01

This paper presents experimental validation of an alternate integral-formulation method (AIM) for predicting acoustic radiation from an arbitrary structure based on the particle velocities specified on a hypothetical surface enclosing the target source. Both the normal and tangential components of the particle velocity on this hypothetical surface are measured and taken as the input to AIM codes to predict the acoustic pressures in both exterior and interior regions. The results obtained are compared with the benchmark values measured by microphones at the same locations. To gain some insight into practical applications of AIM, laser Doppler anemometer (LDA) and double hotwire sensor (DHS) are used as measurement devices to collect the particle velocities in the air. Measurement limitations of using LDA and DHS are discussed.

Transient hot-film sensor response in a shock tube

NASA Technical Reports Server (NTRS)

Roberts, A. S., Jr.; Ortgies, K. R.; Gartenberg, E.

1989-01-01

Shock tube experiments were performed to determine the response of a hot-film sensor, mounted flush on the side wall of a shock tube, to unsteady flow behind a normal shock wave. The present experiments attempt to isolate the response of the anemometer due only to the change in convective heat transfer at the hot-film surface. The experiments, performed at low supersonic shock speeds in air, are described along with the data acquisition procedure. The change in convective heat transfer is deduced from the data and the results are compared with those from transient boundary layer theory and another set of experimental results. Finally, a transient local heat transfer coefficient is formulated for use as the forcing function in a hot-film sensor instrument model simulation.

Heat transfer from cylinders in subsonic slip flows

NASA Technical Reports Server (NTRS)

Nagabushana, K. A.; Stainback, P. C.

1992-01-01

The heat transfer in heated wires was measured using a constant temperature anemometer over a Mach number range from 0.05 to 0.4 and pressures from 0.5 to 8.0 atmospheres. The total temperature ranged from 80 to 120 F and the wire diameters were 0.00015, 0.00032, and 0.00050 inch. The heat transfer data is presented in the form of a corrected Nusselt number. Based on suggested criteria, much of the data was obtained in the slip flow regime. Therefore, the data is compared with data having comparable flow conditions. The possible application of the heat transfer data to hot wire anemometry is discussed. To this end, the sensitivity of the wires to velocity, density, and total temperature is computed and compared using two different types of correlations.

The pros and cons of code validation

NASA Technical Reports Server (NTRS)

Bobbitt, Percy J.

1988-01-01

Computational and wind tunnel error sources are examined and quantified using specific calculations of experimental data, and a substantial comparison of theoretical and experimental results, or a code validation, is discussed. Wind tunnel error sources considered include wall interference, sting effects, Reynolds number effects, flow quality and transition, and instrumentation such as strain gage balances, electronically scanned pressure systems, hot film gages, hot wire anemometers, and laser velocimeters. Computational error sources include math model equation sets, the solution algorithm, artificial viscosity/dissipation, boundary conditions, the uniqueness of solutions, grid resolution, turbulence modeling, and Reynolds number effects. It is concluded that, although improvements in theory are being made more quickly than in experiments, wind tunnel research has the advantage of the more realistic transition process of a right turbulence model in a free-transition test.

Hot wire in low Reynolds number flow

NASA Technical Reports Server (NTRS)

Kolb, M. A.; Covert, E. E.

1984-01-01

Progress reports were issued on the following experiments: (1) low Reynolds number flow phenomenon of periodic vortex shedding in the wake behind a cylinder as studied by applying the hot wire anemometer technique of flow measurement. The downstream diffusion of these shed vortices was of prime concern. An evaluation of the performance of the hot wire at low Reynolds number is also considered. (2) A brief examination of the back sections of the Wright Brothers wind tunnel circuits were conducted to establish whether or not gross flow deviations were present at corners, or turning vane regions. A calibration of the test sections was done. (3) The attractiveness of using rembedded grids for airfoil calculations modeled by the Euler equations was explored. These calculations were extended to C-type grids and then to Navier-Stokes calculations,

Observed acoustic and aeroelastic spectral responses of a MOD-2 turbine blade to turbulence excitation

NASA Technical Reports Server (NTRS)

Kelley, N. D.; Mckenna, H. E.; Jacobs, E. W.

1995-01-01

Early results from a recent experiment designed to directly evaluate the aeroacoustic/elastic spectral responses of a MOD-2 turbine blade to turbulence-induced unsteady blade loads are discussed. The experimental procedure consisted of flying a hot-film anemometer from a tethered balloon in the turbine inflow and simultaneously measuring the fluctuating airload and aeroelastic response at two blade span stations (65% and 87% spans) using surface-mounted, subminiature pressure transducers and standard strain gage instrumentation. The radiated acoustic pressure field was measured with a triad of very-low-frequency microphones placed at ground level, 1.5 rotor diameters upwind of the disk. Initial transfer function estimates for acoustic radiation, blade normal forces, flapwise acceleration/displacement, and chord/flapwise moments are presented.

In-situ measurement system

DOEpatents

Lord, David E.

1983-01-01

A multipurpose in situ underground measurement system comprising a plurality of long electrical resistance elements in the form of rigid reinforcing bars, each having an open loop "hairpin" configuration of shorter length than the other resistance elements. The resistance elements are arranged in pairs in a unitized structure, and grouted in place in the underground volume. The electrical resistance of each element and the difference in electrical resistance of the paired elements are obtained, which difference values may be used in analytical methods involving resistance as a function of temperature. A scanner sequentially connects the resistance-measuring apparatus to each individual pair of elements. A source of heating current is also selectively connectable for heating the elements to an initial predetermined temperature prior to electrical resistance measurements when used as an anemometer.

An Analysis of Peak Wind Speed Data from Collocated Mechanical and Ultrasonic Anemometers

NASA Technical Reports Server (NTRS)

Short, David A.; Wells, Leonard; Merceret, Francis J.; Roeder, William P.

2007-01-01

This study compared peak wind speeds reported by mechanical and ultrasonic anemometers at Cape Canaveral Air Force Station and Kennedy Space Center (CCAFS/KSC) on the east central coast of Florida and Vandenberg Air Force Base (VAFB) on the central coast of California. Launch Weather Officers, forecasters, and Range Safety analysts need to understand the performance of wind sensors at CCAFS/KSC and VAFB for weather warnings, watches, advisories, special ground processing operations, launch pad exposure forecasts, user Launch Commit Criteria (LCC) forecasts and evaluations, and toxic dispersion support. The legacy CCAFS/KSC and VAFB weather tower wind instruments are being changed from propeller-and-vane (CCAFS/KSC) and cup-and-vane (VAFB) sensors to ultrasonic sensors under the Range Standardization and Automation (RSA) program. Mechanical and ultrasonic wind measuring techniques are known to cause differences in the statistics of peak wind speed as shown in previous studies. The 45th Weather Squadron (45 WS) and the 30th Weather Squadron (30 WS) requested the Applied Meteorology Unit (AMU) to compare data between the RSA ultrasonic and legacy mechanical sensors to determine if there are significant differences. Note that the instruments were sited outdoors under naturally varying conditions and that this comparison was not designed to verify either technology. Approximately 3 weeks of mechanical and ultrasonic wind data from each range from May and June 2005 were used in this study. The CCAFS/KSC data spanned the full diurnal cycle, while the VAFB data were confined to 1000-1600 local time. The sample of 1-minute data from numerous levels on five different towers on each range totaled more than 500,000 minutes of data (482,979 minutes of data after quality control). The ten towers were instrumented at several levels, ranging from 12 ft to 492 ft above ground level. The ultrasonic sensors were collocated at the same vertical levels as the mechanical sensors and typically within 15 ft horizontally of each another. Data from a total of 53 RSA ultrasonic sensors, collocated with mechanical sensors were compared. The 1- minute average wind speed/direction and the 1-second peak wind speed/direction were compared.

UAV multirotor platform for accurate turbulence measurements in the atmosphere

NASA Astrophysics Data System (ADS)

Carbajo Fuertes, Fernando; Wilhelm, Lionel; Sin, Kevin Edgar; Hofer, Matthias; Porté-Agel, Fernando

2017-04-01

One of the most challenging tasks in atmospheric field studies for wind energy is to obtain accurate turbulence measurements at any location inside the region of interest for a wind farm study. This volume would ideally include from several hundred meters to several kilometers around it and from ground height to the top of the boundary layer. An array of meteorological masts equipped with several sonic anemometers to cover all points of interest would be the best in terms of accuracy and data availability, but it is an obviously unfeasible solution. On the other hand, the evolution of wind LiDAR technology allows to measure at any point in space but unfortunately it involves two important limitations: the first one is the relatively low spatial and temporal resolution when compared to a sonic anemometer and the second one is the fact that the measurements are limited to the velocity component parallel to the laser beam (radial velocity). To overcome the aforementioned drawbacks, a UAV multirotor platform has been developed. It is based on a state-of-the-art octocopter with enough payload to carry laboratory-grade instruments for the measurement of time-resolved atmospheric pressure, three-component velocity vector and temperature; and enough autonomy to fly from 10 to 20 minutes, which is a standard averaging time in most atmospheric measurement applications. The UAV uses a gyroscope, an accelerometer, a GPS and an algorithm has been developed and integrated for the correction of any orientation and movement. This UAV platform opens many possibilities for the study of features that have been almost exclusively studied until now in wind tunnel such as wind turbine blade tip vortex characteristics, near-wake to far-wake transition, momentum entrainment from the higher part of the boundary layer in wind farms, etc. The validation of this new measurement technique has been performed against sonic anemometry in terms of wind speed and temperature time series as well as the most important turbulence statistics such as turbulence intensity or momentum and heat turbulent fluxes. Some example measurements of turbulence around a wind turbine will be shown as well in order to showcase the potential of this UAV platform.

Field-based ET calibration and validation sites in interior Alaska: Preparatory Science for NASA's planned HyspIRI Mission

NASA Astrophysics Data System (ADS)

Prakash, A.; Cristobal, J.; Fochesatto, G. J.; Starkenburg, D. P.; Kane, D. L.; Gens, R.; Alfieri, J. G.; Irving, K.; Anderson, M. C.; Kustas, W.

2012-12-01

Evapotranspiration (ET) is a critical component of the hydrologic cycle in interior Alaska, being about 74% of summer precipitation or 50% of annual precipitation, and is a process that will become more important as we witness increasing trends of climate warming, permafrost degradation, forest fire occurrences, and significant land cover changes. In preparation for NASA's planned Hyperspectral Infrared Imager (HyspIRI) satellite mission; we have established two experimental sites in interior Alaska to measure representative ET values for typical boreal forest in this region as a basis to estimate and upscale ET from remote sensing solar and thermal data. The first site (University of Alaska Fairbanks, UAF, north campus) is located in a needleleaf forest mainly composed of black spruce (Picea mariana) and the second site (Caribou-Poker Creek Research Watershed) is in a deciduous forest mainly composed of paper birch (Betula papyrifera). Both field sites are equipped with sonic anemometers and gas analyzers at 24 m height operating at a 20Hz sampling rate, and, additionally, the UAF north campus site includes a 3 and 12m sonic anemometers. At 24m, the tower is also equipped with a four component net radiometer sensor and air temperature and pressure sensors are installed at different heights. To monitor ground heat, temperature and soil moisture sensors as well as heat flux plates have also been installed in the organic and the subsurface soil layers. Additionally, a Large Aperture Scintillometer (LAS) transmitter and receiver units with a separation of 1.2 km have been installed across the tower ensuring a beam height of 24m. Data is recorded on data loggers and downloaded for quality check and processing on a weekly basis. Further details of tower set-up are available at www.et.alaska.edu. Data from the field instruments are presented and their use for Alaska specific ET model calibration are discussed. The field set-up provides all input data for ET modeling and for boundary layer micrometeorological research and the field-sites have also potential to benefit CalVal activities for other planned missions such us SMAP, Sentinel series, and EnMap.

Turbulent Fogwater Flux Measurements Above A Forest

NASA Astrophysics Data System (ADS)

Burkard, R.; Eugster, W.; Buetzberger, P.; Siegwolf, R.

Many forest ecosystems in elevated regions receive a significant fraction of their wa- ter and nutrient input by the interception of fogwater. Recently, several studies have demonstrated the suitability of the eddy covariance technique for the direct measure- ment of turbulent liquid water fluxes. Since summer 2001 a fogwater flux measure- ment equipment has been running at a montane site above a mixed forest canopy in Switzerland. The measurement equipment consists of a high-speed size-resolving droplet spectrometer and a three-dimensional ultrasonic anemometer. The chemical composition of the fogwater was determined from samples collected with a modified Caltech active strand collector. The deposition of nutrients by fog (occult deposition) was calculated by multiplying the total fogwater flux (total of measured turbulent and calculated gravitational flux) during each fog event by the ionic concentrations found in the collected fogwater. Several uncertainties still exist as far as the accuracy of the measurements is con- cerned. Although there is no universal statistical approach for testing the quality of the liquid water flux data directly, results of independent data quality checks of the two time series involved in the flux computation and accordingly the two instruments (ultrasonic anemometer and the droplet spectrometer) are presented. Within the measurement period, over 80 fog events with a duration longer than 2.5 hours were analyzed. An enormous physical and chemical heterogeneity among these fog events was found. We assume that some of this heterogeneity is due to the fact that fog or cloud droplets are not conservative entities: the turbulent flux of fog droplets, which can be referred to as the liquid water flux, is affected by phase change processes and coagulation. The measured coexistence of upward fluxes of small fog droplets (di- ameter < 10 µm) with the downward transport of larger droplets indicates the influ- ence of such processes. With the aid of the measured data we will present an approach which is based on the evolution of the stable isotope ratios during a fog event, on how to deal with the complexity of the evaporation and condensation processes during a fog event.

3D-calibration of three- and four-sensor hot-film probes based on collocated sonic using neural networks

NASA Astrophysics Data System (ADS)

Kit, Eliezer; Liberzon, Dan

2016-09-01

High resolution measurements of turbulence in the atmospheric boundary layer (ABL) are critical to the understanding of physical processes and parameterization of important quantities, such as the turbulent kinetic energy dissipation. Low spatio-temporal resolution of standard atmospheric instruments, sonic anemometers and LIDARs, limits their suitability for fine-scale measurements of ABL. The use of miniature hot-films is an alternative technique, although such probes require frequent calibration, which is logistically untenable in field setups. Accurate and truthful calibration is crucial for the multi-hot-films applications in atmospheric studies, because the ability to conduct calibration in situ ultimately determines the turbulence measurements quality. Kit et al (2010 J. Atmos. Ocean. Technol. 27 23-41) described a novel methodology for calibration of hot-film probes using a collocated sonic anemometer combined with a neural network (NN) approach. An important step in the algorithm is the generation of a calibration set for NN training by an appropriate low-pass filtering of the high resolution voltages, measured by the hot-film-sensors and low resolution velocities acquired by the sonic. In Kit et al (2010 J. Atmos. Ocean. Technol. 27 23-41), Kit and Grits (2011 J. Atmos. Ocean. Technol. 28 104-10) and Vitkin et al (2014 Meas. Sci. Technol. 25 75801), the authors reported on successful use of this approach for in situ calibration, but also on the method’s limitations and restricted range of applicability. In their earlier work, a jet facility and a probe, comprised of two orthogonal x-hot-films, were used for calibration and for full dataset generation. In the current work, a comprehensive laboratory study of 3D-calibration of two multi-hot-film probes (triple- and four-sensor) using a grid flow was conducted. The probes were embedded in a collocated sonic, and their relative pitch and yaw orientation to the mean flow was changed by means of motorized traverses. The study demonstrated that NN-calibration is a powerful tool for calibration of multi-sensor 3D-hot film probes embedded in a collocated sonic, and can be employed in long-lasting field campaigns.

Energy balance measurements over a small reservoir in Ghana's Upper East Region

NASA Astrophysics Data System (ADS)

van de Giesen, Nick; Ohene Annor, Frank

2013-04-01

Near the small village of Binaba (10.778927 deg N, 0.464859 deg E), a small irrigation reservoir has been instrumented to measure different parts of the energy balance of this water body. Instruments were placed on, or attached to, a spar platform. This platform consisted of a long PVC pipe, the spar, which is closed at the bottom. On the PVC pipe rests an aluminum frame platform that carries instrumentation and solar power panel. In turn, the platform rests partially on a large inflated tire. At the bottom of the PVC pipe, lead weights and batteries were placed to ensure a very low point of gravity to minimize wave impact on the platform movement. The tire ensures a large second moment of the water plane. The combination of large second momentum of the water plane and small displacement, ensures a high placement of the metacenter. The distance between the point of gravity and the metacenter is relatively long and the weight is large due to the weights and batteries. This ensures that the eigenfrequency of the platform is very low. On the platform, we fixed a WindMaster Pro (sonic anemometer for 3D wind speed and air temperature to perform eddy covariance measurements of sensible heat flux), a NR Lite (net radiometer), and air temperature and relative humidity sensors. Water temperature at different depths was measured with a string of TidbiT's (waterproof temperature sensors and loggers). The platform had a wind vane and the spar could turn freely around its anchor cable to ensure that the anemometer always faced upwind. A compass in the logger completed this setup. First results suggest, as expected, that the sensible heat flux is relatively small with on average 20 W/m2 over the course of a day. Sensible heat flux peaked around midnight at 35 W/m2, when the warm water warmed up the air from the colder surrounding land. The dynamics of heat storage during the daytime and longwave radiation during the night time, are important to calculate the latent heat flux.

An anomalous CO2 uptake measured over asphalt surface by open-path eddy-covariance system

NASA Astrophysics Data System (ADS)

Bogoev, Ivan; Santos, Eduardo

2017-04-01

Measurements of net ecosystem exchange of CO2 in desert environments made by Wohlfahrt et al. (2008) and Ma (2014) indicate strong CO2 sink. The results of these studies have been challenged by Schlesinger (2016) because the rates of the CO2 uptake are incongruent with the increase of biomass in the vegetation and accumulation of organic and inorganic carbon in the soil. Consequently, the accuracy of the open-path eddy-covariance systems in arid and semi-arid ecosystems has been questioned. A new technology merging the sensing paths of the gas analyzer and the sonic anemometer has recently been developed. This integrated open-path system allows a direct measurement of CO2 mixing ratio in the open air and has the potential to improve the quality of the temperature related density and spectroscopic corrections by synchronously measuring the sensible heat flux in the optical path of the gas analyzer. We evaluate the performance and the accuracy of this new sensor over a large parking lot with an asphalt surface where the water vapor and CO2 fluxes are expected to be low and the interfering sensible heat fluxes are above 200 Wm-2. For independent CO2 flux reference measurements, we use a co-located closed-path analyzer with a short intake tube and a standalone sonic anemometer. We compare energy and carbon dioxide fluxes between the open- and the closed-path systems. During periods with sensible heat flux above 100 W m-2, the open-path system reports an apparent CO2 uptake of 0.02 mg m-2 s-1, while the closed-path system consistently measures a more acceptable upward flux of 0.015 mg m-2 s-1. We attribute this systematic bias to inadequate fast-response temperature compensation of absorption-line broadening effects. We demonstrate that this bias can be eliminated by using the humidity-corrected fast-response sonic temperature to compensate for the abovementioned spectroscopic effects in the open-path analyzer.

Wind shear, sensible heat flux and atmospheric stability within a forest canopy

NASA Astrophysics Data System (ADS)

Piringer, M.; Polreich, E.

2009-09-01

The scientific project "ROSALIA”, carried out in co-operation between ZAMG and the Austrian Federal Research and Training Centre for Forests, Natural Hazards, and Landscape, investigated the meteorological impacts on pollen emission and spread in a typical Central European forest of mixed deciduous and coniferous trees. The study area is the "Lehrforst Rosalia” of BOKU University approx. 60 km south of the city of Vienna in undulating terrain (300 - 750 m altitude). In this area, two meteorological towers of similar construction, one at crest height, the other in the small valley of the river "Ofenbach” near a meteorological ground station, have been equipped with 3D ultrasonic anemometers: one has been placed on top of the upper tower to representatively measure the gradient flow; the tower in the valley has been equipped with 3 instruments, one at the lowermost platform near ground, the second in the middle of the forest canopy, the third on top of the tower situated within the transition zone between the canopy and the "free” boundary layer where the gradient winds dominate. The sonic anemometers measure the three-dimensional wind vector; in addition, the sound velocity is derived, from which the so-called "sonic temperature” is calculated to derive the sensible heat flux. Other quantities are the means, standard deviations, and covariances of the wind components and the momentum flux, the Monin-Obukhov stability parameter, and the friction velocity. In the sloping dense forest canopy surrounding the tower, complex meteorological conditions and frequent decoupling of above-canopy and within-canopy flow has to be expected. The presence of a thick leaf canopy results in a stronger decoupling between the flow above and inside the canopy. As the investigation period covers April and May 2009, this gives the opportunity to discern between leaf-off (at the beginning) and leaf-on periods, with a proposed increase in decoupling with time. The aim of the study is to derive characteristic patterns of wind and atmospheric stability within the forest canopy for leaf-off and leaf-on periods as well as for days of intense versus negligible pollen production.

Proceedings of Workshop on Laser Diagnostics in Fluid Mechanics and Combustion

NASA Astrophysics Data System (ADS)

1993-10-01

Proceedings of the Workshop on Laser Diagnostics in Fluid Mechanics and Combustion are presented. Topics included are: Accuracy of Laser Doppler Anemometry; Applications of Raman-Rayleigh-LIF Diagnostics in Combustion Research; Phase Doppler Anemometer Technique Concepts and Applications; CARS; Particle Image Velocimetry; Practical Consideration in the Use and Design of Laser Velocimetry Systems in Turbomachinery Applications; Phase Doppler Measurements of Gas-Particle Flow Through a Tube Bank; Degenerate Four Wave Mixing for Shock Tunnel Studies of Supersonic Combustion; Laser Induced Photodissociation and Fluorescence (LIPF) of Sodium Species Present in Coal Combustion; 3D Holographic Measurements Inside a Spark Ignition Engine; Laser Doppler Velocimeter Measurements in Compressible Flow; Bursting in a Tornado Vortex; Quantitative Imaging of OH and Temperature Using a Single Laser Source and Single Intensified Camera; and Laser Doppler Measurements Inside an Artificial Heart Valve.

Capabilities and constraints of combustion diagnostics in microgravity

NASA Technical Reports Server (NTRS)

Greenberg, Paul S.

1993-01-01

A significant scientific return from both existing and proposed microgravity combustion science experiments is substantially dependent on the availability of diagnostic systems for the collection of the required scientific data. To date, the available diagnostic instrumentation has consisted primarily of conventional photographic media and intrusive temperature and velocity probes, such as thermocouples and hot wire anemometers. This situation has arisen primarily due to the unique and severe operational constraints inherent in reduced gravity experimentation. Each of the various reduced gravity facilities is accompanied by its own peculiar envelope of capabilities and constraints. Drop towers, for example, pose strict limitations on available working volume and power, as well as autonomy of operation. In contrast, hardware developed for space flight applications can be somewhat less constrained in regards to the aforementioned quantities, but is additionally concerned with numerous issues involving safety and reliability.

In situ measurement system

DOEpatents

Lord, D.E.

1980-11-24

A multipurpose in situ underground measurement system comprising a plurality of long electrical resistance elements in the form of rigid reinforcing bars, each having an open loop hairpin configuration of shorter length than the other resistance elements. The resistance elements are arranged in pairs in a unitized structure, and grouted in place in the underground volume. Measurement means are provided for obtaining for each pair the electrical resistance of each element and the difference in electrical resistance of the paired elements, which difference values may be used in analytical methods involving resistance as a function of temperature. A scanner means sequentially connects the resistance-measuring apparatus to each individual pair of elements. A source of heating current is also selectively connectable for heating the elements to an initial predetermined temperature prior to electrical resistance measurements when used as an anemometer.

Comparison of laser anemometer measurements and theory in an annular turbine cascade with experimental accuracy determined by parameter estimation

NASA Technical Reports Server (NTRS)

Goldman, L. J.; Seasholtz, R. G.

1982-01-01

Experimental measurements of the velocity components in the blade to blade (axial tangential) plane were obtained with an axial flow turbine stator passage and were compared with calculations from three turbomachinery computer programs. The theoretical results were calculated from a quasi three dimensional inviscid code, a three dimensional inviscid code, and a three dimensional viscous code. Parameter estimation techniques and a particle dynamics calculation were used to assess the accuracy of the laser measurements, which allow a rational basis for comparison of the experimenal and theoretical results. The general agreement of the experimental data with the results from the two inviscid computer codes indicates the usefulness of these calculation procedures for turbomachinery blading. The comparison with the viscous code, while generally reasonable, was not as good as for the inviscid codes.

Concepts for a theoretical and experimental study of lifting rotor random loads and vibrations (further experiments with progressing/regressing rotor flapping modes), Phase 7-C

NASA Technical Reports Server (NTRS)

Hohenemser, K. H.; Crews, S. T.

1973-01-01

The experiments with progressing/regressing forced rotor flapping modes have been extended in several directions and the data processing method has been considerably refined. The 16 inch hingeless 2-bladed rotor model was equipped with a new set of high precision blades which removed previously encountered tracking difficulties at high advance ratio, so that tests up to .8 rotor advance ratio could be conducted. In addition to data with 1.20 blade natural flapping frequency data at 1.10 flapping frequency were obtained. Outside the wind tunnel, tests with a ground plate located at different distances below the rotor were conducted while recording the dynamic downflow at a station .2R below the rotor plane with a hot wire anemometer.

Turbulence measurements in a complex plowfield using a crossed hot-wire. M.S. Thesis

NASA Technical Reports Server (NTRS)

Mckillop, B. E.

1983-01-01

Turbulence was quantified in complex axisymmetric, nonreacting, nonswirling flowfields using a crossed hot-wire anemometer. Mean velocity, turbulence intensities, turbulent viscosity, and Reynolds tree were measured in round free jet and confined jet flowfields. The confined jet, a model of an axisymmetric can combustor, had an expansion ratio D/d=2, an expansion angle of 90 deg, and an axial location increments of 0.5 diameters. The confined jet was studied with and without a contraction nozzle. Free jet measurements validated the experimental technique and data reduction. Results show good agreement with those of previous research. Measurements in the confined jet indicate that the cross hot-wire used cannot handle axial flow reversal and the experimental technique is inadequate for measuring time-mean radial velocity. Other quantities show a high level of comparability.

Microelectrokinetic turbulence in microfluidics at low Reynolds number.

PubMed

Wang, Guiren; Yang, Fang; Zhao, Wei

2016-01-01

There is commonly no turbulence in microfluidics, and the flows are believed to be either laminar or chaotic, since Reynolds number (Re) in microflows is usually on the order of unity or lower. However, we recently demonstrated that it is possible to achieve turbulence with low Re (based on the measured flow velocity and the width of the channel entrance) when a pressure-driven flow is electrokinetically forced in a quasi T-microchannel. To be able to measure high frequency velocity fluctuations in microchannels, a velocimeter with submicrometer spatial resolution and microsecond temporal resolution, called a laser-induced fluorescence photobleaching anemometer, is developed. Here we characterize the microelectrokinetic turbulence and observe some typical and important features of high Re flows, such as Kolmogorov -5/3 spectrum of velocity fluctuation, which usually can be realized only at very high Re in macroturbulent flows.

The microburst - Hazard to aircraft

NASA Technical Reports Server (NTRS)

Mccarthy, J.; Serafin, R.

1984-01-01

In encounters with microbursts, low altitude aircraft first encounter a strong headwind which increases their wing lift and altitude; this phenomenon is followed in short succession by a decreasing headwind component, a downdraft, and finally a strong tailwind that catastrophically reduces wing lift and precipitates a crash dive. It is noted that the potentially lethal low altitude wind shear of a microburst may lie in apparently harmless, rain-free air beneath a cloud base. Occasionally, such tell-tale signs as localized blowing of ground dust may be sighted in time. Microbursts may, however, occur in the heavy rain of a thunderstorm, where they will be totally obscured from view. Wind shear may be detected by an array of six anemometers and vanes situated in the vicinity of an airport, and by Doppler radar equipment at the airport or aboard aircraft.

Terrestrial Applications of a Nano-g Accelerometer

NASA Technical Reports Server (NTRS)

Hartley, Frank T.

1996-01-01

The ultra-sensitive accelerometer, developed for NASA to monitor the microgravity environments of Space Shuttle, five orbiters and Space Station, needed to measure accelerations up to 10 mg with an absolute accuracy of 10 nano-g (10(exp -8)g) for at least two orbits (10(exp 4) seconds) to resolve accelerations associated with orbital drag. Also, the accelerometers needed to have less than 10(exp -9) F.S. off-axis sensitivity; to be thermally and magnetically inert; to be immune to quiescent shock, and to have an in-situ calibration capability. Multi-axis compact seismometers, designs that have twelve decades of dynamic range will be described. Density profilometers, precision gradiometers, gyros and vibration isolation designs and applications will be discussed. Finally, examples of transformations of the accelerometer into sensitive anemometers and imaging spectrometers will be presented.

Sonic Thermometer for High-Altitude Balloons

NASA Technical Reports Server (NTRS)

Bognar, John

2012-01-01

The sonic thermometer is a specialized application of well-known sonic anemometer technology. Adaptations have been made to the circuit, including the addition of supporting sensors, which enable its use in the high-altitude environment and in non-air gas mixtures. There is a need to measure gas temperatures inside and outside of superpressure balloons that are flown at high altitudes. These measurements will allow the performance of the balloon to be modeled more accurately, leading to better flight performance. Small thermistors (solid-state temperature sensors) have been used for this general purpose, and for temperature measurements on radiosondes. A disadvantage to thermistors and other physical (as distinct from sonic) temperature sensors is that they are subject to solar heating errors when they are exposed to the Sun, and this leads to issues with their use in a very high-altitude environment

Turbulent shear stresses in compressible boundary layers

NASA Technical Reports Server (NTRS)

Laderman, A. J.; Demetriades, A.

1979-01-01

Hot-wire anemometer measurements of turbulent shear stresses in a Mach 3 compressible boundary layer were performed in order to investigate the effects of heat transfer on turbulence. Measurements were obtained by an x-probe in a flat plate, zero pressure gradient, two dimensional boundary layer in a wind tunnel with wall to freestream temperature ratios of 0.94 and 0.71. The measured shear stress distributions are found to be in good agreement with previous results, supporting the contention that the shear stress distribution is essentially independent of Mach number and heat transfer for Mach numbers from incompressible to hypersonic and wall to freestream temperature ratios of 0.4 to 1.0. It is also found that corrections for frequency response limitations of the electronic equipment are necessary to determine the correct shear stress distribution, particularly at the walls.

Eddy covariance measurements of sea spray particles over the Atlantic Ocean

NASA Astrophysics Data System (ADS)

Norris, S.; Brooks, I.; de Leeuw, G.; Smith, M. H.; Moeman, M.; Lingard, J.

2007-09-01

Most estimates of sea spray aerosol source functions have used indirect means to infer the rate of production as a function of wind speed. Only recently has the technology become available to make high frequency measurements of aerosol concentration suitable for direct eddy correlation determination of the particle flux. This was accomplished in this study by combining a newly developed fast aerosol particle counter with an ultrasonic anemometer which allowed for eddy covariance measurements of size-segregated particle fluxes. The aerosol instrument is the Compact Lightweight Aerosol Spectrometer Probe (CLASP) - capable of measuring 8-channel size spectra for mean radii between 0.15 and 0.35 μm at 10 Hz. The first successful measurements were made during the WASFAB (Waves, Air Sea Fluxes, Aerosol and Bubbles) field campaign in October 2005 in Duck (NC, USA). The method and results are presented and comparisons are made with recent sea spray source functions from the literature.

A multiple-fan active control wind tunnel for outdoor wind speed and direction simulation

NASA Astrophysics Data System (ADS)

Wang, Jia-Ying; Meng, Qing-Hao; Luo, Bing; Zeng, Ming

2018-03-01

This article presents a new type of active controlled multiple-fan wind tunnel. The wind tunnel consists of swivel plates and arrays of direct current fans, and the rotation speed of each fan and the shaft angle of each swivel plate can be controlled independently for simulating different kinds of outdoor wind fields. To measure the similarity between the simulated wind field and the outdoor wind field, wind speed and direction time series of two kinds of wind fields are recorded by nine two-dimensional ultrasonic anemometers, and then statistical properties of the wind signals in different time scales are analyzed based on the empirical mode decomposition. In addition, the complexity of wind speed and direction time series is also investigated using multiscale entropy and multivariate multiscale entropy. Results suggest that the simulated wind field in the multiple-fan wind tunnel has a high degree of similarity with the outdoor wind field.

An experimental investigation of an axisymmetric jet in a coflowing airstream. [using laser Doppler velocimeter

NASA Technical Reports Server (NTRS)

Catalano, G. D.; Morton, J. B.; Humphris, R. R.

1976-01-01

The flow development of an axisymmetric jet exhausting into a moving airstream has been studied. The jet has a Reynolds number of 22,600, and the ratio of the jet velocity to the wind tunnel velocity is 5.1 to 1. The flow field of the axisymmetric jet was examined at locations varying from approximately zero to eight diameters downstream of the orifice. Of primary concern at each downstream location was the mapping of the one point statistical properties of the flow, including mean velocity, turbulent intensity, and intermittency. Autocorrelations and power spectral density curves were determined for both the fluctuating velocity field and the concentration signal at various distances from the jet's center line for different downstream locations. A laser Doppler velocimeter, using a phase locked loop processor, was used to make the desired velocity field measurements which were compared with hot wire anemometer and pressure probe data.

Evaluation of thermal overload in boiler operators.

PubMed

Braga, Camila Soares; Rodrigues, Valéria Antônia Justino; Campos, Julio César Costa; de Souza, Amaury Paulo; Minette, Luciano José; de Moraes, Angêlo Casali; Sensato, Guilherme Luciano

2012-01-01

The Brazilians educational institutions need a large energy demand for the operation of laundries, restaurants and accommodation of students. Much of that energy comes from steam generated in boilers with wood fuel. The laboral activity in boiler may present problems for the operator's health due to exposure to excessive heat, and its operation has a high degree of risk. This paper describes an analysis made the conditions of thermal environment in the operation of a B category boiler, located at a Higher Education Institution, located in the Zona da Mata Mineira The equipments used to collect data were Meter WBGT of the Heat Index; Meter of Wet Bulb Index and Globe Thermometer (WBGT); Politeste Instruments, an anemometer and an Infrared Thermometer. By the application of questionnaires, the second phase consisted of collecting data on environmental factors (temperature natural environment, globe temperature, relative humidity and air velocity). The study concluded that during the period evaluated, the activity had thermal overload.

Lidar determination of winds by aerosol inhomogeneities: motion velocity in the planetary boundary layer.

PubMed

Kolev, I; Parvanov, O; Kaprielov, B

1988-06-15

The paper presents results from lidar measurements of wind velocity in the planetary boundary layer using correlation data processing. Two lidars are used in our experiments: a ruby lidar operating along slant paths and a YAG:Nd lidar operating for near vertical sounding used by us for the first time. On the basis of our experience the optimal sizes of aerosol inhomogeneities (30-300 m), the duration of the experiments (2-10 min), and the repetition rate of laser shots (fractions of hertz to several hertz) are determined. The results are compared to independent data obtained from anemometer measurements, theodolite- and radar-tracked pilot balloons. The range of differences is ~1-2 m/s in speed and 10-15 degrees in direction. Preliminary results from the use of lidar data to remotely sound the wind speed for various atmospheric stratifications and synoptic situations are described as well.

The behavior of the skin-friction coefficient of a turbulent boundary layer flow over a flat plate with differently configured transverse square grooves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wahidi, R.; Chakroun, W.; Al-Fahed, S.

2005-11-01

Skin-friction coefficient of turbulent boundary layer flow over a smooth-wall with transverse square grooves was investigated. Four grooved-wall cases were investigated. The four grooved-wall configurations are single 5mm square grooved-wall, and 5mm square grooves spaced 10, 20 and 40 element widths apart in the streamwise direction. Laser-Doppler Anemometer (LDA) was used for the mean velocity and turbulence intensity measurements. The skin-friction coefficient determined from the velocity profile increases sharply just downstream of the groove. This overshoot is followed by an undershoot and then relaxation back to the smooth-wall value. This behavior is observed in most grooved-wall cases. Integrating the skin-frictionmore » coefficient in the streamwise direction indicates that there is an increase in the overall drag in all the grooved-wall cases.« less

An investigation of turbulent transport in the extreme lower atmosphere

NASA Technical Reports Server (NTRS)

Koper, C. A., Jr.; Sadeh, W. Z.

1975-01-01

A model in which the Lagrangian autocorrelation is expressed by a domain integral over a set of usual Eulerian autocorrelations acquired concurrently at all points within a turbulence box is proposed along with a method for ascertaining the statistical stationarity of turbulent velocity by creating an equivalent ensemble to investigate the flow in the extreme lower atmosphere. Simultaneous measurements of turbulent velocity on a turbulence line along the wake axis were carried out utilizing a longitudinal array of five hot-wire anemometers remotely operated. The stationarity test revealed that the turbulent velocity is approximated as a realization of a weakly self-stationary random process. Based on the Lagrangian autocorrelation it is found that: (1) large diffusion time predominated; (2) ratios of Lagrangian to Eulerian time and spatial scales were smaller than unity; and, (3) short and long diffusion time scales and diffusion spatial scales were constrained within their Eulerian counterparts.

A real time dynamic data acquisition and processing system for velocity, density, and total temperature fluctuation measurements

NASA Technical Reports Server (NTRS)

Clukey, Steven J.

1991-01-01

The real time Dynamic Data Acquisition and Processing System (DDAPS) is described which provides the capability for the simultaneous measurement of velocity, density, and total temperature fluctuations. The system of hardware and software is described in context of the wind tunnel environment. The DDAPS replaces both a recording mechanism and a separate data processing system. DDAPS receives input from hot wire anemometers. Amplifiers and filters condition the signals with computer controlled modules. The analog signals are simultaneously digitized and digitally recorded on disk. Automatic acquisition collects necessary calibration and environment data. Hot wire sensitivities are generated and applied to the hot wire data to compute fluctuations. The presentation of the raw and processed data is accomplished on demand. The interface to DDAPS is described along with the internal mechanisms of DDAPS. A summary of operations relevant to the use of the DDAPS is also provided.

NASA aircraft trailing vortex research

NASA Technical Reports Server (NTRS)

Mcgowan, W. A.

1971-01-01

A brief description is given of NASA's comprehensive program to study the aircraft trailing vortex problem. Wind tunnel experiments are used to develop the detailed processes of wing tip vortex formation and explore different means to either prevent trailing vortices from forming or induce early break-up. Flight tests provide information on trailing vortex system behavior behind large transport aircraft, both near the ground, as in the vicinity of the airport, and at cruise/holding pattern altitudes. Results from some flight tests are used to show how pilots might avoid the dangerous areas when flying in the vicinity of large transport aircraft. Other flight tests will be made to verify and evaluate trailing vortex elimination schemes developed in the model tests. Laser Doppler velocimeters being developed for use in the research program and to locate and measure vortex winds in the airport area are discussed. Field tests have shown that the laser Doppler velocimeter measurements compare well with those from cup anemometers.

Correcting for particle counting bias error in turbulent flow

NASA Technical Reports Server (NTRS)

Edwards, R. V.; Baratuci, W.

1985-01-01

An ideal seeding device is proposed generating particles that exactly follow the flow out are still a major source of error, i.e., with a particle counting bias wherein the probability of measuring velocity is a function of velocity. The error in the measured mean can be as much as 25%. Many schemes have been put forward to correct for this error, but there is not universal agreement as to the acceptability of any one method. In particular it is sometimes difficult to know if the assumptions required in the analysis are fulfilled by any particular flow measurement system. To check various correction mechanisms in an ideal way and to gain some insight into how to correct with the fewest initial assumptions, a computer simulation is constructed to simulate laser anemometer measurements in a turbulent flow. That simulator and the results of its use are discussed.

Propagation of a Free Flame in a Turbulent Gas Stream

NASA Technical Reports Server (NTRS)

Mickelsen, William R; Ernstein, Norman E

1956-01-01

Effective flame speeds of free turbulent flames were measured by photographic, ionization-gap, and photomultiplier-tube methods, and were found to have a statistical distribution attributed to the nature of the turbulent field. The effective turbulent flame speeds for the free flame were less than those previously measured for flames stabilized on nozzle burners, Bunsen burners, and bluff bodies. The statistical spread of the effective turbulent flame speeds was markedly wider in the lean and rich fuel-air-ratio regions, which might be attributed to the greater sensitivity of laminar flame speed to flame temperature in those regions. Values calculated from the turbulent free-flame-speed analysis proposed by Tucker apparently form upper limits for the statistical spread of free-flame-speed data. Hot-wire anemometer measurements of the longitudinal velocity fluctuation intensity and longitudinal correlation coefficient were made and were employed in the comparison of data and in the theoretical calculation of turbulent flame speed.

Visualization and imaging methods for flames in microgravity

NASA Technical Reports Server (NTRS)

Weiland, Karen J.

1993-01-01

The visualization and imaging of flames has long been acknowledged as the starting point for learning about and understanding combustion phenomena. It provides an essential overall picture of the time and length scales of processes and guides the application of other diagnostics. It is perhaps even more important in microgravity combustion studies, where it is often the only non-intrusive diagnostic measurement easily implemented. Imaging also aids in the interpretation of single-point measurements, such as temperature, provided by thermocouples, and velocity, by hot-wire anemometers. This paper outlines the efforts of the Microgravity Combustion Diagnostics staff at NASA Lewis Research Center in the area of visualization and imaging of flames, concentrating on methods applicable for reduced-gravity experimentation. Several techniques are under development: intensified array camera imaging, and two-dimensional temperature and species concentrations measurements. A brief summary of results in these areas is presented and future plans mentioned.

Laser transit anemometer software development program

NASA Technical Reports Server (NTRS)

Abbiss, John B.

1989-01-01

Algorithms were developed for the extraction of two components of mean velocity, standard deviation, and the associated correlation coefficient from laser transit anemometry (LTA) data ensembles. The solution method is based on an assumed two-dimensional Gaussian probability density function (PDF) model of the flow field under investigation. The procedure consists of transforming the data ensembles from the data acquisition domain (consisting of time and angle information) to the velocity space domain (consisting of velocity component information). The mean velocity results are obtained from the data ensemble centroid. Through a least squares fitting of the transformed data to an ellipse representing the intersection of a plane with the PDF, the standard deviations and correlation coefficient are obtained. A data set simulation method is presented to test the data reduction process. Results of using the simulation system with a limited test matrix of input values is also given.

Santa Ana Winds of Southern California: Their climatology, extremes, and behavior spanning six and a half decades

NASA Astrophysics Data System (ADS)

Guzman-Morales, Janin; Gershunov, Alexander; Theiss, Jurgen; Li, Haiqin; Cayan, Daniel

2016-03-01

Santa Ana Winds (SAWs) are an integral feature of the regional climate of Southern California/Northern Baja California region, but their climate-scale behavior is poorly understood. In the present work, we identify SAWs in mesoscale dynamical downscaling of a global reanalysis from 1948 to 2012. Model winds are validated with anemometer observations. SAWs exhibit an organized pattern with strongest easterly winds on westward facing downwind slopes and muted magnitudes at sea and over desert lowlands. We construct hourly local and regional SAW indices and analyze elements of their behavior on daily, annual, and multidecadal timescales. SAWs occurrences peak in winter, but some of the strongest winds have occurred in fall. Finally, we observe that SAW intensity is influenced by prominent large-scale low-frequency modes of climate variability rooted in the tropical and north Pacific ocean-atmosphere system.

Relationship between wind, waves and radar backscatter

NASA Technical Reports Server (NTRS)

Katsaros, Kristina B.; Ataktuerk, Serhad S.

1991-01-01

The aim of the research was to investigate the relationship between wind, waves, and radar backscatter from water surface. To this end, three field experiments with periods of 2 to 4 weeks were carried out during summer months in 1988, 1989 and 1990. For these periods, the University of Washington group provided (1) environmental parameters such as wind speed, wind stress, and atmospheric stratification through measurements of surface fluxes (of momentum, sensible heat and latent heat) and of air and water temperatures; and (2) wave height spectra including both the dominant waves and the short gravity-capillary waves. Surface flux measurements were performed by using our well tested instruments: a K-Gill twin propeller-vane anemometer and a fast response thermocouple psychrometer. Wave heights were measured by a resistance wire wave gauge. The University of Kansas group was responsible for the operation of the microwave radars.

An experimental study of stratospheric gravity waves - Design and preliminary results

NASA Astrophysics Data System (ADS)

Talagrand, O.; Ovarlez, H.

1984-02-01

The design of balloon-borne experimental apparatus for long-term gravitational-wave measurements in the stratosphere is reported, and preliminary results of a first test flight are presented. Two gondolas (each containing a pressure sensor; a temperature sensor; horizontal and vertical sonic anemometers; a fin equipped with crossed magnetometers; and data-processing, data-transmission, and control electronics) are suspended 100 and 300 m below a solar/terrestrial-IR-absorption-heated hot-air balloon drifting between altitudes 22 km (night) and 28 km (day); power is supplied by NiCd batteries recharged by solar cells. The path of the first flight, a circumnavigation beginning in Pretoria, South Africa and crossing South America and northern Australia, from December 11, 1982, to February 2, 1983 (when transmission ceased over southern Africa) is shown on a map, and sample data for a 36-h period are summarized in a graph.

REMS Wind Sensor Preliminary Results

NASA Astrophysics Data System (ADS)

De La Torre Juarez, M.; Gomez-Elvira, J.; Navarro, S.; Marin, M.; Torres, J.; Rafkin, S. C.; Newman, C. E.; Pla-García, J.

2015-12-01

The REMS instrument is part of the Mars Science Laboratory payload. It is a sensor suite distributed over several parts of the rover. The wind sensor, which is composed of two booms equipped with a set of hot plate anemometers, is installed on the Rover Sensing Mast (RSM). During landing most of the hot plates of one boom were damaged, most likely by the pebbles lifted by the Sky Crane thruster. The loss of one wind boom necessitated a full review of the data processing strategy. Different algorithms have been tested on the readings of the first Mars year, and these results are now archived in the Planetary Data System (PDS), The presentation will include a description of the data processing methods and of the resulting products, including the typical evolution of wind speed and direction session-by-session, hour-by-hour and other kinds of statistics . A review of the wind readings over the first Mars year will also be presented.

A comparison of predicted and measured inlet distortion flows in a subsonic axial inlet flow compressor rotor

NASA Technical Reports Server (NTRS)

Owen, Albert K.

1992-01-01

Detailed flow measurements were taken inside an isolated axial compressor rotor operating subsonically near peak efficiency. These Laser Anemometer measurements were made with two inlet velocity profiles. One profile consisted of an unmodified baseline flow, and the second profile was distorted by placing axisymmetric screens on the hub and shroud well upstream of the rotor. A detailed comparison in the rotor relative reference frame between a Navier-Stokes solver and the measured experimental results showed good agreement between the predicted and measured flows. A primary flow is defined in the rotor and deviations and the computed predictions is made to assess the development of a passage vortex due to the distortion of the inlet flow. Computer predictions indicate that a distorted inlet profile has a minimal effect on the development of the flow in the rotor passage and the resulting passage vortex.

Validating precision estimates in horizontal wind measurements from a Doppler lidar

DOE PAGES

Newsom, Rob K.; Brewer, W. Alan; Wilczak, James M.; ...

2017-03-30

Results from a recent field campaign are used to assess the accuracy of wind speed and direction precision estimates produced by a Doppler lidar wind retrieval algorithm. The algorithm, which is based on the traditional velocity-azimuth-display (VAD) technique, estimates the wind speed and direction measurement precision using standard error propagation techniques, assuming the input data (i.e., radial velocities) to be contaminated by random, zero-mean, errors. For this study, the lidar was configured to execute an 8-beam plan-position-indicator (PPI) scan once every 12 min during the 6-week deployment period. Several wind retrieval trials were conducted using different schemes for estimating themore » precision in the radial velocity measurements. Here, the resulting wind speed and direction precision estimates were compared to differences in wind speed and direction between the VAD algorithm and sonic anemometer measurements taken on a nearby 300 m tower.« less

Reynolds number invariance of the structure inclination angle in wall turbulence.

PubMed

Marusic, Ivan; Heuer, Weston D C

2007-09-14

Cross correlations of the fluctuating wall-shear stress and the streamwise velocity in the logarithmic region of turbulent boundary layers are reported over 3 orders of magnitude change in Reynolds number. These results are obtained using hot-film and hot-wire anemometry in a wind tunnel facility, and sonic anemometers and a purpose-built wall-shear stress sensor in the near-neutral atmospheric surface layer on the salt flats of Utah's western desert. The direct measurement of fluctuating wall-shear stress in the atmospheric surface layer has not been available before. Structure inclination angles are inferred from the cross correlation results and are found to be invariant over the large range of Reynolds number. The findings justify the prior use of low Reynolds number experiments for obtaining structure angles for near-wall models in the large-eddy simulation of atmospheric surface layer flows.

Applying a simple three-dimensional eddy correlation system for latent and sensible heat flux to contrasting forest canopies

NASA Astrophysics Data System (ADS)

Bernhofer, Ch.

1992-06-01

A simple eddy correlation system is presented that allows on-line calculation of latent and sensible heat fluxes. The system is composed of a three dimensional propeller anemometer, a thermocouple and a capacitance relative humidity sensor. Results from two contrasting sites demonstrate the capability of the system to measure turbulent fluxes under varying conditions. A dry mixed (dominantly coniferous) forest in hilly terrain in Austria is compared to a well irrigated, heavily transpiring, deciduous pecan orchard in the Southwest of the US. The US site shows insufficient closure of the energy balance that is attributed to non-turbulent fluxes under advective conditions in a stable boundary layer (Blanford et al., 1991) while the Austrian site exhibits almost perfect closure with the use of the very same instruments when the boundary layer is convective and advection is negligible.

Flow measurement in mechanical ventilation: a review.

PubMed

Schena, Emiliano; Massaroni, Carlo; Saccomandi, Paola; Cecchini, Stefano

2015-03-01

Accurate monitoring of flow rate and volume exchanges is essential to minimize ventilator-induced lung injury. Mechanical ventilators employ flowmeters to estimate the amount of gases delivered to patients and use the flow signal as a feedback to adjust the desired amount of gas to be delivered. Since flowmeters play a crucial role in this field, they are required to fulfill strict criteria in terms of dynamic and static characteristics. Therefore, mechanical ventilators are equipped with only the following kinds of flowmeters: linear pneumotachographs, fixed and variable orifice meters, hot wire anemometers, and ultrasonic flowmeters. This paper provides an overview of these sensors. Their working principles are described together with their relevant advantages and disadvantages. Furthermore, the most promising emerging approaches for flowmeters design (i.e., fiber optic technology and three dimensional micro-fabrication) are briefly reviewed showing their potential for this application. Copyright © 2015 IPEM. Published by Elsevier Ltd. All rights reserved.

Wind Noise Reduction in a Non-Porous Subsurface Windscreen

NASA Technical Reports Server (NTRS)

Zuckerwar, Allan J.; Shams, Qamar A.; Knight, H. Keith

2012-01-01

Measurements of wind noise reduction were conducted on a box-shaped, subsurface windscreen made of closed cell polyurethane foam. The windscreen was installed in the ground with the lid flush with the ground surface. The wind was generated by means of a fan, situated on the ground, and the wind speed was measured at the center of the windscreen lid with an ultrasonic anemometer. The wind speed was controlled by moving the fan to selected distances from the windscreen. The wind noise was measured on a PCB Piezotronics 3†electret microphone. Wind noise spectra were measured with the microphone exposed directly to the wind (atop the windscreen lid) and with the microphone installed inside the windscreen. The difference between the two spectra comprises the wind noise reduction. At wind speeds of 3, 5, and 7 m/s, the wind noise reduction is typically 15 dB over the frequency range of 0.1-20 Hz.

Characteristics of inhomogeneous jets in confined swirling air flows

NASA Technical Reports Server (NTRS)

So, R. M. C.; Ahmed, S. A.

1984-01-01

An experimental program to study the characteristics of inhomogeneous jets in confined swirling flows to obtain detailed and accurate data for the evaluation and improvement of turbulent transport modeling for combustor flows is discussed. The work was also motivated by the need to investigate and quantify the influence of confinement and swirl on the characteristics of inhomogeneous jets. The flow facility was constructed in a simple way which allows easy interchange of different swirlers and the freedom to vary the jet Reynolds number. The velocity measurements were taken with a one color, one component DISA Model 55L laser-Doppler anemometer employing the forward scatter mode. Standard statistical methods are used to evaluate the various moments of the signals to give the flow characteristics. The present work was directed at the understanding of the velocity field. Therefore, only velocity and turbulence data of the axial and circumferential components are reported for inhomogeneous jets in confined swirling air flows.

Development of superconducting YBa2Cu3O(x) wires with low resistance electrical contacts

NASA Technical Reports Server (NTRS)

Buoncristiani, A. M.; Byvik, C. E.; Caton, R.; Selim, R.; Lee, B. I.; Modi, V.; Sherrill, M.; Leigh, H. D.; Fain, C. C.; Lewis, G.

1993-01-01

Materials exhibiting superconductivity above liquid nitrogen temperatures (77 K) will enable new applications of this phenomena. One of the first commercial applications of this technology will be superconducting magnets for medical imaging. However, a large number of aerospace applications of the high temperature superconducting materials have also been identified. These include magnetic suspension and balance of models in wind tunnels and resistanceless leads to anemometers. The development of superconducting wires fabricated from the ceramic materials is critical for these applications. The progress in application of a patented fiber process developed by Clemson University for the fabrication of superconducting wires is reviewed. The effect of particle size and heat treatment on the quality of materials is discussed. Recent advances made at Christopher Newport College in the development of micro-ohm resistance electrical contacts which are capable of carrying the highest reported direct current to this material is presented.

ICIASF '85 - International Congress on Instrumentation in Aerospace Simulation Facilities, 11th, Stanford University, CA, August 26-28, 1985, Record

NASA Technical Reports Server (NTRS)

1985-01-01

Developments related to laser Doppler velocimetry are discussed, taking into account a three-component dual beam laser-Doppler-anemometer to be operated in large wind tunnels, a new optical system for three-dimensional laser-Doppler-anemometry using an argon-ion and a dye laser, and a two-component laser Doppler velocimeter by switching fringe orientation. Other topics studied are concerned with facilities, instrumentation, control, hot wire/thin film measurements, optical diagnostic techniques, signal and data processing, facilities and adaptive wall test sections, data acquisition and processing, ballistic instrument systems, dynamic testing and material deformation measurements, optical flow measurements, test techniques, force measurement systems, and holography. Attention is given to nonlinear calibration of integral wind tunnel balances, a microcomputer system for real time digitized image compression, and two phase flow diagnostics in propulsion systems.

A Simple Experiment to Explore Standing Waves in a Flexible Corrugated Sound Tube

NASA Astrophysics Data System (ADS)

Amorim, Maria Eva; Sousa, Teresa Delmira; Carvalho, P. Simeão; Sousa, Adriano Sampaioe

2011-09-01

Sound tubes, pipes, and singing rods are used as musical instruments and as toys to perform amusing experiments. In particular, corrugated tubes present unique characteristics with respect to the sounds they can produce; that is why they have been studied so intensively, both at theoretical and experimental levels.1-4 Experimental studies usually involve expensive and sophisticated equipment that is out of reach of school laboratory facilities.3-6 In this paper we show how to investigate quantitatively the sounds produced by a flexible sound tube corrugated on the inside by using educational equipment readily available in school laboratories, such as the oscilloscope, the microphone, the anemometer, and the air pump. We show that it is possible for students to study the discontinuous spectrum of sounds produced by a flexible corrugated tube and go even further, computing the speed of sound in air with a simple experimental procedure.

Multi-Sensor Integration to Map Odor Distribution for the Detection of Chemical Sources.

PubMed

Gao, Xiang; Acar, Levent

2016-07-04

This paper addresses the problem of mapping odor distribution derived from a chemical source using multi-sensor integration and reasoning system design. Odor localization is the problem of finding the source of an odor or other volatile chemical. Most localization methods require a mobile vehicle to follow an odor plume along its entire path, which is time consuming and may be especially difficult in a cluttered environment. To solve both of the above challenges, this paper proposes a novel algorithm that combines data from odor and anemometer sensors, and combine sensors' data at different positions. Initially, a multi-sensor integration method, together with the path of airflow was used to map the pattern of odor particle movement. Then, more sensors are introduced at specific regions to determine the probable location of the odor source. Finally, the results of odor source location simulation and a real experiment are presented.

Development of superconducting YBa2Cu3O(x) wires with low resistance electrical contacts

NASA Astrophysics Data System (ADS)

Buoncristiani, A. M.; Byvik, C. E.; Caton, R.; Selim, R.; Lee, B. I.; Modi, V.; Sherrill, M.; Leigh, H. D.; Fain, C. C.; Lewis, G.

Materials exhibiting superconductivity above liquid nitrogen temperatures (77 K) will enable new applications of this phenomena. One of the first commercial applications of this technology will be superconducting magnets for medical imaging. However, a large number of aerospace applications of the high temperature superconducting materials have also been identified. These include magnetic suspension and balance of models in wind tunnels and resistanceless leads to anemometers. The development of superconducting wires fabricated from the ceramic materials is critical for these applications. The progress in application of a patented fiber process developed by Clemson University for the fabrication of superconducting wires is reviewed. The effect of particle size and heat treatment on the quality of materials is discussed. Recent advances made at Christopher Newport College in the development of micro-ohm resistance electrical contacts which are capable of carrying the highest reported direct current to this material is presented.

Stator hub treatment study

NASA Technical Reports Server (NTRS)

Wisler, D. C.; Hilvers, D. E.

1974-01-01

The results of an experimental research program to investigate the potential of improving compressor stall margin by the application of hub treatment are presented. Extensive tuft probing showed that the two-stage, 0.5 radius ratio compressor selected for the test was indeed hub critical. Circumferential groove and baffled wide blade angle slot hub treatments under the stators were tested. Performance measurements were made with total and static pressure probes, wall static pressure taps, flow angle measuring instrumentation and hot film anemometers. Stator hub treatment was not found to be effective in improving compressor stall margin by delaying the point of onset of rotating stall or in modifying compressor performance for any of the configurations tested. Extensive regions of separated flow were observed on the suction surface of the stators near the hub. However, the treatment did not delay the point where flow separation in the stator hub region becomes apparent.

A case study of air quality above an urban roof top vegetable farm.

PubMed

Tong, Zheming; Whitlow, Thomas H; Landers, Andrew; Flanner, Benjamin

2016-01-01

The effect of elevation and rooftop configuration on local air quality was investigated at the Brooklyn Grange rooftop farm during a short-term observational campaign. Using multiple particle counters and sonic anemometers deployed along vertical gradients, we found that PM2.5 concentration decayed with height above the street. Samples adjacent to the street had the highest average PM2.5 concentration and frequent stochastic spikes above background. Rooftop observations 26 m above ground showed 7-33% reductions in average PM2.5 concentration compared with the curbside and had far fewer spikes. A relationship between the vertical extinction rate of PM2.5 and atmospheric stability was found whereby less unstable atmosphere and greater wind shear led to greater PM2.5 extinction due to damped vertical motion of air. Copyright © 2015 Elsevier Ltd. All rights reserved.

Application of rotor mounted pressure transducers to analysis of inlet turbulence. [flow distortion in turbofan engine inlet

NASA Technical Reports Server (NTRS)

Hanson, D. B.

1976-01-01

Miniature pressure transducers installed near the leading edge of a fan blade were used to diagnose the non-uniform flow entering a subsonic tip speed turbofan on a static test stand. The pressure response of the blade to the inlet flow variations was plotted in a form which shows the space-time history of disturbances ingested by the rotor. Also, periodically sampled data values were auto- and cross-correlated as if they had been acquired from fixed hot wire anemometers at 150 equally spaced angles around the inlet. With a clean inlet and low wind, evidence of long, narrow turbulence eddies was easily found both in the boundary layer of the fan duct and outside the boundary layer. The role of the boundary layer was to follow and amplify disturbances in the outer flow. These eddies frequently moved around the inlet with a corkscrew motion as they passed through.

Bisecting Microfluidic Channels with Metallic Nanowires Fabricated by Nanoskiving.

PubMed

Kalkman, Gerard A; Zhang, Yanxi; Monachino, Enrico; Mathwig, Klaus; Kamminga, Machteld E; Pourhossein, Parisa; Oomen, Pieter E; Stratmann, Sarah A; Zhao, Zhiyuan; van Oijen, Antoine M; Verpoorte, Elisabeth; Chiechi, Ryan C

2016-02-23

This paper describes the fabrication of millimeter-long gold nanowires that bisect the center of microfluidic channels. We fabricated the nanowires by nanoskiving and then suspended them over a trench in a glass structure. The channel was sealed by bonding it to a complementary poly(dimethylsiloxane) structure. The resulting structures place the nanowires in the region of highest flow, as opposed to the walls, where it approaches zero, and expose their entire surface area to fluid. We demonstrate active functionality, by constructing a hot-wire anemometer to measure flow through determining the change in resistance of the nanowire as a function of heat dissipation at low voltage (<5 V). Further, passive functionality is demonstrated by visualizing individual, fluorescently labeled DNA molecules attached to the wires. We measure rates of flow and show that, compared to surface-bound DNA strands, elongation saturates at lower rates of flow and background fluorescence from nonspecific binding is reduced.

Statistical parameters of thermally driven turbulent anabatic flow

NASA Astrophysics Data System (ADS)

Hilel, Roni; Liberzon, Dan

2016-11-01

Field measurements of thermally driven turbulent anabatic flow over a moderate slope are reported. A collocated hot-films-sonic anemometer (Combo) obtained the finer scales of the flow by implementing a Neural Networks based in-situ calibration technique. Eight days of continuous measurements of the wind and temperature fluctuations reviled a diurnal pattern of unstable stratification that forced development of highly turbulent unidirectional up slope flow. Empirical fits of important turbulence statistics were obtained from velocity fluctuations' time series alongside fully resolved spectra of velocity field components and characteristic length scales. TKE and TI showed linear dependence on Re, while velocity derivative skewness and dissipation rates indicated the anisotropic nature of the flow. Empirical fits of normalized velocity fluctuations power density spectra were derived as spectral shapes exhibited high level of similarity. Bursting phenomenon was detected at 15% of the total time. Frequency of occurrence, spectral characteristics and possible generation mechanism are discussed. BSF Grant #2014075.

Gas exchange on Mono Lake and Crowley Lake, California

NASA Technical Reports Server (NTRS)

Wanninkhof, Rik; Ledwell, James R.; Broecker, Wallace S.

1987-01-01

Gas exchange coefficients (k) have been determined for freshwater Crowley Lake and saline Mono Lake through the use of a man-made purposefully injected gas, SF6. The concentration decreased from an initial value of 40 to 4 pmol/L for Mono Lake and from 20 to 1 pmol/L for Crowley lake over a period of 6 wks. Wind-speed (u) records from anemometers on the shore of each lake made it possible to determine the relationship between k and u. The average u and k values for the experiment were identical for the two lakes, despite the large chemical differences. It is estimated that, for the u values observed over Mono Lake from July to December 1984, the exchange of CO2 occurred 2.5 times faster than without chemical enhancement. This is a factor of 4 lower than needed to explain the high invasion rate of C-14 produced by nuclear bomb tests.

Optimizing Lidar Scanning Strategies for Wind Energy Measurements (Invited)

NASA Astrophysics Data System (ADS)

Newman, J. F.; Bonin, T. A.; Klein, P.; Wharton, S.; Chilson, P. B.

2013-12-01

Environmental concerns and rising fossil fuel prices have prompted rapid development in the renewable energy sector. Wind energy, in particular, has become increasingly popular in the United States. However, the intermittency of available wind energy makes it difficult to integrate wind energy into the power grid. Thus, the expansion and successful implementation of wind energy requires accurate wind resource assessments and wind power forecasts. The actual power produced by a turbine is affected by the wind speeds and turbulence levels experienced across the turbine rotor disk. Because of the range of measurement heights required for wind power estimation, remote sensing devices (e.g., lidar) are ideally suited for these purposes. However, the volume averaging inherent in remote sensing technology produces turbulence estimates that are different from those estimated by a sonic anemometer mounted on a standard meteorological tower. In addition, most lidars intended for wind energy purposes utilize a standard Doppler beam-swinging or Velocity-Azimuth Display technique to estimate the three-dimensional wind vector. These scanning strategies are ideal for measuring mean wind speeds but are likely inadequate for measuring turbulence. In order to examine the impact of different lidar scanning strategies on turbulence measurements, a WindCube lidar, a scanning Halo lidar, and a scanning Galion lidar were deployed at the Southern Great Plains Atmospheric Radiation Measurement (ARM) site in Summer 2013. Existing instrumentation at the ARM site, including a 60-m meteorological tower and an additional scanning Halo lidar, were used in conjunction with the deployed lidars to evaluate several user-defined scanning strategies. For part of the experiment, all three scanning lidars were pointed at approximately the same point in space and a tri-Doppler analysis was completed to calculate the three-dimensional wind vector every 1 second. In another part of the experiment, one of the scanning lidars ran a Doppler beam-swinging technique identical to that used by the WindCube lidar while another scanning lidar used a novel six-beam technique that has been presented in the literature as a better alternative for measuring turbulence. In this presentation, turbulence measurements from these techniques are compared to turbulence measured by the WindCube lidar and sonic anemometers on the 60-m meteorological tower. In addition, recommendations are made for lidar measurement campaigns for wind energy applications.

Volumetric LiDAR scanning of a wind turbine wake and comparison with a 3D analytical wake model

NASA Astrophysics Data System (ADS)

Carbajo Fuertes, Fernando; Porté-Agel, Fernando

2016-04-01

A correct estimation of the future power production is of capital importance whenever the feasibility of a future wind farm is being studied. This power estimation relies mostly on three aspects: (1) a reliable measurement of the wind resource in the area, (2) a well-established power curve of the future wind turbines and, (3) an accurate characterization of the wake effects; the latter being arguably the most challenging one due to the complexity of the phenomenon and the lack of extensive full-scale data sets that could be used to validate analytical or numerical models. The current project addresses the problem of obtaining a volumetric description of a full-scale wake of a 2MW wind turbine in terms of velocity deficit and turbulence intensity using three scanning wind LiDARs and two sonic anemometers. The characterization of the upstream flow conditions is done by one scanning LiDAR and two sonic anemometers, which have been used to calculate incoming vertical profiles of horizontal wind speed, wind direction and an approximation to turbulence intensity, as well as the thermal stability of the atmospheric boundary layer. The characterization of the wake is done by two scanning LiDARs working simultaneously and pointing downstream from the base of the wind turbine. The direct LiDAR measurements in terms of radial wind speed can be corrected using the upstream conditions in order to provide good estimations of the horizontal wind speed at any point downstream of the wind turbine. All this data combined allow for the volumetric reconstruction of the wake in terms of velocity deficit as well as turbulence intensity. Finally, the predictions of a 3D analytical model [1] are compared to the 3D LiDAR measurements of the wind turbine. The model is derived by applying the laws of conservation of mass and momentum and assuming a Gaussian distribution for the velocity deficit in the wake. This model has already been validated using high resolution wind-tunnel measurements and large-eddy simulation (LES) data of miniature wind turbine wakes, as well as LES data of real-scale wind-turbine wakes, but not yet with full-scale wind turbine wake measurements. [1] M. Bastankhah and F. Porté-Agel. A New Analytical Model For Wind-Turbine Wakes, in Renewable Energy, vol. 70, p. 116-123, 2014.

Wind and flux measurements in a windfarm co-located with agricultural production (Invited)

NASA Astrophysics Data System (ADS)

Takle, E. S.; Prueger, J. H.; Rajewski, D. A.; Lundquist, J. K.; Aitken, M.; Rhodes, M. E.; Deppe, A. J.; Goodman, F. E.; Carter, K. C.; Mattison, L.; Rabideau, S. L.; Rosenberg, A. J.; Whitfield, C. L.; Hatfield, J.

2010-12-01

Co-locating wind farms in pre-existing agricultural fields represents multiple land uses for which there may be interactions. Agricultural producers have raised questions about the possible impact of changes in wind speed and turbulence on pollination, dew formation, and conditions favorable for diseases. During summer 2010 we measured wind speed and surface fluxes within a wind farm that was co-located with a landscape covered by corn and soybeans in central Iowa. We erected four 9.14 m towers in corn fields upwind and downwind of lines of 1.5 MW turbines. All towers were instrumented with sonic anemometers at 6.45 m above ground, three-cup anemometers at 9.06 m ,and two temperature and relative humidity probes at 5.30 and 9.06 m. In addition, LiCor 7500 CO2/H2O flux analyzers were mounted at 6.45 m on two towers. At the beginning of the field campaign (late June) the corn had a height of about 1.3 m and grew to about 2.2 m at maturity in late July. For a 2-week period beginning late June a vertically pointing lidar was located near a flux tower downwind of one of the turbines and collected horizontal winds from 40 m to 200 m above ground. Twenty-Hz data from the eddy covariance systems were recorded as were 5-min averaged values of wind speed, temperature, humidity, and fluxes of heat, momentum, moisture and CO2 day and night under a wide variety of weather conditions, including a two-week period when the turbines were shut down. Numerical simulations with the WRF (Weather Research and Forecast) model for select periods with no turbine influence provide opportunities for comparing modeled and measured values of surface conditions and vertical wind profiles. Results show clear evidence of changes in flow field conditions at the surface that influence fluxes. We will discuss diurnal changes in fluxes and influence of turbines. Lidar measurements of vertical profiles of wind speed compared against modeled undisturbed flow fields behind a turbine reveal significant momentum extraction and creation of regions of strong shear leading to mechanical generation of turbulence. Potential impacts on agricultural crops will be discussed.

Mobile Measurement of Methane and Ethane for the Detection and Attribution of Natural Gas Pipeline Leaks Using Off-Axis Integrated Output Spectroscopy

NASA Astrophysics Data System (ADS)

Leen, J. B.; Spillane, S.; Gardner, A.; Hansen, P. C.; Gupta, M.; Baer, D. S.

2015-12-01

Natural gas leaks pose a risk to public safety both because of potential explosions as well as from the greenhouse gas potential of fugitive methane. The rapid and cost effective detection of leaks in natural gas distribution is critical to providing a system that is safe for the public and the environment. Detection of methane from a mobile platform (vehicles, aircraft, etc.) is an accepted method of identifying leaks. A robust approach to differentiating pipeline gas (thermogenic) from other biogenic sources is the detection of ethane along with methane. Ethane is present in nearly all thermogenic gas but not in biogenic sources and its presence can be used to positively identify a gas sample. We present a mobile system for the simultaneous measurement of methane and ethane that is capable of detecting pipeline leaks and differentiating pipeline gas from other biogenic sources such as landfills, swamps, sewers, and enteric fermentation. The mobile system consists of a high precision GPS, sonic anemometer, and methane/ethane analyzer based on off-axis integrated cavity output spectroscopy (OA-ICOS). In order to minimize the system cost and facilitate the wide use of mobile leak detection, the analyzer operates in the near-infrared portion of the spectrum where lasers and optics are significantly less costly than in the mid-infrared. The analyzer is capable of detecting methane with a precision of <2 ppb (1σ in 1 sec) and detecting ethane with a precision of <30 ppb (1σ in 1 sec). Additionally, measurement rates of 5 Hz allow for detection of leaks at speeds up to 50 mph. The sonic anemometer, GPS and analyzer inlet are mounted to a generic roof rack for attachment to available fleet vehicles. The system can detect leaks having a downwind concentration of as little as 10 ppb of methane above ambient, while leaks 500 ppb above ambient can be identified as thermogenic with greater than 99% certainty (for gas with 6% ethane). Finally, analysis of wind data provides an estimate of leak direction and distance. The system presented provides a robust, cost effective solution to natural gas leak detection and attribution to maximize safety and minimize greenhouse gas impacts of distribution systems.

An experimental study of the impact of trees and urban form on the turbulent dispersion of heavy particles from near ground point sources

NASA Astrophysics Data System (ADS)

Stoll, R., II; Christen, A.; Mahaffee, W.; Salesky, S.; Therias, A.; Caitlin, S.

2016-12-01

Pollution in the form of small particles has a strong impact on a wide variety of urban processes that play an important role in the function of urban ecosystems and ultimately human health and well-being. As a result, a substantial body of research exists on the sources, sinks, and transport characteristics of urban particulate matter. Most of the existing experimental work examining point sources employed gases (e.g., SF6) as the working medium. Furthermore, the focus of most studies has been on the dispersion of pollutants far from the source location. Here, our focus is on the turbulent dispersion of heavy particles in the near source region of a suburban neighborhood. To this end, we conducted a series of heavy particle releases in the Sunset neighborhood of Vancouver, Canada during June, 2017. The particles where dispersed from a near ground point source at two different locations. The Sunset neighborhood is composed mostly of single dwelling detached houses and has been used in numerous previous urban studies. One of the release points was just upwind of a 4-way intersection and the other in the middle of a contiguous block of houses. Each location had a significant density of trees. A minimum of four different successful release events were conducted at each site. During each release, fluorescing micro particles (mean diameter approx. 30 micron) were released from ultrasonic atomizer nozzles for a duration of approximately 20 minutes. The particles where sampled at 50 locations (1.5 m height) in the area downwind of the release over distances from 1-15 times the mean canopy height ( 6 m) using rotating impaction traps. In addition to the 50 sampler locations, instantaneous wind velocities were measured with eight sonic anemometers distributed horizontally and vertically throughout the release area. The resulting particle plume distributions indicate a strong impact of local urban form in the near source region and a high degree of sensitivity to the local wind direction measured from the sonic anemometers. In addition to presenting the experimental data, initial comparisons to a Lagrangian particle dispersion model driven by a mass consistent diagnostic wind field will be presented.

An experimental study of the impact of trees and urban form on the turbulent dispersion of heavy particles from near ground point sources

NASA Astrophysics Data System (ADS)

Stoll, R., II; Christen, A.; Mahaffee, W.; Salesky, S.; Therias, A.; Caitlin, S.

2017-12-01

Pollution in the form of small particles has a strong impact on a wide variety of urban processes that play an important role in the function of urban ecosystems and ultimately human health and well-being. As a result, a substantial body of research exists on the sources, sinks, and transport characteristics of urban particulate matter. Most of the existing experimental work examining point sources employed gases (e.g., SF6) as the working medium. Furthermore, the focus of most studies has been on the dispersion of pollutants far from the source location. Here, our focus is on the turbulent dispersion of heavy particles in the near source region of a suburban neighborhood. To this end, we conducted a series of heavy particle releases in the Sunset neighborhood of Vancouver, Canada during June, 2017. The particles where dispersed from a near ground point source at two different locations. The Sunset neighborhood is composed mostly of single dwelling detached houses and has been used in numerous previous urban studies. One of the release points was just upwind of a 4-way intersection and the other in the middle of a contiguous block of houses. Each location had a significant density of trees. A minimum of four different successful release events were conducted at each site. During each release, fluorescing micro particles (mean diameter approx. 30 micron) were released from ultrasonic atomizer nozzles for a duration of approximately 20 minutes. The particles where sampled at 50 locations (1.5 m height) in the area downwind of the release over distances from 1-15 times the mean canopy height ( 6 m) using rotating impaction traps. In addition to the 50 sampler locations, instantaneous wind velocities were measured with eight sonic anemometers distributed horizontally and vertically throughout the release area. The resulting particle plume distributions indicate a strong impact of local urban form in the near source region and a high degree of sensitivity to the local wind direction measured from the sonic anemometers. In addition to presenting the experimental data, initial comparisons to a Lagrangian particle dispersion model driven by a mass consistent diagnostic wind field will be presented.

An error reduction algorithm to improve lidar turbulence estimates for wind energy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Newman, Jennifer F.; Clifton, Andrew

Remote-sensing devices such as lidars are currently being investigated as alternatives to cup anemometers on meteorological towers for the measurement of wind speed and direction. Although lidars can measure mean wind speeds at heights spanning an entire turbine rotor disk and can be easily moved from one location to another, they measure different values of turbulence than an instrument on a tower. Current methods for improving lidar turbulence estimates include the use of analytical turbulence models and expensive scanning lidars. While these methods provide accurate results in a research setting, they cannot be easily applied to smaller, vertically profiling lidarsmore » in locations where high-resolution sonic anemometer data are not available. Thus, there is clearly a need for a turbulence error reduction model that is simpler and more easily applicable to lidars that are used in the wind energy industry. In this work, a new turbulence error reduction algorithm for lidars is described. The Lidar Turbulence Error Reduction Algorithm, L-TERRA, can be applied using only data from a stand-alone vertically profiling lidar and requires minimal training with meteorological tower data. The basis of L-TERRA is a series of physics-based corrections that are applied to the lidar data to mitigate errors from instrument noise, volume averaging, and variance contamination. These corrections are applied in conjunction with a trained machine-learning model to improve turbulence estimates from a vertically profiling WINDCUBE v2 lidar. The lessons learned from creating the L-TERRA model for a WINDCUBE v2 lidar can also be applied to other lidar devices. L-TERRA was tested on data from two sites in the Southern Plains region of the United States. The physics-based corrections in L-TERRA brought regression line slopes much closer to 1 at both sites and significantly reduced the sensitivity of lidar turbulence errors to atmospheric stability. The accuracy of machine-learning methods in L-TERRA was highly dependent on the input variables and training dataset used, suggesting that machine learning may not be the best technique for reducing lidar turbulence intensity (TI) error. Future work will include the use of a lidar simulator to better understand how different factors affect lidar turbulence error and to determine how these errors can be reduced using information from a stand-alone lidar.« less

An error reduction algorithm to improve lidar turbulence estimates for wind energy

DOE PAGES

Newman, Jennifer F.; Clifton, Andrew

2017-02-10

Remote-sensing devices such as lidars are currently being investigated as alternatives to cup anemometers on meteorological towers for the measurement of wind speed and direction. Although lidars can measure mean wind speeds at heights spanning an entire turbine rotor disk and can be easily moved from one location to another, they measure different values of turbulence than an instrument on a tower. Current methods for improving lidar turbulence estimates include the use of analytical turbulence models and expensive scanning lidars. While these methods provide accurate results in a research setting, they cannot be easily applied to smaller, vertically profiling lidarsmore » in locations where high-resolution sonic anemometer data are not available. Thus, there is clearly a need for a turbulence error reduction model that is simpler and more easily applicable to lidars that are used in the wind energy industry. In this work, a new turbulence error reduction algorithm for lidars is described. The Lidar Turbulence Error Reduction Algorithm, L-TERRA, can be applied using only data from a stand-alone vertically profiling lidar and requires minimal training with meteorological tower data. The basis of L-TERRA is a series of physics-based corrections that are applied to the lidar data to mitigate errors from instrument noise, volume averaging, and variance contamination. These corrections are applied in conjunction with a trained machine-learning model to improve turbulence estimates from a vertically profiling WINDCUBE v2 lidar. The lessons learned from creating the L-TERRA model for a WINDCUBE v2 lidar can also be applied to other lidar devices. L-TERRA was tested on data from two sites in the Southern Plains region of the United States. The physics-based corrections in L-TERRA brought regression line slopes much closer to 1 at both sites and significantly reduced the sensitivity of lidar turbulence errors to atmospheric stability. The accuracy of machine-learning methods in L-TERRA was highly dependent on the input variables and training dataset used, suggesting that machine learning may not be the best technique for reducing lidar turbulence intensity (TI) error. Future work will include the use of a lidar simulator to better understand how different factors affect lidar turbulence error and to determine how these errors can be reduced using information from a stand-alone lidar.« less

Eddy covariance measurements of sea spray particles over the Atlantic Ocean

NASA Astrophysics Data System (ADS)

Norris, S. J.; Brooks, I. M.; de Leeuw, G.; Smith, M. H.; Moerman, M.; Lingard, J. J. N.

2008-02-01

Most estimates of sea spray aerosol source functions have used indirect means to infer the rate of production as a function of wind speed. Only recently has the technology become available to make high frequency measurements of aerosol spectra suitable for direct eddy correlation determination of the sea spray particle flux. This was accomplished in this study by combining a newly developed fast aerosol particle counter with an ultrasonic anemometer which allowed for eddy covariance measurements of size-segregated particle fluxes. The aerosol instrument is the Compact Lightweight Aerosol Spectrometer Probe (CLASP) - capable of measuring 8-channel size spectra for mean radii between 0.15 and 3.5 µm at 10 Hz. The first successful measurements were made during the Waves, Air Sea Fluxes, Aerosol and Bubbles (WASFAB) field campaign in October 2005 in Duck (NC, USA). The method and initial results are presented and comparisons are made with recent sea spray source functions from the literature.

Drop size distribution and air velocity measurements in air assist swirl atomizer sprays

NASA Technical Reports Server (NTRS)

Mao, C.-P.; Oechsle, V.; Chigier, N.

1987-01-01

Detailed measurements of mean drop size (SMD) and size distribution parameters have been made using a Fraunhofer diffraction particle sizing instrument in a series of sprays generated by an air assist swirl atomizer. Thirty-six different combinations of fuel and air mass flow rates were examined with liquid flow rates up to 14 lbm/hr and atomizing air flow rates up to 10 lbm/hr. Linear relationships were found between SMD and liquid to air mass flow rate ratios. SMD increased with distance downstream along the center line and also with radial distance from the axis. Increase in obscuration with distance downstream was due to an increase in number density of particles as the result of deceleration of drops and an increase in the exposed path length of the laser beam. Velocity components of the atomizing air flow field measured by a laser anemometer show swirling jet air flow fields with solid body rotation in the core and free vortex flow in the outer regions.

Analysis of an existing experiment on the interaction of acoustic waves with a laminar boundary layer

NASA Technical Reports Server (NTRS)

Schopper, M. R.

1982-01-01

The hot-wire anemometer amplitude data contained in the 1977 report of P. J. Shapiro entitled, ""The Influence of Sound Upon Laminar Boundary'' were reevaluated. Because the low-Reynolds number boundary layer disturbance data were misinterpreted, an effort was made to improve the corresponding disturbance growth rate curves. The data are modeled as the sum of upstream and downstream propagating acoustic waves and a wave representing the Tollmien-Schlichting (TS) wave. The amplitude and phase velocity of the latter wave were then adjusted so that the total signal reasonably matched the amplitude and phase angle hot-wire data along the plate laminar boundary layer. The revised rates show growth occurring further upstream than Shapiro found. It appears that the premature growth is due to the adverse pressure gradient created by the shape of the plate. Basic elements of sound propagation in ducts and the experimental and theoretical acoustic-stability literature are reviewed.

A method for the measurement and the statistical analysis of atmospheric turbulence

NASA Technical Reports Server (NTRS)

Tieleman, H. W.; Tavoularis, S. C.

1974-01-01

The instantaneous values of output voltages representing the wind velocity vector and the temperature at different elevations of the 250-foot meteorological tower located at NASA Wallops Flight Center are provided with the three dimensional split-film TSI Model 1080 anemometer system. The output voltages are sampled at a rate of one every 5 milliseconds, digitized and stored on digital magnetic tapes for a time period of approximately 40 minutes, with the use of a specially designed data acqusition system. A new calibration procedure permits the conversion of the digital voltages to the respective values of the temperature and the velocity components in a Cartesian coordinate system connected with the TSI probe with considerable accuracy. Power, cross, coincidence and quadrature spectra of the wind components and the temperature are obtained with the use of the fast Fourier transform. The cosine taper data window and ensemble and frequency smoothing techniques are used to provide smooth estimates of the spectral functions.

Vertical profiles of the 3-D wind velocity retrieved from multiple wind lidars performing triple range-height-indicator scans

DOE PAGES

Debnath, Mithu; Iungo, G. Valerio; Ashton, Ryan; ...

2017-02-06

Vertical profiles of 3-D wind velocity are retrieved from triple range-height-indicator (RHI) scans performed with multiple simultaneous scanning Doppler wind lidars. This test is part of the eXperimental Planetary boundary layer Instrumentation Assessment (XPIA) campaign carried out at the Boulder Atmospheric Observatory. The three wind velocity components are retrieved and then compared with the data acquired through various profiling wind lidars and high-frequency wind data obtained from sonic anemometers installed on a 300 m meteorological tower. The results show that the magnitude of the horizontal wind velocity and the wind direction obtained from the triple RHI scans are generally retrieved withmore » good accuracy. Furthermore, poor accuracy is obtained for the evaluation of the vertical velocity, which is mainly due to its typically smaller magnitude and to the error propagation connected with the data retrieval procedure and accuracy in the experimental setup.« less

Two Capacitive Micro-Machined Ultrasonic Transducers for Wind Speed Measurement

PubMed Central

Bui, Gia Thinh; Jiang, Yu-Tsung; Pang, Da-Chen

2016-01-01

This paper presents a new wind speed measurement method using a single capacitive micro-machined ultrasonic transducer (CMUT). The CMUT was arranged perpendicular to the direction of the wind flow, and a reflector was set up a short distance away, facing the CMUT. To reduce the size, weight, cost, and power consumption of conventional ultrasonic anemometers this study proposes two CMUT designs for the measurement of wind speed using either the amplitude of the signal or the time of flight (TOF). Each CMUT with a double array element design can transmit and receive signals in five different operation modes. Experiments showed that the two CMUT designs utilizing the TOF were better than those utilizing the amplitude of the signal for wind speed measurements ranging from 1 m/s to 10 m/s, providing a measurement error of less than 0.2 m/s. These results indicate that the sensitivity of the TOF is independent of the five operation modes. PMID:27271625

Development of Point Doppler Velocimetry for Flow Field Investigations

NASA Technical Reports Server (NTRS)

Cavone, Angelo A.; Meyers, James F.; Lee, Joseph W.

2006-01-01

A Point Doppler Velocimeter (pDv) has been developed using a vapor-limited iodine cell as the sensing medium. The iodine cell is utilized to directly measure the Doppler shift frequency of laser light scattered from submicron particles suspended within a fluid flow. The measured Doppler shift can then be used to compute the velocity of the particles, and hence the fluid. Since this approach does not require resolution of scattered light from individual particles, the potential exists to obtain temporally continuous signals that could be uniformly sampled in the manner as a hot wire anemometer. This leads to the possibility of obtaining flow turbulence power spectra without the limitations of fringe-type laser velocimetry. The development program consisted of a methodical investigation of the technology coupled with the solution of practical engineering problems to produce a usable measurement system. The paper outlines this development along with the evaluation of the resulting system as compared to primary standards and other measurement technologies.

A user's guide to the Langley 16- by 24-inch water tunnel

NASA Technical Reports Server (NTRS)

Pendergraft, Odis C., Jr.; Neuhart, Dan H.; Kariya, Timmy T.

1992-01-01

The Langley 16 x 24 inch Water Tunnel is described in detail, along with all the supporting equipment used in its operation as a flow visualization test facility. These include the laser and incandescent lighting systems; and the photographic, video, and laser fluorescence anemometer systems used to make permanent records of the test results. This facility is a closed return water tunnel capable of test section velocities from 0 to 0.75 feet per second with flow through the 16 x 24 inch test section in a downward (vertical) direction. The velocity normally used for testing is 0.25 feet per second where the most uniform flow occurs, and is slow enough to easily observe flow phenomena such as vortex flow with the unaided eye. An overview is given of the operational characteristics, procedures, and capabilities of the water tunnel to potential users of the facility so that they may determine if the facility meets their needs for a planned study.

Two Capacitive Micro-Machined Ultrasonic Transducers for Wind Speed Measurement.

PubMed

Bui, Gia Thinh; Jiang, Yu-Tsung; Pang, Da-Chen

2016-06-02

This paper presents a new wind speed measurement method using a single capacitive micro-machined ultrasonic transducer (CMUT). The CMUT was arranged perpendicular to the direction of the wind flow, and a reflector was set up a short distance away, facing the CMUT. To reduce the size, weight, cost, and power consumption of conventional ultrasonic anemometers this study proposes two CMUT designs for the measurement of wind speed using either the amplitude of the signal or the time of flight (TOF). Each CMUT with a double array element design can transmit and receive signals in five different operation modes. Experiments showed that the two CMUT designs utilizing the TOF were better than those utilizing the amplitude of the signal for wind speed measurements ranging from 1 m/s to 10 m/s, providing a measurement error of less than 0.2 m/s. These results indicate that the sensitivity of the TOF is independent of the five operation modes.

An Experimental Investigation of Wall-Cooling Effects on Hypersonic Boundary-Layer Stability in a Quiet Wind Tunnel

NASA Technical Reports Server (NTRS)

Blanchard, Alan E.; Selby, Gregory V.

1996-01-01

One of the primary reasons for developing quiet tunnels is for the investigation of high-speed boundary-layer stability and transition phenomena without the transition-promoting effects of acoustic radiation from tunnel walls. In this experiment, a flared-cone model under adiabatic- and cooled-wall conditions was placed in a calibrated, 'quiet' Mach 6 flow and the stability of the boundary layer was investigated using a prototype constant-voltage anemometer. The results were compared with linear-stability theory predictions and good agreement was found in the prediction of second-mode frequencies and growth. In addition, the same 'N=10' criterion used to predict boundary-layer transition in subsonic, transonic, and supersonic flows was found to be applicable for the hypersonic flow regime as well. Under cooled-wall conditions, a unique set of continuous spectra data was acquired that documents the linear, nonlinear, and breakdown regions associated with the transition of hypersonic flow under low-noise conditions.

A gas-puff-driven theta pinch for plasma-surface interaction studies

NASA Astrophysics Data System (ADS)

Jung, Soonwook; Kesler, Leigh; Yun, Hyun-Ho; Curreli, Davide; Andruczyk, Daniel; Ruzic, David

2012-10-01

DEVeX is a theta pinch device used to investigate fusion-related material interaction such as vapor shielding and ICRF antenna interactions with plasma-pulses in a laboratory setting. The simulator is required to produce high heat-flux plasma enough to induce temperature gradient high enough to study extreme conditions happened in a plasma fusion reactor. In order to achieve it, DEVeX is reconfigured to be combined with gas puff system as gas puffing may reduce heat flux loss resulting from collisions with neutral. A gas puff system as well as a conical gas nozzle is manufactured and several diagnostics including hot wire anemometer and fast ionization gauge are carried out to quantitatively estimate the supersonic flow of gas. Energy deposited on the target for gas puffing and static-filled conditions is measured with thermocouples and its application to TELS, an innovative concept utilizing a thermoelectric-driven liquid metal flow for plasma facing component, is discussed.

Wind power in Jamaica

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, A.A.; Daniel, A.R.; Daniel, S.T.

1990-01-01

Parameters to evaluate the potential for using wind energy to generate electricity in Jamaica were obtained. These include the average wind power scaled to a height of 20 m at existing weather stations and temporary anemometer sites, the variation in annual and monthly wind power, and the frequency distribution of wind speed and wind energy available. Four small commercial turbines were assumed to be operating at some of the sites, and the estimated energy captured by them, the time they operated above their cut-in speed and their capacity factors were also determined. Diurnal variations of wind speed and prevailing windmore » directions are discussed and a map showing wind power at various sites was produced. Two stations with long-term averages, Manley and Morant Point, gave results which warranted further investigation. Results from some temporary stations are also encouraging. Mean wind speeds at two other sites in the Caribbean are given for comparison. A method for estimating the power exponent for scaling the wind speed from climatic data is described in Appendix 2.« less

Study of Oscillating Electroosmotic Flows with High Temporal and Spatial Resolution.

PubMed

Zhao, Wei; Liu, Xin; Yang, Fang; Wang, Kaige; Bai, Jintao; Qiao, Rui; Wang, Guiren

2018-02-06

Near-wall velocity of oscillating electroosmotic flow (OEOF) driven by an AC electric field has been investigated using a laser-induced fluorescence photobleaching anemometer (LIFPA). For the first time, an up to 3 kHz velocity response of OEOF has been successfully measured experimentally, even though the oscillating velocity is as low as 600 nm/s. It is found that the oscillating velocity decays with the forcing frequency f f as f f -0.66 . In the investigated range of electric field intensity (E A ), below 1 kHz, the linear relation between oscillating velocity and E A is also observed. Because the oscillating velocity at high frequency is very small, the contribution of noise to velocity measurement is significant, and it is discussed in this manuscript. The investigation reveals the instantaneous response of OEOF to the temporal change of electric fields, which exists in almost all AC electrokinetic flows. Furthermore, the experimental observations are important for designing OEOF-based micro/nanofluidics systems.

Modeling measured glottal volume velocity waveforms.

PubMed

Verneuil, Andrew; Berry, David A; Kreiman, Jody; Gerratt, Bruce R; Ye, Ming; Berke, Gerald S

2003-02-01

The source-filter theory of speech production describes a glottal energy source (volume velocity waveform) that is filtered by the vocal tract and radiates from the mouth as phonation. The characteristics of the volume velocity waveform, the source that drives phonation, have been estimated, but never directly measured at the glottis. To accomplish this measurement, constant temperature anemometer probes were used in an in vivo canine constant pressure model of phonation. A 3-probe array was positioned supraglottically, and an endoscopic camera was positioned subglottically. Simultaneous recordings of airflow velocity (using anemometry) and glottal area (using stroboscopy) were made in 3 animals. Glottal airflow velocities and areas were combined to produce direct measurements of glottal volume velocity waveforms. The anterior and middle parts of the glottis contributed significantly to the volume velocity waveform, with less contribution from the posterior part of the glottis. The measured volume velocity waveforms were successfully fitted to a well-known laryngeal airflow model. A noninvasive measured volume velocity waveform holds promise for future clinical use.

Radiation mechanism for the aerodynamic sound of gears - An explanation for the radiation process by air flow observation

NASA Astrophysics Data System (ADS)

Houjoh, Haruo

1992-12-01

One specific feature of the aerodynamic sound produced at the face end region is that the radiation becomes equally weak by filling root spaces as by shortening the center distance. However, one can easily expect that such actions make the air flow faster, and consequently make the sound louder. This paper attempts to reveal the reason for such a feature. First, air flow induced by the pumping action of the gear pair was analyzed regarding a series of root spaces as volume varying cavities which have channels to adjacent cavities as well as the exit/inlet at the face ends. The numerical analysis was verified by the hot wire anemometer measurement. Next, from the obtained flow response, the sound source was estimated to be a combination of symmetrically distributed simple sources. Taking the effect of either the center distance or root filling into consideration, it is shown that the simplified model can explain such a feature rationally.

Dynamic "Scanning-Mode" Meniscus Confined Electrodepositing and Micropatterning of Individually Addressable Ultraconductive Copper Line Arrays.

PubMed

Lei, Yu; Zhang, Xianyun; Xu, Dingding; Yu, Minfeng; Yi, Zhiran; Li, Zhixiang; Sun, Aihua; Xu, Gaojie; Cui, Ping; Guo, Jianjun

2018-05-03

Micro- and nanopatterning of cost-effective addressable metallic nanostructures has been a long endeavor in terms of both scientific understanding and industrial needs. Herein, a simple and efficient dynamic meniscus-confined electrodeposition (MCED) technique for precisely positioned copper line micropatterns with superior electrical conductivity (greater than 1.57 × 10 4 S/cm) on glass, silicon, and gold substrates is reported. An unexpected higher printing speed in the evaporative regime is realized for precisely positioned copper lines patterns with uniform width and height under horizontal scanning-mode. The final line height and width depend on the typical behavior of traditional flow coating process, while the surface morphologies and roughness are mainly governed by evaporation-driven electrocrystallization dynamics near the receding moving contact line. Integrated 3D structures and a rapid prototyping of 3D hot-wire anemometer are further demonstrated, which is very important for the freedom integration applications in advanced conceptual devices, such as miniaturized electronics and biomedical sensors and actuators.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Debnath, Mithu; Iungo, Giacomo Valerio; Brewer, W. Alan

During the eXperimental Planetary boundary layer Instrumentation Assessment (XPIA) campaign, which was carried out at the Boulder Atmospheric Observatory (BAO) in spring 2015, multiple-Doppler scanning strategies were carried out with scanning wind lidars and Ka-band radars. Specifically, step–stare measurements were collected simultaneously with three scanning Doppler lidars, while two scanning Ka-band radars carried out simultaneous range height indicator (RHI) scans. The XPIA experiment provided the unique opportunity to compare directly virtual-tower measurements performed simultaneously with Ka-band radars and Doppler wind lidars. Furthermore, multiple-Doppler measurements were assessed against sonic anemometer data acquired from the meteorological tower (met-tower) present at the BAOmore » site and a lidar wind profiler. As a result, this survey shows that – despite the different technologies, measurement volumes and sampling periods used for the lidar and radar measurements – a very good accuracy is achieved for both remote-sensing techniques for probing horizontal wind speed and wind direction with the virtual-tower scanning technique.« less

Effects of inlet distortion on the development of secondary flows in a subsonic axial inlet compressor rotor. Ph.D. Thesis - Toledo Univ., OH

NASA Technical Reports Server (NTRS)

Owen, Albert K.

1991-01-01

Detailed flow measurements were taken inside an isolated axial compressor rotor operating subsonically near peak efficiency. Laser anemometer measurements were made with two inlet velocity profiles. One profile consisted of an unmodified baseline flow, and the second profile was distorted by placing axisymmetric screens on the hub and shroud well upstream of the rotor. A primary flow is defined in the rotor and deviations from this primary flow for each inlet flow condition identified. A comparison between the two flow deviations is made to assess the development of a passage vortex due to the distortion of the inlet flow. A comparison of experimental results with computational predictions from a Navier-Stokes solver showed good agreement between predicted and measured flow. Measured results indicate that a distorted inlet profile has minimal effect on the development of the flow in the rotor passage and the resulting passage vortex.

Markovian properties of wind turbine wakes within a 3x3 array

NASA Astrophysics Data System (ADS)

Melius, Matthew; Tutkun, Murat; Cal, Raúl Bayoán

2012-11-01

Wind turbine arrays have proven to be significant sources of renewable energy. Accurate projections of energy production is difficult to achieve because the wake of a wind turbine is highly intermittent and turbulent. Seeking to further the understanding of the downstream propagation of wind turbine wakes, a stochastic analysis of experimentally obtained turbulent flow data behind a wind turbine was performed. A 3x3 wind turbine array was constructed in the test section of a recirculating wind tunnel where X-wire anemometers were used to collect point velocity statistics. In this work, mathematics of the theory of Markovian processes are applied to obtain a statistical description of longitudinal velocity increments inside the turbine wake using conditional probability density functions. Our results indicate an existence of Markovian properties at scales on the order of the Taylor microscale, λ, which has also been observed and documented in different turbulent flows. This leads to characterization of the multi-point description of the wind turbine wakes using the most recent states of the flow.

Experimental investigation of the turbulent axisymmetric wake with rotation generated by a wind turbine

NASA Astrophysics Data System (ADS)

Dufresne, Nathaniel P.

An experimental investigation of the axial and azimuthal (swirl) velocity field in the wake of a single 3-bladed wind turbine with rotor diameter of 0.91m was conducted, up to 20 diameters downstream. The turbine was positioned in the free stream, near the entrance of the 6m x 2.7m cross section of the University of New Hampshire (UNH) Flow Physics Facility. Velocity measurements were conducted at different rotor loading conditions with blade tip-speed ratios from 2.0 to 2.8. A Pitot-static tube and constant temperature hot-wire anemometer with a multi-wire sensor were used to measure velocity fields. An equilibrium similarity theory for the turbulent axisymmetric wake with rotation was outlined, and first evidence for a new scaling function for the mean swirling velocity component, Wmax ∝ x-1 ∝ U3/2o a was found; where W represents swirl, x represents downstream distance, and Uo, represents the centerline velocity deficit in the wake.

PM2.5 and Carbon Emissions from Prescribed Fire in a Longleaf Pine Ecosystem

NASA Astrophysics Data System (ADS)

Strenfel, S. J.; Clements, C. B.; Hiers, J. K.; Kiefer, C. M.

2008-12-01

Prescribed fires are a frequently utilized land-management tool in the Southeastern US. In order to better characterize emissions and impacts from prescribed fire in longleaf pine ecosystems, in situ data were obtained within the burn perimeter using a 10-m instrumented flux tower. Turbulence and temperature data at 10-m were sampled at 10 Hz using a sonic anemometer and fine-wire thermocouples respectively. Measurements of PM2.5, CO and CO2 emissions were sampled at 10-m within the burn perimeter and PM2.5 and Black Carbon PM2.5 were sampled 0.5 km downwind of the fire front using a 2-m instrumented tripod. Preliminary results indicate PM2.5 and carbon emissions significantly increased during the fire-front passage, and downwind PM concentrations were amplified beyond pre-fire ambient concentrations. In addition, the considerable amount a heat release and flux data gathered from these prescribed fires suggests that near surface atmospheric conditions were directly impacted by increased turbulence generation.

Estimating Variances of Horizontal Wind Fluctuations in Stable Conditions

NASA Astrophysics Data System (ADS)

Luhar, Ashok K.

2010-05-01

Information concerning the average wind speed and the variances of lateral and longitudinal wind velocity fluctuations is required by dispersion models to characterise turbulence in the atmospheric boundary layer. When the winds are weak, the scalar average wind speed and the vector average wind speed need to be clearly distinguished and both lateral and longitudinal wind velocity fluctuations assume equal importance in dispersion calculations. We examine commonly-used methods of estimating these variances from wind-speed and wind-direction statistics measured separately, for example, by a cup anemometer and a wind vane, and evaluate the implied relationship between the scalar and vector wind speeds, using measurements taken under low-wind stable conditions. We highlight several inconsistencies inherent in the existing formulations and show that the widely-used assumption that the lateral velocity variance is equal to the longitudinal velocity variance is not necessarily true. We derive improved relations for the two variances, and although data under stable stratification are considered for comparison, our analysis is applicable more generally.

An experimental study of a self-confined flow with ring-vorticity distribution. Ph.D. Thesis. Final Report

NASA Technical Reports Server (NTRS)

Lin, K. M.; Moore, F. K.

1976-01-01

A new form of self-confined flow was investigated in which a recirculation zone forms away from any solid boundary. An inviscid flow analysis indicated that in a purely meridional axisymmetric flow a stationary, spherical, self-confined region should occur in the center of a streamlined divergent-convergent enlargement zone. The spherical confinement region would be at rest and at constant pressure. Experimental investigations were carried out in a specially built test apparatus to establish the desired confined flow. The streamlined divergent-convergent interior shape of the test section was fabricated according to the theoretical calculation for a particular streamline. The required inlet vorticity distribution was generated by producing a velocity profile with a shaped gauze screen in the straight pipe upstream of the test section. Fluid speed and turbulence intensity were measured with a constant-temperature hot-wire anemometer system. The measured results indicated a very orderly and stable flow field.

Transmission of Mycobacterium chimaera from Heater-Cooler Units during Cardiac Surgery despite an Ultraclean Air Ventilation System.

PubMed

Sommerstein, Rami; Rüegg, Christian; Kohler, Philipp; Bloemberg, Guido; Kuster, Stefan P; Sax, Hugo

2016-06-01

Heater-cooler units (HCUs) were recently identified as a source of Mycobacterium chimaera causing surgical site infections. We investigated transmission of this bacterium from HCUs to the surgical field by using a thermic anemometer and particle counter, videotape of an operating room equipped with an ultraclean laminar airflow ventilation system, and bacterial culture sedimentation plates in a nonventilated room. Smoke from the HCU reached the surgical field in 23 s by merging with ultraclean air. The HCU produced on average 5.2, 139, and 14.8 particles/min in the surgical field at positions Off, On/oriented toward, and On/oriented away, respectively. Culture plates were positive for M. chimaera <5 m from the HCU in the test room. These experiments confirm airborne transmission of M. chimaera aerosols from a contaminated HCU to an open surgical field despite ultraclean air ventilation. Efforts to mitigate infectious risks during surgery should consider contamination from water sources and airflow-generating devices.

Particle-sampling statistics in laser anemometers Sample-and-hold systems and saturable systems

NASA Technical Reports Server (NTRS)

Edwards, R. V.; Jensen, A. S.

1983-01-01

The effect of the data-processing system on the particle statistics obtained with laser anemometry of flows containing suspended particles is examined. Attention is given to the sample and hold processor, a pseudo-analog device which retains the last measurement until a new measurement is made, followed by time-averaging of the data. The second system considered features a dead time, i.e., a saturable system with a significant reset time with storage in a data buffer. It is noted that the saturable system operates independent of the particle arrival rate. The probabilities of a particle arrival in a given time period are calculated for both processing systems. It is shown that the system outputs are dependent on the mean particle flow rate, the flow correlation time, and the flow statistics, indicating that the particle density affects both systems. The results are significant for instances of good correlation between the particle density and velocity, such as occurs near the edge of a jet.

First results of a study on turbulent boundary layers in oscillating flow with a mean adverse pressure gradient

NASA Technical Reports Server (NTRS)

Houdeville, R.; Cousteix, J.

1979-01-01

The development of a turbulent unsteady boundary layer with a mean pressure gradient strong enough to induce separation, in order to complete the extend results obtained for the flat plate configuration is presented. The longitudinal component of the velocity is measured using constant temperature hot wire anemometer. The region where negative velocities exist is investigated with a laser Doppler velocimeter system with BRAGG cells. The boundary layer responds by forced pulsation to the perturbation of potential flow. The unsteady effects observed are very important. The average location of the zero skin friction point moves periodically at the perturbation frequency. Average velocity profiles from different instants in the cycle are compared. The existence of a logarithmic region enables a simple calculation of the maximum phase shift of the velocity in the boundary layer. An attempt of calculation by an integral method of boundary layer development is presented, up to the point where reverse flow starts appearing.

Disturbance Source Separation in Shear Flows Using Blind Source Separation Methods

NASA Astrophysics Data System (ADS)

Gluzman, Igal; Cohen, Jacob; Oshman, Yaakov

2017-11-01

A novel approach is presented for identifying disturbance sources in wall-bounded shear flows. The method can prove useful for active control of boundary layer transition from laminar to turbulent flow. The underlying idea is to consider the flow state, as measured in sensors, to be a mixture of sources, and to use Blind Source Separation (BSS) techniques to recover the separate sources and their unknown mixing process. We present a BSS method based on the Degenerate Unmixing Estimation Technique. This method can be used to identify any (a priori unknown) number of sources by using the data acquired by only two sensors. The power of the new method is demonstrated via numerical and experimental proofs of concept. Wind tunnel experiments involving boundary layer flow over a flat plate were carried out, in which two hot-wire anemometers were used to separate disturbances generated by disturbance generators such as a single dielectric barrier discharge plasma actuator and a loudspeaker.

An experimental investigation of vortex breakdown on a delta wing

NASA Technical Reports Server (NTRS)

Payne, F. M.; Nelson, R. C.

1986-01-01

An experimental investigation of vortex breakdown on delta wings at high angles is presented. Thin delta wings having sweep angles of 70, 75, 80 and 85 degrees are being studied. Smoke flow visualization and the laser light sheet technique are being used to obtain cross-sectional views of the leading edge vortices as they break down. At low tunnel speeds (as low as 3 m/s) details of the flow, which are usually imperceptible or blurred at higher speeds, can be clearly seen. A combination of lateral and longitudinal cross-sectional views provides information on the three dimensional nature of the vortex structure before, during and after breakdown. Whereas details of the flow are identified in still photographs, the dynamic characteristics of the breakdown process were recorded using high speed movies. Velocity measurements were obtained using a laser Doppler anemometer with the 70 degree delta wing at 30 degrees angle of attack. The measurements show that when breakdown occurs the core flow transforms from a jet-like flow to a wake-like flow.

Accurately measuring volcanic plume velocity with multiple UV spectrometers

USGS Publications Warehouse

Williams-Jones, Glyn; Horton, Keith A.; Elias, Tamar; Garbeil, Harold; Mouginis-Mark, Peter J; Sutton, A. Jeff; Harris, Andrew J. L.

2006-01-01

A fundamental problem with all ground-based remotely sensed measurements of volcanic gas flux is the difficulty in accurately measuring the velocity of the gas plume. Since a representative wind speed and direction are used as proxies for the actual plume velocity, there can be considerable uncertainty in reported gas flux values. Here we present a method that uses at least two time-synchronized simultaneously recording UV spectrometers (FLYSPECs) placed a known distance apart. By analyzing the time varying structure of SO2 concentration signals at each instrument, the plume velocity can accurately be determined. Experiments were conducted on Kīlauea (USA) and Masaya (Nicaragua) volcanoes in March and August 2003 at plume velocities between 1 and 10 m s−1. Concurrent ground-based anemometer measurements differed from FLYSPEC-measured plume speeds by up to 320%. This multi-spectrometer method allows for the accurate remote measurement of plume velocity and can therefore greatly improve the precision of volcanic or industrial gas flux measurements.

Effect of Turbulence in Wind-Tunnel Measurements

NASA Technical Reports Server (NTRS)

Dryden, H L; Kuethe, A M

1931-01-01

This paper gives some quantitative measurements of wind tunnel turbulence and its effect on the air resistance of spheres and airship models, measurements made possible by the hot wire anemometer and associated apparatus in its original form was described in Technical Report no. 320 and some modifications are presented in an appendix to the present paper. One important result of the investigation is a curve by means of which measurements of the air resistance of spheres can be interpreted to give the turbulence quantitatively. Another is the definite proof that the discrepancies in the results on the N. P. L. Standard airship models are due mainly to differences in the turbulences of the wind tunnels in which the tests were made. An attempt is made to interpret the observed results in terms of the boundary layer theory and for this purpose a brief account is given of the physical bases of this theory and of conceptions that have been obtained by analogy with the laws of flow in pipes.

Turbulence Measurements in a Tropical Zoo Hall

NASA Astrophysics Data System (ADS)

Eugster, Werner; Denzler, Basil; Bogdal, Christian

2017-04-01

The Masoala rainforest hall of the Zurich Zoo, Switzerland, covers a ground surface area of 10,856 m2 and reaches 30 m in height. With its transparent ETFE foiled roof it provides a tropical climate for a large diversity of plants and animals. In combination with an effort to estimate dry deposition of elemental mercury, we made an attempt to measure turbulent transfer velocity with an ultrasonic anemometer inside the hall. Not surprising, the largest turbulence elements were on the order of the hall dimension. Although the dimensions of the hall seem to be small (200,000 m3) for eddy covariance flux measurements and the air circulation inside the hall was extremely weak, the spectra of wind velocity components and virtual (sonic) temperature obeyed the general statistical description expected under unconstrained outdoor measurement conditions. We will present results from a two-week measurement campaign in the Masoala rainforest hall and make a suggestion for the deposition velocity to be used to estimate dry deposition of atmospheric components to the tropical vegetation surface.

KC-135 aero-optical turbulent boundary layer/shear layer experiment revisited

NASA Technical Reports Server (NTRS)

Craig, J.; Allen, C.

1987-01-01

The aero-optical effects associated with propagating a laser beam through both an aircraft turbulent boundary layer and artificially generated shear layers are examined. The data present comparisons from observed optical performance with those inferred from aerodynamic measurements of unsteady density and correlation lengths within the same random flow fields. Using optical instrumentation with tens of microsecond temporal resolution through a finite aperture, optical performance degradation was determined and contrasted with the infinite aperture time averaged aerodynamic measurement. In addition, the optical data were artificially clipped to compare to theoretical scaling calculations. Optical instrumentation consisted of a custom Q switched Nd:Yag double pulsed laser, and a holographic camera which recorded the random flow field in a double pass, double pulse mode. Aerodynamic parameters were measured using hot film anemometer probes and a five hole pressure probe. Each technique is described with its associated theoretical basis for comparison. The effects of finite aperture and spatial and temporal frequencies of the random flow are considered.

Transmission of Mycobacterium chimaera from Heater–Cooler Units during Cardiac Surgery despite an Ultraclean Air Ventilation System

PubMed Central

Sommerstein, Rami; Rüegg, Christian; Kohler, Philipp; Bloemberg, Guido; Kuster, Stefan P.

2016-01-01

Heater–cooler units (HCUs) were recently identified as a source of Mycobacterium chimaera causing surgical site infections. We investigated transmission of this bacterium from HCUs to the surgical field by using a thermic anemometer and particle counter, videotape of an operating room equipped with an ultraclean laminar airflow ventilation system, and bacterial culture sedimentation plates in a nonventilated room. Smoke from the HCU reached the surgical field in 23 s by merging with ultraclean air. The HCU produced on average 5.2, 139, and 14.8 particles/min in the surgical field at positions Off, On/oriented toward, and On/oriented away, respectively. Culture plates were positive for M. chimaera <5 m from the HCU in the test room. These experiments confirm airborne transmission of M. chimaera aerosols from a contaminated HCU to an open surgical field despite ultraclean air ventilation. Efforts to mitigate infectious risks during surgery should consider contamination from water sources and airflow-generating devices. PMID:27070958

Experimental studies of flow separation and stalling on two-dimensional airfoils at low speeds. Phase 2: Studies with Fowler flap extended

NASA Technical Reports Server (NTRS)

Seetharam, H. C.; Wentz, W. H., Jr.

1975-01-01

Results were given on experimental studies of flow separation and stalling on a two-dimensional GA(W)-1 17 percent thick airfoil with an extended Fowler flap. Experimental velocity profiles obtained from a five tube probe survey with optimum flap gap and overlap setting (flap at 40 deg) are shown at various stations above, below, and behind the airfoil/flap combination for various angles of attack. The typical zones of steady flow, intermittent turbulence, and large scale turbulence were obtained from a hot wire anemometer survey and are depicted graphically for an angle of attack of 12.5 deg. Local skin friction distributions were obtained and are given for various angles of attack. Computer plots of the boundary layer profiles are shown for the case of the flap at 40 deg. Static pressure contours are also given. A GA(W)-2 section model was fabricated with 30 percent Fowler flaps and with pressure tabs.

Measurement of atmospheric surface layer turbulence using unmanned aerial vehicles

NASA Astrophysics Data System (ADS)

Bailey, Sean; Canter, Caleb

2017-11-01

We describe measurements of the turbulence within the atmospheric surface layer using highly instrumented and autonomous unmanned aerial vehicles (UAVs). Results from the CLOUDMAP measurement campaign in Stillwater Oklahoma are presented including turbulence statistics measured during the transition from stably stratified to convective conditions. The measurements were made using pre-fabricated fixed-wing remote-control aircraft adapted to fly autonomously and carry multi-hole pressure probes, pressure, temperature and humidity sensors. Two aircraft were flown simultaneously, with one flying a flight path intended to profile the boundary layer up to 100 m and the other flying at a constant fixed altitude of 50 m. The evolution of various turbulent statistics was determined from these flights, including Reynolds stresses, correlations, spectra and structure functions. These results were compared to those measured by a sonic anemometer located on a 7.5 m tower. This work was supported by the National Science Foundation through Grant #CBET-1351411 and by National Science Foundation award #1539070, Collaboration Leading Operational UAS Development for Meteorology and Atmospheric Physics (CLOUDMAP).

Measurement of atmospheric surface layer turbulence using unmanned aerial vehicles

NASA Astrophysics Data System (ADS)

Witte, Brandon; Smith, Lorli; Schlagenhauf, Cornelia; Bailey, Sean

2016-11-01

We describe measurements of the turbulence within the atmospheric surface layer using highly instrumented and autonomous unmanned aerial vehicles (UAVs). Results from the CLOUDMAP measurement campaign in Stillwater Oklahoma are presented including turbulence statistics measured during the transition from stably stratified to convective conditions. The measurements were made using pre-fabricated fixed-wing remote-control aircraft adapted to fly autonomously and carry multi-hole pressure probes, pressure, temperature and humidity sensors. Two aircraft were flown simultaneously, with one flying a flight path intended to profile the boundary layer up to 100 m and the other flying at a constant fixed altitude of 50 m. The evolution of various turbulent statistics was determined from these flights, including Reynolds stresses, correlations, spectra and structure functions. These results were compared to those measured by a sonic anemometer located on a 7.5 m tower. This work was supported by the National Science Foundation through Grant #CBET-1351411 and by National Science Foundation award #1539070, Collaboration Leading Operational UAS Development for Meteorology and Atmospheric Physics (CLOUDMAP).

N2O eddy covariance fluxes: From field measurements to flux calculation

NASA Astrophysics Data System (ADS)

Lognoul, Margaux; Debacq, Alain; Heinesch, Bernard; Aubinet, Marc

2017-04-01

From March to October 2016, we performed eddy covariance measurements in a sugar beet crop at the Lonzée Terrestrial Observatory (LTO, candidate ICOS site) in Belgium. N2O and H2O atmospheric concentrations were measured at 10 Hz using a quantum-cascade laser spectrometer (Aerodyne Research, Inc.) and combined to wind speed 3D components measured with a sonic anemometer (Gill HS-50). Flux computation was carried out using the EddyPro Software (LI-COR) with a focus on adaptations needed for tracers like N2O. Data filtering and quality control were performed according to Vickers and Mahrt (1997) and Mauder and Foken (2004). The flags were adapted to N2O time series. In this presentation, different computation steps will be presented. More specifically: 1) Considering that a large proportion of N2O fluxes are small (within ± 0.5 nmol m-2 s-1), the classical stationarity test might lead to excessive data filtering and in such case, some searchers have chosen to use the running mean (RM) as a detrend method over block averaging (BA) and to filter data otherwise. For our dataset, BA mean fluxes combined to the stationarity test did not significantly differ from RM fluxes when the averaging window was 300s or larger, but were significantly larger otherwise, suggesting that significant eddies occurred at the 5-min timescale and that they were not accounted for with a shorter averaging window. 2) The determination of time-lag in the case of N2O fluxes can become tricky for two reasons : (1) the signal amplitude can differ from one time period to the next, making it difficult to use the method of covariance maximization and (2) an additional clock drift can appear if the spectrometer is not logging on the same computer than the anemometer. In our case, the N2O signal was strong enough to solve both problems and to perform time-lag compensation according to the covariance maximization, with a default value equal to the mode of the lag distribution. The automatic time-lag optimization suggested by EddyPro was not used as it gave inconsistent values for our dataset. 3) The effect of high frequency spectral correction was also investigated by comparing different in-situ methods to evaluate how using spectra or co-spectra - averaged or not - can affect results. Finally, a preliminary analysis of N2O fluxes dynamics will be presented.

A Grid of Fine Wire Thermocouples to Study the Spatial Coherence of Turbulence within Katabatic Flow through a Vineyard Canopy

NASA Astrophysics Data System (ADS)

Everard, K.; Christen, A.; Sturman, A.; Skaloud, P.

2016-12-01

Knowledge of the dynamics and thermodynamics of katabatic flow is relevant in vineyards, where grapevines are sensitive to temperature changes (frost protection and cooling). Basic understanding of the occurrence and evolution of, and turbulence within, katabatic flow is well known over bare slopes. However, little work has been completed to extend this understanding to mid-sized canopies and how the presence of a canopy affects the turbulent exchange of momentum and heat within the flow. Measurements were carried out over a 6° vineyard slope near Oliver, BC, Canada in the Okanagan Valley between July 5 and July 22, 2016. The set-up consisted of an array of five vertically arranged CSAT 3D (Campbell Scientific, Inc.) ultrasonic anemometers at z = 0.45 m, 0.90 m, 1.49 m, 2.34 m, and 4.73 m above ground level (AGL), and a 2-D grid of 40 Type-E (copper-constantan) fine-wire thermocouples (FWTC) arranged at the same heights as the CSAT 3D array on 8 masts extending in the upslope (flow) direction at locations x = 0.0 m (CSAT 3D tower), 0.5 m, 1.0 m, 2.0 m, 4.0 m, 8.0 m, 16.0 m, and 32.0 m. The FWTC array formed a sheet of 40 sampling points in the upslope-vertical plane. The height of the grapevine canopy (h) was approximately 2 m AGL, and rows were aligned along the local slope direction with a row spacing of 2.45 m. CSAT-3s were sampled at 60 Hz with 20 Hz data recording, the FWTCs were sampled at 2 Hz, all synchronized by a data logger. Katabatic flow was observed on several nights during the campaign, with a wind speed maximum located within the canopy. This contribution will focus on the measurement techniques, combining ultrasonic anemometer data with the spatially synchronized FWTC array using image process techniques. We identify the dynamics and structure of the katabatic flow, relevant for heat exchange, using the spatial coherence of the temperature field given by the FWTC array. Improved knowledge of the vertical structure and the dynamics of katabatic flow within canopies allows better understanding of how it influences mass transport and cold-air pooling within the immediate grapevine canopy. Such understanding allows for better vineyard planning and management, as well as parameterizing model approaches to assist in forecasting the effect of such events on the thermal environment.

Reattachment Zone Characterisation Under Offshore Winds With Flow Separation On The Lee Side Of Coastal Dunes

NASA Astrophysics Data System (ADS)

Delgado-Fernandez, I.; Jackson, D.; Cooper, J. A.; Baas, A. C.; Lynch, K.; Beyers, M.

2010-12-01

Airflow separation, lee-side eddies and secondary flows play an essential role on the formation and maintenance of sand dunes. Downstream from dune crests the flow surface layer detaches from the ground and generates an area characterised by turbulent eddies in the dune lee slope (the wake). At some distance downstream from the dune crest, flow separates into a reversed component directed toward the dune toe and an offshore “re-attached” component. This reattachment zone (RZ) has been documented in fluvial and desert environments, wind tunnel experiments and numerical simulations, but not yet characterised in coastal dunes. This study examines the extent and temporal evolution of the RZ and its implications for beach-dune interaction at Magilligan, Northern Ireland. Wind parameters were measured over a profile extending from an 11 m height dune crest towards the beach, covering a total distance of 65 m cross-shore. Data was collected using an array of nine ultrasonic anemometers (UAs) deployed in April-May 2010, as part of a larger experiment to capture airflow data under a range of incident wind velocities and offshore directions. UAs were located along the profile (5 m tower spacing) over the beach, which allowed a detailed examination of the RZ with empirical data. Numerical modelling using Computational Fluid Dynamics (CFD) software was also conducted with input data from anemometer field measurements, running over a surface mesh generated from LiDAR and DGPS surveys. Results demonstrate that there is a wind threshold of approximately 5-6 ms-1 under which no flow separation exists with offshore winds. As wind speed increases over the threshold, a flow reversal area is quickly formed, with the maximum extent of the RZ at approximately 3.5 dune heights (h). The maximum extent of the RZ increases up to 4.5h with stronger wind speeds of 8-10 ms-1 and remains relatively constant as wind speed further increases. This suggests that the spatial extent of the RZ is independent of incident wind speed and is located between 4-5h. The magnitude of the maximum extent of the RZ is similar to that simulated using CFD and is consistent with previous studies conducted in desert dunes and wind tunnel simulations for offshore winds blowing over tall and sharp-crested dunes. Ongoing analyses are being conducted to evaluate the effect of changing wind direction, dune height and shape.

Machine learning algorithms for meteorological event classification in the coastal area using in-situ data

NASA Astrophysics Data System (ADS)

Sokolov, Anton; Gengembre, Cyril; Dmitriev, Egor; Delbarre, Hervé

2017-04-01

The problem is considered of classification of local atmospheric meteorological events in the coastal area such as sea breezes, fogs and storms. The in-situ meteorological data as wind speed and direction, temperature, humidity and turbulence are used as predictors. Local atmospheric events of 2013-2014 were analysed manually to train classification algorithms in the coastal area of English Channel in Dunkirk (France). Then, ultrasonic anemometer data and LIDAR wind profiler data were used as predictors. A few algorithms were applied to determine meteorological events by local data such as a decision tree, the nearest neighbour classifier, a support vector machine. The comparison of classification algorithms was carried out, the most important predictors for each event type were determined. It was shown that in more than 80 percent of the cases machine learning algorithms detect the meteorological class correctly. We expect that this methodology could be applied also to classify events by climatological in-situ data or by modelling data. It allows estimating frequencies of each event in perspective of climate change.

First results of eclipse induced pressure and turbulence changes in South Carolina

NASA Astrophysics Data System (ADS)

Hiscox, A.; McCombs, A. G.; Stewart, M. J.

2017-12-01

Total solar eclipses supply both visual captivation and a controlled meteorological experiment by reason of a sudden decrease in radiation from the Sun. This presentation will provide first results from a field experiment focused on the atmospheric surface layer changes before, during, and after a total solar eclipse. A suite of instruments including radiosondes, aerosol lidar, sonic anemometers, and microbarographs will be deployed one mile from the total eclipse centerline outside Columbia, South Carolina. The results should not only confirm the commonly expected changes in sensible weather, but also provide insight into the generation and propagation of internal gravity waves. These waves propagate and transfer both energy and momentum vertically to and from the upper levels of the atmosphere. Early scientific results are expected to provide IGW vertical propagation speeds from succesive radiosonde measurements, while triangulated surface pressure measurements will provide timing of wave activity. Other anticipated results to be presented are changes in turbulence turbulence stationarity and pressure pertubations. Finally, the sucess of a major outreach event held in tandem with the scientific experiement will be discussed.

Compensated intruder-detection systems

DOEpatents

McNeilly, David R.; Miller, William R.

1984-01-01

Intruder-detection systems in which intruder-induced signals are transmitted through a medium also receive spurious signals induced by changes in a climatic condition affecting the medium. To combat this, signals received from the detection medium are converted to a first signal. The system also provides a reference signal proportional to climate-induced changes in the medium. The first signal and the reference signal are combined for generating therefrom an output signal which is insensitive to the climatic changes in the medium. An alarm is energized if the output signal exceeds a preselected value. In one embodiment, an acoustic cable is coupled to a fence to generate a first electrical signal proportional to movements thereof. False alarms resulting from wind-induced movements of the fence (detection medium) are eliminated by providing an anemometer-driven voltage generator to provide a reference voltage proportional to the velocity of wind incident on the fence. An analog divider receives the first electrical signal and the reference signal as its numerator and denominator inputs, respectively, and generates therefrom an output signal which is insensitive to the wind-induced movements in the fence.

Experimental and computational investigation of the tip clearance flow in a transonic axial compressor rotor

NASA Astrophysics Data System (ADS)

Suder, Kenneth L.; Celestina, Mark L.

1995-06-01

Experimental and computational techniques are used to investigate tip clearance flows in a transonic axial compressor rotor at design and part speed conditions. Laser anemometer data acquired in the endwall region are presented for operating conditions near peak efficiency and near stall at 100% design speed and at near peak efficiency at 60% design speed. The role of the passage shock/leakage vortex interaction in generating endwall blockage is discussed. As a result of the shock/vortex interaction at design speed, the radial influence of the tip clearance flow extends to 20 times the physical tip clearance height. At part speed, in the absence of the shock, the radial extent is only 5 times the tip clearance height. Both measurements and analysis indicate that under part-speed operating conditions a second vortex, which does not originate from the tip leakage flow, forms in the endwall region within the blade passage and exits the passage near midpitch. Mixing of the leakage vortex with primary flow downstream of the rotor at both design and part speed conditions is also discussed.

LIST/BMI Turbines Instrumentation and Infrastructure

DOE Office of Scientific and Technical Information (OSTI.GOV)

JONES,PERRY L.; SUTHERLAND,HERBERT J.; NEAL,BYRON A.

2001-06-01

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 structuralmore » 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.« less

Measurement of vortex flow fields

NASA Technical Reports Server (NTRS)

Mcdevitt, T. Kevin; Ambur, Todd A.; Orngard, Gary M.; Owen, F. Kevin

1992-01-01

A 3-D laser fluorescence anemometer (LFA) was designed, built, and demonstrated for use in the Langley 16 x 24 inch Water Tunnel. Innovative optical design flexibility combined with compact and portable data acquisition and control systems were incorporated into the instrument. This will allow its use by NASA in other test facilities. A versatile fiber optic system facilities normal and off-axis laser beam alignment, removes mirror losses and improves laser safety. This added optical flexibility will also enable simple adaptation for use in the adjacent jet facility. New proprietary concepts in transmitting color separation, light collection, and novel prism separation of the scattered light was also designed and built into the system. Off-axis beam traverse and alignment complexity led to the requirement for a specialized, programmable transverse controller, and the inclusion of an additional traverse for the off-axis arm. To meet this challenge, an 'in-house' prototype unit was designed and built and traverse control software developed specifically for the water tunnel traverse applications. A specialized data acquisition interface was also required. This was designed and built for the LFA system.

Investigation of scaling characteristics for defining design environments due to transient ground winds and near-field, nonlinear acoustic fields

NASA Technical Reports Server (NTRS)

Shih, C. C.

1973-01-01

In order to establish a foundation of scaling laws for the highly nonlinear waves associated with the launch vehicle, the basic knowledge of the relationships among the paramaters pertinent to the energy dissipation process associated with the propagation of nonlinear pressure waves in thermoviscous media is required. The problem of interest is to experimentally investigate the temporal and spacial velocity profiles of fluid flow in a 3-inch open-end pipe of various lengths, produced by the propagation of nonlinear pressure waves for various diaphragm burst pressures of a pressure wave generator. As a result, temporal and spacial characteristics of wave propagation for a parametric set of nonlinear pressure waves in the pipe containing air under atmospheric conditions were determined. Velocity measurements at five sections along the pipes of up to 210 ft. in length were made with hot-film anemometers for five pressure waves produced by a piston. The piston was derived with diaphragm burst pressures at 20, 40, 60, 80 and 100 psi in the driver chamber of the pressure wave generator.

RSA/Legacy Wind Sensor Comparison. Part 2; Eastern Range

NASA Technical Reports Server (NTRS)

Short, David A.; Wheeler, Mark M.

2006-01-01

This report describes a comparison of data from ultrasonic and propeller-and-vane anemometers on 5 wind towers at Kennedy Space Center and Cape Canaveral Air Force Station. The ultrasonic sensors are scheduled to replace the Legacy propeller-and-vane sensors under the Range Standardization and Automation (RSA) program. Because previous studies have noted differences between peak wind speeds reported by mechanical and ultrasonic wind sensors, the latter having no moving parts, the 30th and 45th Weather Squadrons wanted to understand possible differences between the two sensor types. The period-of-record was 13-30 May 2005, A total of 357,626 readings of 1-minute average and peak wind speed/direction from each sensor type were used. Statistics of differences in speed and direction were used to identify 15 out of 19 RSA sensors having the most consistent performance, with respect to the Legacy sensors. RSA average wind speed data from these 15 showed a small positive bias of 0.38 kts. A slightly larger positive bias of 0.94 kts was found in the RSA peak wind speed.

Zero pressure gradient boundary layer at extreme Reynolds numbers

NASA Astrophysics Data System (ADS)

Hultmark, Marcus; Vallikivi, Margit; Smits, Alexander

2011-11-01

Experiments were conducted in a zero pressure gradient flat plate boundary layer using the Princeton/ONR High Reynolds number Test Facility (HRTF). The HRTF uses highly compressed air, up to 220 atmospheres, to produce Reynolds numbers up to Reθ =225,000 . This corresponds to a δ+ =65,000 which is one of the highest Reynolds numbers ever measured in a laboratory. When using pressure to achieve high Reynolds numbers the size of the measurement probes become critical, thus the need for very small sensors is acute. The streamwise component of velocity was investigated using a nanoscale thermal anemometer (NSTAP) as well as a 200 μm pitot tube. The NSTAP has a spatial resolution as well as a temporal resolution one order of magnitude better than conventional measurement techniques. The data was compared to recent data from a high Reynolds number turbulent pipe flow and it was shown that the two flows are more similar than previous data suggests. Supported under NR Grant N00014-09-1-0263 (program manager Ron Joslin) and NSF Grant CBET-1064257(program manager Henning Winter).

Unsteady Flows in a Single-Stage Transonic Axial-Flow Fan Stator Row. Ph.D. Thesis - Iowa State Univ.

NASA Technical Reports Server (NTRS)

Hathaway, Michael D.

1986-01-01

Measurements of the unsteady velocity field within the stator row of a transonic axial-flow fan were acquired using a laser anemometer. Measurements were obtained on axisymmetric surfaces located at 10 and 50 percent span from the shroud, with the fan operating at maximum efficiency at design speed. The ensemble-average and variance of the measured velocities are used to identify rotor-wake-generated (deterministic) unsteadiness and turbulence, respectively. Correlations of both deterministic and turbulent velocity fluctuations provide information on the characteristics of unsteady interactions within the stator row. These correlations are derived from the Navier-Stokes equation in a manner similar to deriving the Reynolds stress terms, whereby various averaging operators are used to average the aperiodic, deterministic, and turbulent velocity fluctuations which are known to be present in multistage turbomachines. The correlations of deterministic and turbulent velocity fluctuations throughout the axial fan stator row are presented. In particular, amplification and attenuation of both types of unsteadiness are shown to occur within the stator blade passage.

Numerical and Experimental Study of Wake Redirection Techniques in a Boundary Layer Wind Tunnel

NASA Astrophysics Data System (ADS)

Wang, J.; Foley, S.; Nanos, E. M.; Yu, T.; Campagnolo, F.; Bottasso, C. L.; Zanotti, A.; Croce, A.

2017-05-01

The aim of the present paper is to validate a wind farm LES framework in the context of two distinct wake redirection techniques: yaw misalignment and individual cyclic pitch control. A test campaign was conducted using scaled wind turbine models in a boundary layer wind tunnel, where both particle image velocimetry and hot-wire thermo anemometers were used to obtain high quality measurements of the downstream flow. A LiDAR system was also employed to determine the non-uniformity of the inflow velocity field. A high-fidelity large-eddy simulation lifting-line model was used to simulate the aerodynamic behavior of the system, including the geometry of the wind turbine nacelle and tower. A tuning-free Lagrangian scale-dependent dynamic approach was adopted to improve the sub-grid scale modeling. Comparisons with experimental measurements are used to systematically validate the simulations. The LES results are in good agreement with the PIV and hot-wire data in terms of time-averaged wake profiles, turbulence intensity and Reynolds shear stresses. Discrepancies are also highlighted, to guide future improvements.

Direct Growth of Graphene Films on 3D Grating Structural Quartz Substrates for High-Performance Pressure-Sensitive Sensors.

PubMed

Song, Xuefen; Sun, Tai; Yang, Jun; Yu, Leyong; Wei, Dacheng; Fang, Liang; Lu, Bin; Du, Chunlei; Wei, Dapeng

2016-07-06

Conformal graphene films have directly been synthesized on the surface of grating microstructured quartz substrates by a simple chemical vapor deposition process. The wonderful conformality and relatively high quality of the as-prepared graphene on the three-dimensional substrate have been verified by scanning electron microscopy and Raman spectra. This conformal graphene film possesses excellent electrical and optical properties with a sheet resistance of <2000 Ω·sq(-1) and a transmittance of >80% (at 550 nm), which can be attached with a flat graphene film on a poly(dimethylsiloxane) substrate, and then could work as a pressure-sensitive sensor. This device possesses a high-pressure sensitivity of -6.524 kPa(-1) in a low-pressure range of 0-200 Pa. Meanwhile, this pressure-sensitive sensor exhibits super-reliability (≥5000 cycles) and an ultrafast response time (≤4 ms). Owing to these features, this pressure-sensitive sensor based on 3D conformal graphene is adequately introduced to test wind pressure, expressing higher accuracy and a lower background noise level than a market anemometer.

The effect of small angle of attack on the laminar-turbulent transition in boundary layer on swept wing at Mach number M=2

NASA Astrophysics Data System (ADS)

Semionov, N. V.; Yermolaev, Yu. G.; Kosinov, A. D.; Semenov, A. N.; Smorodsky, B. V.; Yatskikh, A. A.

2017-10-01

The paper is devoted to an experimental and theoretical study of effect of small angle of attack on disturbances evolution and laminar-turbulent transition in a supersonic boundary layer on swept wing at Mach number M=2. The experiments are conducted at the low nose supersonic wind tunnel T-325 of ITAM. Model is a symmetrical wing with a 45° sweep angle, a 3 percent-thick circular-arc airfoil. The transition location is determined using a hot-wire anemometer. Confirmed monotonous growth of the transition Reynolds numbers with increasing of angle of attack from -2° to 2.5°. The experimental data on the influence of the angle of attack on the disturbances evolution in the supersonic boundary layer on the swept wing model are obtained. Calculations on the effect of small angles of attack on the development of perturbations are made in the framework of the linear theory of stability. A good qualitative correspondence of theoretical and experimental data are obtained.

Effect of Climate Extremes, Seasonal Change, and Agronomic Practices on Measured Evapotranspiration and CO2 Exchange in Sacramento-San Joaquin River Delta Alfalfa Fields

NASA Astrophysics Data System (ADS)

Clay, J.; Kent, E. R.; Leinfelder-Miles, M.; Paw U, K. T.; Little, C.; Lambert, J. J.

2017-12-01

Evapotranspiration and CO2 exchange was measured in five alfalfa fields in the Sacramento-San Joaquin River Delta region from 2016 to 2017 using eddy covariance and surface renewal methods. Seasonal changes of evapotranspiration and CO2 fluxes were compared between 2016, a drought year, and 2017, a high rainfall year. Additionally, changes in evapotranspiration and CO2 flux were investigated across various agronomic considerations, such as irrigation methods (border-check flood and sub-surface), stand life, and herbicide programs. Components of the energy balance, including net radiation, latent heat, ground heat flux, and sensible heat, were evaluated considering correlations to wind speed measured by three sonic anemometers, irrigation frequency, and crop cutting cycle. Comparisons between two different types of radiometers were also carried out. Under drought conditions, we observed higher amounts of evapotranspiration in a field having a stand life of less than two years of age compared to older stands, and in a sub-surface irrigated field compared to flood irrigated fields.

GADEN: A 3D Gas Dispersion Simulator for Mobile Robot Olfaction in Realistic Environments.

PubMed

Monroy, Javier; Hernandez-Bennets, Victor; Fan, Han; Lilienthal, Achim; Gonzalez-Jimenez, Javier

2017-06-23

This work presents a simulation framework developed under the widely used Robot Operating System (ROS) to enable the validation of robotics systems and gas sensing algorithms under realistic environments. The framework is rooted in the principles of computational fluid dynamics and filament dispersion theory, modeling wind flow and gas dispersion in 3D real-world scenarios (i.e., accounting for walls, furniture, etc.). Moreover, it integrates the simulation of different environmental sensors, such as metal oxide gas sensors, photo ionization detectors, or anemometers. We illustrate the potential and applicability of the proposed tool by presenting a simulation case in a complex and realistic office-like environment where gas leaks of different chemicals occur simultaneously. Furthermore, we accomplish quantitative and qualitative validation by comparing our simulated results against real-world data recorded inside a wind tunnel where methane was released under different wind flow profiles. Based on these results, we conclude that our simulation framework can provide a good approximation to real world measurements when advective airflows are present in the environment.

Assessment of virtual towers performed with scanning wind lidars and Ka-band radars during the XPIA experiment

DOE PAGES

Debnath, Mithu; Iungo, Giacomo Valerio; Brewer, W. Alan; ...

2017-03-29

During the eXperimental Planetary boundary layer Instrumentation Assessment (XPIA) campaign, which was carried out at the Boulder Atmospheric Observatory (BAO) in spring 2015, multiple-Doppler scanning strategies were carried out with scanning wind lidars and Ka-band radars. Specifically, step–stare measurements were collected simultaneously with three scanning Doppler lidars, while two scanning Ka-band radars carried out simultaneous range height indicator (RHI) scans. The XPIA experiment provided the unique opportunity to compare directly virtual-tower measurements performed simultaneously with Ka-band radars and Doppler wind lidars. Furthermore, multiple-Doppler measurements were assessed against sonic anemometer data acquired from the meteorological tower (met-tower) present at the BAOmore » site and a lidar wind profiler. As a result, this survey shows that – despite the different technologies, measurement volumes and sampling periods used for the lidar and radar measurements – a very good accuracy is achieved for both remote-sensing techniques for probing horizontal wind speed and wind direction with the virtual-tower scanning technique.« less

Experimental and Computational Investigation of the Tip Clearance Flow in a Transonic Axial Compressor Rotor

NASA Technical Reports Server (NTRS)

Suder, Kenneth L.; Celestina, Mark L.

1995-01-01

Experimental and computational techniques are used to investigate tip clearance flows in a transonic axial compressor rotor at design and part speed conditions. Laser anemometer data acquired in the endwall region are presented for operating conditions near peak efficiency and near stall at 100% design speed and at near peak efficiency at 60% design speed. The role of the passage shock/leakage vortex interaction in generating endwall blockage is discussed. As a result of the shock/vortex interaction at design speed, the radial influence of the tip clearance flow extends to 20 times the physical tip clearance height. At part speed, in the absence of the shock, the radial extent is only 5 times the tip clearance height. Both measurements and analysis indicate that under part-speed operating conditions a second vortex, which does not originate from the tip leakage flow, forms in the endwall region within the blade passage and exits the passage near midpitch. Mixing of the leakage vortex with primary flow downstream of the rotor at both design and part speed conditions is also discussed.

GADEN: A 3D Gas Dispersion Simulator for Mobile Robot Olfaction in Realistic Environments

PubMed Central

Hernandez-Bennetts, Victor; Fan, Han; Lilienthal, Achim; Gonzalez-Jimenez, Javier

2017-01-01

This work presents a simulation framework developed under the widely used Robot Operating System (ROS) to enable the validation of robotics systems and gas sensing algorithms under realistic environments. The framework is rooted in the principles of computational fluid dynamics and filament dispersion theory, modeling wind flow and gas dispersion in 3D real-world scenarios (i.e., accounting for walls, furniture, etc.). Moreover, it integrates the simulation of different environmental sensors, such as metal oxide gas sensors, photo ionization detectors, or anemometers. We illustrate the potential and applicability of the proposed tool by presenting a simulation case in a complex and realistic office-like environment where gas leaks of different chemicals occur simultaneously. Furthermore, we accomplish quantitative and qualitative validation by comparing our simulated results against real-world data recorded inside a wind tunnel where methane was released under different wind flow profiles. Based on these results, we conclude that our simulation framework can provide a good approximation to real world measurements when advective airflows are present in the environment. PMID:28644375

Editorial special issue on "Laser Doppler vibrometry"

NASA Astrophysics Data System (ADS)

Vanlanduit, Steve; Dirckx, Joris

2017-12-01

The invention of the laser in 1960 has opened up many opportunities in the field of measurement science and technology. Just a few years after the invention of the laser, a novel fluid flow measurement technique based on the Doppler effect was introduced: at that moment the laser Doppler anemometer or shortly LDA [1] was born. The technique enabled fluid velocity measurement by using the light of a He-Ne beam which was scattered by very small polystyrene spheres entrained in the fluid. Later on, in the late nineteen seventees it was recognized that the detection of the Doppler frequency shift that occurs when light is scattered by a moving surface can also be used to measure the vibration velocity of an object. The instrument to perform these vibration measurements was called the laser Doppler vibrometer or LDV [2]. In the last decades several technological advances were made in the field of laser Doppler vibrometry. The result is that nowadays, velocity measurements of fluids (using LDA) and vibrating objects (using LDV) are performed in many challenging applications in different fields (microelectronics, civil structures, biomedical engineering, material science, etc.).

Flow-field Survey of an Empennage Wake Interacting with a Pusher Propeller

NASA Technical Reports Server (NTRS)

Horne, W. Clifton; Soderman, Paul T.

1988-01-01

The flow field between a model empennage and a 591-mm-diameter pusher propeller was studied in the Ames 7- by 10-Foot Wind Tunnel with directional pressure probes and hot-wire anemometers. The region probed was bounded by the empennage trailing edge and downstream propeller. The wake properties, including effects of propeller operation on the empennage wake, were investigated for two empennage geometries: one, a vertical tail fin, the other, a Y-tail with a 34 deg dihedral. Results showed that the effect of the propeller on the empennage wake upstream of the propeller was not strong. The flow upstream of the propeller was accelerated in the streamwise direction by the propeller, but the empennage wake width and velocity defect were relatively unaffected by the presence of the propeller. The peak turbulence in the wake near the propeller tip station, 0.66 diameter behind the vertical tail fin, was approximately 3 percent of the free-stream velocity. The velocity field data can be used in predictions of the acoustic field due to propeller-wake interaction.

Flight Demonstration of a Shock Location Sensor Using Constant Voltage Hot-Film Anemometry

NASA Technical Reports Server (NTRS)

Moes, Timothy R.; Sarma, Garimella R.; Mangalam, Siva M.

1997-01-01

Flight tests have demonstrated the effectiveness of an array of hot-film sensors using constant voltage anemometry to determine shock position on a wing or aircraft surface at transonic speeds. Flights were conducted at the NASA Dryden Flight Research Center using the F-15B aircraft and Flight Test Fixture (FTF). A modified NACA 0021 airfoil was attached to the side of the FTF, and its upper surface was instrumented to correlate shock position with pressure and hot-film sensors. In the vicinity of the shock-induced pressure rise, test results consistently showed the presence of a minimum voltage in the hot-film anemometer outputs. Comparing these results with previous investigations indicate that hot-film anemometry can identify the location of the shock-induced boundary layer separation. The flow separation occurred slightly forward of the shock- induced pressure rise for a laminar boundary layer and slightly aft of the start of the pressure rise when the boundary layer was tripped near the airfoil leading edge. Both minimum mean output and phase reversal analyses were used to identify the shock location.