1、Designation: D 5527 00 (Reapproved 2002)e1Standard Practices forMeasuring Surface Wind and Temperature by AcousticMeans1This standard is issued under the fixed designation D 5527; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、 year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEMade editorial corrections to the table in 3.3 and to Equation 8 in October 2002.1. Scope1.1 This practice covers
3、procedures for measuring one-,two-, or three-dimensional vector wind components and sonictemperature by means of commercially available sonicanemometer/thermometers that employ the inverse time mea-surement technique. This practice applies to the measurementof wind velocity components over horizonta
4、l terrain usinginstruments mounted on stationary towers. This practice alsoapplies to speed of sound measurements that are converted tosonic temperatures but does not apply to the measurement oftemperature by the use of ancillary temperature devices.1.2 The values stated in SI units are to be regard
5、ed as thestandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to u
6、se.2. Referenced Documents2.1 ASTM Standards:2D 1356 Standard Terminology Relating to Sampling andAnalysis of AtmospheresD 3631 Test Methods for Measuring Surface AtmosphericPressureD 4230 Test Method of Measuring Humidity with Cooled-Surface Condensation (Dew-Point) HygrometerE 337 Test Method for
7、Measuring Humidity with a Psy-chrometer (the Measurement of Wet- and Dry-Bulb Tem-peratures)E 380 Practice for Use of the International System of Units(SI) (the Modernized Metric System)3. Terminology3.1 DefinitionsRefer to Terminology D 1356 for commonterminology.3.2 Definitions of Terms Specific t
8、o This Standard:3.2.1 acceptance angle (6a, deg) the angular distance,centered on the array axis of symmetry, over which thefollowing conditions are met: (a) wind components are unam-biguously defined, and (b) flow across the transducers isunobstructed or remains within the angular range for whichtr
9、ansducer shadow corrections are defined.3.2.2 acoustic pathlength (d, (m)the distance betweentransducer transmitter-receiver pairs.3.2.3 sampling period(s)the record length or time intervalover which data collection occurs.3.2.4 sampling rate (Hz)the rate at which data collectionoccurs, usually pres
10、ented in samples per second or Hertz.3.2.5 sonic anemometer/thermometeran instrument con-sisting of a transducer array containing paired sets of acoustictransmitters and receivers, a system clock, and microprocessorcircuitry to measure intervals of time between transmission andreception of sound pul
11、ses.3.2.5.1 DiscussionThe fundamental measurement unit istransit time. With transit time and a known acoustic pathlength,velocity or speed of sound, or both, can be calculated.Instrument output is a series of quasi-instantaneous velocitycomponent readings along each axis or speed of sound, or both.T
12、he speed of sound and velocity components may be used tocompute sonic temperature (Ts), to describe the mean windfield, or to compute fluxes, variances, and turbulence intensi-ties.3.2.6 sonic temperature (Ts), (K) an equivalent tempera-ture that accounts for the effects of temperature and moistureo
13、n acoustic wavefront propagation through the atmosphere.3.2.6.1 DiscussionSonic temperature is related to thevelocity of sound c, absolute temperature T, vapor pressure ofwater e, and absolute pressure P by (1).3c25 403T 1 1 0.32e/P! 5 403Ts(1)1This practice is under the jurisdiction of ASTM Committ
14、ee D22 on Samplingand Analysis of Atmospheres and is the direct responsibility of SubcommitteeD22.11 on Meteorology.Current edition approved September 10, 2000. Published November 2000.Originally published as D 5527 94. Last previous edition D 5527 94.2For referenced ASTM standards, visit the ASTM w
15、ebsite, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The boldface numbers in parentheses refer to the list of references at the end ofthis practice.1Copyright AS
16、TM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.(Guidance concerning measurement of P and e are containedin Test Methods D 3631, D 4230, and E 337.)3.2.7 transducer shadow correctionthe ratio of the truealong-axis velocity, as measured in a wind
17、tunnel or by anotheraccepted method, to the instrument along-axis wind measure-ment.3.2.7.1 DiscussionThis ratio is used to compensate foreffects of along-axis flow shadowing by the transducers andtheir supporting structure.3.2.8 transit time (t, (s)the time required for an acousticwavefront to trav
18、el from the transducer of origin to thereceiving transducer.3.3 Symbols:B (dimensionless) squared sums of sines and cosines of wind directionangle used to calculate wind direction standard devia-tionc (m/s) speed of soundd (m) acoustic pathlengthe (Pa) vapor pressure of waterf (dimensionless) compre
19、ssibility factorP (Pa) ambient pressuret (s) transit timeT (K) absolute temperature, KTs(K) sonic temperature, Kg (dimensionless) specific heat ratio (cp/cv)M (g/mol) molar mass of airn (dimensionless) sample sizeR* (J/molK) the universal gas constantu (m/s) velocity component along the determined m
20、ean wind di-rectionus(m/s) velocity component along the array u axisv (m/s) velocity component crosswind to the determined meanwind directionvs(m/s) velocity component along the array v axisw (m/s) vertical velocityWS (m/s) scalar wind speed computed from measured velocitycomponents in the horizonta
21、l planeu (deg) determined mean wind direction with respect to truenorthur(deg) wind direction measured in degrees clockwise from thesonic anemometer + vsaxis to the along-wind u axisa (deg) acceptance anglef (deg) orientation of the sonic anemometer axis with respect tothe true northsu(deg) standard
22、 deviation of wind azimuth angle3.4 Abbreviations:UnitsUnits of measurement usedshould be in accordance with Practice E 380.44. Summary of Practice4.1 Acalibrated sonic anemometer/thermometer is installed,leveled, and oriented into the expected wind direction to ensurethat the measured along-axis ve
23、locity components fall withinthe instruments acceptance angle.4.2 The wind components measured over a user-definedsampling period are averaged and subjected to a softwarerotation into the mean wind. This rotation maximizes the meanalong-axis wind component and reduces the mean cross-component v to z
24、ero.4.3 Mean horizontal wind speed and direction are computedfrom the rotated wind components.4.4 For the sonic thermometer, the speed of sound solutionis obtained and converted to a sonic temperature.4.5 Variances, covariances, and turbulence intensities arecomputed.5. Significance and Use5.1 Sonic
25、 anemometer/thermometers are used to measureturbulent components of the atmosphere except for confinedareas and very close to the ground. This practice applies to theuse of these instruments for field measurement of the wind,sonic temperature, and atmospheric turbulence components.The quasi-instanta
26、neous velocity component measurements areaveraged over user-selected sampling times to define meanalong-axis wind components, mean wind speed and direction,and the variances or covariances, or both, of individualcomponents or component combinations. Covariances are usedfor eddy correlation studies a
27、nd for computation of boundarylayer heat and momentum fluxes. The sonic anemometer/thermometer provides the data required to characterize the stateof the turbulent atmospheric boundary layer.5.2 The sonic anemometer/thermometer array shall have asufficiently high structural rigidity and a sufficient
28、ly lowcoefficient of thermal expansion to maintain an internal align-ment to within 60.1. System electronics must remain stableover its operating temperature range; the time counter oscilla-tor instability must not exceed 0.01 % of frequency. Consultwith the manufacturer for an internal alignment ve
29、rificationprocedure.5.3 The calculations and transformations provided in thispractice apply to orthogonal arrays. References are also pro-vided for common types of non-orthogonal arrays.6. Interferences6.1 Mount the sonic anemometer probe for an acceptanceangle into the mean wind. Wind velocity comp
30、onents fromangles outside the acceptance angle may be subject to uncom-pensated flow blockage effects from the transducers andsupporting structure, or may not be unambiguously defined.Obtain acceptance angle information from the manufacturer.6.2 Mount the sonic array at a distance that exceeds theac
31、oustic pathlength by a factor of at least 2p from anyreflecting surface.6.3 To obtain representative samples of the mean wind, thesonic array must be exposed at a representative site. Sonicanemometer/thermometers are typically mounted over level,open terrain at a height of 10 m above the ground. Con
32、sidersurface roughness and obstacles that might cause flow block-age or biases in the site selection process.6.4 Carefully measure and verify array tilt angle and align-ment. The vertical component of the wind is usually muchsmaller than the horizontal components. Therefore, the verticalwind compone
33、nt is highly susceptible to cross-componentcontamination from tilt angles not aligned to the chosencoordinate system. A typical coordinate system may includeestablishing a level with reference to either the earth or to localterrain slope. Momentum flux computations are particularlysusceptible to off
34、-axis contamination (2). Calculations andtransformations (Section 9) for sonic anemometer data arebased on the assumption that the mean vertical velocity ( w )isnot significantly different from zero. Arrays mounted above asloping surface may require tilt angle adjustments. Also, avoidmounting the ar
35、ray close (within 2 m) to the ground surfacewhere velocity gradients are large and w may be nonzero.4Excerpts from Practice E 380 are included in Vol 11.03.D 5527 00 (2002)e126.5 The transducers are tiny microphones and are, therefore,sensitive to extraneous noise sources, especially ultrasonicsourc
36、es at the anemometers operating frequency. Mount thetransducer array in an environment free of extraneous noisesources.6.6 Sonic anemometer/thermometer transducer arrays con-tribute a certain degree of blockage to flow. Consequently, themanufacturer should include transducer shadow corrections aspar
37、t of the instruments data processing algorithms, or definean acceptance angle beyond which valid measurements cannotbe made, or both.6.7 Ensure that the instrument is operated within its velocitycalibration range and at temperatures where thermal sensitivityeffects are not observed.6.8 This practice
38、 does not address applications where mois-ture is likely to accumulate on the transducers. Moistureaccumulation may interrupt transmission of the acoustic signal,or possibly damage unsealed transducers. Consult the manu-facturer concerning operation in adverse environments.7. Sampling7.1 The basic s
39、ampling rate of a sonic anemometer is on theorder of several hundred hertz. Transit times are averagedwithin the instruments software to produce basic measure-ments at a rate of 10 to 20 Hz, which may be user-selectable.This sampling is done to improve instrument measurementprecision and to suppress
40、 high frequency noise and aliasingeffects. The 10 to 20-Hz sample output in a serial digital datastream or through a digital to analog converter is the basic unitof measurement for a sonic anemometer.7.2 Select a sampling period of sufficient duration to obtainstatistically stable measurements of th
41、e phenomena of interest.Sampling periods of at least 10 min duration usually generatesufficient data to describe the turbulent state of the atmosphereduring steady wind conditions. Sampling periods in excess of1 h may contain undesired trends in wind direction.8. Procedure8.1 Perform system calibrat
42、ion in a zero wind chamber(refer to the manufacturers instructions).8.2 Mount the instrument array on a solid, vibration-freeplatform free of interferences.8.3 Select an orientation into the mean flow within theinstruments acceptance angle. Record the orientation anglewith a resolution of 1. Use a l
43、eveling device to position theprobe to within 60.1 of the vertical axis of the chosencoordinate system.NOTE 1Caution: Wind measurements using a sonic anemometershould only be made within the acceptance angle.8.4 Install cabling to the recording device, and keep cablingisolated from other electronics
44、 noise sources or power cables tominimize induction or crosstalk.8.5 As a system check, collect data for several sequentialsampling periods (of at least 10-min duration over a period ofat least 1 h) during representative operating conditions. Exam-ine data samples for extraneous spikes, noise, align
45、ment faults,or other malfunctions. Construct summary statistics for eachsampling period to include means, variances, and covariances;examine these statistics for reasonableness. Compute 1-hspectra and examine for spikes or aliasing affecting the 5/3spectral slope in the inertial subrange.NOTE 2Calcu
46、lations and transformations presented in this practiceare based on the assumption of a zero mean vertical velocity component.Deviation of the mean vertical velocity component from zero should notexceed the desired measurement precision. Alignment or data reductionsoftware modifications not addressed
47、 in this practice may be needed forlocations where w is nonzero.8.6 Recalibrate and check instrument alignment at leastonce a week, whenever the instrument is subjected to asignificant change in weather conditions, or when transducersor electronics components are changed or adjusted.8.7 Check for bi
48、as, especially in w, using a data set collectedover an extended time period. The array support structure,topography, and changes in ambient temperature may producebiases in vertical velocity w. Procedures described in (3) arerecommended for bias compensation. (WarningUncompensated flow distortion du
49、e to the acoustic array andsupporting structure is possible when the vertical angle of theapproaching wind exceeds 615.)9. Calculations and Transformations9.1 Each sonic anemometer provides wind component mea-surements with respect to a coordinate system defined by itsarray axis alignment. Each array design requires specificcalculations and transformations to convert along-axis mea-surements to the desired wind component data. The calcula-tions and transformations are applicable to orthogonal arrays.References (4), (5), and (6) provide information
