1、Designation: D 5741 96 (Reapproved 2007)e1Standard Practice forCharacterizing Surface Wind Using a Wind Vane andRotating Anemometer1This standard is issued under the fixed designation D 5741; the number immediately following the designation indicates the year oforiginal adoption or, in the case of r
2、evision, the 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.e1NOTEEditorially added the term “degrees” to subection 4.1.3 in October 2007.1. Scope1.1 This practice cove
3、rs a method for characterizing surfacewind speed, wind direction, peak one-minute speeds, peakthree-second and peak one-minute speeds, and standard devia-tions of fluctuation about the means of speed and direction.1.2 This practice may be used with other kinds of sensors ifthe response characteristi
4、cs of the sensors, including theirsignal conditioners, are equivalent or faster and the measure-ment uncertainty of the system is equivalent or better thanthose specified below.1.3 The characterization prescribed in this practice willprovide information on wind acceptable for a wide variety ofapplic
5、ations.NOTE 1This practice builds on a consensus reached by the attendeesat a workshop sponsored by the Office of the Federal Coordinator forMeteorological Services and Supporting Research in Rockville, MD onOct. 2930, 1992.1.4 This standard does not purport to address all of thesafety concerns, if
6、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 use.2. Referenced Documents2.1 ASTM Standards:2D 1356 Terminology Relating to Sampling and Anal
7、ysis ofAtmospheresD 5096 Test Method for Determining the Performance of aCup Anemometer or Propeller AnemometerD 5366 Test Method for Determining the Dynamic Perfor-mance of a Wind Vane3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 aerodynamic roughness length (z0, m)a charac
8、teris-tic length representing the height above the surface whereextrapolation of wind speed measurements, below the limit ofprofile validity, would predict the wind speed would becomezero (1).3It can be estimated for direction sectors from alandscape description.3.1.2 damped natural wavelength (ld,
9、m)a characteristicof a wind vane empirically related to the delay distance and thedamping ratio. See Test Method D 5366 for test methods todetermine the delay distance and equations to estimate thedamped natural wavelength.3.1.3 damping ratio (h, dimensionless)the ratio of theactual damping, related
10、 to the inertial-driven overshoot of windvanes to direction changes, to the critical damping, the fastestresponse where no overshoot occurs. See Test Method D 5366for test methods and equations to determine the damping ratioof a wind vane.3.1.4 distance constant (L, m)the distance the air flowspast
11、a rotating anemometer during the time it takes the cupwheel or propeller to reach (1 1/e) or 63 % of the equilibriumspeed after a step change in wind speed. See Test MethodD 5096.3.1.5 maximum operating speed (um, m/s)as related toanemometer, the highest speed as which the sensor will survivethe for
12、ce of the wind and perform within the accuracyspecification.3.1.6 maximum operating speed (um, m/s)as related towind vane, the highest speed at which the sensor will survivethe force of the wind and perform within the accuracyspecification.3.1.7 standard deviation of wind direction (su, degrees)the
13、unbiased estimate of the standard deviation of winddirection samples about the mean horizontal wind direction.The circular scale of wind direction with a discontinuity at1This practice is under the jurisdiction ofASTM Committee D22 onAir Qualityand is the direct responsibility of Subcommittee D22.11
14、 on Meteorology.Current edition approved Oct. 1, 2007. Published December 2007. Originallyapproved in 1996. Last previous edition approved in 2002 as D5741 - 96(2002)e1.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annua
15、l Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The boldface numbers in parentheses refers to the list of references at the endof this standard.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-
16、2959, United States.north may bias the calculation when the direction oscillatesabout north. Estimates of the standard deviation such assuggested by (2, 3) are acceptable.3.1.8 standard deviation of wind speed (su, m/s)theestimate of the standard deviation of wind speed samples aboutthe mean wind sp
17、eed.3.1.9 starting threshold (u0, m/s)as related to anemom-eter, the lowest speed at which the sensor begins to turn andcontinues to turn and produces a measurable signal whenmounted in its normal position (see Test Method D 5096).3.1.10 starting threshold (u0, m/s)as related to system, theindicated
18、 wind speed when the anemometer is at rest.3.1.11 starting threshold (u0, m/s)as related to wind vane,the lowest speed at which the vane can be observed ormeasured moving from a 10 offset position in a wind tunnel(see Test Method D 5366).3.1.12 wind direction (u, degrees)the direction, refer-enced t
19、o true north, from which air flows past the sensorlocation if the sensor or other obstructions were absent. Thewind direction distribution is characterized over each 10-minperiod with a scalar (non-speed weighted) mean, standarddeviation, and the direction of the peak 1-min average speed.The circula
20、r direction range, with its discontinuity at north,requires special attention in the averaging process. A unitvector method is an acceptable solution to this problem.3.1.12.1 DiscussionWind vane direction systems provideoutputs when the wind speed is below the starting threshold forthe vane. For thi
21、s practice, report the calculated values (see 4.3or 4.4) when more than 25 % of the possible samples are abovethe wind vane threshold and the standard deviation of theacceptable samples, su, is 30 or less, otherwise report lightand variable code, 000.3.1.13 wind speed (u, m/s)the speed with which ai
22、r flowspast the sensor location if the sensor or other obstructions wereabsent. The wind speed distribution is characterized over each10-min period with a scalar mean, standard deviation, peak 3-saverage, and peak 1-min average.3.2 For definitions of additional terms used in this practice,refer to T
23、erminology D 1356.4. Summary of Practice4.1 Siting of the Wind Sensors:4.1.1 The wind sensor location will be identified by anunambiguous label which will include either the longitude andlatitude with a resolution of1sofarc(about 30 m or less) ora station number which will lead to that information i
24、n thestation description file. When redundant sensors or microscalenetwork stations (for example, airport runway sensors) areavailable, they will have individual labels which unambigu-ously identify the data they produce.4.1.2 The anemometer and wind vane shall be located at a10-m height above level
25、 or gently sloping terrain with an openfetch of at least 150 m in all directions, with the largest fetchpossible in the prevailing wind direction. Compromise isfrequently recognized and acceptable for some sites. Obstaclesin the vicinity should be at least ten times their own heightdistant from the
26、wind sensors.4.1.3 The wind sensors shall preferably be located on top ofa solitary mast. If side mounting is necessary, the boom lengthshould be at least three times the mast width. In the undesirablecase that locally no open terrain is available and the measure-ment is to be made above some buildi
27、ng, then the wind sensorheight above the roof top should be at least 1.5 times the lesserof the maximum building height and the maximum horizontaldimension of the major roof surface. In this case, the stationdescription file shall indicate the height above ground level(AGL) of the highest part of th
28、e building, the height of thewind sensors above ground, AGL, and the height of the windsensors above roof level. Site characteristics shall be docu-mented in sectors no greater than 45 degrees nor smaller than30 degrees in width around the wind sensors. The near terrainmay be characterized with phot
29、ographs, taken at wind sensorheight if possible, aimed radially outward at labeled centralangles, with respect to true north. Average roughness of thenearest 3 km of each sector shall be characterized according tothe roughness class as tabulated above (4). The z0numbers inTable 1 are typical and not
30、 precise statements.4.1.4 Important terrain features at distances larger than 3 km(hills, cities, lakes, and so forth, within 20 km) shall beidentified by sector and distance. Additional information, suchas aerial photographs, maps, and so forth, pertinent to the site,is recommended to be added to t
31、he basic site documentation.TABLE 1 Characterizations Extracted from Wieringa, J. (4)No. z0, m Landscape Description1: 0.0002 Sea Open sea or lake (irrespective of the wave size), tidal flat, snow-covered flat plain, featureless desert, tarmac and concrete, with afree fetch of several kilometres.2:
32、0.005 Smooth Featureless land surface without any noticeable obstacles and with negligible vegetation; for example, beaches, pack ice withoutlarge ridges, morass, and snow-covered or fallow open country.3: 0.03 Open Level country with low vegetation (for example, grass) and isolated obstacles with s
33、eparations of at least 50 obstacle heights; forexample, grazing land without windbreaks, heather, moor and tundra, runway area of airports.4: 0.10 Roughly open Cultivated area with regular cover of low crops, or moderately open country with occasional obstacles (for example, low hedges,single rows o
34、f trees, isolated farms) at relative horizontal distances of at least 20 obstacle heights.5: 0.25 Rough Recently developed young landscape with high crops or crops of varying heights, and scattered obstacles (for example, denseshelter-belts, vineyards) at relative distances of about 15 obstacle heig
35、hts.6: 0.5 Very rough Old cultivated landscape with many rather large obstacle groups (large farms, clumps of forest) separated by open spaces of about10 obstacle heights. Also low-large vegetation with small interspaces, such as bushland, orchards, young densely planted forest.7: 1.0 Closed Landsca
36、pe totally and quite regularly covered with similar-size large obstacles, with open spaces comparable to the obstacle heights;for example, mature regular forests, homogeneous cities, or villages.8: 2 Chaotic Centers of large towns with mixture of low-rise and high-rise buildings. Also irregular larg
37、e forests with many clearings.D 5741 96 (2007)e12NOTE 2Cameras using 35-mm film in the landscape orientation willhave the following theoretical focal length to field angle relationships:50 mm yields 4040 mm yields 4828 mm yields 66Prints or transparencies may not utilize the total theoretical width
38、of theimage. It is desirable to label known angles in the photograph. Forexample, a 45 sector photograph could have a central label of 360 withmarker flags located at 337.5 and 022.5 true.4.2 Characteristics of the Wind SystemsThere are twocategories of sensor design within this practice. Sensitived
39、escribes sensors commonly applied for all but extreme windconditions. Ruggedized describes sensors intended to functionduring extreme wind conditions. The application of this prac-tice requires the starting threshold (u0) of both the wind vaneand the anemometer to meet the same operating range cat-e
40、gory.4.2.1 Operating Range:Category Starting Threshold, u0Maximum Speed, umSensitive 0.5 m/s 50 m/sRuggedized 1.0 m/s 90 m/s4.2.2 Dynamic Response CharacteristicsDynamic re-sponse characteristics of the measurement system may includeboth the sensor response and a measurement circuit contribu-tion. T
41、he specified values are for the entire measurementsystem, including sensors and signal conditioners (5).Itisexpected that the characteristics of the sensors, which can beindependently determined by the referenced Test MethodsD 5096 and D 5366, will not be measurably altered by thecircuitry.Anemomete
42、r Distance constant, L 0.3Wind vane Damped natural wavelength, ld10 m/s 5 % of readingWind direction Degrees of arc to true north 65 (see Note 5)NOTE 3The relative accuracy of the position of the vane with respectto the sensor base should be less than 63 for averaged samples. The biasof the sensor b
43、ase alignment to true north should be less than 62.4.2.4 Measurement Resolution:Average Standard De-viationWind speed 0.1 m/s 0.1 m/sWind direction 1 0.14.2.5 SamplingPeriods of time, specified as the averagingintervals, are fixed clock periods and not running or overlap-ping intervals, except for t
44、he three-second gust. Outputs mustbe continuously and uniformly sampled during the reportingperiod. Incomplete data must be identified.Wind speed 1 to3s(seeNote 4)Winddirection 1to3s(seeNote 5)NOTE 4A true 3-s average wind speed results from counting theoutput pulses of the anemometer transducer for
45、 3 s. If a pulse-generatingtransducer is not used, a suitable sampling rate and averaging method isrequired to produce a true 3-s average.NOTE 5A sample of the wind direction may be used ONLY when thesample of wind speed is at or above the wind direction starting threshold.4.3 Standard Data Output f
46、or ArchivesTime labels shoulduse the ending time of the interval. If a different labelingmethod is consistently used, it must be defined. The dataoutputs are listed as follows:4.3.1 Ten-minute scalar averaged wind speed.4.3.2 Ten-minute unit vector or scalar averaged wind direc-tion.4.3.3 Fastest 3-
47、s gust during the 10-min period.4.3.4 Time of the fastest 3-s gust during the 10-min period.4.3.5 Fastest 1-min scalar averaged wind speed during the10-min period (fastest minute).4.3.6 Average wind direction for the fastest 1-min windspeed.4.3.7 Standard deviation of the wind speed samples (1 to 3s
48、) about the 10-min mean speed (su).4.3.8 Standard deviation of the wind direction samples (1 to3 s) about the 10-min mean direction (su).4.4 Optional Condensed Data Output for ArchivesSomenetworks will not be able to save eight 10-min data sets (48values plus time and identification) each hour. For
49、those cases,an abbreviated or condensed alternative is provided. When thecondensed output is employed the following outputs arerequired.4.4.1 Sixty-minute scalar averaged wind speed.4.4.2 Sixty-minute unit vector or scalar averaged winddirection.4.4.3 Fastest 3-s gust during the 60-min period.4.4.4 Wind direction for the fastest 3-s gust.4.4.5 Fastest 1-min scalar averaged wind speed during the60-min period.4.4.6 Average wind direction for the fastest 1-min windspeed.4.4.7 Ending time of the fastest 1-min wind speed.4.4.8 Root-mean-square of six
