ASTM_D_5366_-_96_2017.pdf

Designation:D536696(Reapproved 2017)Standard Test Method forDetermining the Dynamic Performance of a Wind Vane1This standard is issued under the fixed designation D5366;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the determination of the startingthreshold,delay distance,and overshoot ratio of a wind vanefrom direct measurements in a wind tunnel.This test method isapplicable only to wind vanes having measurable overshoot.1.2 This test method provides for determination of theperformance of a system consisting of a wind vane and itsassociated position-to-output transducer in wind tunnel flow.Use of values determined by this test method to describeperformance in atmospheric flow of a wind direction measur-ing system incorporating the vane must be done with anunderstanding of the differences between the two systems andthe two environments.1.3 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.4 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 use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:2D1356 Terminology Relating to Sampling and Analysis ofAtmospheres3.Terminology3.1 For terms that are not defined herein,refer to Terminol-ogy D1356.3.2 Definitions:3.2.1 delay distance(D)the distance the air flows past awind vane during the time it takes the vane to return to 50%of the initial displacement.3.2.2 overshoot(n)the amplitude of a deflection of awind vane as it oscillates about Bafter release from an initialdisplacement.3.2.3 overshoot ratio()the ratio of two successiveovershoots,as expressed by the equation:5 n11!/n(1)where nand(n+1)are the n and n+1 overshoots,respec-tively.In practice,since deflections after the first(to the sideopposite the release point are normally small,the initial re-lease point(that is,the n=0 deflection)and the first deflec-tion after release(n=1)are used in determining the over-shoot ratio.3.2.4 starting threshold(Uo)the lowest speed at which thevane can be observed or measured moving from a 10 offset ina wind tunnel.3.3 Symbols:D(m)delay distanceUo(m/s)starting threshold(none)overshoot ratio(none)damping ratiod(m)damped natural wavelengthn(degrees)overshoot;maximum angular excursiono(degrees)reference directionB(degrees)vane equilibrium positionB o(degrees)dynamic vane bias3.4 Calculated or Estimated Values:3.4.1 damping ratio()calculated from the overshootratio(1,2).3 5ln1/!21ln1/!#2!0.5(2)1This test method is under the jurisdiction of ASTM Committee D22 on AirQuality and is the direct responsibility of Subcommittee D22.11 on Meteorology.Current edition approved March 15,2017.Published March 2017.Originallyapproved in 1993.Last previous edition approved in 2011 as D5366 96(2011).DOI:10.1520/D5366-96R17.2For referenced ASTM standards,visit the ASTM website,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 standard.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.1 3.4.2 damped natural wavelength(d)at sea level in theU.S.Standard Atmosphere,damped natural wavelength isrelated to delay distance and damping ratio by the empiricalexpression(1,2).3d5D6.02 2.4!1 2 2!0.5(3)4.Summary of Test Method4.1 Reference Direction(o,degrees)is the indicated angu-lar position of the vane when aligned along the centerline of thewind tunnel.4.2 Vane Equilibrium Position(B,degrees)is the finalresting position of the vane after motion in response to aninitial displacement.Ideally,B=o.4.3 Dynamic Vane Bias(B o,degrees)is the displace-ment of the vane from the wind tunnel centerline at 5 m/s.Thismeasurement will identify wind vanes with unbalanced aero-