ASTM D5366-96(2011)
(Test Method)Standard Test Method for Determining the Dynamic Performance of a Wind Vane
Standard Test Method for Determining the Dynamic Performance of a Wind Vane
SIGNIFICANCE AND USE
This test method will provide a standard for comparison of wind vanes of different types. Specifications by regulatory agencies and industrial societies (3-5) have stipulated performance values. This test method provides an unambiguous method for measuring starting threshold, delay distance, and overshoot ratio.
SCOPE
1.1 This test method covers the determination of the starting threshold, delay distance, and overshoot ratio of a wind vane from direct measurements in a wind tunnel. This test method is applicable only to wind vanes having measurable overshoot.
1.2 This test method provides for determination of the performance of a system consisting of a wind vane and its associated position-to-output transducer in wind tunnel flow. Use of values determined by this test method to describe performance in atmospheric flow of a wind direction measuring system incorporating the vane must be done with an understanding of the differences between the two systems and the two environments.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D5366 − 96 (Reapproved 2011)
Standard Test Method for
Determining the Dynamic Performance of a Wind Vane
This standard is issued under the fixed designation D5366; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2.1.4 starting threshold (U )—thelowestspeedatwhichthe
o
vane can be observed or measured moving from a 10° offset in
1.1 Thistestmethodcoversthedeterminationofthestarting
a wind tunnel.
threshold, delay distance, and overshoot ratio of a wind vane
fromdirectmeasurementsinawindtunnel.Thistestmethodis 2.2 Symbols:
applicable only to wind vanes having measurable overshoot.
D (m) delay distance
U (m/s) starting threshold
o
1.2 This test method provides for determination of the
Ω (none) overshoot ratio
performance of a system consisting of a wind vane and its
η (none) damping ratio
λ (m) damped natural wavelength
associated position-to-output transducer in wind tunnel flow. d
θ (degrees) overshoot; maximum angular excursion
n
Use of values determined by this test method to describe
θ (degrees) reference direction
o
performance in atmospheric flow of a wind direction measur-
θ (degrees) vane equilibrium position
B
θ − θ (degrees) dynamic vane bias
B o
ing system incorporating the vane must be done with an
understanding of the differences between the two systems and 2.3 Calculated or Estimated Values:
the two environments. 2.3.1 damping ratio (η)—calculated from the overshoot
ratio (1,2).
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the ln 1/Ω
~ !
η 5 (2)
2 2 0.5
responsibility of the user of this standard to establish appro-
~π 1@ln~1/Ω!# !
priate safety and health practices and determine the applica-
2.3.2 damped natural wavelength (λ )—at sea level in the
d
bility of regulatory limitations prior to use.
U.S. Standard Atmosphere, damped natural wavelength is
related to delay distance and damping ratio by the empirical
2. Terminology
expression (1,2).
2.1 Definitions:
D~6.0 22.4η!
2.1.1 delay distance (D)—the distance the air flows past a
λ 5 (3)
d 2 0.5
1 2η
~ !
wind vane during the time it takes the vane to return to 50%
of the initial displacement.
3. Summary of Test Method
2.1.2 overshoot (θ )—the amplitude of a deflection of a
n
3.1 Reference Direction (θ , degrees) is the indicated angu-
wind vane as it oscillates about θ after release from an initial o
B
larpositionofthevanewhenalignedalongthecenterlineofthe
displacement.
wind tunnel.
2.1.3 overshoot ratio (Ω)—the ratio of two successive
3.2 Vane Equilibrium Position (θ , degrees) is the final
overshoots, as expressed by the equation:
B
resting position of the vane after motion in response to an
Ω 5θ /θ (1)
n11 n
~ !
initial displacement. Ideally, θ =θ .
B o
where θ and θ are the n and n+1 overshoots, respec-
n (n+1)
3.3 Dynamic Vane Bias (θ −θ , degrees) is the displace-
B o
tively. In practice, since deflections after the first (to the side
mentofthevanefromthewindtunnelcenterlineat5m/s.This
opposite the release point are normally small, the initial re-
measurement will identify wind vanes with unbalanced aero-
lease point (that is, the n=0 deflection) and the first deflec-
dynamic response because of damage (for example, bent tail)
tion after release (n=1) are used in determining the over-
or poor design.
shoot ratio.
3.4 Starting Threshold(U ,m/s)isdeterminedbyobserving
o
ormeasuringthelowestspeedatwhichthevane,releasedfrom
This test method is under the jurisdiction of ASTM Committee D22 on Air
Quality and is the direct responsibility of Subcommittee D22.11 on Meteorology.
Current edition approved Oct. 1, 2011. Published October 2011. Originally
approved in 1993. Last previous edition approved in 2007 as D5366-96(2007). Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
DOI: 10.1520/D5366-96R11. this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5366 − 96 (2011)
a 10° offset position in a wind tunnel, moves toward θ . threshold, delay distance, and overshoot ratio since these
B
Movement must be distinguishable from vibration. values are density dependent.
3.5 Delay Distance (D, m) may be determined at a number
5.2 Measuring System:
of wind speeds but shall include 5 m/s and 10 m/s. It is
5.2.1 Direction—The resolution of the wind vane position-
computedfromthetimerequiredforthevanetoreach50%of
–to–output transducer limits the resolution of the measure-
the initial displacement from 10° off θ . This time in seconds
ments.Theaccuracyoftheposition–to–outputconversionshall
B
is converted to delay distance by multiplying by the wind
be within 60.1°. (Warning—Avoid potentiometer dead spots
tunnel speed in metres per second.Tests shall include an equal
or crossover positions while performing these procedures.)
number of displacements to each side of θ .
B 5.2.2 Time—The resolution of time shall be consistent with
the distance accuracy required. For this reason, the time
3.6 Overshoot Ratio (Ω) may be determined at the same
resolution may be changed as the wind tunnel speed is
timeasthedelaydistance.Themaximumangularexcursionon
changed. For example, for a distance constant measurement to
the opposite side of θ from the initial 10° displacement
B
0.1 m, one must have a time resolution of 0.05 s at 2 m/s and
fromθ is measured. This value is divided by the initial
B
0.01 s at 10 m/s. If time accuracy is based on commercial
displacement to obtain Ω.
electrical power frequency, it will be at least an order of
magnitude better than the resolution suggested above.
4. Significance and Use
4.1 Thistestmethodwillprovideastandardforcomparison 5.3 Signal Conditioning—Care shall be taken to avoid
of wind vanes of different types. Specifications by regulatory electroniccircuitsinsignalconditioningandrecordingdevices
agencies and industrial societies (3-5) have stipulated perfor- that adversely affect the apparent vane performance.
mance values. This test method provides an unambiguous (Warning—Time constants in signal conditioning and record-
method for measuring starting threshold, delay distance, and ing devices shall be less than 0.01 s.)
overshoot ratio.
5.4 Recording Techniques—The measuring or recording
system shall represent the 10° displacement on each side ofθ
B
5. Apparatus
with a resolution of 0.2°. One simple technique is to use a
5.1 Wind Tunnel (6):
fast-response recorder (flat to 40–60 Hz or better) with enough
5.1.1 Size—The wind tunnel shall be large enough so that
gain so that a vane can be oriented in the wind tunnel with θ
B
the total projected area of supports, sensor apparatus, and the
represented at mid-scale, and 610° of vane displacement
vane in its displaced position is less than 5% of the cross-
traversing the full span of the recorder.
sectional area of its test section.
5.4.1 The recorder shall have a fast chart speed of 50 mm/s
5.1.2 Speed Range—The wind tunnel shall have a speed
or more.An alternative is to use an FM tape recorder to record
control that will allow the flow rate to be varied from 0 to at
thesignal.Whenplayedbackatlowerspeed,aproportionately
least 10 m/s. The speed control shall maintain the flow rate
slower analog strip chart recorder yielding an equivalent
within 60.2 m/s.
50-mm/schartspeedisacceptable.Oscilloscopeswithmemory
5.1.3 Turbulence and Swirl—Across the volume to be oc-
and hard copy capability may also be used.
cupiedbythevane,theflowprofileshallvarybynomorethan
5.4.2 Digital recording and data reduction systems are
1%aboutthemeanspeedandshallexhibitaturbulenceofless
satisfactory if the sampling rate is at least 100 per second.
than 1%. (Warning— Swirl in the wind tunnel may influence
starting threshold measurements. Variations in
...
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