ASTM D5366-96(2002)e01
(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 2002)
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 (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Several editorial changes were made throughout the standard in October 2002.
1. Scope point (that is, the n=0 deflection) and the first deflection after
release (n=1) are used in determining the overshoot ratio.
1.1 Thistestmethodcoversthedeterminationofthestarting
2.1.4 starting threshold (U )—thelowestspeedatwhichthe
o
threshold, delay distance, and overshoot ratio of a wind vane
vane can be observed or measured moving from a 10° offset in
fromdirectmeasurementsinawindtunnel.Thistestmethodis
a wind tunnel.
applicable only to wind vanes having measurable overshoot.
2.2 Symbols:
1.2 This test method provides for determination of the
D (m) delay distance
performance of a system consisting of a wind vane and its
U (m/s) starting threshold
o
associated position-to-output transducer in wind tunnel flow.
V (none) overshoot ratio
Use of values determined by this test method to describe h (none) damping ratio
l (m) damped natural wavelength
performance in atmospheric flow of a wind direction measur- d
u (degrees) overshoot; maximum angular excursion
n
ing system incorporating the vane must be done with an
u (degrees) reference direction
o
understanding of the differences between the two systems and
u (degrees) vane equilibrium position
B
u − u (degrees) dynamic vane bias
B o
the two environments.
1.3 This standard does not purport to address all of the
2.3 Calculated or Estimated Values:
safety concerns, if any, associated with its use. It is the
2.3.1 damping ratio (h)—calculated from the overshoot
responsibility of the user of this standard to establish appro-
ratio (1,2).
priate safety and health practices and determine the applica-
ln~1/V!
bility of regulatory limitations prior to use. h5 (2)
2 2 0.5
p 1 ln 1/V
~ @ ~ !# !
2. Terminology
2.3.2 damped natural wavelength (l )—at sea level in the
d
U.S. Standard Atmosphere, damped natural wavelength is
2.1 Definitions:
related to delay distance and damping ratio by the empirical
2.1.1 delay distance (D)—the distance the air flows past a
expression (1,2).
wind vane during the time it takes the vane to return to 50%
of the initial displacement.
D~6.0 22.4h!
l 5 (3)
d
2.1.2 overshoot (u )—the amplitude of a deflection of a 2 0.5
n
~12h !
wind vane as it oscillates about u after release from an initial
B
3. Summary of Test Method
displacement.
2.1.3 overshoot ratio (V)—the ratio of two successive
3.1 Reference Direction (u , degrees) is the indicated
o
overshoots, as expressed by the equation:
angular position of the vane when aligned along the centerline
V5u /u (1)
of the wind tunnel.
~n11! n
3.2 Vane Equilibrium Position (u , degrees) is the final
B
where u and u are the n and n+1 overshoots, respec-
n (n+1)
resting position of the vane after motion in response to an
tively. In practice, since deflections after the first (to the side
initial displacement. Ideally, u = u .
B o
oppositethereleasepointarenormallysmall,theinitialrelease
3.3 Dynamic Vane Bias (u − u , degrees) is the displace-
B o
mentofthevanefromthewindtunnelcenterlineat5m/s.This
This test method is under the jurisdiction of ASTM Committee D22 on
Sampling andAnalysis ofAtmospheres and is the direct responsibility of Subcom-
mittee D22.11 on Meterology.
Current edition approved October 10, 1996. Published December 1996. Origi- Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
nally published as D5366–93. Last previous edition D5366–95. this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D5366–96 (2002)
measurement will identify wind vanes with unbalanced aero- 5.1.5 Environment—The temperature and pressure of the
dynamic response because of damage (for example, bent tail) environment within the wind tunnel test section shall be
or poor design. reported. Differences of greater than 3% in the density of air
3.4 Starting Threshold (U , m/s) is determined by observ- within the test environment may result in poor inter-
o
ing or measuring the lowest speed at which the vane, released comparability of independent measurements of starting thresh-
from a 10° offset position in a wind tunnel, moves toward u . old, delay distance, and overshoot ratio since these values are
B
Movement must be distinguishable from vibration. 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 u . This time in seconds ments.Theaccuracyoftheposition–to–outputconversionshall
B
is converted to delay distance by multiplying by the wind be within 60.1°. CAUTION: 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 u . 5.2.2 Time—The resolution of time shall be consistent with
B
3.6 Overshoot Ratio (V) may be determined at the same
the distance accuracy required. For this reason, the time
timeasthedelaydistance.Themaximumangularexcursionon
resolution may be changed as the wind tunnel speed is
theoppositesideof u fromtheinitial10°displacementfromu
changed. For example, for a distance constant measurement to
B
ismeasured.Thisvalueisdividedbytheinitialdisplacement
0.1 m, one must have a time resolution of 0.05 s at 2 m/s and
B
to obtain V. 0.01 s at 10 m/s. If time accuracy is based on commercial
electrical power frequency, it will be at least an order of
4. Significance and Use
magnitude better than the resolution suggested above.
4.1 Thistestmethodwillprovideastandardforcomparison 5.3 Signal Conditioning—Care shall be taken to avoid
of wind vanes of different types. Specifications by regulatory
electronic circuits in signal conditioning and recording devices
agencies and industrial societies (3-5) have stipulated perfor- that adversely affect the apparent vane performance. CAU-
mance values. This test method provides an unambiguous
TION: Time constants in signal conditioning and recording
method for measuring starting threshold, delay distance, and 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 of u
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 u
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
...
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