ASTM D5366-96
(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
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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NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
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Designation: D 5366 – 96
Standard Test Method for
Determining the Dynamic Performance of a Wind Vane
This standard is issued under the fixed designation D 5366; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 2.2 Symbols:
D (m) delay distance
1.1 This test method covers the determination of the starting
U (m/s) starting threshold
o
threshold, delay distance, and overshoot ratio of a wind vane
V (none) overshoot ratio
from direct measurements in a wind tunnel. This test method is
h (none) damping ratio
l (m) damped natural wavelength
d
applicable only to wind vanes having measurable overshoot.
u (degrees) overshoot; maximum angular excursion
n
1.2 This test method provides for determination of the
u (degrees) reference direction
o
performance of a system consisting of a wind vane and its u (degrees) vane equilibrium position
B
u − u (degrees) dynamic vane bias
B o
associated position-to-output transducer in wind tunnel flow.
Use of values determined by this test method to describe
2.3 Calculated or Estimated Values:
performance in atmospheric flow of a wind direction measur-
2.3.1 damping ratio (h)—calculated from the overshoot
ing system incorporating the vane must be done with an
ratio (1,2).
understanding of the differences between the two systems and
ln~1/V!
the two environments.
h5 (2)
2 2 0.5
~p 1 @ln~1/V!# !
1.3 This standard does not purport to address all of the
2.3.2 damped natural wavelength (l )—at sea level in the
safety concerns, if any, associated with its use. It is the
d
U.S. Standard Atmosphere, damped natural wavelength is
responsibility of the user of this standard to establish appro-
related to delay distance and damping ratio by the empirical
priate safety and health practices and determine the applica-
expression (1,2).
bility of regulatory limitations prior to use.
D~6.0 2 2.4 !
h
2. Terminology
l 5 (3)
d
2 0.5
~12h !
2.1 Definitions:
2.1.1 delay distance (D)—the distance the air flows past a 3. Summary of Test Method
wind vane during the time it takes the vane to return to 50 %
3.1 Reference Direction (u , degrees) is the indicated
o
of the initial displacement.
angular position of the vane when aligned along the centerline
2.1.2 overshoot (u )—the amplitude of a deflection of a
n
of the wind tunnel.
wind vane as it oscillates about u after release from an initial
B
3.2 Vane Equilibrium Position (u , degrees) is the final
B
displacement.
resting position of the vane after motion in response to an
2.1.3 overshoot ratio (V)—the ratio of two successive
initial displacement. Ideally, u = u .
B o
overshoots, as expressed by the equation:
3.3 Dynamic Vane Bias (u − u , degrees) is the displace-
B o
V5u /u (1) ment of the vane from the wind tunnel centerline at 5 m/s. This
~n11! n
measurement will identify wind vanes with unbalanced aero-
where u and u are the n and n + 1 overshoots, respec-
n (n+1)
dynamic response because of damage (for example, bent tail)
tively. In practice, since deflections after the first (to the side
or poor design.
opposite the release point are normally small, the initial release
3.4 Starting Threshold (U , m/s) is determined by observ-
o
point (that is, the n = 0 deflection) and the first deflection after
ing or measuring the lowest speed at which the vane, released
release (n = 1) are used in determining the overshoot ratio.
from a 10° offset position in a wind tunnel, moves toward u .
B
2.1.4 starting threshold (U )—the lowest speed at which the
o
Movement must be distinguishable from vibration.
vane can be observed or measured moving from a 10° offset in
3.5 Delay Distance (D, m) may be determined at a number
a wind tunnel.
of wind speeds but shall include 5 m/s and 10 m/s. It is
computed from the time required for the vane to reach 50 % of
1 the initial displacement from 10° off u . This time in seconds
B
This test method is under the jurisdiction of ASTM Committee D-22 on
Sampling and Analysis of Atmospheres and is the direct responsibility of Subcom-
mittee D22.11 on Meterology.
Current edition approved Oct. 10, 1996. Published December 1996. Originally The boldface numbers in parentheses refer to the list of references at the end of
published as D 5366 – 93. Last previous edition D 5366 – 95. this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 5366
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
time as the delay distance. The maximum angular excursion on resolution may be changed as the wind tunnel speed is
the opposite side of u from the initial 10° displacement fromu changed. For example, for a distance constant measurement to
B
is measured. This value is divided by the initial displacement 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 This test method will provide a standard for comparison 5.3 Signal Conditioning—Care shall be taken to avoid
electronic circuits in signal conditioning and recording devices
of wind vanes of different types. Specifications by regulatory
agencies and industrial societies (3-5) have stipulated perfor- that adversely affect the apparent vane performance. CAU-
TION: Time constants in signal conditioning and recording
mance values. This test method provides an unambiguous
method for measuring starting threshold, delay distance, and devices shall be less than 0.01 s.
5.4 Recording Techniques—The measuring or recording
overshoot ratio.
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
fast-response recorder (flat to 40–60 Hz or better) with enough
5.1 Wind Tunnel (6):
gain so that a vane can be oriented in the wind tunnel with u
5.1.1 Size—The wind tunnel shall be large enough so that
B
represented at mid-scale, and 610° of vane displacement
the total projected area of supports, sensor apparatus, and the
traversing the full span of the recorder.
vane in its displaced position is less than 5 % of the cross-
5.4.1 The recorder shall have a fast chart speed of 50 mm/s
sectional area of its test section.
or more. An alternative is to use an FM tape recorder to record
5.1.2 Speed Range—The wind tunnel shall have a speed
the signal. When played back at lower speed, a proportionately
control that will allow the flow rate to be varied from 0 to at
slower analog strip chart recorder yielding an equivalent
least 10 m/s. The speed control shall maintain the flow rate
50-mm/s chart speed is acceptable. Oscilloscopes with memory
within 60.2 m/s.
and hard copy capability may also be used.
5.1.3 Turbulence and Swirl—Across the volume to be
5.4.2 Digital recording and data reduction systems are
occupied by the vane, the flow profile shall vary by no more
satisfactory if the sampling rate is at least 100 per second.
than 1 % about the mean speed and shall exhibit a turbulence
of less than 1 %. CAUTION: Swirl in the wind tunnel may
6. Sampling
influence starting threshold measurements. Variations in the
6.1 Starting Threshold—Ten consecutive tests at the same
measurement of u a low speeds likely indicate the existence of
B
speed meeting the test method requirement, five in each
swirl.
direction from u , are required for a valid starting threshold
5.1.4 Calibration—The mean flow rate sha
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