Form Approved
REPORT DOCUMENTATION PAGE
OMB No. 0704-0188
Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and
maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information,
including suggestion for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington,
VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503.
1. AGENCY USE ONLY (Leave blank)
2. REPORT DATE
3. REPORT TYPE AND DATES COVERED
October 1995
4. TITLE AND SUBTITLE
5. FUNDING NUMBERS
Sensible Heat Flux Measurements Near a Cold Surface
PE: 6.11.02A
PR: 4A161192AT24
TA: SS
6. AUTHORS
WU: E09
Yin-Chao Yen
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)
8. PERFORMING ORGANIZATION
REPORT NUMBER
U.S. Army Cold Regions Research and Engineering Laboratory
72 Lyme Road
CRREL Report 95-22
Hanover, New Hampshire 03755-1290
9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)
10. SPONSORING/MONITORING
AGENCY REPORT NUMBER
Office of the Chief of Engineers
Washington, D.C. 20314-1000
11. SUPPLEMENTARY NOTES
12a. DISTRIBUTION/AVAILABILITY STATEMENT
12b. DISTRIBUTION CODE
Approved for public release; distribution is unlimited.
Available from NTIS, Springfield, Virginia 22161
13. ABSTRACT (Maximum 200 words)
A unidirectional sonic anemometer with a fine-wire thermocouple in conjunction with a hot film anemometer were
employed to measure the turbulent fluctuating velocities of w ′, u′, and the fluctuating temperature T′. Covariances were
evaluated to compute the turbulent heat flux and the friction velocity. Based on preliminary data, it can be noted that the
values of fluctuating vertical velocity and temperature, the friction velocity, and the standard deviations of vertical and
horizontal turbulent fluctuating velocities can all be correlated rather well with a single variable, i.e., the mean wind speed
measured at a height of 2 m. In all the plots of friction velocity, vertical and horizontal turbulent fluctuating velocities, and
the fluctuating vertical velocity and temperature vs. the mean wind speed at 2 m, the slopes are slightly lowered as the test
season progressed from early summer to the winter. The most striking reduction can be observed in the case of the
fluctuating vertical velocity and temperature vs. mean wind speed at 2 m. During the winter period, the slope is only about
one third of that during the springsummer period. In other words, under unstable conditions, for the same mean wind
speed, the heat flux during the winter is only about one third of the flux that would have occurred during the spring
summer. Under stable conditions, the magnitude of the fluctuating vertical velocity and temperature is much smaller, and its
value shows much greater dispersion. The values of fluctuating vertical velocity and temperature cannot be correlated in
any meaningful manner, as is the case under unstable conditions, by the mean wind speed alone. Comparisons were made
with the few existing measured data or with predictions from theoretical expressions, and they were found to be in fairly
good agreement in some cases and to have large divergence in others.
14. SUBJECT TERMS
15. NUMBER OF PAGES
52
Energy balance
Fluctuating velocity
Turbulence
16. PRICE CODE
Fluctuating temperature
Sensible heat flux
17. SECURITY CLASSIFICATION
18. SECURITY CLASSIFICATION
19. SECURITY CLASSIFICATION
20. LIMITATION OF ABSTRACT
OF REPORT
OF THIS PAGE
OF ABSTRACT
UNCLASSIFIED
UNCLASSIFIED
UNCLASSIFIED
UL
Standard Form 298 (Rev. 2-89)
NSN 7540-01-280-5500
Prescribed by ANSI Std. Z39-18
298-102
Previous Page
