Details
| Original language | English |
|---|---|
| Pages (from-to) | 357-377 |
| Number of pages | 21 |
| Journal | Boundary-Layer Meteorology |
| Volume | 148 |
| Issue number | 2 |
| Early online date | 9 Apr 2013 |
| Publication status | Published - Aug 2013 |
Abstract
This study conducted large-eddy simulations (LES) of fully developed turbulent flow within and above explicitly resolved buildings in Tokyo and Nagoya, Japan. The more than 100 LES results, each covering a 1,000 × 1,000 m2 area with 2-m resolution, provide a database of the horizontally-averaged turbulent statistics and surface drag corresponding to various urban morphologies. The vertical profiles of horizontally-averaged wind velocity mostly follow a logarithmic law even for districts with high-rise buildings, allowing estimates of aerodynamic parameters such as displacement height and roughness length using the von Karman constant= 0.4. As an alternative derivation of the aerodynamic parameters, a regression of roughness length and variable Karman constant was also attempted, using a displacement height physically determined as the central height of drag action. Although both the regression methods worked, the former gives larger (smaller) values of displacement height (roughness length) by 20-25 % than the latter. The LES database clearly illustrates the essential difference in bulk flow properties between real urban surfaces and simplified arrays. The vertical profiles of horizontally-averaged momentum flux were influenced by the maximum building height and the standard deviation of building height, as well as conventional geometric parameters such as the average building height, frontal area index, and plane area index. On the basis of these investigations, a new aerodynamic parametrization of roughness length and displacement height in terms of the five geometric parameters described above was empirically proposed. The new parametrizations work well for both real urban morphologies and simplified model geometries.
Keywords
- Aerodynamic parametrization, Displacement height, Large-eddy simulation, Real urban surfaces, Three-dimensional building map
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Atmospheric Science
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In: Boundary-Layer Meteorology, Vol. 148, No. 2, 08.2013, p. 357-377.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - A New Aerodynamic Parametrization for Real Urban Surfaces
AU - Kanda, Manabu
AU - Inagaki, Atsushi
AU - Miyamoto, Takashi
AU - Gryschka, Micha
AU - Raasch, Siegfried
N1 - Funding Information: Acknowledgments This research was financially supported by Research Program on Climate Change Adaptation (RECCA), a Grant-in-Aid for Scientific Research (B): 21360233, and a Grant-in-Aid for Young Scientists (B): 23760454 from the Ministry of Education, Culture, Sports, Science and Technology, Japan. This research was also supported by the German Research Foundation under Grant RA 617/15-2.
PY - 2013/8
Y1 - 2013/8
N2 - This study conducted large-eddy simulations (LES) of fully developed turbulent flow within and above explicitly resolved buildings in Tokyo and Nagoya, Japan. The more than 100 LES results, each covering a 1,000 × 1,000 m2 area with 2-m resolution, provide a database of the horizontally-averaged turbulent statistics and surface drag corresponding to various urban morphologies. The vertical profiles of horizontally-averaged wind velocity mostly follow a logarithmic law even for districts with high-rise buildings, allowing estimates of aerodynamic parameters such as displacement height and roughness length using the von Karman constant= 0.4. As an alternative derivation of the aerodynamic parameters, a regression of roughness length and variable Karman constant was also attempted, using a displacement height physically determined as the central height of drag action. Although both the regression methods worked, the former gives larger (smaller) values of displacement height (roughness length) by 20-25 % than the latter. The LES database clearly illustrates the essential difference in bulk flow properties between real urban surfaces and simplified arrays. The vertical profiles of horizontally-averaged momentum flux were influenced by the maximum building height and the standard deviation of building height, as well as conventional geometric parameters such as the average building height, frontal area index, and plane area index. On the basis of these investigations, a new aerodynamic parametrization of roughness length and displacement height in terms of the five geometric parameters described above was empirically proposed. The new parametrizations work well for both real urban morphologies and simplified model geometries.
AB - This study conducted large-eddy simulations (LES) of fully developed turbulent flow within and above explicitly resolved buildings in Tokyo and Nagoya, Japan. The more than 100 LES results, each covering a 1,000 × 1,000 m2 area with 2-m resolution, provide a database of the horizontally-averaged turbulent statistics and surface drag corresponding to various urban morphologies. The vertical profiles of horizontally-averaged wind velocity mostly follow a logarithmic law even for districts with high-rise buildings, allowing estimates of aerodynamic parameters such as displacement height and roughness length using the von Karman constant= 0.4. As an alternative derivation of the aerodynamic parameters, a regression of roughness length and variable Karman constant was also attempted, using a displacement height physically determined as the central height of drag action. Although both the regression methods worked, the former gives larger (smaller) values of displacement height (roughness length) by 20-25 % than the latter. The LES database clearly illustrates the essential difference in bulk flow properties between real urban surfaces and simplified arrays. The vertical profiles of horizontally-averaged momentum flux were influenced by the maximum building height and the standard deviation of building height, as well as conventional geometric parameters such as the average building height, frontal area index, and plane area index. On the basis of these investigations, a new aerodynamic parametrization of roughness length and displacement height in terms of the five geometric parameters described above was empirically proposed. The new parametrizations work well for both real urban morphologies and simplified model geometries.
KW - Aerodynamic parametrization
KW - Displacement height
KW - Large-eddy simulation
KW - Real urban surfaces
KW - Three-dimensional building map
UR - http://www.scopus.com/inward/record.url?scp=84880508388&partnerID=8YFLogxK
U2 - 10.1007/s10546-013-9818-x
DO - 10.1007/s10546-013-9818-x
M3 - Article
AN - SCOPUS:84880508388
VL - 148
SP - 357
EP - 377
JO - Boundary-Layer Meteorology
JF - Boundary-Layer Meteorology
SN - 0006-8314
IS - 2
ER -