Open AccessLES Analysis of the Aerodynamic Surface Properties for Turbulent Flows over Building Arrays with Various Geometries
Author(s) -
Hiromasa Nakayama,
Tetsuya Takemi,
Hiroki Nagai
Publication year - 2011
Publication title -
journal of applied meteorology and climatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.079
H-Index - 134
eISSN - 1558-8432
pISSN - 1558-8424
DOI - 10.1175/2011jamc2567.1
Subject(s) - aerodynamics , roughness length , turbulence , surface finish , surface roughness , large eddy simulation , drag coefficient , range (aeronautics) , drag , standard deviation , environmental science , meteorology , materials science , mechanics , physics , mathematics , wind speed , statistics , wind profile power law , composite material
This paper describes aerodynamic roughness properties for turbulent flows over various building arrays that represent realistic urban surface geometries. First, building morphological characteristics such as roughness density λ f and building height variability V h , defined respectively as the ratio of total frontal area of roughness elements to the total surface area and the ratio of standard deviation in building height to the average building height of the study site, were investigated. Next, large-eddy simulations (LESs) of turbulent flows over building arrays were performed with various surface geometries characterized by a wide range of values for both λ f and V h , based on this building morphological analysis. Third, aerodynamic roughness parameters such as roughness length z 0 and drag coefficientwere evaluated for the central Tokyo area from the values of z 0 and V h using the LES results. The values of z 0 andas a function of both λ f and V h were comparable to those found in earlier studies. The values of z 0 andevaluated by a conventional method using only λ f were underestimated, particularly for densely built-up areas. This indicates that the present approach to estimating aerodynamic roughness parameters, taking account of both roughness density and building height variability, is more appropriate than conventional approaches when applied to actual urban areas. The roughness aerodynamic parameters as a function of λ f and V h obtained from the LES results will be useful in incorporating urban effects into weather forecasting models.