Parametric Study of Urban-Like Topographic Statistical Moments Relevant to a Priori Modelling of Bulk Aerodynamic Parameters

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• 作者：Xiaowei Zhu ; G. Valerio Iungo ; Stefano Leonardi…
• 关键词：Aerodynamic drag ; Large ; eddy simulation ; Roughness length ; Urban topography
• 刊名：Boundary-Layer Meteorology
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：162
• 期：2
• 页码：231-253
• 全文大小：
• 刊物类别：Earth and Environmental Science
• 刊物主题：Atmospheric Sciences; Meteorology; Atmospheric Protection/Air Quality Control/Air Pollution;
• 出版者：Springer Netherlands
• ISSN：1573-1472
• 卷排序：162

文摘

For a horizontally homogeneous, neutrally stratified atmospheric boundary layer (ABL), aerodynamic roughness length, \(z_0\), is the effective elevation at which the streamwise component of mean velocity is zero. A priori prediction of \(z_0\) based on topographic attributes remains an open line of inquiry in planetary boundary-layer research. Urban topographies – the topic of this study – exhibit spatial heterogeneities associated with variability of building height, width, and proximity with adjacent buildings; such variability renders a priori, prognostic \(z_0\) models appealing. Here, large-eddy simulation (LES) has been used in an extensive parametric study to characterize the ABL response (and \(z_0\)) to a range of synthetic, urban-like topographies wherein statistical moments of the topography have been systematically varied. Using LES results, we determined the hierarchical influence of topographic moments relevant to setting \(z_0\). We demonstrate that standard deviation and skewness are important, while kurtosis is negligible. This finding is reconciled with a model recently proposed by Flack and Schultz (J Fluids Eng 132:041203-1–041203-10, 2010), who demonstrate that \(z_0\) can be modelled with standard deviation and skewness, and two empirical coefficients (one for each moment). We find that the empirical coefficient related to skewness is not constant, but exhibits a dependence on standard deviation over certain ranges. For idealized, quasi-uniform cubic topographies and for complex, fully random urban-like topographies, we demonstrate strong performance of the generalized Flack and Schultz model against contemporary roughness correlations.