Local-scale forcing effects on wind flows in an urban environment: Impact of geometrical simplifications

Wind flow in urban areas is strongly affected by the urban geometry. In the last decades most of the geometries used to reproduce urban areas, both in wind-tunnel (WT) tests and Computational Fluid Dynamics (CFD) simulations, were simplified compared to reality in order to limit experimental effort and computational costs. However, it is unclear to which extent these geometrical simplifications can affect the reliability of the numerical and experimental results. The goal of this paper is to quantify the deviations caused by geometrical simplifications. The case under study is the district of Livorno city (Italy), called “Quartiere La Venezia”. The 3D steady Reynolds-averaged Navier-Stokes (RANS) simulations are solved, first for a single block of the district, then for the whole district. The CFD simulations are validated with WT tests at scale 1:300. Comparisons are made of mean wind velocity profiles between WT tests and CFD simulations, and the agreement is quantified using four validation metrics (FB, NMSE, R and FAC1.3). The results show that the most detailed geometry provides improved performance, especially for wind direction α = 240° (22% difference in terms of FAC1.3).

[1]  H Hamid Montazeri,et al.  CFD evaluation of new second-skin facade concept for wind comfort on building balconies : case-study for the Park Tower in Antwerp , 2013 .

[2]  T. Shih,et al.  A new k-ϵ eddy viscosity model for high reynolds number turbulent flows , 1995 .

[3]  Michael Schatzmann,et al.  Quality assurance and improvement of micro-scale meteorological models , 2011 .

[4]  George C. Efthimiou,et al.  CFD-RANS model validation of turbulent flow in a semi-idealized urban canopy , 2012 .

[5]  Brent C. Hedquist,et al.  Flow, turbulence, and pollutant dispersion in urban atmospheresa) , 2010 .

[6]  S. Patankar.  Numerical Heat Transfer and Fluid Flow , 2018, Lecture Notes in Mechanical Engineering.

[7]  C. Baker.  Wind engineering—Past, present and future , 2007 .

[8]  Bje Bert Blocken,et al.  Computational Fluid Dynamics for urban physics: Importance, scales, possibilities, limitations and ten tips and tricks towards accurate and reliable simulations , 2015 .

[9]  Robert N. Meroney,et al.  Ten questions concerning hybrid computational/physical model simulation of wind flow in the built environment , 2016 .

[10]  Andrea Freda,et al.  Wind tunnel measurements of the urban boundary layer development over a historical district in Italy , 2017 .

[11]  S. Hanna,et al.  Air quality model performance evaluation , 2004 .

[12]  Bert Blocken,et al.  CFD simulation for pedestrian wind comfort and wind safety in urban areas: General decision framework and case study for the Eindhoven University campus , 2012, Environ. Model. Softw..

[13]  T. Shih,et al.  A New K-epsilon Eddy Viscosity Model for High Reynolds Number Turbulent Flows: Model Development and Validation , 1994 .

[14]  Bje Bert Blocken,et al.  Quality assessment of Large-Eddy Simulation of wind flow around a high-rise building : validation and solution verification , 2013 .

[15]  Robert N. Meroney,et al.  Concentration and flow distributions in urban street canyons: wind tunnel and computational data , 2003 .

[16]  Gianluca Iaccarino,et al.  Quantifying inflow and RANS turbulence model form uncertainties for wind engineering flows , 2015 .

[17]  J. Fung,et al.  Sensitivity of inflow boundary conditions on downstream wind and turbulence profiles through building obstacles using a CFD approach , 2013 .

[18]  Stephen E. Belcher,et al.  A canopy model of mean winds through urban areas , 2004 .

[19]  B. Launder,et al.  The numerical computation of turbulent flows , 1990 .

[20]  Jörg Franke,et al.  Recommendations of the COST action C14 on the use of CFD in predicting pedestrian wind environment , 2006 .

[21]  Alan Robins,et al.  Influence of urban morphology on air flow over building arrays , 2015 .

[22]  Theodore Stathopoulos,et al.  Computational wind engineering: Past achievements and future challenges , 1997 .

[23]  Bert Blocken,et al.  Coupled urban wind flow and indoor natural ventilation modelling on a high-resolution grid: A case study for the Amsterdam ArenA stadium , 2010, Environ. Model. Softw..

[24]  S. Murakami,et al.  COMPARISON OF VARIOUS TURBULENCE MODELS APPLIED TO A BLUFF BODY , 1993 .

[25]  P. Bradshaw,et al.  Momentum transfer in boundary layers , 1977 .

[26]  Joel H. Ferziger,et al.  Computational methods for fluid dynamics , 1996 .

[27]  Bert Blocken,et al.  50 years of Computational Wind Engineering: Past, present and future , 2014 .

[28]  Bje Bert Blocken,et al.  Pedestrian wind comfort around buildings : comparison of wind comfort criteria based on whole-flow field data for a complex case study , 2013 .

[29]  Aya Hagishima,et al.  Analysis of airflow over building arrays for assessment of urban wind environment , 2013 .

[30]  Fernando Porté-Agel,et al.  Adjustment of Turbulent Boundary-Layer Flow to Idealized Urban Surfaces: A Large-Eddy Simulation Study , 2015, Boundary-Layer Meteorology.

[31]  Zheng-Tong Xie,et al.  LES and RANS for Turbulent Flow over Arrays of Wall-Mounted Obstacles , 2006 .

[32]  M. Bossard,et al.  CORINE land cover technical guide - Addendum 2000 , 2000 .

[33]  T. Stathopoulos,et al.  CFD simulation of the atmospheric boundary layer: wall function problems , 2007 .

[34]  S. Murakami,et al.  Comparison of various revised k–ε models and LES applied to flow around a high-rise building model with 1:1:2 shape placed within the surface boundary layer , 2008 .

[35]  C. Gorlé,et al.  Quantifying inflow uncertainties for CFD simulations of the flow in downtown Oklahoma City , 2014 .

[36]  Bje Bert Blocken,et al.  Pedestrian-level wind conditions around buildings: Review of wind-tunnel and CFD techniques and their accuracy for wind comfort assessment , 2016 .

[37]  H. Fernando.  Fluid Dynamics of Urban Atmospheres in Complex Terrain , 2010 .

[38]  Gianluca Iaccarino,et al.  Modeling of structural uncertainties in Reynolds-averaged Navier-Stokes closures , 2013 .

[39]  Janet F. Barlow,et al.  The wind that shakes the buildings: wind engineering from a boundary layer meteorology perspective , 2013 .

[40]  O. Coceal,et al.  Large-Eddy Simulation of Flows over Random Urban-like Obstacles , 2008 .

[41]  T. Trucano,et al.  Verification, Validation, and Predictive Capability in Computational Engineering and Physics , 2004 .

[42]  Andrea Freda,et al.  Numerical and experimental methods to investigate the behaviour of vertical-axis wind turbines with stators , 2015 .

[43]  Yoshihide Tominaga,et al.  AIJ guidelines for practical applications of CFD to pedestrian wind environment around buildings , 2008 .

[44]  Yoshihide Tominaga,et al.  CFD Simulation of Near-Field Pollutant Dispersion in the Urban Environment: A Review of Current Modeling Techniques , 2013 .

[45]  Shuzo Murakami.  Computational wind engineering , 1990 .

[46]  Nicolas G. Wright,et al.  On the use of the k–ε model in commercial CFD software to model the neutral atmospheric boundary layer , 2007 .

[47]  R. Britter,et al.  FLOW AND DISPERSION IN URBAN AREAS , 2003 .

[48]  Bert Blocken,et al.  CFD evaluation of wind speed conditions in passages between parallel buildings : effect of wall-function roughness modifications for the atmospheric boundary layer flow , 2007 .

[49]  Giovanni Solari,et al.  The wind forecast for safety management of port areas , 2012 .

[50]  Yoshihide Tominaga,et al.  Ten Questions Concerning Modeling of Near-Field Pollutant Dispersion in the Built Environment. , 2016 .