Airflow patterns around obstacles with arched and pitched roofs: Wind tunnel measurements and direct simulation

Abstract Achieving accurate numerical predictions of airflow around buildings is challenging due to the dynamic characteristics of wind. Buildings are usually considered as obstacles to the wind. A time-dependent simulation model has been applied for the prediction of the turbulent airflow around obstacles with arched and pitched roof geometry, under wind tunnel conditions. The numerical model is based on the direct solution of transient Navier–Stokes and continuity equations using the Galerkin finite element method. To verify the reliability of the model an experiment was conducted inside a wind tunnel and the air velocity and turbulent kinetic energy profiles were measured around two small-scale obstacles with an arched-type and a pitched-type roof, respectively. The velocity components and the turbulent kinetic energy values were used to demonstrate a dynamic and statistical analysis of this complex flow. The wind tunnel tests presented good agreement with the numerical simulations with respect to airflow patterns. The different roof geometry of obstacles affected the instantaneous and time-mean averaged parameters of the flow. According to the instantaneous results of the numerical solution, airflow patterns presented fluctuating characteristics mainly downstream of the obstacles. Intense variations were shown in streamlines and velocity components, both at the arched-type and the pitched-type obstacle, starting from the upstream corner of the roof and the top of the roof respectively. The time-dependent simulation of the flow parameters can provide important information on instantaneous fluctuations of the complex flow phenomena around arched-type and pitched-type roof obstacles which cannot be obtained by the time-mean averaged approach.

[1]  Dimitrios Moshou,et al.  Calculated external pressure coefficients on livestock buildings and comparison with Eurocode 1 , 2012 .

[2]  Simon J. Watson,et al.  Estimating the potential yield of small building‐mounted wind turbines , 2007 .

[3]  Peter V. Nielsen,et al.  Original paper: Validation of CFD simulation for ammonia emissions from an aqueous solution , 2011 .

[4]  Jan Carmeliet,et al.  CFD analysis of convective heat transfer at the surfaces of a cube immersed in a turbulent boundary layer , 2010 .

[5]  Iraj Mortazavi,et al.  Vortex simulation of active control strategies for transitional backward-facing step flows , 2009 .

[6]  Tetsuro Tamura,et al.  AIJ guide for numerical prediction of wind loads on buildings , 2006 .

[7]  Tong Yang,et al.  CFD and field testing of a naturally ventilated full-scale building , 2004 .

[8]  Anuradha M. Annaswamy,et al.  Self-sustained oscillations and vortex shedding in backward-facing step flows: Simulation and linear instability analysis , 2004 .

[9]  C. J. Apelt,et al.  Simulation of wind flow around three-dimensional buildings , 1989 .

[10]  Theodore Stathopoulos,et al.  Application of computational fluid dynamics in building performance simulation for the outdoor environment: an overview , 2011 .

[11]  N. Malamataris,et al.  Two-dimensional numerical simulation of vortex shedding and flapping motion of turbulent flow around a rib , 2012 .

[12]  Jing Liu,et al.  Evaluation of various non-linear k–ɛ models for predicting wind flow around an isolated high-rise building within the surface boundary layer , 2012 .

[13]  Yoshihiko Hayashi,et al.  Numerical simulation of velocity field and diffusion field in an urban area , 1990 .

[14]  Y. Tominaga,et al.  Numerical simulation of dispersion around an isolated cubic building: Model evaluation of RANS and LES , 2010 .

[15]  P. Panigrahi,et al.  Turbulent structures and budgets behind permeable ribs , 2008 .

[16]  José Meseguer,et al.  An analysis on the dependence on cross section geometry of galloping stability of two-dimensional bodies having either biconvex or rhomboidal cross sections , 2009 .

[17]  Kemal Hanjalic,et al.  Vortex structure and heat transfer in turbulent flow over a wall-mounted matrix of cubes , 1999 .

[18]  van Taj Twan Hooff,et al.  Computational analysis of the performance of a venturi-shaped roof for natural ventilation : venturi-effect versus wind-blocking effect , 2011 .

[19]  Atila Novoselac,et al.  Cross ventilation with small openings: Measurements in a multi-zone test building , 2012 .

[20]  Guoqiang Zhang,et al.  Effects of airflow and liquid temperature on ammonia mass transfer above an emission surface: experimental study on emission rate. , 2009, Bioresource technology.

[21]  A. El-aziz,et al.  Study of wind effects on different buildings of pitched roofs , 2007 .

[22]  Testing Batchelor’s similarity hypotheses for decaying two-dimensional turbulence , 2010 .

[23]  E. Erturk,et al.  Numerical solutions of 2-D steady incompressible flow over a backward-facing step, Part I: High Reynolds number solutions , 2008 .

[24]  Volker John,et al.  Time‐dependent flow across a step: the slip with friction boundary condition , 2006 .

[25]  Takao Inamura,et al.  Numerical simulation of separated flow transition and heat transfer around a two-dimensional rib , 2007 .

[26]  Baoming Li,et al.  Numerical modelling of temperature variations in a Chinese solar greenhouse , 2009 .

[27]  H. Fernholz,et al.  Manipulation of the reverse-flow region downstream of a fence by spanwise vortices , 2007 .

[28]  Nikolaos A. Malamataris,et al.  Direct simulation of two‐dimensional turbulent flow over a surface‐mounted obstacle , 2007 .

[29]  Bje Bert Blocken,et al.  A venturi-shaped roof for wind-induced natural ventilation of buildings: wind tunnel and CFD evaluation of different design configurations , 2011 .

[30]  Qingyan Chen,et al.  Natural Ventilation in Buildings: Measurement in a Wind Tunnel and Numerical Simulation with Large Eddy Simulation , 2003 .

[31]  Separation behaviour in front of a two-dimensional fence , 2001 .

[32]  H. Sung,et al.  Unsteady separated and reattaching turbulent flow over a two-dimensional square rib , 2008 .

[33]  Xianting Li,et al.  Numerical analysis of outdoor thermal environment around buildings , 2005 .

[34]  Takashi Kurabuchi,et al.  Study on airflow characteristics inside and outside a cross-ventilation model, and ventilation flow rates using wind tunnel experiments , 2001 .

[35]  Mahmood Yaghoubi,et al.  Thermal analysis of vaulted roofs , 2008 .

[36]  Christine M. Hrenya,et al.  Size segregation in rapid, granular flows with continuous size distributions , 2004 .

[37]  Y. Wang,et al.  Estimation of the vortex shedding frequency of a 2-D building using correlation and the POD methods , 2010 .

[38]  Influence of the filtering tools on the analysis of two-dimensional turbulent flows , 2009 .

[39]  Mahmood Yaghoubi,et al.  Thermal behavior of curved roof buildings exposed to solar radiation and wind flow for various orientations , 2008 .

[40]  Da-Wen Sun,et al.  Applications of computational fluid dynamics (CFD) in the modelling and design of ventilation systems in the agricultural industry: a review. , 2007, Bioresource technology.

[41]  G. K. Ntinas,et al.  Numerical simulation of airflow over two successive tunnel greenhouses , 2011 .

[42]  Bje Bert Blocken,et al.  CFD simulation of cross-ventilation for a generic isolated building : impact of computational parameters , 2012 .