A numerical-experimental investigation on the aerodynamic performance of CAARC building models with geometric modiﬁcations G.W. Alminhana * , A.L. Braun, A.M. Loredo-Souza Graduate Program in Civil Engineering (PPGEC), Universidade Federal do Rio Grande do Sul (UFRGS), Av. Osvaldo Aranha, 99 – 3  ﬂoor, Porto Alegre, RS, CEP: 90035- 190, Brazil ARTICLE INFO Keywords: Wind engineering Building aerodynamics Wind tunnel Finite element method (FEM) Large eddy simulation (LES) ABSTRACT This paper presents the results of a numerical-experimental investigation carried out with the purpose to evaluate the aerodynamic performance of CAARC tall building models with different cross-section conﬁgurations. A nu- merical model based on the Taylor-Galerkin two-step scheme and the Finite Element Method is adopted. Tur- bulence is described using LES and a synthetic inﬂow turbulence generator. Experimental tests were performed at the Prof. Joaquim Blessmann Boundary Layer Wind Tunnel considering CAARC tall building models with cross- section modiﬁcations based on chamfered and recessed corners. Some of the wind tunnel predictions obtained here are compared with results obtained from the numerical model proposed in this work, where two and three- dimensional meshes are utilized. Comparisons are also performed considering results obtained from other authors in similar studies. From the present investigation, it was observed that the wind action on tall buildings is signiﬁcantly inﬂuenced by the geometric conﬁguration of the building corners, which may lead to important reductions in the aerodynamic forces. Through a direct comparison of results between numerical and experi- mental simulation, we can see that both reach a convergence of results, thus indicating the potential of use of CFD in the modern aerodynamic investigation of buildings. 1. Introduction The CAARC standard tall building model is an experimental building prototype presenting a simple hexahedral geometry with right-angle corners, which has been widely utilized to calibrate experimental methodologies in wind tunnel tests. Nevertheless, it is well known that certain geometric conﬁgurations of building corners can improve the aerodynamic performance of tall buildings by reducing the magnitude of drag and lift forces acting on the building surface. Hence, shape opti- mization is a major topic in building aerodynamics, where the shape of the cross-section plays an important role. In this sense, a numerical- experimental investigation is proposed in this work in order to eval- uate the aerodynamic behavior of tall building models based on the CAARC geometry with corner modiﬁcations. One of the ﬁrst studies dedicated to wind action on the CAARC building model is due to Wardlaw and Moss (1970), where extensive experimental tests were performed. Later, Melbourne (1980) compared predictions obtained from six different wind tunnel devices to evaluate the reliability of the corresponding experimental data. Whitbread (1975) obtained the aerodynamic coefﬁcients for the CAARC building model using experimental tests in a wind tunnel and Obasaju (1992) determined experimentally the overturning moments and forces referring to a CAARC model considering different incidence angles and different boundary layer proﬁles. The action of natural winds on the CAARC building model was analyzed by authors such as Tang and Kwok (2004), Chen and Letchford (2004) and Balendra et al. (2005), who also inves- tigated winds under extreme conditions. The inﬂuence of geometric conﬁguration over the aerodynamic efﬁciency of tall buildings was pointed out by Baker (2007) and Xie (2014). In the ﬁeld of aerodynamic optimization of buildings, one can observe that signiﬁcant improvements can be obtained by simply modifying the cross-section conﬁguration slightly. In this sense, it is well known that the shape of the building corners has noticeable inﬂuence on the magnitude of aerodynamic forces acting on the building surface. Davenport (1971) is one of the ﬁrst authors to investigate aspects of aerodynamic optimi- zation applied to buildings, where different geometric conﬁgurations were analyzed. He concluded that buildings with circular cross-section behave better in terms of aerodynamic efﬁciency, followed by build- ings with rectangular shape with modiﬁed corners. Effects of the corner shape over the ﬂow ﬁeld around building models were also studied by * Corresponding author. E-mail addresses: guilherme.alminhana@ufrgs.br (G.W. Alminhana), alexandre.braun@ufrgs.br (A.L. Braun), acir@ufrgs.br (A.M. Loredo-Souza). Contents lists available at ScienceDirect Journal of Wind Engineering & Industrial Aerodynamics journal homepage: www.elsevier.com/locate/jweia https://doi.org/10.1016/j.jweia.2018.07.001 Received 18 September 2017; Received in revised form 13 March 2018; Accepted 1 July 2018 0167-6105/© 2018 Elsevier Ltd. All rights reserved. Journal of Wind Engineering & Industrial Aerodynamics 180 (2018) 34–48