Civil Engineering and Architecture 7(4): 99-119, 2019 http://www.hrpub.org DOI: 10.13189/cea.2019.070402 Numerical Investigation of Three-dimensional Turbulent Wind Flow around Two Square Buildings with Hip Roofs J. Venetis School of Applied Mathematics and Physical Sciences, National Technical University of Athens, Greece Copyright©2019 by authors, all rights reserved. Authors agree that this article remains permanently open access under the terms of the Creative Commons Attribution License 4.0 International License Abstract This computational work aims at studying the three – dimensional turbulent wind flow around two square buildings with pyramid roofs of trivial architectural forms for an arbitrary geographical location. The overall investigation substantially reduces to the fundamental problem of an external three – dimensional turbulent flow field past a mounted obstacle of predefined shape. The novelty of this research is that the independency of the numerical solution for any possible distribution of mesh points was demonstrated in a theoretical manner without the necessity of changing the original grid with simultaneous repetition of the computational process. Keywords Turbulent Flow, Mounted Obstacle, Finite Volume Method, Voronoi Diagram, Delaunay Triangulation 1. Introduction It is well known that the governing differential equations of any fluid flow, laminar or turbulent, can be solved analytically only for a limited number of simple flow cases of little interest to a mechanical, hydraulic or chemical engineer. The difficulty of solving analytically the momentum conservation equations is due to the form of the terms of acceleration of transfer, which unfortunately are non-linear terms. Nonetheless, exact solutions can generally be achieved for problems where the conditions of the acceleration transfer are zero, e.g. Couette flow, Poiseuille flow, flowing into porous media. In most practical problems encountered by an engineer, such as the design of a ventilation system of a building, the differential equations describing the air transport are not linear, so there is no analytical solution of closed form. One has to resort to numerical methods. By means of computational methods, the differential equations characterizing a flow are approximated by algebraic equations describing the characteristic flux sizes, not across the entire flow field but at specific points (meshpoints), all of which synthesize the numerical grid. Numerical equations consist of a system of equations that form the basis of any computational code and the solution of which determines all sizes that characterize a flow, velocity field volumetric flow, Computational methods are generally divided into boundary element methods (BEM) and Domain Discretization methods. The latter are in turn divided into Finite Differences, Finite Element (FEM), (with linear, nonLinear and stochastic elements) and Finite Volume methods. In the meanwhile, during the last four decades, a large amount of valuable research work has proved that air movement in buildings can be predicted in a reliable manner via Domain Discretization methods. Indeed, the related models actually implement the so-called finite-volume and/or finite-element methods for any transported quantity (such as velocity components, temperature and species concentrations) in the flow domain to derive, from the differential equations describing the relevant phenomena, a finite system of algebraic equations. In the sequel, this assembly can be solved on the basis of specific iterative processes to obtain numerical values when user-defined convergence criteria are reached. As long as these results can be considered accurate, i.e. validated versus experimental data, they form a “virtual” airflow field within the building space, representing the so-called “prediction” of the flow field. Thus, CFD can be used for airflow pattern predictions in buildings, in order to design optimum ventilation systems. The current literature signifies that CFD is a very strong tool for predicting air movement in buildings in terms of hydrodynamic and temperature fields, providing plausible results for various ventilation designs, and particularly for choosing among different alternatives. This is an important CITE THIS PAPER [1] J. Venetis , "Numerical Investigation of Three-dimensional Turbulent Wind Flow around Two Square Buildings with Hip Roofs," Civil Engineering and Architecture, Vol. 7, No. 4, pp. 99 - 119, 2019. DOI: 10.13189/cea.2019.070402.