Jiru T.E.,Mechanical and Materials Engineering |
Bitsuamlak G.T.,Florida International University
International Journal of Ventilation | Year: 2010
This paper reviews the application of CFD for designing and parametric studies of wind-induced natural ventilation. The approaches employed in such applications of CFD are whole-domain and domain-decoupled CFD modelling. The domain-decoupled technique separately analyses the external airflow fields outside and internal flows inside a building. In the whole-domain approach, the outdoor and indoor airflow is modelled simultaneously and within the same computational domain. The review showed that the whole-domain approach has been more popular than the domain-decoupled approach, and with efficient computing algorithms, grid generation techniques and advances in hardware technology, can overcome the computational overhead it incurs during application. CFD has also allowed the concept of stream tube and the local dynamic similarity model (LDSM) to be used in practice. These concepts have helped in the fundamental understanding of wind-driven natural ventilation and in distinguishing flow through large openings from that of "cracks". An important and practical approach for natural ventilation design and analysis is the integration of CFD with other simulation programs such as Building Simulation (BS) and Geographic Information Systems (GIS). Apparently, CFD is increasing its importance in sustainable building design and it is expected that more complex naturally ventilated buildings will be designed and analysed as CFD techniques continue to improve.
Kube C.M.,Mechanical and Materials Engineering |
Turner J.A.,Mechanical and Materials Engineering
Journal of Elasticity | Year: 2015
In this article, expressions are derived for the Voigt, Reuss, and Hill estimates of the third-order elastic constants for polycrystals with either cubic or hexagonal crystal symmetry and orthorhombic physical symmetry. General forms of the fourth- and sixth-rank elastic stiffness and compliance tensors for crystal and physical symmetries are given. Explicit expressions are reduced from these tensors for the case of polycrystals exhibiting orthorhombic sample symmetry with either cubic or hexagonal crystallites. The estimated third-order elastic constants of the textured polycrystal are obtained in terms of second- and third-order single-crystal elastic constants and orientation distribution coefficients (ODCs), which are used to account for anisotropic physical symmetry. The acoustic nonlinearity parameter, (Formula presented.), is defined through combinations of the second- and third-order Voigt, Reuss, and Hill estimates of the elastic constants for a textured polycrystal. The model predicts that (Formula presented.) is dependent on the type of averaging scheme used and the texture-defining ODCs. The model is quantitatively evaluated for polycrystalline iron, aluminum, and titanium using second- and third-order single-crystal elastic constants and experimentally measured ODCs. The interrelation between (Formula presented.) and polycrystalline anisotropy offers potential for techniques associated with quantitative texture analysis. © 2015 Springer Science+Business Media Dordrecht