Mechanical Engineering

Impinging jets are encountered in ventilation systems and many other industrial applications. Their flows are three-dimensional, time-dependent, and turbulent. These jets can generate a high level of noise and often present a source of discomfort in closed areas. In order to reduce and control such mechanisms, one should investigate the flow dynamics that generate the acoustic field. The purpose of this study is to investigate the flow dynamics and, more specifically, the coherent structures involved in the acoustic generation of these jets. Model reduction techniques are commonly used to study the underlying mechanisms by decomposing the flow into coherent structures. The dynamic mode decomposition (DMD) is an equation-free method that relies only on the system’s data taken either through experiments or through numerical simulations. In this paper, the DMD technique is applied, and the spatial modes and their frequencies are presented. The temporal content of the DMD’s modes is the...

Ventilating electrical rooms with intense heat emission sources is imperative to prevent workers' injury and damage to equipment. This paper investigates by means of computational fluid dynamics (CFD) the performance of seven proposed ventilation schemes for a multi-zone transformer room of an indoor substation in Beirut city. To this end, an indoor multi-zone substation with four transformers was simulated using ANSYS/Fluent 15.0 with different proposed ventilation schemes. The location of inlet louvers was fix, while the positions of four exhaust outlets were changed throughout the CFD simulations to determine the best-case scenario providing the lowest levels of temperatures in the operating zone and in the vicinity of transformers. The analysis showed that the cooling effect improves as the elevation of the exhaust fans decreases. The obtained results can be used to make some recommendations for design and optimization of similar ventilation projects of indoor transformer rooms.