Analysis and Improvement of Separation Efficiency of Air Curtains in the Built Environment

The term 'plane impinging jet' refers to a high-velocity fluid stream that is ejected from a nozzle, a narrow opening or an orifice, and which impinges on a surface. In the building industry, impinging jets are used in air curtains to separate two environments, subjected to different environmental conditions, without restricting access of people, vehicles or materials to these environments. Air curtains are frequently used at entrance doors in commercial, healthcare and industrial premises to create an aerodynamic barrier for the purpose of thermal comfort, air quality, energy efficiency and fire protection in buildings. The performance of an air curtain is commonly assessed by the parameter known as 'separation efficiency'. The separation efficiency of air curtains can be significantly influenced by a large set of environmental and jet parameters which affect the jet structure and its vortex dynamics, and therefore determine the transport of heat and mass between the environments separated by the air curtain. Because of the many applications of the impinging jet technology, multiple studies have been conducted in the past. However, despite the extensive existing literature and research on impinging jets, there is insufficient specific research on jet and environmental parameters relevant for air-curtain applications, and thus there is a knowledge gap that needs to be addressed for the advancement of the state-of-the-art in air-curtain technology. In order to address the current lack of knowledge on impinging jets, focused on their application in air curtains, and to support the development of new air-curtain technologies, this project comprises the following tasks: 1) Develop a comprehensive set of dedicated experimental data to be used for both an in-depth analysis of the fluid dynamics of turbulent plane impinging jets and for the validation of numerical models of turbulent plane impinging jets / air curtains; 2) Investigate the influence of the most important environmental and jet parameters on the separation efficiency of air curtains; 3) Analyze the effect of the formation of turbulent structures in the air-curtain jet and determine its influence on the separation efficiency of air curtains; 4) Optimize the separation efficiency of air curtains by incorporating favorable passive and active jet-control strategies. This project comprises the use of advanced numerical simulation techniques (i.e., computational fluid dynamics (CFD) based on Reynolds-averaged Navier-Stokes and large eddy simulations) for the parametric and systematic analysis of air curtains under variable operational conditions (i.e., varying jet and environmental parameters) and their subsequent optimization. In addition, numerical simulations are accompanied with wind tunnel and water tank measurements using particle image velocimetry (PIV) for validation purposes and additional fluid dynamics analyses.