Numerical models development for unidirectional air flow diffusers with lobed and circular orifices

¹ CAMBI Research Center, Technical University of Civil Engineering Bucharest, 021414, Bucharest, Romania
² Technical University of Civil Engineering Bucharest, Faculty of Building Services, 021414, Bucharest, Romania
³ Technical University of Cluj-Napoca, Department of Mechanical Engineering, 400020, Cluj-Napoca, Romania

^* Corresponding author: ilinca.nastase@gmail.com

Abstract

In order to achieve more realistic boundary conditions on the inlet of a ventilation system it is necessary to study the influences of the air diffuser orifices geometry on the airflow distribution in the enclosure. Integrating these orifices directly in a real scale air diffuser for a numerical study will result in a huge computational grid which will translate in huge computational resources and a much larger calculation time. The solution, in this case, was the numerical simulation of the airflow through small parts of the studied air diffuser. Later, the numerical results will be implemented as boundary conditions in the unidirectional diffuser of a numerical simulation that represents a real scale operating room (OR). In the current study two diffusers with different orifices were studied, one having circular („O”) and the other one lobbed („+”) orifices. The initial numerical model had 25 orifices on the diffuser, but because of the very large numerical grid resulted for the initial meshes (>35 million tetrahedral cells), a solution with only 4 orifices was chosen for this study. A mesh independency study was made for these two types of air diffusers. The numerical studies were made using RANS method, with SST k-ω turbulence model in steady state conditions. The numerical results obtained with the first step models showed very good agreement with the PIV stereoscopic experimental measurements.