CFD Analysis of the Behavior of Airborne Allergens in Carpeted and Uncarpeted Dwellings

Abstract

There is considerable concern today over indoor air quality (IAQ). The factors that influence IAQ may be numerous, and there is considerable research aimed at quantifying these factors. This research is of particular interest to industries that manufacture products used in residential and commercial dwellings, such as the carpet industry. With respect to carpet, there are various opinions about its role in IAQ, but little quantitative data. Much of the quantitative data that does exist either ignores or makes crude assumptions about the influence of fluid dynamics on the experimental observations. In this paper we discuss our use of Computational Fluid Dynamics (CFD) to model the transient behavior of airborne particles in dwellings with and without carpeted floors to quantify the impact of floor covering on IAQ. In particular, we discuss the theoretical considerations that are required to construct an accurate and practical CFD model that captures the correct fluid and particle dynamics, and present and summarize CFD predictions that account for the effects of HVAC systems, room geometry and virtual objects, such as people moving about the dwelling. In addition to getting the fluid and particle dynamics correct, there are two additional aspects of this problem that will be discussed. First, in order to draw reasonable conclusions about IAQ, a large number of simulations are required to capture the wide range of realistic dwelling conditions of interest. In order to perform these simulations in a timely manner, the process of building and meshing the geometry, specifying all relevant room conditions, conducting the simulation and interrogating the results has been automated by constructing a Digital Expert for the problem, wherein the user can automatically complete these tasks with little CFD expertise and no intervention. Second, it is essential to communicate the results of these simulations to lay audiences — the wide range of people interested in IAQ, including school boards, politicians and other government officials. We have developed a means of generating “Hollywood grade” animations that are more realistic in appearance than conventional CFD animations, and consequently more appealing and more readily understandable, but that reflect the correct fluid and particle dynamics. We believe that the integration of CFD with realistic animation capability will see greater applicability as our society becomes increasingly dependent on technology and decreasingly technically literate.