With the numbers of airline passengers always increasing, the regulation authorities are more concerned than ever by the possible contamination of air cabins by contagious viruses, such as SARS or H5N1. This is why Purdue University researchers have developed a system that can track a pathogen substance to an area the size of a single seat. The system uses sensors to locate passengers releasing hazardous materials. But more importantly, it uses a mathematical technique, called 'inverse simulation,' which analyzes 'how a material disperses throughout the cabin and then runs the dispersion in reverse to find its origin.' This system could one day alert the pilots in real time -- and even be deployed in office buildings.
The picture above shows how computational fluid dynamics (CFD) have been used to study air distribution in the cabin of a Boeing 767. (Credit: Qingyan Chen, Purdue University). Here is a more detailed caption: "Passengers and crew are packed in a very limited space in commercial aircraft cabin. The air distribution systems play a very important role for the comfort, health, and safety of passengers and crew. The recent experience of SARS transmission on aircrafts has further heightened the need to improve the design of the air distribution systems currently used on airplanes." (link)
This research has been led by Qingyan Chen, a professor of mechanical engineering at Purdue University, and supported by the Air Transportation Center of Excellence for Airliner Cabin Environment Research, established by the Federal Aviation Administration. Here is a link to other Qingyan Chen's recent research activities.
But what exactly is the purpose of this project?
"The goal is to be able to track the source if a person released a biological agent, such as anthrax, or inadvertently released a pathogen such as pandemic flu by sneezing, for example," said Chen.
And how is it possible to reach this goal? The answer is to use "inverse simulation."
The technique analyzes how a material disperses throughout the cabin and then runs the dispersion in reverse to find its origin. Sensors track the airflow pattern and collect data related to factors such as temperature, velocity and concentration of gases and particles in the air. "This is difficult to do, in part because an airline cabin is a pretty large area," Chen said. "The procedure now requires several days of computing time to complete the track, meaning the method could be used only after a contamination occurs."
This research work appears in the June 2007 issue of Indoor Air, a scientific journal published on behalf of the International Society of Indoor Air Quality and Climate (ISIAQ) by Blackwell Publishing, Inc. The paper is entitled "Identification of contaminant sources in enclosed environments by inverse CFD modeling" (Volume 17, Issue 3, Pages 167-177). Here is a link to the abstract and some excerpts from it.
In case contaminants are found in enclosed environments such as aircraft cabins or buildings, it is useful to find the contaminant sources. One method to locate contaminant sources is by inverse computational fluid dynamics (CFD) modeling. As the inverse CFD modeling is ill posed, this paper has proposed to solve a quasi-reversibility (QR) equation for contaminant transport.
The equation improves the numerical stability by replacing the second-order diffusion term with a fourth-order stabilization term in the governing equation of contaminant transport. In addition, a numerical scheme for solving the QR equation in unstructured meshes has been developed. This paper demonstrates how to use the inverse CFD model with the QR equation and numerical scheme to identify gaseous contaminant sources in a two-dimensional aircraft cabin and in a three-dimensional office.
Here is an additional link to the full text of this paper (PDF format, 19 pages, 741 KB). But I don't recommend reading it, except if your math skills are really sharp.
Sources: Emil Venere, Purdue University News, May 22, 2007; and various websites
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