Analysis of cigarette smoke distribution in a casino

Jan-Hendrik Grobler, CFD Centre, CSIR, South Africa

STAR-CD has recently been used by the CSIR (Council for Scientific and Industrial Research) to analyze the airflow on the main floor of a casino complex to determine the distribution of cigarette smoke particles.

Strict laws aimed at curbing smoking in public venues have recently been promulgated in South Africa. Many businesses had to make significant structural changes to their buildings in order to comply with the new laws, which generally require that designated smoking areas be completely separated from non-smoking areas by means of full height partitions.

The STAR-CD model of the main floor of the casino complex enabled ventilation engineers to investigate the possibility of confining smoke to certain areas with effective ventilation and partial partitions instead of full height partitions which would harm the aesthetical appeal of the venue.

The engineers were also interested in the effectiveness of the ventilation system in removing smoke from smoking areas in the event that they had to be separated with full height partitions. The STAR-CD model was therefore adapted to accommodate such a scenario as well.

The grid presented a modeling challenge due to the many geometric details that had to be captured. The ability of PROSTAR to generate three-dimensional cells by extruding two-dimensional shell cells came in very handy. A floor plan detailing the position of the machines was used to generate a similar picture in PROSTAR consisting of shell cells, via the PATCH command. These cells were then extruded in the vertical direction to form solid cells to represent four different types of machines as well as fluid cells representing the airspace (see figure 1).

The roof detail was also complex, but had a repetitive pattern and the relevant commands in PROSTAR made it possible to generate the complete set of shell cells from one segment. Due to the difference between the roof and floor detail, the two sections were joined by means of an arbitrary coupled interface, situated approximately 4 meters from the floor level. If the two sections could not be joined in this way, it would have been virtually impossible to generate the grid with hexahedral cells alone, and grid development would have taken far longer.

The remaining part of the grid consists of the passage surrounding the main floor and includes several domes. This part of the model was generated using blocks and is shown in figure 2. Figure 2 also shows the location of some of the boundaries, which were automatically applied by running a script of PROSTAR commands.

The final grid consisted ofapproximately 800 000 fluid cells and was used to perform several runs, each with different boundary conditions, representing different ventilation designs. Figure 3 shows one of these solutions and indicates the expected path that smoke particles will take when released by smokers at selected machines.

The model predicted that it would be difficult to contain the cigarette smoke to certain areas without significant changes to the ventilation system. A combination of a modified ventilation system and partitions around the centre section of the main floor was found that made it possible to contain and effectively ventilate the cigarette smoke from that area.