Modelling a fire in a tunnel

In this video clip, Dr Mike Spearpoint from the University of Canterbury talks about using computational modelling to predict fire behaviour – what might happen if a truck caught fire in a tunnel?

Points of interest

• What are some of the variables that would need to be incorporated into the model? • What does the model allow the scientists to do? • Why are scientists concerned with fires in tunnels?

Transcript

DR MIKE SPEARPOINT The model that Mun Kit created was to look at the design of a tunnel in Singapore, in this case, in terms of the fire design. If we are designing a tunnel, we might want to be concerned about, if a fire occurs, how do we allow the motorists to evacuate safely? And one way to do this is to install basically a large fan into the tunnel so that we can blow the smoke away from the people trying to evacuate, so they can get out safely. But of course, in designing and specifying this fan, we need to know how big the fire is.

And if you look at a tunnel, there’s all sorts of vehicles that drive down a tunnel – there’s trucks, there’s cars – and so we don't necessarily know exactly what might catch fire. If we are looking at trucks, then they carry different types of products that burn differently.

So to enable the designer to look at getting these ‘what if?’ scenarios – what if this type of truck catches fire? – we use the model to do our design, our predictions, so that we know what is an appropriate fan to put into this tunnel.

The model would allow you to look at how big, how intense the fire has got, and that would then allow you to look at the temperatures that might occur in the tunnel. It would look at the amount of smoke that is generated by the fire. Often, we will find in tunnels, that the fire might develop quicker than the vehicles can escape, so vehicles upstream of a vehicle on fire, yes, can probably get out, but if you have got vehicles behind the truck that is on fire, of course, they might be stuck. And people might not be aware that something is on fire, so they might sit in their car and wait and see what is happening, and by the time they realise that there is a fire, the fire may have got too big for them to escape. So they either can't drive out – the vehicle can't escape because there is no oxygen for the engine of the vehicle to keep going – or if they try and get out of the vehicle, then they are going to be overtaken by the effects of the fire. And that has happened in a number of actual real fires historically.

There’s talk about having a tunnel in Auckland. If that proposal goes ahead, then we are going to have to look at the fire safety of that particular tunnel.

Acknowledgements: DC Slebert Iralil West Dr Mun Kit Cheong LTA, Singapore