For our fire engineers, one of the key objectives during the early stages of any job is to identify aspects of the design where it will be necessary to develop an alternative approach to that suggested in Approved Document B of the Building Regulations 2010(ADB) or one of the other common design guides, such as BS 9991.
Referred to as an ‘engineered’ approach, this goes beyond the one-size-fits-all methods discussed in ADB and instead considers the unique layout and use of each building to find the most suitable system, without over-specifying.
So, how do fire engineers demonstrate how an engineered approach will affect fire safety in a building, especially as this is generally carried out during the planning and design stages?
For many engineered solutions, particularly those involving smoke ventilation, the short answer is computer modelling, specifically Computational Fluid Dynamic, or CFD, Modelling.
What is CFD?
CFD Modelling is used in a variety of industries, including automotive and aeronautical design, to show the movement of a fluid (in these cases air) over a surface, for instance to show the aerodynamic properties of an object.
A similar approach is taken to fire engineering, with a computer model being created of the building in which the fire safety systems are to be installed. The software will then be used to simulate a fire beginning in the building, and the smoke which this produces. The fluid dynamics, or movement of the smoke and fire over time will also be simulated, taking into account its physical behavior, such as hot air rising, in order to show areas where the smoke is hotter or more dense or where fire may spread more rapidly.
How do we use it?
By highlighting areas with heavy smoke buildup, or common areas/escape routes where smoke accumulates, the software allows our engineers to identify where to provide additional smoke ventilation and other fire safety systems, for instance through the installation of natural or mechanical smoke ventilation systems, pressurisation systems and sprinklers.
The CFD model simulation can then be run once again, factoring in the behaviour of the smoke and fire with these systems activated. This provides an easy reference point, showing the effectiveness of various fire safety systems in different applications, while also allowing properties such as shaft sizes and fan speeds to be adjusted in order to find the best possible system for each application.
What benefits does it provide?
By creating a tailored plan for each project, it’s possible to provide substantial cost and space savings, as this removes the possibility of unnecessary systems being specified.
In addition, CFD models can be used to show that, due to their superior efficiency, the installation of certain systems can allow the extension of compartment (or room) sizes and corridors, providing greater design freedom for designers and architects while also providing more saleable space.
Finally, CFD Modelling is also used to justify these designs to Building Control, with the models created, plus any relevant calculations, being submitted to show that the design is as effective – if not more so – as the suggestions made by ADB.
To learn more about CFD, and to speak to our team of experts, visit: www.fdsconsultuk.com/services/cfd-modelling
