The Importance Of CFD Modelling

In essence, CFD Modelling (Computational Fluid Dynamics) is used to demonstrate the performance of the mechanical extract systems that we install.

CFD modelling is a form of modelling that is used to predict the behaviour of smoke in a fire condition. A model of the area in question is produced within the simulation software and a fire is simulated within this area, the position of the lobby vent is added to the model along with the required extract rate. A timeline is created and various criteria are observed at key points along the timeline and then verified against the agreed required values to ensure the safety of all occupants (including the fire-fighters) at all times.

Within building regulations (approved Doc B) and BS 9991, there are certain criteria that permit the use of a code-compliant natural ventilation system. One such criteria is travel distance from the flat door to the stairwell, but this distance can be varied if the premises are sprinklered.

However there are instances when these code-compliant travel distances are exceeded or the dimensions for a natural shaft are not present on site, and, as such, a code-complaint system is not permitted as the variables are outside the constraints provided by the code. In these instances, either a re-design is required or a mechanical system to the same or a higher performance to the code complaint approach is required.

Although commonly used in high-rise residential buildings, mechanical smoke extraction systems are not a code-compliant approach, and as such their use should be justified to demonstrate that they provide adequate levels of safety in comparison with their natural code-compliant counterparts.

It’s because of the variables above that, when specifying an extract system, a CFD modelling service is highly recommended as a vital part of demonstrating the performance of it. LYFE offer this, either as part of a full turnkey package or as a standalone item, if required.

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