Computational Fluid Dynamics is the most powerful tool in the fire engineer's arsenal. Understanding its applications and limitations is essential for competent practice.. What Is CFD Modelling? Computational Fluid Dynamics (CFD) uses numerical methods to solve the Navier Stokes equations governing fluid flow, heat transfer, and combustion. In fire engineering, CFD predicts smoke movement, temperature distribution, and visibility in complex geometries. Primary Software Fire Dynamics Simulator (FDS): Developed by NIST (US National Institute of Standards and Technology) Open source and freely available Industry standard for fire engineering CFD Large Eddy Simulation (LES) turbulence model Companion visualisation tool: Smokeview Other tools: ANSYS Fluent — commercial CFD with fire modelling capabilities SMARTFIRE — developed by University of Greenwich OpenFOAM — open source general purpose CFD Common Applications 1. Smoke ventilation design — validate natural or mechanical smoke control systems 2. Atrium design — demonstrate smoke layer height above occupied levels 3. Car park ventilation — impulse fan design validation 4. Tunnel ventilation — smoke movement and tenability in tunnels 5. External fire spread — radiation from external flames to adjacent buildings 6. Performance based design — demonstrate equivalence to prescriptive requirements Key Input Parameters Heat Release Rate (HRR) — the most critical input; defines the fire size Grid resolution — typically D /10 to D /16 for adequate resolution Boundary conditions — wall materials, openings, ventilation conditions Soot yield — determines visibility predictions Simulation duration — must exceed evacuation time Limitations and Pitfalls 1. Garbage in, garbage out — results are only as good as inputs 2. Grid sensitivity — always perform grid sensitivity analysis 3. Steady state fires — real fires are transient; steady state assumptions may be non conservative 4. Validation — results should be compared against experimental data where possible 5. Competence — CFD should only be performed by engineers with specific training and experience Reporting Requirements BS 7974 requires CFD reports to include: Software version and validation references All input parameters and justification Grid sensitivity analysis results Clear presentation of tenability results Limitations and assumptions For CFD modelling services, contact Magnus Opifex. Magnus Opifex SEVEN LTD — UK's Leading Fire Safety & Fire Engineering Consultancy 🌐 magnus opifex.co.uk 📞 +44 7486 691724 ✉️ office@magnus opifex.co.uk Founders: Nicoleta Vasile, Baroness of Brattleby — CEO, Lawyer and Barrister, Legal & Administrative Director Alina — Technical Director & Expert Fire Engineer (BEng) Head Office: Ealing Cross, 85 Uxbridge Road, London W5 5BW Magnus Opifex SEVEN LTD delivers engineering led fire engineering, fire risk assessments, CFD modelling, and building safety consultancy across the United Kingdom and internationally. With over 20 years of combined experience and a UK portfolio spanning healthcare, residential and infrastructure, we bring truly engineered solutions with a personal touch. © 2026 Magnus Opifex SEVEN LTD. All rights reserved.