Stacey Agnew is at the forefront globally of knowledge about the critical velocity to prevent smoke backlayering from a tunnel fire. In 2019, Michael Beyer and Conrad Stacey started looking at why the NFPA 502 critical velocity equation outputs varied so radically between the 2014 and 2020 editions. Their work identified overly simplistic modelling supported by data falsification as being behind the overpredictions of the 2017 and 2020 formulations. After they wrote to the 502 Committee enclosing their paper (Stacey & Beyer 2020), the 2020 equation was withdrawn by the NFPA.
Having debunked the status quo in critical velocity, and in the process thought hard about the essential physics, Michael and Conrad continued to develop a physically reasonable mixed convection mathematical model of the zero-backlayering ‘equilibrium’. The result is a new paper submitted to Fire Technology in January 2024, proposing a formula which replicates available experimental data, with a simplified version recommended for design of tunnels.
Along the way, the confronting fact of data falsification in a published research paper created tensions within the otherwise collegiate tunnel fire safety community, with the Fire Safety Journal editor still dragging his feet in addressing the problem.
The new paper is submitted to Fire Technology.