In this episode of fire fundamentals we sit down with Professor Simo Hostikka from Aalto University to cover radiation in fires, both from the angle of physical phenomena and ways to model it. In this episode we cover following topics:

• feel less mysterious, from blackbody basics and role of radiation actually does inside the CFD N-S equation.
• Spectrum and emissivity to real engineering outcomes like heat flux, tenability
• Radiation’s two roles in fire CFD: target heat flux and the gas energy source term
• Emission versus absorption and why Kirchhoff’s law is spectral, not just a single number
• Spectrum intuition using Planck, Wien’s law, and why T to the fourth explodes heat flux
• View factors as a hazard mental model for layers, panels, and distance effects
• Why gases are strongly non-gray while soot often looks smooth and easier to approximate
• How FDS uses the finite angle method, why 104 directions exists, and how updates are staged in time, how to manage spatial and temporal resolution of the radiation
• Ray effect and numerical diffusion, when you can see the error and when you cannot
• Other radiation models such as Monte Carlo, and when they are worth it.
  
  

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