Fire Simulation

1
Fire Simulation

• José L. Torero
• BRE/Edinburgh Fire Research Centre
• The University of Edinburgh

2
Different Models

• Zone Models
• Field Models
• RANS
• LES

3
Zone Models

• Resolve energy and mass exchange between room
  size control volumes
• Do not resolve fluid mechanics or heat transfer
• Strong Assumptions

4
Field Models

• Resolve thousands (or millions) of small control
  volumes
• Solve heat transfer and fluid mechanics
• For fire applications it is necessary to
  introduce a turbulence model
• RANS
• LES

5
Field Models - RANS

• Time averaged solution to equations of motion
• Limited when solving short time scale transient
  or fluctuating processes
• Some assumptions and tuneable parameters

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Field Models - RANS

• Solves transient equations of motion
• Very computer intensive unless coarse grid is
  used
• Some assumptions and tuneable parameters

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Limitations

• Zone Models Baseline computations
• Accuracy limited by the assumptions
• Large part of physics is lost
• Field Models High Resolution
• Include most of necessary physics
• Adequate accuracy
• Time intensive not suitable for super real time
  computations

8
The FireGrid Solution

• Computations coupled with sensor input
• Field Models Initialize for short periods the
  computations
• Simple functions (i.e. polynomials) used to
  reproduce the details of flow and temperature
  gradients
• yC1xnC2xn-1C3xn-2.
• Functions generated by initialization
  computations (y)
• Constants defined by sensor feedback (Cn)
• Constant sensor feedback until constants converge
• Super real time without loosing details