SMARTFIRE FUTURE DEVELOPMENTS
Warehouse fire simulation (with ceiling vents) simulated using the unstructured mesh version of SMARTFIRE.
Unstructured tetrahedral mesh elements (Pyramids), has been used in the unstructured mesh version of SMARTFIRE to simulate the effects of fire within aircraft. The mesh was generated using a third party mesh generator.
Simulation of fire within an aircraft cockpit using an unstructured mesh. Depicted is a VR representation of the aircraft with a temperature isosurface. Some notable features in the geometry include the pilots chair and ducting in the above ceiling region. Visualised using MayaVi.
Decomposing an unstructured mesh of the MD11 scenario for simulation in the Parallel version of SMARTFIRE.
The researchers in FSEG are currently working on a number of approaches to handle the difficulties of unstructured geometries. One prototype approach uses a Google Sketch-Up building as a starting point and demonstrates how the geometry can be manipulated and filtered to create a compatible SMARTFIRE simulation scenario.
An "unstructured" house geometry in Google Sketch-Up.
The house geometry has been saved and then meshed in the Harpoon Meshing System.
Another meshed house geometry is configured as a scenario and then run in SMARTFIRE CFD Engine.
Completed simulation results visualised in DataViewer.
Fires typically generate a number of narcotic and toxic gasses. Sometimes these products of combustion have complex behaviour which means that the dispersion and transport of the products (within the flow domain) is non-trivial. For HCL, the gas reacts with certain wall surfaces to effectively remove it from the gaseous phase. This needs to be accurately modelled in order to predict the gaseous quantities of HCL which can be convected into other regions of the geometry and so cause harm to occupants.
Galloway and Hirschlerís deposition model, typically used in zone models, is modified and applied to a field fire model in order to predict the decay of HCL within fire enclosures. The modified model still uses empirical formulas, but the HCL deposition mechanisms have been simplified from three processes to two processes (see Figure below).
The effect of HCL flux to the wall boundary, on the time to reach equilibrium (i.e. for the wall surface HCL density to rise and reach the equilibrium) is addressed in this modified model. The new model correctly predicts the absorption of HCL by wall surfaces with the SMARTFIRE Fire Field Model.
SMARTFIRE modelling HCL absorption showing surface map when using PMMA walls
SMARTFIRE modelling HCL absorption showing surface map when using Concrete walls
In very large geometries
(e.g. airport terminals, underground stations) there may
be regions of the geometry which will only experience
minor fire impact or which may be of little direct
relevance to the solution outcome. In such cases
it may be desirable to use a coupled field-zone
modelling approach to simplify the calculations and
reduce the computational overhead associated with
simulations based on a pure field modelling
approach. The aim of this project is to develop
such a coupled field-zone modelling approach using SMARTFIRE
as the core field modelling engine. An
advanced prototype Hybrid CFD/Zone computational engine
has been developed and it has demonstrated very good
solution consistency whilst providing excellent
computational time savings as compared to using full CFD
simulation. Current research and development activities
are directed at providing a suitable scenario
configuration for the Hybrid model.
The current SMARTFIRE to EXODUS data linkage relies on the creation of appropriate hazard sub-volumes within both models. These hazard sub-volumes might be very large by comparison to the control volumes used within the CFD model. In such instances there might be considerable local inaccuracy (due to data averaging) within the sub-volumes, particularly when the hazard sub-volumes are close to the fire sources or where there are complex/significant flows.
An enhanced SMARTFIRE
to EXODUS data linkage is currently being
developed which attempts to preserve more of the
computational accuracy of the CFD modelling. The
evacuation software will have access to a more
spatially-resolved database of results data for each
time step which it can interrogate to determine more
representative hazard values. Although the spatial
resolution of the hazard export could be as small as a
single evacuation node space, this would typically
result in exporting rather more hazard data than is
Sprinkler and Water Mist models developed by FSEG for the EU funded FIREDASS project have been ported to the SMARTFIRE software. Ongoing research is aimed at investigating droplet interaction with the gas environment, droplet interaction with burning surfaces and fire suppression effects. Although Sprinkler and Water Mist system modelling is now available, Fire Suppression and enhanced coupling between sub-models will be made available to users in future releases of the software after thorough validation has been performed.
Investigating the effect of sprinkler head design for Water Mist modelling within SMARTFIRE Research Version.
Research undertaken by the SMARTFIRE development team into the development of solid fuel combustion models based on the pyrolysis process, and including charring effects, is being incorporated into the SMARTFIRE environment.This research is using an embedded mesh for the fine scale modelling of the thermal conduction and decomposition into the solid fueld surface.
Research by the SMARTFIRE developers continues into the application and development of toxic gas generation models based on the Local Equivalence Ratio (LER) concept. The LER based toxicity model has been fully implemented in SMARTFIRE and is currently being extended to model other gaseous species.
The model was first used to predict the CO, CO2 and Optical Density of smoke for a combined CFD analysis and evacuation model performed in SMARTFIRE and EXODUS.
Ratio φ, is defined as the fuel mass flow rate divided
by the air mass flow rate normalized by the
stoichiometric ratio of fuel to air. φ is used to
describe the vitiated condition within a fire room
Correlation between species yields and φ. Experimental
data support that the yields of combustion products are
correlated with φ. A Correlation between species yields
and φ have been derived from experimental data for
various building materials. This yield correlation is
used to predict the generation of combustion products in
room fires. Preliminary numerical tests showed that this
approach was very promising.
The model performed very well in the Cable fire scenario with accurate prediction of the product species.
SMARTFIRE modelling CO mass fractions from a cable fire
Graph showing predicted and experimental CO2 volume fractions for a small room fire test scenario.
A range of new
features for SMARTFIRE v5.0 (and beyond)
are currently in development.
The current list of features under development and testing, includes:
More information concerning these features will be provided here in the near future.
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