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  • Memorial Tunnel Fire Ventilation Simulations
    the fans The calculated flow through the tunnel was about 10 below the measured value this was acceptable given the simplifications in the modeling and the uncertainty in the experimental set up Fire simulations are often carried out without radiation modelling the heat source associated with the fire is reduced to allow for the heat that is in reality transferred by radiation but the detail of that heat transfer is ignored In this case simulations were carried out both with and without radiation making use of the IMMERSOL model in PHOENICS Comparisons with data at monitoring locations showed that both approaches were able to predict the presence of a back layering region near the ceiling but only in the IMMERSOL case were the values in accordance with experiment This aspect is of crucial relevance a misrepresentation of the back layering phenomenon in flows near the critical conditions could give a completely wrong prediction of the ventilation efficiency in controlling the smoke diffusion The simulations demonstrated the capability of the PHOENICS software to simulate tunnel fires and to predict the observed flow behaviour This provides safety engineers with a powerful tool in the design of ventilation systems that will enhance safety while keeping down costs 2 Technical summary The Memorial Tunnel is a two lane 853m long straight motorway gallery with a medium slope of 3 2 from north to south portal the tunnel has a cross section of 60 4m 2 Various ventilation configurations were used for the experiments but the simulations concentrate on the longitudinal system 15 jet fans were placed inside the tunnel in groups of 3 The jet fans induced an air velocity of 34 2m s and a mass flow rate of 43m 3 s A body fitted coordinate BFC grid was constructed to represent adequately

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_applic/recapps/enea/enea_o1.htm (2016-02-15)
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  • fire1
    a source of mass heat and pollutant smoke The turbulence model used is K Epsilon Figures displaying the geometry Outside view of the building Location of the boiler Outlines of the building geometry Inside view of the building Figures displaying velocity vectors and streamlines Velocity vectors in a vertical cross section Stream line across the building from the boiler to the exit Stream line showing the recirculation at the fourth

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_applic/builfire/fire1.htm (2016-02-15)
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  • BFC grid buoyancy k epsilon model continued The plots show the following Velocity vectors in a plane just downstream of the fire The fire plume passes through this plane towards the top Having risen flow turns out of the plane of the plot and along the roof of the tunnel Temperature contours on the same plane deg K Temperature contours at a plane towards the end of the train Note

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_applic/dgln/cross.htm (2016-02-15)
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  • Annecy-Town-Hall Car Park
    The most dangerous fire location was assumed at the lowest level of the car park and an average heat release rate of 5MW was used The development of the smoke and heat distribution was established by the simulations and the influence of various parameters was investigated Smoke propagation was observed through the central atrium and also up the helical slab through the parking levels The atrium allows rapid transmission of smoke and heat to the upper levels this is not serious as the contact with fresh air causes significant cooling and dilution which keeps conditions safe for evacuation As a result of the flow to the atrium the hot gases only propagate slowly through the parking levels again evacuation is not compromised by this There is though a problem in the atrium where the stairwells can become surrounded by hot fumes It was realised that the most important safety requirement was to ensure the isolation of the stairwells from the atrium while retaining access from the parking levels for evacuation pressurisation of the stairwells is also important to their role as emergency exits The understanding gained from the PHOENICS simulations enabled safety proposals to be put forward The changes required to the design were comparatively minor and can provide fire safety without great expense and without compromising the architecture of the building 2 Technical summary The Annecy Town Hall car park is composed of a helical slab which forms the six parking levels surrounding a central atrium The radius of the atrium is 8 5m as is the width of the slab at the centre of the slab the slope is 2 5 and the total depth is about 20m Ventilation is both natural and mechanical Natural ventilation is provided by the central atrium and by two shafts per level there are also two extraction shafts on each level equipped with fans Exit from the car park is by staircases and elevators The PHOENICS simulations were set up to take account of the whole of the geometry including ventilation systems The most dangerous fire location was assumed at the lowest level of the car park and an average heat release rate of 5MW was used A cylindrical grid was used for the computations with VR objects used to represent the structural components parking levels ventilation ducts staircases vehicles The computational grid was selected after grid refinement studies to obtain well converged stable solutions and sufficient accuracy The grid lines were more finely spaced near the walls and the ventilation ducts where the gradients are the steepest The chosen grid was composed of 430000 cells The simulation was transient and had to take account of the key physical phenomena turbulence buoyancy phenomena generated by the fire heat and smoke release at the fire A k e turbulence model was used in the simulations In view of the importance of buoyancy the k e RNG variation a standard PHOENICS built in option was adopted The calculations were carried out without a model

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_applic/recapps/annecy/annecy.htm (2016-02-15)
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  • in width x 40 in height y and 625 in length z Solved for variables are three velocities pressure temperature and smoke concentration At inlet the longitudinal velocity profile inceases linearly with height and a rectangular sectioned stream of hot smoke enters the remainder being occupied by atmospheric temperature air Buoyancy causes flow in cross section to exhibit vortices Computed results This case shows how the parabolic option can be

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_applic/d_enviro/smorpl.htm (2016-02-15)
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  • Thermal radiation in a compartment fire
    supplying the air for heating and ventilation purposes The fuel is ignited on entry and steady combustion is in progress producing the high temperarture combustion products Their movement is greatly influenced by buoyancy with the salient features as follows Ventilation air is heated by the fire source and rises due to buoyancy and subsequently leaves the room through the top of the door Ambient air enters through the lower portion of the doorway brings in an extra oxidant and is heated up by combustion rises due to buoyancy and leaves the room through the higher part of the door The task is to calculate the temperatures of the internal wall structure and combustion gases along with all related field distributions COMPUTATIONAL DETAILS Conservation equations The independent variables of the problem are the three components of cartesian coordinate system namely X Y and Z The main dependent solved for variables are Pressure P1 Three components of velocity U1 V1 W1 Turbulence energy and its dissipation rate KE EP Gas total enthalpy H1 Gas mixture fraction MIXF and Gas radiosity solid temperature T3 Turbulence and combustion models The K epsilon model KEMODL closed by wall functions is used to calculate the distribution of turbulence energy and its dissipation rate from which the turbulence viscosity is deduced Combustion is treated as a single step irreversible diffusion controlled chemical reaction with a infinitely fast rate between fuel and oxygen The gas composition and its enthalpy are related to the mixture fraction according to the Simple Chemical Reaction Scheme SCRS concept Model of radiative transfer The IMMERSOL model is used to simulate the distribution of T3 within the space filled with combustion gases and solid blocks From the temperature fields the radiant heat fluxes QRX QRY and QRZ W m 2 are calculated and used

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_applic/d_rad/immersol/imm7.htm (2016-02-15)
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  • Fire in a wind-exposed building
    openings and near ceiling slot exposed to the 30 degree external wind It is supposed that a fuel methane leak from the communication system enters the building structure through an internal aperture The fuel is ignited on entry and steady combustion is in progress producing the high temperarture combustion products Their movement is influenced by buoyancy and the air coming in from outside The task is to calculate the temperatures and composition of combustion gases along with all related field distributions COMPUTATIONAL DETAILS Conservation equations The independent variables of the problem are the three components of cartesian coordinate system namely X Y and Z The main dependent solved for variables are Pressure P1 Three components of velocity U1 V1 W1 Turbulence energy and its dissipation rate KE EP Gas total enthalpy H1 and Gas mixture fraction MIXF Turbulence and combustion models The K epsilon model KEMODL closed by wall functions is used to calculate the distribution of turbulence energy and its dissipation rate from which the turbulence viscosity is deduced Combustion is treated as a single step irreversible diffusion controlled chemical reaction with a infinitely fast rate between fuel and oxygen The gas composition and its enthalpy are related to the mixture fraction according to the Simple Chemical Reaction Scheme SCRS concept Properties and auxiliary relations The gas density is computed from the local pressures gas temperatures and local mixture molecular masses The specific enthalpies are related to gas temperatures fuel mass fraction and the heat of combustion THE RESULTS The plots show the distribution of temperatures velocities and other related fields within and outside the building structure Pictures are as follows Building structure geometry Flow streamlines Flow velocity vectors Velocity vectors at the window plane Temperature contours at the window plane Velocity vectors at the ceiling plane Temperature contours

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_applic/d_comb/thrufire/winexp.htm (2016-02-15)
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  • and observed results which were obtained for the case of an isolated rectangular shaped model building it is concluded that the k L turbulence model as well as the standard k e model can give the results with acceptable degree of accuracy Obtained results as concentration fields were used to calculate fields of damage of an intoxication at various meteorological conditions by means of the EMERGENCY code that represents a written in DELPHI 2 application running under WINDOWS 95 The EMERGENCY allows performing the quantitative risk assessment of an influence of various hazardous factor fields e g concentration of toxic gases thermal fields explosion shock waves and other using the probit analysis The PHOENICS result file as well as another file format can be easily adopted as the EMERGENCY input file The EMERGENCY output file has compatible with the PHI file format so user can employ the PHOTON to display the result The pictures are as follows Figure 1 Scheme of the building complex and location of the ammonia vapours source Figure 2 6 m height horizontal wind field south east wind direction wind speed at height 10 m 4 5 m s neutral atmosphere Figure 3 Surface with ammonia vapours concentration of C 0 5 g m 3 2 m height contours of ammonia vapours concentration and some air particle trajectories originating in the south inlet region at height 6 m above ground in 30 min after leakage south wind direction wind speed at height 10 m 4 5 m s neutral atmosphere Figure 4 Vertical contours of ammonia vapours concentration and air particle trajectories passing over the ground source of toxic vapours in 30 min after leakage south east wind direction wind speed at height 10 m 2 5 m s neutral atmosphere Figure 5 EMERGENCY produced damage

    Original URL path: http://www.cham.co.uk/casestudies/misasva/misasva.htm (2016-02-15)
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