Fluids

Fluids

Flame propagation in railway tunnel

    • riteshnw
      Subscriber

      Hello all.


      I want to do the simulation for flame propagation inside the railway tunnel.


      I have drawn the geometry, but now I don't know how to proceed with meshing and other thing.


      Please help me out.


      This is my first time to deal with fire propagation inside the system.


      Thank you in advance.

    • DrAmine
      Ansys Employee

      Do you want to model burn out propagation (propagation of products of combustion) or you want to include combustion in your analysis. If it is your first time I would rather make some training and tutorials. 

    • riteshnw
      Subscriber

      I am trying with some online tutorials.


      I want to include combustion in my analysis for the emergency purpose in case of ventilation system in the tunnels.


       


      Best regards,


      Ritesh

    • DrAmine
      Ansys Employee
      Flame propagation can be done with premixed model if reactants are mixed on entry into fluid domain.
    • riteshnw
      Subscriber

      Thank you Amine.


      I will try with the premixed model.


      There is also a big fan and there is sudden fire generation inside the tunnel.


      What will you suggest me to see the fire propagation in presence of air from the fan? How can I proceed?


      Till now I tried the simulations in fluid flow (Fluent) using k- epsilon model but I am not able to see any fire propagation.

    • DrAmine
      Ansys Employee

      Adding momentum flux to model the fan effect. 


      Without combustion model like premixed model you won't see any propagation.

    • riteshnw
      Subscriber

      I will tried adding non-premixed model but I couldn't see the result.


      I will try once again with premixed model.


      Thank you.

    • DrAmine
      Ansys Employee

      It is not Lotto: you should not try all models. How is fuel and oxidizer feed into the tunnel. Fire can be modeled either as fire source by just adding heat into the volume or via combustion model. With combustion model it all depends how fuel and air are feed into the tunnel. For fire prorogation we usually use premixed model assuming all reactants are mixed on entrance and we want to track the flame propagation (discontinuity of burnt/unburnt components). Cheaper will be via Eddy Dissipation Model and assuming for fire efficiency and where the fuel source is added into air filled domain (in your case tunnel).

    • riteshnw
      Subscriber

      In my case, it is an accidental fire at one selected location.


      So it means I have to use premixed combustion. Correct?


       


      Ritesh

    • DrAmine
      Ansys Employee

      You can even use Eddy Breakup Model. Flame propagation with Premixed Model is expensive. Does it mean that in your case that the reacatants are mixed at that location and the fire starts?


      Please have a look into this report on fire in tunnel using EBU: https://rib.msb.se/Filer/pdf/22988.pdf

    • riteshnw
      Subscriber

      Thank you.


      I will have a look and will try the simulation.


       


      Best regards,


      Ritesh

    • DrAmine
      Ansys Employee

      Good Luck!

    • riteshnw
      Subscriber

      Hi Amine,


      I tried my model using premixed combustion model.


      But, it shows the error as "floating point exception" when |I am trying transient simulation.


      When I do steady simulation for 5000 iterations, the solution does not get converged.


      I want to see the fire and smoke propagation inside the tunnel  and when there is fire.


      How can I model this?


      I have fire source of 20 MW. the dimension of the fire source is 1 X 1 X 1 m3 located at the distance of 10 m from the fan of 2 m diameters in the tunnel section of 100 m long and 7 m width and height.


      Thank you.

    • DrAmine
      Ansys Employee

      What about using what  I have already suggested: Please have a look into this report on fire in tunnel using EBU: https://rib.msb.se/Filer/pdf/22988.pdf


       


      As ANSYS Staff I cannot provide any other hints or look into your case.

    • riteshnw
      Subscriber

      I had a look in the report. But, I have not yet tried due to some technical problems.


      I will try and will let you know.


      Thank you.


      Best regards,


      Ritesh

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