Jet fan arrangement in tunnel

[deepak paudel]

Dear All,

I aim to design jet fans arrangements for a tunnel.

I have smoke spreading model for natural ventilation. 

For forced ventilation the issues are:

1. The grid resolution: The tunnel is curved and also has height difference along the length. 0.5 m grid was already computationally expensive. To include jet fan of diameter 0.8 m and length 3 m would require much finer mesh. The number of fans is around 24. This would be computationally difficult. 

2. Manually place fans and then vents for such curved geometry would be also time consuming. 

May I ask for any advice on this issue ? Would it be possible to impose flow conditions and not model jet fans instead ? Would it be possible to estimate fan arrangements based on natural ventilation smoke spreading information ?

I would appreciate any advice. Thank you in advance.

[Kevin McGrattan]

If your grid resolution is very coarse, I suggest another method besides FDS. You could try commercial CFD software like FLUENT that will provide body-fitted coordinates, and then just run a "steady-state" calculation to assess the flow pattern. But this is still going to be expensive. Maybe just try a 1-D model. I do not know of one in particular, but I do see simple empirical correlations in the literature. This is like a pipe flow calculation with pressure gains and losses.

[deepak paudel]

Thank you Kevin, I try work on this empirical correlations similar to pipe flow !