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Author Topic: aerodynamic versus geometric surface  (Read 997 times)


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aerodynamic versus geometric surface
« on: September 11, 2018, 10:16:37 am »

In our simulations of natural smoke and heat exhaust ventilation, we are regularly confronted to the question what we should indicate in our report as aerodynamic or geometric surface for the exhaust vents on the roof. What can be considered as a reasonable ratio between the surface of the exhaust modeled in FDS and the geometric and aerodynamic surface of an exhaust product. We are in general modelling the roof as a thick obstruction, and the exhaust as a hole in the roof with open boundary conditions over the roof.
What is generally considered to be the link between the size of the exhaust introduced in the FDS model and the aerodynamic surface or geometric surface? I assume that the effect of the "vena contracta" can be regarded as taken into account by an FDS simulation. What mesh size should here be considered?