Thunderhead Engineering Forum

Public Forum => PyroSim => Topic started by: M Hod on November 03, 2011, 06:09:47 am

Title: Gas Dispersion
Post by: M Hod on November 03, 2011, 06:09:47 am
I know it is possible to model gas dispersions in FDS as i have read a vairety of articles on this topic. I cannot however find anything relating to how to model it using pyrosim, is it possible to do and if so where can i find instructions on how to do so.

Title: Re: Gas Dispersion
Post by: Charlie Thornton on November 03, 2011, 01:00:44 pm
We do not have an example problem or tutorial specific to gas dispersion. What FDS input parameters are unique to gas dispersion problems? (e.g. Is there an example FDS input file?)
Title: Re: Gas Dispersion
Post by: M Hod on November 04, 2011, 03:25:56 am
not that i could find. i was just wondering if it was possible to input the parameters for a particular type of gas to be dispersed and not just air for which there is a tutorial.

Title: Re: Gas Dispersion
Post by: Charlie Thornton on November 04, 2011, 08:30:08 am
I think what you're after is "extra species". They allow you to introduce non-reactive gaseous species into the domain. You can use FDS's 23 pre-defined species (e.g. water vapor, CO, N, Toluene), or you can define your own. Once you've added some extra species to the simulation, you can define an INIT region with certain mass fractions of your species or just blow it in with a supply SURF and a VENT.

To add extra species to your model: on the Model menu, click Edit Extra Species.

EDIT: I should add that you can them track extra species using isosurfaces, slice planes, and gas-phase devices.
Title: Re: Gas Dispersion Simulation
Post by: Nikolaos Kapellas on February 08, 2020, 11:16:58 am
Hello there,
My name is Nikolaos Kapellas and i am currently doing my dissertation which is a safety assessment on Reliquefaction systems on LNG carriers.
More specifically, i would like to ask you how am i able to simulate a gas dispersion of methane leaking from a reliquefaction plant i have imported from Autocad?
Furthermore, i can assure you that i have understood how to do a fire simulation on a room via the PyroSim Example Guide and the Pyrosim Manual. The only way i saw simulating a gas dispersion of methane was to supply it with a vent and an open vent, but i spotted that i can also add species and reactions. finally when i am doing the simulation with the vent i am not getting any Heat Release Rate Results only Q Radiation.
Please help me,
Kind Regards,
Nikolaos Kapellas, 4th year Marine Engineering Student at the University of Strathclyde, Glasgow
Title: Re: Gas Dispersion
Post by: Dave McGill on April 11, 2020, 02:27:23 pm
Hi Nikolaos,

I assume you want to model just the dispersion, and not any subsequent combustion.

as Charlie mentioned above.

1- add methane as a species
2- create a vent that discharges methane at a given rate (kg/s)
3- add slice files or spot measuring devices to track the [methane]
4- specify methane as the species to be tracked instead of smoke ( Simulation Parameters -> Output -> Smoke Quantity -> [Species: METHANE] Mass Fraction)
5- When viewing the methane cloud in Results Viewer you can change it's colour to something other than black, so it won't be mistaken for smoke.

Title: Re: Gas Dispersion
Post by: ropheka93 on June 12, 2020, 02:10:58 am
Thank you for the information that is very useful.