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-   -   Please help!! Patch and Species transport (http://www.cfd-online.com/Forums/fluent/30196-please-help-patch-species-transport.html)

Julie August 21, 2002 11:39

Please help!! Patch and Species transport
 
Dear All,

Sorry for posting so many questions in the forum...But I'm gettin towards the deadlines and Im reallie worried.

I am modelling the spread of a source of gas in a ventilated room (air).

When I want to patch a zone for species transport modelling, in the patch panel i click on the species and there is a box for me to enter a value, but it did not have any units or description of what value it is refering to. Is this value mass fraction? So if my zone is purely of one species, I just enter a value of 1 into the selected species?

Also, if it is mass fraction, and i input the value of 1 in the small volume of zone, how much of the species (in terms of mass e.g. kg or grams) am I actually inputting? Or the only way to measure is by ppm, where ppm= mass fraction of the species x 1000000??

Also, this question is asked in my other thread in the forum, but just in case different pple read this thread, they may have a clue of how to do it:

If I create a new mixture using the species already defined in the database, are the properties of the overall mixture formed automatically calculated and updated by Fluent? Or do we still have to find out the values thru books and input them in ourselves?

Jin-Wook LEE August 21, 2002 20:11

Re: Please help!! Patch and Species transport
 
Yes, that value is mass fraction.

I recommend that you use 'MASS SOURCE' in boundary condition panle.

You can use Fluent's various option in the MATERIAL panle. Fluent's default setting is based on the constant value for the properties at the room temperature.

Sincerely, Jinwook


Julie August 24, 2002 11:18

Re: Please help!! Patch and Species transport
 
Do you mean from the BC of my fluid zone, I could specify "mass source"? But under fluid zone BC, when I turn on the source terms, it is in kg/m^3sec but my source is not constantly emitting mass of ammonia gas in every second.

so I decided to use patch where I will telling fluent that there is a fixed intial amount of source at a certain position.

Also, I have another question which I have posted out recently, wonder if you could help. I need my concentration of ammonia gas in the room to be about 40mg/m^3, and from the volume of my room, I calculated that there should be 0.006272kg of ammonia gas in the room. Hence using the density of ammonia gas, I calculated the volume occupied by this amount of ammonia gas, thus able to patch this volume.

However the conc of ammonia gas is really very small 40mg/m^3 of the room, hence it is 0.00004Kg/m^3 but the plot of conc with time is only up to 4 decimal places, do you by any chance know how to increase the number of decimal places such that my y-axis values will not be all 0.0000. Thanks.

snh September 24, 2012 15:24

Quote:

Originally Posted by Julie
;102280
Dear All,

Sorry for posting so many questions in the forum...But I'm gettin towards the deadlines and Im reallie worried.

I am modelling the spread of a source of gas in a ventilated room (air).

When I want to patch a zone for species transport modelling, in the patch panel i click on the species and there is a box for me to enter a value, but it did not have any units or description of what value it is refering to. Is this value mass fraction? So if my zone is purely of one species, I just enter a value of 1 into the selected species?

Also, if it is mass fraction, and i input the value of 1 in the small volume of zone, how much of the species (in terms of mass e.g. kg or grams) am I actually inputting? Or the only way to measure is by ppm, where ppm= mass fraction of the species x 1000000??

Also, this question is asked in my other thread in the forum, but just in case different pple read this thread, they may have a clue of how to do it:

If I create a new mixture using the species already defined in the database, are the properties of the overall mixture formed automatically calculated and updated by Fluent? Or do we still have to find out the values thru books and input them in ourselves?

Hii

I am facing a similar problem of entering the specific quantity of reactant using the patch option in my simulation. I would like to know how you tackled with the problem. It would be of great help in my project.

shk12345 September 25, 2012 10:55

Quote:

Originally Posted by Julie
;102280
Dear All,

Sorry for posting so many questions in the forum...But I'm gettin towards the deadlines and Im reallie worried.

I am modelling the spread of a source of gas in a ventilated room (air).

When I want to patch a zone for species transport modelling, in the patch panel i click on the species and there is a box for me to enter a value, but it did not have any units or description of what value it is refering to. Is this value mass fraction? So if my zone is purely of one species, I just enter a value of 1 into the selected species?

Also, if it is mass fraction, and i input the value of 1 in the small volume of zone, how much of the species (in terms of mass e.g. kg or grams) am I actually inputting? Or the only way to measure is by ppm, where ppm= mass fraction of the species x 1000000??

Also, this question is asked in my other thread in the forum, but just in case different pple read this thread, they may have a clue of how to do it:

If I create a new mixture using the species already defined in the database, are the properties of the overall mixture formed automatically calculated and updated by Fluent? Or do we still have to find out the values thru books and input them in ourselves?

The species in volume basis and not on mass basis. After patching the required amount check the countor of the species and you can see that in that zone that much volume is there .If it is in ppm level you can convert it in volume using mass and density of that substance and patch it there whatever low the volume may be.
You can check the volume average in the domain of that species there.

Hope that helps
Shk


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