Contaminant Removal By Ventilation
 

Using OF-1.5 I would like to simulate the removal of contaminant by means of ventilation (forced convection). The first idea (approach) is to model the flow of air + additional scalar equation for contaminant (here, the scalar will be used as a "tracer" for contaminant concentration). I have already (and successfully) included additional scalar equation in the OF-1.5 solver and set the "initial field" for contaminant (similar to the "DamBreak" tutorial case) for the simple flow in a straight channel...
Now, I would like to move to the next step (figuratively presented in attachment), which involves the following:

• The ventilator is placed inside the fluid domain (for example in a room) - I have tried to do this with blockMesh utility, but I am having problems with definition of internal region as well as "internal walls" (walls that bound the ventilator). How can I overcome this issue (define an internal region with two walls so the "wall boundary conditions" are taken into account)?
• For the "ventilator region" I would like to add an extra explicit source term (known pressure drop) to the momentum equation - I think this is possible with "timeActivatedExplicitSource.C", but due to my lack of OF experience I do not know exactly what has to be done... Can someone help me, please?
• Instead of the contaminant "initial filed" I would like to add the explicit source term to the scalar transport equation and this surce term would be "switched on & off" at predifined times (e.g. scalar source is active only in a certain region for a certain period of time). Again, I think this is possible with "timeActivatedExplicitSource.C", but for the same reason (lack of experience with OF) I kindly ask you for your assistance...

Your help, tips and ... is highly appreciated,
Primoz.

Hi Primoz,

maybe the attached solver helps. It works for 1.6.x is mainly work smoke distributions with no testing ... yet :-) Hope this helps a bit and would be nice to see yours running...

Fabian

Hi Fabian,

thanks for the solver! But at the moment I am facing "conceptual" problems (see my previous post), i.e.:

• how to create a mesh with "internal" region (ventilator)
• how to model additional explicit source term in momentum equation (pressure drop caused by ventilator)
• how to model explicit source term in equation for contaminant (at the first approach I would like to model it with scalar equation - it can be used as a tracer for contaminant concentration)

I think that last two "problems" can be resolved with "timeActivatedExplicitSource.C", but (again) my lack of experience with OpenFoam is responsible for my "cry for help" :), while for resolving the first problem I do not have any idea at the moment :(!

If you (or anybody else) can help how to overcome these issues I am more than thankfull! I think that implememtation of the correct solver for this case (standard solver with some modiciations if neccessary) is just the matter of approach (academic or industrial) - my current oppinion is that removal of contaminat is mostly governed by the forced convection... Of course, influence of natural convetction can be an upgrade of this (first) step!

With best wishes,
Primoz.

Hi,

you should take a look at the solver. The definition of a volume source region is done using dictionaries see attached case.

Fabian

this is a very interesting problem to me, i'd like to hear how you go if you can solve it!

it would suit the study of fires with smoke and chemical spills indoors and how much work a fan might need to do to return the air to a breathable ratio...?

Fabian,

thanks again! Now I am getting the point for sources in a volume region!

I will try the proposed approach and will keep you posted with results.

Cheers,
Primoz.

Hi Kurt,

thanks for showing interest on this problem. Indeed, this aims to model different scenarios where ventilation system (type, number and placement of ventilators) is used to avoid "human damage".
If (or better said when) I will have progress with this subject, I will keep you informed...

Regards,
Primoz.

P.S.: if you (or anybody else) have some articles (or other open literature) on this subject I will be extremely thankful if you can send them to me!

Hi Fabian,

I tried to follow "your recipe" (regarding the explicit source terms), but unfortunately something is not working... To be honest, it is my low level of experience with OpenFoam-1.5 that is responsible for that.

In a first approach I am using "turbFoam" which was modified with inclusion of additional scalar equation for "smoke" - so far so good :). But when I try to define "explicit source term for smoke (which is scalar)"...:mad:

Can you (or anybody else), please, see the attached case and help me with a definition of an explicit source term! Currently I am using the setFields utility for initial values of scalar, but I would like to do this via source terms...

Thanks in advance,
Primoz.

Hi Ternik,
how are you doing with your problem?
Actually i have the same kind of problem ventillation with a smoke source and i was wondering if it is possible to use a buoyant solver. Do you think this could work out?

Regards Fabian

Hi Fabian,

at the moment "this problem" is on stand-by!!! About the buoyant solver - it depends what you would like to "capture" with numerical modelling. In my first approach I am looking to be able to model this by solving additional transport scalar equation (for smoke)! I have done this, but as a next step I would need (or to be able):

• prescribe "smoke" concentration via "time&place" dependent source term (in scalar equation) - and my lack of OF experience is "guilty" for not resolving this approach!

When I will make any progress, I will keep you posted!

Cheers,
Primoz.

Hello,
I think timeActivatedExplicitCellSource is something that could help you, I'm trying to solve a similar problem and I found this at src/finiteVolume/cfdTools/general/fieldSources/, it writes:
Creates a cell set source that is activated at a given time, and remains
active for a specified duration. The source value is either in specific
(XX/m3) or absolute (XX) units.

My only problem is that I haven't found any notes or tutorials on how to use that, I will post if I manage, I hope you find it interesting.