Learning Forum

[Meyzeeh]

Hi Everyone

Can I ask how you would add a species source in the near wall cells if the shape of the geometry were not simple enough to use hex, cylinder, or sphere to create a cell register? I'm trying to model a problem where the walls of a complex tunnel geometry are a species source and there is air ventilation. 

[Rob]

Have a look at boundary registers. Otherwise you may need to create fluid regions at the geometry stage. 

[Meyzeeh]

Thank you very much. I will try both methods.

[Meyzeeh]

Hi Rob

I was able to create the boundary register along with an if statement that activates the source in that region however during initialization fluent loads seemingly forever without giving errors do you perhaps know what might be causing this and how I can fix it? please help.

[Rob]

Check RAM usage. Otherwise initialisation usually works or fails relatively quickly. Which initialisation option are you using?

[Meyzeeh]

I have 16GB RAM and only about 50% is used by the time I get to initialization. I've tried both the standard and hybrid the same thing happens. The strange thing is that I am able to create the boundary register and it's usable for other things for example if I separate it to create a new cell zone but it's not usable with the if statement. 

[Meyzeeh]

Can you kindly try using it (boundary register) on your side with a simple if statement that introduces a species source on any simple geometry I just want to see if you will get the same initialization problem?

[Rob]

Why are you using an IF statement? 

[Meyzeeh]

I created the boundary register and then used an if statement to activate the species source only in the boundary register created. The if statement checks if I'm in the boundary register and then returns a value of 1 and activates the source else it returns 0. This usually works with a region register so I thought it will work with a boundary register.

[Meyzeeh]

The boundary register I was creating was one cell distance away from the walls.

[Rob]

Ah, if you're patching you can just pick the register and patch that. No need for anything "clever" with IF statements and the like. Make sure you deselect the fluid regions too! 

[Meyzeeh]

Hi Rob

Ah, I see, and thank you very much for your quick responses, I tried patching but I have run into some problems. The first one is that under patching all the variables (Pressure, Temperature, etc) in the value field have corresponding units except for the variable thoron which is the species source I want to add in the boundary register. This makes me think the value field for thoron corresponds to mass fraction whereas I want to input the source term in kg/m^3s^1 how can fix this? Secondly after patching the value how do you make it a continuous constant source throughout the simulation and not just a source at the beginning of the simulation that eventually dies off?

[Rob]

Ah, I think we've confused each other.  For a source you'll need to split the mesh Domain>Zones>Separate and then add the species (and mass) to that region.  To add an initial amout of species you use patch. 

Too many questions..... 

[Meyzeeh]

Thank you very much, Rob. I will try that. I am very sorry for having so many questions ?.

[Rob]

Not just you.... ;)  :)  You're welcome. I like questions that are asked to learn: questions from not bothering to look/read/think not so much.