[gustavosimiema]

Hi,

anybody knows one way to put one specific coating in a model? I want to simulate the drag in a model without coating and another one with coating. And then see how was the improvement due to the coating.

[fresty]

HI..
I guess that would really depend on what would be the consequences or effects of coating.. by what I understand from your question, if you intend to visualize the aerodynamic effects (only aerodynamic drag) then I believe surface roughness parameter would be enough to model it..
if the coating has certain absorption functionality then porous medium could be used in conjunction.. however if there are thermal properties to be observed that would make it a bit further tricky..

[gustavosimiema]

Thank you to your reply.
But where can I set the roughness Parameter in Fluent?
To make it easier the understanding, if my model is a ball. I can run both simulations (with roughness and without) with the same model? Just changing the roughness Parameter?

[fresty]

from what i can recall it should be in the momentum tab of the wall BC you have defined for the model.. should be something like roughness height and roughness constant.. you may need to do some research on the standard roughness selection for you model..
Yes exactly, individual simulations with and without the roughness could be run with the same model..

[gustavosimiema]

Your Memory is good, the roughness is in the momentum from Wall BC

But is freezed, I cannot enable it to set the Parameters. Do you know what is missing?

(please see attach)

[fresty]

You would need turbulence flow model to be able to simulate surface roughness.

[gustavosimiema]

Hi,

If I have a geometrie, for example a airplane wing (NACA0012), with a structured coating. Please see the attachment. I know the height of this structures (200µm). How can I set it on Fluent? There are just roughness height and roughness constant to fill in.

Roughness height would be 200µm? And what would be roughness constant?

My objective is to perform a simulation with a smooth surface and then with this structured coating and compare the drag coefficient.

Can anyone give me some hints?

Thanks

[devesh.baghel]

Hi,

I hope, below link may help

http://www.cfd-online.com/Forums/flu...rection-y.html

http://www.cfd-online.com/Forums/flu...nt-height.html


Regards

[gustavosimiema]

Thank you for your help... But unfurtunately the doubt still exists... I already knew these two links... ..

if you have any hint about my questions would be great...

thanks and Best regards

[gustavosimiema]

Anyone know how to take into consideration the roughness geometry in the simulation?

[gustavosimiema]

How to mesh this triangular geometry knowing it is very small? In the order of Microns....

[devesh.baghel]

Hi,

Do you really want to mesh surface roughness height into your model ? I guess not; that's why need to define roughness height and roughness constant by considering near wall mesh along with required y+.

Please take some reference value and cross check the simulation results are how far from expectations.


Regards

[gustavosimiema]

Hi,

Actually I modeled the structured surface in the top of my model. And I´m having problems to generate the mesh. (See then model in attach).
I already have the results of the simulation without this structured surface. Now I would like to run another simulation with the same parameters but now with this structurated surface in the top of my model and compare the results. This triangular structure has 100 micrometers height.


Do you have any hint?

Regards

[gustavosimiema]

I don´t know if it´s a problem to generate the hole model in a CAD software (Ex. Inventor) without any assembly. Because as I did that, without assembly, I cannot select just the triangular structures and apply a mesh sizing at them...
Is there a better way to treat that?

[gustavosimiema]

I forgot to attach the geometry ....

[fresty]

Hi..Been a while..
It is quite something that you're trying to do here, as it is hard for me to imagine the reason why you would need an exact model of roughness pattern.. random roughness would probably be a better evaluation criteria than a structured one in my opinion keeping in view the micron coating would only have a certain level of regularity.. just trying to say that the detailed approach here seems a bit overwhelming considering your comments & discussion.. Nevertheless, if i understood correctly, you may need to try creating assembly with your main body as one part and triangular roughness arrays as another, all just to select them separately to mesh.. you may need to specify the element size/ method for these micron level triangles in order to achieve a mesh if at all..

[gustavosimiema]

Thank you for your suggestion. I have one question, I created a farfield in Design Modeler, than used boolean (subtract) so I have the countours of the triangular structure. How to proceed?

Thanks

[gustavosimiema]

Is there a special approach for this case?

[fresty]

I don't think there would be a special approach.. the problem lies at meshing these micron order shapes. It would be difficult because the base of these triangular structures are now (of course always will be) part of the other body if you perform a single boolean operation. Either construct the geometries & apply boolean operation separately so in essence you would have two domains bonded. This would allow you to deal with the coating & other body separately however to form a compatible & coherent mesh between these two flow domains is a challenge. Nevertheless, I would just give a detailed & thorough time to try this way and mesh.

[gustavosimiema]

Thank you...

Look in the attach.. this is the type of error I´m facing right now...
"ran out of memory". Do you know why this message appears?

I will try to apply boolean operation separately...