Simulation Error for Porous Medium

C72 · October 18, 2021, 12:15

Hello,

I am trying to simulate atmospheric air flow through porous building with a thickness of 1m in the wall and roof sections within my flow domain.

I am modelling this using an implicit unsteady solver with k-omega turbulence. From looking at the Isotropic Porous Media tutorial, I've seen that two separate regions are required for this problem - my 'Fluid' or 'Flow Domain' region created by boolean subtraction of my building model from a larger block, and the 'building' part as an assigned region itself which I define as a porous medium within the flow domain.

I have so far created these two regions, defining 'Flow Domain' as my fluid region, created from the subtraction part, and 'Porous Building' created from my original building CAD part that i subtracted from the block to create the 'Flow Domain' part. I've specified this building region as type 'Porous Region' and entered my desired porous coefficient values in accordance with Darcy's Law.

I've created my desired boundary conditions and also added internal interface boundary conditions as done in the tutorial, created between the internal and external wall surfaces of my 'Porous Building' region and the corresponding surfaces within the 'Flow Domain' region. This made 10 interfaces in total - 2 for each of the 4 walls and roof, internal and external. These are of type 'Internal Interface'.

I then moved on to create my automated mesh as I had done before with my previous model, however, I have only input part 'Flow Domain' into this. I'm not sure if this is the right thing to do but i had an error come up when i tried to input both 'flow domain' and 'Building' parts. Anyway, i completed my meshing as usual and refined the wake spots i wanted to etc.

Now, when i try to run the simulation, I keep getting the following error:

'There is no volume mesh to solve on or no physics continuum assigned to regions. The mesh pipeline likely needs to be run first.'

Is this because i've only input the part for one of my regions into the volume mesh? Or if not, does anyone know how to get around this?

Thanks in advance for any responses,

C72

LuckyTran · October 19, 2021, 04:41

You have more than one problem.

The meshing pipeline likely failed and all meshes were deleted for that error to be shown.

But still, your porous building also needs a mesh. If it doesn't have a mesh... then why are you assigning it a physics continuum?

C72 · October 19, 2021, 10:33

Thanks for the response.

Yeah i did delete original meshes previously so that makes sense thanks.

I also think i am confusing myself slightly. So my flow domain has the building within it because i subtracted my original building part from a larger block. But then the only way that i could see to make this porous was to then assign the building part to regions as well as the flow domain subtracted part, giving two regions but both of them have all of the 'building' part geometries. Do i have duplicates here that i would then need to get rid of?

I've tried to mesh using both 'building' and 'flow domain' as input parts but i keep getting the error that ive attached involving an intersection at the 'Left.Outer' part of the geometry. I'm not sure how to fix this and all 4 sides of the building are identical. I had to move the original building piece slightly below the block before i made the subtraction for flow domain.

LuckyTran · October 19, 2021, 14:32

CADing is CADing. You can see in the parts tree exactly how many parts you have. And yes you CAN have many many many duplicate cad parts. You may or may not want to delete them (because you might need them for manipulating). The CAD process is its own pipeline and you can have many CAD parts at different stages all existing as different parts and part versions.

Ultimately, what is meshed is what part you assign in the automatic mesher. Yes you can still have overlapping parts and you can even generate multiple overlapping meshes in one go!

Now the only one that actually knows what all these different parts are is you–the one doing it! So if you are confused then... unfortunately no one else can help you. I can tell you how to mesh a single part, a box for example. I always have to assume that you CAD'd this part correctly.

October 18, 2021, 12:15	Simulation Error for Porous Medium	#1
C72 New Member Calum Join Date: Sep 2021 Posts: 14 Rep Power: 5	Hello, I am trying to simulate atmospheric air flow through porous building with a thickness of 1m in the wall and roof sections within my flow domain. I am modelling this using an implicit unsteady solver with k-omega turbulence. From looking at the Isotropic Porous Media tutorial, I've seen that two separate regions are required for this problem - my 'Fluid' or 'Flow Domain' region created by boolean subtraction of my building model from a larger block, and the 'building' part as an assigned region itself which I define as a porous medium within the flow domain. I have so far created these two regions, defining 'Flow Domain' as my fluid region, created from the subtraction part, and 'Porous Building' created from my original building CAD part that i subtracted from the block to create the 'Flow Domain' part. I've specified this building region as type 'Porous Region' and entered my desired porous coefficient values in accordance with Darcy's Law. I've created my desired boundary conditions and also added internal interface boundary conditions as done in the tutorial, created between the internal and external wall surfaces of my 'Porous Building' region and the corresponding surfaces within the 'Flow Domain' region. This made 10 interfaces in total - 2 for each of the 4 walls and roof, internal and external. These are of type 'Internal Interface'. I then moved on to create my automated mesh as I had done before with my previous model, however, I have only input part 'Flow Domain' into this. I'm not sure if this is the right thing to do but i had an error come up when i tried to input both 'flow domain' and 'Building' parts. Anyway, i completed my meshing as usual and refined the wake spots i wanted to etc. Now, when i try to run the simulation, I keep getting the following error: 'There is no volume mesh to solve on or no physics continuum assigned to regions. The mesh pipeline likely needs to be run first.' Is this because i've only input the part for one of my regions into the volume mesh? Or if not, does anyone know how to get around this? Thanks in advance for any responses, C72

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October 19, 2021, 04:41		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,761 Rep Power: 66	You have more than one problem. The meshing pipeline likely failed and all meshes were deleted for that error to be shown. But still, your porous building also needs a mesh. If it doesn't have a mesh... then why are you assigning it a physics continuum?

October 19, 2021, 14:32		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,761 Rep Power: 66	CADing is CADing. You can see in the parts tree exactly how many parts you have. And yes you CAN have many many many duplicate cad parts. You may or may not want to delete them (because you might need them for manipulating). The CAD process is its own pipeline and you can have many CAD parts at different stages all existing as different parts and part versions. Ultimately, what is meshed is what part you assign in the automatic mesher. Yes you can still have overlapping parts and you can even generate multiple overlapping meshes in one go! Now the only one that actually knows what all these different parts are is you–the one doing it! So if you are confused then... unfortunately no one else can help you. I can tell you how to mesh a single part, a box for example. I always have to assume that you CAD'd this part correctly.