Resistance Material Direction

[Anonymous]

Hello,

I am working on a HVAC duct simulation. I have problem applying the resistance material to a part of the duct and also issues with meshing.

1. I defined a resistance material and tried to apply it normal to the direction of flow but I was able to select the direction only to the flow direction. Not Normal to the direction of flow.

2. I have problems with meshing too when I tried to run the simulation. The model is not meshing properly at resistance material and  the simulation is not running as the solver stops at creating the mesh.

Thanks

[LKania]

Can you zip a sharefile (.cfz) and upload?

[Anonymous]

Hello Lee,

Please check the attached file and I have total 9 outlets.

I was not able to assign the resistance material normal to the direction of flow on top rectagle outlets and I have problem with meshing with radial outlets and radial resistance material.

Thanks

[LKania]

Satish,

I am able to load and mesh your model successfully. What sort of messages are you seeing in the message window leading you to believe that the meshing operation has failed?

[Anonymous]

I suppressed the round features. If you activate them, it won't mesh and
solve.

Thanks

[LKania]

Satish,

  The cylindrical "caps" you had suppressed are improperly mated with the currently meshed portion of the model and a duplicate surface exists in this region. The attached image shows this  The import process sees these surfaces as sufficiently distinct whereas there should be a common/shared surface here; this is the source of the meshing difficulties. If you clean up the assembly and try again, there should be no meshing issues.

  It might be possible to adjust the import coincidence tolerance (the AsmCoinTol flag at model import), but this may involve a little trial and error to identify a tolerance that addresses this issue. 

[Anonymous]

Lee,

OK. I will work on cleaning thoae parts.

Could you help he on assigning Resitance material on the rectangle outlets at the front.

I want to assign the resistance material normal to the flow. Whe I tried to select surfaces, it is showing only in the direction of flow.

Thanks

[LKania]

I'm not in a position to comment on the resistance material settings; perhaps others monitoring this forum can chime in with some advice.

[Royce_adsk]

Hi Satish,

Could you explain why you need to apply the flow direction not normal to the flow?  

What is your goal here? 

Keep in mind, that you can control the 'in-plane' resistances when you edit the resistance material, so you could apply and then adjust based on your intentions.

Thanks,

[Anonymous]

Hello Royce,

What I am trying to do is, air flow in a HAVC duct with filters at the end of air outlets.

Based on the HVAC tutorial you have in the help, I am trying to assign the resistance material for filters with resistance normal to the flow(if I understand correctly based on the tutorial).

Here is the link.

http://help.autodesk.com/view/SCDSE/2014/ENU/?guid=GUID-BC3E47DC-6626-41C6-974F-4D5676FAE066

In the below image(from tutorial), ther is a filter near to inlet to which resitance is applied normal to the direction of flow.

The arrow showing below is not the direction of flow. Flow enters in opposite direction.

In my case, I have filter at the outlet and I want to apply the resitance normal to the flow but I was able to select the resistance in the direction of flow. Flow is coming out as the direction shown below.

My question is, as per your tutorial I need to apply the resistance normal to the direction of flow as explained above. How can I change the direction in my case? If you want to see the model, I attached a zip file above to understand my model.

[Jon.Wilde]

Wouldn't the flow direction just be applied to this top surface? Although in CFD, the flow could travel in either direction along this arrow.

Can I also suggest you extend your outlets to avoid recirculation over them? They should be about 10x the length of the diamater of the pipe - here it is cuboid so just take the short length make the outlets 10x this.

You need to do the same for the inlet, but here its length should be 5x the 'diameter', take the shortest edge again. Ideally we should have better developed flow entering the model.

Also be sure to use Advection Scheme 5 for volumetric resistances (Solve -> Solution Controls -> Advection) or switch to Surface Resistances, seeing as your flow is going to be travelling pretty uniformly over them, saves on worrying about the mesh 🙂

Hope this is useful.

Thanks,

Jon