Applying multiple thermal surface conditions -- defaults and direction-based transparency

[obscureed]

I am trying to apply different thermal boundary conditions to the walls of a model, using &MATL and &SURF. For example, the floor in a set of rooms and corridors could be concrete, the interior walls could involve plasterboard, exterior walls could be blockwork, and fire-resistant walls and stair cores could be concrete. In particular, these apply to the boundaries of MESH blocks, except where there are MESH-MESH connections. The only way I can see of doing this is to apply &OBST blocks at these boundaries, and then I have to pay attention to miss out all MESH-MESH connections. Are there any shortcuts to this, for example to change the default SURF_ID (or ideally SURF_ID6), mesh by mesh, or region by region?

Also, I really like the behavior of smokeview where a fluid boundary surface is invisible if the view is into a fluid block, but opaque at the other side, where the transition is from fluid to void. Transparency/opacity varies by view direction, and it works really well to see inside a model. However, as far as I can tell, this applies only to default surfaces. When I apply OBSTs to all the boundary surfaces, I lose this feature -- I have to choose a transparency, and it applies in all view directions. Is there a way to get the directional transparency for a non-default thermal BC?

[Er9y714]

Your first question is not clear to me. Mesh-mesh interfaces are open to flow and solid surfaces cannot be applied unless an obstruction is placed there. Can you explain your situation a little more?

[obscureed]

Sure:
I have a model constructed from multiple adjoining mesh blocks, and I need to apply different thermal boundary conditions to different parts of the model.
I define these thermal BCs using &MATL and &SURF.
Where I apply &OBST blocks, I can specify SURF_ID (or SURF_IDS or SURF_ID6) to these.
Where there is a join between two MESH blocks, I leave it alone, unless I want obstruction there.
The question is about how to apply the various thermal BCs to the remaining fluid boundaries, at the exposed surfaces of MESH blocks, with nothing on the other side of the surface. One way is to apply thin OBST blocks at each of these surfaces -- this is what I am currently doing. (This leads to the second question about visualisation.) It requires me to build up a patchwork of OBSTs, avoiding the MESH/MESH boundaries, and also avoiding all the VENT, OPEN, HVAC etc surfaces. I just wondered whether there is a more efficient way?

For example, it would be convenient to set a default SURF_ID/SURF_IDS/SURF_ID6 for each MESH block -- where the default is understood to apply except for MESH/MESH boundaries, and other user-defined surfaces (including OBST and all the VENT options), in the same way that the global default SURF_ID applies.

I suspect that there is no current alternative way, so I need to apply that patchwork of OBSTs. Currently I define those OBSTs to have finite thickness, both sides of the MESH extreme -- compared to infinitely thin OBSTS at the exact coordinates, this seems safer (though I think that OBSTs will lock onto the desired facets) and does not have any differences in terms of visualisation.

For the sake of being specific, I'll attach an example image below. How would I apply different thermal BCs to the red, cyan and yellow surfaces? (Grey, bright red, pale green, magenta and invisible surfaces are already dealt with.) In the example shown, I have made the OBSTs on two sides of the stairwell opaque and red. OBSTs on the other two sides, nearer to the viewer, are transparent. Therefore the view is much less useful from the opposite direction.

[drjfloyd]

You can use VENT for the exterior boundaries of meshes instead of OBST and Smokeview will look through VENTs on the exterior boundary. For example, in the lower left if those thin red OBST on the boundary were VENT, you would look through into the shaft.

The idea of having SURF_ID(S or 6) as a MESH input is interesting. I can see how it would be useful in cases like yours where different construction types are associated with different meshes.

[obscureed]

That has worked - thanks! One drawback of a VENT is that you can't overlay other VENTs on top of it, so I think I'll end up using OBST for the floor. (I don't mind the floor being opaque in both directions.)