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[Warren Davis]

It would be nice if there was an easier way to model FD solids surrounded by ablative insulation layers. It's difficult to merge nodes since they don't always line up and entering conductors manually can be painful.

[DPBell]

From our discussions, I understand that this request is to have a solid that is embedded in the ablative material with one face exposed to the environment and ablative material surrounding it. I assume that the intent would be to allow the ablative and solid to exchange heat perpendicularly to the flow of heat through the ablative. Unfortunately, this violates one of our primary assumptions regarding ablation: the heat flow is 1D and travels normal to the ablative face.

It is actually a bad idea to attempt to thermally connect the ablative to an object other than the substrate and boundary condition. So your workaround is not advisable.

We can look at this from another perspective and hopefully see that the assumption is justifiable. If heat is transferred from the solid to the ablative, this would increase the recession rate surrounding the solid and then cut off the connection between the solid and the ablative. If the heat transfers from the ablative to the solid, then recession would be slowed locally and the remaining ablative would insulate the solid on the sides. Assuming the solid is more conductive than the ablative, my guess is that the former assumption is more correct.

Now the former possibility is simple to model: you would create a thermal connection from the sides of the solid to the boundary condition that is proportional to the local recession of the ablative. For the latter, you could also have a connection from the BC to the sides of the solid (proportional to the recession), but include some ablative on the face of the solid. Either of these methods would avoid lateral heat transfer within ablative.[/img]