[yow]

I set up two geometries, one with a solid wire and fluid around the wire (a) and one with only the fluid (b).

(a) has wall BCs for the fluid and solid shadow, both at 2000K (temperature thermal condition).
(b) has wall BC at 2000K (temperature thermal condition).

Otherwise, both have the same setup. The sizes of the flowfields are slightly different but should be irrelevant for this situation.

Yet, the thermal boundary layer (?) for (b) is much thicker than (a). Why is that? Is it possible to make these match?

(a) temperature field (sliver at the bottom): http://imgur.com/Dy6fhto
(b) temperature field: http://imgur.com/Rkbt1Qh

[LuckyTran]

Originally Posted by yow

(a) has wall BCs for the fluid and solid shadow, both at 2000K (temperature thermal condition).

This is no longer a coupled wall because you've fixed it's temperature. Hence, (a) and (b) should be exactly same because you are now comparing a constant temperature wall with a constant temperature wall.

I really can't much sense of your pictures. Where the heck is the wire?

Also, why are the top, right, & bottom boundaries at a temperature of 2000K?

[yow]

Thank you for your reply LuckyTran. Only the bottom is at 2000K for both. I guess the top and right are just outlined in red; their temperature is 300K (just checked). The thermal "boundary layer" of (a) is so thin it looks the same but it's 2000K.

[yow]

Found the difference; I accidentally used "scalable wall function" in my viscous model which made the thermal BL much thinner, probably b/c it was scaling my already refined wall mesh?