HT3D - Ramp functionality

[FDS-seerup]

Hey FDS community

I am currently exploring the cababilities of the 3D heat conduction solver, and have been running into an issue.

When defining the BC's for at 3D problem, one needs to define the FRONT and BACK -side conditions, in respect to the surface orientation of the object. - What if i want to control the temperature of these surfaces by a ramp?

I have a more complex model where i am not getting what i expect.

I have tried troubleshooting the complex model by modifying the ht3d_pile example, se attached:

`
&SURF ID='HOT', TMP_FRONT=100, RAMP_T='temp', COLOR='RED', HT3D=T, CELL_SIZE=0.01 /
&SURF ID='COLD', TMP_BACK=100., RAMP_TMP_BACK='temp' HEAT_TRANSFER_COEFFICIENT=0, COLOR='BLUE', HT3D=T, CELL_SIZE=0.01 /
&SURF ID='SIDE', HEAT_TRANSFER_COEFFICIENT=0, COLOR='GRAY', HT3D=T, CELL_SIZE=0.01 /

&RAMP ID='temp', T=0, F=0.2 /
&RAMP ID='temp', T=1000, F=1 /
`

I expect ithe surface to start at 20 degrees ramping to 100 by the end. However i see some wierd results.

The temperature inside the object (by looking at the temp slice) seems to be jumping from one value to another bewteen each solution step.

Am I doing something wrong, or is it not possible to have these BC's?

ht3d_pile_ramp.txt

[mcgratta]

I'll take a look.

[mcgratta]

First, make sure you are running the latest release version of FDS (or a recent nightly build). We are moving away from these "BACK" boundary conditions except in cases of 1-D heat transfer into a solid with no exposed back side. Now, in any case, 1-D or 3-D, where the back side of the obstruction is within the computational domain, you need only use "FRONT" BCs and apply those SURF lines to the appropriate surface. Thus, in your case, use TMP_FRONT on both SURF lines that are applied to the left and right of the obstructions.

As for the flickering in Smokeview of the slice image --- Smokeview can only show an average temperature within the gas phase cells that are embedded in the obstruction. Thus, you cannot see the detailed temperature profile in depth with Smokeview. Use the PROF line that you have, but add another without the FORMAT parameter to see transient profiles. This indicates the actual temperatures being computed.