Hello,
my basic intention was to get a temperature distribution inside a system. I wanted to use the molar velocity for determining the distribution, but I encountered some characteristics which I couldn’t figure it out. So I made this small example, see attachment (unfortunately, pdf wasn’t allowed). Test_Tube.zip (103.3 KB)
How is the molar velocity calculated, by selecting a face with the “Detail” button and adding a texture?
Why do I see an increase of the velocity (slide 3), higher velocity at the outlet compared to the inlet by constant temperature (see slide 2) ?
On silde 5 I would expact and decrease of the velocity from the inlet to the outlet, face #42 ok, face #44 nearly have the wall temperature speed?
Silde 6 I see an constant decrease of velocity by constant temperature, why is that?
Hello Thomas, I have allowed pdf extension, thank you for reporting.
The average molar speed is calculated differently for the facet details window and the textures. For textures, it is an estimate, as I tried to emphasize in the dropdown menu:
(The underlying reason is that textures internally do not record the velocity of every hit, which would add a lot of memory overhead for a realtively rarely used feature)
Textures estimate the avg. molecular speed assuming isotropy, which is true in many geometries, but isn’t next to the sticking=1 exit of your tube (you can visualize this by direction textures):
Your speeds are overestimated as the dominant particle flow direction is perpendicular to your test facets.
To get the actual mol. speeds, divide the facet to smaller cells with the split or explode commands, and either use Facet Details (which calculates the true velocity) or use the Particle Logger (which generates a list of all hits on the facet).
I verified and the velocity doesn’t change in case 1 (mono-temp test tube):
Exploding selected facet works the first time, exploding them a second time for refining the facet, an error occurs “All selected facets must have a mesh with boudary correction enabled”. I coundn’t find a check box or button for this.
Textured facets have a mesh.
The error means that you try to explode an untextured facet.
Explode converts texture cells to facets.
I’ll remove the part of the error message with the “boundary correction”, that function isn’t shown anymore.
