Discussion Forum

Hi

it depends in which context, a heat flux is defined w.r.t. a "normal vector" so a negative heat flux is onlyshowing that the flow direction is opposite to the normal vector direction.

Sometimes you get negative temperatures and bizarre heat fluxes in time dependent solver cases when the mesh density is not respecting the heat diffusivity and time step criteria (check Nagis comments on other treads on the Forum)

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Good luck
Ivar

Thank you so much for your guidance :).
but still confused which direction is positive.is it mean along positive axis ?

So to avoid negative value can I simultaneously take the total normal heat flux of different values as absolute.It gives me positive value but do not know is it correct or not?



Looking forward for your cooperation.

Regards.
Tassawar

Hi

you need to get COMSOL to show you how it has defined the directions, you can get that (have forgotten exactly how/where in old 3.5 ;) but its there.
For 2D you have the arrows that are the positive "s" direction, in 3D you need to ask for a plot and se the vector nx,ny,nz directions manually (this is easier in the new version but still sometoimes cumbersome)

Once the geoemtry has been made, and you do not modify it (entitiy renumbering the directio ndoes not change, so then you can check and adapt the sign

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Good luck
Ivar

Thank You so much. I got the idea now :).



Regards,
Tassawar