Discussion Forum

model 2

Hi

I'm not sure, but use the latest patch it works better, have a look (the response changes depending if you turn on or off S2SR #3)

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Good luck
Ivar

Hi Ivar

Thanks, but my problem is in the MODEL (1) when enabling STSR #3 then it does not work.

surface 3 is the bottom surface of the cavity.

Thanks

Hi

Sorry my model (2) is your model(1) (poorly shoosen name I agree) but rebuild fresh in 4.1.0.185 version, I only copy/loaded the geometry (but I migh have missed or changed slightly other things).
As I could not get your v4.1.0.88 model to work, I suspect a version issue. Use the latest and forget about the previous ones, at least to the 3rd or forth release ;)

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Good luck
Ivar

hi Ivar

so it looks like surface numbers changes during this conversion. as i said STRS #3 is the surface which is the bottom surface of the cubic cavity in the bigger block. which indeed would be in a direct contact with the bottom surface of the block which is going inside. so when I activate that, in the time when the block wants to begin contact and gets in COMSOL says there might be a singularity problem!! but as you see in the other model which is just three blocks and we have again the same situation this thing works.

one question for me is, suppose we made models like two blocks over each other, one of them has its front in the middle of the other so when we want to select the surfaces of the blocks the contacting part between these two is defined as one surface in COMSOL but sometimes each surface is still related to each block and the contacting part is not another surface. did you get what I mean, I hope you do (my weak english :))

in the model which works now it looks like if we put surfaces on each other in geometry modeling each surface is still depends on the block but in the one that says singularity when they come on each other looks like the bottom surface is separated in two surfaces ! :(

and I just have version 4.1 :(

thanks,

Hi

indeed radiation between two surfaces, from the moment they are in "contact" or overlapping, seems not to work, could well be that the view factor cannot be correctly evaluated over a distance of "0"

But as you have contact transmission of heat, that is normally much higher than radiative exchange, so I believe you could estimate it by hand, and probably conclude that it might be ignored, or am I wrong ?

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Good luck
Ivar

thats correct Ivar.

the point is I need to define that surface as radiating surface in order to have it radiating when it goes over the hole :) so because radiation from the walls of the hole needs to be counted too so i can not say first i do a heat conduction simulation then in another septate simulation I calculate the radiation from the surface. so thats why I need to define that surface radiating from the beginning of the simulation, unless COMSOL has something that let me to cut a computation in the middle then go and define the surface radiating and then continue the computation which is not doable I think :)

could I say it, and am I right about it?

thanks

Hi

First check carefully how many watts is transferred via radiation and how much by contact, I suppose (havent checked) that you can neglect the radiation between the two parts apart from the radiation to you sensor. As these are not "in direct contact", I had no problem to simulate them, your round edge there changes the slope seen by the sensor, it's less steep with the round edge, as expected.

As its often tricky to set up all physics it's often worth to estimate first which are predominant, and then neglect the others in the model, anyhow a model is mostly 5-10% precise

Be sure you have patch 3 on your 4.1, there seem to be some issues or change of names in 4.1.0.88, with radiation

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Good luck
Ivar