Discussion Forum

Posted: 1 decade ago 4 giu 2012, 12:44 GMT-4

Any other voluntary suggestions related to this design will be hugely appreciated.

Posted: 1 decade ago 5 giu 2012, 01:42 GMT-4

Hi its an impressive geometry you have mastered there, and all in COMSOL ! But still, I believe you will have to tweak it a bit further to avoid overlaps and silver edges, then you must use "assembly mode" to dedouble your boundaries, but previously you will need to do some grouping Unions) to minimise the pair creations First you have your perforations 1,2,3,4: I would only keep 1 & 3 have them start at 0.2 and go for 0.4" all the way through, then disable Perforations 2&4 this removes some silver edges where you have the tube flush with the transverse perforations and the interiour boundaries will be removed by the union Then you need to group the tubing into 3 objects by unions and differences try: an union1 of ext10,13,14,15,16 (do not keep objects nor interiour boundaries) then another union2 with mir2, cone2 ext7, 8, 9 and all the ext12(...) do not keep the objects nor interiour boundaris then a last union3 with ext1,2 mir1 all ext3,5(...), do not keep objects nor ineriour boundaries The last union3 has small faces that might need to be removed at the perforation outlets (to be considered) make a difference1 between union 2 - union3 (keep input obkect no interiour boundaries, then a difference2 between union1 - union3 (keep input objects, no interiour boundaries) then a difference 3 between diff2-diff1 (keep input objects, no interiour boundaries) The you need to remove the extra objects "Delete entities" union 1 & 2, and diff 2 Then use geometry assembly mode do not create pairs, keep imprints, it's in your case better to make the identity pairs manually. If you move to the material section you should now have only 3 entities in the geometry selection list, for your 3 fluids inlets You might want to keep certain internal boundaries to ease the meshing, such as at the cone tube sections caps, and you might want to further remove the small extra surfaces for the perforatiosn and get them flush with the tube Then you need to make indentity selections for the regions where the fluids mix. For this I would suggest to use extensively the Definition - Selections first, and make 3 extra views where you add a delete entity and select 1,2,3 so in each view you have ONLY one geometrical domain then its easier to catch the common interface surfaces. Once you have the selections, you can create youre Identity pairs too. For the mesh start meshing the source identity pais and copy the mesh onto the destination of you identity pairs, then mesh the rest, you will need a lot of RAm as you need a dense mesh, because of the object ratios. Do not forget to check the boundary meshings, asI'm not sure hoe these adapt to the "thin tubing" edge regions Finally, I would suggest to start setting up the physics ona much simpler i.e. 2D-axi partial model, when your physics are all set up you can make the one for the large model as you then know better the different BC settings, also start in laminar, then only move to turbulent (even consider useing a stationary laminar flow as initial velocity conditions for the turbulent case) do not forget you need 3 inlet BC and 1 outlet (I suppose) for the fluid part and 3 inlet temperatures and one outflow for the thermal part of NITF, plus whatever other BCs Finally for the selection of several individual physics and one commo, the one common is quicker to set up, but might be trickier to get to solve, you will probably need to play with the order of the segregated solver I hope these suggestions might help you on the way -- Have fun Comsoling Ivar

Posted: 1 decade ago 18 giu 2012, 13:33 GMT-4

Hi Mr. Kjelberg, Thanks a lot for spending time to read my question and giving your suggestion. I will implement the ideas you gave us and come back to you for more ideas.

Posted: 1 decade ago 18 giu 2012, 14:00 GMT-4

Is it possible to run the model assuming a multi-phase flow?? If yes, can you give us some ideas based on this? That'd be very helpful for us Thank you.

Posted: 1 decade ago 18 giu 2012, 14:02 GMT-4

[QUOTE] Hi its an impressive geometry you have mastered there, and all in COMSOL ! But still, I believe you will have to tweak it a bit further to avoid overlaps and silver edges, then you must use "assembly mode" to dedouble your boundaries, but previously you will need to do some grouping Unions) to minimise the pair creations First you have your perforations 1,2,3,4: I would only keep 1 & 3 have them start at 0.2 and go for 0.4" all the way through, then disable Perforations 2&4 this removes some silver edges where you have the tube flush with the transverse perforations and the interiour boundaries will be removed by the union Then you need to group the tubing into 3 objects by unions and differences try: an union1 of ext10,13,14,15,16 (do not keep objects nor interiour boundaries) then another union2 with mir2, cone2 ext7, 8, 9 and all the ext12(...) do not keep the objects nor interiour boundaris then a last union3 with ext1,2 mir1 all ext3,5(...), do not keep objects nor ineriour boundaries The last union3 has small faces that might need to be removed at the perforation outlets (to be considered) make a difference1 between union 2 - union3 (keep input obkect no interiour boundaries, then a difference2 between union1 - union3 (keep input objects, no interiour boundaries) then a difference 3 between diff2-diff1 (keep input objects, no interiour boundaries) The you need to remove the extra objects "Delete entities" union 1 & 2, and diff 2 Then use geometry assembly mode do not create pairs, keep imprints, it's in your case better to make the identity pairs manually. If you move to the material section you should now have only 3 entities in the geometry selection list, for your 3 fluids inlets You might want to keep certain internal boundaries to ease the meshing, such as at the cone tube sections caps, and you might want to further remove the small extra surfaces for the perforatiosn and get them flush with the tube Then you need to make indentity selections for the regions where the fluids mix. For this I would suggest to use extensively the Definition - Selections first, and make 3 extra views where you add a delete entity and select 1,2,3 so in each view you have ONLY one geometrical domain then its easier to catch the common interface surfaces. Once you have the selections, you can create youre Identity pairs too. For the mesh start meshing the source identity pais and copy the mesh onto the destination of you identity pairs, then mesh the rest, you will need a lot of RAm as you need a dense mesh, because of the object ratios. Do not forget to check the boundary meshings, asI'm not sure hoe these adapt to the "thin tubing" edge regions Finally, I would suggest to start setting up the physics ona much simpler i.e. 2D-axi partial model, when your physics are all set up you can make the one for the large model as you then know better the different BC settings, also start in laminar, then only move to turbulent (even consider useing a stationary laminar flow as initial velocity conditions for the turbulent case) do not forget you need 3 inlet BC and 1 outlet (I suppose) for the fluid part and 3 inlet temperatures and one outflow for the thermal part of NITF, plus whatever other BCs Finally for the selection of several individual physics and one commo, the one common is quicker to set up, but might be trickier to get to solve, you will probably need to play with the order of the segregated solver I hope these suggestions might help you on the way -- Have fun Comsoling Ivar [/QUOTE] Is it possible to run the model assuming a multi-phase flow?? If yes, can you give us some ideas based on this? That'd be very helpful for us Thank you.