General Question: Inlet- Outlet Mesh - have to be simular?
Hi guys,
iam kinda new in the whole cfd business, so here my question: i was wondering how important it is, that inlet and outlet have the same meshing (and by meshing in mean: simular number of cells). Is it at all important? My outlet got way more cells as my inlet (because i want to incert some particles and im really interested in where the particles "land" on the outlet screen) - was just wondering what and if that means anything for my results?! |
Hi Andi,
The only important thing is that you have to achieve grid independent results. Amir |
And by that u mean, that i have to change the mesh-type (for example from size function on curvature, on proximity) to another method of meshing? or can i show grid independence also by changes the number of cells.
another general question that comes to mind (its not connected with the question above). when i use symmetry on my tube-system, do i have to take only the half flow rate? that would also mean a lower velocity because of the half surface - so i guess not?!? i marked all symmetry-faces, so i thought (until now), that fluent is aware of that and handles it like "full". is that correct? |
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Yes that makes sense. velocity will not change.
when i calculate the turbulent intensity, do i have to use half-surface as a factor to calculate the Renolds-number as well? Re goes directly into the formular I = 0.16(RE)^(-1/8) its not topic related but i have another general question - and because you allready helped me that good, i ll try to post it in this thread :-) Imagine a CLOSED simple tube-system where i have 1 inlet and 1 outlet. how can i simulate the system beeing closed? i can asign 1 inlet (with my known velocity) and 1 pressure-outlet. but that doesnt fit my situation. i tryed to make the pressure-outlet a inlet with negative velocity, but that doesnt work and continuity should allready been considerated by fluent. i thought about making the pressure-outlet kind of a "pressure drop" - but i honestly dont know, how huge the drop is, because its not exactly a tube, its a little more complicated in the geometry. any suggestions? |
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just imagine a simple tube as a part of a closed system (by that i mean circular flow). i take 1 part of it and select inlet and outlet as named surfaces. then i put in the velocity at the inlet. the outlet i select as pressure-outlet (with no other options seleceted).
i believe that this system is simplified (by my settings). so from inlet there is fluid that flows out at the outlet (by in reality, it doenst flow out, its still a part of the circular flow). i dont know, if i loose information by just selection the outlet as simple pressure-outlet. sorry i cant post a picture. |
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Sorry for my poor discription, let me try it again.
I want to simulate suction at the outlet. What i think is , that a simple pressure-outlet isnt enough - i tryed to make the outlet a inlet with negative velocity, but that doesnt really work, i guess. |
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