dear All I have stumbled onto something I currently dont understand and which prevent me to move forward.
Because it can be of general interrest, I take the liberty to share it with you: it seems that Boundary submitted to constant heat flux and expected to remains at constant temperature in the context of defined case exhibits some small temperature gradient that can be amplified in some circumstances. In order to observe this problem which I initially found on case I build otherwise [ more on that later] , you can do the following: Start from the heatpipe case in dumux lecture Create some meshes along the y axis [ I put 10 meshes]. Run the case and observe the temperature profile on the right"heating" boundary You should observe a parabolic temperature with maximum on the edges and minimum on the middle My understanding is that the expected profile for this case should be a constant temperature. For this case the amplitude of the parabolla is very small and of no practical consequences at all. But, it increases with the heatflux and when near the critical flux becomes the seed for anomalous heating that make the resulst useless.[ because the edge are slightly hoter than the middle there is slightly more vapor which means the temperature increase more .. amd so forth... You observe this effect by increasing the heat flux in the previous case from 100W/m2 to the heat flux 4kw/m2 the amplitudes of the temperature difference increase and is not engligible anymore [by far] around 225000 s. That said, I am perfectly aware that the critical flux is an instability point both in computation and in real life. This example alone is probably not sufficient to point to a serious problem. I propose it for illustration purpose after I back engineered my way to it from cases I build in 3p3c where, apparently because of more complex phase/components interactions, this effect is further amplified to the point where low heat fluxes become supercritical creating localized pure vapor area and very hot zone at these corner points where none should exist. Back to dumux, this situation is not specific to BC "discontinuity" point as I initially thought. I have build examples where the heating surface is a square or a circle located in the middle of the porous material area [ so no BC discontinuities exist at all every connected boundary has the same bc] and observe these temperature profiles on the heated boundary otherwise expected to be constant. This predictably leads to the same observed anomalous heating. These points are always geometrically located [ aka not randomly placed] What do yo think of this ...? Am I missing something? Is this a known limitation in dumux? if yes, is there a workaround? Happy Holliday to you all!! _______________________________________________ Dumux mailing list [email protected] https://listserv.uni-stuttgart.de/mailman/listinfo/dumux
