July 10, 2019 at 5:15 pmtoramanSubscriber
I have a ribbed duct 80*80*200 mm that is heated from sublayer (2000 W/m2 constant heat flux). Reynolds is between 10000 – 30000. I applied an inlet volume 1000 mm to obtain hydrodynamically fully developed flow additionally, also an outlet region 200 mm.
In meshing, I applied first layer thickness for inflation ( y+ = 1 and for different Reynolds number ) but continuity fixed on 10^-3 no reduce. For other residuals no problem. If I use y+ > 11, 30, etc. , the total inflation layer thickness is over my shortest rib so the rib keeps in inflation layer.
Skewness 0,21 and Orthogonal Quality 0,78
I’ve also tried many times in k-w SST, k-e RNG, etc. also but no change.
Does anybody suggest?
July 12, 2019 at 10:22 pmRaef.KobeissiSubscriberTry to run it for longer, have you used 2nd order Upwind? Also try to have a longer domain to avoid having flow reversal or use outflow as an outlet bc.
July 12, 2019 at 10:32 pmtoramanSubscriber
I used the second upwind. I applied an inlet region approximately 10*Hydrolic Diameter and although no see the convergence of continuity able to observe the velocity profile well.
July 12, 2019 at 10:36 pmRaef.KobeissiSubscriberI would run it a little bit more and I would try to decrease the momentum under-relaxation factor to 0.5. Have you used the SIMPLE algorithm? Also try using Outflow rather than pressure outlet.
July 12, 2019 at 10:52 pmtoramanSubscriber
Thanks for your reply. I also tried URF. Residuals reduced for a short time but then increased again. However, I think that the problem is estimating the first layer thickness. I saw your calculator and tried but the results are totally different from mines that ? used below the which is for duct flow.
July 13, 2019 at 12:25 amRaef.KobeissiSubscriberI don’t think that’s the problem. You already mentioned that you y+ is 1so your thickness is alright. Try to initialise from inlet make sure your turbulence intensity is correct and insert correct hydraulic diameter at inlet. Use outflow..
July 13, 2019 at 1:28 am
July 13, 2019 at 2:50 amtoramanSubscriber
Sorry I checked intensity on fluent boundary conditions it is %5 as default I think that's ok.
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