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Senior Member
Nejc
Join Date: Feb 2017
Location: Slovenia
Posts: 196
Rep Power: 9 ![]() |
Hello,
I've been struggling to make my pump case run for well over six months now and now I decided to split my problem(s) into smaller ones, starting with meshing. I made the simplest case I could think of: a sudden expansion joint, see attached pictures. To eliminate errors on the inlet edge I declared a 'slip' BC on a short section after inlet patch. I used k-omega SST turbulence model and wall functions. Boundary conditions are 1m/s inlet velocity and 0 outlet pressure, noSlip walls (except the mentioned patch). I tried with a few different meshes: - snappyHexMesh with 1, 0.5, 0.25 and 0.125mm 'smallest' cell without boundary layers - cfMesh with 1x 1mm, 3x 0.5mm and 5x 0.3mm boundary cells - cfMesh with 10x 8um boundary cells without wall functions I also tried the cfMesh cells without turbulence modelling. All except one laminar case converged. Here are a few numbers I think are important: Code:
mesh min size N*y+ Umax pmin snappy coarse 1mm 1.074 -0.217 snappy medium 0.5mm 1.073 -0.213 snappy fine 0.25mm 1.083 -0.221 snappy extrafine 0.125mm 1.088 -0.225 coarse layers 1x 1mm 110 1.243 -0.237 medium layers 3x 0.5mm 54 1.1 -0.247 fine layers 5x 0.3mm 33 1.103 -0.241 no wall functions 10x 9um 1 1.087 -0.301 y+ = 9um I now have no idea what the results mean. Are the results reasonable and which ones should be trusted most? Thanks! Last edited by kandelabr; September 4, 2017 at 09:34. Reason: added BC explanations |
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