October 13, 2020 at 11:29 pmsimonhennSubscriber
I have a problem simulating an airflow through a diffuser. I use a mass flow inlet and a pressure outlet. The mass flow is 0.485 kg/s and the static outlet gauge pressure is 3600 pa. I use the Coupled Solver and comprossible flow setting.
When I start the calculation I immediately notice that the residuals don't really decrease very much:October 14, 2020 at 1:12 amKarthik RAdministratorFirstly, when I look at the residual plot, it seems like your simulation is not converged. Please make sure that your simulation converges.nWhat is your Mach number? Is the working fluid air? nHow do your inlet and outlet diameters compare?nThanks.nKarthiknOctober 14, 2020 at 8:42 amsimonhennSubscriberHello, nI'm pretty sure that they would have diverged later because that's what always happens when I let it run. So I stopped the calculation to see in which direction the results are going. nThe mach number is around 0.2-0.25, the fluid is compressible air. When I solve with incompressible air it also diverges. nThe inlet area is 6*10^(-3) m^2, outlet area is 1.9*10^(-2) m^3. nActually the mass flow rate is 0.38 kg/s, I got that wrong in the question.October 14, 2020 at 9:36 amRobAnsys EmployeeThat should solve very quickly, so check the mesh and post some images of the flow field. nOctober 14, 2020 at 10:25 amsimonhennSubscriberWhat exactly do you mean with checking my grid? nOctober 14, 2020 at 10:43 amRobAnsys EmployeeIs the cell quality in the acceptable range, and have you resolved the wall and flow. nOctober 15, 2020 at 10:10 pmsimonhennSubscriberYes, I always get told to check my mesh but which are the specific metrics I should check and in which range should they be?nOctober 16, 2020 at 11:05 amRobAnsys EmployeeHave you read the documentation, Meshing - Global Mesh Controls - Quality Group - Mesh Metric - Skewness will give you a good starting point. Fluent User's Guide (Solution) 6.2.2 also has guidance. nViewing 7 reply threads
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