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Showing results 1 to 10 of 10 Search took 0.00 seconds. Search: Posts Made By: ghorrocks

Forum: CFX January 19, 2019, 04:50

Replies: 29 Convergence problem Views: 3,240 Posted By ghorrocks The oscillating pressure ratio is a sign the flow... The oscillating pressure ratio is a sign the flow is moving, and therefore it is a transient flow, not steady state. These become more common as you approach stall or other off-design flow...

Forum: CFX January 15, 2019, 16:32

Replies: 29 Convergence problem Views: 3,240 Posted By ghorrocks I don't have time to look at people's files in... I don't have time to look at people's files in detail. If you read the FAQ:...

Forum: CFX January 11, 2019, 14:50

Replies: 29 Convergence problem Views: 3,240 Posted By ghorrocks Start with the time step derived from the... Start with the time step derived from the residence time over all domains. But this is just a starting point - if it is converging easily then increase it, if it is having difficulties then decrease...

Forum: CFX January 11, 2019, 05:21

Replies: 29 Convergence problem Views: 3,240 Posted By ghorrocks Residuals to 1e-6 is very tight. But you might... Residuals to 1e-6 is very tight. But you might require it, you don't know if you don't check. So do a sensitivity check (compare 1e-4, 1e-5 and 1e-6) and see if you really do need this tight...

Forum: CFX November 14, 2018, 16:22

Replies: 29 Convergence problem Views: 3,240 Posted By ghorrocks Yes, you can use a time step smaller (or bigger)... Yes, you can use a time step smaller (or bigger) than 1/omega. 1/omega is just a guide, you can adjust it as you like from there. Don't go crazy any use 1e-10 as that will cause numerical problems...

Forum: CFX November 13, 2018, 17:05

Replies: 29 Convergence problem Views: 3,240 Posted By ghorrocks Yes, the small area of high residuals is likely... Yes, the small area of high residuals is likely to be causing the lack of RMS residual convergence. You should look at the residuals in the post processor and I bet you will find a small region of...

Forum: CFX October 30, 2018, 17:03

Replies: 29 Convergence problem Views: 3,240 Posted By ghorrocks The "accepted values" you quote are just... The "accepted values" you quote are just guidelines, and some simulations have a tighter requirement and some have a looser requirement. If this device is operating near the stall point your...

Forum: CFX October 29, 2018, 17:30

Replies: 29 Convergence problem Views: 3,240 Posted By ghorrocks In addition to Opaque's comments: * I would... In addition to Opaque's comments: * I would compare the reattachment model's results, in terms of your output parameters like output torque and see if it affects things. If it has no significant...

Forum: CFX October 28, 2018, 05:44

Replies: 29 Convergence problem Views: 3,240 Posted By ghorrocks I trust you will not ignore my previous post on... I trust you will not ignore my previous post on this thread. We have seen this question a lot on the forum so I have seen it before. Casing = stationary, yes this is normally correct. Inteface...

Forum: CFX October 26, 2018, 19:56

Replies: 29 Convergence problem Views: 3,240 Posted By ghorrocks It is normal for the design point of a pump to... It is normal for the design point of a pump to converge nicely, but as you approach stall convergence gets much harder. Some ideas: * You need to make sure your numerical stability is as good as...

Showing results 1 to 10 of 10

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