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Showing results 1 to 15 of 15 Search took 0.00 seconds. Search: Posts Made By: ghorrocks

Forum: CFX June 20, 2018, 02:16

Replies: 34 Error code 255 Views: 4,772 Posted By ghorrocks Recommendations unless you have a good reason to... Recommendations unless you have a good reason to do otherwise: Advection Scheme: HiRes Transient Scheme: If you are capturing important transient features then second order. If there are transient...

Forum: CFX June 19, 2018, 18:43

Replies: 34 Error code 255 Views: 4,772 Posted By ghorrocks There is nothing wrong with your settings. But... There is nothing wrong with your settings. But whether they are correct is another question. For instance: * Use are using upwind differencing. This is not recommended. * You are using second order...

Forum: CFX June 19, 2018, 06:12

Replies: 34 Error code 255 Views: 4,772 Posted By ghorrocks Convergence Criteria: You probably defined... Convergence Criteria: You probably defined imbalances as an additional convergence criteria, or maybe some other convergence criteria. That additional criteria has not converged so it continues...

Forum: CFX June 18, 2018, 19:32

Replies: 34 Error code 255 Views: 4,772 Posted By ghorrocks 1) That sounds a good approach for a research... 1) That sounds a good approach for a research project. 2) A few points here: 2a) Make sure you distinguish between start up transients, when the bubbles first start appearing and the flow is...

Forum: CFX June 17, 2018, 19:15

Replies: 34 Error code 255 Views: 4,772 Posted By ghorrocks 1) That is your decision. You have to judge... 1) That is your decision. You have to judge whether the result is significant or not. 2) We have already discussed this. If a time step does not converge then you risk inaccurate results. But if...

Forum: CFX June 17, 2018, 07:00

Replies: 34 Error code 255 Views: 4,772 Posted By ghorrocks Different simulations have different... Different simulations have different sensitivities to mesh quality. So I cannot assess whether your mesh quality is a problem or not. But I will guarantee that if you improve mesh quality, at least...

Forum: CFX June 16, 2018, 06:02

Replies: 34 Error code 255 Views: 4,772 Posted By ghorrocks a) Sure, but is your mesh fine enough to be... a) Sure, but is your mesh fine enough to be numerically accurate enough for your purposes? You do a sensitivity analysis to work this out. b) OK, and don't forget improved mesh quality and better...

Forum: CFX June 16, 2018, 05:14

Replies: 34 Error code 255 Views: 4,772 Posted By ghorrocks 1) Your text implies that it is not converging at... 1) Your text implies that it is not converging at the start of the simulation, even when you start with quite a small time step. If you need a time accurate simulation you need to fix this - improve...

Forum: CFX June 15, 2018, 08:28

Replies: 34 Error code 255 Views: 4,772 Posted By ghorrocks If you used an initial time step of 0.05[s] and... If you used an initial time step of 0.05[s] and it decreased it to 8e-5[s] then it says your initial time step is way too big. My guess of 1e-6[s] is better as it will converge OK from the first time...

Forum: CFX June 15, 2018, 07:37

Replies: 34 Error code 255 Views: 4,772 Posted By ghorrocks 2) Yes, the basic things you need to check are... 2) Yes, the basic things you need to check are set correctly on a transient simulation are the time step size, mesh size and convergence criteria. 3) Try this: Total Time = 1000[s] First update...

Forum: CFX June 15, 2018, 06:50

Replies: 34 Error code 255 Views: 4,772 Posted By ghorrocks 2) I do not understand what you are saying here.... 2) I do not understand what you are saying here. The normal way to work out what convergence criteria you require is to do a sensitivity study. Change the convergence criteria by a factor of 10 (say...

Forum: CFX June 15, 2018, 05:24

Replies: 34 Error code 255 Views: 4,772 Posted By ghorrocks If the residuals graph is less than your... If the residuals graph is less than your convergence criteria then those time steps converged. You should also be asking if the convergence criteria you defined is adequate, or even if it is too...

Forum: CFX June 13, 2018, 20:20

Replies: 34 Error code 255 Views: 4,772 Posted By ghorrocks Is this a transient simulation? My previous posts... Is this a transient simulation? My previous posts assumed that this is a transient simulation. If your simulation is steady state then your convergence is a problem. If your simulation is...

Forum: CFX June 13, 2018, 07:01

Replies: 34 Error code 255 Views: 4,772 Posted By ghorrocks 1) I cannot be sure about your settings but it... 1) I cannot be sure about your settings but it appears to have nothing to do with convergence. I did check your out file. 2) Don't worry about checking your Courant number to see if it is OK. CFX...

Forum: CFX June 13, 2018, 05:11

Replies: 34 Error code 255 Views: 4,772 Posted By ghorrocks There is no description of what the CFX error... There is no description of what the CFX error numbers mean. I don't know why they bother telling you a error number when they don't give you any information about it. But that is just my whinge. ...

Showing results 1 to 15 of 15

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