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Showing results 1 to 13 of 13 Search took 0.00 seconds. Search: Posts Made By: ghorrocks

Forum: CFX December 19, 2012, 16:45

Replies: 33 SMC models Convergence Views: 5,529 Posted By ghorrocks That's why I generally recommend doing transient... That's why I generally recommend doing transient runs with adaptive time stepping homing in on 3-5 coeff loops per iteration. Then the solver automatically takes care of the time step size.

Forum: CFX September 28, 2012, 07:25

Replies: 33 SMC models Convergence Views: 5,529 Posted By ghorrocks An aspect ratio of greater than 1.2 results in... An aspect ratio of greater than 1.2 results in significant errors in surface tension modelling. The only way to be sure on what mesh quality it requires is to test it and find out. It may also be...

Forum: CFX September 7, 2012, 08:58

Replies: 33 SMC models Convergence Views: 5,529 Posted By ghorrocks RSM models are very sensitive to mesh quality.... RSM models are very sensitive to mesh quality. Your mesh quality is probably fine for 2-eqn models, but inadequate for RSM. In my experience RSM runs fine when the mesh quality is very good. But...

Forum: CFX August 6, 2011, 07:24

Replies: 33 SMC models Convergence Views: 5,529 Posted By ghorrocks If you change to local time stepping from... If you change to local time stepping from physical or vice versa you have to set a number of parameters correctly or it returns an error. Have a look at the CCL of a run set up for local time...

Forum: CFX August 5, 2011, 18:16

Replies: 33 SMC models Convergence Views: 5,529 Posted By ghorrocks 1 - there is no single timescale as it varies... 1 - there is no single timescale as it varies across the domain. 2 - running for about 1 time scale sounds sensible (1 flow-through time, 1 eddy turnover time etc) 3 - yes, you can also do the...

Forum: CFX July 26, 2011, 18:47

Replies: 33 SMC models Convergence Views: 5,529 Posted By ghorrocks Yes, I find it very useful for getting tricky... Yes, I find it very useful for getting tricky steady state simulations on the way to convergence. But you need to run physical timestepping for a while afterwards before declaring it converged, you...

Forum: CFX July 25, 2011, 08:12

Replies: 33 SMC models Convergence Views: 5,529 Posted By ghorrocks You can also get the same aspect ratio by staying... You can also get the same aspect ratio by staying at y+=1, but using 10 time more elements along the chord. Of course this results in a 10x larger mesh which only makes run times even longer.

Forum: CFX July 24, 2011, 06:33

Replies: 33 SMC models Convergence Views: 5,529 Posted By ghorrocks The under relaxation factor comments are not... The under relaxation factor comments are not relevant to CFX. The other comments are relevant, but only repeat what support said in your post yesterday.

Forum: CFX July 23, 2011, 06:25

Replies: 33 SMC models Convergence Views: 5,529 Posted By ghorrocks Well, we are both right. Both my comments and... Well, we are both right. Both my comments and support's comments are generalisations and I have no idea what is happening in your specific case. RSM is very sensitive to mesh quality, and RSM often...

Forum: CFX July 22, 2011, 08:26

Replies: 33 SMC models Convergence Views: 5,529 Posted By ghorrocks CFD was never meant to be easy. This is why most... CFD was never meant to be easy. This is why most people do not use RSM turbulence models.

Forum: CFX July 22, 2011, 07:10

Replies: 33 SMC models Convergence Views: 5,529 Posted By ghorrocks It should be low enough to make it converge :) ... It should be low enough to make it converge :) Aspect ratio of 1000 is still huge so I doubt that will work. 100 is still large but might be OK. Just keep improving it until it works.

Forum: CFX July 22, 2011, 00:00

Replies: 33 SMC models Convergence Views: 5,529 Posted By ghorrocks Aspect ratio of 8000 is pretty huge. You will... Aspect ratio of 8000 is pretty huge. You will need to get that down for a RSM.

Forum: CFX July 21, 2011, 19:21

Replies: 33 SMC models Convergence Views: 5,529 Posted By ghorrocks Reynolds stress models are hard to converge so it... Reynolds stress models are hard to converge so it is not a surprise that it has caused problems. They are often very sensitive to mesh quality.

Showing results 1 to 13 of 13

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