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Started By
Message
nevermind
Posted on 8/4/16 at 5:23 pm
Posted on 8/4/16 at 5:23 pm
(no message)
This post was edited on 1/10/21 at 10:42 pm
7
Posted on 8/4/16 at 5:36 pm to The Baker
Wait, you have questions about advanced fluid dynamics and "I know, I'll ask the motherfrickin' OT!!" is what popped into your head?
What firm do you work for? Your judgment is all kinds of fricked and we need to steer clear.
What firm do you work for? Your judgment is all kinds of fricked and we need to steer clear.
Posted on 8/4/16 at 6:02 pm to TigerstuckinMS
(no message)
This post was edited on 1/10/21 at 10:42 pm
Posted on 8/4/16 at 6:49 pm to The Baker
I do. They work in rocket fueling and engine testing. Smart folk. I tend to think they pad tolerances like other designers, but their designs are generally successful.
Just chimed in to say there's smarter stuff than o&g.
Just chimed in to say there's smarter stuff than o&g.
Posted on 8/4/16 at 6:57 pm to The Baker
quote:
Does anyone here have experience using CFD?
Somewhat.
Posted on 8/4/16 at 7:11 pm to CFDoc
(no message)
This post was edited on 1/10/21 at 10:42 pm
Posted on 8/4/16 at 7:13 pm to The Baker
I did my dissertation on multiphase reacting flows using several different algorithms, including VOF. However, I have never used Fluent to do VOF modeling.
Posted on 8/4/16 at 8:10 pm to CFDoc
(no message)
This post was edited on 1/10/21 at 10:42 pm
Posted on 8/4/16 at 8:11 pm to The Baker
Baw. You came to the wrong place for fluid dynamics advice.
Posted on 8/4/16 at 8:15 pm to jimbeam
(no message)
This post was edited on 1/10/21 at 10:42 pm
Posted on 8/4/16 at 8:30 pm to The Baker
Negative but #CFD
Hats off to folks who run into a fire-
Hats off to folks who run into a fire-
This post was edited on 8/4/16 at 8:34 pm
Posted on 8/4/16 at 8:34 pm to soccerfüt
(no message)
This post was edited on 1/10/21 at 10:42 pm
Posted on 8/4/16 at 8:40 pm to The Baker
You designing an offshore structure baw?
Oil rig? or Offshore wind turbine?
ETA: No I cannot help you with that problem........
Oil rig? or Offshore wind turbine?
ETA: No I cannot help you with that problem........
This post was edited on 8/4/16 at 8:44 pm
Posted on 8/4/16 at 9:17 pm to The Baker
I would probably need to sit down and thing about this some more. Also, I have never used delft-3d, so I can only guess the shallow water equations it solving. However, I will try to give you a few points to consider.
1) It sounds like you are modeling fully turbulent, 3D, flow using k-e in Fluent and then trying to compare it to an analytical relationship and the shallow water result. Given this, do you have a good reason to believe Fluent should be converging on the same answer as the analytical and shallow water solution in the first place? Did the analytical study include turbulent fluxes? What about the shallow water equations?
2) Is the actual flow you are trying to model fully turbulent? As far as I know, Fluent doesn't have a transition model for it's VOF algorithm. Therefore, if the actual flow isn't fully turbulent, the k-e model is going to make it fully turbulent regardless (it may be beneficial to switch to a one equation turbulence model like Spalart if not fully turbulent). This could easily give false mass fluxes in all directions.
3) Is the actual flow you are trying to model steady?
4) Does Fluent offer LES in conjunction with VOF? Might be worth a shot for unsteadiness and/or better flux calculations.
5) Have you done a grid resolution study at all? Are the Fluent fluxes still under-predicted if the grid resolution gets finer?
6) And finally, as a CFD pro, it is fairly well known throughout the community that Fluent is shite . Especially when it comes to resolving steep gradients (like what you see between an air/water interface). Fluent is going to smooth, diffuse, wash away, flux correct, and numerical viscosity its way through any steep gradient it feels will go unstable and crash the code. For them, the wrong answer is much better than NaN.
1) It sounds like you are modeling fully turbulent, 3D, flow using k-e in Fluent and then trying to compare it to an analytical relationship and the shallow water result. Given this, do you have a good reason to believe Fluent should be converging on the same answer as the analytical and shallow water solution in the first place? Did the analytical study include turbulent fluxes? What about the shallow water equations?
2) Is the actual flow you are trying to model fully turbulent? As far as I know, Fluent doesn't have a transition model for it's VOF algorithm. Therefore, if the actual flow isn't fully turbulent, the k-e model is going to make it fully turbulent regardless (it may be beneficial to switch to a one equation turbulence model like Spalart if not fully turbulent). This could easily give false mass fluxes in all directions.
3) Is the actual flow you are trying to model steady?
4) Does Fluent offer LES in conjunction with VOF? Might be worth a shot for unsteadiness and/or better flux calculations.
5) Have you done a grid resolution study at all? Are the Fluent fluxes still under-predicted if the grid resolution gets finer?
6) And finally, as a CFD pro, it is fairly well known throughout the community that Fluent is shite
. Especially when it comes to resolving steep gradients (like what you see between an air/water interface). Fluent is going to smooth, diffuse, wash away, flux correct, and numerical viscosity its way through any steep gradient it feels will go unstable and crash the code. For them, the wrong answer is much better than NaN. Posted on 8/4/16 at 9:49 pm to The Baker
Cfdoc couldn't get the suspension right on a mini car. Don't listen to him. Ha
Posted on 8/5/16 at 7:07 am to lurk9000
Good to see they brought Internet to your trailer park in Port Allen, J.
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