[shafee]

I am doing a case for my dissertation that is due in a week time.
I am running a supersonic flow around a cylinder Re 3.4x10^7. I have been have a problem that i do not know how to resolve. I have tried different mesh sizes. nothing works.
the flow starts with vortex shedding but as soon as it reaches 0.050seconds. the vortex shedding disappears and it the plots do not oscillate any more for lift and drag.
your help with be highly appreciated.
link to the file
https://www.dropbox.com/s/5zbgh4lc3m...0case.sim?dl=0

[FMDenaro]

Originally Posted by shafee

I am doing a case for my dissertation that is due in a week time.
I am running a supersonic flow around a cylinder Re 3.4x10^7. I have been have a problem that i do not know how to resolve. I have tried different mesh sizes. nothing works.
the flow starts with vortex shedding but as soon as it reaches 0.050seconds. the vortex shedding disappears and it the plots do not oscillate any more for lift and drag.
your help with be highly appreciated.
link to the file
https://www.dropbox.com/s/5zbgh4lc3m...0case.sim?dl=0

I suppose you are running some turbulence model in URANS formulation, maybe you get too dissipation from the model

[shafee]

Originally Posted by FMDenaro

I suppose you are running some turbulence model in URANS formulation, maybe you get too dissipation from the model

How do i fix that, any suggestions ?

[FMDenaro]

Originally Posted by shafee

How do i fix that, any suggestions ?

Check your type of discretization (upwind supplies artificial viscosity), check you turbulence model and analyze your grid (refine it if necessary).
Did you reach an asymptotic steady state running URANS?

[shafee]

Originally Posted by FMDenaro

Check your type of discretization (upwind supplies artificial viscosity), check you turbulence model and analyze your grid (refine it if necessary).
Did you reach an asymptotic steady state running URANS?

I am using send second order discretization. the turbulence model is KE.
you could look at attached picture
https://www.dropbox.com/s/74jgyppptn...23-15.png?dl=0

thanks for your help

[FMDenaro]

Originally Posted by shafee

I am using send second order discretization. the turbulence model is KE.
you could look at attached picture
https://www.dropbox.com/s/74jgyppptn...23-15.png?dl=0

thanks for your help

let your simulation run for longer time and see the velocity field in a zoomed region

[shafee]

Originally Posted by FMDenaro

let your simulation run for longer time and see the velocity field in a zoomed region

Fm denaro
i am currently generating smaller mesh.
following are the velocity scenes
https://www.dropbox.com/s/6a7qf13ocm...01-52.png?dl=0

[shafee]

Originally Posted by shafee

Fm denaro
i am currently generating smaller mesh.
following are the velocity scenes
https://www.dropbox.com/s/6a7qf13ocm...01-52.png?dl=0

https://www.dropbox.com/s/3vxq3g6evc...02-04.png?dl=0

[FMDenaro]

you must properly scale them, it is impossible to understand .....

[shafee]

https://www.dropbox.com/s/q93mf4lqp6...25-05.png?dl=0
does that help....
you may contact me on
+44(0)7799371737
or on facebook
Shafee Muhammad
thank you very much for your help appreciate it

[shafee]

07759735399*
apologies for the wrong numbher

[FMDenaro]

Originally Posted by shafee

https://www.dropbox.com/s/q93mf4lqp6...25-05.png?dl=0
does that help....
you may contact me on
+44(0)7799371737
or on facebook
Shafee Muhammad
thank you very much for your help appreciate it

still not enough clear this plot ....
however, I suggest to plot the total kinetic energy in the whole domanin versus the time. This way we can check if your simulation has reached a fully developed condition.

[shafee]

Originally Posted by FMDenaro

still not enough clear this plot ....
however, I suggest to plot the total kinetic energy in the whole domanin versus the time. This way we can check if your simulation has reached a fully developed condition.

thank you very much i will try that. it is absolutely driving me crazy ! having a breakdown I have been working on for the past 4-5 months... 6-7 hours daily ! i might end up smashing the computer !