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Patch fully developed velocity and turbulence profile over full domain

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Old   June 10, 2015, 15:26
Default Patch fully developed velocity and turbulence profile over full domain
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Tom Derks
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Dear CFD users,

How can prescribe a velocity profile (created by write>profile) as initial condition over my full domain?

I have determined my fully developed velocity and turbulence profile with the following simulation:

3D steady state simulation of a pipe flow
model:multiphase vof, standard k-e enhanced wall Fn
fluid:water-vapor (in the next simulation a droplet will be released)
inlet: velocity inlet 15m/s
outlet: outflow
wall: no-slip
diameter: 3mm
length: 18mm (2xhydrodynamic entry length)

the velocity, turbulent kinetic energy and turbulent dissipation rate profiles at the outlflow have been saved by write>profile

I want to prescribe the values of this profile (see attachment) over the entire length of my pipe as the initial values. How do i do this?

I am able to choose the values of the profile as velocity inlet condition, however if i initialize my simulation fluent gives the whole domain the average velocity instead of the velocity profile.

Thanks in advance
Attached Images
File Type: jpg Fully developed profile.jpg (22.5 KB, 66 views)
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Old   June 27, 2015, 07:59
Default Any Solutions so far?
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Mohammad Mahmudur Rahman
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Hi

I am also kind of same situation. Did you able to solve that problem?

Regards
MR
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Old   June 29, 2015, 13:47
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Tom Derks
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Ansys fluent does not allow you to patch a profile (created by write>profile) over the full domain.

However you can solve a steady state simulation with your fully developed profile as inlet and outlet boundary condition.The result will be the fully developed profile over the full domain.

Now for multi-phase simulations you can patch other phases into the fully developed domain. And run the simulation without without initializing. This way you release the secondary phase in the primary fully developed phase.

http://www.cfd-online.com/Forums/att...1&d=1435599818



Unfortunately for me this does not result into stable solutions. Probably due to high pressure and velocity gradients at the interface of the patched droplet. After a few time steps high pressure peaks appear near the interface.(see picture) And eventually the droplet "explodes" resulting into a very low volume fraction over the domain.





The black and white lines represent the volume fraction contours

Does anyone has an idea to make this simulation more stable? And give it a realistic pressure distribution according to the Laplace pressure(high inside droplet low outside)
Attached Images
File Type: png pres+volfrac_contours_t=2.8e-6.png (39.9 KB, 284 views)
File Type: png pres+volfrac_contours_t=2.85e-6.png (50.9 KB, 276 views)
File Type: jpg drop_r=0,05_v=10_Tdrop=458_vel_t=0.jpg (27.5 KB, 281 views)
File Type: jpg drop_r=0,05_v=10_Tdrop=458_volfrac_t=0.jpg (21.4 KB, 62 views)
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fully developed flow, initialization, profile, turbulent flow

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