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-   -   fluent flow problem (http://www.cfd-online.com/Forums/fluent/49970-fluent-flow-problem.html)

Tony December 4, 2008 08:20

fluent flow problem
 
Hi,

i am trying to model simple flow in a pipe with a cavity.

my boundary conditions are

inlet: 0.1mpa (absolute pressure) turbulence intensity 5% turbulence length scale 66.00mm mass flow rate 0.305kg/s

outlet;

atmospheric pressure i.e. guage=0 turbulence intensity 0.1% length scale 0.66mm

wanting to have a mass flow inlet and 0 guage pressure outlet but having problems solving as fluent is giving me errors-'absolute pressure limted' and ' problem with amg solver:pressure'

i am using second order wind solvers and the k epsilon turbulence model.

canyone help?


mAx December 4, 2008 10:00

Re: fluent flow problem
 
is your model right scaled? (eg: m, cm or mm, etc...?) check in define/scale

instead of massflow-inlet & pressure-outlet, try velocity-inlet & pressure-outlet

Tony December 4, 2008 10:16

Re: fluent flow problem
 
have checked scale and used a velocity inlet but getting same problem roughly after 35 iterations or so.

have calculated a velocity inlety of 87.834 m/s with temp of 291.0 k, turbulence intensity =5% and scale=66mm

have set my outlet to guage pressure= 0 with turbulence scale =0.1 and scale 66mm (diameter of flow) getting same problem ;

turbulence viscosity limited to viscosity ratio of 1.000e+05 absolute pressure limited to 1.00000e+00

then finally;

divergence detected in AMG solver:pressure correction

:(

mAx December 4, 2008 10:29

Re: fluent flow problem
 
*is the massflow conserved between inlet/outlet? (report/fluxes)

*switch to first order

*try several method for initialization

*is your mesh ok? (grid/check) (grid/info/quality)

if you still have troubles, zip your case file, and give me per mail a link where you shared it (rapidshare, etc...), I will take a loot at it, tomorrow


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