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transient flow simulation shows odd behaviour

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Old   March 12, 2021, 09:25
Default transient flow simulation shows odd behaviour
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Hello everyone,



For school I have to analyse a flow past a needle valve. To make sure all the settings are right I want to do a simple simulation that doesn't take too much computing time. The idea is to perform a transient flow simulation around a cylinder. The results should look something like this:
vortex shedding around a cylinder.jpg


(The vortex shedding is moving of course, but the velocity at the inlet, walls and outlet stays mainly the same)



I posted a video on vimeo of the results regarding my simulation:


https://vimeo.com/522807243/d441011624


The high velocity in the whole fluid is moving back and forth. Only the velocity at the inlet stays the same but furthur in the fluid domain it starts to fluctuate. The velocity and pressure plots show the fluctiation:
pressure.JPG
velocity.JPG

For clarification some settings of the simulation:

mesh size.JPG

mesh:

mesh sizelength of the box: 200mm

diameter cylinder: 9mm



boundary conditions

inlet: inlet flow 10 m/s

outlet: opening

symmetry plane



solution parameters


serial solver

k-epsilon turbulence model

transient

time interval: 0 - 0.009 sec

time step: 0.000045 sec

results: match integration times



does someone know what I'm doing wrong?



Thanks in advance,



Jesse van Asseldonk
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