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How to create time averaged plot for unsteady fluid flow problem?

Posted 4 dic 2010, 12:12 GMT-5 3 Replies

SM Ananth
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I have a cylindrical duct with a sinusoidal velocity boundary condition at inlet and a constant pressure boundary condition at exit.I could solve the problem and plot 'radial variation of velocity at a particular cross section' for a particular time instant. Now I want to get 'TIME AVERAGED radial variation of velocity at a particular cross section'.Can anyone suggest me how to do this? Thanks
3 Replies Last Post 20 lug 2011, 13:56 GMT-4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 5 dic 2010, 03:27 GMT-5
Hi

In v4, if you have a sinus input load and you solve in transient you will have the instantaneous value at any point in space (or over a boundary / cut plane). Now if you define a global variable and get the pressure out you can solve this in a table for each time, but you can also add a summing function to your table value (see the last section in the global evaluation or integration window). This would then integrate the result, up to you to divide it by the time interval

On the other side, if you use a harmonic solver and give the amplitude /phase input value (rms) ad a frequency scan you should also be able to get out the rms average value (and phase) at any cut/plane in your model, no?

The second case solves also quicker than the first one, I believe

--
Good luck
Ivar
Hi In v4, if you have a sinus input load and you solve in transient you will have the instantaneous value at any point in space (or over a boundary / cut plane). Now if you define a global variable and get the pressure out you can solve this in a table for each time, but you can also add a summing function to your table value (see the last section in the global evaluation or integration window). This would then integrate the result, up to you to divide it by the time interval On the other side, if you use a harmonic solver and give the amplitude /phase input value (rms) ad a frequency scan you should also be able to get out the rms average value (and phase) at any cut/plane in your model, no? The second case solves also quicker than the first one, I believe -- Good luck Ivar
SM Ananth
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Posted: 1 decade ago 6 dic 2010, 15:22 GMT-5
To Ivar sir,
Thanks a lot for your help...
To Ivar sir, Thanks a lot for your help...
Guillermo Vilaplana
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Posted: 1 decade ago 20 lug 2011, 13:56 GMT-4
Hi,

thank you Ivar, very clever ;)

Now any idea to plot the t-average on a whole surface?

Thanks
Guillermo
Hi, thank you Ivar, very clever ;) Now any idea to plot the t-average on a whole surface? Thanks Guillermo

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