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Simple Question for Flow Rate

Posted Jan 16, 2012, 1:30 p.m. EST MEMS & Nanotechnology, Fluid & Heat, MEMS & Piezoelectric Devices, Computational Fluid Dynamics (CFD), Microfluidics, Porous Media Flow, Modeling Tools & Definitions, Parameters, Variables, & Functions 5 Replies

COMSOL user2
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Hello,

I already done a few simulations with "laminar flow" using time dependent with rectangular input.

Input was "pressure, no viscous stress".

Is there any ways of getting the flow rate from "results" as post process?

I just calculated "area" * "velocity", but there should be a better way of getting it through Comsol.

Thanks.
5 Replies Last Post May 11, 2017, 2:18 p.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jan 16, 2012, 5:12 p.m. EST
Hi

you mean you calculated the area and multiplied by the average velocity ?
what about integrating the local velocity

int_over_area_of v*dx*dy => m^3/s ... no ?

Do not forget the 2*pi*r in 2D-axi

--
Good luck
Ivar
Hi you mean you calculated the area and multiplied by the average velocity ? what about integrating the local velocity int_over_area_of v*dx*dy => m^3/s ... no ? Do not forget the 2*pi*r in 2D-axi -- Good luck Ivar
COMSOL user2
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Posted: 1 decade ago Jan 16, 2012, 5:54 p.m. EST
Thanks Ivar as usual.

Where & How do I need to type it? BTW I'm using 3D.

Thanks.


Hi

you mean you calculated the area and multiplied by the average velocity ?
what about integrating the local velocity

int_over_area_of v*dx*dy => m^3/s ... no ?

Do not forget the 2*pi*r in 2D-axi

--
Good luck
Ivar


Thanks Ivar as usual. Where & How do I need to type it? BTW I'm using 3D. Thanks. [QUOTE] Hi you mean you calculated the area and multiplied by the average velocity ? what about integrating the local velocity int_over_area_of v*dx*dy => m^3/s ... no ? Do not forget the 2*pi*r in 2D-axi -- Good luck Ivar [/QUOTE]
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jan 16, 2012, 6:01 p.m. EST
Hi

either you need a variable for your solving, then you Define a surface integration operator on your flow area / boundary / surface and you define a variable vdens=intop1(spf.U)

Or its for postprocessing and you right click the Derived variable node under Results and add a surface integration on the flow boundary and you type spf.U, or whatever adequate flow component u,v,w and "execute " = "


the dx*dy is implicit and is part of the integation operator, just as the references to the location is implicit by the selection of the boundary and the integration operator (specific COMSOL notation not 100% obvious in the beginning I agree ;)

--
Good luck
Ivar
Hi either you need a variable for your solving, then you Define a surface integration operator on your flow area / boundary / surface and you define a variable vdens=intop1(spf.U) Or its for postprocessing and you right click the Derived variable node under Results and add a surface integration on the flow boundary and you type spf.U, or whatever adequate flow component u,v,w and "execute " = " the dx*dy is implicit and is part of the integation operator, just as the references to the location is implicit by the selection of the boundary and the integration operator (specific COMSOL notation not 100% obvious in the beginning I agree ;) -- Good luck Ivar
Puttagunta Yaswanth
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Posted: 8 years ago Oct 3, 2016, 8:21 p.m. EDT
if we do intop1(u) then we get m^4/s which is equal to volume integration in derived values , as i am doing 3d so can i consider volume integration of velocity is flow rate ?
please suggest me
Thanks
Regards
if we do intop1(u) then we get m^4/s which is equal to volume integration in derived values , as i am doing 3d so can i consider volume integration of velocity is flow rate ? please suggest me Thanks Regards
Syairah Soib
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Posted: 8 years ago May 11, 2017, 2:18 p.m. EDT
hi ivan, can i get your email. i want to ask a question regarding how to plot the frequency vs flow rate graph.

syairahs@gmail.com , incase i didnt get notified from this site. thank you.
hi ivan, can i get your email. i want to ask a question regarding how to plot the frequency vs flow rate graph. syairahs@gmail.com , incase i didnt get notified from this site. thank you.

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