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Flow rate calculation - 2D model - FSI

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I have a 2D fluid flow model with a flow through a channel with rectangular cross-section. There is one inlet with non-zero inlet pressure and outlet with zero pressure.


After solving, in order to compute the volume flow rate , I started by going to Definitions > Model Couplings > Integration. I created a integration for the outlet boundary (which corresponds to the height of the channel in 2D view) and named it intop1

Then I went to Study > Update Solution (I had already computed the solution), then I went to Results > 1D Plot Group, then 1D Plot Group > Global.

In the Global plot I added the expression, intop1(fsi.U)*W which gives me values in m^3/s....where W is a constant and is the width of the channel.


Can someone confirm that this is the correct way to calculate volume flow rate?

Thank you.

1 Reply Last Post 5 set 2012, 22:06 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 set 2012, 22:06 GMT-4
Hi

I would say probably yes, as velocity times area is the flow.

But you should perhaps ask yourself which velocity component to chose?
Normally I would use the normal flow velocity (normal to my outlet surface). If this is a vertical boundary and yor flow is horizontal, then u[m/s]*height_y[m]*Width_z[m] is te flow in [m^3/s], where height_y is integral of the boundary length.
And as fsi.u is the x direction flow density field per boundary length element it's normal to integrate it to get a total global value

Units corresponds too, so just get clear the direction or scalar product of the velocity vector and the boundary normal and I would say: you are there

--
Good luck
Ivar
Hi I would say probably yes, as velocity times area is the flow. But you should perhaps ask yourself which velocity component to chose? Normally I would use the normal flow velocity (normal to my outlet surface). If this is a vertical boundary and yor flow is horizontal, then u[m/s]*height_y[m]*Width_z[m] is te flow in [m^3/s], where height_y is integral of the boundary length. And as fsi.u is the x direction flow density field per boundary length element it's normal to integrate it to get a total global value Units corresponds too, so just get clear the direction or scalar product of the velocity vector and the boundary normal and I would say: you are there -- Good luck Ivar

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