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Pressure Drop in a channel
Posted Sep 22, 2011, 6:03 p.m. EDT Fluid & Heat, Computational Fluid Dynamics (CFD) Version 4.2 1 Reply
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I have a micro channel with posts in it. I am trying to find the net pressure drop due to channel geometry.
I know the mass flow rate, surface roughness of the channel..
Is there a one click solution for this or do I have to export data to excel and calculate it manually with Navier Stokes or relevant equations..
I will also post this on Model exchange once I can get results.
Thanks
I know the mass flow rate, surface roughness of the channel..
Is there a one click solution for this or do I have to export data to excel and calculate it manually with Navier Stokes or relevant equations..
I will also post this on Model exchange once I can get results.
Thanks
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1 Reply Last Post Sep 25, 2011, 4:45 a.m. EDT
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Posted:
1 decade ago
Hi
no there is no "one click" solution ;) you can set up your model as a standard Fluid problem and have COMSOL solve it (it's a nice example so agree it would be nice to have it on the model exchange), this will give you velocities and pressure drops.
From the "engineering" fluid books you can find approximation formulas for different shapes, you should always use these to check your results but these are approximate and not really precise when you link in three domains like this.
Studying physics, and that is what COMSOL is all about - even if COMSOL itself is, per say, "only" and advanced PDE math solver programme, tailored for physics - is comparing approximate "engineering" formulas to more detailed FEM solving as you typically get with COMSOL.
Your case seems rather "simple to set up in COMSOL with the fluidics physics, import or build your geometry, define the liquid material parameters, define the physics boundary conditions: inlet, outlet, Mesh (try thedefault) but check that you have fine boundary meshings on all "no-slip" boundaries, check the meshing size and quality, check the initial conditions to have a minimum flow direction, and pressure drop ongoing such to better initiate the solution
and off you go.
Some tricks:
0) check your initial conditions before solving (solver dependent variables node + right click + "compute to selected")
1) use plotting while solving to see how the solver gets on, this might give you a clue of something wrong and you can interrupt and restart, without waiting a day for nonsense results ;)
2) you might be better off by adding an internal boundary to the left and right of your trapeze shape, such that you have a regular shape inlet nad outlet, and a well defined central block with all the cylinder I/F
--
Good luck
Ivar
no there is no "one click" solution ;) you can set up your model as a standard Fluid problem and have COMSOL solve it (it's a nice example so agree it would be nice to have it on the model exchange), this will give you velocities and pressure drops.
From the "engineering" fluid books you can find approximation formulas for different shapes, you should always use these to check your results but these are approximate and not really precise when you link in three domains like this.
Studying physics, and that is what COMSOL is all about - even if COMSOL itself is, per say, "only" and advanced PDE math solver programme, tailored for physics - is comparing approximate "engineering" formulas to more detailed FEM solving as you typically get with COMSOL.
Your case seems rather "simple to set up in COMSOL with the fluidics physics, import or build your geometry, define the liquid material parameters, define the physics boundary conditions: inlet, outlet, Mesh (try thedefault) but check that you have fine boundary meshings on all "no-slip" boundaries, check the meshing size and quality, check the initial conditions to have a minimum flow direction, and pressure drop ongoing such to better initiate the solution
and off you go.
Some tricks:
0) check your initial conditions before solving (solver dependent variables node + right click + "compute to selected")
1) use plotting while solving to see how the solver gets on, this might give you a clue of something wrong and you can interrupt and restart, without waiting a day for nonsense results ;)
2) you might be better off by adding an internal boundary to the left and right of your trapeze shape, such that you have a regular shape inlet nad outlet, and a well defined central block with all the cylinder I/F
--
Good luck
Ivar