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-   -   Force library (http://www.cfd-online.com/Forums/openfoam/118184-force-library.html)

pechwang May 22, 2013 09:05

Force library
 
Hello everyone,

I'm new to OpenFOAM. I played with icoFoam and simpleFoam for a few months. Now I want to move to multi-phase flow, which is mixture of air and water, so I choose interFoam. Then comes the question.
Originally I use the force library to calculate the torque and use patchIntegrate to calculate the volume flow rate in icoFoam and simpleFoam. And the viscosity of the single-phase flow is defined in transportProperties file. But now, it becomes multi-phase flow and the viscosity is a function of the phae fraction of the mixture, and the phase fraction is different everywhere. Then how can I calculate the "local viscosity" to calculate the force and torque on the wall? And how can I calculate the "pure" water flow rate at the boundaries.

Thanks,
Pengchuan

haakon May 22, 2013 09:10

When it comes to calculating what you call the "pure water flow" (or the volume flux of one phase only) I think you should study these tutorials:

https://www.hpc.ntnu.no/display/hpc/...llway+Tutorial
https://www.hpc.ntnu.no/display/hpc/...AM+-+swak4Foam

They describe in detail how to monitor flow of one phase, either in the domain or at a boundary.

pechwang May 22, 2013 09:20

Hi Hakon,

Thank you for your quick reply, I'll work on that. Thanks again. Then do you have any idea on how to calculate the torque?

Quote:

Originally Posted by haakon (Post 429226)
When it comes to calculating what you call the "pure water flow" (or the volume flux of one phase only) I think you should study these tutorials:

https://www.hpc.ntnu.no/display/hpc/...llway+Tutorial
https://www.hpc.ntnu.no/display/hpc/...AM+-+swak4Foam

They describe in detail how to monitor flow of one phase, either in the domain or at a boundary.


haakon May 22, 2013 09:28

No, not in multiphase flows at least. I know that in regular, single-phase flows the torque is calculated by the forces and forceCoeffs function objects. You specify the axis around which to calculate the torque with the CofR vector. But again, I am very uncertain on how to do this for multiphase flows.


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