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 multiphase 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 singlephase flow is defined in transportProperties file. But now, it becomes multiphase 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 
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. 
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:

No, not in multiphase flows at least. I know that in regular, singlephase 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.

Hi Pengchuan,
have you made any progress in this problem? I also deal with the problem how to calculate the torque of a patch when there is a multiphase flow and the properties like density and viscosity depend on the alpha value. Greetings. 
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