lift and drag calculation in LBM

[garcfd]

How do people usually calculate lift or drag in LBM code?

1. integrate pressure over the body surface?

2. momentum exchange method at the boundary wall?

3. wake-traverse method to integrate u(Uinf-u) at downstream plane?

I have tried a few different methods and they are all highly dubious, giving variable numbers.
I would love to know if there are reliable / accurate methods for calculating the drag in LBM.
Thankyou.

[mathias]

Option 2 is what is usually been doen and what OpenLB uses as well!

[garcfd]

Thanks – can you point me to the paper (or code) which describes how the momentum exchange method was implemented (please)?

[garcfd]

I just spotted a couple of clues in the source code:

MOMENTUM_EXCHANGE_FORCE_H
//Momentum Exchange Wen2014
return (f1*(c-pVel) + f2*(c+pVel));

//Momentum Exchange Ladd1994
return ((f1 + f2)*c);

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