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what is the difference between reacf and total stress?

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When I am playing with the flow past cylinder example in V4.1. I found the lift force for the cylinder is the integration of -reacf(v) over the boundary of the cylinder.
I guess if we integrate the total stress in y direction (-spf.T_stressy), the results should be exactly the same as the lift force.
However, to my surprise, these two values generally match, but with noticable difference. Please see the attached image in which the blue curve is the result from reacf(v), while the green one is from spf.T_stressy.
Anyone knows the difference between the two?
Actually, I am doing cases with moving boundary, where reacf(v) produces zero results, while spf.T_stressy gives seemingly good (but not necessary correct) results.
For your kind help or comments please.
ZR


0 Replies Last Post 18 mar 2011, 11:27 GMT-4
COMSOL Moderator

Hello Zirui Li

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