[chuky_abc]

hello all,

as in pictures attached, i wanted to created a rotating part (yellow) inside a cylinder. so when i input rotational velocity to the rotating part, the vector of velocity on the inlet started to swirl before it even reached the rotating part, arent the vectors suppose to be straight first and rotate when it reach the rotating part?

[chuky_abc]

when i give rotational velocity of the rotating zone to 0, the vector seems to travel straight

[LuckyTran]

Originally Posted by chuky_abc

arent the vectors suppose to be straight first and rotate when it reach the rotating part?

To suddenly turn a fluid would require infinite force and energy. It must act over a finite length scale.

Navier-Stokes equations are elliptic, information (shear in this case) can propagate upstream. i.e. the downstream rotating fluid can drag the upstream fluid and also cause it to rotate. Laminar flows are dominated by momentum diffusion so this seems applicable. You can do some rough calculations to see if the shear stress is of the right order of magnitude.

[chuky_abc]

hi luckytran,

thanks for the explanation. btw could you have a look at my mesh file and tell me what i did wrong?

[chuky_abc]

Originally Posted by chuky_abc

hi luckytran,

thanks for the explanation. btw could you have a look at my mesh file and tell me what i did wrong?

Nevermind,

i have solved the problems