Floating Bodies - strange velocity profile depending on mk value

RCBE

Dear all,

I have a simple pipe flow with five floating cylinders (mk = 2,3,...,6). Without floating bodies the fluid velocity is 0.001 m/s. With floating bodies the velocity is much higher > 0.0018 m/s and the cylinder with the lowest mk value is always much faster than the others.
Here you can find some pictures and the xml-file.

https://www.dropbox.com/sh/cgw6yhwgyc4wv3c/AAD28Xx0Sbo_7sNVOCcfBxmda?dl=0

Every picture shows the fluid velocity after 1 second.
Pos1.png means left cylinder mk = 2
Pos3.png middle cyl mk=2
Pos5.png right cyl mk=2
...

So my question is:
Why has the floating body with mk=2 such an influence on the fluid velocity?

(This phenomenon occurred for other geometries and other floating bodies as well.)

Best regards

######## UPDATE ############
little workaround: placing the cyl with mk=2 outside the pipe → no influence on fluid. But this cyl is still moving with a fast velocity!

Alex

Can you please also send to us: CaseForcesData.csv

Regards

RCBE

Should be also available now

Alex

You have defined the acceleration 0.001 m/s^2.
That is not a cte velocity of the fluid of 0.001 m/s. Ok?

RCBE

I don't understand what you want to say.
With 0.001 m/s^2 the results say after 1s the fluid velocity is 0.001 m/s (without floating bodies - see picture).

Alex

Ok yes, if you are checking velocity after one second then that is the expected velocity you are right. I just want to avoid that confussion with LinearAcc

RCBE

There is now also a folder of the "workaround" available. I made a short movie.

https://www.dropbox.com/sh/cgw6yhwgyc4wv3c/AAADCX2Bemt1VpnNqYXYD4fOa/workaround?dl=0&preview=5cyl.avi

Two cylinders are now located outside the pipe. You can see that the left cylinder (floating body with lowest mkbound value) is moving very fast for no reason.

Bug?