I'm using dynamic mesh to make a moving pipe ,the wall is defined as a rigid body ,the cells are hexahedral ,and I have used symmetry BC.

In previewing the motion just the wall moves and fluid interior cells get deformated and it creates negative volumes. I have used bellow command to turn on the Spring-Based Smoothing method:

> (rpsetvar 'dynamesh/spring/all-element-type? #t)

> dynamesh/spring/all-element-type?

but nothing changed. Maybe the settings that I put in dynamic parameters panel aren't correct , please please help me to solve this problem.

Thank you in advance.

svh

Hi For dynamic mesh moment, fluent gives us three methods(spring, layering , local remeshing). You had better use the spring and layering method to resolve your problems. If you can minish the time step of every literate, I think the negative volumes may be disappear.

lyf

Thank you lyf, the time step that I use is .01(s),is it big?

Is the form of mesh effective in moving?

Thanks again.

svh

Hi! svh

The time step* velocity <= the Cell Height on adjacent zone.

try to do it !

lyf

Hi!

My velocity function is :

vel[2] = 0.0628*cos(6.28*time) (metric system)

My time step size = .01 (s)

Cell Height = 2 mm

So time step size is not big ,Dear lyf is any thing else effective on moving ,like making active Sping Smoothing or the mesh?

Grate thanks.