How to active "Spring-Based Smoothing "?
 

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