What is Wall Slip?

Typically, fluid velocity at the wall is assumed to be zero as “no-slip boundary condition” Wall slip occurs when a fluid moves along the wall with a non-zero velocity, Common in polymer melts, highly filled materials, or concentrated suspensions.

What is Critical Wall Shear Stress?

Wall slip starts only when the wall shear stress exceeds the critical value, a threshold value of wall shear stress.
Below this value → No slip occurs (standard no-slip behavior)
Above this value → Wall slip begins (velocity at the wall > 0)

Wall Slip Models in Moldex3D

1. Power Law Model

Based on an empirical slip behavior model (commonly used for polymer melts)
Assumes that wall slip velocity follows a power-law relationship with wall shear stress
2.Friction Force Model

Based on the slip behavior model, but models wall slip as a result of frictional resistance between the wall and fluid