COMSOL Multiphysics^® 5.5 Release Highlights

Microfluidics Module Updates

For users of the Microfluidics Module, COMSOL Multiphysics^® version 5.5 brings inelastic non-Newtonian constitutive relations in two-phase flow, an Interior Slip Wall feature, two new Pair features, Continuity and Initial Interface in the Two-Phase Flow, Phase Field interface, and two new optimization tutorials. Read more about these features and functionality below.

Inelastic Non-Newtonian Constitutive Relations

Many fluids are non-Newtonian, that is, the relationship between strain and stress is nonlinear. Non-Newtonian behavior can, for example, be observed in aqueous solutions of corn starch, ketchup, blood, and paper pulp. Users of the Microfluidics Module can now simulate two-phase flow of inelastic non-Newtonian fluids using either the Level Set or Phase Field models.

The Settings window in COMSOL Multiphysics for the Two-Phase Flow, Level Set multiphysics coupling with the Domain Selection and Fluid Properties sections open.

Settings window for the Two-Phase Flow, Level Set multiphysics coupling node, showing the Power Law option in the inelastic non-Newtonian constitutive relation.

Interior Slip Wall Feature

Thin barriers in the flow field can be modeled more efficiently by ignoring their thickness and thus treating them as interior surfaces in 3D, or interior edges in 2D. For users of the Slip Flow interface, the new Interior Slip Wall feature can be used to apply slip conditions, due to noncontinuum effects in viscosity and/or thermal creep, on both sides of an interior barrier.

A model of a pipe with a black inclined slip wall mounted inside and streamlines visualizing flow going through the pipe and around the wall.

Streamlines and pressure (color table) for flow past an inclined slip wall (black) mounted in a pipe.

Continuity and Initial Interface Pair Features

On interior boundaries across which the mesh is discontinuous, such as when two domains slide against each other, the phase-field variables can be made continuous by applying one of two new Pair features: the Continuity and Initial Interface pairs. The Initial Interface pair can, in addition to enforcing continuity of the phase-field variables, be used to smooth an initial discontinuity that may occur as a result of specifying different phases on adjacent domains.

A model of a channel with internal gravity waves shown in blue as well as the mesh.

Internal gravity waves generated by a volume force active in the lower half of the channel. The Initial Interface pair is used to make the phase-field variables continuous across an assembly boundary with nonmatching tetrahedral and hexahedral meshes, in the lower and upper half of the channel, respectively.