CFD Module Updates
For users of the Mixer Module, COMSOL Multiphysics® version 6.3 introduces new Rotating Machinery, High Mach Number Flow interfaces for all transport-equation eddy-viscosity models and a new Mixing Plane feature for the High Mach Number Flow interfaces. This feature performs circumferential averaging of flow quantities while accounting for the direction of characteristics. The mixing plane approach is an efficient method for modeling sectors of centrifugal pumps, turbines, and compressors. The new predefined study Frozen Rotor with Initialization automatically adds a Mixing Plane Initialization study step, which computes average flow quantities using the initial values.
Reynolds-Stress Turbulence Models
The new Turbulent Flow, Wilcox R-w and Turbulent Flow, SSG–LRR (Speziale–Sarkar–Gatsk/Launder–Reece–Rodi) interfaces offer a higher-order closure, making them particularly effective for modeling secondary flows in ducts, flows with strong swirl or mean rotation, and flows with significant mean streamline curvature. Unlike eddy-viscosity models (EVM), these interfaces do not assume that Reynolds stresses are aligned with the mean strain rate, leading to more accurate results in complex flow conditions. The two Reynolds stress models, Wilcox R-w and SSG–LRR, differ primarily in how they model the pressure–strain term and the far-field specific dissipation rate.
Shear-Induced Migration in Dispersed Multiphase Flow
In concentrated suspensions, irreversible particle collisions lead to particle migration toward regions with lower shear rates, a phenomenon used in processes like particle fractionation and microfiltration. For example, in pressure-driven channel flow of a neutrally buoyant mixture, particles tend to aggregate at the center of the channel. A new Include shear-induced migration option, now available in the Mixture Model multiphysics coupling, supports multiple species and enhances the accuracy of such simulations. The Two-Phase Flow Modeling of a Dense Suspension tutorial model has been updated to use this new feature.
Kinetic Energy and Subsonic Inlet Condition in High-Mach-Number Flow
To improve energy conservation, the new Include kinetic energy option in the High Mach Number Flow interfaces provides a more accurate representation of viscous work. While the differences are often small, in certain cases this option delivers significantly better energy conservation. Additionally, for low-inlet Mach numbers, such as those in internal flow devices like ejectors, a new Subsonic option has been added to the Inlet feature, offering a less computationally demanding alternative to the Characteristics based option.
New Functionality in the Phase Transport Interfaces
A new Boundary Mass Source boundary condition has been added to the Phase Transport interfaces. This new feature accounts for the consumption or production of different phases due to reactions or other physical processes at boundaries. Boundary conditions will now be easier to set up when, for example, phase transport is coupled to surface reactions. Additionally, to help unify nomenclature across the different physics interfaces, the new Fluid and Porous Medium nodes have replaced the previously available Phase and Transport Properties and Phase and Porous Media Transport Properties nodes in the Phase Transport interfaces.
Power Law Option for Relative Permeabilities
The Porous Medium feature in the Phase Transport in Porous Media interface now includes a new Power law option, making it easier to implement relative permeabilities based on power law expressions. This enhancement simplifies the setup and modeling of permeability behavior in porous media simulations.
Result Templates in the Chemical Species Transport Interfaces
Creating useful and visually appealing plots of reacting systems can be time consuming since there are often many reactants and thus many concentration fields to plot. To save time, there are a number of new Result Templates in the Chemical Species Transport interfaces. Among these, plot array templates are now available that include up to four species concentrations simultaneously in the Graphics window. The Result Templates are available for all Chemical Species Transport interfaces, independent of the add-on product, but are especially useful for the multicomponent transport interfaces included in the modules for chemical engineering as well as in the Porous Media Flow Module, Subsurface Flow Module, and Microfluidics Module.
New Tutorial Model
COMSOL Multiphysics® version 6.3 brings a new tutorial model to the CFD Module.
Shock Diamonds from a Rectangular Nozzle
