CFD Module

New Multiphase Flow Interface: Three-Phase Flow, Phase Field

The new Three-Phase Flow, Phase Field interface can be used to model the flow and interaction of three different, immiscible fluids when you need to study the exact positions of the interfaces separating the fluids. This phenomenon is also known as separated flow with surface tracking. The fluid-fluid interfaces are tracked using a ternary phase field formulation that accounts for differences in the fluids’ densities and viscosities and includes the effects of surface tension. The phase field method can handle moving contact lines on no-slip boundaries.

In the example to the right, a gas bubble (the gray surface represents the gas-liquid interface) rises through a layer of heavy liquid (the blue surface represents the liquid-liquid interface) and into a lighter liquid. A portion of the heavy liquid is entrained into the wake of the gas bubble and transported up into the light liquid, where it becomes negatively buoyant and falls down toward the liquid-liquid interface. A surface plot of the velocity magnitude (the rainbow surface plot) over a central cross section is projected onto the rear container wall to enhance the visualization of the liquid-liquid and liquid-gas interfaces.

The predefined Three-Phase Flow multiphysics coupling combines a Laminar Flow interface with a Ternary Phase-Field interface. The movement of the fluid-fluid interfaces is determined by the minimization of free energy.

Libraries for liquid-liquid and liquid-gas surface tension coefficients are available. In the Wetted Wall feature, you can specify contact angles for fluid pairs at solid surfaces.

A flow between a gas and two liquids, simulated with the Laminar Three-Phase Flow, Phase Field interface.

A flow between a gas and two liquids, simulated with the Laminar Three-Phase Flow, Phase Field interface.

A flow between a gas and two liquids, simulated with the Laminar Three-Phase Flow, Phase Field interface.

New Mathematics Interface: Ternary Phase Field

The corresponding Ternary Phase Field interface, used to track moving interfaces between three immiscible phases in the CFD and Microfluidics modules, is also a standalone Mathematics interface.

New to the Rotating Machinery Fluid Flow Interface: "Turbulent Flow, Algebraic yPlus" and "Turbulent Flow, L-VEL"

In the Rotating Machinery interfaces, there are two turbulent flow models: Turbulent Flow, Algebraic yPlus and Turbulent Flow, L-VEL. For these models, the turbulent viscosity is determined using two different extensions of the logarithmic wall law. The local Reynolds number for these models is based on the distance to the nearest wall. The advantages of this approach are that no additional transport equations need to be solved and no inlet or outlet conditions need to be specified for the turbulence variables. Algebraic turbulence models are computationally cheaper and more robust (but generally less accurate) than transport equation turbulence models, such as the k-ε and k-ω models.

The velocity field and streamlines (colored by the turbulent viscosity) in an anchor-impeller mixer, simulated with the Algebraic yPlus turbulence model. The velocity field and streamlines (colored by the turbulent viscosity) in an anchor-impeller mixer, simulated with the Algebraic yPlus turbulence model.

The velocity field and streamlines (colored by the turbulent viscosity) in an anchor-impeller mixer, simulated with the Algebraic yPlus turbulence model.

New Feature in the Rotating Machinery Fluid Flow Interface: Stationary Free Surface

When solving a quasi-steady flow using the Frozen Rotor study type, you can now estimate the deformation of a free surface due to the combined effect of fluid flow and volume forces (such as gravity). An average pressure is applied on the selected boundary in the fluid flow computation. The surface elevation is then evaluated from the resulting pressure variations on the boundary in a postprocessing study step.

Streamlines and surface deformation due to the flow around a torpedo. The quasi-steady flow is computed with the Rotating Machinery, Fluid Flow interface using a Frozen Rotor simulation. Turbulence is modeled with the Algebraic yPlus model, and the surface elevation is obtained with the new Stationary Free Surface feature.

Streamlines and surface deformation due to the flow around a torpedo. The quasi-steady flow is computed with the Rotating Machinery, Fluid Flow interface using a Frozen Rotor simulation. Turbulence is modeled with the Algebraic yPlus model, and the surface elevation is obtained with the new Stationary Free Surface feature.

Streamlines and surface deformation due to the flow around a torpedo. The quasi-steady flow is computed with the Rotating Machinery, Fluid Flow interface using a Frozen Rotor simulation. Turbulence is modeled with the Algebraic yPlus model, and the surface elevation is obtained with the new Stationary Free Surface feature.

Additional Correlations for Heat Transfer Coefficients

The heat transfer coefficients library has a new convective heat transfer coefficient correlation for natural convection around a vertical thin cylinder. This heat transfer coefficient lets you replace a nonisothermal flow simulation with a heat flux boundary condition on the cylinder boundaries to reduce the computational cost of the simulation.

New App: Inkjet Design

Although initially invented to be used in printers, inkjets have been adopted for other application areas, such as within the life sciences and microelectronics. Simulations can be useful to improve the understanding of the fluid flow and to predict the optimal design of an inkjet for a specific application.

The purpose of the Inkjet Design app is to adapt the shape and operation of an inkjet nozzle for a desired droplet size, which depends on the contact angle, surface tension, viscosity, and density of the injected liquid. The results also reveal whether the injected volume breaks up into several droplets before merging into a final droplet at the substrate.

The fluid flow is modeled by the incompressible Navier-Stokes equations together with surface tension, using the level set method to track the fluid interface.

Screen captures of the pinch-off process during an inkjet simulation. The graphs show the injection-pulse profile (1D) and the time-evolution of the droplet size (2D, 3D). Screen captures of the pinch-off process during an inkjet simulation. The graphs show the injection-pulse profile (1D) and the time-evolution of the droplet size (2D, 3D).

Screen captures of the pinch-off process during an inkjet simulation. The graphs show the injection-pulse profile (1D) and the time-evolution of the droplet size (2D, 3D).

New App: NACA Airfoil Optimization

The aerodynamic properties of a wing, propeller, or turbine blade are to a large extent determined by the precise shape of the airfoil that is used. The NACA Airfoil Optimization application computes the two main aerodynamic properties (the lift and drag coefficients) of a fully parameterized NACA airfoil. It can be used to visualize how changes to the airfoil thickness, camber, and chord length affect the aerodynamics.

When you enter the fluid flow's Reynolds number into the simulation app, the appropriate fluid flow interfaces and meshes are automatically chosen based on this number. Low Reynolds number simulations are performed with the Laminar Flow interface, while high Reynolds number simulations use the Spalart-Allmaras turbulence model, which has been specifically developed for airfoil design simulations.

The airfoil geometry is fully parameterized and you can choose to either enter the airfoil's dimensions directly or let the app’s optimization solver find the optimal geometry in order to maximize the lift-to-drag ratio.

Turbulent flow around a NACA profile computed using the Spalart-Allmaras turbulence model. Turbulent flow around a NACA profile computed using the Spalart-Allmaras turbulence model.

Turbulent flow around a NACA profile computed using the Spalart-Allmaras turbulence model.

New App: Water Treatment Basin

Water treatment basins are used in industrial-scale processes in order to remove bacteria or other contaminants, such as for making water safe to drink.

The Water Treatment Basin application exemplifies the use of apps for modeling turbulent flow and material balances subject to chemical reactions. You can specify the dimensions and orientation of the basin, mixing baffles, and inlet and outlet channels. You can also set the inlet velocity, species concentration, and reaction rate constant in the first-order reaction.

The app solves for the turbulent flow through the basin and presents the resulting flow and concentration fields as well as the space-time, half-life, and pressure drop.

Velocity magnitude and streamlines from a simulation of reacting flow in a water treatment basin. Velocity magnitude and streamlines from a simulation of reacting flow in a water treatment basin.

Velocity magnitude and streamlines from a simulation of reacting flow in a water treatment basin.