Simulating two-phase, immiscible fluids

Video: Model water sloshing in a bottle

You can model the following two-phase, immiscible fluid simulation problems:

• Open volume enclosures, such as filling problems.

• Closed container problems, such as water sloshing in a bottle or fuel levels in a gas tank.

Note:

Simulating two-phase, immiscible fluids is supported only by the parallel flow solver.

Specifying constituents of the mixture

You specify the constituents in the Immiscible Fluid Mixture modeling object. One fluid is the tracked fluid and the other fluid represents the complementary fluid. The fluid mixture can consist of any of the following constituents:

• One liquid and one gas

• Two liquids

• Two gases

When you define the material for the meshes, the 3D solid mesh collector must point to the modeling object.

Note:

The modeling of two-phase flows does not support temperature-dependent density and specific heat.

Specifying initial conditions

To define the region that contains the tracked fluid at the start of your analysis, you must create an Initial Immiscible Fluid Mixture — 3D Flow type of the Initial Conditions constraint.

Closed volume enclosures

To model rigid body movement of closed enclosures containing a two-phase, immiscible fluid, you must define a time-varying acceleration for the Moving Frame of Reference simulation object. Do the following:

• To define a translating acceleration, set Type to Translating Frame of Reference.

• To define a rotating motion, set Type to Rotating Frame of Reference. The mixture enclosure is completely contained in the region of the rotating frame of reference.

Open volume enclosures

To simulate an open volume enclosure, you specify the tracked fluid area fraction of the mixture that enters the enclosure in the following ways:

• Specify it locally for each inflow boundary condition, for the following types of Flow Boundary Condition simulation object: Inlet Flow, Opening, or Static Pressure.

• Specify it globally for all inflow boundary conditions, under the Ambient Conditions node in the Solution dialog box.

The mixture leaves the enclosure on faces for the following types of Flow Boundary Condition simulation object: Outlet Flow, Opening, Convective Outflow, or Static Pressure. The flow solver computes the tracked fluid area fraction for the mixture that leaves the enclosure.

Two-phase, immiscible fluid simulation workflow

• Mesh the two regions using 3D elements. You can mesh both regions in the same mesh or have different meshes for the two regions. You must use mesh mating conditions when you use more than one mesh.

• Create an Immiscible Fluid Mixture modeling object in the 3D mesh collector.

• Create an Initial Immiscible Fluid Mixture — 3D Flow type of the Initial Conditions constraint to define the initial tracked fluid region, if it exists.

• Define the necessary boundary conditions:Inlets and openings for open volume enclosure problems.Time-varying acceleration for sloshing problems.

• Define a flow or coupled thermal-flow solution using the parallel flow solver.

• Solve and post process your solution.When you post process the results, a volume fraction value close to one indicates that the mixture is mostly composed of the tracked fluid whereas a value close to zero indicates that the mixture is mostly composed of the complementary fluid.

How do I

Model water sloshing in a bottle

Learn more

Immiscible Fluid Mixture

Initial Conditions

Moving Frame of Reference

Quick links

Command reference

Pre/Post video examples

Bulk Entry Descriptions

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Simcenter 3D Thermal/Flow, Electronic Systems Cooling, and Space Systems Thermal boundary conditions

Simulating two-phase, immiscible fluids, Simcenter 3D 2021.1 Series

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