Defining the Fluid Physics of a Flow Simulation

You can define the fluid physics to describe flow qualities that apply to the entire simulation, such as thermal and radiation effects, gravity, compressible flow, and turbulence. You can specify that the fluid physics in your simulation use the volume of fluid (VOF) method, an Eulerian algorithm that predicts the location of the interface between two immiscible fluids. You might want to define the fluid physics without the VOF method if your simulation includes compressible flow or multispecies sections or if you want to solve the analysis using the coupled solver.

This task shows you how to:

Define Fluid Physics Without Using the Volume of Fluid Method
Define Fluid Physics Using the Volume of Fluid Method

Define Fluid Physics Without Using the Volume of Fluid Method

From the Procedures section of the action bar, click Physics .
Optional: Enter a descriptive Name.
From the State options, select Fluid.
Select Enable thermal effects to include the effects of heat energy in your flow simulation.
Select Enable compressible flow to use the compressible flow algorithm to solve the fluid physics in this simulation.
Select Enable coupled solver to solve the Navier-Stokes equations using the coupled solver rather than solving them individually.
For more information, see About Coupled Solving Versus Segregated Solving.
Select Enable gravity to include gravitational effects in the fluid physics in the simulation.
By default, gravity is applied in the Z-direction, and the app activates the Boussinesq approximation to simulate natural convection cases. If you want to change either gravity-related behavior, open the Gravity parameters expander and change the parameters to ones suitable for your simulation.
Optional: Select the Turbulence model you want to use, if any, for the simulation.
For more information, see Defining Turbulence in Fluid Physics.
Optional: From the Radiation model options, select the Surface-to-surface radiation model to consider radiation heat transfer in a diffuse-gray enclosure.
By default, the radiation model calculates radiation using an ambient temperature of 300 K. You can change this temperature if the conditions in your simulation require a different ambient temperature.
Optional: To introduce solar radiation into your simulation, do the following:
1. Select Enable solar radiation.
2. Specify the Solar parameters, which describe the behavior of solar radiation in your simulation.
  For more information, see Defining Solar Radiation in Fluid Physics.
Optional: To specify the human comfort model for your simulation, do the following:
1. Select Enable human comfort model.
  The Human Comfort Parameters options appear.
2. Specify the Human Comfort Parameters, which describe the conditions that determine the level of comfort for the human models in the simulation.
  For more information, see Defining Human Comfort Parameters in Fluid Physics.
Optional: To include particle modeling in your simulation, do the following:
1. Select Enable particle modeling.
  The Particle Modeling Parameters options appear.
2. Specify the Particle Modeling Parameters, which describe whether the particles have mass and, if so, the composition of the particles.
  For more information, see Defining Lagrangian Particles in Fluid Physics.
Click OK.

Define Fluid Physics Using the Volume of Fluid Method

Before you begin: Define a VOF section for at least one component in your model in which no more than one of the materials is a compressible ideal gas. For more information, see Defining VOF Section Properties.

From the Procedures section of the action bar, click Physics .
Optional: Enter a descriptive Name.
From the State options, select Fluid.
Select Enable thermal effects to include the effects of heat energy in your flow simulation.
Select Enable compressible flow to use the compressible flow algorithm to solve the fluid physics for the compressible gas component of the VOF section.
Select Enable gravity to include gravitational effects in the fluid physics in the simulation.
By default, gravity is applied in the Z-direction, and the app activates the Boussinesq approximation to simulate natural convection cases. If you want to change either gravity-related behavior, open the Gravity parameters expander and change the parameters to ones suitable for your simulation.
Optional: Select the Turbulence model you want to use, if any, for the simulation.
For more information, see Defining Turbulence in Fluid Physics.
Select VOF to enable the VOF method.
By default, gravity is applied in the Z-direction, and the app activates the Boussinesq approximation to simulate natural convection cases. If you want to change either gravity-related behavior, open the Gravity parameters expander and change the parameters to ones suitable for your simulation.
Optional: From the Radiation model options, select the Surface-to-surface radiation model to consider radiation heat transfer in a diffuse-gray enclosure.
By default, the radiation model calculates radiation using an ambient temperature of 300 K. You can change this temperature if the conditions in your simulation require a different ambient temperature.
Optional: To introduce solar radiation into your simulation, do the following:
1. Select Enable solar radiation.
2. Specify the Solar parameters, which describe the behavior of solar radiation in your simulation.
  For more information, see Defining Solar Radiation in Fluid Physics.
Click OK.