You can create fluids for fluid flow analysis, solids for heat transfer analysis, or you can create both materials in a single project for the simulation of conjugate heat transfer (CHT) between solid and fluid domains.
Create a Material
Click the + icon next to Material.
Select Fluid or Solid.
In the properties panel below, fine-tune the specifics of your material (explained in the sections below).
Assign volumes to your material.
Once you have materials defined, you can move on to creating Physics.
Fluid
You can use fluid materials for external aerodynamics and internal flow cases, or in conjunction with solid materials for CHT analysis. There are three options in the Material Preset dropdown menu:
Standard Air: Selecting this will set up a compressible flow simulation using air. You will not be able to edit the properties of the fluid.
Water: Selecting this will set up an incompressible flow simulation using water. You will not be able to edit the properties of the fluid.
Custom: Selecting this will allow you to fine tune all of the properties. You can set up compressible or incompressible flow simulations with this option.
Reference Pressure
The operating pressure for your simulation is defined by this value. The absolute pressure of the simulation will be this plus the pressure calculated in the simulation. All pressure values specified during initialization and in boundary conditions will be with respect to this reference pressure.
Density Relationship
This is where you can choose between compressible and incompressible flow:
Ideal Gas Law: This will set up a compressible simulation. You will need to specify the Molecular Weight and Specific Heat at Constant Pressure values.
Constant Density: This will set up an incompressible simulation. You will need to specify a Constant Density Value.
Constant Density with Energy Equation: This will set up an incompressible simulation and allow you to model energy transfer in constant density flows. You will need to specify a Constant Density Value, Specific Heat at Constant Pressure, and a Laminar Thermal Conductivity Model.
Dynamic Viscosity Model
There are two options in the Dynamic Viscosity Model dropdown menu:
Constant Laminar Viscosity: This is the only option for incompressible flow simulations. You will need to specify a Viscosity value.
Sutherland's Law: You will need to specify a Reference Viscosity, Reference Temperature, and Sutherland Constant.
For compressible flow you can also select the Laminar Thermal Conductivity Model to be either Prandtl Number or Constant Conductivity, setting the relevant value in the box below.
Boussinesq Approximation
Boussinesq Approximation allows you to model natural convection for constant-density fluids by including the forces caused by thermal expansion without changing the density used in the incompressible Navier-Stokes equations.
Important: Because density remains constant for conservation purposes, this model is not adequate for large density variations. The absolute value of alpha times the maximum difference between fluid temperature and reference temperature should be much smaller than 1. It's important to use a reference temperature adequate to the boundary conditions of the problem. For example, the expected average temperature of the fluid or the initial fluid temperature.
To use this feature:
Turn on Gravity in General.
In Materials, select the desired material, then find the Density Relationship dropdown in the properties panel. Select Constant Density with energy equation.
Scroll down and find the Boussinesq Approximation dropdown. Select On.
Specify a Reference Temperature and a Thermal Expansion Coefficient.
Solid
You can use a solid material for heat transfer analysis, or in conjunction with fluid materials for conjugate heat transfer (CHT) analysis.
There are multiple options in the Material Preset dropdown menu:
Aluminum
Copper
Iron
Nickel
Titanium
When you create a custom solid material, you’ll need to define the following properties:
Constant Density Value measured in kg/m3
Specific Heat at Constant Pressure measured in J/K/kg
Thermal Conductivity measured in W/K/m.
References:
MatWeb, LLC. "Material Property Data." MatWeb. https://www.matweb.com/Search/MaterialGroupSearch.aspx.