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Flow Solver
Contains flow solver related guides, such as the reference and API guides.
Flow solver reference
Insert short description here
Governing equations
A model can be comprised of multiple flow enclosures. Each enclosure is a separate group of three-dimensional elements that form a separate fluid domain from the remaining geometry. The physical scales of each enclosure, such as the length scale, time scale, pressure, and temperature are independent of the other enclosures. The flow solver solves governing equations separately for each flow enclosure.
Scalar equation
The flow solver addresses general scalar equations, defining key variables and terms for transient, convective, and diffusion processes. It includes modeling passive scalars and applications such as gas mixtures and humidity.
Temperature dependent diffusion coefficient
The flow solver supports temperature-dependent diffusion coefficient in active and passive scalar equations.

Flow Solver
Contains flow solver related guides, such as the reference and API guides.
- Flow solver guides
  Maya HTT's flow solver is included and distributed with Simcenter 3D and Simcenter Femap. This page contains links to flow solver guides, which help you understand how the flow solver works.
- Flow solver reference
  Insert short description here
  - Introduction
    The flow solver computes a solution to the non-linear, partial differential equations for the conservation of mass, momentum, energy, and general scalars in general complex 3D geometries. It uses an element-based finite volume method and iterative Krylov methods to discretize and solve the governing equations.
  - Nomenclature
    The nomenclature table offers a description and sample units or constant values of the variables used in the Flow Solver Reference Manual.
  - Governing equations
    A model can be comprised of multiple flow enclosures. Each enclosure is a separate group of three-dimensional elements that form a separate fluid domain from the remaining geometry. The physical scales of each enclosure, such as the length scale, time scale, pressure, and temperature are independent of the other enclosures. The flow solver solves governing equations separately for each flow enclosure.
    - Mass and momentum equations
      The flow solver solves conservation equations for mass and momentum for general flow.
    - Energy equation
      The instantaneous total energy equation describes the conservation of energy in fluid dynamics, accounting for internal energy, velocity, heat flux, and heat generation.
    - Scalar equation
      The flow solver addresses general scalar equations, defining key variables and terms for transient, convective, and diffusion processes. It includes modeling passive scalars and applications such as gas mixtures and humidity.
      - Temperature dependent diffusion coefficient
        The flow solver supports temperature-dependent diffusion coefficient in active and passive scalar equations.
    - Equations of state
      An equation of state is a constitutive equation which provides a mathematical relationship between thermodynamic state variables for a given material.
  - Source term
    The source term can represent body forces or flow resistance forces to model different physical phenomena.
  - Turbulence models
    In the flow solver, the flow field can be solved as laminar or as turbulent using governing equations.
  - Boundary conditions
    This section outlines different boundary conditions supported by the flow solver and the associated considerations.
  - Modeling a gas mixture
    The flow solver uses the scalar equation to model a gas mixed in any proportion with the main gas. The software supports up to five gases in the mixture. All gases are assumed to behave as ideal gases using the ideal gas law.
  - Modeling humidity
    The flow solver uses the gas mixture scalar equation to model humidity that is defined as a mixture of water vapor in air.
  - Modeling non-Newtonian fluid
  - Modeling particle tracking
    The following section describes the equations and forces that model particle trajectories, including treatment and effects of boundary conditions
  - Modeling fluid structure interaction
    Fluid structure interaction (FSI) computations account for motion or deformation of the solid structure boundaries that are interacting with the adjacent fluid flow. The flow solver handles both transient and static fluid structure interactions.
  - Discretization
    The following section describes the discretization methods used by the flow solver to discretize the governing equations.
  - Solver numerical methods
    The following section describes numerical methods used by the flow solver such as the linear equation solution, which acts as a preconditioning method to the basic iterative algorithm, and other solver methods, such as Krylov methods.
  - Flow solver files
    The following table describes the flow solver files, which are written in the run directory during the solving process.
  - Flow solver bibliography
    The following bibliography lists all sources used to explain how the flow solver works.
- Flow solver flowcharts
  This section consists of flowcharts that illustrate the methodology of the flow solver when you run a simple steady-state or transient simulation, and does not cover all features and situations. It also highlights how the flow solver is coupled to the thermal solver for a simple steady-state or transient coupled thermal-flow simulation.

Temperature dependent diffusion coefficient

The flow solver supports temperature-dependent diffusion coefficient in active and passive scalar equations.

To use this functionality, do the following before you run your simulation:

Add the following line in the user.prm file.
```
VARIABLE_MOLECULAR_DIFFUSION_COEFFICIENT = TRUE
```
For more information on the user.prm file, see Flow solver files.

Specify the table for the molecular diffusion coefficient.

You specify the table in the flow.vdc file, which you create using a text editor in your run directory. The following table lists the field values that you need to specify in the flow.vdc file and indicates the values used in the example below:


Field	Value	Description	Value from example
S	int	The number of tables	1
Name_S	char	The name of the affected scalar S	Carbon_Dioxide_Gas
N	int	Length of the table	8
T_0 D_0	double	Temperature, T_0, and molecular diffusion coefficient, D_0	0.00000 14.00000
...	...	...	...
T_N D_N	double	Temperature, T_N, and molecular diffusion coefficient, D_N	50.00000 19.00000

The temperature units must be consistent with the solution units.

Example

1
Carbon_Dioxide_Gas
8
  0.00000    14.00000
  7.14286    14.71429
 14.28571    15.42857
 21.42857    16.14286
 28.57143    16.85714
 35.71429    17.57143
 42.85714    18.28571
 50.00000    19.00000