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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
Source term
The source term can represent body forces or flow resistance forces to model different physical phenomena.
Cavities
Understand how the flow solver computes reference temperatures differently for enclosed cavities and cavities with openings.

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.
  - Source term
    The source term can represent body forces or flow resistance forces to model different physical phenomena.
    - Buoyancy force
      For buoyancy-driven flows, the flow solver uses the full gravity model for multiphase and multicomponent flows or flows with density differences from non-temperature sources, and the Boussinesq model for flows with small temperature-induced density variations.
    - Cavities
      Understand how the flow solver computes reference temperatures differently for enclosed cavities and cavities with openings.
    - Flow resistance through porous materials
      Learn how the flow solver models flow resistance through isotropic and orthotropic porous materials.
  - 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.

Cavities

Understand how the flow solver computes reference temperatures differently for enclosed cavities and cavities with openings.

Enclosed cavities

In an enclosed cavity, with no communication of pressure level to the outside, T_r is arbitrary: the temperature and velocity fields are independent of reference temperature. The pressure reacts with differing linear variations superimposed on an unchanging field. In effect, different T_r values only create different hydrostatic pressure variations in P^*. T_r is selected such that the total buoyancy force summed over the whole domain is zero.

The buoyancy source term is

This code reference temperature is computed internally to minimize the summed effect of the buoyancy term:

where V is the volume of fluid, and the sums are over the whole domain. Substituting this expression for T_r into the equation for the buoyancy source term and then summing the result over the whole domain gives a zero buoyancy force.

Cavities with openings

Consider a simple cavity, open to a large domain at the top and the bottom, and heated from its internal walls. Physically, natural convection results with fluid entering through the bottom and heated fluid leaving through the top.

If T_r is computed from the reference temperature equation for enclosed cavities in a model with cavities open to external fluid domains then, by design, there will be a zero total buoyancy force and with the zero force from the P^* pressure boundary conditions there will be no net movement of the fluid through the cavity. Because of this potential problem, the reference temperature for open cavities T_r is taken as the maximum of all the openings temperatures in the enclosure, given by: