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Flow Solver
Contains flow solver related guides, such as the reference and API guides.
Flow solver reference
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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.

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
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  - 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.
  - 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.

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.

Transient fluid structure interaction

The flow solver uses the arbitrary-Lagrange-Eulerian (ALE) form to discretize the governing equations for FSI modeling. Integration of the governing Navier-Stokes equations in the ALE form over a moving control volume V(t) [57] is given as:

where:

U is a conserved quantity (mass, momentum and energy).
F is the convective flux term.
G is the viscous flux term.
∂V(t) is the control volume boundary.
S is the control volume boundary surface.
is the velocity of the control volume boundary.
is the normal vector to the control volume boundary.
t is the time.

The discrete form of the governing equations in the ALE form is given as:

where the discrete convective flux in the ALE form is:

and the discrete viscous flux is:

and x(t) are the control volume boundary positions.

The following source term is added to the right hand side of the discrete form of the governing equation, to satisfy the geometric conservation law, by assuming that the state of U is an exact constant solution for the governing equation.

Static fluid structure interaction

The flow solver uses the following discrete form of ordinary differential equation (ODE) to compute FSI modeling with static mesh.

where:

U is a conserved quantity (mass, momentum and energy).
is the grid face velocity.
V is the control volume.

The grid face velocity is defined as:

where is the surface normal.

In static FSI modeling, the velocity of the control volume boundary, , is zero and the control volume depends on the control volume grid coordinates, x(t) as:

Knowing the grid coordinate positions and velocities as a function of time, for a first order time accurate scheme, the flow solver uses the following discretization of the ODE for the static FSI modeling:

where Δt = t^{n + 1} - tⁿ is the current time step.