Constrain Stasis#

This subsection is used to define temperature-dependent solid domains within a defined fluid. Homogenous constraints are applied on velocity degrees of freedom (DoFs) of cells found within the prescribed temperature range to mimic a solid.

Attention

In order to use this feature, the heat transfer physic must be enabled (true) in the Multiphysics subsection.

The subsection with default parameters goes as follows:

subsection constrain stasis
  set enable                               = false
  set enable domain restriction with plane = false
  # In 2D
  set restriction plane point              = 0.0, 0.0
  set restriction plane normal vector      = 0.0, 0.0
  # In 3D
  set restriction plane point              = 0.0, 0.0, 0.0
  set restriction plane normal vector      = 0.0, 0.0, 0.0
  set number of constraints                = 0
  subsection constraint 0
    set fluid id                 = 0
    set phase fraction tolerance = 1e-4
    set min temperature          = -999.0
    set max temperature          = 0.0
  end
end

  • The enable parameter is set to true when at least one temperature-dependent stasis constraint should be applied.

  • The enable domain restriction with plane parameter is set to true when it is desired to reduce the constrained domain using a plane in addition to the temperature range. The plane cuts the domain in two subdomains. Only cells in the subdomain in the opposite direction to the normal vector can be constrained.

  • The restriction plane point parameter is a point on the plane.

  • The restriction plane normal vector parameter is an outward-pointing normal vector of the plane. This vector points to the side of the plane that contains cells to constrain.

  • The number of constraints parameter is an integer representing the number of constraints that will be applied. It is used in multiphase (VOF) simulations to apply different constraints to each fluid. Only one constraint per fluid can be imposed. Each constraint comes with its own subsection (starting with number 0) containing its own set of parameters as detailed below.

    • The fluid id parameter is an integer representing the fluid on which the current constraint should be applied.

    • The phase fraction tolerance parameter is an absolute tolerance on the filtered phase fraction \((\phi')\) used in conjunction with VOF simulations (see Volume of Fluid (Multiphase Flow) subsection) to select the cells on which the constraint is applied. For example, if a phase fraction tolerance of \(10^{-4}\) is specified for a constraint on a fluid of fluid id = 1, cells with \(\phi' \in [0.9999,1.0001]\) are considered as the cells of interest. Note that if the phase fraction filter is disabled, the tolerance will be applied on the solved phase fraction field \((\phi)\).

    • The min temperature parameter is a double representing the minimum temperature value for a cell to be considered a solid \([\Theta]\).

    • The max temperature parameter is a double representing the maximum temperature value for a cell to be considered a solid \([\Theta]\).