Solid Objects#

Solid objects are finite auxiliary objects that can be stationary or in motion. Rotating impellers, sliding surfaces, and finite stoppers are examples of solid objects. The main differences between them and floating walls are: 1. floating wall is a plane, while a solid object can be either a volume or a surface 2. floating wall is infinite, while solid object is finite 3. floating wall is stationary while solid object may be stationary or moving.

Note

At the moment, solid objects in Lethe have to be defined using triangular (simplex) meshes. Only triangular 2D meshes of 3D surfaces in simulations are currently supported, meaning that any other meshes will not work.

This subsection explains the solid objects information. First of all, the number of solids is specified. Then, for each solid object, we need a mesh subsection. In these subsections, the type, initial refinement, and other properties of the objects are defined. Note that currently, only solid surfaces, meaning dim=2, spacedim=3 meshes, are usable. The simplex parameter must be set to true for all solid surfaces. For more information on mesh subsection, visit CFD mesh

subsection solid objects
  subsection solid surfaces
    # Total number of solid surfaces
    set number of solids  = 1
    subsection solid object 0
      subsection mesh
        set type                   = gmsh
        set file name              = none
        set simplex                = true
        set initial refinement     = 0
        set initial rotation axis  = 1, 0, 0
        set initial rotation angle = 0
        set initial translation    = 0, 0, 0
      end

      subsection translational velocity
        set Function expression = 0 ; 0 ; 0
      end

      subsection angular velocity
        set Function expression = 0 ; 0 ; 0
      end

      set center of rotation    = 0., 0., 0.
      set output solid object = true
    end
  end
end

  • The number of solids parameter defines the total number of solid surfaces used during the simulation.

  • For each solid object, we need a separate subsections (for instance subsection solid object 0) in which the information of the solid surface 0 (type, file name, initial refinement, initial translation, initial rotation axis, initial rotation angle) is defined. Each component of the initial translation and of the initial rotation axis parameters represent the x, y and z axes. The rotation is applied before the translation.

  • In the subsection translational velocity, we define the translational velocity function of the solid object.

  • In the subsection angular velocity, we define the angular velocity function of the solid object.

  • The center of rotation defines the center of rotation of the solid object (in the case of rotational motion) in the x, y and z directions. This center of rotation will move according to the translational velocity parameter.

  • The output solid object defines if we want an output file to be generated for the solid object at every output time step.