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Thread: Edge degrees of freedom

  1. #1
    Junior Member
    Join Date
    Apr 2021

    Edge degrees of freedom


    Is it possible to use a variable that has more than one degrees of freedom per edge? By this I do not mean edge basic functions of the second degree.

    For example, is it possible to use a weak formulation containing E and H vector fields (where E represents the electric field vector and H represents the magnetic field vector) such that both vector fields are approximated by edge elements.

    I guess it would then look like this in a SIF file:
    Solver 1
    Variable = Field[ E re:1 E im:1 H re:1 H im:1] !...harmonic case
    Variable DOFs= 4
    Element = "n:0 e:1"

    I am trying to develop similar formulation in the 3D case, but the solver does not seem to know that the variable has 4 edge degrees of freedom, i.e. real and imag part for both E and H.

    For example:
    When I print final solution for an element that is a tetrahedron (so it has 6 edges), by using the GetLocalSolution() subroutine, the solutuion vector SOL has only 14 values ​​instead of 24 values ​​(4 EdgeDofs for each of the 6 edges of the tetrahedron).

    It seems to me that it offers me real an imaginary part for each of the 6 edges plus 2 strange values (maybe some unwanted nodal Dofs), from which it follows:
    2 * 6Edges + 2dofs = 14 values ​​in SOL.

    Thanks and best regards

  2. #2
    Junior Member
    Join Date
    Sep 2021
    Hi there, good question. Understanding the meaning of degrees of freedom is critical to selecting the appropriate constraints to define a mechanism’s ability to move. A completely unconstrained body has six degrees of freedom, three translational and three rotational. Each constraint restricts movement in a specific way. Before you select a pre-defined constraint set to apply to your model, you should know which type of movement you want to restrict. Better to ask experts for that.


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