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    NDSolve`FEM`

    InitializeBoundaryConditions::femibcnd

    Details

    • This message is generated in case no DirichletCondition or non-Robin-type NeumannValue is specified for a dependent variable.
    • Off[message] switches off the message; On[message] switches it on. For example: Off[InitializeBoundaryConditions::femibcnd].

    Examples

    Basic Examples  (2)

    Exclusively specifying Neumann boundary conditions for stationary PDEs may result in a non-unique solution. In some cases, the system may not be solvable at all:

    Wolfram Language code: NDSolveValue[Subsuperscript[∇, {x, y}, 2]u[x, y] == Sin[x y], u, {x, y}∈Disk[]]
    Wolfram Language code: Plot3D[%[x, y], {x, y}∈Disk[]]

    Specifying a Robin boundary condition is sufficient:

    Wolfram Language code: NDSolveValue[Subsuperscript[∇, {x, y}, 2]u[x, y] == NeumannValue[3u[x, y] + Sin[x y], True], u, {x, y}∈Disk[]]
    Wolfram Language code: Plot3D[%[x, y], {x, y}∈Disk[]]

    This message can be generated by other functions:

    Wolfram Language code: Needs["NDSolve`FEM`"] vd = NDSolve`VariableData[{"DependentVariables", "Space"} -> {{u}, {x, y}}]; sd = NDSolve`SolutionData[{"Space"} -> {ToElementMesh[Rectangle[]]}];
    Wolfram Language code: InitializeBoundaryConditions[vd, sd, {{}}]