Error with Dirichlet BC in C++ implementation

Question

Hello,

I am trying to modifiy the undocumented elastodynamics [demo][1] which deals with a nonlinear weak form, to a linear weak form. However, post editing, when I generated and ran the demo file, it gives the following error:

Error: Unable to create Dirichlet boundary condition.
*** Reason: Expecting a vector-valued boundary value but given function is scalar.
*** Where: This error was encountered inside DirichletBC.cpp.

The DBC has been defined as:

  DirichletBC bcl(V, S, left);
  DirichletBC bct(V, c, top);
  DirichletBC bcr(V, c, right);
  DirichletBC bcb(V, c, bottom);

  // Collect all DBC in one container 'bcs'
  // std::vector<const DirichletBC*> bcs = {{&bcl, &bcr, &bcb, &bct}};
  std::vector<const DirichletBC*> bcs;
  bcs.push_back(&bcl); bcs.push_back(&bcr); bcs.push_back(&bcb); bcs.push_back(&bct);

Answer 1

Hi,
the error is encountered inside of the Source class (you have not defined the dimension of the Source objects and in consequence by default is taken as 1).

To solve your problem change the Source to:

class Source : public Expression
{
public:

  //Constructor
  Source() : Expression(2), t(0) {}

  // Evaluate incoming wave
  void eval(Array<double>& values, const Array<double>& x) const
  {
  values[0] = sin(2.0*DOLFIN_PI*5.0*t);
  values[1] = 0.0;
  }

  //Current time
  double t;
};

Comments

Thanks a lot Hernan!