function PSI = psi_square ( X, Y )

%*****************************************************************************80
%
%% psi_square returns the stream function for square flow.
%
%  Licensing:
%
%    This code is distributed under the GNU LGPL license.
%
%  Modified:
%
%    16 June 2020
%
%  Input:
%
%    real X(nr,nc), Y(nr,nc): the node coordinates.
%
%  Output:
%
%    real PSI(nr,nc): the stream function.
%
  PSI = - X.^2 .* ( 1.0 - X ).^2 .* Y.^2 .* ( 1.0 - Y ).^2;

  return
end

