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Soham Mukherjee edited this page Aug 18, 2017 · 4 revisions

Project Update

To solve a scalar wave equation using space-time discretization of the action.

All the results are computed on a 4x4 Chebyshev grid.

Laplace Equation

To test the implementation of the integration matrix, and then the boundary projection operator by solving the Laplace equation as a test case.

Used two different methods to implement BCs:

Boundary conditions

u[0] = u[-1] = 0

u[:, 0] = u[:, -1] = 1

Lagrange multipliers

Solution

Eigen Values

Boundary projection operator

Here's the solution which looks very wrong: Solution

Eigen Values

Scalar wave equation

Tried to implement BCs using a mixed approach:

  • Dirichlet BCs on three sides using Lagrange multipliers
  • Neumann BCs using the projection operator.

FIXME: However, multiplying the matrix with the projection operator leads to a singular matrix!

Hence, didn't multiply with the projection operator, but kept the 'b' vector intact. Here's the solution, which looks deceptively correct.

Grid size '4 x 4'

Boundary conditions

u(0) = np.exp(-(x)**2.0/2.0*25.0)

\dot(u)(0) = -0.004*x*np.exp(-(x)**2.0/2.0*25.0)

Results

For understanding the motion, look at the plots here.

Spacetime grid

Eigen Values