SparseLizard/examples/electromagnetic-waveguide-3d/main.cpp

// This code simulates the steady-state electromagnetic waves in a cross-shaped 
// 3D waveguide made of a perfect conductor.


#include "sparselizardbase.h"


using namespace mathop;

void sparselizard(void)
{	
    // The domain regions as defined in 'waveguide3D.geo':
    int left = 1, skin = 2, wholedomain = 3;

    mesh mymesh("waveguide3D.msh");

    // Edge shape functions 'hcurl' for the electric field E.
    // Fields x, y and z are the x, y and z coordinate fields.
    field E("hcurl"), x("x"), y("y"), z("z");

    // Use interpolation order 2 on the whole domain:
    E.setorder(wholedomain, 2);
    
    // The cutoff frequency for a 0.2x0.2 m^2 cross section is freq = 1.06 GHz in theory. 
    // With this code and a fine enough mesh you will get the same value.
    double freq = 1.2e9, c = 3e8, pi = 3.14159, k = 2*pi*freq/c;
    
    // The waveguide is a perfect conductor. We thus force all
    // tangential components of E to 0 on the waveguide skin.
    E.setconstraint(skin);
    // We force an electric field in the z direction on region 'left'
    // that is 0 on the exterior of 'left' and 1 in the center.
    E.setconstraint(left, cos(y/0.2*pi)* cos(z/0.2*pi)* array3x1(0,0,1));

    formulation maxwell;
    
    // This is the weak formulation for electromagnetic waves:
    maxwell += integral(wholedomain, -curl(dof(E))*curl(tf(E)) + k*k*dof(E)*tf(E));
    
    // Generate and solve the algebraic system Ax = b:
    maxwell.generate();
    vec solE = solve(maxwell.A(), maxwell.b());
    
    // Transfer the data from the solution vector to field E:
    E.setdata(wholedomain, solE);    
    // Save the electric field E with an order 2 interpolation:
    E.write(wholedomain, "E.pos", 2);
    
    // Code validation line. Can be removed.
    std::cout << ((abs(E)*curl(E)).integrate(wholedomain, 5) < 6.9398e-07 && (abs(E)*curl(E)).integrate(wholedomain, 5) > 6.93978e-07);
}

int main(void)
{	
    SlepcInitialize(0,{},0,0);

    sparselizard();

    SlepcFinalize();

    return 0;
}