view +sbp/+implementations/d2_variable_2.m @ 577:e45c9b56d50d feature/grids

Add an Empty grid class The need turned up for the flexural code when we may or may not have a grid for the open water and want to plot that solution. In case there is no open water we need an empty grid to plot the empty gridfunction against to avoid errors.
author Jonatan Werpers <jonatan@werpers.com>
date Thu, 07 Sep 2017 09:16:12 +0200
parents ded4156e53e2
children b758d1cf4c8e
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line source

function [H, HI, D1, D2, e_l, e_r, d1_l, d1_r] = d2_variable_2(m,h)

    BP = 1;
    if(m<2*BP)
        error(['Operator requires at least ' num2str(2*BP) ' grid points']);
    end

    % Norm
    Hv = ones(m,1);
    Hv(1) = 1/2;
    Hv(m:m) = 1/2;
    Hv = h*Hv;
    H = spdiag(Hv, 0);
    HI = spdiag(1./Hv, 0);


    % Boundary operators
    e_l = sparse(m,1);
    e_l(1) = 1;
    e_r = rot90(e_l, 2);

    d1_l = sparse(m,1);
    d1_l(1:3) = 1/h*[-3/2 2 -1/2];
    d1_r = -rot90(d1_l, 2);

    % D1 operator
    diags   = -1:1;
    stencil = [-1/2 0 1/2];
    D1 = stripeMatrix(stencil, diags, m);
    
    D1(1,1)=-1;D1(1,2)=1;D1(m,m-1)=-1;D1(m,m)=1;
    D1(m,m-1)=-1;D1(m,m)=1;
    D1=D1/h;
    %Q=H*D1 + 1/2*(e_1*e_1') - 1/2*(e_m*e_m');


    M=sparse(m,m);

    scheme_width = 3;
    scheme_radius = (scheme_width-1)/2;
    r = (1+scheme_radius):(m-scheme_radius);

    function D2 = D2_fun(c)

        Mm1 = -c(r-1)/2 - c(r)/2;
        M0  =  c(r-1)/2 + c(r)   + c(r+1)/2;
        Mp1 =            -c(r)/2 - c(r+1)/2;

        M(r,:) = spdiags([Mm1 M0 Mp1],0:2*scheme_radius,length(r),m);


        M(1:2,1:2)=[c(1)/2 + c(2)/2 -c(1)/2 - c(2)/2; -c(1)/2 - c(2)/2 c(1)/2 + c(2) + c(3)/2;];
        M(m-1:m,m-1:m)=[c(m-2)/2 + c(m-1) + c(m)/2 -c(m-1)/2 - c(m)/2; -c(m-1)/2 - c(m)/2 c(m-1)/2 + c(m)/2;];
        M=M/h;

        D2=HI*(-M-c(1)*e_l*d1_l'+c(m)*e_r*d1_r');
    end
    D2 = @D2_fun;
end