Mercurial > repos > public > sbplib
view +sbp/+implementations/d4_compatible_2.m @ 1037:2d7ba44340d0 feature/burgers1d
Pass scheme specific parameters as cell array. This will enabale constructDiffOps to be more general. In addition, allow for schemes returning function handles as diffOps, which is currently how non-linear schemes such as Burgers1d are implemented.
author | Vidar Stiernström <vidar.stiernstrom@it.uu.se> |
---|---|
date | Fri, 18 Jan 2019 09:02:02 +0100 |
parents | f7ac3cd6eeaa |
children |
line wrap: on
line source
function [H, HI, D1, D4, e_1, e_m, M4, Q, S2_1, S2_m,... S3_1, S3_m, S_1, S_m] = d4_compatible_2(m,h) %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%% 4:de ordn. SBP Finita differens %%% %%% operatorer framtagna av Ken Mattsson %%% %%% %%% %%% 6 randpunkter, diagonal norm %%% %%% %%% %%% Datum: 2013-11-11 %%% %%% %%% %%% %%% %%% H (Normen) %%% %%% D1 (approx f?rsta derivatan) %%% %%% D2 (approx andra derivatan) %%% %%% D3 (approx tredje derivatan) %%% %%% D2 (approx fj?rde derivatan) %%% %%% %%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % M?ste ange antal punkter (m) och stegl?ngd (h) % Notera att dessa opetratorer ?r framtagna f?r att anv?ndas n?r % vi har 3de och 4de derivator i v?r PDE % I annat fall anv?nd de "traditionella" som har noggrannare % randsplutningar f?r D1 och D2 % Vi b?rjar med normen. Notera att alla SBP operatorer delar samma norm, % vilket ?r n?dv?ndigt f?r stabilitet BP = 4; if(m<2*BP) error(['Operator requires at least ' num2str(2*BP) ' grid points']); end H=speye(m,m);H(1,1)=1/2;H(m,m)=1/2; H=H*h; HI=inv(H); % First derivative SBP operator, 1st order accurate at first 6 boundary points q1=1/2; % Q=q1*(diag(ones(m-1,1),1)-diag(ones(m-1,1),-1)); stencil = [-q1,0,q1]; d = (length(stencil)-1)/2; diags = -d:d; Q = stripeMatrix(stencil, diags, m); %Q=(-1/12*diag(ones(m-2,1),2)+8/12*diag(ones(m-1,1),1)-8/12*diag(ones(m-1,1),-1)+1/12*diag(ones(m-2,1),-2)); e_1=sparse(m,1);e_1(1)=1; e_m=sparse(m,1);e_m(m)=1; D1=H\(Q-1/2*(e_1*e_1')+1/2*(e_m*e_m')) ; %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % Second derivative, 1st order accurate at first 6 boundary points % m1=-1;m0=2; % % M=m1*(diag(ones(m-1,1),1)+diag(ones(m-1,1),-1))+m0*diag(ones(m,1),0);M(1,1)=1;M(m,m)=1; % stencil = [m2,m1,m0,m1,m2]; % d = (length(stencil)-1)/2; % diags = -d:d; % M = stripeMatrix(stencil, diags, m); % M=M/h; S_U=[-1 1]/h; S_1=sparse(1,m); S_1(1:2)=S_U; S_m=sparse(1,m); S_m(m-1:m)=fliplr(-S_U); % D2=H\(-M-e_1*S_1+e_m*S_m); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % Third derivative, 1st order accurate at first 6 boundary points % q2=1/2;q1=-1; % % Q3=q2*(diag(ones(m-2,1),2)-diag(ones(m-2,1),-2))+q1*(diag(ones(m-1,1),1)-diag(ones(m-1,1),-1)); % stencil = [-q2,-q1,0,q1,q2]; % d = (length(stencil)-1)/2; % diags = -d:d; % Q3 = stripeMatrix(stencil, diags, m); %QQ3=(-1/8*diag(ones(m-3,1),3) + 1*diag(ones(m-2,1),2) - 13/8*diag(ones(m-1,1),1) +13/8*diag(ones(m-1,1),-1) -1*diag(ones(m-2,1),-2) + 1/8*diag(ones(m-3,1),-3)); % Q3_U = [0 -0.2e1 / 0.5e1 0.3e1 / 0.10e2 0.1e1 / 0.10e2; 0.2e1 / 0.5e1 0 -0.7e1 / 0.10e2 0.3e1 / 0.10e2; -0.3e1 / 0.10e2 0.7e1 / 0.10e2 0 -0.9e1 / 0.10e2; -0.1e1 / 0.10e2 -0.3e1 / 0.10e2 0.9e1 / 0.10e2 0;]; % Q3(1:4,1:4)=Q3_U; % Q3(m-3:m,m-3:m)=rot90( -Q3_U ,2 ); % Q3=Q3/h^2; S2_U=[1 -2 1;]/h^2; S2_1=sparse(1,m); S2_1(1:3)=S2_U; S2_m=sparse(1,m); S2_m(m-2:m)=fliplr(S2_U); % D3=H\(Q3 - e_1*S2_1 + e_m*S2_m +1/2*(S_1'*S_1) -1/2*(S_m'*S_m) ) ; % Fourth derivative, 0th order accurate at first 6 boundary points (still % yield 4th order convergence if stable: for example u_tt=-u_xxxx m2=1;m1=-4;m0=6; M4=m2*(diag(ones(m-2,1),2)+diag(ones(m-2,1),-2))+m1*(diag(ones(m-1,1),1)+diag(ones(m-1,1),-1))+m0*diag(ones(m,1),0); %M4=(-1/6*(diag(ones(m-3,1),3)+diag(ones(m-3,1),-3) ) + 2*(diag(ones(m-2,1),2)+diag(ones(m-2,1),-2)) -13/2*(diag(ones(m-1,1),1)+diag(ones(m-1,1),-1)) + 28/3*diag(ones(m,1),0)); M4_U=[0.4e1 / 0.5e1 -0.7e1 / 0.5e1 0.2e1 / 0.5e1 0.1e1 / 0.5e1; -0.7e1 / 0.5e1 0.16e2 / 0.5e1 -0.11e2 / 0.5e1 0.2e1 / 0.5e1; 0.2e1 / 0.5e1 -0.11e2 / 0.5e1 0.21e2 / 0.5e1 -0.17e2 / 0.5e1; 0.1e1 / 0.5e1 0.2e1 / 0.5e1 -0.17e2 / 0.5e1 0.29e2 / 0.5e1;]; M4(1:4,1:4)=M4_U; M4(m-3:m,m-3:m)=rot90( M4_U ,2 ); M4=M4/h^3; S3_U=[-1 3 -3 1;]/h^3; S3_1=sparse(1,m); S3_1(1:4)=S3_U; S3_m=sparse(1,m); S3_m(m-3:m)=fliplr(-S3_U); D4=H\(M4-e_1*S3_1+e_m*S3_m + S_1'*S2_1-S_m'*S2_m); S_1 = S_1'; S_m = S_m'; S2_1 = S2_1'; S2_m = S2_m'; S3_1 = S3_1'; S3_m = S3_m'; % L=h*(m-1); % x1=linspace(0,L,m)'; % x2=x1.^2/fac(2); % x3=x1.^3/fac(3); % x4=x1.^4/fac(4); % x5=x1.^5/fac(5); % x0=x1.^0/fac(1); end