ODE15s with non-constant Jacobian

2 Ansichten (letzte 30 Tage)
Berry
Berry am 2 Aug. 2022
Kommentiert: Berry am 3 Aug. 2022
Hi everyone,
i want to solve an ODE by using the Jacobian, that is not constant:
options = odeset( 'Jacobian' , @(t,x)J(u_int, deltaZ, Nz, cFeed), 'RelTol',1e-8, 'AbsTol',1e-8);
[t,V] = ode15s(@(t,v)odeTest(t,v), tspan, v0, options);
function dfdx = J(u_int, deltaZ, Nz, cFeed)
x = sym('x' , [1 Nz+4]);
f1 = (-u_int .* (x(1)^2 - cFeed) ./ deltaZ );
f2 = (-u_int .* (x(2:Nz+4) - x(1:Nz+3)) ./ deltaZ );
f = [f1, f2];
J = jacobian(f,x);
dfdx = (J);
end
%% ODE
function dfdt = odeTest(~, vi)
dfdt = zeros(length(vi),1);
%% Variables
u_int = 0.10;
H = 0.20;
Nz = 100;
deltaZ = H/(Nz+4);
cFeed = 10;
x = vi(1:Nz+4);
%% DGL
dfdt(1) = (-u_int .* (x(1)^2 - cFeed) ./ deltaZ );
dfdt(2: Nz+4) = (-u_int .* (x(2:Nz+4) - x(1:Nz+3)) ./ deltaZ );
end
The problem I am facing is following error:
Conversion to logical from sym is not possible.
Error in ode15s (line 405)
if absh * rh > 1
Error in test_jacobi_upwind (line 39)
[t,V] = ode15s(@(t,v)odeTest(t,v), tspan, v0, options);
I can make it work, if the Jacobian is a constant and does not depend on x(i) - but as soon as J is depending on x(i), I am getting errors.
Any help is appreciated.
Best,
M

Akzeptierte Antwort

Torsten
Torsten am 2 Aug. 2022
JacFun = J(u_int, deltaZ, Nz, cFeed);
options = odeset( 'Jacobian' , @(t,x)JacFun(t, x, u_int, deltaZ, Nz, cFeed), 'RelTol',1e-8, 'AbsTol',1e-8);
[t,V] = ode15s(@(t,x)odeTest(t,x,u_int, deltaZ, Nz, cFeed), tspan, v0, options);
function dfdx = J(u_int, deltaZ, Nz, cFeed)
x = sym('x' , [1 Nz+4]);
f1 = (-u_int .* (x(1)^2 - cFeed) ./ deltaZ );
f2 = (-u_int .* (x(2:Nz+4) - x(1:Nz+3)) ./ deltaZ );
f = [f1, f2];
J = jacobian(f,x);
dfdx = matlabFunction(J,'Vars',[t, x, u_int, deltaZ, Nz, cFeed]);
end
function dfdt = odeTest(t, vi, u_int, deltaZ, Nz, cFeed)
dfdt = zeros(length(vi),1);
%% Variables
u_int = 0.10;
H = 0.20;
Nz = 100;
deltaZ = H/(Nz+4);
cFeed = 10;
x = vi(1:Nz+4);
%% DGL
dfdt(1) = (-u_int .* (x(1)^2 - cFeed) ./ deltaZ );
dfdt(2: Nz+4) = (-u_int .* (x(2:Nz+4) - x(1:Nz+3)) ./ deltaZ );
end
  5 Kommentare
Torsten
Torsten am 3 Aug. 2022
I didn't use this options command in my answer:
options = odeset( 'Jacobian' , @(t,x)JacFunc(u_int, deltaZ, Nz, epsilon,cFeed), 'RelTol',1e-8, 'AbsTol',1e-8);
Berry
Berry am 3 Aug. 2022
My mistake! Thank you very much! Everything works fine now.

Melden Sie sich an, um zu kommentieren.

Weitere Antworten (0)

Kategorien

Mehr zu Numerical Integration and Differential Equations finden Sie in Help Center und File Exchange

Produkte


Version

R2022a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by