4th order ODE, 4 boundary conditions

5 vues (au cours des 30 derniers jours)
Connor Thompson
Connor Thompson le 11 Juil 2022
I have a 4th order ODE, with 4 boundary conditions.
The ODE problem is
y''''(x) = y(x)*y'''(x) - y'(x)*y''(x)
With the 4 boundary conditions:
y(0) = 0.1, y(1) = 0, y'(0) = 0, y'(1) = 0.
I started off my code by writing the ODE as a system of first order ODE's,
function dydx = ab(x,y)
dydx = zeros(4,1);
dydx(1) = y(2);
dydx(2) = y(3);
dydx(3) = y(4);
dydx(4) = y(1)*y(4) - y(2)*y(3);
Then defining the 4 boundary conditions,
function res = bc4(ya,yb)
res = [ya(1)-0.1; yb(1); ya(2); yb(2)];
Followed by:
solinit = bvpinit(linspace(0,0.05,1), [1, 0]);
sol = bvp4c(@ab, @bc4,solinit);
x = linspace(0,1);
y = deval(sol.x);
plot(x,y(1,:));
However, I already get an error on the second line,
"Not enough input arguements. Erron in __ (line 3)
dydx = y(2)"
Any ideas on what is going wrong?

Réponses (2)

Torsten
Torsten le 11 Juil 2022
Modifié(e) : Torsten le 11 Juil 2022
%solinit = bvpinit(linspace(0,0.05,1), [1, 0]);
solinit = bvpinit(0:0.05:1, [1, 0,0,0]);
sol = bvp4c(@ab, @bc4,solinit);
%x = linspace(0,1);
%y = deval(sol.x);
%plot(x,y(1,:));
plot(sol.x,[sol.y(1,:);sol.y(2,:)]);
function dydx = ab(x,y)
dydx = zeros(4,1);
dydx(1) = y(2);
dydx(2) = y(3);
dydx(3) = y(4);
dydx(4) = y(1)*y(4) - y(2)*y(3);
end
function res = bc4(ya,yb)
res = [ya(1)-0.1; yb(1); ya(2); yb(2)];
end

MOSLI KARIM
MOSLI KARIM le 16 Fév 2023
%%
function answer_matlab
clc
clear all
close all
format long
mesh=20;
x=linspace(0,1,mesh)
solinit=bvpinit(linspace(0,1,10),[0.1 ;0 ;0; 0])
sol=bvp4c(@fct,@bc,solinit)
y=deval(sol,x)
figure(1)
hold on
plot(x,y(1,:))
function dxdy=fct(x,y)
dxdy=[y(2);y(3);y(4);y(1)*y(4)-y(2)*y(3) ];
end
function res=bc(ya,yb)
res=[ya(1)-0.1
yb(1)
ya(2)
yb(2)
];
end
end

Catégories

En savoir plus sur Numerical Integration and Differential Equations dans Help Center et File Exchange

Community Treasure Hunt

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

Start Hunting!

Translated by