How to solve 2nd order ODE inequality ?
2 vues (au cours des 30 derniers jours)
Afficher commentaires plus anciens
Hello to all,
I am trying to numerically solve a 2nd order ODE inequality of the form : y"(x) + y'(x)*a(x) + y(x)*b(x) <= 0 ( a(x) and b(x) are spatially varying parameters). Also, my solution y(x) must be > 0 for all x.
It is possible to solve a similar problem in Matlab ( y"(x) + y'(x)*a(x) + y(x)*b(x) = 0 ) using ode solvers, however, I am uncapable of enforcing the above constraints (ODE<=0 and y(x)>0).
Are toolboxes like Yalmip useful in solving such problems?
Thanks in advance
Firas
3 commentaires
Réponses (1)
Tamir Suliman
le 29 Nov 2016
Modifié(e) : Tamir Suliman
le 29 Nov 2016
lets assume that we have the equations:
y''+a*y'+b*y<=0 a , b are f(x) where x>0
let y(x)=Y1 and dy(x)/dx = Y2
dY1/dx= Y2 dY2/dx= -a*Y2-b*Y1
lets assume a =3 b =4 then the program code would be similar to
a=3;b=4;
syms y(x)
[V] = odeToVectorField(diff(y, 2) == -a*diff(y) -b* y);
M = matlabFunction(V,'vars', {'x','Y'})
sol = ode45(M,[0 20],[2 0]);
fplot(@(x)deval(sol,x,1), [0, 20])
if statement would be sufficient to add the constraints
2 commentaires
Tamir Suliman
le 2 Déc 2016
Modifié(e) : Tamir Suliman
le 2 Déc 2016
if sol > 0 then code please do some thing for me here
else if sol < 0 then code please do some thing for me else code
end
Voir également
Catégories
En savoir plus sur Ordinary Differential Equations dans Help Center et File Exchange
Produits
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!