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# problem about ODE (Rayleigh-Plesset Equation) error in ode15s

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Ahmed Mehrem on 23 May 2013
Now , i simulate Rayleigh-Plesset Equation and i did the Function which is
function f = RP(t,y)
p_ref = 1e5; %reference pressure Pa
rho = 1e3; %density of fluid kg/m3
g = 1; %polytropic exponent Unitless
R0=0.0005;
f= [y(2);( pulse(t) - p_ref + p_ref*(R0./y(1))^(3*g) )/(rho*y(1))-(1.5*y(2)^2/(y(1)))];
return;
and this is the Pulse code
function z=pulse(t)
global A w t0 sigma env%accept globals.
z = A*sin(w*t); %no window
return
and this is the Solution
[T,R] = ode15s('RP',[0 3e-8],[1e-6 70]);
plot(T,R(:,1)),xlabel('time'),ylabel('Radius')
no i have this problem
??? Error using ==> odearguments at 103
RP returns a vector of length 1, but the length of initial conditions vector is 2. The
vector returned by RP and the initial conditions vector must have the same number of
elements.
Error in ==> ode15s at 227
[neq, tspan, ntspan, next, t0, tfinal, tdir, y0, f0, odeArgs, odeFcn, ...
Error in ==> solv at 6
[T,R] = ode15s('RP',[0 3e-1],[1e-6 70]);
what can i do ? i need a help i got the Signal simulation before but i did dome change , now i cant return
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### Answers (2)

Navid on 30 Jul 2013
I am using ode45 to solve this equation. I am considering everything such as surface tension, viscosity, and acoustic pressure. I will get good results when the oscillations are stable. And by stable I mean there is no sudden collapses and bubble oscillation is not huge comparing to its initial radius. But when the oscillations become huge, and oscillations get transient, I am not getting good results. bubble radius reaches to very very small values but again rebounds to huge values. Any experience of suggestions? Is it better to use another ODE solver?
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Ahmed Mehrem on 4 Aug 2013
Thank you ,i find the solution of this problem. and you are Right i am also used ode45 and the solution is very good and nearly the same with Experimental Part

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bym on 23 May 2013
check your call to ode15s
[T,R] = ode15s('RP',[0 3e-8],[1e-6 70]); %your code
what does the following give you?
[T,R] = ode15s(@RP,[0 3e-8],[1e-6 70]);
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Ahmed Mehrem on 24 May 2013
the same problem :(

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