Error in Ode 45

Question

Francesco Renzulli 2021-1-6

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链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/710238-error-in-ode-45

评论： Star Strider 2021-1-6

采纳的回答： Star Strider

在 MATLAB Online 中打开

I have a probleb solving this ode ODE it gives me the following errors

or too many inputs in the ode45

or Inputs must be floats, namely single or double.

burn_time=100;
Nt=1000;
m_ox=0.7;
t=linspace(0,burn_time,Nt);
m_ox=m_ox.*ones(1,Nt);
Dp_in=0.0005;
rho_fuel=1.9;
L_grain=0.5;
%% Definizione regression rate
a=0.007;
b=0.67;
r_dot=a.*m_ox.^b;% in futuro r_dot sara gia fornito da dati sperimentali
C=((m_dot_fuel+m_ox-m_dot_pr)./(v_cham)) ;
A=((4.*r_dot)./Dp_t);
dt=t(2)-t(1);
t_span=(0:dt:burn_time);
y_0=zeros(1,Nt);
y_0=y_0(:);
[T,Y ]=ode45(@(t,y) vdp1(C,y,A),t_span,y_0);
function dydt = vdp1(C,y,A)
dydt =C+A*y;
dydt=dydt(:);
end

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Answer 1

Star Strider 2021-1-6

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/710238-error-in-ode-45#answer_592203

在 MATLAB Online 中打开

The problem here:

[T,Y ]=ode45(@(t,y) vdp1(C,y,A),t_span,y_0);

is that one of the input arguments to ‘vdp1’ needs to be ‘t’.

There are too many missing constants for me to run your code, however this:

[T,Y ]=ode45(@(t,y) vdp1(t,C,y,A),t_span,y_0);

should work, if there are no other problems.

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Francesco Renzulli 2021-1-6

在 MATLAB Online 中打开

clc;
close all;
clear all;
%% Parametrizzazione DEL FLUSSO DI OSSIDANTE 
%In futuro questa parte di codice verrà sostiutita dal grafico excel, che
%ci indichera si ala discretizzazione temporale che i valori della funzione
%m_ox
burn_time=100;
Nt=1000;
m_ox=0.7;
t=linspace(0,burn_time,Nt);
m_ox=m_ox.*ones(1,Nt);
Dp_in=0.0005;
rho_fuel=1.9;
L_grain=0.5;
%% Definizione regression rate
a=0.007;
b=0.67;
r_dot=a.*m_ox.^b;% in futuro r_dot sara gia fornito da dati sperimentali
%% variabili ugello divergente 
At =1.45*10^(-4);%Area della gola del' ugello 
P_e=1*10^6;% Pressione in uscita 
P_cham=45*10^6;
gamma=1.2;
T_cham=3000;
R=0.344;
 %% Ugello isoentropico
 T_e=T_cham*(P_e/P_cham)^((gamma-1)/gamma);
 sound_v=(gamma*R*T_e)^0.5;
 T_t=(2*R*gamma*T_cham)/(gamma-1);
 v_e=(T_t*(1-((P_e/P_cham)^((gamma-1)/gamma))))^0.5;
 M_e=v_e/sound_v;
 
 %Pt=P_e*(1+((gamma-1)/2)*M_e^2)^((gamma)/(gamma-1));
 Pt=P_cham*(T_cham./T_t)^(gamma/(gamma-1));
 %Pt=((2/(gamma+1))^(gamma/(gamma-1)))*2.068;
 
 
 m_dot_pr=(At*Pt)/(((T_t)^0.5))*((gamma/R)^0.5)*((gamma+1)/2);
%% Calcolo il variare del DIameter port
syms Dp(T) T
ode=diff(Dp,T)==2.*r_dot;
cond=Dp(0)==Dp_in;
Dp=dsolve(ode,cond);
Dp_t=subs(Dp,T,t);
%% Calcolo la variazione di volume della C.C e dell' afflusso di carburante nel tempo 
m_dot_fuel=r_dot.*rho_fuel*L_grain.*Dp_t;
v_cham=((Dp_t./2).^2).*L_grain;
plot(t,m_dot_fuel);
figure(2)
plot(t,v_cham);
%% Calcolo la variazione di densita risolvendo il sistema lineare 
C=((m_dot_fuel+m_ox-m_dot_pr)./(v_cham)) ;
A=((4.*r_dot)./Dp_t);
dt=t(2)-t(1);
t_span=(0:dt:burn_time);
y_0=zeros(1,Nt);
y_0=y_0(:);