Could someone please help me with my code I have spent a lot of time working on it and I still didn4t figure out what is the problem

R=8.314/32;
T0=2930;
a=(12)/((2.027*10^6)^0.45);
rhoP=1920;
Astar=pi*0.25^2;
k=1.35;
n=0.45;
P0=101325;
%syms P(t)
%at beginning of the integration set initial values for the persistent variables
rp=0.35; %initial port radius
v0=pi*rp^2*8;
t1=0; %initial time step
dP=@(t,P)Fun(t,P,R,T0,rp,a,n,Ab,P0,rhoP,Astar,k,v0);%@(t,P)(Ab.*a.*P.^n.*(rhoP-rhoO)-P.*Astar.*sqrt(k/(R.*T0)).*(2/(k+1)).^((k+1)/(2.*(k-1)))).*R.*T0./v0;
[t,P]=ode45(dP, [0,0.001], P0);
figure(1)
plot(t,y)
xlabel("Time (s)")
ylabel("Chamber Pressure (Pa)")
title("Chamber Pressure vs Time (Start-Up)")
dP=@(t1,P)Fun(t,P,R,T0,rp,a,n,t1,Ab,P0,rhoP,Astar,k,v0);%@(t,P)(Ab.*a.*P.^n.*(rhoP-rhoO)-P.*Astar.*sqrt(k/(R.*T0)).*(2/(k+1)).^((k+1)/(2.*(k-1)))).*R.*T0./v0;
[t,P]=ode45(dP, [0,60], P0);
hold on
figure(2)
plot(t,y)
xlabel("Time (s)")
ylabel("Chamber Pressure (Pa)")
title("Chamber Pressure vs Time ")
hold off

function dP = Fun(t,P,Ab,R,T0,rp,a,n,rhoP,Astar,k)
dP=0;
if t==0
    rp=0.35;
   
end
Ab=2*pi*rp*8;
rhoO=P/(R*T0);
rp>=0.7
Ab=0;

v0=pi*rp^2*8;
t1=t;
rp=min(rp+((a*P^n)*10^-3)*(t-t1),0.7);
Ab=2*pi*rp*8;
dP = (Ab.*a.*P.^n.*(rhoP-rhoO)-P.*Astar.*sqrt(k/(R.*T0)).*(2/(k+1)).^((k+1)/(2.*(k-1)))).*R.*T0./v0;
end

[John D'Errico]

There is no problem that I see. It does exactly what it does. Of course, you give no hint at all as to where the problem may lie, or even what the code should, in your opinion do, or why you think there may be a problem.

To this end, I am now using my MATLAB tarot cards, so see if they identify what is the problem, but all they want to tell me is you may come into some money soon.

[Amal Fennich]

my code gives me this error I forgot to include it >> rocket3

Error using rocket3>Fun

Too many input arguments.

Error in rocket3>@(t,P)Fun(t,P,R,T0,rp,a,n,Ab,P0,rhoP,Astar,k,v0) (line 14)

dP=@(t,P)Fun(t,P,R,T0,rp,a,n,Ab,P0,rhoP,Astar,k,v0);%@(t,P)(Ab.*a.*P.^n.*(rhoP-rhoO)-P.*Astar.*sqrt(k/(R.*T0)).*(2/(k+1)).^((k+1)/(2.*(k-1)))).*R.*T0./v0;

Error in odearguments (line 90)

f0 = feval(ode,t0,y0,args{:}); % ODE15I sets args{1} to yp0.

Error in ode45 (line 115)

odearguments(FcnHandlesUsed, solver_name, ode, tspan, y0, options, varargin);

Error in rocket3 (line 15)

[t,P]=ode45(dP, [0,0.001], P0);

[Stephen23]

The function input arguments are inconsistent:

Fun(t,P,R,T0,rp,a,n,Ab,P0,rhoP,Astar,k,v0) % function call
Fun(t,P,Ab,R,T0,rp,a,n,rhoP,Astar,k) % function definition

Aligned on the matching names:

Fun(t,P,   R,T0,rp,a,n,Ab,P0,rhoP,Astar,k,v0) % function call
Fun(t,P,Ab,R,T0,rp,a,n,      rhoP,Astar,k   ) % function definition

Answer 1

[Subhadeep Koley]

As rightly pointed by Stephen Cobeldick, the function input arguments are inconsistent. I have made some changes in the script and the function. Check whether it is providing your expected output or not.

SCRIPT

clear;close all;clc;
R=8.314/32;
T0=2930;
a=(12)/((2.027*10^6)^0.45);
rhoP=1920;
Astar=pi*0.25^2;
k=1.35;
n=0.45;
P0=101325;
%syms P(t)
%at beginning of the integration set initial values for the persistent variables
rp=0.35; %initial port radius
v0=pi*rp^2*8;
t1=0; %initial time step
dP=@(t,P)Fun(t,P,R,T0,rp,a,n,rhoP,Astar,k);%@(t,P)(Ab.*a.*P.^n.*(rhoP-rhoO)-P.*Astar.*sqrt(k/(R.*T0)).*(2/(k+1)).^((k+1)/(2.*(k-1)))).*R.*T0./v0;
[t,P]=ode45(dP, [0,0.001], P0);
figure(1);
plot(t,P);
xlabel("Time (s)");
ylabel("Chamber Pressure (Pa)");
title("Chamber Pressure vs Time (Start-Up)");
dP=@(t,P)Fun(t,P,R,T0,rp,a,n,rhoP,Astar,k);%@(t,P)(Ab.*a.*P.^n.*(rhoP-rhoO)-P.*Astar.*sqrt(k/(R.*T0)).*(2/(k+1)).^((k+1)/(2.*(k-1)))).*R.*T0./v0;
[t,P]=ode45(dP, [0,60], P0);
hold on;
figure(2);
plot(t,P);
xlabel("Time (s)");
ylabel("Chamber Pressure (Pa)");
title("Chamber Pressure vs Time ");
hold off;

FUNCTION

function dP = Fun(t,P,R,T0,rp,a,n,rhoP,Astar,k)
if t==0
    rp=0.35;
    
end
rhoO=P/(R*T0);
rp>=0.7;
v0=pi*rp^2*8;
t1=t;
rp=min(rp+((a*P^n)*10^-3)*(t-t1),0.7);
Ab=2*pi*rp*8;
dP = (Ab.*a.*P.^n.*(rhoP-rhoO)-P.*Astar.*sqrt(k/(R.*T0)).*(2/(k+1)).^((k+1)/(2.*(k-1)))).*R.*T0./v0;
end

Hope this helps!