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

Question

Amal Fennich 2019-11-3

0
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https://ww2.mathworks.cn/matlabcentral/answers/488994-could-someone-please-help-me-with-my-code-i-have-spent-a-lot-of-time-working-on-it-and-i-still-didn4

回答： Subhadeep Koley 2019-11-6

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

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Amal Fennich 2019-11-3

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 2019-11-3

编辑：Stephen23 2019-11-3

在 MATLAB Online 中打开

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

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Answer 1

Subhadeep Koley 2019-11-6

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/488994-could-someone-please-help-me-with-my-code-i-have-spent-a-lot-of-time-working-on-it-and-i-still-didn4#answer_400109

在 MATLAB Online 中打开

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