From help-request at octave dot org Wed Jan 12 09:04:14 2005
Subject: New system for ODE
From: "homer_jay at katamail dot com" <homer_jay@katamail.com>
To: help at octave dot org
Date: Wed, 12 Jan 2005 15:06:54 +0000

i'm trying to solve a new system, with 2 m-files: the first one, ruNuovo.m, contains the instructions, and the second one, Nuovo.m contains the equations. so i just type "ruNuovo". first i have a tollerance error message (now it's not a great problem), second my octave (2.1.50) crushes after a long time period!!
can you run my m-files?
here they are

ruNuovo.m

L=1;
T0=240+273;
D0=1.06e-03;
y0=[T0 2 D0];
z=linspace(0,L,100)';
y=lsode("Nuovo",y0,z);
plot(z,y(:,1)-273)
#plot(z,y(:,3))


and Nuovo.m:

function Nuovo=f(y,z)
# sistema dell'ipfdd
# y(1)=T(x)
# y(2)=F(x)
# y(3)=D(x)
g=9.810;
rho=900;
Cp=2500;
Ta=25+273;
alfa=0.065;
Talfa=473;
Taria=15+273;
lambda=3e-2;
Q=3.85e-05;
a=0.41;
b=0.61;
Nua=1000000*(10.2+0.131*(y(1)-273));
v=4*Q/(rho*3.14*y(3)^2);
Re=v*y(3)/Nua;
Cd=a*Re^b;
Nu=0.42*(Re)^(1/3);
Etap=exp(-alfa*(y(1)-Talfa));
Nup=Etap/rho;
dNup=-alfa*Etap/rho;
tau=(1/2)*Cd*rho*v^2;
hc=Q*Cp/(Nu*3.14*lambda);
Nuovo(1)=-(y(1)-Taria)/hc;
Nuovo(2)=(-8*Q^2/(rho*3.14*y(3)^3))+3.14*y(3)*tau-0.25*rho*g*3.14*y(3)^2;
Nuovo(3)=-8*Q/(rho*3.14*y(3)^3);
endfunction


thanks

 

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