Unrecognized function or variable

2020 3 19
1 个回答
更新时间：2020 3 20
1 次查看（30 天）

0 个投票

Hi everyone,
I am having trouble with my code, in particular the variable 'T'. I always seem to get back to this error and was wondering where I am going wrong.
Thanks.
Unrecognized function or variable 'T'.
Error in Main_Script>dTdr (line 93)
dTdr_ = Z/(r*(k(T)+rho(T)*Cp(T)*epsilon_m_));
Error in Main_Script (line 21)
w1=h*dTdr(r(i),Z(i),Cp(T),k(T),rho(T),epsilon_m_(r,T,Rm,Ri,Ro,tawi,tawo));
% Parameters & Boundary Conditions
dTdz=30.12; Ri=0.05; Ro=0.075; Rm=0.0621; hcoeff=100; To=300; Ti=0; Zo=0; Zi=1.3*Ri*hcoeff*(Ti-To); uRi=0; uRo=0; tawi=4.3465; tawo=3.792; npoints=1000;
h=(Ro-Ri)/npoints;
r=(Ri+h:h:Ro)';
uR= zeros(npoints,1);
T= zeros(npoints,1);
Z = zeros(npoints,1);
%
% Call Runge Kutta Function Fourth Order
for i=1:1:(npoints-1)
T(1)=Ti;
Z(1)=Zi;
uR(1)= uRi;
if r(i)<Rm
k1=h*dUdrI(r(i),tawi,mu(T),rho(T),epsilon_m_(r,T,Rm,Ri,Ro,tawi,tawo),Rm,Ri);
w1=h*dTdr(r(i),Z(i),Cp(T),k(T),rho(T),epsilon_m_(r,T,Rm,Ri,Ro,tawi,tawo));
f1=h*dZdr(r(i),rho(T),Cp(T),uR,dTdz);
k2=h*dUdrI((r(i)+h/2),tawi,mu(T),rho(T),epsilon_m_(r,T,Rm,Ri,Ro,tawi,tawo),Rm,Ri);
w2=h*dTdr((r(i)+h/2),Z,Cp(T),k(T),rho(T),epsilon_m_(r,T,Rm,Ri,Ro,tawi,tawo));
f2=h*dZdr((r(i)+h/2),rho(T),Cp(T),uR,dTdz);
k3=h*dUdrI((r(i)+h/2),tawi,mu(T),rho(T),epsilon_m_(r,T,Rm,Ri,Ro,tawi,tawo),Rm,Ri);
w3=h*dTdr((r(i)+h/2),Z,Cp(T),k(T),rho(T),epsilon_m_(r,T,Rm,Ri,Ro,tawi,tawo));
f3=h*dZdr((r(i)+h/2),rho(T),Cp(T),uR,dTdz);
k4=h*dUdrI((r(i)+h),tawi,mu(T),rho(T),epsilon_m_(r,T,Rm,Ri,Ro,tawi,tawo),Rm,Ri);
w4=h*dTdr((r(i)+h),Z,Cp(T),k(T),rho(T),epsilon_m_(r,T,Rm,Ri,Ro,tawi,tawo));
f4=h*dZdr((r(i)+h),rho(T),Cp(T),uR,dTdz);
uR(i+1) = uR(i) + (k1+2*k2+2*k3+k4)/6;
T(i+1) = T(i) + (w1+2*w2+2*w3+w4)/6;
Z(i+1) = Z(i) + (f1+2*f2+2*f3+f4)/6;
end
end
for i=(npoints-1):1:1
T(1)=To;
Z(1)=Zo;
uR(1)=uRo;
if r(i)>=Rm
k1=h*dUdrO(r(i),tawo,mu(T),rho(T),epsilon_m_(r,T,Rm,Ri,Ro,tawi,tawo),Rm,Ro);
w1=h*dTdr(r(i),Z,Cp(T),k(T),rho(T),epsilon_m_(r,T,Rm,Ri,Ro,tawi,tawo));
f1=h*dZdr(r(i),rho(T),Cp(T),uR,dTdz);
k2=h*dUdrO((r(i)-h/2),tawo,mu(T),rho(T),epsilon_m_(r,T,Rm,Ri,Ro,tawi,tawo),Rm,Ro);
w2=h*dTdr((r(i)-h/2),Z,Cp(T),k(T),rho(T),epsilon_m_(r,T,Rm,Ri,Ro,tawi,tawo));
f2=h*dZdr((r(i)-h/2),rho(T),Cp(T),uR,dTdz);
k3=h*dUdrO((r(i)-h/2),tawo,mu(T),rho(T),epsilon_m_(r,T,Rm,Ri,Ro,tawi,tawo),Rm,Ro);
w3=h*dTdr((r(i)-h/2),Z,Cp(T),k(T),rho(T),epsilon_m_(r,T,Rm,Ri,Ro,tawi,tawo));
f3=h*dZdr((r(i)-h/2),rho(T),Cp(T),uR,dTdz);
k4=h*dUdrO((r(i)-h),tawo,mu(T),rho(T),epsilon_m_(r,T,Rm,Ri,Ro,tawi,tawo),Rm,Ro);
w4=h*dTdr((r(i)-h),Z,Cp(T),k(T),rho(T),epsilon_m_(r,T,Rm,Ri,Ro,tawi,tawo));
f4=h*dZdr((r(i)-h),rho(T),Cp(T),uR,dTdz);
uR(i+1)=uR(i)+(k1+2*k2+2*k3+k4)/6;
T(i+1)=T(i)+(w1+2*w2+2*w3+w4)/6;
Z(i+1)=Z(i)+(f1+2*f2+2*f3+f4)/6;
end
end
figure, plot (r,uR)
xlabel('Radius')
ylabel('Velocity')
title('Velocity vs Radius')
figure, plot (r,T)
xlabel('Radius')
ylabel('Temperature')
title('Temperature vs Radius')
figure, plot (r,Z)
xlabel('Radius')
ylabel('Heat transfer per unit length')
title('Heat transfer per unit length vs Radius')
% Heat Transfer per Unit Length
function [dZdr_] = dZdr (r,rho,Cp,uR,dTdz)
dZdr_ = -r*rho(T)*Cp(T)*uR*dTdz;
end
% Temperature Profile
function [dTdr_] = dTdr (Z,r,k,rho,Cp,epsilon_m_)
dTdr_ = Z/(r*(k(T)+rho(T)*Cp(T)*epsilon_m_));
end
% Velocity Profile
function [dUdrI_] = dUdrI (tawi,mu,rho,epsilon_m_,Rm,r,Ri)
dUdrI_= tawi./(mu+rho*epsilon_m_)*((Rm^2-r^2)/(Rm^2-Ri^2))*(Ri/r);
end
function [dUdrO_] = dUdrO (tawo,mu,rho,epsilon_m_,r,Rm,Ro)
dUdrO_= tawo./(mu+rho*epsilon_m_)*((r^2-Rm^2)/(Ro^2-Rm^2))*(Ro/r);
end
%eddy diffusivities of momentum
function [epsilon_m] = epsilon_m_ (r,T,Rm,Ri,Ro,tawi,tawo)
if r<Rm
radratio=(r-Ri)/(Rm-Ri);
rEpsI=6.516e-4+3.9225e-1*radratio+(-6.0949e-1)*(radratio).^2+(2.3391e-1)*(radratio).^3+(1.410e-1)*(radratio).^4+(-9.6098e-2)*(radratio).^5;
epsilon_m=rEpsI*sqrt(tawi./rho(T))*(Rm-Ri);
else
radratio=(Ro-r)/(Ro-Rm);
rEpsO=6.516e-4+3.9225e-1*radratio+(-6.0949e-1)*(radratio).^2+(2.3391e-1)*(radratio).^3+(1.410e-1)*(radratio).^4+(-9.6098e-2)*(radratio).^5;
epsilon_m=rEpsO*sqrt(tawo./rho(T))*(Ro-Rm);
end
end
function [Cp_]=Cp(T)
Cp_=1010.4755 + 0.1151*(T) + 4.00e-5*(T).^2;
end
function [k_]=k(T)
k_=0.0243+(6.548e-5)*(T) - (1.65e-8)*(T).^2;
end
%Dynamic Viscosity
function [mu_]=mu(T)
mu_=1.747e-5 + 4.404e-8*(T) - 1.645e-11*((T).^2);
end
function [Pr_]=Pr(T)
Pr_=0.7057*10^(2.06e-5*(T));
end
function [rho_]=rho (T)
rho_ =1e5/(287*(T));
end
function [vis_]=vis(T)
vis_=1.380e-5 + (8.955e-8)*(T) - (1.018e-10)*(T)^2;
end

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回答（1 个）

Rik
Rik 2020-3-19

0 个投票

Inside of this function the variable T doesn't exist. You will have to pass it as a variable, or make this a nested function so it shares the variable with the outer function.
function [dTdr_] = dTdr (Z,r,k,rho,Cp,epsilon_m_)
dTdr_ = Z/(r*(k(T)+rho(T)*Cp(T)*epsilon_m_));
end

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Thomas Faulkner
Thomas Faulkner 2020-3-19
Thanks Rik!
What will I need to do to pass it as a variable?
I tried adding T to the brackets to call it as a variable but now I am getting a new error
Array indices must be positive integers or logical values.
Error in Main_Script>dTdr (line 93)
dTdr_ = Z/(r*(k(T)+rho(T)*Cp(T)*epsilon_m_));
Error in Main_Script (line 21)
w1=h*dTdr(r(i),Cp(T),k(T),rho(T),epsilon_m_(r,T,Rm,Ri,Ro,tawi,tawo));
Thanks for your help, I'm sure theres just a couple small mistakes I need to rectify.
>>
Rik
Rik 2020-3-20
Apparently T contains non-integers and/or values smaller than 1.

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Rik
2020-3-20

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