Problem with inf value

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I am having inf values, while I am supposed to be having 1.0396e+01 value... (which is apparently not at all an infinite value)...
I have 4 loops in my code : and I am trying to get the ratios condGaz(i,j,k) / condGaz(i,j,g), where k=1:3 ; g=1:3.
Here is a part of my code :
----------- Before this, I have 3 loops i (for Temperature), j (for Pressure), k=1:3 and this loop is my final loop ------------
for g=1:3
if k~=g
Phigk(i,j,k,g) = condGaz(i,j,k) / condGaz (i,j,g);
else
Phigk(i,j,k,g) =0 ;
end
end
end
end
end
Here are the condGaz(i,j,k) values.
And here are the values that I obtain for my ratio Phigk (i,j,k,g) = condGaz(i,j,k) / condGaz (i,j,g);
I get the impression that for g=1, I get all values right...
As soon as it gets to g=2 I get 1 value right and the other is INF
And for g=3, I get all the values INF....
I am not supposed to be having INF values because I manually did the ratio of for example Phigk(1,1,2,3) = condGaz(1,1,2) / condGaz(1,1,3) = 1.23e+00. (which is INF value if you see the results with the loops for Phigk(:,:,2,3)...
I tried format shortE and stuff... And it did not work... So I am confused about the sense of this INF value.... It is supposed to give INF value when the result is too big... But here we are talking values of 1.23e+00.... Can you please help me?
  14 Comments
Plamen Bonev
Plamen Bonev on 20 May 2021
Here is the full version of my code :
format shortE
%Constante des gaz parfaits en J/mol.K
Rg=8.314;
%---------------------- Températures en K -------------------------
%T=[200 : 100 : 1000];
%T=[1000 : 100 : 2000];
T=[600 : 200 : 2000];
% -------------------- Pressions en Pa -----------------------------
%------------ P = [0.01 Mpa ; 0.1 Mpa] ---------------------
% P=[0.1e5:0.1e5:1e5]
% ----------- P = [0.1 MPa (1 bar) ; 10 MPa (10 bar)] ---------
% P=[1e5:2e5:100e5];
% ----------- P = [40MPa, 45MPa] -----------
P=[400e5:50e5:450e5];
% ----------- P = [0.1MPa, 1MPa] -----------
% P=[1e5:1e5:10e5];
% P=[0.1e5 : 1e5 : 200e5];
% ---------- Echelle log pour la Pression (de 1e4 Pa (0.01 MPa) à 1e7 Pa (10MPa) avec 1000 points entre les
% deux) ---------
% P=logspace(4, 7, 1000)
%He indice 1
%Kr indice 2
%Xe indice 3
% ------------------- Nombre de gaz considéré -----------------------
NbGaz=[1, 2, 3];
%--------------Paramètres critiques pour chaque gaz (pour le modèle avancé) ----------
%Masses molaires en kg/mol
M=[4.003e-3, 83.798e-3, 131.293e-3];
%Pressions critiques Pc en Pa
Pc=[0.2275e6, 5.51e6, 5.84e6];
%Températures critiques Tc en K
Tc=[5.2, 209.4, 289.7];
%Densités critiques rhoc en kg/m^3
rhoc=[69.64, 908.4, 1110];
%Coefficients directeurs pour viscosité dynamique
Anu=[3.063e-7, 6.963e-7, 7.568e-7];
%Coefficients de température pour viscosité dynamique en K
Tnu=[-21.33, 71.07, 112.31];
%Exposants pour viscosité dynamique
n=[0.724, 0.667, 0.655];
%--------------- Constantes a et b pour chaque gas (pour le modèle
%simplifié) ---------------
%He indice 1
%Kr indice 2
%Xe indice 3
aURGAP=[176.32e-5, 9.8e-5, 4.6e-5];
bURGAP=[0.77227, 0.8007, 0.8425];
aROCHE=[284e-5, 8.11e-5, 5.14e-5];
bROCHE=[0.7, 0.83, 0.83];
aBISON=[263.9e-5, 8.247e-5, 4.351e-5];
bBISON=[0.7085, 0.8363, 0.8616];
%------------ Initialisation des vecteurs/matrices -----------------
visc0=zeros(length(T),1);
cond0=zeros(length(T),1);
Vetoile=zeros(length(NbGaz),1);
condPseudoCr=zeros(length(NbGaz),1);
rho=zeros(length(T), length(P), length(NbGaz));
B2=zeros(length(T), length(NbGaz));
B3=zeros(length(T), length(NbGaz));
theta=zeros(length(T), length(NbGaz));
coef1=zeros(length(T), length(P));
coef2=zeros(length(T), length(P), length(NbGaz));
coef3=zeros(length(T), length(P), length(NbGaz));
racines=cell(length(T), length(P), length(NbGaz));
vraiRacines=cell(length(T), length(P), length(NbGaz));
B=cell(length(T), length(P), length(NbGaz));
imagi=cell(length(T), length(P), length(NbGaz));
rhor=zeros(length(T), length(P), length(NbGaz));
psi=zeros(length(T), length(P), length(NbGaz));
condGaz=zeros(length(T), length(P), length(NbGaz));
condGazURGAP=zeros(length(T), length(NbGaz));
condGazROCHE=zeros(length(T), length(NbGaz));
condGazBISON=zeros(length(T), length(NbGaz));
rapportURGAP=zeros(length(T), length(P), length(NbGaz));
pourcentageAugm=zeros(length(T), length(P), length(NbGaz));
diffURGAP=zeros(length(T), length(P), length(NbGaz));
diffBISON=zeros(length(T), length(P), length(NbGaz));
diffROCHE=zeros(length(T), length(P), length(NbGaz));
Psigk=zeros(length(T), length(P), length(NbGaz), length(NbGaz));
Phigk=zeros(length(T), length(P), length(NbGaz), length(NbGaz));
for k=1:numel(NbGaz)
%Volumes molaires caractéristiques
Vetoile(k)=Rg*Tc(k)/Pc(k);
condPseudoCr(k)=(0.201e-4*((Tc(k))^(0.277))*((M(k))^(-0.465)))/((0.291*Vetoile(k))^(0.415));
for i=1:numel(T)
%----------Conductivité de chaque gaz (modèle simplifié)---------
%Données a et b URGAP
condGazURGAP(i,k)=aURGAP(k)*(T(i))^(bURGAP(k));
%Données a e b ROCHE
condGazROCHE(i,k)=aROCHE(k)*(T(i))^(bROCHE(k));
%Données a et b BISON
condGazBISON(i,k)=aBISON(k)*(T(i))^(bBISON(k));
%----------Modèle avancé---------
theta(i,k)=(T(i))/(Tc(k));
visc0(i,k)=Anu(k)*(T(i)-Tnu(k))^(n(k));
cond0(i,k)=visc0(i,k)*((15*Rg)/(4*M(k)));
if k==2 | k==3
B2(i,k)=(-102.6+(102.732-0.001*theta(i,k)-0.44*((theta(i,k))^(-1.22)))*tanh(4.5*sqrt(theta(i,k))))*Vetoile(k);
B3(i,k)=(0.0757+(-0.0862+(-3.6e-5)*theta(i,k)+0.0237*((theta(i,k))^(-0.059)))*tanh(0.84*theta(i,k)))*((Vetoile(k))^2);
else
B2(i,k)=(8.4-0.0018*T(i)+(115/(sqrt(T(i))))-835/(T(i)))*(10^(-6));
B3(i,k)=0;
end
for j=1:numel(P)
%coef1, 2 et 3 corréspondent aux coefficients devant rho
coef1(i,j,k)=(Rg*T(i))/(P(j));
coef2(i,j,k)=(B2(i,k))*((Rg*T(i))/(P(j)));
coef3(i,j,k)=(B3(i,k))*((Rg*T(i))/(P(j)));
% On cherche les racines de l'équation cubique d'état
racines{i,j,k}=((roots([coef3(i,j,k), coef2(i,j,k), coef1(i,j,k), -1])));
% On récupère uniquement les racines réelles
vraiRacines{i,j,k}=racines{i,j,k}(imag(racines{i,j,k})==0);
% La densité corréspond à la valeur maximale de chaque racine trouvée
% pour chaque jeu de (P, T, gaz)
rho(i,j,k)=(max(vraiRacines{i,j,k}))*M(k);
% Densité réduite
rhor(i,j,k)=(rho(i,j,k))/rhoc(k);
% Psi
% psi(i,j,k)=0.645*rhor(i,j,k)+0.331*((rhor(i,j,k))^2)+0.0368*((rhor(i,j,k))^3)-0.0128*((rhor(i,j,k))^4);
psi(i,j,k)=0.645+0.331*((rhor(i,j,k))^1)+0.0368*((rhor(i,j,k))^2)-0.0128*((rhor(i,j,k))^3);
% % Calcul final de la conductivité d'un gaz
condGaz(i,j,k)=cond0(i,k)+(condPseudoCr(k)*psi(i,j,k)*(rhor(i,j,k)));
%RapportsURGAP
rapportURGAP(i,j,k)=(condGaz(i,j,k))/(condGazURGAP(i,k));
%Calcul d'erreur entre le modèle avancé/modèle simple
% Erreur URGAP / avancé (en %)
diffURGAP(i,j,k)=(condGazURGAP(i,k)-condGaz(i,j,k))*10^2;
% Erreur BISON/ avancé (en %)
diffBISON(i,j,k)=(condGazBISON(i,k)-condGaz(i,j,k))*10^2;
% Erreur ROCHE/ avancé (en %)
diffROCHE(i,j,k)=(condGazROCHE(i,k)-condGaz(i,j,k))*10^2;
% POUR GUILHERME : LE PROBLEME COMMENCE ICI.
for g=1:numel(NbGaz)
disp(['i,j,k,g = ' num2str([i j k g]) ' ; condGaz (i,j,g) = ' num2str(condGaz(i,j,g))])
Phigk(i,j,k,g)=(condGaz(i,j,k))/(condGaz(i,j,g));
end
end
end
end

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Accepted Answer

Walter Roberson
Walter Roberson on 20 May 2021
condGaz(i,j,k)=cond0(i,k)+(condPseudoCr(k)*psi(i,j,k)*(rhor(i,j,k)));
That sets condGaz(I,j,:) according to the largest k value that has been seen so far. For example at k = 1, condGaz(i,j,1) will be set, and condGaz(i,j,2) will not have been set yet.
for g=1:numel(NbGaz)
disp(['i,j,k,g = ' num2str([i j k g]) ' ; condGaz (i,j,g) = ' num2str(condGaz(i,j,g))])
but numel(NbGaz) is greater than k = 1, so in this inner loop within for k, as soon as g is greater than the current k, you index condGaz(i,j,:) elements that are still 0, and that gets you a division by 0.
Perhaps that loop needs to be postponed until after the other arrays have been fully built.
  3 Comments
Plamen Bonev
Plamen Bonev on 20 May 2021
Thank you, Walter, you solved it all for me.
Cheers.

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