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problem on solve function,the result is empty sym:0-by-1

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arham zakki edelo
arham zakki edelo 2019-5-18
关闭： John D'Errico 2019-5-18
i got some trouble when i run this script function, at the solve function the result is empty sym:0-by-1, i am relatively new in MatLab can anyone help me?
function[u_g] = viscosity(Pm) % viscosity() calculates viscosity of the gas at given reservoir % temperature and pressure.
M_air=[28.96;29;29.56;30;31;31.86;32;32.3;33;33.50];
Avg_Mol_Wt= [25.48;26;26.12;26.79;27;27.60;28;29;29.40;30];
spgr=Avg_Mol_Wt.\M_air;
Pm=[3800;3850;3400;3450;3500;3550;3600;3650;3700;3750]; %initial reservoir pressure
T=[660;680;720;740;760;780;800;820;840;860]; %Reservoir Temperature= 660 deg R (Literature)
u_uncorrected = ((1.709 * (10^(-5)-(2.062*10^(-6)*spgr))).*(T-460))+((8.118*10^(-3))-(6.15*10^(-3)*log10(spgr)));
yCO2 = 0.03;
yN2 = 0.02;
yH2S = 0.01;
u_CO2 = (yCO2*(((9.08*10^(-3))*(log10(spgr)))+ (6.24*10^(-3))));
u_N2 = (yN2*((8.48*10^(-3)*log10(spgr))+ (9.59*10^(-3))));
u_H2S = (yH2S*((8.49*10^(-3)*log10(spgr))+ (3.73*10^(-3))));
u1 = u_uncorrected + u_CO2 + u_N2 + u_H2S ;
Tpc = 168 + (325 * spgr) -(12.5*(spgr.^2));
Ppc = 677 + (15*spgr) -(37.5*(spgr.^2));
Tpr = T.\Tpc;
Ppr = Pm.\Ppc;
% Constants for viscosity relation
na=[1
1
1
1
1
1
1
1
1
1];
a0 = na.*-2.5;
a1 = na.*3;
a2 = na.*-0.29;
a3 = na.* 0.008;
a4 = na.*2.89;
a5 = na.* -3.5;
a6 = na.*0.36;
a7 = na.*-0.01;
a8 = na.*-0.8;
a9 = na.*1.4;
a10 = na.*-0.15;
a11 = na.*0.0044;
a12 = na.*0.084;
a13 = na.*-0.18;
a14 = na.*0.02;
a15 = na.*-0.0006;
syms ug;
con = a0+(a1.*Ppr)+(a2.*(Ppr.^2))+ (a3.*(Ppr.^3)) +(Tpr.*(a4+(a5.*Ppr))+(a6.*(Ppr.^2))+(a7.*(Ppr.^3))+((Tpr.^2).*(a8+(a9.*Ppr)))+(a10.*(Ppr.^2))+(a11.*(Ppr.^3)))+((Tpr.^3).*(a12+(a13.*Ppr)+(a14.*(Ppr.^2))+(a15.*(Ppr.^3))))
eqn = ((Tpr.*ug) == u1.*exp(con));
temp= solve(eqn,'ug')
u_g = double(temp);
end
the result
>> viscosity
con =
-0.5039
-0.5552
-0.5859
-0.6263
-0.6414
-0.6689
-0.7055
-0.7509
-0.7738
-0.8039
temp =
Empty sym: 0-by-1
ans =
0×1 empty double column vector

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