Error using BVP4c (singular Jacobian encountered)

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Adarrsh Patil
Adarrsh Patil 2020-3-8
回答： Devineni Aslesha 2020-4-23
Hi,
I am trying to get a concentration profile in my catalyst particle using the following code but I am getting an error of Singular Jacobian being encountered.
clear all
close all
clc
Pt = 85; %bar
P_CO = (1-0.05)/3*Pt; %bar
P_H2 = 2*(1-0.05)/3*Pt; %bar
P_H2O = 0*Pt;
P_CO2 = 0*Pt;
P_CH3OH = 0;
d_p = 3e-4; %diameter of particle in metres
xmesh = linspace(d_p/2,0,50);
solinit = bvpinit(xmesh, @guess);
sol = bvp4c(@bvpfcn, @bcfcn, solinit);
function dydx = bvpfcn(x,y)
P_CO = (1-0.05)/3*85; %bar
P_H2 = 2*(1-0.05)/3*85; %bar
P_CH3OH = 0;
T_rxn = 280; %degree Celsius
T = T_rxn + 273.15;
R = 8.314;
R1 = 8.314e-5; %bar.m^3.(mol.K)^-1
rho_cat = 1000; %kg/m3
D_CO = 1e-9; %m2/s
dydx = zeros(5,1);
dydx = [y(2)
(2.68e9*exp(-18400/T)*(K_calc(T)*y(1)*y(3)^2 - y(5)))*rho_cat*R1*T_rxn/(((1 + 0.069 * y(1) + 6.19e-8 * exp(6610/T) * y(3))^3)*D_CO*K_calc(T)) - 2*y(1)/x
y(3)
(2.68e9*exp(-18400/T)*(K_calc(T)*y(1)*y(3)^2 - y(5)))*rho_cat*R1*T_rxn*2/(((1 + 0.069 * y(1) + 6.19e-8 * exp(6610/T) * y(3))^3)*D_CO*K_calc(T)) - 2*y(3)/x
-y(1) - 2*y(3)];
function K_eq = K_calc(T)
A = 5139;
B = 12.621;
K_eq = 10 ^ (A/(T-B));
end
end
function res = bcfcn(ya,yb)
res = [ya(1) - (1-0.05)/3*85
yb(2)
ya(3) - (1-0.05)/3*85*2
yb(4)
ya(5)];
end
function g = guess(x)
g = [(1-0.05)/3*85
tanh(x)
(1-0.05)/3*85*2
tanh(x)
0];
end

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回答（1 个）

Devineni Aslesha
Devineni Aslesha 2020-4-23
Hi
I hope this link might help you to solve the error (Singular Jacobian encountered) when using bvp4c function in MATLAB.

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