matlab ode45 out of memory

Question

Mitul Dattani 2018-11-14

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/429865-matlab-ode45-out-of-memory

评论： madhan ravi 2018-11-15

Out of memory error on line 45 cant draw the graph of the below function

function dh_dt = tankf1(t,h)
% Tank model parameters and constants
A = 12.5;       % m^2
CV1 = 3.41;     % (m^3/h)/kPa^0.5
CV2 = 3.41;     % (m^3/h)/kPa^0.5
P0 = 100;       % kPa
P3 = 100;       % kPa
rho = 1000;     % kg/m^3
g = 9.81;       % m/s^2
P1 = P1function(t);  % kPa
dh_dt = (1/A)*((CV1*sqrt(P1-P0-rho*g*h/1000))-(CV2*sqrt(P0+rho*g*h/1000-P3)));
% Set extra parameters
tf = 72; % h
h0 = 2; % m
% Solve the DAE
opts = odeset('Reltol',1e-5);
[t,h] = ode45(@tankf1,[0 tf],h0,opts);
% Plot the graph
plot(t,h)
title('Tank model solved by Method 1')
xlabel('Time (h)')
ylabel('Level (m)')
grid on
function P1 = P1function(t)
% P1FUNCTION: Upstream pressure (kPa) as a function of time (h)
if t<=10
    P1 = 139.5;
elseif t<=11
    P1 = 139.5 + 60.5*(t-10);
elseif t<=40
    P1 = 200;
elseif t<=55
    P1 = 200 - 30*(t-40)/15;
else  % t>55
    P1 = 170;
end

The error is given as :

Out of memory. The likely cause is an infinite recursion within the program.
Error in odearguments (line 90)
f0 = feval(ode,t0,y0,args{:});   % ODE15I sets args{1} to yp0.

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Answer 1

madhan ravi 2018-11-14

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/429865-matlab-ode45-out-of-memory#answer_346937

编辑：madhan ravi 2018-11-14

在 MATLAB Online 中打开

 
tf = 72; % h
h0 = 2; % m
% Solve the DAE
opts = odeset('Reltol',1e-5);
[t,h] = ode45(@tankf1,[0 tf],h0,opts);
% Plot the graph
plot(t,h)
title('Tank model solved by Method 1')
xlabel('Time (h)')
ylabel('Level (m)')
grid on
 
function dh_dt = tankf1(t,h)
% Tank model parameters and constants
A = 12.5;       % m^2
CV1 = 3.41;     % (m^3/h)/kPa^0.5
CV2 = 3.41;     % (m^3/h)/kPa^0.5
P0 = 100;       % kPa
P3 = 100;       % kPa
rho = 1000;     % kg/m^3
g = 9.81;       % m/s^2
P1 = P1function(t);  % kPa
dh_dt = (1/A)*((CV1*sqrt(P1-P0-rho*g*h/1000))-(CV2*sqrt(P0+rho*g*h/1000-P3)));
% Set extra parameters
end
 
function P1 = P1function(t)
% P1FUNCTION: Upstream pressure (kPa) as a function of time (h)
if t<=10
    P1 = 139.5;
elseif t<=11
    P1 = 139.5 + 60.5*(t-10);
elseif t<=40
    P1 = 200;
elseif t<=55
    P1 = 200 - 30*(t-40)/15;
else  % t>55
    P1 = 170;
end
end