Doubt in solving ODE45

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Susmita Panda 2021-9-20

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https://ww2.mathworks.cn/matlabcentral/answers/1457019-doubt-in-solving-ode45

编辑： Star Strider 2021-9-20

tried_ode_both.m

I am trying to solve a differential equation for parameter 'dis' for infinite length of beam which is function of time and space in ode45.I am doubtful about how to consider infinite 'L' in the analysis, as my time is dependent upon v (velocity) and L (length).

I tried solving ode45 as usual taking arbitary L=20 but want to plot 'dis' wrt to space.I need help in plotting.My code has been attached herein.

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Jan 2021-9-20

The code is not visible yet.

Susmita Panda 2021-9-20

Sir,please check my code.

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Answer 1

Star Strider 2021-9-20

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1457019-doubt-in-solving-ode45#answer_791474

编辑：Star Strider 2021-9-20

在 MATLAB Online 中打开

It seems that ‘dis’ does not appear anywhere.

L=20;

v=20;%v (m/sec)

T=L/v;

tspan_1=[0:0.001:T];%time range

y0_1=[0;0];%initial conditions

[t1,y1]=ode45(@diffeqn11,tspan_1,y0_1);

figure()

plot(t1, y1(:,1), 'r', 'LineWidth',2)

grid

xlabel('t_1')

ylabel('y_1')

function f= diffeqn11(t,y)

A=250;B=20;C=10;j=1;L=20;v=20;a=0.5;%a=x/L

f=zeros(2,1);

f(1)=y(2);

f(2)=(A*sin(j*pi*v*t/L)-B*y(2)-C*y(1))*sin(j*pi*a);%Dimensional

end

EDIT — (20 Sep 2021 at 19:24)

If you have ‘y’ as a function of space and time, this is a partial differential equation.

Express

appropriately as a function of both space and time, and then solve it with the pdepe function, or the partial Differential Equation Toolbox functions.

.