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铜虫 (小有名气)

[求助] 急!求大神用Matlab四阶龙格库塔解个方程! 已有1人参与

万分感谢,求哪位大神用matlab四阶龙格库塔帮我解下面这个方程
dy/dx=(-1.588)*10^(-7)*y^(2/7)*(9.617y^(2/7)-5)^(1/2), y(0)=0.11
求看见的大神帮我解一下,拜托了,万分感谢!!!!!!
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Fluent学习中
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铜虫 (小有名气)

引用回帖:
5楼: Originally posted by laosam280 at 2014-02-27 11:38:50
你这个方程右端因为有一个很小的系数,使得方程的解在很长的时间内都稳定在初值附近。你的初值给的是0.1918,要想解减少到哪怕0.09,x会上好几十万这么大。我刚刚试了一下。
代码都给你了,你自己去matlab上运行就 ...

haode ,xiexie
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6楼2014-02-27 15:55:06
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laosam280

禁虫 (正式写手)

【答案】应助回帖

感谢参与,应助指数 +1
feixiaolin: 数学EPI+1, reward for helping 2014-04-18 08:55:29
function SolveRK4
clear all; clc;
y0 = 0.11;
T = 50;
h = 1/20;
[t,y]=ode45(@myfun,[0:h:T],y0);

plot(t,y,'linewidth',3);
xlabel('x');
ylabel('y(x)')

function dt = myfun(t,y)
dt = [(-1.588)*10^(-7)*y^(2/7)*(9.617*y^(2/7)-5)^(1/2)];
急!求大神用Matlab四阶龙格库塔解个方程!
untitled.jpg

What hurts more, the pain of hard work, or the pain of regret?
2楼2014-02-27 11:16:58
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铜虫 (小有名气)

引用回帖:
2楼: Originally posted by laosam280 at 2014-02-27 11:16:58
function SolveRK4
clear all; clc;
y0 = 0.11;
T = 50;
h = 1/20;
=ode45(@myfun,,y0);

plot(t,y,'linewidth',3);
xlabel('x');
ylabel('y(x)')

function dt = myfun(t,y)
dt = ;

untitled.jpg
...

感谢大神帮助,万分感谢
但是我的初始值搞错了,还有我想知道几个特定y值下对应的
x值
麻烦大神给我重新算一下,拜托了
dy/dx=(-1.588)*10^(-7)*y^(2/7)*(9.617y^(2/7)-5)^(1/2), y(0)=0.1918
求y=0.096,0.093,0.09,0.087,0.079,0.072,0.065,0.056,0.052
对应的x值
拜托了大神!!!
Fluent学习中
3楼2014-02-27 11:26:04
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铜虫 (小有名气)

引用回帖:
2楼: Originally posted by laosam280 at 2014-02-27 11:16:58
function SolveRK4
clear all; clc;
y0 = 0.11;
T = 50;
h = 1/20;
=ode45(@myfun,,y0);

plot(t,y,'linewidth',3);
xlabel('x');
ylabel('y(x)')

function dt = myfun(t,y)
dt = ;

untitled.jpg
...

感谢大神,万分感谢
但是我初始值错了,还有就是,我想知道几个特定y值下对应的X值
dy/dx=(-1.588)*10^(-7)*y^(2/7)*(9.617y^(2/7)-5)^(1/2), y(0)=0.1918
求y=0.1,0.096,0.093,0.09,0.087,0.079,0.072,0.065,0.056,0.05,0.04,0.035时对应的X值,麻烦大神重新帮我算一下,拜托了,我不懂啊
Fluent学习中
4楼2014-02-27 11:29:47
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