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jindan8865

铜虫 (小有名气)

[求助] matlab 三重数值积分 已有1人参与

自己按这个公式写了一个三重积分,用的int函数,但一直warning。
     Z1u=sqrt(2*Rs*r1*cos(theta1)-r1^2);
      r1l = sqrt(R(j)^2-(Rp^2*sin(theta2)^1)-Rp*cos(theta1);
      r1u = 2*Rs*cos(theta1);
      theta1u = acos(sqrt((R(j)^2-Rp^2)/(4*Rs*(2*Rp))));
      V(j) = 4*int(int(int(1,z1,0,Z1u)*r1,r1,r1l,r1u),theta1,0,theta1u);
    希望大神能给一个三重数值积分的代码。
    多谢!

matlab 三重数值积分
IMG_1282(20170312-161908).jpg
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jindan8865

铜虫 (小有名气)

引用回帖:
2楼: Originally posted by tuburfransth at 2017-03-12 18:02:37
syms Rs r1 theta1 Rn Rp
z1u = sqrt(2*Rs*r1*cos(theta1) - r1^2);
r11 = sqrt(Rn^2 - Rp^2*(sin(theta1)^2)) - Rp*cos(theta1);
r1u = 2*Rs*cos(theta1);
theta1u = acos(sqrt((Rn^2 - Rp^2)/(4*Rs*(Rs + Rp) ...

感谢您的回贴!多谢

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4楼2017-03-12 19:46:52
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tuburfransth

金虫 (正式写手)

【答案】应助回帖

★ ★ ★ ★ ★ ★
感谢参与,应助指数 +1
jjdg: 金币+1, 辛苦了 2017-03-12 22:06:45
jindan8865: 金币+5, ★有帮助 2017-03-22 09:03:01
syms Rs r1 theta1 Rn Rp
z1u = sqrt(2*Rs*r1*cos(theta1) - r1^2);
r11 = sqrt(Rn^2 - Rp^2*(sin(theta1)^2)) - Rp*cos(theta1);
r1u = 2*Rs*cos(theta1);
theta1u = acos(sqrt((Rn^2 - Rp^2)/(4*Rs*(Rs + Rp))));
Vn = int(int(int(r1, r1, 0, z1u), Rs, r11, r1u), Rn, 0, theta1u)
#--------------------------------------------------------------------
Warning: Explicit integral could not be found.

Vn =

int(- (Rp*cos(theta1) - (Rn^2 - Rp^2*sin(theta1)^2)^(1/2))*(r1^2/2 + (cos(theta1)*(Rp*cos(theta1) - (Rn^2 - Rp^2*sin(theta1)^2)^(1/2))*r1)/2) - 2*Rs*cos(theta1)*(r1^2/2 - Rs*r1*cos(theta1)^2), Rn == 0..acos(((Rn^2 - Rp^2)/(4*Rs*(Rp + Rs)))^(1/2)))
#----------------------------------------------------------------------
看结果,貌似无法得到显式积分结果
2楼2017-03-12 18:02:37
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jindan8865

铜虫 (小有名气)

引用回帖:
2楼: Originally posted by tuburfransth at 2017-03-12 18:02:37
syms Rs r1 theta1 Rn Rp
z1u = sqrt(2*Rs*r1*cos(theta1) - r1^2);
r11 = sqrt(Rn^2 - Rp^2*(sin(theta1)^2)) - Rp*cos(theta1);
r1u = 2*Rs*cos(theta1);
theta1u = acos(sqrt((Rn^2 - Rp^2)/(4*Rs*(Rs + Rp) ...

我之前写的那个也是这个警告。我百度了一下可能是因为得不到解析解,得用其他的函数来求数值解

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3楼2017-03-12 19:44:42
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