How to add more than one conditions for an ode45 problem?

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Purush otham
Purush otham 2018-5-12
编辑： Purush otham 2018-5-12
Hi, This is my code in which 'b','phi' and 'VOLUME' are present:
format long
%input your entries here
density=1;%kg/m3
gravity=9;%m/s2
tension=46.5;%kg/s2
beta=(density*gravity)/tension;
for b=0:0.5:2
xini=1e-10;
zini=1e-10;
phiini=0;
phifin=150;
stepsize=1e-2;
V=1;
%code begins
phi1=deg2rad(phiini);
phi2=deg2rad(phifin);
f=@(phi,x)[b*cos(phi)/(2+beta*(x(2)/b)-(sin(phi)/(x(1)/b)));(b*sin(phi))/(2+beta*(x(2)/b)-(sin(phi)/(x(1)/b)))];
[phi,xa]=ode45(f,[phi1:stepsize:phi2],[xini zini]);
%Volume calculation
X=xa(:,1);
Z=xa(:,2);
VOLCUM=cumtrapz(Z,X);
position=find(VOLCUM<=V,1,'last');
VOLUME=VOLCUM(position)
My intention is to find the 'b' that gives me the required 'VOLUME' as well as 'phi' In other words, I want the code to loop until it gives me that 'b' which has 'VOLUME=1' and 'phi=60'. I am not sure how to proceed.
  2 个评论
Jan
Jan 2018-5-12
编辑：Jan 2018-5-12
The question is not clear. You want to get a "required V", but V is defined as a variable already. while is not an "operator" and I have no idea, where you want to apply &&. It is not clear, why you apply cumtrapz after the integration. Are you sure that this is useful?
Maybe you want to write a single-shooting method to estimate a parameter?
By the way: a:b:c is a vector already. There is no need to use [] for a horizontal concatenation.
Purush otham
Purush otham 2018-5-12
Hi thanks for your comment. Edited the original question. The three major parameters here are: 'phi','b' and 'VOLUME'.
My intention is to predefine 'VOLUME' and 'phi' and get the required 'b'.
The use of cumtrapz here is to find the area under plot. (%The final value of cumtrapz is same as trapz)

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