# second order ode45-where to put boundary and initial condition?

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I G on 7 May 2018
Answered: Torsten on 8 May 2018
I am solving this equation with ode45 method, p0 is already known:
4B*d^2u/dr^2+(4B/r)*du/dr=dp0/dz
and I have two conditions,
initial condition: r=0: du/dr=0;
boundary condition where r=1: u=0.
Where to put these conditions, because I can put initial condition in ode45 solver, but where to put boundary condition in this case?
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### Answers (1)

Torsten on 8 May 2018
u(r) = -1/(16*B)*dp0/dz*(1-r^2)
If the analytical solution is not what you want, use "bvp4c" instead of "ode45".
Best wishes
Torsten.
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