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solve second order time-derivative term equation
Posted Nov 25, 2011, 10:16 p.m. EST Version 4.2 1 Reply
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Hi! I'm sorry for my bad English.
I'm trying to solve the following equation.
(d^2 x)/(d t^2) + (a + b * cos(θ) )*x = 0
(d^2 x)/(d t^2) = second order time-derivative term
a,b = constant
x,θ = variables
I'm trying to solve this equation with Equation-Based Modeling (PDE interfaces).
But I can't understand how to solve it with COMSOL.
Does someone has any idea to solve this problem ?
Thanks a lot.
I'm trying to solve the following equation.
(d^2 x)/(d t^2) + (a + b * cos(θ) )*x = 0
(d^2 x)/(d t^2) = second order time-derivative term
a,b = constant
x,θ = variables
I'm trying to solve this equation with Equation-Based Modeling (PDE interfaces).
But I can't understand how to solve it with COMSOL.
Does someone has any idea to solve this problem ?
Thanks a lot.
1 Reply Last Post Nov 26, 2011, 12:21 p.m. EST
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Posted:
1 decade ago
Hi
COMSOL can only solve diff equatins fitting into the shapes ofthe general or coefficient form (which cover most "physics" induced phenomena.
So you need to reexpress your equations by separating them, clearly defining constans, coordinate variables and dependent variables. Sometimes also creating new dependent variables, particularly if you have higher order terms than the 2nd order, which understand is not you case.
--
Good luck
Ivar
COMSOL can only solve diff equatins fitting into the shapes ofthe general or coefficient form (which cover most "physics" induced phenomena.
So you need to reexpress your equations by separating them, clearly defining constans, coordinate variables and dependent variables. Sometimes also creating new dependent variables, particularly if you have higher order terms than the 2nd order, which understand is not you case.
--
Good luck
Ivar