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High oder Equation-Weak Form
Posted Feb 24, 2012, 5:12 p.m. EST 1 Reply
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Hi all,
I am going to implement a 4th order equation in Comsol using weak form. The equation is the simple beam equation (∂^4 w)/(∂x^4 )=(1/c^2)*(∂^2 w)/(∂t^2 ).
The one equation would have 3 natural boundary conditions (Shear (∂^3 w)/(∂x^3 ) , Moment (∂^2 w)/(∂x^2 ), slope (∂w)/(∂x).
By applying the equation in weak form I would have: wxx*test(wxx)+((1/c^2)*wtt*test(w)
1) I am wondering if this way of implementing allow me to have all 3 naturtal boundary conditions available in the model.
(It seems this only allow me to apply 1 natural boundary condition.)
2) Should I again for weak form I reduce the order of equation in order that the comsol be able to solve the model?
(First I tried to implement the equation in PDE general format but It was not a good idea as it could not have all the boundary conditions)
Thanks for any comment.
Masoud
I am going to implement a 4th order equation in Comsol using weak form. The equation is the simple beam equation (∂^4 w)/(∂x^4 )=(1/c^2)*(∂^2 w)/(∂t^2 ).
The one equation would have 3 natural boundary conditions (Shear (∂^3 w)/(∂x^3 ) , Moment (∂^2 w)/(∂x^2 ), slope (∂w)/(∂x).
By applying the equation in weak form I would have: wxx*test(wxx)+((1/c^2)*wtt*test(w)
1) I am wondering if this way of implementing allow me to have all 3 naturtal boundary conditions available in the model.
(It seems this only allow me to apply 1 natural boundary condition.)
2) Should I again for weak form I reduce the order of equation in order that the comsol be able to solve the model?
(First I tried to implement the equation in PDE general format but It was not a good idea as it could not have all the boundary conditions)
Thanks for any comment.
Masoud
1 Reply Last Post Feb 24, 2012, 5:39 p.m. EST
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Posted:
1 decade ago
Hi
should you add a independent variable such to have two sets of 2nd order equations, then you can use the standard notation and define enough BC, no ?
--
Good luck
Ivar
should you add a independent variable such to have two sets of 2nd order equations, then you can use the standard notation and define enough BC, no ?
--
Good luck
Ivar