Discussion Forum

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