Discussion Forum

Krupali,

Scattering Boundary Condition is used to avoid back reflection of the outgoing wave from the exterior boundary of your computational domain. In another words, this boundary condition makes a boundary transparent for the outgoing waves.

Scattering Boundary Condition can also be used to lunch source (incident) wave from the boundary.

Regards,
Sergei

thank you sir for your reply.

Still I am confused that how PML and scattering boundary conditions differ from each other?when should I use PML and when scattering boundary condition?

Krupali,

You can use either Scattering Boundary Condition or PML in frequency domain. PML might give you more accurate solution since plane wave is partially reflected at oblique incidence for Scattering BC. PML is not particularly sensitive to the shape of the wave fronts.

PML is not available in time domain. Thus, Scattering BC is the only choice in time domain.

Regards,
Sergei

ok...thank you so much.this is really helpful to me.

I want to understand physics behind PML..Actually I have read an equation in RF USED GUIDE that how comsol applies PML Layer.equation includes coordinate t..i can't understand what actually t means? what is its physical indication?

Hi,

Fundamentally there is one big difference between PML & Scattering Boundary Condition. First, the PML boundary condition is used where you are not actually concerned about the domains in the model (or virtual domain). For example if you have a wave propagating through air, the air region can be infinitely long. But you cannot model it as it will be tough to analyse. Hence you add a PML region in which the waves can propagate as if the air domain is infinitely long with minimal reflection or no reflections. The scattering boundary condition is the same but there is a slight difference to the way it is completely transparent to the incoming wave. This boundary condition is completely transparent for wave which are normal to the incident boundary. Therefore some waves will be reflected back as it hits the incident boundary.

Hi all

Does anybody knows how to set perfectly matched layer (PML) in boundary condition in electromagnetic wave time domain (teew)