[Gopal, Jan]
For the past couple of days, Jan and I have been discussing a major issue in COMSOL involving **modeling both oscillatory and non-oscillatory forces simultaneously while using FDA**. It turns out that he and I had run into the same problem at different times and with different projects. After discussing with an expert, Jan had decided in the past that this simple task was **impossible** via direct means.
The issue could still be resolved if there was a way for us to work on the **Weak Form **of the differential equations describing the system:
- Usually, one must define weight as a body load in the negative-z direction. However, this problematically instantiates a new force in COMSOL, which is automatically driven over the range of frequencies during FDA.
- Instead, we could define gravity as an anti-restoring force, since we assume that the base of the stack is fixed.
- In other words,
* ***F**_{g} = (ρ*g/L)*x + (ρ*g/L)*y for a point mass which is constrained on the bottom (for small angles).
- Working in Weak Form then, we'd never have to define an explicit gravity load-- this could just be an extra couple of terms in the differential equation which are related entirely to the x- and y-vectors (well-defined for each mesh point). This would
**fool COMSOL into never tacking on the oscillatory term** during FDA.
According to current documentation however, **Weak Form analysis is not yet possible in COMSOL 4.0**. Jan suggested moving my work over to ANSYS or waiting for the 4.0 upgrade, but there's probably not enough time left in my SURF for either of these options. I suggested attempting a **backwards-compatibility test to COMSOL 3.5**; Jan and I will be exploring this option some time next week. |