specialize to pressure only

[arturgower]

ElasticWaves.jl/src/cylindrical/boundary_conditions.jl

Line 5 in bfcf59c

shear_field_mode(ω, r, bearing.medium, basis_order, bc.fieldtype)

The shear part needs to return an empty vector when the boundary condition type refers to pressure only. That way, the resulting matrix from the boundary_system will be the matrix for pressure only.

[arturgower]

ElasticWaves.jl/src/cylindrical/boundary_conditions.jl

Line 57 in bfcf59c

shear_coefficients = coefficients[:,3:4] |> transpose

Need to rewrite how ElasticWave works which currently always assumes there are shear waves.

[arturgower]

The specialisation to pressure only should come from the user giving the PhysicalMedium Acoustic. Should not mess around too much with the boundarytypes.