Coupled sloshing in hyperbolic containers suspended as a bifilar pendulum

The coupled interaction between a sloshing fluid in a partially-filled container suspended as a bifilar pendulum is investigated. The sloshing fluid has a free-surface upon which waves are generated this fluid contributes a restoring force to the container motion by its weight through the wire suspensions and the free-surface waves may either enhance or diminish the restoring force through hydrodynamic interaction with the container walls. Results are presented for inviscid, irrotational sloshing in both a two-dimensional hyperbolic container and a threedimensional hyperboloid container. Frequency results for the coupled system are presented for various pendulum lengths and fluid fill heights. It is found that for long pendulum lengths the container and the fluid oscillate in a synchronous motion when the vessel is released with typical experimental initial conditions, but for pendulum lengths below a given threshold the container and fluid oscillate asynchronously from the same initial condition.