  This study develops a computationally efficient phase-field lattice Boltzmann
model with the capability to simulate thermocapillary flows. The model was
implemented into the open-source simulation framework, waLBerla, and extended
to conduct the collision stage using central moments. The multiphase model was
coupled with both a passive-scalar thermal LB, and a RK solution to the energy
equation in order to resolve temperature-dependent surface tension phenomena.
Various lattice stencils (D3Q7, D3Q15, D3Q19, D3Q27) were tested for the
passive-scalar LB and both the second- and fourth-order RK methods were
investigated. There was no significant difference observed in the accuracy of
the LB or RK schemes. The passive scalar D3Q7 LB discretisation tended to
provide computational benefits, while the second order RK scheme is superior in
memory usage. This paper makes contributions relating to the modelling of
thermocapillary flows and to understanding the behaviour of droplet capture
with thermal sources analogous to thermal tweezers. Four primary contributions
to the literature are identified. First, a new 3D thermocapillary,
central-moment phase-field LB model is presented and implemented in the
open-source software, waLBerla. Second, the accuracy and computational
performance of various techniques to resolve the energy equation for
multiphase, incompressible fluids is investigated. Third, the dynamic droplet
transport behaviour in the presence of thermal sources is studied and insight
is provided on the potential ability to manipulate droplets based on local
domain heating. Finally, a concise analysis of the computational performance
together with near-perfect scaling results on NVIDIA and AMD GPU-clusters is
shown. This research enables the detailed study of droplet manipulation and
control in thermocapillary devices.
