Direct numerical simulation of solidifying liquid turbulence using the phase-field model

We realized a direct numerical simulation (DNS) of the turbulent flow of liquid along a solid wall with solidification by incorporating the phase-field model. The combination of DNS and phase-field model can clarify the mechanism of modulation of a turbulent boundary layer of liquid solidifying upon a solid wall and assist in constructing a prediction method in the future. The simulations allow observation of turbulent flow along a solid wall surface that grows with the solidification of a flowing liquid under an undercooling condition. In the flow field, turbulence structures such as velocity streaks and quasi-streamwise vortices were noted to diminish, and the turbulent flow tended to be laminar. In contrast, there were no changes in the turbulence statistics in the region above the growing solid–liquid interface. The solidification structure had a bent shape, which was caused by the e ff ects of advection downstream and growing in the upstream direction owing to the undercooled fluid flowing from upstream. The wall surface grew non-uniformly depending on the local flow patterns and temperature distribution caused by turbulence structures close to the wall surface. The complex shape of the wall surface, which was observed during simulation, was originally triggered by the initial distribution of the turbulence structures. Sweep events in the high-speed streaks relatively expedited the growth of the solidification structures, which then modified the turbulence structures. The interaction between the turbulence structure and solidification structure promotes laminarization of the fluid flow.