Mesoscopic simulations of a molten sand droplet spreading on thermal barrier coatings under non-isothermal conditions*

The deposition, infiltration and the ensuing solidification of molten sand on the thermal barrier coating (TBC) of gas turbine engine components alters the thermal properties of the TBC causing severe damage. The mesoscopic dynamics of a highly-viscous molten sand droplet spreading on a smooth TBC surface are investigated under non-isothermal conditions using the energy-conserving dissipative particle dynamics (eDPD) framework in conjunction with the many-body interactions to model the multiphase effects. Following the experiments conducted at the Army Research Laboratory, the droplet is subjected to a linear ramp-up of temperature from 1140 degrees Celsius to 1260 degrees Celsius where it is held constant till the end of the simulation. The contact angle obtained from the experiments is used to calibrate the contact angle in the eDPD simulations. The eDPD system is carefully parameterized to model the temperature-dependent non-linear viscosity of the molten sand droplet by setting the exponent of the weighting function as a function of temperature. The temporal evolution of the spreading radius and the corresponding scaling laws are evaluated for different drop sizes and final equilibrium contact angles and compared to previously obtained results from isothermal spreading on a smooth surface.