Experimental research on flow patterns of liquid-solid two-phase thermocapillary convection inside a liquid bridge

Micron-scale inclusions significantly compromise the crystal quality during the floating zone growth processes, yet their dynamic interaction with thermocapillary convection remains insufficiently understood due to the lack of internal flow field measurements. To address this, this study employs Particle Image Velocimetry (PIV) with 5 × 10 −6 m 2 /s kinematic viscosity silicone oil to investigate the liquid-solid two-phase flow dynamics in a half-zone liquid bridge. The side-view analysis reveals velocity fields and spatiotemporal evolution of liquid-solid two-phase thermocapillary convection. Experimental results demonstrate that increasing the temperature difference (Δ T ) from 5 °C to 35 °C shortens the flow recovery time ( t 2 ) by approximately 21.2% (from 78.56 s to 61.88 s), effectively accelerating flow stabilization. Conversely, the onset of buoyancy-driven convection is advanced, with the emergence time ( t 1 ) decreasing from 12.48 s to 5.16 s. Increasing the volume ratio ( Vr ) from 0.7 to 0.85 reduces the emergence time of buoyancy cells by 2.45 s, confirming that convex interfaces strengthen buoyancy effects. Regarding geometric constraints, increasing the aspect ratio ( Ar ) from 0.5 to 1 delays the recovery to steady state by approximately 15% (from 61.08 s to 70.24 s) due to the formation of a smaller-diameter neck which reduces the axial thermal conductivity. Oscillations exhibit asynchronous modes without buoyant vortices at low Vr = 0.5 - 0.6, while at Vr = 0.7 - 0.85, synchronous modes evolve into asynchronous modes with buoyant vortices gradually vanishing under diagonal fluid compression. Top-view observations under large temperature differences reveal the non-uniform particle distribution. Specifically, a clockwise-rotating triangular flow ( m = 3) at Ar = 0.75 with an oscillation period Γ = 11.90 s, and an elliptical flow ( m = 2) at Ar = 1 ( Γ = 12.96 s). By quantifying these oscillation characteristics and particle accumulation structures, this work establishes a foundation for inclusion removal in industrial monocrystalline silicon manufacturing. • High temperature (Δ T ) shortens recovery time by 21.2%. • Convex interfaces ( Vr = 0.85) intensify buoyancy via steeper gradients. • Geometric constraints ( Ar = 1) extend rotating flow duration by 33.7%. • Higher supercriticality at Ar = 1 boosts peak velocity by 36%. • Particle drag reduces experimental velocity by 10-15% vs predictions.