Rotation of melting ice disks due to melt fluid flow

Area of Science:

• Fluid dynamics
• Thermodynamics
• Phase transitions

Background:

• Ice disks melting in water exhibit complex motion, including rotation.
• The relationship between water temperature and ice disk rotation speed is not fully understood.
• Understanding the fluid dynamics beneath melting ice is crucial for various applications.

Purpose of the Study:

• To investigate the physical mechanisms behind the rotation of melting ice disks.
• To analyze the fluid flow patterns beneath the ice disk during melting.
• To determine the influence of water temperature on ice disk rotational velocity.

Main Methods:

• Experimental setup involving melting ice disks (85 mm diameter, 14 mm height) in a thermalized water bath.
• Particle Image Velocimetry (PIV) technique to visualize and quantify fluid flow under the ice disk.
• Systematic variation of water bath temperature to observe its effect on rotation.

Main Results:

• Ice disks exhibited both translational and rotational motion during melting.
• Observed a direct correlation between increasing water bath temperature and increased ice disk rotation speed.
• PIV revealed a downward and horizontally rotating flow beneath the ice disk, forming a vertical vortex.

Conclusions:

• A mechanism involving maximum water density at 4°C generating a downward plume and subsequent vortex formation is proposed.
• The horizontal rotation of this vortex, through viscous entrainment, induces the solid-body rotation of the ice disk.
• The observed phenomenon is likely generic, applicable to any floating object subjected to vortex-generating vertical flows.