Comment on'Quasi liquid layer-pressure asymmetrical model for the motion of of a curling rock on ice surface'

​​​​​​​Bingmiao Liu

Introduction

The motion of a curling rock on an ice surface presents a fascinating and longstanding scientific puzzle. Despite numerous models attempting to explain this phenomenon, no model has been able to offer a comprehensive, quantitative solution. In their recent work, Hao and Wang (2023) propose a new approach — the quasi-liquid layer-pressure asymmetrical model — to better understand the lateral motion of the curling rock on ice. This model suggests that the curling rock's motion is influenced by a quasi-liquid layer, which provides a novel perspective on the interaction between the ice and the rock’s surface. In this comment, we aim to critically assess the proposed model and its implications for the understanding of curling dynamics.

Summary of Hao and Wang's Model

The key assertion of Hao and Wang's (2023) model is that the asymmetrical pressure distribution, arising from the quasi-liquid layer formed beneath the curling rock, is responsible for the observed lateral motion. This quasi-liquid layer, which forms due to the interaction of the rock's surface with the ice, is thought to exert varying pressure along different points of the rock. The resulting pressure differential causes a lateral force that directs the rock's path in a manner opposite to the expected trajectory on dry surfaces. This new model builds on the pebble model, which has been widely used to describe the behavior of curling rocks on ice, but it aims to provide a more detailed explanation by focusing on the molecular and surface-level interactions.

Strengths of the Model

1. Innovative Approach: The model introduces the concept of a quasi-liquid layer, which has not been a focal point in prior studies of curling rock dynamics. This aspect is particularly promising as it may offer a more direct link between the macroscopic motion of the rock and the microscopic interactions between ice and rock surfaces.

2. Refinement of Existing Models: By incorporating the quasi-liquid layer, the model provides an extension to the existing pebble model, offering a potential pathway to quantitatively explain the motion of curling rocks. The pressure asymmetry hypothesis may enhance the understanding of how lateral forces affect the trajectory.

3. Practical Implications: If validated, this model could have practical implications not only in improving the understanding of curling dynamics but also in enhancing the design of ice surfaces for the sport, and even applications in other fields involving frictional dynamics on smooth surfaces.

Critiques and Areas for Further Exploration

1. Model Validation: While the model is theoretically appealing, its practical validation remains a critical step. The authors present no experimental data to directly support the presence or behavior of the quasi-liquid layer. Future studies should aim to experimentally validate this concept by measuring the pressure distributions on the ice-rock interface during curling, perhaps using high-resolution imaging or force sensors.

2. Simplifications in the Model: One area of concern lies in the simplifications made in the modeling of the ice surface. Ice surfaces are not perfectly homogeneous, and various factors such as temperature gradients, surface roughness, and ice crystal orientations could influence the formation of the quasi-liquid layer. A more detailed treatment of these variables might improve the model’s accuracy.

3. Generalization of the Findings: The model's generalization to other sports or scenarios involving smooth, frictional surfaces could be explored. While the authors focus on curling, the principles may be applicable to other contexts, such as the motion of balls in sports like bowling or the behavior of sliding objects on icy roads. A more extensive exploration of these potential applications would be beneficial.

Conclusion

Hao and Wang's (2023) quasi-liquid layer-pressure asymmetrical model represents an innovative step forward in understanding the motion of curling rocks. By introducing a novel explanation based on molecular interactions at the ice-rock interface, the model has the potential to resolve long-standing questions in the dynamics of curling. However, further experimental validation and refinement of the model are necessary to confirm its applicability and accuracy. Future research should focus on experimental studies to test the assumptions made by the model and explore its broader applicability.

References

1. Hao, Yuze, and Yueqi Wang. "Quasi liquid layer-pressure asymmetrical model for the motion of a curling rock on ice surface." arXiv preprint arXiv:2302.11348 (2023).
2. Hao, Yuze, and Yueqi Wang. "Quasi liquid layer-pressure asymmetrical model for the motion of a curling rock on ice surface." arXiv e-prints (2023): arXiv-2302.
3. Hao, Yuze, and Yueqi Wang. "Quasi liquid layer-pressure asymmetrical model for the motion of a curling rock on ice surface." ScienceOpen Preprints (2023).
4. Liu, Bingmiao. "Analyzing the Dynamics of Curling: Insights from the Quasi Liquid Layer-Pressure Asymmetrical Model." ScienceOpen Preprints (2024).
5. Liu, Bingmiao. (2025). Analyzing the Dynamics of Curling: Insights from the Quasi Liquid Layer-Pressure Asymmetrical Model. Zenodo. https://doi.org/10.5281/zenodo.14784015