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A Physical and Mathematical Study of the
Supercooling Process and Frazil Evolution

Shi-Qiang, Ye

Abstract
The supercooling of water in nature and the associated production of frazil can have a profound impact on the management of water resources infrastructure in cold regions. Herein, a series of experiments were carried out using the unique counter-rotating flume that is housed in a computer controlled cold room. A Digital Image Process System (DIPS) was used to observe frazil ice processes. In particular, the effects of air temperature, flow velocity, and bottom roughness on the supercooling and frazil ice processes were examined.

Based on these experimental findings and previous research, a new approach for the supercooling process and frazil evolution is proposed. The principal supercooling process is defined as a process whereby frazil formation reaches the entrained frazil generating capacity of the flow. The residual supercooling stage represents, therefore, a two-layer frazil ice stage, involving both entrained and surface frazil ice. The model describing the frazil size and its distribution in flows is developed based on characteristics of the flow turbulence. Furthermore, in analogy to suspended sediment transport, an equation estimating the entrained frazil generating capacity of a flow is proposed, which is governed by air temperature and flow turbulence.

A numerical model for the supercooling process and frazil ice evolution is developed. The model avoids the need to simulate seeding, secondary nucleation, flocculation/break-up, and gravitational removal. Only the overall heat balance is considered; consequently, less assumptions and calibrated parameters are needed. The model successfully simulates the characteristics of frazil ice evolution and the supercooling process of water, and as well as the vertical distribution of frazil ice. Sensitivity analysis shows that the cooling rate, the initial ice concentration assumed, and the bed friction factor are much more sensitive than other hydraulic parameters.

This new approach provides an opportunity to estimate the frazil ice characteristics and supercooling period under varying thermo-hydraulic conditions in practical engineering. Besides, the approach and its concepts can be considered fundamentals to various river ice problems, and can be extended to develop models for anchor ice growth during the supercooling process.

Click Images To Enlarge

Sontek Acoustic Doppler Velicometer (ADV) attatched to a DMC-400 motion controller. Used to measure the 3 components of velocity.

Video

The counter-rotating flume used in Ye's research

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