EFFECT OF NATURAL CONVECTION ON FREEZING IN A CAVITY

The cooling and subsequent freezing of the top layer of a body of water has been studied numerically. A simple freezing model is used assuming no water supercooling. The water is confined in a rectangular cavity with a free top surface subject to convective cooling. When water is cooled, through 4°C, the interesting phenomenon of flow pattern inversion is observed. As ice forms across the water surface, it is found that its profile is affected significantly by the convective currents underneath. The ice layer is thinner in locations where the current flows upward, thus convecting warmer water from the bottom to the surface. On the other hand, a thicker layer of ice is formed where the current moves downward. This effect is particularly pronounced when the water is cooled rapidly while slower cooling results in an ice layer which is quite uniform across the surface.