In this paper we present numerical simulations of two-dimensional turbulent convection on a hemisphere. Recent experiments on a half soap bubble located on a heated plate have shown that such a configuration is ideal for studying thermal convection on a curved surface. Thermal convection and fluid flows on curved surfaces are relevant to a variety of situations, notably for simulating atmospheric and geophysical flows. As in experiments, our simulations show that the gradient of temperature between the base and the top of the hemisphere generates thermal plumes at the base that move up from near the equator to the pole. The movement of these plumes gives rise to a two-dimensional turbulent thermal convective flow. Our simulations turn out to be in qualitative and quantitative agreement with experiments and show strong similarities with Rayleigh-Bénard convection in classical cells where a fluid is heated from below and cooled from above. To compare to results obtained in classical Rayleigh-Bénard convection in standard three-dimensional cells (rectangular or cylindrical), a Nusselt number adapted to our geometry and a Reynolds number are calculated as a function of the Rayleigh number. We find that the Nusselt and Reynolds numbers verify scaling laws consistent with turbulent Rayleigh-Bénard convection: Nu ∝ Ra 0.31 and Re ∝ Ra 1/2 . Further, a Bolgiano regime is found with the Bolgiano scale scaling as Ra −1/4 . All these elements show that despite the significant differences in geometry between our simulations and classical 3D cells, the scaling laws of thermal convection are robust.

A simple dye-tracing method was developed to monitor the kinetic process of water penetration in chicken filets subjected to rotary tumble marination. A total of 860 chicken breast filets were tumbled for 0, 5, 15, and 30 min in marinades containing 1.6 or 3.2% sodium PP, TPP, or HMP with or without 8% NaCl. Marinade penetration was monitored by tracing a dye (FD&C Blue No. 1) migrating into different layers of the filets using a spectrophotometric measurement (absorbance at 627 nm). Marinades penetrated most rapidly in the initial 5 min, e.g., PP, TPP, and HMP at a low level (1.6%) enhancing the rate of penetration of unsalted water in the first 5 min by 196, 171, and 138%, respectively. However, the effect of phosphates was diminished when their concentration was high (3.2%) or when salt was present. Overall, low-level (1.6%) phosphates facilitated water penetration deep into the filets, whereas high-level (3.2%) phosphates and salt improved water penetration in the surface layers of the filets.

Phase change material (PCM) is one of the most important ways to store and manage energy. The melting process of PCM in a rectangular enclosure with the different aspect ratio is frequently related to some thermal energy storage devices. In this work, the melting of PCM in the horizontal rectangular enclosures heated from the different sides and the influence of aspect ratio of the rectangle are carefully studied. The enthalpy porosity technique and the finite volume method (FVM) are used to simulate the melting process numerically. The results show that the melting process of PCM can be dominated by conduction or natural convection due to the different heated sides. The melting of PCM in the enclosure heated from the bottom side is firstly affected by conduction and then mostly influenced by convection. In addition, the aspect ratio of the rectangular enclosure is found to play an important role in the melting process. Finally, a series of fitting correlations of the liquid fraction, Nusselt number and the energy storage are presented with the influence of aspect ratios in order to provide the reference for designing the rectangular container of PCM. This study is helpful for the selection of an appropriate aspect ratio and heating method to achieve the desired energy storage performance of encapsulated PCM.

Abstract