Numerical simulation of a silicon-based latent heat thermal energy storage system operating at ultra-high temperatures

Numerical simulations of solidification around two tandemly-arranged circular cylinders under forced convection

We present a numerical investigation of the deformation and breakup of a compound drop in shear flow. The numerical method used in this study is a two-dimensional front-tracking/finite difference technique for representing the interface separating two fluids by connected elements. The compound drop with the initially circular and concentric inner and outer fronts is placed at the center of a domain whose top and bottom boundaries move in the opposite direction. Because of the shear rate, the compound drop deforms and can break up into drops, depending on the flow conditions based on the Reynolds number Re, the Capillary number Ca and the interfacial tension ratio σ21 of the outer to inner interfaces. We vary Re in the range of 0.1-3.16, Ca in the range of 0.05-0.6 and σ21 in the range of 0.8-3.2 to reveal the transition from the non-breakup to breakup regimes. Numerical results indicate that the compound drop breaks up into drops when there's an increase in Re or Ca or a decrease in σ21 beyond the corresponding critical values. We also propose a phase diagram of Ca versus Re that shows the region in which the compound drop changes from the deformation mode to the breakup mode.

Numerical investigation of dynamic behavior of a compound drop in shear flow

Fully resolved simulations of drop solidification under forced convection

Numerical modeling of three-phase flow with phase change using the level-set method

We present numerical investigations of solidification around a cooled circular cylinder in the presence of forced convection. The numerical method is based on the front-tracking/finite difference and interpolation techniques. The solidification interface is represented by connected elements that move on a fixed, rectangular grid. The no-slip and Dirichlet temperature boundary conditions are imposed by the linear interpolation. The interpolation method was first validated through comparisons of the present results with some other numerical results for flow in an annulus, flow in an enclose with a conduction solid body and flow over a heated cylinder. We then used the method to investigate the solidification process around a cold cylinder by varying various parameters such as the Reynolds number Re, the Prandtl number Pr, the Stefan number, the thermal conductivity ratio k
 sl
 , the non-dimensional temperature of the introduced liquid θ
 0, and the solid-to-liquid density ratio ρ
 sl
 . Numerical results indicate that an increase in any of Re, Pr and θ
 0 results in a decrease in the area of the solidification region around the cylinder. In contrast, increasing k
 sl
 increases the region of the solid phase. Investigation on St and ρ
 sl
 reveals that the solidification rate increases with an increase in St or a decrease in ρ
 sl
 . However, St and ρ
 sl
 have a minor effect on the final product of the solidification process.

Numerical investigations of solidification around a circular cylinder under forced convection

The lossy nature of wireless communication leads to many challenges in designing multi-hop sensor networks. As an integral part of routing protocols, effective link estimation is essential for reliable communication. In this paper, we conduct a detailed performance analysis of several representatives of link estimators in the interplay with Collection Tree Protocol. The evaluation process has been carried out a test-bed of real nodes running ContikiOS. We also improve the Direct Estimate estimator to show the importance of acknowledgement delivery in reliable communication. The resulting extend-Direct Estimate shows better performance. We final conclude some suggestions of using which links estimator for which kind of applications.

Anh V. Truong

Papers

Numerical investigations of solidification around a circular cylinder under forced convection

Performance study of link estimation in static wireless sensor networks