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Vehicular ad hoc networks (VANETs) are a fundamental component of intelligent transportation systems in smart cities. With the support of open and real-time data, these networks of inter-connected vehicles constitute an 'Internet of vehicles' with the potential to significantly enhance citizens' mobility and last-mile delivery in urban, peri-urban, and metropolitan areas. However, the proper coordination and logistics of VANETs raise a number of optimization challenges that need to be solved. After reviewing the state of the art on the concepts of VANET optimization and open data in smart cities, this paper discusses some of the most relevant optimization challenges in this area. Since most of the optimization problems are related to the need for real-time solutions or to the consideration of uncertainty and dynamic environments, the paper also discusses how some VANET challenges can be addressed with the use of agile optimization algorithms and the combination of metaheuristics with simulation and machine learning methods. The paper also offers a numerical analysis that measures the impact of using these optimization techniques in some related problems. Our numerical analysis, based on real data from Open Data Barcelona, demonstrates that the constructive heuristic outperforms the random scenario in the CDP combined with vehicular networks, resulting in maximizing the minimum distance between facilities while meeting capacity requirements with the fewest facilities. [ABSTRACT FROM AUTHOR]

Nanorefrigerants have attracted the attention of refrigeration scientists and engineers across the globe during the last decade. They demonstrated some promising aspects like enhanced pool boiling and convective heat transfer coefficients, lead to produce smaller and more affordable refrigeration equipment. A comprehensive and useful review about the numerical studies of nanorefrigerants has been reported in this paper. Results show that thermal performance of nanorefrigerants is a function of nanoparticle concentration and also they introduce more pressure drop as a penalty. Nonetheless, it seems that more numerical studies are needed to make a valid and comprehensive outlook about this type of heat transfer fluids, especially where the experimental studies are not possible or affordable. Furthermore, a predicting correlation has been introduced for the nanorefrigerants thermal conductivity based on statistical analysis using the numerical data provided in the literature. Unlabelled Image • Thermal performance of nanorefrigerants is a function of nanoparticle concentration. • Sharp increase in pressure drop as a function of nanoparticle volume concentration. • Most of numerical studies have been performed under the single-phase approach. • A new correlation for thermal conductivity has been introduced using MVR method. [ABSTRACT FROM AUTHOR]

This paper concerns the Lattice Boltzmann Method (LBM) which has recently become alternative, computationally efficient tool to simulate a Newtonian fluid flow, especially in complex geometries. A series of benchmark two-dimensional simulations with the LBM are presented and analyzed in order to assess the impact of the LBM grid refinement on the results of the simulations. The considered cases include stationary and time-dependent flows past a circular or a 45-degree rotated square cylinder confined in the channel with parallel walls. Next, the same flow configurations are investigated by means of the Spectral Element Method (SEM) and obtained results are used to cross-validate both approaches. The sensitivity to the resolution of representation of the obstacle's shape in the LBM simulations is of the main interest. Particular attention is paid also to the effects of compressibility of the flow. Additionally, for unsteady flows the transient flow characteristics are compared in detail: the velocity profiles from the LBM and SEM are presented and some non-dimensional characteristics such as Strouhal number of the compared von Karman vortex streets. [ABSTRACT FROM AUTHOR]