A multi-distribution lattice Boltzmann Bhatnagar–Gross–Krook (BGK) model with a multiple-grid lattice Boltzmann (MGLB) model is proposed to efficiently simulate natural convection over a wide range of Prandtl numbers. In this method, different grid sizes and time steps for heat transfer and fluid flow equations are chosen. The model is validated against natural convection in a square cavity, since extensive benchmark solutions are available for that problem. The proposed method can resolve the computational difficulty in simulating problems with very different time scales, in particular, when using extremely low or high Prandtl numbers. The technique can also enhance computational speed and stability while keeping the simplicity of the BGK method. Compared with the conventional lattice Boltzmann method, the simulation time can be reduced up to one-tenth of the time while maintaining the accuracy in an acceptable range. The proposed model can be extended to other lattice Boltzmann collision models and three-dimensional cases, making it a great candidate for large-scale simulations.
At present, the lithium-ion battery (LIB) is the most important candidate for electrical energy storage for different applications, including electric and hybrid vehicles and aircraft. Although many studies have been done so far to evaluate performance and durability of LIB cells and packs for vehicle application, there is no study for the application of LIBs in electric and hybrid aircraft. In this paper, the cycle life and calendar life of a typical aftermarket LIB are studied through an empirical modeling method. The degradation rate of the battery for a typical light-weight passenger aircraft with a flight range of less than 1000 km is presented. The real duty-cycle of the battery for this aircraft is used for the cycle-life analysis.
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