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A novel treatment of fractional-time derivative using the incompressible smoothed particle hydrodynamics (ISPH) method is introduced to simulate the bioconvection flow of nano-enhanced phase change materials (NEPCM) in a porous hexagonal cavity. The fractional-time derivative is based on the Caputo style, which reflects the fractional order behavior in complex systems. In this work, the circular rotation of the embedded four-pointed star and the motion of oxytactic microorganisms in a hexagonal cavity are conducted. Due to the significance of fractional derivatives in handling real physical problems with more flexibility than conventional derivatives, the present scheme of the ISPH method is developed to solve the fractional-time derivative of the bioconvection flow in a porous hexagonal cavity. This study implicates the variations of a fractional-time derivative, a parametric of an inner four-pointed star, and the pertinent physical parameters on the behavior of a bioconvection flow of a nanofluid in a hexagonal-cavity containing oxytactic microorganisms. The presence of microorganisms has a significant role in many biological, engineering, and medical phenomena. From the present numerical investigation, it is well mentioned that the computational time of the transient processes can be reduced by applying a fractional-time derivative. The variable sizes of an inner four-pointed star enhance the bioconvection flow in a hexagonal cavity.

A novel treatment of fractional-time derivative using the incompressible smoothed particle hydrodynamics (ISPH) method is introduced to simulate the bioconvection flow of nano-enhanced phase change materials (NEPCM) in a porous hexagonal cavity. The fractional-time derivative is based on the Caputo style, which reflects the fractional order behavior in complex systems. In this work, the circular rotation of the embedded four-pointed star and the motion of oxytactic microorganisms in a hexagonal cavity are conducted. Due to the significance of fractional derivatives in handling real physical problems with more flexibility than conventional derivatives, the present scheme of the ISPH method is developed to solve the fractional-time derivative of the bioconvection flow in a porous hexagonal cavity. This study implicates the variations of a fractional-time derivative, a parametric of an inner four-pointed star, and the pertinent physical parameters on the behavior of a bioconvection flow of a nanofluid in a hexagonal-cavity containing oxytactic microorganisms. The presence of microorganisms has a significant role in many biological, engineering, and medical phenomena. From the present numerical investigation, it is well mentioned that the computational time of the transient processes can be reduced by applying a fractional-time derivative. The variable sizes of an inner fourpointed star enhance the bioconvection flow in a hexagonal cavity. [ABSTRACT FROM AUTHOR]

[Display omitted] • A perfect selective metamaterial absorber with four-pointed star prisms is proposed. • Mechanisms for the perfect spectral selectivity of the absorber are revealed. • High efficiencies of 92.31–77.78% are achieved at 1000 suns and 1273–1673 K. • The absorber exhibits good insensitivities to the polarization and incident angles. Selective absorber is an important component for enhancing the solar-to-heat efficiency in high-temperature solar applications. In this paper, a selective metamaterial absorber possessing four-pointed star prisms was proposed and studied. Firstly, an optimal metamaterial absorber with perfect spectrally selective performance was obtained after optimizing the structure. It was found that the optimal absorber can achieve the high total solar absorptance of 0.958 and the low total emittance of 0.2355–0.4062, thus obtaining the high solar-to-heat efficiency of 92.31%-77.78% at 1000 suns and 1273–1673 K. Secondly, the underlying mechanisms for the good spectral selectivity of the optimal absorber were analyzed. The results showed that the high spectral absorptance in the solar spectrum owes to the impedance matching and the coupling effects of different plasmonic modes. The low spectral emittance within the mid-infrared band can be explained by the impedance mismatching. Thirdly, the effects of the geometrical parameters on the spectral selectivity of the absorber were studied, indicating that the height of the SiO 2 layer above the star and the short diagonal length of the rhomb influence little on the spectral absorptance when they are in certain ranges. However, other parameters have obvious influences on the spectral absorptance. Finally, study on the effects of the polarization angle and incident angle indicated that the optimal absorber exhibits good insensitivities to the polarization angle and the incident angle. These results indicate that the proposed perfect absorber is a promising candidate for high-temperature solar applications. [ABSTRACT FROM AUTHOR]