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439 results on '"Niu, Shichao"'

28. Numerical Simulation Analysis and Research on Drag Reduction and Stability Enhancement Effect of Head Swing Based on Biomimetic Flexible Variants.

Author

Qi, Debo, Li, Yang, Yang, Baisheng, Wu, Zhengyang, Li, Bo, and Niu, Shichao

Subjects
JETS (Fluid dynamics), SUPERHYDROPHOBIC surfaces, NUMERICAL analysis, OSCILLATIONS, COMPUTER simulation, DRAG reduction
Abstract

With the intensification of the oil crisis, research on drag reduction technologies has gained increasing momentum. In tidal environments, the drag reduction effectiveness of conventional methods, such as bionic non-smooth surfaces, super-hydrophobic surfaces, biomimetic jet flow, wall surface vibration, etc., will be severely diminished. To enhance the adaptability of vehicles in variable fluid environments, this study explores the feasibility of adjusting the drag of a vehicle through active head swing variants. The flexible oscillation of the head of the vehicle was achieved by combining dynamic mesh technology with User-Defined Functions (UDFs). The oscillation process was numerically simulated using Fluent software. The results show that, when the vehicle maintains a stationary posture, biasing the vehicle's head towards the incoming flow direction can effectively reduce the radial drag and drag moment, thereby improving the stability of the vehicle. Conversely, both the radial drag and the drag moment significantly increase. This condition can be utilized for the auxiliary turning of the vehicle. When the vehicle undergoes continuous periodic oscillation of its head, the drag characteristics are optimal with the sine oscillation mode. By adjusting the range of the head's oscillation angle, it can further minimize the average radial drag during the head swing process, making it possible to achieve radial drag reduction and enhance the vehicle's stability through head oscillation. This research significantly improves the stability of the vehicle in tidal environments, making it adaptable to the highly variable underwater flow conditions. [ABSTRACT FROM AUTHOR]

Published
2025
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37. Study on the Effect of Soft–Hard Material Interface Differences on Crack Deflection in Nacre-Inspired Brick-and-Mortar Structures.

Author

Wang, Yifan, Yang, Xiao, Niu, Shichao, Tang, Biao, and Shao, Chun

Subjects
MOTHER-of-pearl, FRACTURE toughness
Abstract

Nacre has excellent balanced strength and toughness. In this paper, the mechanical performance of the typical "brick-and-mortar" structure, including the stress–strain and strain at the interface as well as the stress in the bricks, was calculated by a simplified analytical model of the nacre. This paper proposes a new method to control the crack deflection based on the toughening mechanism of the nacre. The crack extension of the "brick-and-mortar" structure was simulated using cohesive elements based on the traction–separation law with elastic and softening stiffness as variables, and it was found that both stiffness could effectively control the crack extension. The strength and toughness of the models with different stiffness combinations were calculated and plotted as a function of elastic stiffness and softening stiffness, showing that elastic stiffness significantly affects strength and softening stiffness is a determinant of toughness. [ABSTRACT FROM AUTHOR]

Published
2024
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45. Designer SiO2 metasurfaces for efficient passive radiative cooling

Author

Universitat Politècnica de Catalunya. Departament de Màquines i Motors Tèrmics, Universitat Politècnica de Catalunya. CREMIT - Centre de Recerca de Motors i Instal·lacions Tèrmiques, Ding, Zhenmin, Li, Honglin, Li, Xin, Fan, Xueying, Jaramillo Fernández, Juliana, Pattelli, Lorenzo, Zhao, Jiupeng, Niu, Shichao, Li, Yao, Xu, Hongbo, Universitat Politècnica de Catalunya. Departament de Màquines i Motors Tèrmics, Universitat Politècnica de Catalunya. CREMIT - Centre de Recerca de Motors i Instal·lacions Tèrmiques, Ding, Zhenmin, Li, Honglin, Li, Xin, Fan, Xueying, Jaramillo Fernández, Juliana, Pattelli, Lorenzo, Zhao, Jiupeng, Niu, Shichao, Li, Yao, and Xu, Hongbo

Abstract

In recent years, an increasing number of passive radiative cooling materials are proposed in the literature, with several examples relying on the use of silica (SiO2) due to its unique stability, non-toxicity, and availability. Nonetheless, due to its bulk phonon-polariton band, SiO2 presents a marked reflection peak within the atmospheric transparency window (8-13 µm), leading to an emissivity decrease that poses a challenge to fulfilling the criteria for sub-ambient passive radiative cooling. Thus, the latest developments in this field are devoted to the design of engineered SiO2 photonic structures, to increase the cooling potential of bulk SiO2 radiative coolers. This review seeks to identify the most effective photonic design and fabrication strategies for SiO2 radiative emitters by evaluating their cooling efficacy, as well as their scalability, providing an in-depth analysis of the fundamental principles, structural models, and results (both numerical and experimental) of various types of SiO2 radiative coolers., The authors thank the National Key Research and Development Program of China (2022YFB3902704), the National Natural Science Foundation of China (No.51702068, 52072096), the Natural Science Foundation of Heilongjang Province (LH2023E034) and the Fundamental Research Funds for the Central Universities (HIT OCEF. 2021004). L.P. and J.J.F. acknowledge support from the European project PaRaMetriC, code 21GRD03. The project 21GRD03 PaRaMetriC received funding from the European Partnership on Metrology, co-financed by the European Union’s Horizon Europe Research and Innovation Programme, and from the Participating States. Open Access Funding provided by Istituto Nazionale di Ricerca Metrologica within the CRUI-CARE Agreement., Peer Reviewed, Postprint (published version)

Published
2024

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