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Analysis of dynamic characteristics of a sealed ends squeeze film damper considering the fluid inertia force

Zhou Hai Lun, Cang Yang Guang, Zhang Yu Qi, Guo Chao

Journal of Theoretical and Applied Mechanics

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2023

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Vol. 61 nr 3

441--452

EN

In order to effectively calculate dynamic characteristics of a sealed ends squeeze film damper (SFD) under the influence of the inertial force, a computational fluid dynamics model of the sealed ends SFD is established. The fluid inertia coefficient of SFD is investigated by using an energy approximation method. Both the theoretical calculation and numerical simulation are conducted to analyze the effects of eccentricity ratio and whirling frequency on stiffness and damping. In this research, the oil film inertia force of the sealed ends SFD is solved by using long bearing approximation (LBA) theory, which provides guidance for the design and application of the sealed ends SFD.

2

A study on RCFST column instability modes

Lu Zhengran, Guo Chao

Archives of Civil Engineering

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2022

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Vol. 68, nr 2

211--225

EN

In this work, the instability damage modes of yield state of a steel tube at the tension side of a rectangular steel tube-confined concrete (RCFST) column under eccentric compression were classified into two types based on the coupling effect of slenderness ratio (λ) and eccentricity ratio (γ). The two types include the unilateral compression yield failure mode with a smaller value of γ and tensile and compressive yield failure modes on both column sides with a larger value of γ. Further, the parametric analyses were performed by employing the finite element (FE) method and the analytical analysis to test 16 groups of RCFST columns by varying the γ value with different λ values. It was observed that the results of the analysis for the mechanical properties like the responses of load-strain (Ρ-ε) and RCFST column instability modes correlated well with the results obtained in the experiments. Furthermore, the proposed theoretical method could be used to investigate the roles of γ as a controller against the instability in RCFST columns when compared with λ.

3

Study of a new type of Flettner rotor in merchant ships

Li Boyang, Zhang Rui, Li Yajing, Zhang Baoshou, Guo Chao

Polish Maritime Research

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2021

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nr 1

28--41

EN

Wind energy is a clean and renewable source of energy. This study seeks to explore the potential for utilising wind power for merchant ships. A new type of Flettner rotor (rotating cylinder) mounted on the superstructure of a ship is proposed and numerically simulated. The construction and installation of the rotating cylinder is designed and a numerical simulation of the ship-mounted cylinder is carried out, using the commercially available CFD code Ansys Fluent to obtain parameters such as lift and drag coefficient of the cylinder in different conditions. Specifically, it is found that the cylinder type superstructure can play a certain role in reducing the effect of friction by comparing traditional and cylindrical superstructures; the rotating cylinder can generate auxiliary thrust for the ship. After analysis, the wind speed around the cylinder and spin ratio will have a direct influence on its thrust effect; there is an inflection point in the lift coefficient with the increase of α; the thrust coefficient (8.63) reaches the maximum environmental wind speed at 10 m/s and spin ratio is 2.5. For the rotating cylinder, the greater the environmental wind, the greater the thrust contribution generated under the same spin ratio conditions. The maximum thrust can reach 750,000 N; the cylinder’s auxiliary propulsion contribution shows a better advantage in α = 2.0. The effective power generated by the cylinder reaches a maximum of 2,240 kW for environmental wind speed = 20 m/s and α = 1.0.