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Designing and experimental study of compact vibration isolator with quasi-zero stiffness
Anvar Valeev,Radmir Tashbulatov,Boris Mastobaev 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.79 No.4
This study aimed to develop a compact high-efficiency vibration isolator. It was proposed to use force characteristic with quasi-zero stiffness. To avoid a number of design problems, the isolator was designed in a dome shape. This study features a mathematical model of the vibration isolator with quasi-zero stiffness. It allows calculating the isolator properties by geometrical parameters. Stability analysis giving advanced formulas for achieving the maximum workload at certain dimensions was made. For an experimental study, the prototypes were made of shock-absorbing rubbers IRP1346, IRP1347, IRP1348, and fluoroelastomer SKF-32. Force characteristic in static condition was studied, which showed the high efficiency of the compact vibration isolator with quasi-zero stiffness: natural frequency equals 0.8-1.2 Hz. An experimental study in dynamic condition was done using load cell sensors to measure dynamic force transmitted with and without the vibration isolator. The experiment shows a vibration isolation coefficient equal to 244, corresponding to the natural vibration frequency of 2.17 Hz. The study shows the vibration isolator with quasi-zero stiffness as highly efficient, compact, and very perspective for industrial application.
A low-Reynolds-number k–ε model for polymer drag-reduction prediction in turbulent pipe flow
Chen Yang,Zhang Meiyu,Valeev A. R.,Li Changjun,Nechval A. M.,Yang Peng 한국유변학회 2024 Korea-Australia rheology journal Vol.36 No.2
Pipeline transport at high Reynolds number can result in significant turbulent losses. One of the most effective methods for turbulent drag reduction is adding a very small amount of polymer drag-reducing agent to the pipeline. However, due to the complex interaction between polymers and turbulence, turbulence models incorporating polymer additives remain to be studied and developed. In the present work, we investigated the turbulence model using Reynolds averaged numerical simulation (RANS) to describe polyacrylamide drag reduction flow. A low-Reynolds-number k–ε model in turbulent flow has been developed by considering the concentration and type of polymers, which can be applied for polymer drag reduction prediction in the pipe. Mean velocity profile Uf, turbulent intensity, turbulent kinetic energy k, and turbulent dissipation rate ε in the regions of viscous sublayer, buffer layer and logarithmic layer have been predicted with various concentration θ, Reynolds number Re, degradation degrees, and changing laws of these factors have been revealed with wall distance. The developed turbulence model showed a good capability to qualitatively forecast mean velocity profile, turbulent intensity, turbulent kinetic energy, and turbulent dissipation rate, and the prediction error between the experimental and simulated values falls along the y = x curve, which can be used for the investigation and prediction of varies water-soluble, oil-soluble polymers in turbulent drag reduction flow in pipes with other parameters such as pipe diameter, pipe length, and the Reynolds number.
Magnetic field and radial velocities of the star Chi Draconis A
Lee, Byeong-Cheol,Gadelshin, D,Han, Inwoo,Kang, Dong-Il,Kim, Kang-Min,Valyavin, G,Galazutdinov, G,Jeong, Gwanghui,Beskrovnaya, N,Burlakova, T,Grauzhanina, A,Ikhsanov, N R,Kholtygin, A F,Valeev, A,Bych Oxford University Press 2018 Monthly notices of the Royal Astronomical Society. Vol.473 No.1