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Strategy to Develop Efficient Grid System for Flow Analysis Around Two-dimensional Bluff Bodies
M. N. Haque,H. Katsuchi,H. Yamada,M. Nishio 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.5
Computational Fluid Dynamics (CFD) is becoming more and more popular in various fields of engineering due to improvement of turbulence model and availability of high performance computing system. In bluff body and bridge aerodynamics fields CFD is applied to predict the aerodynamic response for reconfirming experimental results and revealing the flow mechanism. Accurate prediction of response largely depends on the accurate generation of grid system having converged solution. However, conventional grid convergence test takes much time to obtain the desired grid system. It becomes even worse for a beginner or user having lack of experience. In this paper, a strategy was proposed and demonstrated for faster generation of accurate and converged grid system for two-dimensional bluff bodies. First, the strategy was proposed and demonstrated by conducting simulation for a square rectangular cylinder at Reynolds number (ReB) of 1.22 × 104. An equation was derived to initialize the first grid height (y) and a Growth Factor (GF) was recommended to expand the grid away from the target body to obtain a grid system having converged solution. The strategy was checked and examined by conducting standard grid convergence test and by comparing solution of various aerodynamic parameters with past experimental works. Finally, the strategy was applied for an elongated rectangular cylinder and for a streamlined bridge deck for further checking the performance of the strategy and found to be efficient enough for faster and quick generation of accurate and converged grid system.
Red Blood Cell Velocity Field in Rat Mesenteric Arterioles Using Micro PIV Technique
Sugii, Y,Nishio, S,Okamoto, K,Nakano, A,Minamiyama, M,Niimi, H Biomedical Engineering Society for Circulation 2003 International Journal of Vascular Biomedical Engin Vol.1 No.1
As endothelial cells are subject to flow shear stress, it is important to determine the detailed velocity distribution in microvessels in the study of mechanical interactions between blood and endothelium. This paper describes a velocity field of the arteriole in the rat mesentery using an intravital microscope and high-speed digital video system obtained by a highly accurate PIV technique. Red blood cells (RBCs) velocity distributions with spatial resolutions of $0.8{\times}0.8{\mu}m$ were obtained even near the wall in the center plane of the arteriole. By making ensemble-averaged time-series of velocity distributions, velocity profiles over different cross-sections were calculated for comparison. The shear rate at the vascular wall also evaluated on the basis of the ensemble-averaged profiles. It was shown that the velocity profiles were blunt in the center region of the vessel cross-section while they were steep in the near wall region. The wall shear rates were significantly small, compared with those estimated from the Poiseuille profiles.
Microfabrication of ZnO on a PTFE Template Patterned by Using Synchrotron Radiation
Q. X. Guo,Y. Mitsuishi,T. Tanaka,M. Nishio,H. Ogawa,Y. Z. Huang 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5
Microstructures of ZnO were fabricated on polytetrafluoroethylene, which had been patterned by synchrotron radiation light irradiation, by using metal organic decomposition. Near-band-edge emission without any deep-level emissions was observed at 3.2 eV from the ZnO microstructures. The results show that the process is promising for obtaining micro- and nanostructured ZnO with a high aspect ratio and a high resolution.