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41.
We develop a hybrid unsteady-flow simulation technique combining direct numerical simulation (DNS) and particle tracking velocimetry
(PTV) and demonstrate its capabilities by investigating flows past an airfoil. We rectify instantaneous PTV velocity fields
in a least-squares sense so that they satisfy the equation of continuity, and feed them to the DNS by equating the computational
time step with the frame rate of the time-resolved PTV system. As a result, we can reconstruct unsteady velocity fields that
satisfy the governing equations based on experimental data, with the resolution comparable to numerical simulation. In addition,
unsteady pressure distribution can be solved simultaneously. In this study, particle velocities are acquired on a laser-light
sheet in a water tunnel, and unsteady flow fields are reconstructed with the hybrid algorithm solving the incompressible Navier–Stokes
equations in two dimensions. By performing the hybrid simulation, we investigate nominally two-dimensional flows past the
NACA0012 airfoil at low Reynolds numbers. In part 1, we introduce the algorithm of the proposed technique and discuss the
characteristics of hybrid velocity fields. In particular, we focus on a vortex shedding phenomenon under a deep stall condition
(α = 15°) at Reynolds numbers of Re = 1000 and 1300, and compare the hybrid velocity fields with those computed with two-dimensional DNS. In part 2, the extension
to higher Reynolds numbers is considered. The accuracy of the hybrid simulation is evaluated by comparing with independent
experimental results at various angles of attack and Reynolds numbers up to Re = 104. The capabilities of the hybrid simulation are also compared with two-dimensional unsteady Reynolds-Averaged Navier–Stokes
(URANS) solutions in part 2. In the first part of these twin papers, we demonstrate that the hybrid velocity field approaches
the PTV velocity field over time. We find that intensive alternate vortex shedding past the airfoil, which is predicted by
the two-dimensional DNS, is substantially suppressed in the hybrid simulation and the resultant flow field is similar to the
PTV velocity field, which is projection of the three-dimensional velocity field on the streamwise plane. We attempt to identify
the motion that originates three-dimensional flow patterns by highlighting the deviation of the PTV velocity field from the
two-dimensional governing equations at each snapshot. The results indicate that the intensive spots of the deviation appear
in the regions in which three-dimensional instabilities are induced in the shear layer separated from the pressure side. 相似文献
42.
In the present paper, the algorithm of Binary Image Cross-Correlation (BICC) was developed to measure the unsteady flow field.
A vortex flow field was used to test the algorithm by numerical simulation. The results show that BICC is an effective algorithm
for particle identification from consecutive images, the accurate velocity vector field can be obtained. The real velocity
field in a valve chamber was measured by BICC in this study. From the full-field velocity information, the pressure and vorticity
fields were also extracted by post-processing.
The project supported by the National Natural Science Foundation of China 相似文献
43.
Syun-ichi KiyookaHiroshi Fujimoto Masaaki MishimaShinjiro Kobayashi Khabir Md UddinMizue Fujio 《Tetrahedron letters》2003,44(5):927-930
Diphenylboron perchlorate very smoothly catalyzed self- and cross-condensation reactions of aldehydes at rt in nitroethane. The new catalyst provided novel behaviors owing to the characteristics of possessing a covalency in the boronoxygen bond, compared with ionic perchlorates. 相似文献
44.
采用柱层析等步骤纯化了根霉G7的羧甲基纤维素酶及β-葡糖苷酶,回收率分别为4.5%和19.6%.二种酶的最适酶反应温度都为55°C,并都能在较大pH范围内保持稳定,其中羧甲基纤维素酶具有很高的耐热性,在100°C水浴中保持1h也仍可检测出约20%的酶活性,最适反应pH为7.0~7.5;而β-葡糖苷酶的热稳性较差,其最适反应pH为5.0.该两种酶的分子量分别为2.5×104和9.5×104,而Km值则分别为7.40mgmL-1和0.213mgmL-1. 相似文献
45.
Mizue Fujio Toshikazu Adachi Yoshifumi Shibuya Akihisa Murata Yuho Tsuno 《Tetrahedron letters》1984,25(40):4557-4560
Substituent effects of p-MeO and p-MeS groups deactivated by additional m-substituents in cumyl and α-phenylethyl solvolyses were studied to provide evidence for the higher resonance demand in the α-phenylethyl system. 相似文献
46.
47.
Toshikazu Nishide Fujio Mizukami Hidenobu Yamaguchi 《Journal of Sol-Gel Science and Technology》1994,1(2):113-121
Many types of TiO2-SiO2 (Ti:Si=50:50 mol%) were prepared by the sol-gel procedure with and without 2-methyl-2, 4-pentanediol (MPD) as an organic ligand. The effect of MPD on the gel structure and the properties of the TiO2 crystals were studied by XRD and raman spectroscopy, and the effect of the sol standing time on the properties of the TiO2 crystals were also studied by XRD spectroscopy. In the gels with MPD, anatase of TiO2 appeared at approximately 580°C, and the crystal structures were similar despite the difference in the gel preparation procedure. The titania gels with MPD were presumed to be dispersed in the silica gel matrix without any Ti-O-Si bond. In the presence of MPD, the formation of titania gels is controlled and the specified TiO2 crystal is produced. 相似文献
48.
Tanaka M Imai M Fujio M Sakamoto E Takahashi M Eto-Kato Y Wu XM Funakoshi K Sakai K Suemune H 《The Journal of organic chemistry》2000,65(18):5806-5816
Asymmetric cyclization of symmetrical 3,4-disubstituted and 3,3, 4-trisubstituted 4-pentenals was studied using Rh-complexes with chiral ligands. The cyclization of symmetrical 4-pentenals 4a,b by a neutral Rh[(R)-BINAP]Cl afforded cis-3,4-disubstituted (4R)-cyclopentanones 9a,b of >95% ee in 25-31% yields; on the other hand, the cyclization of 4a-c by a cationic Rh[(R)-BINAP]ClO(4) afforded trans-3,4-disubstituted (4S)-cyclopentanones 10a-c of >95% ee in 70-81% yields. All stereoisomers could be stereoselectively made by the selection of a neutral or cationic Rh-complex, and (R)- or (S)-BINAP ligand. The Rh-catalyzed cyclization could be applied to the construction of cyclopentanones 17 and 18 bearing a chiral quaternary carbon. The cyclization by the cationic Rh[(R)-BINAP]ClO(4) afforded the optically active trans-3,3, 4-trisubstituted cyclopentanones 18a-c of 92-95% ee in 75-83% yields. The catalytic cycle was also studied by using deuterium aldehyde, and the tentative mechanisms of the enantio- and diastereoselection were proposed. 相似文献
49.
Fujio Okino Yukio Kawaguchi Kunitake Momota Toshihiro Ando Mamoru Yoshimoto 《Journal of fluorine chemistry》2004,125(11):1715-1722
Boron-doped semiconducting diamond films were prepared using BF3 by microwave plasma assisted chemical vapor deposition. B-doping was confirmed by SIMS and Raman spectroscopic measurements and the B-doping levels were estimated. Electrochemical behaviors of boron-doped diamond thin-film electrodes prepared using B2H6 and BF3 were studied by measuring cyclic voltammograms for anodic oxidation of 1,4-difluorobenzene in the liquid electrolyte, neat Et4NF·4HF. The results of the direct thermal interaction of elemental fluorine with hydrogenated and oxidized diamond surfaces are also presented. 相似文献
50.
Keikichi Uno Kazuma Niume Yasuhisa Iwata Fujio Toda Yoshio Iwakura 《Journal of polymer science. Part A, Polymer chemistry》1977,15(6):1309-1318
2-Sulfoterephthalic acid (STA) and disulfoisophthalic acid (DSIA) were synthesized through the sulfonation and the oxidation of m- and p-xylene. The polycondensation reactions of STA and DSIA with aromatic tetraamines gave polybenzimidazoles which contained one or two sulfonic acid groups for each repeating unit. The polymer obtained was soluble in sulfuric acid, some organic solvents, and aqueous strong alkaline solution. The polymers were stable up to 400°C, but they gave polybenzimidazoles above 400°C by eliminating sulfonic acid groups, instead of ring closure. 相似文献