Measurements in a heated turbulent wall jet on a concave wall     

S. Okamoto  M. M. Gibson 《Mineralium Deposita》1994,29(1):291-297

The paper contains the results of extensive single-point hot-wire and resistance-thermometer measurements in a wall jet on a heated concave wall with an external free stream. It is found that the turbulence in the inner (wall) and outer layers is sensitive to the distortion produced by the curved wall, broadly confirming current views of these effects. The effect on the turbulence of streamline curvature is stabilising in the outer layer, destabilising in the inner. Consequently the point of zero shear stress is closer to the point of maximum mean velocity than in flat and convex wall jets with which these new results are compared. The rate of growth is about 80% of that of the equivalent flat wall flow, and about half that of the convex wall flow. Changes in the wall shear stress and heat flux, which are increased relative to the flat wall flow, are significant but less than the changes in the corresponding convex wall flow. The greatest changes occur in the triple products.List of Symbols c _f skin friction coefficient, 2 _w / U _M ² - q ² u ² +v ²+w ² - R radius of curvature of wall - r radius of curvature - St Stanton number,-q _w /c _p U _M (T –T _w ) - T mean temperature - U streamwise mean velocity - U _J initial wall-jet velocity - U ₁ initial free-stream velocity - U ₀ U _M –U _PW - u, v, w fluctuating velocity components - x, y distances measured along and normal to the wall - y _0.5,y _M wall-jet thicknesses defined in the text - y _S ,y _T wall-jet thicknesses defined in the text - T T _W –T - shear-layer thickness - ₂ momentum thickness - temperature fluctuation - M point of maximum velocity - P potential flow - s point of zero shear stress - W wall value - free stream value  相似文献   

CCD surface photometry of an outburst of P/Schwassmann-Wachmann 1 comet     

Tsuko Nakamura  Jun-Ichi Watanabe  Hajime Kawakami 《Earth, Moon, and Planets》1991,52(1):15-25

We have observed an outburst of P/Schwassmann-Wachmann 1 (SW1) on 25–26 July 1987 using a CCD imager with R-band filter. The total brightness increased from 15.5 mg (25d) to 14.4 mag (26d) during tabout 24 hrs. The southward elongated coma of 25 was detected. The radial surface brightness (B) profiles are plotted against apparent distance p from the nucleus. The logarithmic derivative k = d ln B/d ln p for the inner coma is found to have steepened from k = –1.40 (25d) to k = –1.69 (26d), whereas that for the outer coma showed no appreciable change (k = –1.19 ~ –1.22). The ellipticity of the isophotal contour of the inner coma increased about 15% fro 25d to 6d. It is concluded that the scale of this outburst was smaller than the typical ones whose magnitude change is 5–8 mag. From recent findings on the outburst natur eof SW1 including ours, a working model of the nuclues is proposed.  相似文献   

Displacement properties of landslide masses at the initiation of failure in quick clay deposits and the effects of meteorological and hydrological factors     

Takashi Okamoto  Jan Otto Larsen  Sumio Matsuura  Shiho Asano  Yoshitsugu Takeuchi  Lars Grande 《Engineering Geology》2004,72(3-4):233-251

This study aimed to identify displacement properties of landslide masses at the initiation of failure and factors that affect the landslides activities in areas where quick clay is found. We set up a research site in a quick clay deposit area in Norway and monitored the displacements of landslide masses and meteorological and hydrological factors for a long period of time using an automatic monitoring system. The system collected data for two landslides that occurred at the site from the start of their movement until their ultimate collapse.

The two landslides that were monitored showed definite secondary and tertiary creep stages before they collapsed. One of the landslides moved from the secondary stage to the tertiary creep stage when another landslide occurred nearby. The tertiary stage of this landslide showed reconstruction of short primary, secondary, and tertiary creep stages. These phenomena suggested that (1) the stress at the end of the landslide mass was released during the nearby landslide, and (2) a new stress distribution was formed in the landslide mass. The critical strain differed for 14 times between the two landslide masses we monitored. The difference was likely attributable to the difference in the contents of quick clay, which shows small critical stress against slope failure, as well as topological factors.

Our analyses of the effects of hydrological and meteorological factors on landslides showed that the precipitation of 3 and 10 days before six slope failures as the final stages of the landslides that had occurred in the research area was no different from the mean precipitation of periods that showed no slope failure, suggesting that precipitation had no direct effects on the collapse of the landslide masses. On the other hand, the traveling velocities of the landslide masses during the secondary creep stage, which was prior to their collapse, were affected by the water content of the soil and precipitation (and the amount of snowmelt water), but was little correlated with the pore-water pressure of the quick clay layer. We also found that the presence of snow cover scarcely affected landslide movements.  相似文献   

Structure of the Jan Mayen microcontinent and implications for its evolution     

Shuichi Kodaira  Rolf Mjelde  Karl Gunnarsson  Hajime Shiobara  & Hideki Shimamura 《Geophysical Journal International》1998,132(2):383-400

  相似文献   

Editorial     

Briad Ridley  Dieter Ehhalt  Hajime Akimoto 《Journal of Atmospheric Chemistry》2001,38(1):1-1

  相似文献   

On sexual dimorphism in Paleoparadoxia tabatai     

Yoshikazu  Hasegawa Yojiro  Taketani Hajime  Taru Osamu  Sakamoto Makoto  Manabe 《Island Arc》1994,3(4):513-521

Abstract Upon studying the well preserved skulls referred to Paleoparadoxia tabatai from Japan, the short and low skull of the Yanagawa specimen requires an explanation. Six cranial and dental characters lead us to suggest that the Yanagawa individual is a female while the Izumi, Ohnohara, and Itsukaichi skulls are male. The important characters in the Yanagawa skull are its shortness and shallow depth, less pronounced sagittal and nuchal crests, smaller zygoma, and the small dentition with especially poorly erupted canines, most of which are indicative of weak masticatory musculature.  相似文献   

Teleseismic synthetics obtained from 3-D calculations in 2-D media     

Taro Okamoto 《Geophysical Journal International》1994,118(3):613-622

  相似文献   

Mixed layer in the Sea of Japan: numerical simulation and long-term data analysis   总被引：1，自引：1，他引：0  

TRUSENKOVA Olg  KHRAPCHENKOV Fyodor  ISHIDA Hajime 《海洋学报(英文版)》2005,24(1):76-85

Seasonal variation and topography of the mixed layer in the Sea of Japan are studied by comparison of results from long-term observation data analysis and from numerical simulation with the MHI oceanic model (Shapiro. 1998. Marine Hydrophysical Journal, 6:26～40). The data are retrieved from Oceanographic Atlas of the Bering Sea, Okhotsk Sea, and Japan/East Sea (Rostov, Rostov, Dmitrieva, et al. 2003. Pacific Oceanography, 1 (1):70-72). The simulated and long-term patterns are compared. An impact of surface buoyancy flux, wind, and convergence/divergence of surface currents upon the mixed layer in the Sea of Japan is analyzed.  相似文献   

Petrology of the diamond-grade eclogite in the Kokchetav Massif, northern Kazakhstan   总被引：2，自引：0，他引：2  

K. Okamoto  J. G. Liou and  Y. Ogasawara 《Island Arc》2000,9(3):379-399

Abstract The Kokchetav Massif of northern Kazakhstan is unique because of the abundant occurrence of microdiamond inclusions in garnet, zircon and clinopyroxene of metasediments. In order to determine precise pressure–temperature (P–T) conditions, we have systematically investigated mineral inclusions and the compositions of major silicates in Ti–clinohumite–garnet peridotite and diamond-grade eclogite from Kumdy–Kol. It was found that garnet peridotites from Kumdy–Kol contain assemblages of garnet, olivine, Ti–clinohumite and ilmenite. The garnet contains inclusions that are indicative of both ultrahigh pressure (UHP) and retrograde conditions. Inclusions of hydrous phases such as chlorite, amphibole and zoisite were formed at the post-UHP stage. The study also found that eclogite from Kumdy–Kol contains albite–augite symplectites after omphacitic pyroxene. The core of pyroxene (sodic augite) contains high K₂O (up to 1wt%; average 0.24wt%). Phengite is included in the core. Applying the K₂O-in-augite geobarometry, which is based on recent experiments, and the garnet–clinopyroxene (Grt–Cpx) geothermometer for peak metamorphism, the eclogites yield P–T estimates of > 6 GPa and > 1000 °C, and the diamond-grade eclogites yield lower temperature estimates at 900–1000 °C and 5 GPa.  相似文献   

Experiment and simulation of turbulent flow in local scour around a spur dyke   总被引：6，自引：2，他引：4  

Hajime NAKAGAWA  Kenji KAWAIKE  Yasuyuki BABA 《国际泥沙研究》2009,24(1):33-45

The turbulent flow in the local scour hole around a single non-submerged spur dyke is investigated with both experimental and numerical methods. The experiments are conducted under clear-water scour regime with an impermeable spur dyke. The scour geometry and flow velocities are measured in details with a high-resolution laser displacement meter, electro-magnetic velocimetries and PIV （Particle image velocimetry）. A 3D non-linear k-ε model is developed to simulate the complex local flow field around the scour area. The numerical model is formulated using FVM （Finite volume method） on a collocated unstructured mesh, capable of resolving complex geometries and boundaries. It is found that the simulation results are reasonably consistent with those of the experimental measurements. Based on the study results, the nature of the flow structure around a spur dyke with local scour hole is analyzed.  相似文献