The density of dust in a tunnel during construction is one of the most important factors among the environmental conditions experienced by construction workers. Dust is caused by blasting, shotcrete, waste-handling, etc. Effectively controlling dust is very difficult, especially during blasting. Thus, an effectively designed ventilation system is needed in order to reduce the density of dust. The behavior of dust in a tunnel is only experimentally understood, but there remain many conditions which affect the efficiency of ventilation. If the behavior of dust in a tunnel could be better understood, ventilation systems would be more effectively designed.

View full abstract

Regulations controlling the quality of water discharged from reclaimed areas are becoming more and more strict for reclamation projects which use cutter suction dredgers. These regulations seek to prevent the damaging effects of spilled water on the coastline. For this reason, it is necessary to skillfully manage the growing estimates of water that is discharged along with fine soil particles. Reclamation projects which use cutter section dredgers dredge the sea bed, sucking up soil as well as water, and transport everything to the reclaimed area through a system of distribution pipes. These pipes are also connected to the project's outlet system for discharging water and fine soil particles. The conditions at reclaimed areas under construction change daily, and we must be able to precisely predict these changes. Although several methods have been proposed, one must be selected. This paperwill introduce the actual problems of density and the growing estimates of discharged water and fine soil particles.

View full abstract

For the past two decades, Water Jet Technology has been studied and developed in order to facilitate the mechanical and material improvement of high pressure pumps. In particular, for nearly ten years, the practical use of this technology has been widely expanded from civil engineering to medical tools. YBM has been developing and distributing mud pumps together with boring/drilling machines for mine drilling, ground water development and civil construction. The YBM high pressure triplex plunger pump (Jet Pump), developed according to accumulated technology, is utilized for jet cutter piling and jet grouting jobs in civil construction works, fracturing and water circulation works in the test of Hot Dry Rock (HDR) electric power generation systems, and the Oyster-shell Crushing and Tilling Systems used in fishery farms. Several example of Jet Pump utilization are introduced in this technical note.

View full abstract

In recent years, as people have become more and more health conscious, they have taken a greater interest in bathroom amenities. As a result, whirllpool baths have become increasingly popular, because consumers believe that whirlpool baths are effective for relieving fatigue. This report introduces TOTO's applied technique, which controls the jet stream mixed air (gas-liquid two-phase flow) according to somatic sensations, and in addition, submits subjects for further research.

View full abstract

The development of offshore oil and gas basins such as in the North Sea and the Gulf of Mexico is increasingly characterized by “marginal” reservoirs. The main challenge facing the oil industry is to economically develop these discoveries. One of the major technical trends in the development of such marginal reservoirs is the drive towards total subsea production. All reservoir fluids will be transporteduntreated to a central process facility or ultimately to shore. The development of “multiphase production systems”, either in flow-lines to a central platform or in pipelines to shore, is favored due to important cost reductions resulting from the minimization of field process facilities and pipeline costs. For such a production concept to be a practical proposition, a high level of confidence is required in the application of the multiphase flow technology to the transportation of untreated reservoir fluids over long distances. Multiphase pumping is one of three main aspects of multiphse flow technology that requires further development to make such concepts workable. The development of pumps to handle multiphase flow constituting the full range of flow patterns and with gas void fractions from 0 to 100% is progressing, and some prototype units are currently operational. Japan National Oil Corporation has started R & D in this area, bringing together its expertise, research laboratories and teams since 1990.

View full abstract

An important feature of small multitubes flow-through boilers is that they must be designed to be produced according to regulations such as a maximum working pressure of 1MPa and a maximum surface area of 10m². Within these regulations, more compact and effective boilers are being designed and developed. At present, a design which has achieved a maximum equivalent steam generating rate of 2ton/h and a relatively high heat flux has been developed for industrial use. These results have been achieved due to advances in heat transfer techniques. However, several problems remain to be solved in order to make the separator and upper header, which maintain the steam dryness fraction, more compact and effective. The problems for creating a two-phase flow vapor-liquid process in this boiler are mentioned.

View full abstract

The rate of slugs passing through a pipeline 410mm in diameter and 630m in length was gradually decreased from 552 slugs per hour at 80m to a 43% level of 240 per hour at 500m, with the novel dredged mud conveyance system using compressed air. The aim of this study was to clarify the mechanism of the decrease in the slug passage rate by establishing a slug flow deformation model. Previous studies of air-liquid two-phase flows have mainly focused on liquid of low viscosity in short pipelines of narrow diameter. The flow deformation phenomena of slugs in a pipeline such as the decrease with distance of slug passage rate have been neglected. However, in the large-diameter, long-distance pipeline used at a dredging site, the flow deformation phenomena must be considered, otherwise the conveyance efficiency might not be evaluated accurately. The slug flow deformation model has been established from the viewpoint of the flow deformation phenomena: generation, development and breakdown of slugs. Slugs of various length are generated due to the development of surface waves with various wavelengths. The generated slug develops until a critical point when a balance is reached between the kinematic energy and the energy loss from friction with the pipe wall and the slug's inner energy loss. The developed slug breaks down due to the friction and the inner energy loss. Finally, the critical development length is obtained in view of the energy loss due to the friction caused by viscosity and the energy loss due to the normal stress.

View full abstract

Horizontal annular flow was classified in detail into the following three flow configurations: the slug-like flow with frothy liquid lumps, disturbance wave and ripple flows. In this paper, it was shown that the kurtosis and skewness of the probability density function of time-varying hold-up depended on these flow configurations. However, successful results were not obtained for the pressure difference data. Relations between the kurtosis and volume flow quality are proposed for the criteria of boundaries between these flow configurations of annular flow.

View full abstract

Flow pattern and axial pressure loss are investigated experimentally for gas-liquid (air-water) two-phase flow when the flow passes through a rotating pipe. It is observed that as a result of the rotation bubbles are gathered toward the center of the rotating pipe while the liquid is pushed to the pipe wall covering a large area of the pipe wall. The pressure loss along the span of the rotating pipe decreases when the rotation speed is increased. A correlation for the two-phase friction multiplication factor derived from the experimental observations including the effect of the pipe rotation is proposed, estimating the experimental data reasonably within the range of this experiment.

View full abstract

[in Japanese]

View full abstract