Transactions of the Japan Society of Mechanical Engineers. B 

About: Transactions of the Japan Society of Mechanical Engineers. B is an academic journal. The journal publishes majorly in the area(s): Turbulence & Heat transfer. It has an ISSN identifier of 0387-5016. It is also open access. Over the lifetime, 7875 publications have been published receiving 20362 citations.

Structure of a Turbulent Separation Bubble

Abstract: Flow in the separation bubble formed along the sides of a blunt flat plate with right-angled corners has been studied in terms of extensive single- and two-point measurements of velocity and surface-pressure fluctuations. The cross-correlations between the surface-pressure and velocity fluctuations are found to be useful for the study of large-scale vortex structure in the bubble. Large-scale vortices are shed downstream from the separation bubble with a frequency of about 0.6U∞/xR, where U∞ is the approaching velocity and xR is the time-mean length of the bubble. On top of this regular vortex shedding, there exists a large-scale unsteadiness in the bubble. Vortices which are much larger than the regular vortices are shed with frequencies less than about 0.2U∞/xR. The large-scale unsteadiness is accompanied by enlargement and shrinkage of the bubble and also by a flapping motion of the shear layer near the separation line. The intermittent nature of the flow in the bubble is clarified in some detail. The distributions of the cross-correlations between the pressure and velocity fluctuations demonstrate the vortex structure in the reattaching zone. The longitudinal distance between the vortices is estimated to be (0.7–0.8) xR and their convection velocity is about 0.5U∞ near the reattachment line. The cross-correlations also suggest the existence of a longitudinal counter-rotating system in the bubble. The distance between the axes of the rotation is of the order of 0.6xR. Variations of timescales, lengthscales and phase velocities of the vortices are presented and discussed.

Flow patterns and pressure drop in isothermal gas-liquid concurrent flow in a horizontal capillary tube.

Abstract: A gas-liquid two-phase flow in a capillary tube or a narrow passage is encountered in many applications, for example, the flow of coolant in evaporators of many kinds of heat exchangers. Sufficlent information on fundamental parameters, such as void fraction and pressure drop, however, are not available in designing such devices. In the present investigation, we made a detailed observation of the flow pattern of an air-water two-phase flow in a horizontal capillary tube with an inner diameter of 1.0mm to 4.9mm, and attempted to correlate and explain the behavior of the pressure drop changing with the flow rates of both phases by introducing a physical model.

A Study on the Application of the Two–Color Method to the Measurement of Flame Temperature and Soot Concentration in Diesel Engines

Abstract: Results are presented of optical measurement of the flame temperature and KL factor (soot concentration) in a direct injection diesel engine using the two-color method. In the latter stages of combustion, the infrared two-color method gave a lower value than the visible two-color method, the difference being enhanced with crank angle advancement. The KL factor value obtained by the visible method was about half that of the infrared method. These differences were caused by the alpha index (wavelength dependency of flame emissivity) change in the infrared region during the combustion period; the effect at both wave lengths of uneven distributions of temperature and soot concentration along the optical path; and the effect of the reflection of the opposite wall on the infrared method. The optical characteristics and other instrumentation problems of the two-color method at both wavelengths are also discussed.