Non-Diaphragm Shock Tube and Shock Waves in Low Temperature Gases (First report)

In the present paper an experimental approach for shock waves and shock-condensation phenomena in low temperature gases (N₂ and R-12) within the limit of -45℃ is performed by means of new facilities developed by combining the non-diaphragm (snap-action) shock tube with cooling by liquid nitrogen. Together with the measurements for temperature, incident and reflected velocities of the wave, and pressure history, the experiment of flow visualization is conducted, which shows wall condensation phenomenon of R-12 behind the reflected shock wave

Improvement of the Vibration Prediction of a Poppet Valve in a Cavitation State

Poppet valves are popular components of hydraulic systems, but they sometimes induce vibration in these systems. In particular, the vibration phenomenon of a poppet valve in a cavitation state is a troublesome problem in hydraulic systems, because the dynamic effects of cavitation on the poppet valve are difficult to predict. In this research, we investigated the vibration phenomenon of the poppet valve in the cavitation state in a visualization experiment and numerical simulation. We found in numerical simulation that it is possible to predict the tendency of the vibration by assuming that the bulk modulus of hydraulic oil is affected by the ratio of cavitation bubbles mixed in the oil. Additionally, we proposed a simple method of estimating the quantity of cavitation bubbles through visualization experiments and image processing. We then improved the prediction accuracy of the poppet valve behavior by applying the bubble mixing ratio obtained using the method in the numerical simulation model. The described methods not only avoid the sensor effect on the flow field but also save the additional measurement cost, and they are easy to apply to hydraulics systems

High Reynolds Number Flow in Capillary Tube with Spiral/Bend Portion (Experimental Results for Water)

Experimental study on water flow in capillary tubes with straight, bent, or coiled portion is conducted. Stainless tubes with nominal diameter of 0.5mm, 0.25mm, and 0.1mm are examined at several temperatures. Reynolds number ranges from 30 to 16000, where maximum velocity becomes up to 30m/s. Pressure loss of test piece and discharge flow rate are measured to be compared with the results from previous studies. In spite of considerable roughness of capillary inner surface, measured data do not indicate roughness effect explicitly. Laminar friction factors for coiled tubes show the clear dependence on the number of turns in the coil, which cannot be explained by previous studies. Empirical equations for examined capillary contours are obtained

QUANTITATIVE MEASUREMENT OF TEMPERATURE GRADIENT IN NATURAL HEAT CONVECTION USING COLOR-STRIPE BACKGROUND ORIENTED SCHLIEREN (CSBOS) TECHNIQUE AND COMPUTED TOMOGRAPHY (CT) METHOD

ABSTRACT Quantitative image analysis and measurement of flow fields in convective heat transfer has great importance for the optimum energy consumption problems. In natural and forced convection phenomena of fluids, the complexity of flow field prevents us from detailed three dimensional (3D) experimental analyses of steady/unsteady dynamics in fluids. These flow fields have locally different density and temperature values and yet to be observed quantitatively. Recent development of the Particle Image Velocimetry (PIV) and Particle Tracking Velocimetry (PTV) techniques lead us to the quantitative investigation of flow fields in experimental researches. On the other hand, in image measurements density and temperature distributions have been grasped only in two-dimensions (2D). These qualitative image analyses of flow fields were obtained by using classical flow visualizing techniques, such as shadowgraph and color schlieren method. This paper describes the quantitative measurement of convective flow field using our originally proposed color striped background oriented schlieren (CSBOS) method. The obtained measured image data is used for CT reconstruction and 3D temperature gradient distributions

Construction of microscopic model for f-electron systems on the basis of j-j coupling scheme

We construct a microscopic model for f-electron systems, composed of f-electron hopping, Coulomb interaction, and crystalline electric field (CEF) terms. In order to clarify the meaning of one f-electron state, here the j-j coupling scheme is considered, since the spin-orbit interaction is generally large in f-electron systems. Thus, the f-electron state at each site is labelled by $\mu$, namely, the z-component of total angular momentum j. By paying due attention to f-orbital symmetry, the hopping amplitudes between f-electron states are expressed using Slater's integrals. The Coulomb interaction terms among the $\mu$-states are written by Slater-Condon or Racah parameters. Finally, the CEF terms are obtained from the table of Hutchings. The constructed Hamiltonian is regarded as an orbital degenerate Hubbard model, since it includes two pseudo-spin and three pseudo-orbital degrees of freedom. For practical purposes, it is further simplified into a couple of two-orbital models by discarding one of the three orbitals. One of those simplified models is here analyzed using the exact diagonalization method to clarify ground-state properties by evaluating several kinds of correlation functions. Especially, the superconducting pair correlation function in orbital degenerate systems is carefully calculated based on the concept of off-diagonal long-range order. We attempt to discuss a possible relation of the present results with experimental observations for recently discovered heavy fermion superconductors CeMIn$_5$ (M=Ir, Co, and Rh), and a comprehensive scenario to understand superconducting and antiferromagnetic tendencies in the so-called ``115'' materials such as CeMIn$_5$, UMGa$_5$, and PuCoGa$_5$ from the microscopic viewpoint.Comment: 16 pages, Revtex, with 6 figures embedded in the text. Submitted to Phys. Rev.

Hatching Patterns of the Monogenean Parasites Benedenia seriolae and Heteraxine heterocerca from the Skin and Gills, Respectively, of the Same Host Fish, Seriola quinqueradiata(COMMUNICATION)(Developmental Biology)

Volume: 9Start Page: 451End Page: 45