Shinichi Tsuda

Molecular Dynamics Study of Heterogeneous Bubble Nucleation in Liquid Oxygen Including Helium, Nitrogen, or Argon

Heterogeneous bubble nucleation in liquid oxygen including helium, nitrogen, or argon is simulated by using the molecular dynamics method. Molecular interaction is given as Lennard-Jones potential, and, basically, each potential parameter is determined so that a saturation curve obtained by MD data is consistent with an experimental value. In the case that helium is the impurity, a bubble is caused by density fluctuation at a lower concentration, while clusters of helium molecules become bubble nuclei at a higher concentration, and the point of bubble formation moves closer to the saturation point of pure oxygen when they form clusters. In the case that nitrogen or argon is the impurity, the above-mentioned clustering is not observed at a concentration where helium makes clusters, and these impurities have weaker action to make clusters compared with helium.© 2002 ASME

A Modeling of Thermal Properties of Hydrogen/Oxygen System Using Molecular Simulations

We have calculated some thermal properties of hydrogen and of oxygen using a classical molecular dynamics (MD) method. To examine the applicability of a simplified intermolecular interaction model, we employed the Lennard-Jones (12-6) potential with ignoring the rotational freedom in both fluids and conducted MD simulations for the Lennard-Jones fluid at a wide density-temperature range. Using the MD calculation data, we made a polynomial function of Helmholtz free energy, which can derive every thermal property, and determined the potential parameters of the Lennard-Jones model which reproduce the thermal properties of hydrogen and of oxygen. In spite of the very simple intermolecular interaction model, we found that it can reproduce the thermodynamic properties of oxygen at a wide density-temperature range and the pressure-volumetemperature relationship of hydrogen below its critical density. Such simple model has a potential to estimate reasonably an equation of state of hydrogen/oxygen mixture or the interfacial tension which is very important in the analyses of the coaxial injection jet flows of oxidizer with gaseous hydrogen in a rocket engine thrust chamber.

An improvement of a cavitation model and the application to LES

In this paper, we have improved a cavitation model implemented in “Front Flow/Blue (FFB)”, which is a solver of turbulent flows using the large-eddy simulation (LES) technique with high accuracy. To improve the cavitation model, we have carried out a survey of conventional cavitation models and performed a trade-off between the models based on some evaluation points such as accuracy, achievement, future potential, and computational cost. In the new cavitation model, the surface area of cavitation bubbles in each cell is also solved in addition to the volume fraction of the bubbles. Although the validation is in progress, the new cavitation model is expected to be useful to reproduce a detailed cavitation structure.Copyright

Nucleation and Growth of Bubble With the Effects of Solute Gas

Bubble nucleation and growth of formed nuclei are investigated by molecular dynamics simulation in Lennard-Jones liquid with gas impurities. For the onset of nucleation from bulk, it has been found that a dissolved gas whose interaction is very weak and whose diameter is larger than that of solvent molecules makes the action to cause composition fluctuation or local phase separation so strong that the nucleation probability predicted from pressure change becomes qualitatively wrong. It has been confirmed that this wrong prediction is generally explained by introducing the superheat ratio nondimensionalized by saturation pressure and spinodal pressure. For the growth stage of formed bubble nuclei, it is observed that the coalescence of nuclei occurs when a weak-interaction gas is dissolved at a high concentration while the competition between neighbor nuclei is dominant in the case of pure liquid.Copyright

The Double Structure of Dharmadhatu (Realm of Reality) and the Meaning of Sokushin (_??__??_)

the fundamental scripture of the Shin-on-sect(真 言 宗)of Japanese esoteric Buddhism. As a matter of f act, we find in the Bud dhavatamsaka-sutra almost all the important terms of the Vairocanabhisannbodhi-sutra such as Vairocana, vikurvita, adhisthana, simhavijrmbhita, vyuhalamkara etc. It is our surmise, however, that the more important point of the Bud dhavatamsaka-sutra as the theoretical foundation of the Vairocanabhisambodhi-sutra lies in the fact that it offers us an image of the realm of reality (dharmadhatu Mme), the double structure of which is completely similar to that of the world of the Vairocanabhisambod hi-sutra. This double structure of dharmadhatu clarifies the true