Masahiro Kondo

Surface Tension Model Using Inter-Particle Force in Particle Method

Moving particle semi-implicit (MPS) method is widely used for the free surface flow analysis. In small scale problems, the surface tension is dominant. There are two approaches to calculate surface tension in particle methods. One is based on continuum mechanics governing equation which needs the normal vector and the curvature calculation. However, it requires complex formulation. The other is introducing inter-particle potential force. It is known that surface tension can be deduced from inter-molecular force. We propose inter-particle force whose potential is similar to the molecular potential. We reveal the inter-relation between this potential force and the surface tension coefficient used in continuum mechanics. The surface tension can be calculated using this inter-particle potential force. The oscillation cycle roughly agrees with the theoretical value. It is also important to introduce the contact angle to the solid wall, as well as the surface tension. The inter-particle force is also available to model the contact angle. The potential force ratio between fluid-fluid and fluid-wall can be derived from Young’s equation. Using this theoretical ratio of potential force, a larger contact angle appears, if we give a smaller potential force ratio.Copyright

Elastic objects for computer graphic field using MPS method

Physics simulations play an important role on computer graphics in recent years. We newly adopt MPS(Moving Particle Semiimplicit), which can calculates elastic objects based on continuum mechanics. Interaction is easily evaluated by particle collisions.

Dynamic visualization of eutectic reaction between boron carbide and stainless steel

ABSTRACT To investigate the eutectic reaction process of control-rod materials in a boiling water reactor (BWR), fundamental tests using boron carbide (B4C) powder inserted between stainless steel (SS) plates were performed and dynamically visualized. The eutectic reaction process near the contact area of the two materials and the behavior of molten material and B4C powder were visualized in real time. The temperature, reaction area, and maximum reaction-layer thickness were obtained. The average temperature range of the test was 1455–1481 K. Through dynamic visualization, some important and previously undiscovered phenomena were observed. The solid part of the SS plate and the strong surface tension of the melt retained the melt inside the specimen, preventing it from flowing out from the surface; the melt then invaded the B4C powder region during the reaction. Diffusion of the B4C powder and migration of the nonreacted B4C powder from the B4C powder region through the retained melt to the SS region were observed. This migration accelerated the local reaction growth rate. The time-resolved observation of these dynamic phenomena offers significant insights to the improvement of numerical calculation codes for severe accident analyses of BWRs, including the Fukushima Daiichi nuclear reactors.

An evaluation model to predict steam concentration in a BWR reactor building

When there is no power for cooling the spent fuel pool and conditioning the air in a boiling water reactor (BWR) reactor building, water vapor is generated from the pool and it affects the atmosphere in the building. To consider the impact of the steam in preparing emergency operation procedures, the building atmosphere under various conditions is to be evaluated with reasonably low computational cost. A lumped parameter model to predict the transient behavior of the building atmosphere was developed, in which the evaporation from the spent fuel pool and the condensation to the wall were taken into consideration. A transient behavior of temperature and vapor concentration in a BWR operating floor was predicted with the model. The results and the prediction speed were compared to those of a three-dimensional computational fluid dynamic calculation, and it was confirmed that the model could obtain almost the same results about 280,000 times faster. Parameter studies are conducted with the model, and dominant parameters to the evaporation and the condensation were clarified.

A Study of a Change in the Training Program from Two-weeks to Four-weeks of Fourth-year Undergraduates at the Pharmacy Division, Nagoya City University Hospital.

In Nagoya City University Hospital, a two-week training program for senior students in pharmacy training was carried out up until 1999. The large majority of senior students took a passive role in this pharmacy training course and therefore did not understand that importance of such training. Therefore, the pharmacy training period was extended from two-weeks to four-weeks in 2000. We thus evaluated what differences there were after the training was increased from two-weeks to four-weeks.The four-week training program was found to increase student motivation toward the pharmacy training. Our survey concluded that approximately 69 % of all senior students were interested in pharmacy training and 75% of senior students understood the role of the pharmacist. In addition, 87% of senior students had an improved image of pharmacists after the new pharmacy training. The reason for such an increase was that the senior students gained a better understanding of the reasons for training and also obtained practical experience in pharmaceutical care. These findings suggest that the four-week training program with self-learning exercises was useful for normally passive senior students. It also enabled hospital pharmacists to make an even greater contribution to the pharmacy training program.