nan Novitrian

Studying Brazil-Nut Effect History Line using Disk- Formed Objects, Scanner, and Web Browser

Grains configuration snapshots of Brazil-nut effect (BNE) in two-dimension are physically modeled using disk-formed objects, e.g., buttons and magnetic pin. These BNE configurations are artificially designed to mimic the real ones observed in experiments. A computer scanner is used to capture the configurations. Obtained images are then digitized using web browser running an HTML equipped with a JavaScript code, which is built mainly only for this work. From digitization process all grains positions (granular bed and intruder) are obtained, which is later analyzed using the simplest model, i.e., potential energy. Since the minimum energy principle (MEP) suggests that a closed system should go to its state with minimum internal energy, our BNE system must also obey it. Evolution of only the intruder seems to violate MEP but not for the whole system. Grains compaction plays an important role, so that the system can achieve its configuration with minimum potential energy.

Development of single fluid volume element method for simulation of transient fluid flow in self-siphons

A simple model for transient flow in a narrow pipe is presented in this work. The model is simply derived from Newtons second law of motion. As an example it is used to predict flow occurrence in two forms of self-siphon, which are inverted-U and M-like forms. Simulation for system consists only a vertical pipe is also presented since it is actually part of the both siphon systems. For the simple systems the model can have good predictions but for the complex system it can only have 89.6 % good prediction. Its simplicity can be used to illustrate how the interface between fluid and air, single fluid volume element (SFVE) moves along the siphon. The method itself is named as SFVE method.

Competition between potential energy minimization and number of contact points in two-dimension granular materials exhibiting Brazil-nut effect

The granular materials phenomenon known as Brazil-nut effect is discussed in this work, where its grain configurations are constructed artificially as time-independent using 2-d disks. Single intruder with 2.6u2005cm diameter is introduced to granular bed consisted of 1.3u2005cm diameter disks. Each created configuration is designed similar to observed one in experiments and simulations. Potential energy and number of contact points between grains are observed between initial and final configurations. Contactopy parameter change is also discussed. As comparison results from real experiment and simulation are also presented.

Segmented self-siphon: Experiments and simulations

Observation of fluid flow in a segmented self-siphon has been conducted experimentally and a model using molecular dynamics method is used to study the phenomenon in simulation. Influence of number of parts used in vertical straight segments observed in the simulation is nearly similar to the result observed in experiment. Mismatch error between experiment and simulation results, in predicting whether water can flow in a configuration of segmented a self-siphon or not, has been found about 10.4 %. During the flow through the self-siphon water velocity decreases, especially in the semi-circle bends.

Modeling and characterization of charged particle trajectories in an oscillating magnetic field

A constant magnetic field has frequently been discussed and has been known that it can cause a charged particle to form interesting trajectories such as cycloid and helix in presence of electric field, but a changing magnetic field is rarely discussed. In this work, modeling and characterization of charged particle trajectories in oscillating magnetic field is reported. The modeling is performed using Euler method with speed corrector. The result shows that there are two types of trajectory patterns that will recur for every 180nT0 (n = 0, 1, 2, ..) in increasing of magnetic field oscillation period, where T0 is about 6.25 × 10−7 s.

Simulation of fluid flow in a U-shape self-siphon and its working space

Observation of occurrence of fluid flow in a U-shape self-siphon has been conducted experimentally and in simulation. Water is chosen as the fluid. In experiment, three kinds of pipe inner diameter d (4, 6, and 8 mm) have been used to find its influence to the flow occurrence. The U-shape self-siphon has three different segments, where length of the first segment plays important role for the flow occurrence. The segment has length L + h, which stands for length above and below water surface in water container, respectively. In simulation, head (interface between water and air in the siphon) equation of motion is solved numerically using Euler method. Working spaces of L against h for several d have been produced from simulation and experiment, and they show a good agreement to each other. It can be observed that the relation between L and minimum h for flow to occur becomes more linear for larger inner diameter d.