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Numerical Simulation for Fluid Dynamics
We investigate interaction between fluid and material with numerical simulation

I. Splash's form by Moving Particle Semi-implicit Method

The purpose of this study is to understand a splash, taking account of hydrophilic and hydrophobic properties of a solid object in numerical simulations. The splash generated by a diving sphere with these properties into water is simulated by using the Moving Particle Semi-implicit (MPS) method. The difference of properties is described by the strength of interaction between the particles that represent respectively the solid surface and water. The strength is adjusted so that results coincide with the experimental ones under the same condition. The hydrophilicity that shows weak strength is regarded as a slip flow on the surface. This affects behavior of the flow that is generated along the surface of object in the moment that the sphere contacts the water surface.

II. How to eat a hamburger beautifully ?!
When eating a large hamburger, how should you have it? In order to eat without spilling, it is good to press down a hamburger opposite you eat with your fingers at equal intervals. The movie shows the simulation result when you eat a hamburger at the left side. The right side is pressed by fingers in this case, thus particles do not spill.
III. Dripping of water around the glass
We often look out a water dripping from the edge of cup and adhesion to the wall. We applied the proposed model of the electrostatic attractive force (topic I) to this problem. With introducing the electrostatic attractive force, water drips around the edge of cup and water adheres to the wall. So, we could say, the calculation result was improved by electrostatic model.
IV. Non-linier mixing for μTAS, (FEM)

The effects of forced synthetic vibration on mixing in a circular flexible container were investigated numerically for a -TAS (Total Analysis System). The synthetic forced vibrations consisted of the modevibration in the normal direction to the circular wall and the rotation of node/antinodes’ positions of the vibrating wall by changing the phase of piezo actuators. The synthetic vibration yielded the rotating flow in the container without mechanical rotors. An injected droplet stretched and mixed with surrounding liquid by the strained flow field. The higher stretching of the droplet occurred near the vibrating wall. The degree of the stretching increased with increasing rotation speed and mode number. We showed that the synthetic vibration could induce high strained flow fields in the container even if the Reynolds number is low.

(c) M.Yokoyama