Presentations

This study examines how megasound-induced streaming affects nucleated bubble behavior and heat transfer in the subcooled flow boiling of Novec 7100, which is crucial for advanced electronics cooling.

This paper reports an experimental study of applying pendulum theory to determine whether a rectangular model of a hull would overturn. A pontoon used as a non-self-navigating work vessel was considered in this study. Its model begins to list when an unbalanced load is applied. It can then either stabilize in an inclined state or continue overturning, throwing the unbalanced load midway, and finally stabilizing in the inverted position. In a mid-air experiment, this correlation was made between two motion scenarios, pendular or rotational motion. The two motions were reproduced by changing the distance between the hull center and the rotary axis and the mass of the weight. The experimental results closely matched those of an analytical analysis performed based on the Runge-Kutta method, which confirms the validity of the proposed analysis.

The ultrasonic wave propagation velocities of MR fluid under DC and AC magnetic fields were examined. Experiments were conducted to investigate the effect of magnetic field sweep rate on the cluster formation in MR fluid.

MR fluid is one of the functional fluids affected by the magnetic. When a magnetic field is applied to MR fluid, MR fluid can change its property because of clustering structure. We measure the ultrasonic propagation property through MR fluid under AC magnetic fields. We use two indexes: ultrasonic velocity change rate and attenuation rate. Based on the experimental results, we analyze the clustering structure in MR fluid.

The properties of ultrasonic propagation velocity in MR fluids (MRF122-EG and MRF132-DG) are studied experimentally.We measured ultrasonic propagation velocity with the pulse method. We used AC magnetic fields with the frequency of 1 Hz and 2 Hz, and the intensity of 50 mT and 75 mT.The change of cluster formation were confirmed by applying different frequency or magnetic flux density.

We proposed a mechanical model of MR fluid pipe flow and compared with the experiment results of the flow under an impact load, and conducted drop impact tests with four types of tapered metering pins and qualitative analysis of effects of the pins. The results show that the shape of the pins has some effect on the entire shock absorption process whereas magnetic field strength affects the post-peak behavior only, and shock absorption with a longer tapered pin is more widely controllable by magnetic field.

Forced convective heat transfer of turbulent magnetic fluid flow is remarkably suppressed by applying magnetic field. The result shows that the suppression becomes stronger by applying stronger magnetic field, but is saturated at a certain strength of magnetic field. This suppression depends on not only magnetic field intensity but also flow condition. The relationship among heat transfer, magnetic field intensity and flow condition was discussed.

Keynote lecture about magnetic and MR fluids flows was presented.

Streamwise variation of the suppressed turbulent diffusion of magnetic fluid flow in downstream of the magnetic field region was investigated experimentally. Reynolds number based on hydraulic diameter and bulk mean velocity were varied from 6400 to 14300, and magnetic field was applied up to 500 mT. The result shows that the recovery of suppressed heat transfer in downstream of the magnetic field region is strongly related with flow velocity and magnetic field intensity. Distance for recovering the suppressed turbulent diffusion from the magnetic field region becomes shorter in larger Reynolds number flow. The relationship among the recovery distance of the suppressed turbulent diffusion, magnetic body force and inertial force of the flow was discussed.

We performed vibration experiments for three types of U-pipes, and obtained the following results: (1) The shape of the bottom and elbow of the U-pipe has no influence on the natural frequency change of an MF-TLCD (Magnetic-Fluid Tuned Liquid Column Damper) when a magnetic field is applied. (2) When using a U-pipe with an elbow with a larger curvature, it is possible to reduce the damping force on the liquid column and improve MF-TLCD performance.

Using four types of tapered metering pins, we conducted drop impact tests and a qualitative analysis of effects of the pins on MR fluid with a magnetic field applied around an orifice area. The tapered metering pins changed the piston stroke. The results indicate that the shape of the pins has some effect on the overall shock absorption process whereas magnetic field strength affects the post-peak behavior only. These results show that a tapered metering pin has applicability to shock absorbers using an MR fluid.

The suppression of turbulent heat transfer and the recovery of the suppressed heat transfer in the downstream of magnetic field region was investigated experimentally in more detail. The result shows that the suppression of heat transfer becomes large by applying stronger magnetic field but is saturated at a certain strength of magnetic field with relation to flow velocity. The recovery of suppressed heat transfer in downstream of the magnetic field region is also related with magnetic field intensity and flow velocity.

Pressure drop in a square duct flow of a magnetic fluid was investigated experimentally. DC and AC magnetic fields were applied to the flow. The pressure drop under DC magnetic field was larger than that under the AC magnetic field. When AC magnetic field was applied, the frequency of the pressure drop was twice of that of the AC magnetic field from FFT analysis.

We carry out theoretical and experimental study for the resistance force of MR fluid flow in a circular pipe. The purpose of this study is to calculate resistance of MR fluid based on the analysis and to compare the experimental results with the calculated results. The resistance force acting on a cylinder piston with tapered pin depends on the strength of magnetic field, tapered angle, etc. It is proved that the most dominant effect to the resistance force is magnetic field.

We investigated the free surface fluctuation of liquid in a rotating cylindrical container which receives horizontal vibration in the horizontal direction. In the experiments, we changed the oscillation frequency f and the rotation frequency. We measured time dependent pressure fluctuation instead of free surface fluctuation. By performing FFT analysis, two significant frequencies are obtained. We also examined these results using linear wave theory.