Presentations

Magnetic fluid tuned liquid column damper (MF-TLCD) is a kind of semi-active damper that uses magnetic fluid as its working fluid. We quantitatively investigated the damping coefficient generated by the flow of magnetic fluid, which is strongly related to the damping performance. Three kind of U-pipes that have each different shape ((1) conventional (2) equipped with an orifice (3) curved fluently) were prepared and single-degree-of-freedom oscillation was performed with each those pipes. Finally, we discussed the effect to the damping performance of MF-TLCD induced by various damping coefficient subjected to magnetic field and configurations of those U-pipes.

磁性流体同調液柱管ダンパーはU字管内の磁性流体液柱を付加振動系とする制振装置で、磁場印加によって液柱固有振動数の制御が可能である。本研究では異なる三つの形状のU字管容器で加振実験を行い、それぞれの比較検討を行った。

矩形流路内を流れる磁性流体に直流磁場・交流磁場を印加した場合の流動特性を調べた。圧力損失と超音波伝播速度を計測し，磁性体微粒子のクラスタが流れ場に及ぼす影響を調べた。

We investigated the forced convective heat transfer of a magnetic fluid flow with applying uniform magnetic field in the axial, vertical, and parallel direction in relation to the heat transfer direction.

We investigated the cluster formation and the effect of clusters on two-dimension flow in a square duct under DC and AC magnetic fields. We measured the pressure drop in a test section and ultrasonic propagation velocities in order to clarity the influence of DC and AC magnetic fields on flow resistance.

Forced convective heat transfer and flow resistance of rectangular duct flow of a magnetic fluid by applying non-uniform magnetic field was investigated experimentally. One characteristic result shows that heat transfer is largely enhanced by applying non-uniform magnetic field in the laminar flow regime. Comparing with the result with applying uniform magnetic field, heat transfer enhancement is larger than that with applying uniform magnetic field. This seems that thermal convection excited by applying non-uniform magnetic field strongly affects the heat transfer.

This paper presents experimental analysis of magnetorheological fluid (MRF) under alternating magnetic fields. The experiments were conducted under alternating magnetic fields. MRFs of different volume fraction of two types were used in this study. The relation between the change of ultrasonic propagation velocity, the difference of volume fraction and frequency of magnetic field were discussed. As a result, for high volume fraction, the cluster size was affected by frequency of magnetic field rather than for low volume fraction.

This paper reports experimental studies about anisotropy and attenuation as characteristics of ultrasonic propagation in a magnetorheological fluid (MRF) under AC magnetic fields. Parameters of this studies are magnitude of AC magnetic fields, frequencies of AC magnetic fields and angles between directions of ultrasonic propagation and magnetic field. As results of change rate of sound velocity, MRF has characteristics of time dependence, frequencies dependence and anisotropy under AC magnetic fields. Also, length of clusters in MRF became short with increase of frequencies of AC magnetic fields. The clusters in MRF are formed along the magnetic force under AC magnetic fields. Attenuation decreased with increase of the angles between directions of ultrasonic propagation and magnetic field. But, attenuation did not change with increase of frequencies of AC magnetic fields.

The ultrasonic velocity profiler was used to investigate the influence of non-uniform magnetic field on the velocity distribution of the rectangular duct flow of a magnetic fluid. The results showed that the flow velocity at the upper-leaning side from the center of the duct increased and the velocity gradient at only the bottom wall side, which electromagnet exists, decreased in the laminar flow. In contrast, in the case of turbulent flow, not only velocity gradient but also flow velocity near the center of the duct hardly changed by applying magnetic field. This is because magnetic field intensity is not so strong that the velocity distribution is affected.

The effect of magnetic field on two-layer sloshing with magnetic fluids and silicone oil were studied. Frequency-pressure response was recorded to conduct research. The permanent magnets were placed near the interface of two fluids. The resonant frequencies were changed by the positions of the magnets, the type of magnets, and the direction of the magnetic field. This study shows the possibility that two-layer fluid sloshing with magnetic fluids can be controlled by the intensity and the direction of magnetic field.

現在提案中のセミアクティブ型制振装置である磁性流体液柱管ダンパーの制振特性を検証するため，磁場による固有振動数制御時の制振特性について，構造物-ダンパー系の加振実験を行い，従来型液柱管ダンパーとの比較・検討を行った。

磁性流体に磁場を印加すると磁場方向に鎖状クラスターが形成され，この形成方向が熱物性に影響を与えることが指摘されている。そこで，本研究では，磁性流体の対流熱伝達へ及ぼす磁場印加方向の影響を調べた。

Frequency response analysis of a tuned liquid column damper using magnetic fluid (MF-TLCD) based on a linearized method was presented. An MF-TLCD alters the natural frequency of the magnetic fluid column that forms the resident liquid inside the MF-TLCD by applying a magnetic field. The interaction equations of motion under a harmonic type of loading for SDOF damped structure and liquid surface motion in a MF-TLCD were expressed. The damping term induced by liquid flows and the magnetic force term were linearized to derive analytical solutions. The analytical results were compared with experimental results.

We conducted experimental studies as the ultrasonic propagation characteristics of a magnetic fluid (MF) under AC magnetic fields. The change rate of sound velocities were related to the formation of clusters in MF and it decreased with increase of AC frequencies.

We carried out experiments on two-layer sloshing using a magnetic fluid and silicon oil, and measured displacements of free surface and interface by a laser sensor. We also carried out theoretical investigation using a linear short-wave theory. We compared with experimental and theoretical results.

This paper presents an investigation on the effect of chamfered orifice inlet on magnetorheological (MR) fluid subjected to shock loading. Two different orifices (no chamfer and chamfered at 60 degrees angle on the inlet area) are used. The MR fluid is subjected to a shock loading, and the magnetic field is applied on the orifice area. Experiments have been conducted by measuring piston displacement, impact force and pressure difference between the inlet and outlet of the orifice. Based on the experiment result, the effect of chamfered orifice inlet on MR fluid subjected to shock loading is discussed.

Magnetic fluid TLCD (MF-TLCD) is a novel type of semi-active damper in which the natural frequency can be controlled by applying magnetic field. We tuned the natural frequency of a column of magnetic fluid to excitation frequency, and demonstrated that the damping performance can improved compared with the case without magnetic field.

We conducted experiments on two-layer sloshing in a layered mixture of a magnetic fluid and silicone oil, and measured the dynamic pressure change using four pressure transducers. We also investigated the effect of excitation amplitude on natural frequency and on dynamic pressure change in the presence and absence of an applied magnetic field. Although the magnetic field altered the natural frequency, the change was almost constant even as the excitation amplitude was varied.

We designed a new semi-active Tuned Liquid Column Damper (TLCD) which uses Magnetic Fluid as its working fluid (MF-TLCD). We investigated the damping characteristics of MF-TLCD which has the two electromagnets, and considered transition of the natural frequency that is strongly related to the damping performance. We presented the momentum equation of MF-TLCD, and solved it numerically. Numerical results were compared with experimental results.

Ultrasonic propagation velocity in a magnetic fluid under compression was investigated. Ultrasonic propagation velocity in a magnetic fluid changed with the magnetic flux density and the compressive force. This change is related with cluster formation in a magnetic fluid. Experiment results indicated that cluster formation in a magnetic fluid seemed strongly affected by compressive force.