Browsing by Author "Li, Yan-Hom"

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DESIGN OF MARINE VEHICLE POWERED BY MAGNETOHYDRODYNAMIC THRUSTER
(2020-01-01)
Chan, Cherng-Shyong
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Cheng, Jia-Hong
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Zeng, Cing-Hui
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Huang, Jen-Rung
;
Chen, Yu-Hsuan
The present study outlines the design of a magnetohydrodynamic (MHD) thruster system which is capable to power a 3-meter ship model cruising at a speed of V = 0.5 m/s using the Lorentz force generated by the electric field and magnetic field in conducting seawater. Based on the computational fluid dynamics (CFD) simulation of a modified Delft 372 catamaran model, the thrust needed to achieve the targeted cruising speed is first estimated. To achieve the estimated magnitude of the thrust, dimensions of thruster modules are designed based on numerical simulations of magnetic field, for better distributions of the strength and uniformity of the magnetic field. Additional CFD simulations of the flows through the thruster module, coupled with magnetic and electric fields, are conducted to realize the hydrodynamics. Consequently, several configurations of thruster modules are manufactured and experimented. A particular configuration of a shielded two-unit module is chosen to power the ship model. Finally, a complete system of MHD-1 marine vehicle, including a ship model, multiple MHD thruster modules and power suppliers, is assembled and tested. The system is shown capable to cruise closely to the targeted speed.
Dynamics of a microchain of superparamagnetic beads in an oscillating field
(2012-10-01)
Li, Yan-Hom
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Chen, Ching-Yao
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Sheu, Shih-Tsung
;
Pai, Jay-Min
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機械工程學系
The dynamics of microchains containing superparamagnetic particles in an oscillating field are studied experimentally. The chains are first formed by a static directional field, and then manipulated by an additional dynamical perpendicular field. The present methodology represents a simple reversible chaining process, whose particles can be re-dispersed after removal of the field. The motion of superparamagnetic chains is dominated by magnetic torque and induced hydrodynamic drag. The effects of key parameters, such as field strengths and the lengths of particle chains, are thoroughly analyzed. Distinct behaviors, from rigid body oscillations and bending distortions to rupture failures, are observed by increasing the amplitudes of oscillating fields or chains' lengths. Because of lower induced drag, a shorter chain follows the field trajectory closely and oscillates more synchronically with the external field. On the other hand, the influences of field strengths are not consistent. Even the overall oscillating phase trajectory in a stronger external field deviates less significantly from the corresponding field trajectory, a stronger dynamical component of the external field results in larger phase angle lags at certain points. The experimental results confirm the criterion of ruptures can be effectively determined by the value of (N*Mn (1/2)), where Mn is the Mason number defined as the ratio of induced drag to dipolar attraction, and N represents the number of particles contained in a chain.
DYNAMICS OF A SUPERPARAMAGNETIC MICROPARTICLE CHAIN IN AN OSCILLATING MAGNETIC FIELD: EFFECTS OF FIELD FREQUENCY
(2017-07-01)
Chen, Ching-Yao
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Lin, He-Ching
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Teng, Che-Jui
;
Li, Yan-Hom
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機械工程學系
Dynamics of an oscillating chain consisting of several magnetic microparticles and driven by oscillating magnetic fields with different frequencies are discussed. Because of a shorter driving time by the external field with a higher field frequency, the oscillating amplitude of the chain reduces. On the other hand, the higher field frequency leads to a faster local angular velocity. These two effects result in inconsistent behavior of the structural stability of the chain, so that the chain ruptures in a field of intermediate frequency. A dimensionless parameter of the reduced frequency is proposed to generally describe the monotonic decrease of the normalized amplitude. The phenomenon of trajectory shift triggered by the higher frequency field is also demonstrated.
Magnetic microchains and microswimmers in an oscillating magnetic field
(2016-01)
Ido, Yasushi
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Li, Yan-Hom
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Tsutsumi, Hiroaki
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Sumiyoshi, Hirotaka
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Chen, Ching-Yao
Superparamagnetic micro-bead chains and microswimmers under the influence of an oscillating magnetic field are studied experimentally and numerically. The numerical scheme composed of the lattice Boltzmann method, immersed boundary method, and discrete particle method based on the simplified Stokesian dynamics is applied to thoroughly understand the interaction between the micro-bead chain (or swimmer), the oscillating magnetic field, and the hydrodynamics drag. The systematic experiments and simulations demonstrated the behaviors of the microchains and microswimmers as well as the propulsive efficiencies of the swimmers. The effects of key parameters, such as field strengths, frequency, and the lengths of swimmer, are thoroughly analyzed. The numerical results are compared with the experiments and show good qualitative agreements. Our results proposed an efficient method to predict the motions of the reversible magnetic microdevices which may have extremely valuable applications in biotechnology. (C) 2016 AIP Publishing LLC.
Manipulating mimicked magnetosome chains produced Using superparamagnetic microbeads in a confined space
(2016-03-05)
Li, Yan-Hom
;
Su, Ting-Yu
;
Chang, Tien-Li
;
Lee, Ya-Wei
;
機械工程學系
In this study, we investigated the dynamics of microchains containing superparamagnetic microbeads under the influence of oscillating magnetic fields in a confined space. The behavior of constrained microchains was investigated experimentally. Chains in confined spaces were first formed using a static directional field or a permanent magnet and then manipulated using an additional dynamical perpendicular field. An oscillating chain in a confined space can be designed to mimic magnetosome chains synthesized by magnetotactic bacteria, which have been exploited recently for various applications in biological and medical sciences. The effects of crucial parameters, such as the lengths of particle chains and sizes of confined spaces, were thoroughly analyzed to observe the distinct behavior and investigate the dynamics of the constrained chains. (C) 2016 Elsevier B.V. All rights reserved.
Manipulations of vibrating micro magnetic particle chains
(2012-04-01)
Li, Yan-Hom
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Sheu, Shih-Tsung
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Pai, Jay-Min
;
Chen, Ching-Yao
;
機械工程學系
We investigate the motion of a micro-chain consisting of several magnetic particles. The chain is firstly formed by a uniform directional field, and then manipulated by a vibrating field. We demonstrate where the chain appears to display distinct behaviors, from rigid body vibrations, bending distortions to breaking failures, by increasing either the chain's length or vibrating amplitude. In addition, the vibrating chain can be successfully driven forward, mimicking a micro-swimmer by connecting particles of different sizes. (C) 2012 American Institute of Physics. [doi:10.1063/1.3675269]
Numerical simulations of magnetic microchain behaviors in the presence of magnetic field
(2019-01-01)
Ido, Yasushi
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Iwamoto, Yuhiro
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Li, Yan-Hom
;
Chen, Ching-Yao
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交大名義發表
Behaviors of a magnetic microchain which is an oscillating motion of micrometer-size magnetic particles' cluster caused by an external magnetic field were investigated numerically. The hybrid simulation code which was based on the lattice Boltzmann method, the immersed boundary method and the discrete particle method was developed. The behaviors of a magnetic microchain depends on the number of magnetic particles in the magnetic microchain, frequency of external alternating magnetic field and the strength of applied magnetic field. Three types of behaviors, i.e., rigid rotational oscillation, rotational oscillation with deforming into S shape and splitting into several chains, depends on the number of magnetic particles.
Self-assembly and novel planetary motion of ferrofluid drops in a rotational magnetic field
(2015-05-01)
Chen, Ching-Yao
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Hsueh, Hao-Chung
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Wang, Sheng-Yan
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Li, Yan-Hom
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機械工程學系
We experimentally investigate the motion of a ferrodrop array in a rotating magnetic field. Magnetized and driven by the external field, the ferrodrops are stretched and self-aligned to form a drop array along the field orientation. An interesting planet-like dual rotation, including local self-spins of individual drops and a global revolution of the drop array, is newly identified. While the drops spin nearly synchronized with the external field, the revolution always lags behind the field and appears a forth and back movement. Prominence of the net revolutionary movement depends on the strength and uniformity of the overall field as well as the number of drops containing in the array. In general, more uniform and stronger rotating field leads to a more prominent global revolution. Phenomenon of such planetary motion can be applied to mix two fluids more effectively than self-spin drops.
Steering of Magnetic Micro-Swimmers
(2013-07-01)
Li, Yan-Hom
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Lin, He-Ching
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Chen, Ching-Yao
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機械工程學系
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Department of Mechanical Engineering
We experimentally investigate the motion of micro-swimmers consisting of several magnetic particles with different sizes. Swimmers are firstly formed by a static unidirectional field, and then manipulated by an additional dynamical perpendicular field. It is known that such magnetic-particle swimmers (or chains) driven by an external field would oscillate with the orientation of the field but lagging behind by a certain phase angle. In this work, we demonstrate if a swimmer subjected to a strong oscillating field which results in an instantaneous phase lag greater than pi/2, the swimmer can be steered perpendicularly to its original direction. Detailed swimming mechanism and trajectory are presented. By this innovative steering technology, orientation of a micro-swimmer can be effectively manipulated without a physical reconfiguration of the external field arrangement.
Structural instability of an oscillating superparamagnetic micro-bead chain
(2014-07-01)
Lin, He-Ching
;
Li, Yan-Hom
;
Chen, Ching-Yao
;
機械工程學系
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Department of Mechanical Engineering
Issues concerning the structural instability of an oscillating micro-bead chain are addressed based on systematic experiments. The patterns of rupture are categorized into two distinct regimes, referred to as a weak ductile fracture and a strong ductile fracture. A weak ductile fracture describes a more rigid rupture, which often occurs in a pronounced oscillation driven by strong field strengths. The position of the rupture usually favors toward the two sides of the chain. An interesting phenomenon of a reversed rupture, wherein the ruptured segments oscillate in opposite directions, is observed when there is excessive field strength. An important consequence of the reversed rupture is to cause permanent failure of the chaining structure. On the other hand, a strong ductile fracture, featuring significant deformation before rupture, is favored in a more viscous solvent fluid. The positions of the breakages in this regime favor the central region of the chain. The prominence of rupture instability is enhanced by a weaker directional field or by a longer chain, which is in agreement with quantitative assessments by the normal forces acting between the interfaces of beads. In addition, results of the present experiments provide further validations of the global criterion for rupture instability given by where Mn and N, respectively, represent the dimensionless Mason number and the number of beads in the chain.
Structural instability of an oscillating superparamagnetic micro-bead chain
(2014-07-01)
Lin, He-Ching
;
Li, Yan-Hom
;
Chen, Ching-Yao
;
機械工程學系
;
Department of Mechanical Engineering
Issues concerning the structural instability of an oscillating micro-bead chain are addressed based on systematic experiments. The patterns of rupture are categorized into two distinct regimes, referred to as a weak ductile fracture and a strong ductile fracture. A weak ductile fracture describes a more rigid rupture, which often occurs in a pronounced oscillation driven by strong field strengths. The position of the rupture usually favors toward the two sides of the chain. An interesting phenomenon of a reversed rupture, wherein the ruptured segments oscillate in opposite directions, is observed when there is excessive field strength. An important consequence of the reversed rupture is to cause permanent failure of the chaining structure. On the other hand, a strong ductile fracture, featuring significant deformation before rupture, is favored in a more viscous solvent fluid. The positions of the breakages in this regime favor the central region of the chain. The prominence of rupture instability is enhanced by a weaker directional field or by a longer chain, which is in agreement with quantitative assessments by the normal forces acting between the interfaces of beads. In addition, results of the present experiments provide further validations of the global criterion for rupture instability given by where Mn and N, respectively, represent the dimensionless Mason number and the number of beads in the chain.
Trajectory shift of magnetic microchains in an oscillating field
(2013-05-01)
Li, Yan-Hom
;
Lin, He-Ching
;
Chen, Ching-Yao
;
機械工程學系
;
Department of Mechanical Engineering
We report an interesting phenomenon of "trajectory shift" of magnetic chains in an oscillating field, when the phase angle lags of chains to the external field exceeding 90A degrees. The phenomenon shifts the oscillating trajectory of chain along a new axis, which is perpendicular to its original axis. Applicability of the phenomenon to a stable chain in various conditions is experimented systematically. The trajectory shift provides an effective manipulating mechanism in micro-electro-mechanical-systems, such as steering of micro-swimmers. We successfully demonstrate that the driven direction of a micro-swimmer can be controlled by shifting its oscillating trajectory without a physical re-configuration of the external field.