Resonance Behavior in Ferrofluid with Oscillatory Shear Flow

全文

(1)

Title

Resonance Behavior in Ferrofluid with Oscillatory Shear Flow

Author(s)

Yamada, Y.; Enomoto, Y.

Citation

物性研究 (2006), 87(1): 76-77

Issue Date

2006-10-20

URL

http://hdl.handle.net/2433/110644

Right

Type

Departmental Bulletin Paper

Textversion

publisher

(2)

研究会報告

Resonance Behavior i

n

F

e

r

r

o

f

l

u

i

d

with O

s

c

i

l

l

a

t

o

r

y

Shear

Flow

Dept. of Environmental Technology

Nagoya Institute of Technology Y. Yamada

Y. Enomoto

磁性流体は、コバルトフェライト、マグネタイト、バリウムフェライトなどの磁性ナノ粒子の水 性あるいは油性コロイド溶液であるo我々は、磁性流体の振動場におけるレゾナンス的振る舞いに ついてコンピュータシミュレーションを行い、シェア率と周波数との関係性を調べた。

Introduction

Magnetic fluid is an oil or a water-based colloidal suspension of ferromagnetic nanoparticles such as Cかferrite

magnetite and Ba-ferrite [1

]

[2]. Sinceもheproperties of these fl uids can be easily influenced by an external field, they have recently attracted much scientific and technolog -ical interest [1]

[2]. There are many app1ications such as magnetic日uidrotary seals

magnetic clutch

and turnable dampers. We studied final states of microscopic structure of ferrofluid by changing shear rates and frequency and obtained three typical aggregational patterns of ferrofluid.

1

The

10del

We assume spherical particles dispersed in a suspension in a thin plate. The coating layer. of each particle causes a repulsive force between particles. .On the other hand

the dipole-dipole interaction causes attractive force between particles. We consider a magnetic field in the z-axis

shear flow in the direction of the x-axis. direction of magnetic field is in the z-axis. When chain structure is made

we add an oscillatory shear along the x-axis without the external magnetic field

Under these conditions

the equations of motion ofri =町 孟 十 抗 女

+

ZiZ (translational motion)

and ni (rotational motion) for interacting particles: The

2

、 、 . , , , , 唱 EA , , s 、 N

3

7

=

守Z(

X:十自乞(弓

+FZ)+

(t)

]

~" j(針) (2) ﹃ n M × ↓ 川

+

、 4 ィ J ﹃ m - - u .

+

引 引 い V , N

μ 州 17v

+

A Y ・ 7

2 一 一 日 叫 一 - d

whe

民 山 弓

isthe force on the i-th particle due to the dipole-dipole interaction between pa山 lesi and j

isthe short ra暇 帥ulsiveforce due to surfaωnt

isthe dipole induced

(3)

76-「ソフトマターの物理学 2006J to同ueand 1'

}

i

is the to同ueinduced by the external magnetic日eld

with the translatior凶 d時 force coefficient,Ct三 6wα'fJヲandthe rotational drag force coefficient,Cr

=

=

8wα3'fJ・Theseforces are given by [1

]

[2]

3 Conclusions

We obtained three typical patterns of the fainal state. The transient process and the equation for the relationship between γ

(shearrαte)αndw(frequency)isunderthewαy.

Z L 1 0 0 1 │ O │

0

.

0

1

1

+

1

'

"

0

.

0

5

-

C _

1

+

l

0

.

1

C

¥

B

I

J

l

l

e

~J

0

.

5

C~国

C

C

1

.

0

IC

c

c

図1:Ph邸ediagram of microstructures for various values of the frequency ωand shear magnitude

γo (C: Chained pattern; 1: isotropic pattern)

参考文献

[1] Rosensweig R.E. Ferγvhydrodynamics New York:Cambridge University Press

(1987).

[2] S. Odenbach

Mαgnetoviscoω Effects in Fe作'ofiuids

Springer

Berlin

2002

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