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International Journal of Applied Engineering Research ISSN 0973-4562 Volume 11, Number 23 (2016) pp. 11259-11265
© Research India Publications. http://www.ripublication.com
11259
Numerical Simulation of Biomagnetic Fluid Flow in an Oscillating Lid
Driven Cavity
Abdullah A.A.A. Al-Rashed1, Abdulwahab Ali Alnaqi1 and M. A. Hossain2
1Dept. of Automotive and Marine Engineering Technology, College of Technological Studies, The Public Authority for Applied Education and Training, Kuwait.
2Department of Mathematics, University of Dhaka, Dhaka-1000, Bangladesh. *Corresponding author
Abstract
The fundamental problem of biomagnetic fluid dynamics in a
lid driven cavity is numerically studied. The flows are driven
by the top sliding wall, which executes sinusoidal oscillations.
Numerical solutions are acquired by solving a coupled and non
linear system of PDEs, with their appropriate boundary
conditions and by using a finite differences numerical
technique based on simple algorithm. Results are presented for
wide ranges of principal physical parameters, i.e., Re, the
Reynolds number, MnF, the magnetic number and , the non-
dimensional frequency of the lid oscillation. Comprehensive
details of the flow structure are presented. Results concerning
the velocity and skin friction indicate that the presence of the
magnetic field influence the flow field considerably.
Keywords: Biomagnetic fluid, oscillating lid, magnetic fluid,
driven cavity
Nomenclature
,x y
Cartesian coordinates
,x y
non dimensional Cartesian coordinates , /x y L
M
magnetization
H
magnetic field strength
Re Reynolds number = L U
FMn magnetic number 2
0 0HU
t
time
u
velocity in x-direction
u
dimensionless horizontal velocity
v
velocity in y-direction
v
dimensionless vertical velocity
Greek symbols
biomagnetic fluid density
dynamic viscosity
kinematic viscosity
magnetic susceptibility
ω lid oscillation frequency
D dimensionless average drag force
INTRODUCTION
Biological fluid is a fluid that exists in a living creature. The
fluid dynamics of biological fluids in the presence of applied
magnetic fields is biomagnetic fluid dynamics (BFD). Due to
its bioengineering and medical applications, an extensive
research work has been done on this relatively new area, during
the last decades [1-3]. Development of magnetic devices for
cell separation, magnetic wound or cancer tumor treatment
causing magnetic hyperthermia, targeted transport of drugs
using magnetic particles as drug carriers, reduction of bleeding
during surgeries or provocation of occlusion of the feeding
vessels of cancer tumors and development of magnetic tracers
[4-7].
Biomagnetic fluid flow is analogous to the principals of
FerroHydroDynamics (FHD) and Magneto Hydro Dynamics
(MHD) where the magnetization and the Lorentz force are
dominating force in the flow field. Magnetization is the
measure of how much the magnetic fluid is affected by the
magnetic field and a function of the magnetic field intensity. In
FHD, the flow is affected by the magnetization of the fluid in
the magnetic field [8]. MHD deals with conducting fluids and
the mathematical model ignores the effect of polarization and
magnetization.
Blood can be considered as a magnetic fluid [1]. Moreover, it
can also be considered as diamagnetic, paramagnetic or
ferromagnetic fluid depending upon certain conditions. Mature
red blood cells contain the hemoglobin molecule, in the form
of iron oxides at a exclusively high concentration, so it can be
considered as the most characteristic biomagnetic fluid [9]. The
orientation of the erythrocyte disk plane is parallel to the
magnetic field [10]. Oxygenated blood behaves like a
diamagnetic material whereas paramagnetic when
deoxygenated [11].
Incompressible viscous flow in a closed container constitutes
an important subject, from the standpoints of both theoretical
analyses and technological applications. Fluid flow of viscous
fluid in a driven cavity has been considered as a benchmark
configuration for numerical and experimental model validation
[12–15]. Concerning the practical applications, researchers are
interested in understanding the unsteady cavity flow
phenomena. Time periodic flows in cavity can be viewed as
prototypes for studying mixing processes. A typical
configuration of unsteady flow in cavity is constructed by a
moving top lid with a sinusoidal or cosinusoidal motion [16–
18]. Soh and Goodrich [17] studied the fluid flow within a
closed finite square cavity, driven by a sliding wall that
executes sinusoidal oscillation. They found that the variation of
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 11, Number 23 (2016) pp. 11259-11265
© Research India Publications. http://www.ripublication.com
11260
the fluid flow structure due to the oscillating motion of the lid
in one complete cycle. Later, Iwatsu et al. [18] conducted a
numerical study of flow driven by a torsionally oscillating lid
in a square cavity for a wide range of Reynolds numbers and
frequencies of the oscillating lid. They reported that the effect
of the lid motion penetrates a larger depth into the cavity at low
frequencies, and flow is similar to the steady driven cavity flow
at the maximum plate velocity. However, the flow was
confined within a thin layer near the oscillating lid, at high
frequencies.
The fundamental problem of the biomagnetic fluid flow in a
steady lid driven cavity under the influence of localized
magnetic field has been conducted by Tzirtzilakis and Xenos
[19]. They concluded that the flow field influences
considerably in the presence of the magnetic field. Also the
influence of the magnetic field on the flow is local and is
confined close to the area of application of the magnetic field.
From the above discussion and an exhaustive survey of
literature, it reveals that there has not been much work on the
periodic nature of fluid flow in a cavity. Furthermore, such
studies have been limited to pure lid driven cavity flow
problem. To the best of the authors’ knowledge, the problem of
biomagnetic fluid flow in a square cavity driven by a
periodically oscillating lid, has not yet been studied. The
objective of the present work is to obtain extensive
computational results of the biomagnetic fluid flow in the
driven cavity with an oscillating lid. Complete flow details
have been acquired over wide ranges of some principal
parameters, i.e., Reynolds number, magnetic number and
oscillation frequency. The solution of the problem is obtained
numerically by the development of an efficient numerical
methodology based on the SIMPLE algorithm.
MATHEMATICAL FORMULATION
The problem under consideration is the viscous, steady, two–
dimensional, incompressible, laminar biomagnetic fluid
(blood) flow inside a square duct under the influence of an
applied magnetic field. The length and height of the duct is L
and the axes intersect at the bottom left corner of the square
duct with coordinates (0, 0) i.e the origin of the Cartesian
system is at the bottom left corner of the cavity. The flow is
subject to a magnetic source, which is placed very close to the
lower plate of the cavity and below it. A schematic
representation of the flow field as well as the magnetic field
strength contours are given in Figure 1.
Figure 1: Contour lines of the dimensionless magnetic field
strength
Blood is assumed as a homogeneous Newtonian fluid,
according to the mathematical model of BFD [1, 20-22] and the
principles of FHD [23-26]. The apparent viscosity due to the
application of the magnetic field is considered to be negligible.
The rotational forces acting on the erythrocytes, when entering
and exiting the magnetic field are discarded (equilibrium
magnetization). Moreover, The Lorentz force due to the
electrical conductivity of blood is considered negligible
compared to the magnetization force. Thus, blood is also
considered electrically non-conducting fluid.
The governing equations of the fluid flow, under the action of
the applied magnetic field, are similar to those derived in FHD.
Hence at the cavity flow the dimensional velocity components
(bar above the quantities) u , v and pressure p are governed
by the mass conservation and the fluid momentum equations at
the x , y directions, which are given respectively by
Continuity equation:
0u vx y
(1)
Momentum equations:
2 2
02 2
1u u u p u u Hu v Mt x y x x y x
(2)
2 2
02 2
1v v v p v v Hu v Mt x y y x y y
(3)
The boundary conditions are
Upper wall ( , 0 ): sin , 0
Lower wall ( 0, 0 ): 0, 0
Left wall ( 0, 0 ): 0, 0
Right wall ( , 0 ): 0, 0
y L x L u U t v
y x L u vx y L u v
x L y L u v
(4)
In the above equations , is the biomagnetic fluid density,
is the dynamic viscosity, 0 is the magnetic permeability,
/ is the kinematic viscosity, M is the magnetization
and H is the magnetic field strength.
In equations (3) and (4) equation terms 0 /M H x and
0 /M H y represents, respectively, the component of the
magnetic force per unit volume, and depends on the existence
of the magnetic gradient.
For the variation of the magnetization M , with the magnetic
field intensity H experiments which has been carried out in [2]
showed that it can be fairly approximated by the linear relation
[11]
M H (5)
where, is a constant called magnetic susceptibility. The
components of the magnetic field intensity xH and yH along
the x and y coordinates, ,x yH H H is given respectively
by
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 11, Number 23 (2016) pp. 11259-11265
© Research India Publications. http://www.ripublication.com
11261
2 22 2
,2 2
x yy b x aH H
x a y b x a y b
(6)
where ,a b is the point where the magnetic source is placed
and γ is the magnetic field strength at this point ,x a y b .
The magnitude H of the magnetic field intensity, is given by
1/ 2
22
1, ,
2x yH x y H H
x a y b
(7)
The conservation equations of mass and momentum are non-
dimensionalized by introducing the following non-dimensional
variables and numbers into the conservation equations:
2
0 0 0
2
0 0
, , , , ,
, , , ,
Re (Reynolds number),
(Magnetic nmber)
yxx y
F
x y u v px y u v pL L U U U
HHtU L Ht H H HL U H H H
L U
HMnU
(8)
where 0 ,0H H a .
Applying these non-dimensional variables and numbers the
non-dimensional conservation equation of mass and
momentum together with the boundary conditions may be
written as follows:
0u vx y
(9)
2 2
2 2
1
ReF
u u u p u u Hu v Mn Ht x y x x y x
(10)
2 2
2 2
1
ReF
v v v p v v Hu v Mn Ht x y x x y y
(11)
Upper wall ( 1, 0 1): sin , 0
Lower wall ( 0, 0 1): 0, 0
Left wall ( 0, 0 1): 0, 0
Right wall ( 1 0 1): 0, 0
y x u t vy x u v
x y u vx y u v
(12)
The magnitude H of the magnetic field intensity is also derived
from the relations (8) and (9) is given by:
2 2,
bH x y
x a y b
(13)
NUMERICAL METHODOLOGY
The governing equations are discretized using the finite
difference method while the coupling between velocity and
pressure fields is done using the SIMPLE algorithm. The
diffusion terms in the equations are discretized by a second
order central difference scheme, while a hybrid scheme (a
combination of the central difference scheme and the upwind
scheme) is employed to approximate the convection terms. The
convergence of solutions is assumed when the relative error for
each variable between consecutive iterations is recorded below
the convergence criterion ε such that
1
1
n n
n
U UU
(14)
where n denotes the number of iterations and the convergence
criterion was set to 10−6.
RESULTS AND DISCUSSION
The verification of the present numerical code is carried out in
two folds. First, since there is no public data available for
biomagnetic flow inside an oscillating lid-driven cavity, the
present numerical code was validated with the previous
benchmark solutions of pure lid-driven flow in a square cavity
reported by Iwatsu et. al. [18]. By considering the magnetic
parameter 0FMn , our present numerical simulation for
biomagnetic flow becomes pure lid-driven cavity flow
problem. Typical time history of the drag force for Re = 400 at
different frequencies (low and moderate) are presented in
Figure 2 together with the previous result of lid driven flow
with oscillating lid [18]. It is found that there is a very good
agreement between the present results and the previous study
performed by Iwatsu et. al. [18].
Figure 2: A representative time history of force coefficient,
Cf, for Re = 400 for frequency = 0.1 and 1.0.
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 11, Number 23 (2016) pp. 11259-11265
© Research India Publications. http://www.ripublication.com
11262
(a)
(b)
Figure 3: Streamlines for Re = 400 and various values
of MnF = 1 and 8 (a) Tzirtzilakis and Xenos [19] and (b) Present
The second fold is a comparison between the predicted stream
function contours for Re = 400 and various values of MnF (MnF
= 1, 4 and 8), under steady state condition of the present work
to that of Tzirtzilakis and Xenos [19]. As displayed in Figure 2,
the comparison strikes an excellent agreement between both
studies. These validation cases enhance the confidence in the
numerical outcome of the present work.
After validation of the present code for pure lid-driven cavity
flow with an oscillating motion of the top lid, simulation of
biomagnetic fluid dynamics for the oscillating lid case was
carried out. The flow field becomes periodic with an identical
frequency to the oscillating lid. To ensure the periodic steady
state of the fluid motion, results after a sufficient number of lid
oscillation cycles are considered.
t = T/8 t = T/4 t = 3T/8 t = T/2
t = 5T/8 t = 3T/4 t = 7T/8 t = T
Figure 3: Streamline plots during a complete period of the cycle at Re = 400, ω = 1.0 and MnF = 0
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 11, Number 23 (2016) pp. 11259-11265
© Research India Publications. http://www.ripublication.com
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The contour lines of stream function have been constructed to
visualize the overall flow patterns inside the cavity at different
instants, caused by the oscillation of the lid motion and some
typical pictures are shown in Figure 3 for Re = 400, ω = 1.0 and
MnF = 0.0. Temporal variations of the streamline plots during
a complete period are displayed in Figure 3. Each period was
divided into eight intervals. The first four intervals represent
first half of the cycle. The next four intervals represent the
second half of the cycle which is exhibits a perfect temporal
reversal of the first half of the cycle. Initially, a leading primary
vortex appeared which occupies the whole region of the cavity
at t = T/8. A secondary vortex at the upper portion of the right
side wall and two small counter-rotating vortices at the two
corners of the bottom wall is also observed along with leading
vortex. As a result of the no-slip condition between the fluid
and solid wall, a clockwise vortex forms just below the lid at t = T/4. This clockwise vortex amplifies and merges with the top
right secondary vortex and eventually engages the maximum
space of the cavity. Accordingly, in the last interval of the first
half cycle, the central counterclockwise vortex that emerge at
beginning of the period, gradually reduces in size and
eventually becomes a secondary vortex at the upper portion of
the left wall. The phenomenon observed in the first half of the
cycle reverses in the second half as the fluid flow is forced by
a sinusoidal oscillation.
t = T/8 t = T/4 t = 3T/8 t = T/2
t = 5T/8 t = 3T/4 t = 7T/8 t = T
Figure 4: Streamline plots during the complete cycle at Re = 400, ω = 1.0 and MnF = 1
The flow field revealed significant changes in the location and
number of vortices with the variation of magnetic force which
is depicted in Figure 4. As MnF was increased from 0 to 1,
together with the vortices that created for the pure lid driven
flow, a single prominent minor vortex at the center of the
bottom wall is created because of the influence of the magnetic
field.
MnF = 0 MnF = 1 MnF = 4 MnF = 8
Figure 5: Streamline plots for different values of MnF at a instant t = 3T/8, Re = 400 and ω = 1.0
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 11, Number 23 (2016) pp. 11259-11265
© Research India Publications. http://www.ripublication.com
11264
At the beginning of the period, the bottom wall centre vortex
merge with right side corner vortex and ultimately merge with
the vortex that is created under the lid. At the end of the first
half cycle, a vortex due to magnetic force appeared again at the
center of the bottom wall and in the opposite direction.
Furthermore, as MnF increased from 1 to 4, a similar trend for
vortex formation is observed. The centre vortex of the bottom
wall increased with increasing values of magnetic force.
Fluid flow inside the cavity with various values of magnetic
number at the instant t = 3T/8 is shown in Figure 5, where Re
and ω is considered to be 400 and 1.0 respectively. A
remarkable variation of flow occurs for the implementation of
the magnetic field. An increase in MnF at a given oscillation
frequency and at a given instant promotes the development
vortices. Therefore, fluid is well mixed at higher values of
magnetic number.
Figure 6: Variation of the drag force predictions, for
Re = 400 and MnF = 4 at different frequencies
( = 0.1, 1.0 and 5.0)
Finally, to cover a wide range of lid frequency, ω = 0.1, 1 and
5 were used as the input variables. The effect of lid frequency
on the predicted drag force is displayed in Figure 6. This figure
illustrates how quickly the steady periodic solution is reached
for various values of . From Figure 6 it is observed that steady
periodic solution reaches quicker for large and for small
frequency, = 0.1 more cycles are required to reach a steady
periodic solution. It is observed that the drag force follows the
same sinusoidal behavior of the external excitation offered by
the sliding lid. Furthermore, it is noticed that magnitude of the
drag force increase with an elevation of frequency value.
CONCLUSION
Bio-magnetic fluid flow within a square cavity with an
oscillating upper lid has been investigated numerically. The
investigation was carried out for the magnetic number and the
oscillation frequency of the sliding lid. The steady-periodic
natures of the solutions have been captured. A profound effect
of magnetic numbers on the flow field structure has been
recognized. Formation of vortices within the cavity amplifies
with the increasing values of MnF which accelerates the mixing
of the fluid. As the oscillation frequency increases at a fixed
MnF, the number of vortices within the cavity decreases. Steady
periodic solution is reached faster for small values of the
normalized frequency. Moreover, the results indicate that drag
force increases with an increasing values of the lid frequency.
The numerical results of this study could be useful in
biomedical applications and analyzing the behavior of the fluid
driven by oscillatory motion of the lid and the influence of the
magnetic field.
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