Group Title: 7th International Conference on Multiphase Flow - ICMF 2010 Proceedings
Title: 4.5.3 - Numerical Simulation of Micro Particles Deposition in Realistic Geometry of Deviant Human Nasal Airways
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 Material Information
Title: 4.5.3 - Numerical Simulation of Micro Particles Deposition in Realistic Geometry of Deviant Human Nasal Airways Particle-Laden Flows
Series Title: 7th International Conference on Multiphase Flow - ICMF 2010 Proceedings
Physical Description: Conference Papers
Creator: Moghadas, H.
Abouali, O.
Faramarzi, A.
Ahmadi, G.
Publisher: International Conference on Multiphase Flow (ICMF)
Publication Date: June 4, 2010
 Subjects
Subject: septum deviation
micro particle
deposition
CFD
 Notes
Abstract: 3-D models of both sides of human nasal passages were developed to investigate the effect of septal deviation on the flow patterns and micro particles deposition in the realistic human nasal airways. 3-D computational domain was constructed by a series of coronal CT scan images before and after septoplasty from a live 25-years old nonsmoking human with septal deviation in his right side nasal passage. For several breathing rates correspond to low or moderate activities, the steady state flow in the nasal passage was simulated numerically. Lagrangian approach was used for simulation of micro particles motion. The flow field and particles depositions are strongly depend on passage geometry. The abnormal passage has more particles deposition comparing with the normal side and post-operative passages because of rapid change in geometry. For micro particles, regional depositions are completely different for these three passages while total deposition is the same for the post-operative and normal cavity. Despite the anatomical differences of the human subjects used in the experiments and computer model, the simulation results are in qualitative agreement with the experimental data.
General Note: The International Conference on Multiphase Flow (ICMF) first was held in Tsukuba, Japan in 1991 and the second ICMF took place in Kyoto, Japan in 1995. During this conference, it was decided to establish an International Governing Board which oversees the major aspects of the conference and makes decisions about future conference locations. Due to the great importance of the field, it was furthermore decided to hold the conference every three years successively in Asia including Australia, Europe including Africa, Russia and the Near East and America. Hence, ICMF 1998 was held in Lyon, France, ICMF 2001 in New Orleans, USA, ICMF 2004 in Yokohama, Japan, and ICMF 2007 in Leipzig, Germany. ICMF-2010 is devoted to all aspects of Multiphase Flow. Researchers from all over the world gathered in order to introduce their recent advances in the field and thereby promote the exchange of new ideas, results and techniques. The conference is a key event in Multiphase Flow and supports the advancement of science in this very important field. The major research topics relevant for the conference are as follows: Bio-Fluid Dynamics; Boiling; Bubbly Flows; Cavitation; Colloidal and Suspension Dynamics; Collision, Agglomeration and Breakup; Computational Techniques for Multiphase Flows; Droplet Flows; Environmental and Geophysical Flows; Experimental Methods for Multiphase Flows; Fluidized and Circulating Fluidized Beds; Fluid Structure Interactions; Granular Media; Industrial Applications; Instabilities; Interfacial Flows; Micro and Nano-Scale Multiphase Flows; Microgravity in Two-Phase Flow; Multiphase Flows with Heat and Mass Transfer; Non-Newtonian Multiphase Flows; Particle-Laden Flows; Particle, Bubble and Drop Dynamics; Reactive Multiphase Flows
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Resource Identifier: 453-Moghadas-ICMF2010.pdf

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7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010


Numerical Simulation of Micro Particles Deposition in Realistic Geometry of Deviant
Human Nasal Airways


Hajar Moghadas1, Omid Abouali1, Abolhasan Faramarzi2 and Godarz Ahmadi3

'School of Mechanical Engineering, Shiraz University, Shiraz, Iran
2Ear, Throat and Nose Department, Shiraz Medical University, Shiraz, Iran
3Mechanical and Aeronautical Engineering Department, Clarkson University, Potsdam, NY, USA
abouali @shirazu.ac.ir


Keywords: Septum deviation, micro particle, deposition, CFD



Abstract

3-D models of both sides of human nasal passages were developed to investigate the effect of septal deviation on the flow
patterns and micro particles deposition in the realistic human nasal airways. 3-D computational domain was constructed by a
series of coronal CT scan images before and after septoplasty from a live 25-years old nonsmoking human with septal
deviation in his right side nasal passage. For several breathing rates correspond to low or moderate activities, the steady state
flow in the nasal passage was simulated numerically. Lagrangian approach was used for simulation of micro particles motion.
The flow field and particles depositions are strongly depend on passage geometry. The abnormal passage has more particles
deposition comparing with the normal side and post-operative passages because of rapid change in geometry. For micro
particles, regional depositions are completely different for these three passages while total deposition is the same for the
post-operative and normal cavity. Despite the anatomical differences of the human subjects used in the experiments and
computer model, the simulation results are in qualitative agreement with the experimental data.


Introduction

The human nasal airways play an important role in the
respiratory system. This part filters, tempers and humidifies
the inspired air and protects lung from toxic particles by
capturing them. The deviation in the nasal airways is a
common disease which makes septoplasty one of the most
often performed operations. It is desired to predict the flow
patterns inside the nasal airways and its relation to
geometric variation because of deviation. A detailed
investigation of the flow field for the extremely complex
human nasal airway can be very helpful for successful
surgery in the cases of impaired respiration due to injuries or
abnormal shape nasal airways. Even normal airways have a
highly complex system both geometrically and functionally
and as the Fig. 1 shows this complexity get more for
abnormal airways.
Flow transports through human nasal passages have been
studied experimentally by several researchers. Schreck et al.
(1993) used a hot wire device on 3-times magnified plastic
model of a nose based on MRI images. They reported that
the main part of the breathing air passes through the central
part of the nasal passage while only a small fractions passes
through the meatuses and the olfactory region.


Figure 1: Schematic of the lateral view for the right nasal
cavity of a volunteer. IT and MT refer to inferior and middle
turbinates. IM and MM refer to inferior and middle
meatuses.

Kelly et al. (2000) fabricated a model from CT scans images
and used Particle Image Velocimetry (PIV) for velocity
measurement. They reported that the flow was laminar for a
breathing rate of 15 L/min and a significant part of the flow
passes through inferior airway while a small portion of the
flow passes through olfactory slit and meatuses. It was also
found from their experiments that the inspired air attains the
highest velocity in the nasal valve and the inferior turbinate
regions. Kim and Chang (2003) discussed the effect of
geometry variation on the flow field. They studied three
geometric variations of the middle turbinate experimentally









and showed that the flow field was depending strongly on
the geometry variation.
Some numerical studies of the flow field inside the human
nasal passages have been reported in the literature by
Keyhani et al. (1995), Subramaniam et al. (1998), Zhao et al.
I 1 14,, Weinhold and Mlynski (2004), Shi et al. (2006) and
Wen et al. ',2. ,i,, In addition, the detail of the investigation
for the effect of the septal deviation on the flowfield inside
the nasal passage in present study was brought in
Moghaddas et al. (2009).
Several researchers have studied particles transports through
human nasal passages experimentally and numerically.
Swift (1991), Guilmette et al. (1994) and Zwartz and
Guilmette (2001) measured the capture of ultrafine particles
in human nasal passage for different particles size and flow
rates. Kesavatanthan et al. (1998) carry out in vivo
measurements of the (1-10m) particles deposition in the
human nasal passages for 40 subjects. In their work, they
also studied the effect of nasal cavity characteristic on nasal
deposition efficiency. Cheng (2003) used in vivo and replica
measurements and suggested an improved formula of nasal
deposition for both inertial and diffusion regimes.
Wiesmiller et al. (2003) investigated particles deposition in
inspiration and expiration for particles range of 1-30 itm.
They reported that more particle deposition takes place
during inspiration and a small fraction deposit during
expiration. Kelly et al. (2004) measured the deposition of
nano and micro particles in nasal airway replicas created by
stereo-lithography with different surface quality, SLA nasal
replica model with greater surface roughness than Viper
nasal replica model with smooth surface. They reported that
the surface quality do not significantly affect the nasal
deposition efficiency of nano particles. However, the micro
particles deposition efficiency is strongly depend on surface
roughness.
Stapleton et al. ,2 1,1, Martonen et al. I 'I 12,l, Kleinstreuer
and Zhang i' I ), Zhang et al. i' 2 I 4, DeHaan and Finlay
,2 "4,i, Matida et al. (2006) and Breuer et al. (2006) used
Eularian-Lagrangian approach to simulate micro particle
transport and deposition in the human upper respiratory
system. Shi et al. (2007) studied the inertial particles
deposition in nasal airway, subject to steady laminar flow
rates of 7.5 and 20 L/min. They created a selective
micro-size airway-surface layer to investigate the effect of
wall roughness. Liu et al. ,2ii ') studied the total deposition
of submicron aerosols with different size at several constant
flow rates. Inthavong et al. (2009) investigated the
deposition of particles, particularly the nanoparticles and
micron particles (1-10lm) under different steady laminar
flow rates by using the Lagrangian approach. They
discussed the significance and influence of different factors
that are applicable to micron and nano particles and the
detailed local deposition patterns.
The effect of pathologic conditions such as the presence of
polyps, swelling, atrophy or resection of turbinates and
enlarged adenoids in the nasal airflow were studied with
cadaver models by Tonndrof (1939), Proetz (1951), Swift
and Proctor (1977). Grutzenmacher et al. (2006) studied the
presence of compensatory hypertrophy of turbinates. Their
reports showed that these conditions changed the flow
patterns in the nasal cavities with different order.
Xiong et al. (2008) simulated the nasal cavity airflow pre
and post virtual functional endoscopic surgery (FESS). They


7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010

selected a healthy subject, and applied CFD techniques to
construct a three-dimensional nasal model based on nasal
CT scans. A virtual FESS intervention performed
numerically on the normal nasal model using Fluent
software. Airflow, velocity and pressure distribution were
calculated and compared in both the pre and post FESS
models. Their results showed that in the post-FESS model,
there was an increase in airflow distribution in the maxillary,
ethmoid and sphenoid sinuses, and a 13% increase through
the area connecting the middle meatus and the surgically
opened ethmoid. There was a gradual decrease in nasal
resistance in the posterior ethmoid sinus region following
FESS.
Chung and Kim (2008) used PDIV procedure to study nasal
airflow, airflow in quite respiration and change to airflow
after modification of the nasal turbinates. They also
investigated the flow patterns in both nasal cavities of one
asymptomatic deviated nasal septum patient. Their
experimental results showed that generally the flow patterns
and major pathways in the middle airway were similar in
both concave and convex cavities with that of airflow in the
normal nasal passage.
There are no published reports on the symptomatic deviated
nasal septum. While the normal nasal septum would be a
straight midline structure between right and left nasal
passages, most of people have some degree of twist or
irregularity of the nasal septum. The deviated septum is
presenting generally congenital, but may also be because of
accident. However, the number of symptomatic persons
with deviated nasal septum is lower than that of
asymptomatic patients.
In this study, several computer models of the nasal airway
are developed from a human with nasal septal deviation
who referred to otolaryngolgist with chief complaint of right
side nasal obstruction. The flow field in the nasal passages
is investigated pre and post-operatively. The nasal septum
deviation causes nasal obstruction, desiccated and epistaxis.
Quality of Patient life was mostly affected when the
curvature of the septum makes nasal obstruction. Deviation
and obstruction can occur at any point of the bony or
cartilaginous septum. Nasal septum deviation becomes
clinically important when leads to functional or aesthetic
morbidity. Small changes at the septum can significantly
narrow the internal nasal valve, which can further result in
dynamic collapse of the upper lateral cartilages.

Nomenclature


CD
Clip
d
g
Re
u


Particle Drag Coefficient
Cunningham slip correction factor

Particle diameter ( In)
Gravitational constant (ms-2)
Relative particle Reynolds number
Particle velocity (ms-1)


Greek letters
/1 Fluid viscosity (Pas)
p Particle density (kgm3)
A Air mean free path (/Mn)








Numerical Scheme

1. Computational model of the nasal airway

The creation of an accurate 3-D model of the airway with
complex geometry is the first step for simulation of flow
field in the nasal airway. Here the coronal cross sections of
the nasal cavities obtained by CT scan of an adult man
human subject were used to construct a smooth airway
passage for the pre and post-operative cases for both sides.
CT scans were taken three months after the septoplasty as
shown in Fig. 2.
The major deviation is located in the main airway region.
Septal deviation started from a section with 30mm distance
from the nose tip by decreasing the area of the airway. In the
nasal valve region asymmetry between the left and right
cavity is clear which is because of deviation. In the
beginning of the main airway region at 46mm distance from
the nose tip, deviation divided the right airway to two
separated parts. This continued to the section with 50mm
distance from the nose tip. Deviation decreased the cross
sections area and the total volume of the passage. This made
some breathing problem for the patient. Two separated parts
become a unit part again in the section with 72mm distance
from the nose tip but with a different form compared with
the left side cavity. The deviation ended in the beginning of


7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010

nasopharynx. In fact, the coronal cross sections distanced 2
mm apart were used to produce a 3-D model. Fig. 2 shows
only some selected sections. As it can be seen two separated
parts of the airway in the right side were changed in the
septoplasty to a unit airway. The right side cavity
approximately looks like a normal passage post-operatively.
The left side volume was approximately 36.7 percent
greater than the right side volume pre-operatively while this
difference decreases to 15 percent after surgery.
For generation an accurate 3-D model from 2-D coronal
cross sections, it is necessary to have good information and
knowledge about the real geometry of nasal airway. Since
the coronal sections in the main airway have complex
geometries especially for the abnormal nasal airways,
creation of the 3-D passage from the coronal sections was
difficult and time consuming. The complexity of the
reconstruction process has been also reported before by
Kimbell (2001) and Zamankhan et al. (2006) who used
different methods and also studied normal nose.
The 3-D geometry of human nasal airways was
reconstructed in four steps. At first step, CT-Scan images
with proper resolutions from a volunteer man with septal
deviation in the right cavity pre-operatively were taken. In
the second step using MTALAB software, CT-Scan images


22mm


30mm


38mm 46mm


50mm


72mm
Pre-Operative


imm 22m
1mm 22mm


30mm


38mm 46mm








50mm 72nmm
Post-Operative


Figure 2: Left and right 2-D coronal cross sections for a nasal passage of an adult human at various distances from the nose tip.
The patient had a septal deviation in the right side pre-operatively.


.4 i\


1mm








with DICOM format were processed and the boundary
coordinates of the walls of the nasal cavities were
identified. Then in the third step, the outcome of the image
processing was imported into CATIA software and the
nasal airway volume was created. Final 3D volume from
CATIA was exported to mesh generation software
GAMBIT to produce a 3D computational domain. The
generated unstructured computational grid includes
approximately 800,000 tetrahedral elements. Several finer
computational grid sizes were also used to investigate the
effect of grid refinements on the computational results by
checking the velocity in 5 various optional points. This
comparison showed that the numerical results are
independent from the grid size for a computational grid
with 600,000 cells or more. The initial generated grids
generally had high skewness because of the complexity of
the nasal passages. A high amount of task was done to
decrease this skewness and this resulted to a better
convergence in numerical solutions and decreases the error
residuals of the computations. For simulation of the airflow
and particle transport and deposition, the FLUENT (6.3.12)
software was used.


2. Governing Equations and Boundary conditions

As noted before, the experimental studies of Swift and
Proctor (1977), Hahn et al. (1993) and Kelly et al. (2000)
have shown that the flow in the nasal cavity is laminar for
low to moderate activities corresponding to a breathing rate
of 15 L/min or less. In this study the airflow in the nasal
cavity for low to moderate activities was of interest.
Therefore, a laminar flow regime was assumed. The
particle concentration assumed to be low and effect of
particles on the flow was neglected and a one-way coupling
was used. In this approach, the airflow field was first
simulated, and then the trajectories of individual particles
were calculated. As it was noted before the detail of the
governing equations and results for the flowfield were
reported by Moghaddas et al. ii r,' "'
The micro particle transport and deposition calculation
were performed by a Lagrangian approach using following
equation:

duf 3uCD, Re ( -u)+ (1)
dt 4ppd

In Equations (3), uf is the particle velocity, dp is the

particle diameter, pp is the particles density, p/ is the
fluid viscosity, g is the acceleration gravity,
Re (Rep = pu u d I/ ) is the particle Reynolds

number, CD, define as ( CD =CD/ Clip ) that

CDCD 24 (1+ 0.15Re0687)) is the particle drag
Re
coefficient,

Cs(Ci =1+ 1.257 + 0.4exp -1.1 ) is
d, 2/2


7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010

the Cunningham slip correction factor, A is the air mean
free path.
For the passage wall, a no slip flow boundary condition
was used. At the nostril and at the outlet (the beginning of
nasopharynx) pressure boundary conditions were set. A
zero gage pressure was set at the nostril and various
negative gage pressures were set at the outlet. For
estimating the micro particle deposition, it was assumed
that if the distance between the particle center and the
surface was less than or equal to the particle radius the
particle will attach to the surface and the possibility of the
particle rebounding from the passage surfaces was ignored.


Results and Discussion

1. Flow field simulation

The Reynolds numbers in three passages based on the
average velocity and hydraulic diameter of the nostril is in
the range of 100-450 for all studied cases. As mentioned in
the previous studies the flow regime is laminar for these
ranges of Reynolds number that corresponds to the rest
inspiration in a normal nasal cavity. The flow could not be
turbulent in the abnormal shape cavity in this condition
because as it will shown later, the velocity magnitude of
flow in the abnormal shape cavity is less than that for a
normal cavity in the same pressure difference.
Fig. 3 shows the stream lines of airflow inside the cavities
pre and post-operatively. Air flow enters from the nostril to
the vestibule region and turns 90 degree to the nasal valve
region and then reaches to the main airway region.


Figure 3: The stream lines of the airflow inside the cavities
pre and post-operatively for 40 Pa pressure difference.
The stream lines expanded through the passages before









operation while they contracted after operation and most
of the flow passes through the middle of passage. Also
after septoplasty the mass flow rates has increased which
results in a higher velocity too. The mass flow rates for
various pressure differences, in the right cavity pre and
post-operatively and the left cavity are compared in Fig.
4.


3.5E-04 -
3.0E-04 -
&D
2.5E-04 -
-
2 .0E-04 -
S1.5E-04
1.OE-04 -
5.0E-05 -


e L4eft-efore Surgery
---Right-Before Surgery
-f-Right-After Surgery


0 10 20 30 40
Pressure Drop(Pa)
Figure 4: The air mass flow rates in the right cavity before
and after the septoplasty and the left cavity, for various
pressure drops in the nasal passages.
As the results show for the same pressure difference, the


giF ure 5: particle deposition in
after septoplasty.


7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010

amount of the flow passing through the right cavity before
septoplasty is much smaller than that for the right cavity
after septoplasty. However, the right post-operatively
passage has approximately a breathing rate as equal as that
for the normal left cavity. For this patient, at given pressure
differences, the nasal airflow distinction for the abnormal
right cavity before septoplasty and the left normal cavity
were approximately 40 to 50 percent. Nevertheless, after
septoplasty the distinction reaches to 5.6 percent and less
for these cavities.


2. Particles deposition

2-1. Total Deposition

Mono dispersed particles in the range of 1-50jtm were
released passively into the nasal airway with pressure drop
of 10-40 Pa. Fig. 5 shows particles deposition in three
different passages for particle diameters in the range of
5-20jtm and 40 Pa pressure difference, before and after
septoplasty. Regarding to this figure for a given passage the
particle deposition increases as the particle size increases.


na d 20pm particles a d


Right before operation Right after operation Left
AP = 40Pa AP = 40Pa ---- AP = 40Pa
d=5pmn d = 5pmn d =5pm




^ "- .





Right before operation Right after operation Left
AP = 40Pa AP = 40Pa AP = 40Pa
d = 1Opm d =10 4, m d = 10pm









Right before operation Right after operation Left
AP=40Pa AP= 40Pa AP= 40Pa
d 20pm t d 20m a.. d = 20
d=)lO d=)m d=lcun
*Jc"t L ^a L
: i^ if
__w_________








At the end of the vestibule region that flow turns 900 to the
nasal valve region with rapid variation in geometry, the
inertial impaction increases the particles deposition
especially for larger particles. Because of high inertia, the
particles cannot follow the streamlines. In the pre-operative
right cavity a significant amount of particles deposit in the
beginning of the main airway region where the deviation
started. While in the other passages, only a small fraction
of particles reaches to this region and this fraction becomes
smaller as the particles size becomes larger. In fact, the
local deposition is completely different for various
passages. This shows the great rule of geometry on the
micro particles deposition in the nasal passages. In the
pre-operatively right cavity there is not any particles in the
olfactory region for diameters of 5 and 10ltm and only a
few 20ltm particles reach to this region. This is not


7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010

favorable for drug delivery. However, more particles are
able to reach to the olfactory region in the post-operatively
right cavity. While the flow and particles patterns in the
nasal airway are strongly affected by the septal deviation, it
is very important to investigate the effect of septal
deviation on the patient subjected to drug delivery. Fig.6
shows particles deposition in three different passages, right
cavity before and after septoplasty and left cavity for 10ltm
particle and two various pressure difference of 10 and 40
Pa. Comparisons indicate that in a given passage, particles
depositions increase as pressure difference between inlet
and outlet of the passage increases.
As the pressure difference increases, the mass flow rate
increases too for each passage. Results confirm that for
micro particles deposition the inertia is the dominant
mechanism.


Deviation Right before operation
eviationPa

A P =10PadlO


Ir
4.~


Right after operation
AP =10Pa


A. \-.4 -
'1F N


d =l1Op





. *


Left
AP =10Pa
d =lOpm


*. V1


4;~d


Right before operation
AP = 40Pa
d = 10pum











1Right after operation
AP = 40Pa
S d=lO0pm
k iv ..







* Right after operation
*P = 40Pa
d=l10um


I~S

-.%

A .
1*


Left
AP = 40Pa
d = lpm


t pl


Figure 6: particles deposition in three different passages, left and right before and after septoplasty for 10gtm particle at 10 and 40 Pa
pressure difference.


I _








Particles trajectory and axial velocity contours (the velocity
normal to the coronal section) in three coronal sections
located in vestibule, nasal valve and the main airway
regions of the nasal cavities are shown in Fig. 7 for both
cases before and after septoplasty. The results are presented
for two different particle diameters of 10 and 20lm at 40
Pa pressure drop. In the vestibule region there are more
particles in the cross section of pre-operatively cavity
because as mentioned before for the same pressure
difference the post-operatively cavity passes bigger flow
rate and so the inertia impaction of particles become
stronger and thus more particles deposit in vestibule region
of the post-operatively cavity. This causes that the less
particles to be seen in the cross sections of post-operative


7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010

cavity comparing with pre-operatively case. In the nasal
valve and main airway regions the particles trajectory are
completely different for cavities before and after
septoplasty. Regarding to Fig.7 in the post operatively
sections the distribution of particles are in the middle and
upper areas while for the pre-operative section, particles
seen in the entire section. In addition, more particles
deposition occurs for 40 Pa pressure drop compared with
10 Pa pressure drop so there are less particles in the
sections for 40 Pa pressure drop, Fig.5. Because of
particles deposition in the earlier regions, only a few
particles are able to reach to the final region of the nasal
passage especially for the lager particles and higher mass
flow rates.


AP = -40 Pa d=10am
axial-velocity(m/s)
Before 3.20 After
2.83
2.45
2.08
1.70
1.33
0.95
: 0.57
0.20


(a) Vestibule

axial-velocity(m/s)
Before 7.00 After
6.19
5.38
4.56
3.75
2.94
2.13
1.31
0.50


(b) Nasal Valve

axial-velocity(m/s)
Before 4.5 After

3.5
3
2.5
2
1.5

0.5

(c) Main Airway


AP=-40Pa, d=20 m
axi al-velocity(m/s)
Before 3.20 After
2.83


1.70
1.33
0.95
0.57
0.20

(a) Vestibule

axial-velocity(m/s)
Before 7.00 After
6.19
5.38
4.56
3.75
2.94
2.13
1.31
0.50


(b) Nasal Valve

axi al-velocity(m/s)
Before 4.5 After
4
3.5
3
2.5
2
1.5

0.5

(c) Main Airway


Figure 7: Axial velocity contours in different coronal sections of the right cavity for pre and post-operative cases for 10 and 40 Pa
pressure drops ((a) Vestibule, (b) Nasal Valve, (c) Main Airway)










A comparison of the results of this study with the previous
experimental works is represented in Fig.8 which shows
the deposition efficiency versus the impaction parameter
for different passages and pressure drop of 10 Pa.
Impaction parameter is defined as IP=d2Q.


1 .* EXP.kelly et al (2004)
RB
0o.8 RAR
S -5 L
S0.6 -


a D.

0.2


102 103 104 105 106
d Q[gm2cm3/s]

Figure 8: comparison of the results of present study for 10 Pa
pressure difference with the experimental data for deposition of
mirco particles.


Earlier investigations have shown that this parameter is
very important characterization of deposition efficiency of
micro particles. Difference between the present results and
experimental data can be justified with the anatomical and
geometrical differences. The shape of the nose in this study
is abnormal while the previous models were normal. In
addition, the experimental models usually have wall
roughness while the computer model has smooth wall.
As the results showed for the same pressure difference, the
pre-operative cavity has bigger deposition fraction
compared with the post-operative one because the septum
deviation deviates the streamlines sharply which this
increases the inertia impaction. As mentioned before the
flow rate is smaller in the pre-operative cavity for the same
pressure difference. Maximum total efficiency of the micro
particles for 10 Pa pressure difference corresponds to
IP=26,733 nm2cm3 /s is 79% for right pre-operatively
cavity, 44% for right post-operatively cavity and 35% for
the left cavity. So the maximum difference of deposition
efficiency is 35% between the right pre-operatively and the
normal left cavity. This reduces to 12% after the
septoplasty. Although the efficiency of the right
post-operatively cavity becomes close to the left cavity but
it should be mentioned that the local deposition of these
two passages are completely different. The reason is
geometrical dissimilarity and variation of the flow patterns
in the passages. Fig.9 shows deposition efficiency versus
impaction parameter for pressure variations of 10, 20 and
40 Pa. As it is clear, the curves approximately duplicate
each others. This confirms that in the Fig.8 the differences
between the various curves are due to geometrical
differences.


7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010


Right before operation
1 ---AP=10 Pa
--AP=20 Pa
0.8 -AP=40Pa
0.6

10.4-
0.2

a
102 103 104 10 106
d Q [g m2 cm3/s]

Right after operation
I --AP=10 Pa
S -kAP= 20 Pa
o 0.8 _,AP=40Pa
0.6-
0.4 -

0.2 '

102 103 104 105 106
d2Q[m2 cm3/s]

Left
1 I-AP=10 Pa
S *AF=20 Pa
S0.8 -*-AF=40Pa
S0.6 -
0.4 -
Ca0- ,A?


Figure 9: deposition efficiency versus impaction parameter
for pressure variation of 10, 20 and 40 Pa


2-2. Local deposition of micro particles

Local deposition of 5, 10 and 20 ltm particles are shown in
Fig.10 for pressure differences of 10 and 40 Pa in three
various passages. For the case of the 10 Pa pressure drop,
in the right post-operative cavity and the normal left cavity,
the vestibule and nasal valve regions have significant
particles deposition compared to the right pre-operative
cavity. That is because of passing a higher mass flow rate
through the post-operative and left cavities. However, the
main airway region of the right pre-operative cavity shows
more particles deposition because of the rapid change in
the geometry due to septum deviation.
However, increase of pressure drop from 10 to 40 Pa,
increases the mass flow rate and this affects the larger
particles more due to their higher inertia. As Fig.10 (a-2,
b-2, c-2) shows, for 40 Pa pressure difference most of 20
itm particles deposit in the vestibule and nasal valve
regions, so less particles of this range could reach to the
main airway region. Surely, each large particle that is able


103 104 10s
d Q [/m2 cm3/s]









to reach to the main airway region will deposit there.
In the right post-operative cavity, for both studied pressure
drop and various particle sizes, the most particle deposition
occurs in the vestibule region. The larger particles then will
deposit in the nasal valve region. While smaller particle
about 10 jtm diameter are able to pass from the nasal valve
region but most of them deposit in the main airway region.
The less fraction of smaller particles (smaller than 5 unm)
deposit in the nasal airway and most of them exit to the


7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010

oral airway. In the left cavity, for both studied pressure
drops and various particle sizes, the highest particle
deposition occurs in the vestibule region and then in the
nasal valve region. Higher particles deposition in the nasal
valve of the left cavity compared with the right
pre-operative cavity is due to rapid change in geometry of
the passage in the left side where the nasal valve jointed to
the vestibule region, refer to Fig.2.


Before operation Before operation
AP= 10Pa 1 AP = 40 Pa
0 Vestibule Vestibule
0.8 Nasal Valve Nasal Valve
S0.6 Main airway = 0.6 0 Main airway

0.4 0.4 -
0.2 0.2
0 0
5 10 20 5 10 20
d (pm) d (pm)
(a-1) (a-2)
After operation After operation
1 AP= 10 Pa AP= 40 Pa
Vestibule Vestibule
S0.8 Nasal Valve 08 Nasal Valve
0.6 Main airway 0.6 Main airway
o C
S0.4 0.4
i 0.2 0.2

5 10 20 5 10 20
d(pm ) d(pa)
(b-1) (b-2)
Left Left
1 AP= 10 Pa 1 AP= 40Pa
U Vestibule 5 1 Vestibule
S0.8 Nasal Valve 0.8 NasalValve
S0.6 Main airway 0.6 Main airway
04 00.4
02
0

5 10 20 5 10 20
d (pm) d (pm)
(c-l) (c-2)
Figure 10: The Local deposition of 5, 10 and 20 ltm particles for pressure difference of 10 and 40 Pa in three variant passages.


Conclusions

The following conclusions can be mentioned from the
present computer simulation.
1. The amount of the breathing rate in the studied abnormal
human nasal cavity is approximately 40-50 percent less
than that for a normal human nasal cavity.
2. The numerical results of this study show that the Septal
deviation causes several breathing problems for a person
with abnormal shape cavity because who must produce


bigger mines pressure for having the normal nasal air flow
in inspiration.
3. After an appropriate septoplasty for an abnormal shape
cavity, the nasal airway can have the breathing rates as
equal as the normal nasal cavity.
4. The abnormal shape passage has more particles
deposition compared with the normal passages because of
rapid change in geometry.
5. Maximum deposition decreases 60% for 15 jtm particles
after septoplasty for a typical volume air flow rate.









The post-operative and normal passages have different
regional depositions for micro particles while their total
depositions are nearly the same.
6. The dominant mechanism of micro-particles distribution
is inertia and, consequently, increase of particles diameter
and flow rate leads to an increase of micro-particle
deposition.


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