ISSN 2355-6927

PROCEEDINGS
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ISSN 2355 6927

PROCEEDING
SEMINAR NASIONAL THERMOFLUID VI 2014
29 April 2014
Yogyakarta, Indonesia

DISELENGGARAKAN OLEH:
JURUSAN TEKNIK MESIN DAN INDUSTRI
FAKULTAS TEKNIK
UNIVERSITAS GADJAH MADA

SEMINAR NASIONAL THERMOFLUID

2014

ISSN 2355 6927

SEMINAR NASIONAL THERMOFLUID VI 2014

Yogyakarta, 29 April 2014

Untuk segala pertanyaan mengenai makalah Thermofluid VI:

Ruang Administrasi S2 Jurusan Teknik Mesin dan Industri
Fakultas Teknik - Universitas Gadjah Mada
Jalan Grafika No.2 Yogyakarta 55281
Phone: (0274) 521673
Email: thermofluidvi@gmail.com
Website: thermofluid.ugm.ac.id

Reviewer:
Prof. Dr. Ir. H. Djatmiko Ichsani, M.Eng. (ITS)
Prof. Dr. Ir. Harinaldi, M. Eng. (UI)
Dr. Ir. Anhar Riza Antariksawan (BATAN)
Prof. Ir. I Made Bendiyasa, M.Sc., Ph.D. (UGM)
Prof. Dr.-Ing. Ir. Harwin Saptoadi, M.SE. (UGM)
Dr.Eng. Tri Agung Rohmat, B.Eng., M.Eng. (UGM)
Indro Pranoto, S.T., M.Eng. (UGM)
Adhika Widyaparaga, S.T., M.Biomed.Sc., Ph.D. (UGM)

Editor:
Dimas Dwi Ananda
Avila Dhanu Kurniawan
Ogy Satria Ramadhan
Muhammad Ilham Kurniawan
Ilham Adityarsena F
Putra Juliansen Siregar

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DEWAN REDAKSI

Penanggung Jawab

: Prof. Ir. Jamasri, Ph.D.

(Ketua Jurusan Teknik Mesin dan Industri, Fakultas Teknik
UGM)

Panitia Pengarah

: 1. Sugiyono, ST., MT., Ph.D.

(Kepala Lab. Mekanika Fluida)
2. Dr.Eng. Tri Agung Rohmat, B.Eng., M.Eng.
(Kepala Lab. Konversi Energi)
3. Dr. Ir. Prajitno, MT.
(Kepala Lab. Perpindahan Kalor dan Massa)

Reviewer

: 1. Prof. Dr. Ir. H. Djatmiko Ichsani, M.Eng. (ITS)

2. Prof. Dr. Ir. Harinaldi, M. Eng. (UI)
3. Dr. Ir. Anhar Riza Antariksawan (BATAN)
4. Prof. Ir. I Made Bendiyasa, M.Sc., Ph.D (UGM)
5. Prof. Dr.-Ing. Ir. Harwin Saptoadi, M.SE. (UGM)
6. Dr.Eng. Tri Agung Rohmat, B.Eng., M.Eng. (UGM)
7. Indro Pranoto, S.T., M.Eng. (UGM)
8. Adhika Widyaparaga, S.T., M.Biomed.Sc., Ph.D.

Ketua Panitia

: Dr. Eng. Khasani, S.T., M.Eng.

Sekretaris

: Adhika Widyaparaga, S.T., M.Biomed.Sc., Ph.D.

Bendahara

: Fauzun, S.T., M.T., Ph.D.

Koord. Pelaksana

: Fadhli Akbar

Sekretaris Pelaksana

: Puput Iin Quraini

Bendahara Pelaksana

: Arfin Aruni Silma

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DAFTAR ISI
Halaman Judul ....................................................................................................................

Dewan Redaksi ................................................................................................................... iii

Kata Pengantar .....................................................................................................................

Daftar Isi .............................................................................................................................

vi

A. Combustion Engineering
1. Gelombang Detonasi Marginal Campuran Bahan Bakar Hidrogen & Udara
dengan Pengencer Argon
Jayan Sentanuhady, Ari Dwi Prasetiyo ......................................................................... 1
2. Pengaruh Excess Air terhadap Karakteristik Pembakaran dalam Bubbling
Fluidized Bed Combustor (BFBC)
Fransisko Pandiangan, Tri Agung Rohmat, Purnomo ................................................... 6
3. Perambatan Gelombang Detonasi Campuran Stoikiometris LPG-Oksigen
di Belakang Model Media Porous dengan Variasi Massa
Jayan Sentanuhady, Jannati Adnin Tuasikal ................................................................. 11
4. Studi Eksperimental Kestabilan Api Difusi Biogas pada Counterflow
Burner Configuration
Mega Nur Sasongko ..................................................................................................... 17
5. Studi Eksperimental Pengaruh Swirling Intensity terhadap Efisiensi Termal RFM
Swirl Burner
I Made Kartika Dhiputra, Mekro Permana Pinem ......................................................... 23
6. Simulasi CFD untuk Mengetahui Pengaruh Penambahan Batu Bara
Jenis Medium Rank Coal pada Boiler Jenis Low Rank Coal
di Power Plant PLTU Suralaya Unit 8
Nur Ikwan, Giri Nugroho, Wawan Aries Widodo .......................................................... 28
7. Pengaruh hot-EGR dan cooled-EGR Terhadap Daya Mesin Dan Emisi Jelaga
(Soot) Pada Mesin Diesel Direct Injection (DI) Dengan Menggunakan
Bahan Bakar Campuran Biosolar-Jatropha-High Purity Methanol (HPM)
Sobri, Syaiful ................................................................................................................ 33

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8. Pengaruh Tinggi Bed Terhadap Kecepatan Minimum Fluidisasi dan Distribusi

Temperatur Dalam Fluidized Bed Combustor
Kevin Kristiantana, Tri Agung Rohmat, Purnomo ......................................................... 39

B. Energy and Renewable Energy

9. Thermoelectric sebagai Heat Collector untuk Meningkatkan Efisiensi Photovoltaic
pada Daerah Tropis
Andhita Mustikaningtyas, Sindu Daniarta, Yollanda Zilviana Devi ............................... 45
10. Panas Bumi Sebagai Energi Masa Depan Dan Terbarukan Sumatera Barat
Armila .......................................................................................................................... 50
11. Studi Eksperimental Optimasi Campuran Metanol (96%) Etanol (10%) sebagai
Bahan Bakar Alternatif Terbarukan Pengganti Minyak Tanah
Jarot Hari Astanto, Dwi Aris Himawanto, D.Danardono Dwi Prija T ............................ 61
12. Analisis Resistivitas Daerah Geothermal T Berdasarkan Hasil Inversi Finite
Element Data 2D Magnetotelurik
Nur Rachmaningtias, Agus Setyawan, Imam Baru Raharjo ........................................... 67
13. Sistem Irigasi Buatan dengan Photovoltaic dan Thermoelectric untuk
Meningkatkan Pertanian di Indonesia
Pandhu Picahyo, Sindu Daniarta, Galih Pambudi .......................................................... 70
14. Microhydro Power Plant Pest As Energy Source Electromagnetic Wave
Technology With Environmentally Friendly
Syahrial Shaddiq, Dery Januarizki, Gunawan Eka Prasetyo, Ismail Mukti, Fikriyan,
Fajar Al Farobi, Ramadoni Syahputra ........................................................................... 75

C. Fluid Mechanics
15. Pengaruh Penambahan Inlet Disturbance Body Terhadap Karakteristik Aliran
Melintasi Silinder Sirkular Tersusun Tandem
Aida Annisa Amin Daman, Wawan Aries Widodo ........................................................ 79
16. Analisis Numerik Karakteristik Pressure Drop pada Instalasi Sistem Pneumatik
menggunakan CFD
Amam Fachrur Rozie, Yuda Trimardana, Sumadi, Ahmad Indra Siswantara ................ 85
17. Studi Komparasi Jumlah Sudu Turbin pada Rancangan PLTMH Head Rendah
dengan Daya 2Kw
Budi Triyono, Haryadi dan Sugianto ............................................................................ 93

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18. Analisis Eksperimental dan Simulasi Numerik Karaktristik Aliran Fluida

melalui Silinder Persegi dan Segitiga
H. Nasaruddin Salam, Muh. Noor Umar, Ibnu Sidig ...................................................... 98
19. Studi Eksperimen tentang Karakteristik Tekanan dan Kemungkinan Kavitasi
Aliran Fluida melalui Katup Kupu-Kupu
Muh. Hasbi, Sutardi ...................................................................................................... 105
20. Simulasi Numerik Aliran di Sekitar Circular Cylinder dengan Dua Square
Cylinder sebagai Disturbance Body pada Saluran Sempit
Rina, Wawan Aries Widodo .......................................................................................... 111
21. Analisis Penurunan Tekanan pada Instalasi Sistem Hidrolik Alat Uji Tarik
menggunakan CFD di Laboraturium Fenomena Mesin UIKA Bogor
Rio Adika Cahya, Hady Hidayat, Sumadi1, Edi Sutoyo ................................................. 117
22. Studi Parametrik Pengaruh Roughness Terhadap Profil Kecepatan Lapisan
Batas pada Simulasi Atmospheric Boundary Layer di Wind Tunnel
Subagyo ....................................................................................................................... 125
23. Simulasi Numerik Aliran Internal Muffler Kendaraan 2D
Subagyo ....................................................................................................................... 134
24. Aplikasi Reliability Centred Maintenance (RCM) pada Sistem Pemipaan Industri
Kertas yang Beroperasi Kontinyu
Sumadi.......................................................................................................................... 138
25. Analisa Instalasi Sistem Pneumatik untuk Air Service di Laboratorium Proses
Produksi
Wahyu Nuri. Sumadi .................................................................................................... 145

D. Heat Mass Transfer

26. Kinerja Termal Green Roof sebagai Pendingin Pasif di Iklim Tropis
Nandy Putra, Wayan Nata Septiadi, Bambang Ariantara, Retsa Anugrah Menteng .....

151

27. Alat Uji Sirkulasi Air Akibat Efek Thermosyphon pada Sistem Pemanas
Air Surya
Caturwati NK, Ipick S, Alief ........................................................................................ 157
28. Proses Pembuatan Membran Silika MCM-41untuk Alat Penukar Kalor Udara
Hens Saputra, Murbantan Tandirerung, Hananto Widoyoko ......................................... 162
29. Fenomena Pendidihan dan Dinamika Gelembung dari Porous Graphite Foams
Indro Pranoto ............................................................................................................... 168

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30. Aplikasi Heat Pipe pada Thermoelectric Generator

Rio Wirawan, M. Hadi Kusuma, Ranggi Sahmura, Wayan Nata Septiadi,
Nandy Putra ................................................................................................................. 174
31. Efek Orientasi Sudut Delta-Winglet Vortex Generator Terhadap Performa
Termal dan Hidrodinamik Penukar Kalor Jenis Fin-Tube dengan Susunan
Pipa Sejajar Untuk Aplikasi EGR Cooler
Syaiful dan Rahmat Purnomojati ................................................................................. 180
32. Penentuan Sudut Kontak dengan Pengolahan Citra
Windy Hermawan Mitrakusuma, Deendarlianto, Syamsul Kamal, M. Nuryadi,
Rudi Rustandi .............................................................................................................. 186

E. Internal Combustion Engines

33. Efek Campuran High Purity Methanol (HPM) Diesel dan Sistem Cooled EGR
terhadap Smoke Opacity dan Brake Specific Fuel Consumption (BSFC) pada
Mesin Diesel Injeksi Langsung
Aa Setiawan, Syaiful .................................................................................................... 191
34. Karakteristik Pelumas Campuran Zinc Oxide Nanopowder untuk Kendaraan
Agung Sudrajad, Aditya Yuda Anggara ........................................................................ 196
35. Efek High Purity Methanol (HPM) dan Hot EGR terhadap Brake Spesific Fuel
Consumption (BSFC) dan Emisi Jelaga pada Mesin Diesel Injeksi Langsung
Angga Septiyanto, Syaiful ............................................................................................ 200
36. Pengaruh Diameter Exhaust Valve terhadap Unjuk Kerja dan Emisi Gas Motor
Bensin 4 Langkah
Slamet Wahyudi, Lilis Yulianti, Hastono Wijaya dan Alfian Kusuma ........................... 206

F. Multiphase Flow
37. Quantitative Visualization of the Wave Characteristics for Horizontal
Co-Current Gas-Liquid Plug Two-Phase Flow by Using an Image Processing
Technique
Akmal Irfan Majid, Okto Dinaryanto, Deendarlianto, Indarto ........................................ 212
38. Experimental Study on the Liquid Holdup Characteristics of Air-Water
Horizontal Stratified Flow by Using an Image Processing Technique
Hadiyan Yusuf Kuntoro, Deendarlianto ........................................................................ 218

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39. Visualisasi dan Signal Processing Aliran Slug Air-Udara Berdasarkan

Karakteristik Lokal Pada Pipa Horisontal
Yuli Purwanto, Indarto, Khasani, Deendarlianto ........................................................... 224

G. Thermodynamics
40. Analisis Performa Organic Rankine Cycles Berdasarkan Data Pengujian
Evaporator dengan Menggunakan Solar Panel Plat Datar untuk
Fluida Kerja R22 dan R134a
Edi Marzuki, Seftian Haryadi, Yogi Sirodz Gaoz, Mulya Juarsa,
Muhamad Yulianto ....................................................................................................... 230
41. Analisa Pengaruh Variasi Kecepatan Aliran Udara pada Evaporator
Terhadap Performansi Mesin Refrigerasi Kompresi Uap Air Conditioner
dengan Refrigeran R134a
Mahendra, Hendradinata .............................................................................................. 236
42. Analisis Performa ORC dengan Fluida Kerja R-134a Menggunakan Simulasi
Komputer Berdasarkan Data Eksperimental Variasi Laju Aliran Massa Air di
Kolektor Termal-Surya tipe Plat Datar
Mulya Juarsa, Seftian Haryadi, Muhamad Yulianto, Edi Marzuki, Yogi Sirods Gaos .... 241
43. Studi Simulasi pada Ventilasi, Kualitas Udara Interior dan Konsumsi Energi
Ozkar F. Homzah, Haryanto ......................................................................................... 246
44. Kaji Eksperimental Kinerja Mesin Pendingin Kompresi Uap (Freezer) terhadap
Variasi Massa Refrigeran Hidrokarbon Jenis Propan sebagai Pengganti R-22
Tandi Sutandi, Berkah Fajar ......................................................................................... 251

A. Multiphase Flow

Proceeding
Seminar Nasional Thermofluid VI
Yogyakarta, 29 April 2014

Quantitative Visualization of the Wave Characteristics

for Horizontal Co-Current Gas-Liquid Plug Two-Phase Flow
by Using an Image Processing Technique
1

Akmal Irfan Majid*1, Okto Dinaryanto2, Deendarlianto3, Indarto3

Master Program (Fast-track) in Mechanical Engineering, Dept. of Mechanical and Industrial Engineering,
Faculty of Engineering, Universitas Gadjah Mada, Jalan Grafika 2 Kampus UGM Yogyakarta 55281
2
Doctoral Program in Mechanical Engineering, Dept. of Mechanical and Industrial Engineering, Faculty of
Engineering, Universitas Gadjah Mada, Jalan Grafika 2 Kampus UGM Yogyakarta 55281
3
Dept. of Mechanical and Industrial Engineering, Faculty of Engineering, Universitas Gadjah Mada,
Jalan Grafika 2 Kampus UGM Yogyakarta 55281
E-mail: akmalirfanmajid@mail.ugm.ac,id

Abstract
Gas-liquid plug flow, as a part of the intermittent flow, has received more attention as the initiation of the
slugging phenomena in fluid transportation. This pattern has particular characteristics such as the large
pressure fluctuation, irregularity, and intermittency which possible to lead the internal pipe corrosion and
the pipe blasting. The presence of the large amplitude waves can be generated since gas flows with high
slip velocity through the liquid-phase. Due to that reason, pipe blockage phenomenon can be occurred.
The purpose of the present experimental study is to conduct a better understanding on the wave
characteristics of air-water co-current plug two-phase flow by using an advanced visualization method
named image processing technique.
The novel technique has been applied to elucidate quantitative result of liquid-phase level by analyzing
sequence of recorded images. Water and pressurized air flowed co-currently inside the horizontal acrylic
pipe with 26 mm internal diameters. A high-speed video camera (640 x 480 pixels; 120 frame per seconds)
was used to visualize the pattern. Those observed images were converted from RGB into binary mode by
image segmentation operation by using MATLAB. In order to improve the images quality, several image
filtering types including Median and Wiener filtering were utilized. Moreover, the non-linear statistics
analysis such as cross-correlation function, power spectra density, and probability distribution function
were implemented to obtain the quantitative information. Here, the wave characteristics such as wave
velocity and wave frequency are determined. It reveals the information of plug flow liquid hold up
distribution. It can be inferred that the wave characteristics in a horizontal gas-liquid plug flow are strongly
affected by gas and liquid superficial velocities. Furthermore, the data can be potentially used to investigate
the plug flow mechanism in horizontal pipe, even to validate the CFD codes.
Keywords: Visualization studies, Plug flow, Wave characteristics, Image processing technique, Interfacial
behavior

1.

Introduction
The gas-liquid plug and slug flow has been
investigated since couple years ago due to its standout
characteristics of high pressure fluctuation, random,
irregular motion, and large amplitude waves.
Specifically, the initiation of slugging is classified into
hydrodynamic and terrain slugging. Hydrodynamic
slugging is caused by a flow disturbance to the gas
liquid interface in a stratified flow close to the pipeline
entrance region. A small wave forms on the interface
and grows to block the pipe cross section, forming a
slug [1]. Terrain slugging results from liquid
accumulation in local dips of flow lines with variable
topography [2]. The occurrence of the flow
intermittency inflicts these patterns to be commonly
avoided in related safety issues, pipe erosion, and

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design of the pipeline and pumping system, especially

in offshore, boiling industries, nuclear reactors, and
fluid lines.
Particularly, plug flow takes part as the initiation
of highly-turbulent slug flow. By increasing liquid
flow rates, plug flow is considered as a transition from
stratified into slug flow in a low gas velocity [3, 4].
Under the rise of liquid level, the waves are formed
and tend to block the pipe cross-sectional area.
Otherwise, the gas velocity, liquid Froude number,
and the bridging location influence the air-water slug
initiation and its frequency [5]. However, this model
has a contradiction with one-dimensional two-fluid
model of Taitel and Dukler [6] which conducted that
slug is initiated by a long wavelength disturbances in a
stratified layer until the waves grow to block the pipe
[2]. A different criteria and definition on the onset of

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Proceeding
Seminar Nasional Thermofluid VI
Yogyakarta, 29 April 2014

slugging was also occurred. For all those studies, there

is no deal which confirms an absolute concept on the
plug and slug formation. On the other hand, it is
agreed that a slug initiation process is basically
occurred when the wave characteristics are changed.
Those facts lead the strong reasons to build up a good
understanding on the unique plug flow wave
characteristics to support the systematical data on the
slugging mechanisms.
Various methods have been proposed in order to
determine the interfacial behavior of this regime. For
instances, the use of wire mesh sensor [7] which has a
shortage of its intrusive characteristics. The other
techniques such as the capacitance sensor [8] and
Constant Electric Current Method (CECM) signal
processing [9] were also used to obtain time-series
data. Nevertheless, for a few case, those methods
could only be applied in a specific condition.
Consequently, the different results between those
specified methods are ensued due to the diverse
measurement technique. Moreover, the visualization
methods are used to conduct a profound observation
on the flow behavior. However, the method were
previously used as the escort study to support the
obtained results from the other measuring devices. In
the previous work, this method just applied for
assigning the flow pattern [10, 11]. Thus, the
qualitative data are only performed through this case.
Recently, the visual studies is continued to grow
in the field of advanced visualization methods. The
CFD codes [12] have been already applied. A more
accurate result is expected due to the implementation

only a few studies addressing a comprehensive data

including the flow topology and the important wave
parameters for the plug flow in a horizontal pipe.
Specifically, Mayor et al. [13] conducted an image
processing technique for vertical slug flow while
Amaral et al. [14] applied a different algorithm
(watershed and H-minima) for determining slug flow
topology. In this present work, a simple algorithm
based on noise reduction and image segmentation was
developed to obtain both the gas-liquid plug flow
topologies and the quantitative evaluation of the wave
parameters. The purpose of this present study are to
obtain a better understanding on the interfacial
analysis of gas-liquid plug flow in a horizontal pipe.
The available previous studies were also compared
with the obtained data of this present work.
2.

Experimental Methods
Experiments were performed at the horizontal
two-phase flow test facility of the Fluid Mechanics
Laboratory, Department of Mechanical and Industrial
Engineering, Gadjah Mada University. It consists of
26-mm inner diameter of transparent acrylic pipe
with 9.5-m total length. Air and water were used as
working fluid. The present work was an adiabatically
work which carried out under atmospheric pressure
and room temperature. A depth visual observation of
the gas-liquid flow behavior was conducted by a
high-speed video camera with resolution of 640-pixel
width and 480-pixel height. The camera has rates of
120 frame per second (fps). A rectangular correction
box was used to reduce the image distortion due to

of those methods. However, the shortcomings of the

the different refraction index. The 1.2-m length of
Experimental
apparatus
PIV and X-Ray tomography application areFig.
the1.facts
transparent
box was filled by water which has close
that they need a complicated installation and advanced
value of acrylic reflective index. About 1-m length of
post-data processing. Else, by using CFD codes, a
the visualization test area was positioned in around 7number of parameters such as the boundary condition,
m from the initial pipe to ensure fully developed
meshing criteria, and exact flow parameters should be
flow. A schematic layout of the experimental
well prepared. On the other hand, an image processing
apparatus is briefly represented in Fig. 1 above.
technique is appropriate to be implemented in the
This present work is involving 25 experimental
interfacial analysis due to its simplicity, accuracy, and
data which covers the liquid superficial velocity (JL)
easy to be used. The non-intrusive method has an
from 0.25 to 1.13 m/s and that of gas superficial
ability to establish both of the qualitative and the
velocity (JG) from 0.12 to 0.51 m/s. The experimental
quantitative assessment.
data range is presented in Fig. 2 in the form of coAlthough this technique has been previously
current horizontal flow pattern maps comparison
applied for investigating slug flow characteristics,
among Mandhane et al. (1974), Taitel & Dukler

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Proceeding
Seminar Nasional Thermofluid VI
Yogyakarta, 29 April 2014

(1976), Weismann et al. (1978), and Lin & Hanratty

(1987). All observed data meet the appropriate plug
regime that proposed by these maps.
The physical experiments and investigation on
the liquid hold-up by using CECM (Constant Electric
Current Method) have also been conducted [15, 16].
Three pairs of liquid hold-up sensors are located in
215-mm spacing line between each sensors. The
available results of the signal processing experiment
were used as data comparison of the plug flow wave
characteristics.

Fig. 2. Flow pattern maps comparison

3.

Image Processing Technique

Each obtained video was extracted into
sequences of images. Through the Virtual Dub
software, a video was splatted into the consecutive
images. This operation produces 3600 image frames
from each 30-seconds video. A specific algorithm
which aimed to measure liquid-phase level was
developed in MATLAB R2013a. Particularly, this
engineering software was commonly used in digital
image processing application by providing the friendly
features in Image Processing Toolbox.
Each of digital image was treated as matrix data
(row and column processing) in pixel unit. This work
was used the thresholding method of image
segmentation to make the binary images to find binary
image. Thus, a statistical analysis support the data
analysis for example to find the liquid hold-up
distribution and wave frequency.
The algorithm was started by loading the
extracted images. At the first, those images were in
form of 8-bits RGB (red-green-blue). Due to the
imperfection in capturing the images, an inappropriate
orientation of the loaded images often occurs. An
image rotation should be obtained to reach the best
image orientation. This step is aimed to ensure best
input for the next operation steps.
The 3-layers RGB images need to convert into 1layer grayscale images. As the results, the output
images have 256 grey level index ranging from 0
(black) to 255 (white) pixel. The use of MATLAB
command of rgb2gray allow the easiest way for the
grayscale conversion by eliminating the hue and
saturation information while retaining the luminance
[17]. Those images were then cropped into desired
size depend on the essential informations. Next, in

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order to eliminate the image noise, sequence

operations were performed. The noise reduction
process was begun with the image complementary
operation (Fig. 3b) which underlies the next step of
the artificial backgrounds construction. They were
prepared after a combination with non-flat structuring
element function for ensuring more uniform
luminosity level. After that, a subtraction between the
grayscale complement images and the new
backgrounds was undertaken (Fig. 3c). Moreover,
Median filtering and Wiener Filtering were
implemented to reduce the different types of image
noise. Each output pixel is determined by the median
value of the neighborhood pixels for Median Filtering
while Wiener filtering is a type of linear filtering
which worked adaptively into the images by tailoring
itself to the local image variance [17]. Result of image
filtering operation is presented as well in Fig. 3d.
One of the significant steps in image processing
technique is image segmentation which covers the
binary images conversion (thresholding). A threshold
value corresponds to change the pixel value to be 1
(white) for higher value and 0 (black) for lower
value than threshold value. Due to random and
irregular characteristics in this flow pattern, the
threshold value needs to be determined manually
rather than automatic graytresh method (Otsus
method). Hence, the binary images were performed
(Fig. 3e). Through the bwperim function, the binary
image perimeter (Fig. 3f) can be performed. The
command help encourage an improvement on the
apparent gas-liquid interfacial boundary.

Fig. 3. The following steps of image processing

operation: (A) Result of cropped image (B) result of
image complementary (C) after background
subtraction (D) after image filtering (E) after
conversion to binary mode (F) result of image
perimeter. (JG=0.24 m/s and JL=0.77 m/s)
A quantitative analysis which combined of the
non-linear statistics such as cross-correlation function,
power spectral density (PSD), and Probability
distribution function were involved to analyze this
phenomena. A local analysis was adapted to determine
liquid film thickness by dividing each image frame
into three selected zones (Fig. 4). Each divided zone
has 1-pixel column width. The object tracking
algorithm ensured the obtainment of the lowest point

ISSN 2355 6927

Proceeding
Seminar Nasional Thermofluid VI
Yogyakarta, 29 April 2014

white object (gas-plug). The liquid film thickness ()

could be obtained by this following equation:
(1)
[( h 1) t G ] calibratio n (mm)
where h is the column height (pipe diameter), tG is the
gas-phase thickness, and the calculation was calibrated
from pixel to mm unit.

Fig 4. Illustration of the image division (160th, 320th,

480th column) and liquid film thickness measurement
4. Results and Discussion
4.1 Flow Pattern
Plug flow pattern is characterized by the
presence of the elongated bubble that located in
upper layer of the pipe. This pattern consist of liquidplug and gas-plugs (often recognized as Taylor
bubble or elongated bubble) without any tiny aerated
bubbles behind the gas-plug. Specifically, for the
horizontal flow, the gas-phase (very low-density
phase) took place at the top of the pipe whereas
liquid phase at the bottom of it due to the gravity
effect. Image processing technique was decisively
recognized the important flow parameters, bubblecontours, and the boundary among gas and liquid
through image segmentation operation.

Fig. 6. Comparison among the image processing result

CFD codes and visual observation
(JG=0.12 m/s and JL=0.25 m/s)
4.2 Liquid hold-up characteristics
The measurement of liquid film thickness brings
on the calculation of the liquid hold-up. Basically,
the obtained data at the 2nd zone (x/L = 0.5) of local
analysis (that showed in fig. 4) was chosen due to the
best object condition. However, the observation just
produced one-dimensional side-view data that should
be converted into 3-D liquid hold-up which involves
the cross-sectional analysis. Those following
assumptions has been used by Majid [20] to solve the
same problem.
As shown in fig. 7, the waves are periodically
fluctuated by showing high values (for liquid-plug)
and low values (for gas-plug). In this case, the gas
movement was hampered because the liquid film
always tended to block the pipe. Meanwhile, the
pressure drop in this regime was also in the chaotic
condition.

Fig. 7. Typical transient liquid hold-up data

(for JG=0.12 m/s and JL=0.31 m/s)

Fig. 5. Comparison among the obtained visualization result

from photograph view and image processing
The comparison of single elongated bubble
topology which observed by visual study and image
processing technique is suitably illustrated in Fig. 5.
It can be seen that the image processing results
perform a better interface for the bubble nose and tail
contours. Therefore, this technique can be potentially
used to validate the CFD codes. A comparison with
the previous visual observation [18] and CFD codes
[19] are also depicted in Fig. 6.

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215

Fig. 8. The effect of gas superficial velocities

on the average liquid hold-up
Fig. 8 is revealed that the average liquid hold-up
decreases as the increase of gas superficial velocities.
In a constant duct, the increase of JG was also
contribute to increase the gas volume flow rate.
Therefore, the liquid film was shoved by the presence
of gas-phase. Thus, the liquid hold-up value
decreased. The non-linear statistics such as PSD and
PDF conclude the liquid hold-up frequency and
distribution. As can be seen in Fig. 9, the gas-liquid
plug flow has twin peaks of liquid hold-up distribution
in PDF calculation. They are liquid dominant zone

ISSN 2355 6927

Proceeding
Seminar Nasional Thermofluid VI
Yogyakarta, 29 April 2014

(which has =1) and the else for gas dominant zone.
The PSD data leads the wave frequency calculation.

Fig. 9. Example of (a) PSD and (b) PDF analysis

(JG=0.51 m/s and JL=1.13 m/s)
4.3 Wave Velocity
The wave velocity data was obtained by the
cross correlation function. The measurement used
two waves which obtained from the 160th column
pixel (x/L = 0.25) and the 480th column pixel (x/L =
0.75) of each image frame. The wave velocity can be
calculated through this following equation:
Wave velocity =

(m/s)

(2)

An image processing technique shows a good

performance in the wave velocity measurement. The
wave velocity data comparison is shown in Fig. 10.
The present data are well agree with the previous
studies such as CECM Measurement [15] and bubble
translational analysis [18]. The data is also compared
with the drift-flux model [21], which use the Eq. (3),
as follows:
Ug = C0 Jm + vgj
(3)

Fig. 11. The effect of (a) JG and (b) JL

on the wave velocity
4.4 Wave Frequency
The PSD analysis which based on Fast Fourier
Transform (FFT) produces the exact wave frequency
for each matrix data. The influence of liquid
superficial velocity (JL) through the wave frequency is
shown in Fig. 12. Under the constant JG, the wave
frequency increases as the increase of JL. For high
liquid flow rates, a high wave frequency also
occurred. For instances, the wave frequency can be
obtained as the plug frequency. This term also refers
to the frequency of waves that pass a specific
reference point.

where C0 = 0.98 and vgj = 0.16, for plug flow.

Fig. 10. Relationship between the available previous

studies and averaged wave velocity
The increase of JG and JL induced the less lags
time between two waves. It has a meaning that these
variables give a significant contribution in wave
velocity enhancement. Moreover, by increasing JG in
constant JL and vice versa, the increase of the wave
velocities was also occurred. Fig 11 (a) and (b) depict
the effect of JG and JL on the increase of wave
velocities, respectively.

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216

Fig. 12. Relationship between the liquid superficial

velocity and the wave frequency
5.

Conclusion
An image processing technique was used to
determine the wave characteristics of horizontal cocurrent gas-liquid plug flow. The method has an
ability both for qualitatively ensuring a better point of
air-water interface and proceeding detailed
quantitative results on the important wave parameters.
As the results, an apparent flow pattern, the liquid
hold-up characteristics and distributions, the wave
velocity, and the wave frequency could be
automatically determined through this technique.

ISSN 2355 6927

Proceeding
Seminar Nasional Thermofluid VI
Yogyakarta, 29 April 2014

A specific study was conducted that the gas and

liquid superficial velocity strongly affected the wave
characteristics. The results are summarized as follows:
1. Under a constant JG, wave frequency increases
with increase of JL
2. Under a constant JL, liquid film thickness and
liquid hold-up decrease as the increase of JG.
3. Under the increase of JG and JL wave velocity
is also increased.
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Acknowledgement
The authors gratefully thanks to Directorate General
of Higher Education, Ministry of Education and
Culture, Republic of Indonesia for supporting this
present work as a part of the Hibah Penelitian
Unggulan Perguruan Tinggi research scheme through
Dana DIPA Universitas Gadjah Mada 2013 with the
contract
number:
LPPM-UGM/1448/LIT/2013.

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