Icmeam abstract book

ii

INTERNATIONAL CONFERENCE ON

MECHANICAL ENGINEERING

&

ADVANCED MATERIAL

2015

3rd– 4th DECEMBER 2015

KOTA KINABALU, SABAH, MALAYSIA

iii

TABLE OF CONTENTS

Page

THERMAL & ENVIRONMENTAL ENGINEERING

ICME AM

15011

Methods of Measuring the Remaining Lifetime and Evaluating the Thermal Condition of TBC

Kyoung Sup. Kum & Young Ze. Lee (Invited Paper) 1

ICME AM

15032

Modelling Phase Change Material for Concentrating Energy Storage in Solar Thermal Cooking Stoves

Ang Chan Mun, Ftwi Y. Hagos, Rizalman Mamat, Ahmed Nurye Umer & W. H. Azmi 4

ICME AM

15053

Effect of level of Expansion and Inertia Level in a Suddenly Expanded Flow Zakir Ilahi Chaudhary , V. B. Shinde , Syed Ashfaq & S.A. Khan

12

ICME AM

15009

Self-Start Performance of a Variable Pitch Mechanism for Vertical Axis Wind Turbine

Chua BihLii, Tan May Chan, Mohd. Suffian Misaran & Md. Mizanur Rahman 19

ICME AM

15030

Experimental Study of Aerodynamic Characteristics of Airfoils Using Hexagonal Shaped Dimples

Mohammad Mashud & Rubiat Mustak 23

ICME AM

15028

Experimental Investigation of Greenhouse Solar Dryer with Separate Chimney for Seaweed Drying

Hooi-Kim Phang, Chi-Ming Chu, Sivakumar Kumaresan, Md. Mizanur Rahman, Suhaimi Md. Yasir 28

ICME AM

15052

Combined Effect of Nozzle Pressure Ratio and Screech Prone Supersonic Mac Number in a Suddenly Expanded Flow

Musavir Bashir , Parvathy Rajendran & S A Khan 34

ICME AM

15008

Experimental Optimization of Single Slope Solar Still Using Seawater Ong Cheah Meng, Yeo Kiam Beng & Kenneth Teo Tze Kin

42

ICME AM

15080

Numerical Study on Solar Chimney for Natural Ventilation

Ling Leh Sung, Md. Mizanur Rahman & Mohd. Suffian Bin Misaran 48

ICME AM

15081

Heat Removal Capacity of Earth-Air Heat Exchanger Under Laboratory Condition Md. Mizanur Rahman, Ling Leh Sung, Fadzlita Mohd. Tamiri & Mohd Suffian Bin Misaran

49

ICME AM

15070

Theoretical and Numerical Methods for Determination of Heat Transfer Behaviour of Single Slope Solar Still

Yeo Kiam Beng & Ong Cheah Meng 52

ICME AM

15043

Finite Element Approach of Bio-heat Transfer and Study of Thermal Burn Injuries Abul Mukid Mohammad Mukaddes, Ryuji Shioya & Sannyal Mridul

53

ICME AM

15040

Influence of Low Length-to-Diameter Ratio and Nozzle Pressure Ratio in an Abruptly Expanded Flow

Zakir Ilahi Chaudhary , V. B. Shinde , Syed Ashfaq & S.A. Khan 60

ICME AM

15004

Cost Optimization of Hybrid Solar, Micro-Hydro and Hydrogen Fuel Cell Using Homer Software

Nader Barsoum & Pearl Dianne Petrus 65

ICME AM

15017

Design and Development of Solar Concentrator Carbon Capture and Electro – Conversion

Ooi Shen Ching, Miron Gakim, Karen Wong Min Jin, Chua Bih Li, Nancy Julius Siambun 72

ICME AM

15035

Equi-Volume Natural Convection Behavior of Chimneys

Chi-Ming Chu, Kar-Heng Neoh & Md. Mizanur Rahman 77

ICME AM

15007

Performance Evaluation of Evaporation Models for Open Ponds in East Malaysian Climate

Md. Ashikur Rahman, Md. Mizanur Rahman, Noor Ajian Mohd. Lair & Chi Ming Chu 83

ICME AM

15001

Performance Investigation on Flat Plate Solar Collector Integrated With Thermal Energy Storage Using Fe-Nanofluid

Afolabi Lukmon Owolabi , Hussein Al-Kayiem , Aklilu Tesfamicheal Baheta 91

ICME AM

15082

Effect of Solar Chimney Angle on Natural Convection Flow Through Abdullah Mohd Tahir , Md. Mizanur Rahman & Ling Leh Sung

92

ICME AM

15083

Hydraulic Efficiency of Vortex Turbine for Different Water Head

Fadzlita Mohd Tamiri, Md. Mizanur Rahman & Abdullah Mohd Tahir 93

ICME AM

15084

Solar Irradiated Ventilation of an Enclosure Pond for Evaporation Processes Md. Mizanur Rahman, Md. Ashikur Rahman, Noor Ajian Mohd Lair & Chi Ming Chu

94

DESIGN & MANUFACTURING

ICME AM

15015

Cutting Theory of Unsupported Brushes using Peripheral Blades

Y.D. Kwon, W.K. Choi, D.H. Kim &H.W. Kwon (Invited Paper) 102

ICME AM

15023

Study on incremental sheet forming and recent development

Young-Suk Kim & Van-Cuong Do (Invited Paper) 106

ICME AM

15034

Static and Dynamic Finite Element Analysis of Negative Pressure HDD Air Slider

Pyung Hwang & Polina V. Khan (Invited Paper) 112

ICME AM

15021

Surface Texturing by Biomachining along with Fine Tuning of Process Parameters for Improved Surface Roughness

Imran Muhammad, Yein, Kwak & Tae Jo, Ko, Hochan Kim (Invited Paper) 118

ICME AM

15022

Surface Texturing on Free Form Surfaces by Grinding Process

Jiyong Jeong, Yu Zhen, Tae Jo Ko, & Hochan Kim 120

ICME AM

15027

Development for Mechanical Expansion Equipment of Tubes to Tubesheet in Nuclear Reactor Vessel Internal(RVI)

Myung-Hyun Kim, Si-Geun Choi, Seock-Sam Kim & Jong-Hyoung Kim 122

ICME AM

15071

Compliant Body Autonomous Biomimetic Thunniform Robotic Fish

Wong Wei Loong, Yeo Kiam Beng & Kenneth Teo Tze Kin 123

iv

ICME AM

15061

Development of Removable Shear Link with Perforated Web for EBFs

Daniel Y. Abebe, Gyumyong Gwak, Meron W. Lemma, Jae Hyouk Choi (Invited Paper) 124

ICME AM

15059

Extrusion Shape Complexity: A Research/Industry Review Sayyad Zahid Qamar (Invited Paper)

127

ICME AM

15038

Colorimetric Sensor based Determination of Allura Red (E129) Using Prussian Blue as a Redox Indicator

Kobun Rovina, Shafiquzzaman Siddiquee & Sharifudin Md Shaarani 130

ICME AM

15049

Spray Drying of Herbal Plant Extract on Synergistic Effect of Mengkudu with Wheat Flour

Duduku Krishnaiah,S.M. Anisuzzaman, Awang Bono & Rozianie Rajak 131

ICME AM

15063

Development and Verification of Hybrid Online Test Process Using Hydraulic Actuator

Jeong Hyun Jang, Ji Sang Jang, Ji Won Park , Jae Hyuk Choi 138

ICME AM

15044

Impact of TQM Implementation on Organizational Performance in an Electronic Company

Rosnah Mohd Yusuff & Melissa Abdul Ghafar 140

ICME AM

15031

Experimental Investigation of Slipstreaming Effect between A Semi Trailer-Truck And A Sedan Car

Mohammad Mashud & Rubiat Mustak 144

ICME AM

15029

Surface Modification Techniques for Wear Minimization Dae-Eun Kim (Invited Paper)

147

ICME AM

15064 Experimental Study on the Hysteresis Characteristics of Buckling Resistance Steel Damper Sijeong Jeong, Gyumyong Gwak, Beomseok Go, Jaehyouk Choi

148

ICME AM

15060

Dynamic Response of Plates Due to Impact Load Nittala Surya Venkata Kameswara Rao, Chong Chee Siang & Bong Kwong Nyap

151

ICME AM

15042

The Effects of Machining Parameters on Product Quality in Dry Turning Operation Noor-Ajian Mohd-Lair, Ahmad-Sad Sahibe, Abdullah Mohd-Tahir, Mohd-Saiyful-Safic Awang & Roonie Protasius

157

ICME AM

15065

Effect of Valve Timing Events on the Performance of Compressed Natural Gas Direct Injection (CNGDI) Engine

Using Simulation

Edilan, M.M., Kalam, M.A., Muhamad Said, M.F.

161

ICME AM

15066

Exploring Potential Local Natural Organic Dye Sensitizers for Photoelectrochemical Cells in Dye Sensitized Solar

Cells (DSSC) Ung Mee Ching, Coswald Stephen Sipaut , Jedol Dayou, Rachel Fran Mansa

167

ICME AM

15057

Assessment of C-type Wind Turbine Performance under Low Wind Speed Condition Mohd Suffian Misaran, Md. Mizanur Rahman, Chua Bih Lii, Eugene Edeberg

168

ICME AM

15054

A Design of Baja Electric Vehicle for 2015 Baja SAE KOREA Competition Yun-Hwa Lee, Soon-ki Lee, Seung-Je Yeom & Pyung Hwang

171

ICME AM

15072

Computational Fluid Dynamics Prediction of Outboard Marine Propeller Flow Under Non-Cavitating And Cavitating

Conditions

Choong Wai Heng, Yeo Kiam Beng

177

ADVANCED MATERIALS

ICME AM 15014

Wear Characteristics of 3D Printed Surfaces with Super-Alloy Dong-Gyu Ahn & Ho-Jin Lee (Invited Paper)

178

ICME AM

15019 Mechanical Properties of Si-Diamond Like Carbon films with Plasma Enhanced Chemical Vapor Deposition

Tae Gyu Kim (Invited Paper) 180

ICME AM 15024

Surface Treatments of Carbon Fibers to Enhance the Interfacial Strength of Thermoplastic Composites

Seung A Song, Seung Jin See, Kang Yeong Choe, Seong Su Kim (Invited Paper) 181

ICME AM

15006 Design of new PET/Polyolefin MFC composites A. Almajid, R. Walter, T. Kroos, H. Junaidi, K. Abdullmawjood & M. Gurka

183

ICME AM

15005 High Temperature Deformation of over Aged 7010 Al Alloy

Abdul Hakim Almajid 188

ICME AM

15013 Re-melting Characteristics of 3D Printed Surfaces by a DED Process Ho-Jin Lee, Dong-In Kim, Dong-Gyu Ahn, & Jin-Seok Kim

194

ICME AM

15073 Impact Behavior of Different Ply Orientation on Unidirectional Glass Fiber Laminated Composite

Mazree Ahamad Bin Mahamood Ahamad, Yeo Kiam Beng 196

ICME AM

15033 Laser Shock Processing of Metal for Enhancement of Surface Properties

Sungho Jeong, Hyun-Taeck Lim, In-Kyu Yeo & Jun-Su Park (Invited Paper) 197

ICME AM

15026 Mechanical Properties and Tribological Characteristics of White Metal Treatment on S45C by Laser Cladding

Si-Geun Choi, Yong-Joong Lee, Seock-Sam Kim, Yong-Sub Jung, Jin-Seok Jang, Ji-Hyun Sung, Yang-Gon Kim, Jae-Wook Lee &

Jong-Hyoung Kim 198

ICME AM

15045 Friction and Wear Characteristics of Polylactic Acid (PLA) for 3D Printing under Reciprocating Condition

Hong Yi, Kwang-Hee Lee & Chul-Hee Lee 199

ICME AM

15050 Carbon Dioxide Capture Using Waste Tire Based Adsorbent

Duduku Krishnaiah, S.M. Anisuzzaman, Awang Bono, Teo Bee Khee, V.V.Basava Rao 204

v

ICME AM

15050 Removal of Chlorinated Phenol from Aqueous Solution Utilizing Activated Carbon Derived from Papaya (carica

papaya) Seeds

Duduku Krishnaiah, Collin G. Joseph, S. M. Anisuzzaman, W. M. A. W. Daud, M. Sundang & Y. C. Leow

211

ICME AM

15037 Indentation Micro Vickers Analysis of Brass Piezoelectric Jumardi Sarifudin, Mohd Kamal Mohd Shah & Sahari Jaapar

220

ICME AM

15048 Properties of Melamine Urea Formaldehyde (MUF) Resin under Various Production Formulation

S.M. Anisuzzaman, Awang Bono, D. Krishnaiah & Aisah Bano 224

ICME AM

15074 Plastic Collapse and Energy Absorption of Empty Tubular Structure Under Transverse Quasi-Static Loading

Muaz Bin Abdul Wahab & Yeo Kiam Beng 234

ICME AM

15075 Plastic Collapse and Energy Absorption of PU-Filled Tubes Under Quasi-Static Loads by Computational Analysis

Woo Wen Tzeng & Yeo Kiam Beng 235

ICME AM 15056

Microstructure, Mechanical and Tribological Properties of Crsicn Coatings in Water Lubrication

Fei Zhou, Zhiwei Wu & Qianzhi Wang (Invited Paper) 236

ICME AM 15062

Free Surface Vortex in Pump Sump With A Curtain Wall

Yun Hai Wang, Yeon Won Lee, Chang Soo Kang (Invited Paper) 246

ICME AM 15003

Wax Extraction and Characterization from Petroleum Fraction

S.M. Anisuzzaman, H.A.R. Rahmaliza & P. Ravindra 248

ICME AM

15018 Investigation on Sustainability of Tin Oxide (SnO2) Anode for Molten Salt

Nancy Julius Siambun, Pang Kien Yeung, Miron Gakim & Abdullah Mohd. Tahir 253

ICME AM

15058 Influence of Water Absorption on Mode I Delamination in Carbon/Epoxy Composite Laminate

K.J. Wong, M. Johar, X.J. Gong, S.Aivazzadeh & M.N. Tamin 254

ICME AM

15075 Self-Healing Polymer: A Review Rosalam Hj. Sarbatly, Yeo Kiam Beng, Awang Bono, Choong Wai Heng & Mazree Ahamad Bin Mahamood Ahamad

264

ICME AM

15076 Fiber Orientation Effect on Unidirectional GFRP Composite: Flexural and Tensile Properties

Noratirah Binti Umar, Nurazizah Binti Bokchua, Yeo Kiam Beng & Choong Wai Heng 270

ICME AM

15077 GFRP Laminate of Unsaturated Polyester Resin Reinforced by Plain-Weave Woven E-Glass Fiber

M. A. Faizal, K. B. Yeo & W. H. Choong 271

ICME AM

15078 Impact Behaviour of Different Ply Orientation of Unidirectional Glass Fibre Laminate

Yeo Kiam Beng, Mazree Ahamad Bin Mahamood Ahamad, Mohd Kamal Mohd Shah, Fadzlita Mohd Tamiri 272

International Conference on Mechanical Engineering and Advanced Material 2015

3-4 December, 2015, Kota Kinabalu, Sabah, Malaysia

34

ICME- AM -ID-1505210

Combined Effect of Nozzle Pressure Ratio and Screech Prone

Supersonic Mach Number in a Suddenly Expanded Flow

Musavir Bashir1, ParvathyRajendran

2,and S.A. Khan

3

1 School of Aerospace Engineering, University Sains Malaysia, Penang, Malaysia. 2 School of Aerospace Engineering, University Sains Malaysia, Penang, Malaysia

3Professor, Department of Mechanical Engineering, Faculty of Engineering, IIUM, Kuala Lumpur, Malaysia

[email protected]

ABSTRACT This paper presents the results of an experimental study to evaluate the effectiveness of the micro jets to control the base

pressure in a suddenly expanded flow at supersonic Mach numbers. Four micro jets of 1mm orifice diameter located at 90°

intervals along a pitch circle diameter of 1.3 times the nozzle exit diameter in the base region were employed as active controls.

The Mach numbers of the present study were 1.8 and 2.0. The jets were expanded suddenly into an axi-symmetric circular tube

with cross-sectional area 2.56, 3.24, 4.84 and 6.25 times that of the nozzle exit area. The Length to Diameter ratio of the

suddenly expanded duct was varied from 10 to 1 and experiment were conducted for Nozzle Pressure Ratio (NPR) from 3 to 11.

Jets were over, under, and correctly expanded depending upon the NPR of the respective runs. When flow from the nozzle was

over expanded or under expanded an oblique shock or expansion fan will be positioned at the nozzle lip, which in turn will

result in increase or decrease of the base pressure. From the results it was observed that at NPRs 3 the control was not effective,

however, at NPR 5, 7, 9, and 11 a significant change in the base pressure for all the area ratios was seen. From the results it was

concluded that the level of expansion, Mach number, length-to-diameter ratio, and area ratio played an important role to fix the

value of the base pressure and the control effectiveness by the micro jets.

Keywords: Base pressure, Active Control, Abrupt Expansion, Nozzle Pressure ratio.

1. Introduction The discipline of “Base Flow Aerodynamics” has

attracteda lot of attention in the past few years. The

examination of base flow behind aerodynamic vehicles

such as missiles, rockets, aircraft bodies and projectiles

as well as re-entry vehicles is essential to understand the

flow separation phenomenon, which leads to the

formation of a low-pressure circulation region near the

base. The interaction between the rocket exhaust, and the

transonic/supersonic external flow deteriorates the

performance of launchers and projectiles, and base flow

is the trigger. Talking about the advanced future nozzle

mechanics, such as the plug nozzle, the performance

becomes more relative to the external flow, and therefore,

the base flow plays even greater role. In order to

comprehend the parameters of the base flow

aerodynamics, more experiments are carried out and new

applications are chosen. In the case of flow separation,

the pressure in this region is usually substantially lower

than the free stream atmospheric pressure. This notable

difference in pressures can be up to two-thirds of the

total drag on the body of revolution at Transonic Mach

numbers. Nevertheless, the base drag at supersonic

speeds is around one-third of the total drag and has

decreased in this stream. Whereas, the base drag is 10

per cent of the skin-friction drag in the sub-sonic flow as

the wave drag will not be there. To further increase of

the base pressure, which decreases the base drag, one

can think of different geometrical modifications, like

boat tails, additional cavities, sting and discs, or

application of base bleed and base combustion. However,

the studies of base drag reduction with active control has

not been studied much, therefore, an attempt has been

made to study the problem with an internal flow. The

experimental study of an internal flow apparatus has a

number of distinct advantages over usual ballistics test

procedures. Huge volume of air supply is required for

tunnels with test-section large enough so that wall

interference, etc., will not disturb flow over the model.

`Stings' and other support mechanism required for

external flow tests are also eliminated in the internal

flows. The most important advantage of an internal flow

apparatus is that complete static pressure and surface

temperature measurements can be made not only along

the entrance section to the expansion(analogous to a

body of the projectile), but also in the wake region These

measurements are particularly valuable if one needs to

test the theoretical prediction adequately.

As stated, numerous techniques have been analyzed

to control the flow separation; hence, base drag shall

either by preventing it or by reducing its effects. Many

researchers have adopted the passive methods like

splitter plate, ribs at the base region of the enlarged duct,

acoustic excitation, step body, locked vortex, but very

few efforts have been made on active control strategies.

Therefore, in the present work, an effort is made to

examine the base pressure manipulation with active

control with the help of micro jets under the effect of

favorable, unfavorable pressure gradient and for ideally



35

expanded cases; at high supersonic Mach numbers with

micro jets.

Fig.1: Sudden expansion flow field

2. Literature Review In base flow aerodynamics, the aerodynamic forces are

mainly loaded by separation over the rear slant, a torus

on the base and two longitudinal vortices created on the

side edges (Ahmed et al. 1984; Spohn and Gillie´ron

2002; Roumeás et al. 2008) [1-3]. The abrupt expansion

of air in a duct results in the base pressure and noise was

studied by Anderson and Williams. When the flow

remains attached, the base pressure showed minimum

value, which depends mainly on the duct to nozzle area

ratio and on the geometry of the nozzle. Various jet flow

models for fuel injection into a combustion chamber and

dispersion of effluents into rivers through a diffuser were

studied by Green 1995[4]. A specific configuration of jet

flow had found applications as a combustion burner in

many industries (Nathan et al. 2006) [5]. Rathakrishnan

and Sreekanth [6] studied flows in pipe with sudden

enlargement. They concluded that the non-dimensional

base pressure was a strong function of the expansion

area ratios, the overall pressure ratios and the duct

length-to-diameter ratios. They showed that for a given

overall pressure ratio and a given area ratio, it was

possible to identify an optimal length-to-diameter ratio

of the enlargement that will result in the maximum exit

plane total pressure at the nozzle exit on the symmetry

axis (i.e. minimum pressure loss in the nozzle) and in a

minimum base pressure at the sudden enlargement plane.

The separation and reattachment seemed to be strongly

dependent on the area ratio of the inlet to enlargement.

For a given nozzle and duct area ratio, the duct length

must exceed a definite minimum value for minimum

base pressure. The effectiveness of passive devices for

axi-symmetric base drag reduction at Mach 2 was

studied by Vishwanath and Patil [7]. The devices

examined included primarily base cavities and ventilated

cavities. Their results indicated that the ventilated

cavities offered significant base drag reduction. They

found a 50 per cent increase in base pressure and 3 to 5

per cent net drag reduction at supersonic Mach numbers

for body of revolution.

The effectiveness of micro jets to control the base

pressure in suddenly expanded axi-symmetric ducts was

studied experimentally by Khan et al. [8]-[15]. From the

experimental results, it was found that the micro jets can

serve as active controllers for the base pressure. From

the wall pressure distribution in the duct it was found

that the micro jets do not disturb the flow field in the

enlarged duct. Ashfaq Syed Ashfaq et al. [16]-[27]

studied the effect of area ratio, nozzle pressure ratio,

length to diameter ratio and control effectiveness for

various area ratios for correctly and under expanded jets.

From their result they found that the control in the form

of the micro jets was very effective. One of the reason

for this behaviour could be due the lowest area ratio, the

space available for the flow to create the suction was the

lowest and the vortex sitting at the base whose strength

was constant was able to influence the base region very

effectively leading to very low level of base pressure and

also the wall pressure was found to be low and

oscillatory in nature. This trend of the wall pressure

having waviness was observed for all the NPRs and

Length to Diameter ratio and it was also observed that

this waviness nature was very strong at the higher NPRs

as compared to the lower NPRs. They presented the

results of experimental studies to control the base

pressure from a convergent nozzle under the influence of

favourable pressures gradient at sonic Mach number.

The area ratio (ratio of area of suddenly expanded duct

to nozzle exit area) studied were2.56, 3.24, 4.84 and 6.25.

It was found that many techniques can be used to reduce

or even suppress two or three dimensional separation.

These techniques include blowing or suction of air flow

through slots (Lehugeur et al. 2010; Wassen and Thiele

2007, 2008; Muminovic et al. 2008) [28-30] or holes

(Favier et al. 2007; Roumeás et al. 2008) [31-32], use of

array(s) of unsteady (synthetic or pulsed) jets (Leclerc

2008), actuators (Boucinha et al. 2008a, b; Moreau

2007) [33-35] and others. All of these techniques come

with pros and cons, as the steady blowing or suction

through orifices normal to freestream flow and located

close downstream of the separation line had been

revealed to be effective in reattaching the flow, but such

devices need a continuous supply of mass flow through

such orifices. In the case of slots, the mass flow rate had

been shown to be very high in order to effect the

requisite control. On the other hand, range of steady

microjets had proven much efficient in comparison to

single slit in terms of the flow rate needed, while being

very effective in controlling the separation. This being

the physical mechanisms behind this ‘discrete’ or

‘segmented’ control differ from the use of (quasi) two-

dimensional or high aspect ratio slots. Steady microjets

act as 3D disturbances, which generate distinct 3D

vertical structures that offer some advantages in terms of

mixing and re-energizing the separating boundary layer.

To date, separation control using microjets had primarily

been examined in canonical flows such as a modified

backward facing ramp (Kumar and Alvi 2006, 2009)

[36-37] and for aircraft-related applications for two-



36

dimensional (at least geometrically) airfoils (Bourgois et

al. 2005; Favier et al. 2007; Kreth et al. 2010) [38-40].

In this study, we examine the use of microjet based

control in a suddenly expanded axi-symmetric duct,

especially, the aim is to control the base pressure in the

transonic/supersonic regime, which appears to be very

promising. We will evaluate the microjet efficiency to

reduce the base drag and to gain some insight in the

mechanism behind this approach.

3. Experimental Setup

Fig. 2: Experimental setup

The Fig. 2 shows the experimental setup, which was

used for the present study. At the exit periphery of the

nozzle there were eight holes as shown in the figure, four

of which were (marked c) were used for blowing and the

remaining four (marked m) were used for the base

pressure (Pb) measurement. Control of base pressure was

carried out by blowing through the control holes (c),

using pressure from a settling chamber by employing a

tube connecting the settling chamber and the control

holes (c). Wall pressure taps were provided on the duct

to measure wall pressure distribution. First nine holes

were made at an interval of 3mm each and the remaining

was made at an interval 5mm each. From the literature it

was found that, the typical Length to Diameter (as shown

in Fig. 2) resulting in Pb maximum was usually from 3 to

5 without controls. Since active controls were used in the

present study, Length to Diameter ratios up to 10 had

been employed. For each Mach number, and Length to

Diameter ratios used were 10, 8, 6, 5, 4, 3, 2, and 1 and

for each value of Length to Diameter ratio NPRs used

were 3, 5, 7, 9, and 11.

PSI model 9010 pressure transducer was used for

measuring pressure at the base, the stagnation pressure in

the main settling chamber and the pressure in the control

chamber. It has 16 channels and pressure range was 0-

300 psi. On average 250 samples per second displayed

reading was achieved. The software provided by the

manufacturer was used to interface the transducer with

the computer. The user-friendly menu driven software

acquires data and showed the pressure readings from all

the 16 channels simultaneously in a window type display

on the computer screen. The software can be used to

choose the units of pressure from a list of available units,

perform a re-zero/full calibration, and other transducer

could also facilitate the chosen number of samples to be

averaged, by means of dipswitch settings. It could be

operated in temperatures ranging from -20° to +60°

Celsius and 95 per cent humidity.

4. Results and Discussion

The obtained values consist of base pressure (Pb); wall

static pressure (Pw) along the length of the duct, and the

NPR i.e. stagnation pressure (P0) to back pressure (Patm)

ratio. The obtained pressures were made non-

dimensional by dividing them with the atmospheric

pressure/back pressure. This investigation focus the

attention on the effectiveness of active control in the

form of micro jets, located at the base region of suddenly

expanded axi-symmetric ducts, to modify the base

pressure at supersonic Mach number, which was more

prone to screech. The parameters considered in the

present study were the area ratio of the enlarged duct,

L/D ratio of the suddenly expanded duct, the jet Mach

number and the level of expansion (NPR).

The dependence of base pressure on Mach number,

four area ratios namely 2.56, 3.24, 4.84, and 6.25 for

NPRs from 3 to 11 were given in the Figs. 3((a) to (j)).

Results of the base pressure with and without control

were compared. It was seen from these results that in

supersonic regime the Mach number had a very strong

influence on the base pressure. For a given Mach number

the nozzle pressure ratio (NPR), which dictates the level

of expansion, has a strong role to play on the control

effectiveness of the micro jets. Also, it was seen that

with increase of NPR, the control becomes more

effective in increasing the base pressure for Mach

numbers in the range from 1.8 to 2.0. The physical

reason for this may be the influence of the shock at

nozzle exit, which turns the flow away from the base

region, thereby weakening the vortex positioned at the

base. This results in increase of base pressure since the

weakened vortex at the base encounters the mass flow

injected by the micro-jets. However, NPR11 results in

continuous increase of base pressure compared to the

without control case for the present range of Mach

number tested namely, 1.8 and 2.0. This may be due to

the NPR increases the level of overexpansion decreasing

Hence, the oblique shock at the nozzle exit becomes

weaker than those at lower NPRs. Therefore, the turning

away tendency of incoming flow comes down leaving

the vortex almost intact. At this situation when the micro

jets are introduced they may propagate without any

deflecting tendency, thereby entraining some mass from

the standing vortex and convecting it away from the base

causing the base pressure to assume higher values than

those for without control. It was well known from

literature that passive controls perform better in the

presence of favorable pressure gradient. In the present

study the combined effect of favorable pressure gradient



37

and the relief due to area ratio on the active control

effectiveness is investigated.

The percentage change in base pressure as a function

of length to diameter ratio and area ratio are presented

for NPR =3, 5, 7, 9, and 11.

The NPR range in the present study was such that jet

exiting the nozzle experiences correct, over and under

expansion. It was well known that oblique shock or

expansion fan will be positioned at the nozzle lip for

over and under expanded conditions, respectively. To

understand the influence of level of expansion on the

base pressure with and without control the percentage

change in base pressure variation as a function of Mach

number, L/D and NPR were presented here. The effect

of area ratio with Mach number and NPR being shown in

the Figs. 3 ((a) to (j)). The results for NPR 3 as in the Fig.

3 ((a) to (b)) for Mach numbers 1.8 and 2.0, contain the

base pressure with L/D for over expanded jets. The NPR

required for ideally expanded jets were5.8 and 7.8,

respectively, for Mach 1.8 and 2.0. When the flow was

exiting from the nozzle at NPR 3, the jets were over

expanded and hence, there will be an oblique shock at

the nozzle exit and the shear layer coming out of the

nozzle will be deflected towards the nozzle center line

by the shock. This delayed the reattachment and will

result in a longer reattachment length as compared to a

case without a shock. It was also known that the

reattachment length being a parameter strongly

influencing the base vortex, the increase or decrease of

reattachment length will modify the base pressure. From

the figure it was seen that control effectiveness was only

marginal and the reason for this trend was mainly due to

the level of over expansion.

(a)

(b)

(c)

(d)

Results for NPR = 5 being as shown in the figs. 3 (c) to

(d)). Due to the increase in NPR the level of over

expansion had reduced. In the case of Mach 1.8, this

NPR was very close to become ideally expanded and

there was appreciable gain in the base pressure in the

range from fifteen to twenty percent. This happens only

for lowest area ratio namely 2.56, because of the area

ratio at the micro jets are located at the middle position

ofthe base region. For all the remaining area ratio at



38

Mach 1.8 and 2.0, the effectiveness of the micro jets

were only marginal Fig. 3 ((c) to (d)).

(e)

(f)

Base pressure results for NPR 7 were obtained as in the

Figs. 3(e)-(f) for Mach numbers1.8 and 2. Here, for the

Mach number 1.8, the jet were under expanded and

Mach number 2 are over expanded. Due to the change in

the expansion level, the change in the base pressure

values were observed. For lower area ratios, the increase

in the base pressure is considerable, which was around

twenty five percent and for area ratio 4.84 the micro jets

were not effective. In the results for area ratio 6.25, it

was found that at L/D = 4 for both the Mach numbers,

the jets become quite and the phenomena was observed

by the Anderson and Williams had shown up during this

test, which indicates that the base pressure was having a

minimum value, depends mainly on the duct to nozzle

area ratio and on the geometry of the nozzle. The plot for

the overall noise showed a minimum at a jet pressure

approximately equal to that required producing the

minimum base pressure. We too had also observed this

phenomenon when micro jets were activated, the jets

were silent.

Results for NPR 9 were shown as in the Figs. 3((g)-

(h)). Here both the Mach numbers were under expanded,

there is an expansion fan at the nozzle exit due to

increase in NPR. This expansion fan had a control over

the base pressure depending on the relaxation it enjoys

due to the area ratio effect. From the results it was found

that for all the area ratios the control had become

effective except for area ratio 6.25 where the control

effectiveness was marginal for both Mach numbers. This

observation was in good agreement with those reported

by Ratha Krishnan and Sreekanth [2] for subsonic and

transonic case without control. These results reiterate the

fact that a definite L/D was necessary for the flow to re-

attach after sudden expansion for a given set of

parameters. If the length was less than this minimum

limit, the flow will proceed without re-attaching with the

duct.

(g)

(h)



39

(i)

Results for the NPR 11 being shown as in the fig. 3 ((i)

to (j)). An important point to be observed, that unlike

passive controls the favorable pressure gradient need not

yield the desired results for active control in the form of

micro jets. However, for higher values of the NPRs

namely 11, the active control by micro jets results in

increase of base pressure for all the values of the area

ratios of the present study. It was interesting to note that,

irrespective of the relief due to the area ratio the control

effectiveness was significant at high supersonic Mach

numbers under the influence of favorable pressure

gradient.

(j)

Fig. 3: Percentage change in base pressure with L/D

ratio

It wasevident that increase in relief to the flow simply

indicate that relaxation space existing for the flow was

increasing. This sort of relief will make the

shock/expansion waves at the nozzle lip to spread

relatively more freely with increase of relief at the lip of

nozzle/area ratio.

For lower area ratio, there was significant increase of

base pressure for most of the cases, but it should be

emphasized that some combination of parameters results

in decrease of base pressure when control was employed.

Therefore, one had to identify the proper combination of

parameters to achieve the control of base pressure

resulting in increase or decrease of base pressure

depending on the need of the application. For example,

for base drag reduction one can aim at increasing the

base pressure to a maximum and for mixing

enhancement in the combustion chamber one can aim to

decrease the base pressure to as a low value as possible.

5. Conclusions From the above results, control with the help of micro

jets to control base pressure had been established. The

flow field in the duct remains unaltered when jets were

highly over expanded. With the increase in the NPR, the

control in the form of micro jets becomes for effective

for all NPR > 5 and above. The flow field was

dominated by the presence of the waves both strong as

well as the weak ones. The reflection of the waves from

the wall, recompression and recombination’s are taking

place in the base region as well as partially in the duct

wall, thereby making the flow oscillatory. The micro jets

can be used as effective controllers, increasing the base

suction to appreciable level for some combination of

parameters. The nozzle pressure ratio plays a key role in

deciding the magnitude of base pressure with and

without control, in the high supersonic jet Mach number

regime too.

All the non-dimensional wall pressure values

exhibited in this paper were within an uncertainty band

of ± 2.6%. All the investigation results were within the

range of± 3 per cent.

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Orlando.

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