**Commenced**in January 2007

**Frequency:**Monthly

**Edition:**International

**Paper Count:**310

# Search results for: Bubble pressure

##### 310 Analysis of Impact Load Induced by Ultrasonic Cavitation Bubble Collapse Using Thin Film Pressure Sensors

**Authors:**
Moiz S. Vohra,
Nagalingam Arun Prasanth,
Wei L. Tan,
S. H. Yeo

**Abstract:**

The understanding of generation and collapse of acoustic cavitation bubbles are prerequisites for application of cavitation erosion. Microbubbles generated due to rapid fluctuation of pressure induced by propagation of ultrasonic wave lead to formation of high velocity microjets and or shock waves upon collapse. Due to vast application of ultrasonic, it is important to characterize and understand cavitation collapse pressure under the radiating surface at different conditions. A comparative investigation is carried out to determine impact load and dynamic pressure distribution exerted upon bubble collapse using thin film pressure sensors. Measurements were recorded at different input conditions such as amplitude, stand-off distance, insertion depth of the horn inside the liquid and pulse on-off time of acoustic vibrations. Impact force of 2.97 N is recorded at amplitude of 108 μm and stand-off distance of 1 mm from the sensor film, whereas impulsive force as low as 0.4 N is recorded at amplitude of 12 μm and stand-off distance of 5 mm from the sensor film. The results drawn from the investigation indicated that variety of impact loads can be achieved by controlling generation and collapse of bubbles, making it suitable to use for numerous application.

**Keywords:**
Ultrasonic cavitation,
bubble collapse,
pressure mapping sensor,
impact load.

##### 309 DNS of a Laminar Separation Bubble

**Authors:**
N. K. Singh,
S. Sarkar

**Abstract:**

Direct numerical simulation (DNS) is used to study the evolution of a boundary layer that was laminar initially followed by separation and then reattachment owing to generation of turbulence. This creates a closed region of recirculation, known as the laminar-separation bubble. The present simulation emulates the flow environment encountered in a modern LP turbine blade, where a laminar separation bubble may occur on the suction surface. The unsteady, incompressible three-dimensional (3-D) Navier-Stokes (NS) equations have been solved over a flat plate in the Cartesian coordinates. The adverse pressure gradient, which causes the flow to separate, is created by a boundary condition. The separated shear layer undergoes transition through appearance of ╬ø vortices, stretching of these create longitudinal streaks. Breakdown of the streaks into small and irregular structures makes the flow turbulent downstream.

**Keywords:**
Adverse pressure gradient,
direct numerical simulation,
laminar separation bubble.

##### 308 Role of Acoustic Pressure on the Dynamics of Moving Single-Bubble Sonoluminescence

**Authors:**
Reza Rezaei-Nasirabad,
Zeinab Galavani,
Rasoul Sadighi-Bonabi,
Mohammad Asgarian

**Abstract:**

**Keywords:**
Bubble dynamics,
Equation of the gas state,
Hydrodynamic force,
Moving sonoluminescence.

##### 307 Bubble Point Pressures of CO2+Ethyl Palmitate by a Cubic Equation of State and the Wong-Sandler Mixing Rule

**Authors:**
M. A. Sedghamiz,
S. Raeissi

**Abstract:**

This study presents three different approaches to estimate bubble point pressures for the binary system of CO2 and ethyl palmitate fatty acid ethyl ester. The first method involves the Peng-Robinson (PR) Equation of State (EoS) with the conventional mixing rule of Van der Waals. The second approach involves the PR EOS together with the Wong Sandler (WS) mixing rule, coupled with the UNIQUAC GE model. In order to model the bubble point pressures with this approach, the volume and area parameter for ethyl palmitate were estimated by the Hansen group contribution method. The last method involved the Peng-Robinson, combined with the Wong-Sandler method, but using NRTL as the GE model. Results using the Van der Waals mixing rule clearly indicated that this method has the largest errors among all three methods, with errors in the range of 3.96-6.22%. The PR-WS-UNIQUAC method exhibited small errors, with average absolute deviations between 0.95 to 1.97 percent. The PR-WS-NRTL method led to the least errors, where average absolute deviations ranged between 0.65-1.7%.

**Keywords:**
Bubble pressure,
Gibbs excess energy model,
mixing
rule,
CO2 solubility,
ethyl palmitate.

##### 306 Study of the Particle Size Effect on Bubble Rise Velocities in a Three-Phase Bubble Column

**Authors:**
Weiling Li,
Wenqi Zhong,
Baosheng Jin,
Rui Xiao,
Yong Lu,
Tingting He

**Abstract:**

Experiments were performed in a three-phase bubble column to study variations of bubble rise velocities. The dynamic gas disengagement (DGD) technique and the fast response pressure transducers were utilized to investigate the bubble rise in the column. The superficial gas velocity of large bubbles and small bubbles, the rise velocities of larger and small bubble fractions were studied considering the effect of particle sizes. The results show that the superficial gas velocity associated with large bubbles linearly increase as superficial gas velocity increasing. Particle size has little effect on the both large and small bubble superficial gas velocities. The rise velocities of larger bubble fractions are larger than that of small bubble fractions, and it had different tendency at low and high superficial gas velocities when changing the particle sizes. The rise velocities of small bubble fractions increased and then had a decrease tendency when the particle size became greater.

**Keywords:**
Bubble rise velocity,
gas–liquid–solid,
particle size effect,
three–phase bubble column.

##### 305 CFD simulation of Pressure Drops in Liquid Acquisition Device Channel with Sub-Cooled Oxygen

**Authors:**
David J. Chato,
John B. McQuillen,
Brian J.Motil,
David F. Chao,
Nengli Zhang

**Abstract:**

**Keywords:**
Liquid acquisition devices,
liquid oxygen,
pressure drop,
vortex,
bubble point,
flow rate limitation.

##### 304 Vapor Bubble Dynamics in Upward Subcooled Flow Boiling During Void Evolution

**Authors:**
Rouhollah Ahmadi,
Tatsuya Ueno,
Tomio Okawa

**Abstract:**

**Keywords:**
Subcooled flow boiling,
Bubble dynamics,
Void
fraction,
Sliding bubble.

##### 303 Investigation Bubble Growth and Nucleation Rates during the Pool Boiling Heat Transfer of Distilled Water Using Population Balance Model

**Authors:**
V. Nikkhah Rashidabad,
M. Manteghian,
M. Masoumi,
S. Mousavian

**Abstract:**

In this research, the changes in bubbles diameter and number that may occur due to the change in heat flux of pure water during pool boiling process. For this purpose, test equipment was designed and developed to collect test data. The bubbles were graded using Caliper Screen software. To calculate the growth and nucleation rates of bubbles under different fluxes, population balance model was employed. The results show that the increase in heat flux from q=20 kw/m2 to q= 102 kw/m2 raised the growth and nucleation rates of bubbles.

**Keywords:**
Heat flux,
bubble growth,
bubble nucleation,
population balance model.

##### 302 CFD Simulations to Validate Two and Three Phase Up-flow in Bubble Columns

**Authors:**
Shyam Kumar,
Nannuri Srinivasulu,
Ashok Khanna

**Abstract:**

**Keywords:**
Bubble column,
Computational fluid dynamics,
Gas
holdup profile,
k-ε model.

##### 301 The Effect of Development of Two-Phase Flow Regimes on the Stability of Gas Lift Systems

**Authors:**
Khalid. M. O. Elmabrok,
M. L. Burby,
G. G. Nasr

**Abstract:**

**Keywords:**
Gas lift instability,
bubble forming,
bubble collapsing,
image processing.

##### 300 Investigation of Bubble Growth during Nucleate Boiling Using CFD

**Authors:**
K. Jagannath,
Akhilesh Kotian,
S. S. Sharma,
Achutha Kini U.,
P. R. Prabhu

**Abstract:**

**Keywords:**
Bubble growth,
computational fluid dynamics,
detachment diameter,
terminal velocity.

##### 299 Modeling of the Cavitation by Bubble around a NACA0009 Profile

**Authors:**
L. Hammadi,
D. Boukhaloua

**Abstract:**

In this study, a numerical model was developed to predict cavitation phenomena around a NACA0009 profile. The equations of the Rayleigh-Plesset and modified Rayleigh-Plesset are used to modeling the cavitation by bubble around a NACA0009 profile. The study shows that the distributions of pressures around extrados and intrados of profile for angle of incidence equal zero are the same. The study also shows that the increase in the angle of incidence makes it possible to differentiate the pressures on the intrados and the extrados.

**Keywords:**
Cavitation,
NACA0009 profile,
flow,
pressure coefficient.

##### 298 Evaluation of Exerting Force on the Heating Surface Due to Bubble Ebullition in Subcooled Flow Boiling

**Authors:**
M. R. Nematollahi

**Abstract:**

**Keywords:**
Subcooled boiling,
vibration mechanism,
bubble
behavior.

##### 297 CFD Simulation of Condensing Vapor Bubble using VOF Model

**Authors:**
Seong-Su Jeon,
Seong-Jin Kim,
Goon-Cherl Park

**Abstract:**

In this study, direct numerical simulation for the bubble condensation in the subcooled boiling flow was performed. The main goal was to develop the CFD modeling for the bubble condensation and to evaluate the accuracy of the VOF model with the developed CFD modeling. CFD modeling for the bubble condensation was developed by modeling the source terms in the governing equations of VOF model using UDF. In the modeling, the amount of condensation was determined using the interfacial heat transfer coefficient obtained from the bubble velocity, liquid temperature and bubble diameter every time step. To evaluate the VOF model using the CFD modeling for the bubble condensation, CFD simulation results were compared with SNU experimental results such as bubble volume and shape, interfacial area, bubble diameter and bubble velocity. Simulation results predicted well the behavior of the actual condensing bubble. Therefore, it can be concluded that the VOF model using the CFD modeling for the bubble condensation will be a useful computational fluid dynamics tool for analyzing the behavior of the condensing bubble in a wide range of the subcooled boiling flow.

**Keywords:**
Bubble condensation,
CFD modeling,
Subcooled boiling flow,
VOF model.

##### 296 Bubble Growth in a Two Phase Upward Flow in a Miniature Tube

**Authors:**
R. S. Hassani,
S. Chikh,
L. Tadrist,
S. Radev

**Abstract:**

A bubbly flow in a vertical miniature tube is analyzed theoretically. The liquid and gas phase are co-current flowing upward. The gas phase is injected via a nozzle whose inner diameter is 0.11mm and it is placed on the axis of the tube. A force balance is applied on the bubble at its detachment. The set of governing equations are solved by use of Mathematica software. The bubble diameter and the bubble generation frequency are determined for various inlet phase velocities represented by the inlet mass quality. The results show different behavior of bubble growth and detachment depending on the tube size.

**Keywords:**
Two phase flow,
bubble growth,
minichannel,
generation frequency.

##### 295 Simulation of Ammonia-Water Two Phase Flow in Bubble Pump

**Authors:**
Jemai Rabeb,
Benhmidene Ali,
Hidouri Khaoula,
Chaouachi Bechir

**Abstract:**

The diffusion-absorption refrigeration cycle consists of a generator bubble pump, an absorber, an evaporator and a condenser, and usually operates with ammonia/water/ hydrogen or helium as the working fluid. The aim of this paper is to study the stability problem a bubble pump. In fact instability can caused a reduction of bubble pump efficiency. To achieve this goal, we have simulated the behaviour of two-phase flow in a bubble pump by using a drift flow model. Equations of a drift flow model are formulated in the transitional regime, non-adiabatic condition and thermodynamic equilibrium between the liquid and vapour phases. Equations resolution allowed to define void fraction, and liquid and vapour velocities, as well as pressure and mixing enthalpy. Ammonia-water mixing is used as working fluid, where ammonia mass fraction in the inlet is 0.6. Present simulation is conducted out for a heating flux of 2 kW/m² to 5 kW/m² and bubble pump tube length of 1 m and 2.5 mm of inner diameter. Simulation results reveal oscillations of vapour and liquid velocities along time. Oscillations decrease with time and with heat flux. For sufficient time the steady state is established, it is characterised by constant liquid velocity and void fraction values. However, vapour velocity does not have the same behaviour, it increases for steady state too. On the other hand, pressure drop oscillations are studied.

**Keywords:**
Bubble pump,
drift flow model,
instability,
simulation.

##### 294 Design and Fabrication of Micro-Bubble Oxygenator

**Authors:**
Chiang-Ho Cheng,
An-Shik Yang,
Hong-Yih Cheng

**Abstract:**

This paper applies the MEMS technology to design and fabricate a micro-bubble generator by a piezoelectric actuator. Coupled with a nickel nozzle plate, an annular piezoelectric ceramic was utilized as the primary structure of the generator. In operations, the piezoelectric element deforms transversely under an electric field applied across the thickness of the generator. The surface of the nozzle plate can expand or contract because of the induction of radial strain, resulting in the whole structure to bend, and successively transport oxygen micro-bubbles into the blood flow for enhancing the oxygen content in blood. In the tests, a high magnification microscope and a high speed CCD camera were employed to photograph the time evolution of meniscus shape of gaseous bubbles dispensed from the micro-bubble generator for flow visualization. This investigation thus explored the bubble formation process including the influences of inlet gas pressure along with driving voltage and resonance frequency on the formed bubble extent.

**Keywords:**
Micro-bubble,
nozzle,
oxygenator,
piezoelectric.

##### 293 Measurement of Steady Streaming from an Oscillating Bubble Using Particle Image Velocimetry

**Authors:**
Yongseok Kwon,
Woowon Jeong,
Eunjin Cho,
Sangkug Chung,
Kyehan Rhee

**Abstract:**

Steady streaming flow fields induced by a 500 mm bubble oscillating at 12 kHz were measured using microscopic particle image velocimetry (PIV). The accuracy of velocity measurement using a micro PIV system was checked by comparing the measured velocity fields with the theoretical velocity profiles in fully developed laminar flow. The steady streaming flow velocities were measured in the sagittal plane of the bubble attached on the wall. Measured velocity fields showed upward jet flow with two symmetric counter-rotating vortices, and the maximum streaming velocity was about 12 mm/s, which was within the velocity ranges measured by other researchers. The measured streamlines were compared with the analytical solution, and they also showed a reasonable agreement.

**Keywords:**
Oscillating bubble,
Particle-Image-Velocimetry microstreaming.

##### 292 Pressure Study on Mn Doped KDP System under Hydrostatic Pressure

**Authors:**
W. Paraguassu,
S. Guerini,
C. M. R. Remédios,
P. T. C. Freire

**Abstract:**

High Pressure Raman scattering measurements of KDP:Mn were performed at room temperatures. The X-ray powder diffraction patterns taken at room temperature by Rietveld refinement showed that doped samples of KDP-Mn have the same tetragonal structure of a pure KDP crystal, but with a contraction of the crystalline cell. The behavior of the Raman spectra, in particular the emergence of a new modes at 330 cm-1, indicates that KDP:Mn undergoes a structural phase transition with onset at around 4 GP. First principle density-functional theory (DFT) calculations indicate that tetrahedral rotation with pressure is predominantly around the c crystalline direction. Theoretical results indicates that pressure induced tetrahedral rotations leads to change tetrahedral neighborhood, activating librations/bending modes observed for high pressure phase of KDP:Mn with stronger Raman activity.

**Keywords:**
Dipotassium molybdate,
High pressure,
Raman
scattering,
Phase transition,
ab initio

##### 291 Dynamics of a Vapour Bubble inside a Vertical Rigid Cylinder with a Deposit Rib

**Authors:**
S. Mehran,
S. Rouhi,
F.Rouzbahani,
E. Haghgoo

**Abstract:**

**Keywords:**
Vapour bubble,
Vertical rigid cylinder,
Boundaryelement method.

##### 290 Perfect Plastic Deformation of a Circular Thin Bronze Plate due to the Growth and Collapse of a Vapour Bubble

**Authors:**
M.T. Shervani-Tabar,
M. Rezaee,
E. Madadi Kandjani

**Abstract:**

Dynamics of a vapour bubble generated due to a high local energy input near a circular thin bronze plate in the absence of the buoyancy forces is numerically investigated in this paper. The bubble is generated near a thin bronze plate and during the growth and collapse of the bubble, it deforms the nearby plate. The Boundary Integral Equation Method is employed for numerical simulation of the problem. The fluid is assumed to be incompressible, irrotational and inviscid and the surface tension on the bubble boundary is neglected. Therefore the fluid flow around the vapour bubble can be assumed as a potential flow. Furthermore, the thin bronze plate is assumed to have perfectly plastic behaviour. Results show that the displacement of the circular thin bronze plate has considerable effect on the dynamics of its nearby vapour bubble. It is found that by decreasing the thickness of the thin bronze plate, the growth and collapse rate of the bubble becomes higher and consequently the lifetime of the bubble becomes shorter.

**Keywords:**
Vapour Bubble,
Thin Bronze Plate,
Boundary Integral
Equation Method.

##### 289 Identification of the Main Transition Velocities in a Bubble Column Based on a Modified Shannon Entropy

**Authors:**
Stoyan Nedeltchev,
Markus Schubert

**Abstract:**

*U*

_{G}=0.034 m/s) of the transition flow regime and the beginning (at

*U*

_{G}=0.089 m/s) of the churn-turbulent flow regime. The results were compared with the Kolmogorov entropy (KE) results. A slight discrepancy was found, namely the transition velocities identified by means of the KE were shifted to somewhat higher (0.045 and 0.101 m/s) superficial gas velocities

*U*

_{G}.

**Keywords:**
Bubble column,
gas holdup fluctuations,
Modified Shannon entropy,
Kolmogorov entropy.

##### 288 Entropy Analysis in a Bubble Column Based on Ultrafast X-Ray Tomography Data

**Authors:**
Stoyan Nedeltchev,
Markus Schubert

**Abstract:**

By means of the ultrafast X-ray tomography facility, data were obtained at different superficial gas velocities *U*_{G} in a bubble column (0.1 m in ID) operated with an air-deionized water system at ambient conditions. Raw reconstructed images were treated by both the information entropy (IE) and the reconstruction entropy (RE) algorithms in order to identify the main transition velocities in a bubble column. The IE values exhibited two well-pronounced minima at *U*_{G}=0.025 m/s and *U*_{G}=0.085 m/s identifying the boundaries of the homogeneous, transition and heterogeneous regimes. The RE extracted from the central region of the column’s cross-section exhibited only one characteristic peak at *U*_{G}=0.03 m/s, which was attributed to the transition from the homogeneous to the heterogeneous flow regime. This result implies that the transition regime is non-existent in the core of the column.

**Keywords:**
Bubble column,
ultrafast X-ray tomography,
information entropy,
reconstruction entropy.

##### 287 Process and Supply-Chain Optimization for Testing and Verification of Formation Tester/Pressure-While- Drilling Tools

**Authors:**
Vivek V,
Hafeez Syed,
Darren W Terrell,
Harit Naik,
Halliburton

**Abstract:**

**Keywords:**
Hydraulic Pressure Controller/Calibrator,
M/LWD,
Pressure,
FTWD

##### 286 Mathematical Simulation of Bubble Column Slurry Reactor for Direct Dimethyl Ether Synthesis Process from Syngas

**Authors:**
Zhen Chen,
Haitao Zhang,
Weiyong Ying,
Dingye Fang

**Abstract:**

Based on a global kinetics of direct dimethyl ether (DME) synthesis process from syngas, a steady-state one-dimensional mathematical model for the bubble column slurry reactor (BCSR) has been established. It was built on the assumption of plug flow of gas phase, sedimentation-dispersion model of catalyst grains and isothermal chamber regardless of reaction heats and rates for the design of an industrial scale bubble column slurry reactor. The simulation results indicate that higher pressure and lower temperature were favorable to the increase of CO conversion, DME selectivity, products yield and the height of slurry bed, which has a coincidence with the characteristic of DME synthesis reaction system, and that the height of slurry bed is lessen with the increasing of operation temperature in the range of 220-260℃. CO conversion, the optimal operation conditions in BCSR were proposed.

**Keywords:**
Alcohol/ether fuel,
bubble column slurry reactor,
global kinetics,
mathematical model.

##### 285 A Comparison between Heterogeneous and Homogeneous Gas Flow Model in Slurry Bubble Column Reactor for Direct Synthesis of DME

**Authors:**
Sadegh Papari,
Mohammad Kazemeini,
Moslem Fattahi

**Abstract:**

**Keywords:**
Modelling,
Slurry bubble column,
Dimethyl ether
synthesis,
Homogeneous gas flow,
Heterogeneous gas flow

##### 284 Numerical Simulation of a Single Air Bubble Rising in Water with Various Models of Surface Tension Force

**Authors:**
Afshin Ahmadi Nadooshan,
Ebrahim Shirani

**Abstract:**

Different numerical methods are employed and developed for simulating interfacial flows. A large range of applications belong to this group, e.g. two-phase flows of air bubbles in water or water drops in air. In such problems surface tension effects often play a dominant role. In this paper, various models of surface tension force for interfacial flows, the CSF, CSS, PCIL and SGIP models have been applied to simulate the motion of small air bubbles in water and the results were compared and reviewed. It has been pointed out that by using SGIP or PCIL models, we are able to simulate bubble rise and obtain results in close agreement with the experimental data.

**Keywords:**
Volume-of-Fluid,
Bubble Rising,
SGIP model,
CSS model,
CSF model,
PCIL model,
interface,
surface tension force.

##### 283 Dynamics of a Vapour Bubble inside a Vertical Rigid Cylinder in the Absence of Buoyancy Forces

**Authors:**
S. Mehran,
S. Rouhi,
F.Rouzbahani,
E. Haghgoo

**Abstract:**

**Keywords:**
Vapour bubble,
Vertical rigid cylinder,
Boundaryelement method,
Finite difference method,
Buoyancy forces.

##### 282 Thermo-mechanical Behavior of Pressure Tube of Indian PHWR at 20 bar Pressure

**Authors:**
Gopal Nandan,
P. K. Sahooa,
Ravi Kumara,
B Chatterjeeb,
D. Mukhopadhyayb,
H. G. Leleb

**Abstract:**

**Keywords:**
Pressure Tube,
Calandria Tube,
Thermo-mechanicaldeformation,
Boiling heat transfer,
Reactor safety

##### 281 Modeling the Fischer-Tropsch Reaction In a Slurry Bubble Column Reactor

**Authors:**
F. Gholami,
M. Torabi Angaji,
Z. Gholami

**Abstract:**

**Keywords:**
Modeling,
Fischer-Tropsch Synthesis,
Slurry Bubble
Column Reactor.