bluuebunny/crossref_metadata_2025 huggingface dataset:
An Experimental Investigation of Turbulent Flow in Concentric Annulus Using Particle Image Velocimetry Technique
Authors: Rodriguez Corredor Fabio Ernesto , Bizhani Majid , Ashrafuzzaman Mohammad , Kuru Ergun
Published: October 2013

Fully developed turbulent flow in a concentric annulus is encountered in many engineering problems including food, chemical as well as oil industry applications. Because of nonlinear radial variation of total shear stress with the distance from the pipe wall, the analysis for the flow in annulus is more complex than in a round tube or parallel plate channel.

In this study, fully developed turbulent flow of water through a horizontal flow loop with concentric annular geometry (inner to outer pipe radius ratio = 0.4) was investigated. Reynolds number range varied from 17,700 to 66,900.

Velocity near the wall region was measured using high resolution particle image velocimetry (PIV) system. Axial mean velocity profile was found to be following the universal wall law (i.e., u+ = y+) close to the wall (for y+ < 10) and log law away from the wall (y+>10).

For all the cases investigated, radial positions of the maximum velocity and zero shear stress were very close to each other (± 0.5 mm). The difference between the both locations were found to be varying from 1.3 to 3.3% ( 2% on the average).
Sand Erosion in Multiphase Flow for Low-Liquid Loading and Annular Conditions
Authors: Vieira R. E. , Kesana N. R. , McLaury B. S. , Shirazi S. A.
Published: October 2013

Low-liquid loading (LLL) and annular gas-liquid flow patterns are commonly encountered in gas transportation pipelines. They may also occur in other off-shore production facilities such as gas/condensate production systems. Experience gained from production of hydrocarbons has shown that severe degradation of production equipment will occur due to sand entrained in gas-dominant multiphase flows.

Sand erosion in multiphase flows is a complex phenomenon since several factors influence the particle impact velocity with the wall. In order to give a more comprehensive understanding of the particle erosion process in this particular scenario and to improve the current semi-mechanistic models, erosion and sand distribution measurements were conducted on 76.2 mm (3 inch) and 101.6 mm (4 inch) diameter pipes in a large scale multiphase flow loop with varying gas (air) and liquid (water) velocities generating low-liquid loading and annular conditions. Particle sizes used in the experiments were 150 and 300 microns with the latter being sharper than the former. Erosion measurements were made at sixteen different locations on a 76.2 mm (3 inch) standard elbow using ultrasonic technology, whereas Electrical Resistance (ER) probes were used for the measurements in a 101.6 mm (4 inch) diameter pipe. The experiments were primarily performed in the upward vertical orientation but a few measurements were performed in the horizontal orientation. Results suggest that the erosion is an order of magnitude higher when the pipe is oriented vertically compared to horizontal orientation. Also, the location of maximum erosion is identified for these flow patterns and it is not dependent on the pipe inclination.
Determination of the Effects of Air Gap and Hind Support on the Sound Absorption Coefficient of Biobased and Foam Materials
Authors: David N. V. , Zainal M. N. , Nor M. J. M.
Published: October 2013

The sound absorption characteristics of wooden and porous materials including fibrous media and porous foams vary with the nature of their surface porosity. The low frequency absorption, which is of interest in noise control engineering, of these material types is generally enhanced by introducing an air gap of a certain width or a flexible support at the rear face of the material posterior to the impinging sound waves. This study investigates the effect of air gap with and without hind support on the low frequency absorption of a kenaf/epoxy composite, a Meranti wood, a low-density rigid foam and a high-density rigid foam. The sound absorption coefficient of these materials are determined using the two-microphone impedance tube transfer-function method according to ISO 10534-2 standard in the frequency range between 20 Hz and 1600 Hz. In this study, 5-mm, 10-mm, 50-mm and 100-mm wide air gaps are introduced at the posterior of the specimens to measure the influence of the quarter-wavelength absorption on sound absorption coefficient. Backing panels made from polyethylene are used to study the effect of hind support on sound absorption coefficient at different frequencies. The dBFA Suite 4.8.1 program is used to acquire and process the acoustic signals and the SCS8100 software package is employed for the computation of sound absorption coefficient. The sound absorption coefficient and characteristics of each material within the range of frequency tested are discussed based on the width of air gap (i.e., the quarter-wavelength effect) in tandem with the presence or absence of the hind support. It is found that the low frequency absorption of the high-density foam with the hind support improved the absorption by 50% as the air gap is increased from 0 to 100 mm. The opposite effect is observed for the other materials tested whereby the sound absorption coefficient is reduced by 30 to 40% with the hind support.
Impact Dynamics of a Constrained Mass-Spring-Damper System
Authors: Luo Albert C. J. , George Richard
Published: October 2013

This paper discusses the vibration of a mass-spring-damper system with two constraints and impact interactions. Impacting chatter and stuck phenomena for the mass with constraints are investigated and the corresponding conditions for such phenomena are determined. Analytical predictions are presented for the system to give a precise and complete demonstration of the phenomena in the system. Finally, an analytical parameter map is given to show how the system changes with parameters. From these conditions, numerical simulations are performed to demonstrate these phenomena in the system.
Energetic Characterization of Decomposing Sample Using Simultaneous Thermal Analysis
Authors: Agarwal Gaurav , Lattimer Brian
Published: October 2013

A simultaneous thermogravimetric analyzer was used to investigate the gravimetric and energetic behavior of a decomposing sample under inert atmosphere. Materials tested in the study included liquid chemicals, polymers and composite samples. Mathematical models were developed from the first law of thermodynamics to quantify the energetic characteristics of a decomposing sample. Along with the effect of evolved gas products, the temperature dependent thermal and physical properties were included in the development of the mathematical models. Models were used to obtain the heat of melting, standard heat of decomposition, heat of decomposition, and heat of gasification of the solid materials. It was determined that the heat of decomposition of a sample is different than the area difference of the apparent and sensible heat flow curves, an approach that is currently used in the literature. The standard heat of decomposition was measured and validated against the standard heat of evaporation of known chemicals. The standard heat of decomposition of a sample was found to be a constant quantity, irrespective of the sample heating rate, initial mass of the sample and the inert content (ash) in the initial mass of the sample. Thus, the standard heat of decomposition is proposed as a unique energetic property of a sample.
The Experimental Investigations on Frequency Dependence of Ferroelectric Properties in Soft PZT-5 Ceramics
Authors: Jin Li-Wei , Su Yu
Published: October 2013

In this work the coupled electromechanical behaviors of the overall properties of ferroelectric ceramics have been experimentally studied with different initial poling states and loading frequencies in order to have a better understanding of their domain switching mechanism. The material under investigation is soft PZT-5 ceramic, which shows noticeable nonlinear response upon externally applied load. The experimental results show that the state of initial poling in the specimens can evidently affect the characteristics of the hysteresis loops. The electrical loading frequency dependence of the ferroelectric properties of PZT-5, e.g., coercive field, remnant polarization, etc., has also been investigated through the tests conducted on the carefully designed multi-field testing system. Despite some common features of frequency dependence shared by all three types of initial poling, it is found out that the effects of loading frequency on the change of coercive field and remnant polarization for the specimen poled perpendicular to the switching axis deviate from those of the other two poling states, and this may be attributed to the specific domain switching mechanism for the perpendicularly poled specimen.
Preliminary Numerical Solutions of the Evolution of Free Jets
Authors: Gori Fabio , Angelino Matteo , Boghi Andrea , Petracci Ivano
Published: October 2013

The present paper presents preliminary numerical solutions of the flow evolution of a two dimensional rectangular free jet. The numerical simulations in a two-dimensional domain are carried out with Open-FOAM, the open-source code, and compare the numerical results with the experimental visualizations performed in the same laboratory with the shadowgraph technique. The evolution of a two-dimensional submerged free jet is reported in the literature by the presence of two regions of flow: the potential core, where the centerline velocity maintains equal to that on the slot exit, and the turbulent or mixing region, where the centerline velocity decreases with the distance from the exit. Previous anemometric measurements, carried out in this laboratory with an air jet emerging from a rectangular channel, showed the presence of a region of flow, just outside the exit and before the potential core, where velocity and turbulence remain almost equal to those measured on the exit, and it has been called “undisturbed region of flow” because is present also in turbulent conditions. Previous and present shadowgraph visualizations show a jet which has the same height along the undisturbed region of flow and increases its height afterwards. The length of the undisturbed region depends on the Reynolds number of the flow and on the presence of turbulence promoters, e.g. metallic grids, at the exit of the slot. The undisturbed region is becoming nil with the increase of the Reynolds numbers, in agreement to the literature. The present two dimensional numerical solutions, carried out at Re numbers equal to 25,000 and 60,000 confirm the results obtained with the shadow visualizations.
A Numerical Study of the Blade Passing Frequency Noise of a Centrifugal Fan
Authors: Cai Jian-Cheng , Qi Da-Tong , Zhang Yong-Hai
Published: October 2013

Tonal noise constitutes the major part of the overall fan noise, especially the blade passing frequency (BPF) noise which is generally the most dominant component. This paper studies the BPF tonal noise of a centrifugal fan, including the blade noise, casing aerodynamic noise, and casing structural noise caused by the flow-induced casing vibration. Firstly, generation mechanism and propagation process of fan noise were discussed and the measured spectra of fan noise and casing vibration were presented. Secondly, a fully 3-D transient simulation of the internal flow field of the centrifugal fan was carried out by the computational fluid dynamics (CFD) approach. The results revealed that the flow interactions between the impeller and the volute casing caused periodic pressure fluctuations on the solid walls of the impeller and casing. This pressure fluctuation induces aerodynamic noise radiation as dipole sources, as well as structural vibration as force excitations. Thirdly, using the acoustic analogy theory, the aeroacoustic dipole sources on the casing and blade surface were extracted. The BPF casing and blade aerodynamic sound radiation were solved by the boundary element method (BEM) taking into account the scattering effect of the casing structure. Finally, the casing structural noise was studied. The casing forced vibration and sound radiation under the excitation of BPF pressure fluctuation were calculated by finite element method (FEM) and BEM, respectively. The result indicates that at the studied flow rate, the sound power levels of the casing aerodynamic noise, blade aerodynamic noise and casing structural noise are 103 dB, 91 dB and 79 dB with the reference sound power of 1×10−12 W, respectively.
A Novel Impact Damper Consisting of a Linear Chain of Particles
Authors: Gharib Mohamed , Ghani Saud
Published: October 2013

Passive control is preferred due to its simplicity and low power consumption. A common passive control device is the Impact Damper which consists of a freely moving mass constrained by two stops inside a container mounted on the primary system. Researchers attempted to develop the impact damper for many decades. Their objective was to decrease the high accelerations, contact forces and noise levels.

In this paper, a novel type impact damper consisting of linear chain of different sizes spherical balls is introduced. The Linear Particle Chain (LPC) impact damper is based on dissipating the kinetic energy of the primary system by placing a small ball between each two large balls in the chain arrangement. The small ball will have numerous collisions with the larger balls when the primary system is excited. This behavior leads to dissipate part of the kinetic energy at each collision with the large balls.

The LPC impact damper is validated by comparing its responses with the single unit conventional impact damper. The free vibration of a single degree of freedom system equipped with the damper is studied. It has been shown that the LPC impact damper is more efficient than the conventional impact damper. A parametric study is conducted to investigate the effective number of balls and the efficient geometry of the impact damper to be used in a specific available space in the primary system.
Simulation and Optimization of Combined Cycle Power Cycles Through HRSG’s Heat Exchangers Arrangement and Parameters for Exergy and Cost
Authors: Naik Ravin G. , Shah Chirayu M. , Mohite Arvind S.
Published: October 2013

To produce the power with higher overall efficiency and reasonable cost is ultimate aim for the power industries in the power deficient scenario. Though combined cycle power plant is most efficient way to produce the power in today’s world, rapidly increasing fuel prices motivates to define a strategy for cost-effective optimization of this system. The heat recovery steam generator is one of the equipment which is custom made for combined cycle power plant. So, here the particular interest is to optimize the combined power cycle performance through optimum design of heat recovery steam generator. The case of combined cycle power plant re-powered from the existing Rankine cycle based power plant is considered to be simulated and optimized. Various possible configuration and arrangements for heat recovery steam generator has been examined to produce the steam for steam turbine. Arrangement of heat exchangers of heat recovery steam generator is optimized for bottoming cycle’s power through what-if analysis. Steady state model has been developed using heat and mass balance equations for various subsystems to simulate the performance of combined power cycles. To evaluate the performance of combined power cycles and its subsystems in the view of second law of thermodynamics, exergy analysis has been performed and exergetic efficiency has been determined. Exergy concepts provide the deep insight into the losses through subsystems and actual performance. If the sole objective of optimization of heat recovery steam generator is to increase the exergetic efficiency or minimizing the exergy losses then it leads to the very high cost of power which is not acceptable. The exergo-economic analysis has been carried to find the cost flow from each subsystem involved to the combined power cycles. Thus the second law of thermodynamics combined with economics represents a very powerful tool for the systematic study and optimization of combined power cycles. Optimization studies have been carried out to evaluate the values of decision parameters of heat recovery steam generator for optimum exergetic efficiency and product cost. Genetic algorithm has been utilized for multi-objective optimization of this complex and nonlinear system. Pareto fronts generated by this study represent the set of best solutions and thus providing a support to the decision-making.
Optimization of Biodiesel Production Using RSM and Study of Combustion Characteristics on DI Diesel Engine
Authors: Sivapirakasam S. P. , Anand R. , Kannan G. R. , Balasubramanian K. R.
Published: October 2013

Biodiesel is a monoalkyl ester of fatty acid of long chain derived from vegetable oil or animal fats. In this present investigation deccan hemp oil, a non-edible vegetable oil is used as feed stock for the production of biodiesel. Response surface methodology based on Central Composite Rotatable Design (CCRD) is used to analyze the interaction effect and to optimize the transesterification reaction variables such as temperature, catalyst concentration and oil to methanol ratio on biodiesel yield. A quadratic model is developed based on the CCRD, correlating the yield of biodiesel with reaction variables. The predicted yield by optimization condition is found very close to the experimental values. The optimum condition for biodiesel production is found at the temperature of 55° C, oil to methanol ratio of 1:9, catalyst of 0.5%, stirring speed of 350 rpm and a reaction time of 3h gave the maximum yield of 95%. The physical and chemical properties of deccan hemp oil and its methyl ester is determined as per ASTM standards. The produced biodiesel showed shorter ignition delay of 10.5° CA and lower heat release rate when compared to diesel at full load condition.
Transient 2-D Heat Transfer Analysis of Encapsulated Phase Change Materials for Thermal Energy Storage
Authors: Zhao Weihuan , Elmozughi Ali F. , Neti Sudhakar , Oztekin Alparslan
Published: October 2013

Solar energy is receiving a lot of attention since it is a clean, renewable, and sustainable energy. A major limitation however is that it is available for only about 2,000 hours a year in many places and thus it is essential to find ways to store solar thermal energy for the off hours. The present work deals with heat transfer aspects of storing solar thermal energy in high temperature phase change materials with melting points above 300 °C. Two-dimension transient heat transfer analysis is conducted to investigate thermal energy storage using encapsulated phase change material (EPCM) for concentrated solar power (CSP) applications. Sodium nitrate, NaNO3, is considered as the phase change material (PCM) encapsulated by stainless steel in a cylindrical shaped capsule. Stream function-vorticity formulation is employed to study the effect of buoyancy-driven convection in the molten salt on the total charging and discharging times for various sizes of PCM capsulated. Simulations are also conducted for a horizontally placed rod inside a flow channel. Storage times are calculated for laminar and turbulent flows of heat transfer fluids transferring heat into EPCM. It is shown that the buoyancy-driven convection in the molten PCM enhances internal heat transfer inside the capsule and hence helps to slightly shorten the total heat transfer times during both charging and discharging processes. Flow characteristics of the heat transfer fluid have profound effect on the nature of phase change process inside the EPCM rod.
Improvement of the Frontal Structure of a Bus for Crash Accidents
Authors: Jeyakumar P. D. , Devaradjane G.
Published: October 2013

The increasing legal and customer demands on passive safety of automobiles have to be fulfilled under the conditions of shortened development times and cost reductions. Today the design process of a bus with regard to its crashworthiness function is driven by a virtual development. A wide range of different applications has to be covered by simulation influencing the design of body-in-white, interior and exterior trim, chassis and power train. In recent days more emphasis has been given to Passenger bus rollover analysis and side impact but the study of frontal impact behaviour of the passenger bus is ignored. The finite element analysis is used for estimating the damage of the passenger bus due to the frontal crash. The vehicle model is allowed to frontal crash with rigid material. The deformation and displacement characteristics of the structure are analyzed at different speeds. Geometric modeling of the bus structure has been created by using CATIA cad package and discritized by ANSYS LS-Dyna. The numerical simulation is carried out for different velocities of bus structure. The results of displacement during collision are plotted on the graph. Some improvements were suggested in the body structure after analysing different types of crack initiators.
A Study of Formation of Circulation Patterns in Laminar Unsteady Lid-Driven Cavity Flows Using PIV Measurement Techniques
Authors: Akyuzlu K. M. , Farkas J.
Published: October 2013

An experimental study was conducted to observe/visualize, the formation of circulation patterns inside a square cavity due to the movement of a lid at constant velocity. Lid driven cavity flow is one of the benchmark studies used in the verification/improvement of CFD codes for internal flow applications/predictions. Previous work on this topic is primarily focused on improving the steady state predictions of the CFD codes using different numerical schemes and algorithms. Furthermore, almost all of the studies reported in computational fluid mechanics literature relates to steady state predictions of lid or shear driven flows. Experimental work that is reported in these studies is limited in scope and number. This paper reports on the measurements we made using Particle Image Velocimeter (PIV) technique to determine the flow field as it develops from stagnation to steady state inside a square cavity driven by a lid. For this purpose, we employed a 2-D PIV system, which uses a double-cavity, Nd:Yag laser to illuminate the test cavity. Experiments were conducted using water as the working fluid inside a square cavity that is one inch (25.4 mm) high and one inch wide. The depth of the cavity is five inches (127 mm) to ensure two-dimensional circulations patterns. Hollow glass sphere particles with 10 microns in diameter were used as seeding of the working fluid, water. Experiments were repeated for different lid velocities corresponding to lid Reynolds numbers (laminar to beginning of transition of turbulence.) Velocity fields were captured during the development of the circulations patters each being unique for the time of the measurement and value of the lid velocity. The center of the circulation pattern and its path inside the cavity is constructed from the captured images as steady state is attained. Also, the strength of the circulation (as manifested by the increase in the diameter of the circulation) is determined at different times for different Reynolds numbers.
Effect of Friction on Contact Stress Distribution in Pin-Loaded Orthotropic Plates
Authors: Aluko O. , Whitworth H. A. , Owolabi G.
Published: October 2013

An analytical solution is presented for determining the stress distribution in pin loaded composite joints using Lekhnitskii’s complex stress function approach. In this analysis, it is assumed that the pin is rigid, no clearance exists between pin and plate, and Coulomb friction is assumed to act throughout the contact region. The analysis also assumes that the contact boundary at the pin-plate interface spans through half of the hole boundary. The boundary conditions at the pin-plate interface are specified in terms of the trigonometric series used to represent the displacement field in the contact zone. Numerical results are presented for stress distribution in (±45°)s and (04°/±45°)s carbon fibers reinforced laminates.
Thermal-Mechanical Analysis of a Low-Enriched Uranium Foil Based Annular Target for the Production of Molybdenum-99
Authors: Govindarajan Srisharan G. , Solbrekken Gary L. , Allen Charlie W.
Published: October 2013

One of the US Department of Energy’s Global Threat Reduction Initiative (GTRI) goals is the elimination of the use of high enriched uranium (HEU) for the production of the radioisotope molybdenum-99 (Mo-99). One strategy to achieve this goal is to use an irradiation target that utilizes a low-enriched uranium (LEU) foil. This paper considers an annular target geometry, where an LEU foil of open cross section is sandwiched between two concentric aluminum tubes. A recess is cut on the inner tube to hold the LEU foil and facilitate assembly. The target must contain the fission products until it can be opened and the LEU foil removed for further processing. The thermal contact resistance between the LEU foil and the aluminum tube cladding needs to be low enough to ensure that the LEU temperature does not exceed the operating temperature specified by the reactor safety case.

Numerical models using the commercial finite element code Abaqus FEA are used to explore the potential for gaps opening between the LEU-foil and the aluminum tubes, and the stresses developed in the aluminum tubes during heat generation in the target during irradiation. Parametric studies are conducted using constructed analytic models to explore the impact of the ratio of heat transfer coefficients between the inner and the outer tubes and the inner-to-outer tube thickness ratio. It is concluded that the current annular target design is safe at high LEU heat generation rates and the use of these targets will likely not compromise the reactor safety.
Understanding the Effect of Baseline Modeling Implementation Choices on Analysis of Demand Response Performance
Authors: Addy Nathan , Mathieu Johanna L. , Kiliccote Sila , Callaway Duncan S.
Published: October 2013

Accurate evaluation of the performance of buildings participating in Demand Response (DR) programs is critical to the adoption and improvement of these programs. Typically, we calculate load sheds during DR events by comparing observed electric demand against counterfactual predictions made using statistical baseline models. Many baseline models exist and these models can produce different shed calculations. Moreover, modelers implementing the same baseline model can make different modeling implementation choices, which may affect shed estimates. In this work, using real data, we analyze the effect of different modeling implementation choices on shed predictions. We focused on five issues: weather data source, resolution of data, methods for determining when buildings are occupied, methods for aligning building data with temperature data, and methods for power outage filtering. Results indicate sensitivity to the weather data source and data filtration methods as well as an immediate potential for automation of methods to choose building occupied modes.
Friction on Tool/Chip Interface in Nanometric Machining of Copper
Authors: Ji Chunhui , Tangpong Annie , Wang Yachao , Shi Jing , Liu Zhanqiang
Published: October 2013

Tool/chip interface on tool rake face is also called the first shear zone in machining processes. The interaction between tool rake face and formed chip greatly affects chip morphology, cutting forces, and other phenomena observed in machining. However, the interaction at nanometric scale has not been addressed by the large body of existing literature on nano-machining. In this study, we adopt the molecular dynamic (MD) simulation approach to model the orthogonal machining of monocryatlline copper by a diamond tool at nanometric scale. Two levels of machining speed, namely, 100m/s and 400m/s, are adopted, and the depth of cut is fixed at 2nm. The tool has a negative rake angle, −30°. Morse potential and EAM potential energy functions are employed to model the interaction pairs of copper/carbon and copper/copper atoms, respectively. The simulation results reveal that not only the cutting force components, but also the ratio of the tangential force along tool movement direction versus the thrust force increases with the increase of cutting speed. More importantly, we investigate the stress distributions along tool/chip interface, and discover that the patterns are overall steady regardless of the change of machining speed or the progress position of cutting tool movement. Compared the simulation results with five dominant friction models for macro machining, none of the five models are suitable to fit the friction distribution patterns obtained in nanometric machining. However, the sliding model with constant friction coefficient seems to be effective in approximating one portion of the friction patterns.
The Reynolds Number Effect on Flow Classification in the Wake of Two Staggered Cylinders
Authors: Wong C. W. , Zhou Y. , Feng S. X.
Published: October 2013

This work aims to investigate, based on the Strouhal number St and the flow structure, the dependence of flow classification on the Reynolds number Re in the wake of two staggered cylinders, with Re varying from 1.5×103 and 2.0×104. The cylinder centre-to-centre pitch, P* = P/d examined is 1.2 ∼ 6.0 (d is the cylinder diameter), and the angle (α) between the incident flow and the line through the cylinder centres is 0° ∼ 90°. Two single hotwires were used to measure simultaneously the St behind each of the two cylinders over 2.5d ∼ 15d. Whilst the present data reconfirms the flow structure modes previously reported, the dependence of the flow modes on P* and α exhibits an appreciable dependence on Re. The observation is connected to the Re effect on the generic features of a two-cylinder wake such as flow separation, boundary layer thickness, gap flow deflection and vortex formation length.
Predicting the Quality of One-Dimensional Periodic Micro and Nano Structures Fabricated via Wrinkling
Authors: Saha Sourabh K. , Culpepper Martin L.
Published: October 2013

Wrinkling of thin films due to buckling-based surface instabilities is a fast and inexpensive technique for template-free fabrication of periodic micro/nano scale structures. Although one-dimensional (1-D) periodic micro and nano structures have been fabricated via wrinkling in the past, wrinkling is not yet appropriate for a manufacturing environment. This is because it is currently not possible to predict and control the quality of the fabricated patterns. Pattern quality is quantified in terms of the uniformity of the pattern, i.e., defect density within the patterned area. Herein, we (i) identify the process parameters that affect pattern quality, (ii) model the effect of these parameters on wrinkling quality and (iii) quantify the feasible operating region for a target pattern quality. During wrinkling, dislocation defects are observed due to local geometric imperfections such as voids or variations in the material properties. We have developed a finite element model of the wrinkling process that accounts for voids in the material. The wavelength and amplitude predictions of this model were found to be within ∼13% of the experimental observations. Also, it was found that below a threshold void size, the non-uniformity in the pattern due to voids decays with an increase in the applied compressive strain. This provides a practical means to minimize the non-uniformity in 1-D wrinkled patterns by increasing the compression. However, the defect density due to surface cracks increases with an increase in the compressive strains. Our analysis enables one to identify and predict the feasible operating region within which uniform 1-D patterns can be obtained, thereby improving manufacturability via wrinkling.
Design of a Microfluidic Device to Induce Noise Damage in Hair Cells of the Zebrafish Lateral Line
Authors: Kwon Hyuck-Jin , Xu Yuhao , Solovitz Stephen A. , Xue Wei , Dimitrov Alexander G. , Coffin Allison B. , Xu Jie
Published: October 2013

Hearing loss affects millions of people worldwide and often results from death of the sensory hair cells in the inner ear. Noise-induced damage is one of the leading causes of hair cell loss. Recently, the zebrafish lateral line system has emerged as a powerful in vivo model for real-time studies of hair cell damage and protection. In this research, we designed a microfluidic device to induce noise damage in hair cells of the zebrafish lateral line. As the first step, a 3-D computational fluid dynamics (CFD) simulation was utilized to predict the flow pattern inside the device. An ideal flow pattern for our application should feature higher velocity at the side and lower velocity in the middle of a channel. Flow induced from ordinary channel geometry with single inlet/outlet pair would not work for us because the boundary layers from the two side walls will grow and merge with each other and induce the maximum flow speed in the middle of the channel. In order to achieve the desired flow pattern, side-wall inlet/outlet pairs were used to suppress the growth of boundary layers. CFD simulation was used to design important parameters such as dimensions of the microfluidic channel and the angle of inlets and outlets. It was found that flow velocity at the side of the channel could be 6.7 times faster than the velocity in the middle when we array the inlets and outlets alternatively and set the angle of the inlet to 45° with 2.0 mm main channel width. This 3-D CFD model will serve as a convenient model to design a microfluidic device to induce noise damage in hair cells of a zebrafish lateral line by manipulating the flow pattern inside the device.
An Experimental Study on the Effect of Natural Rubber Coating on Tensile Properties of Dyneema® Single Yarn
Authors: David N. V. , Ahmad M. R.
Published: October 2013

The effect of natural rubber (NR) coating on the quasi-static tensile properties of unidirectional Dyneema® SK-76 single yarn is experimentally studied. Single Dyneema® SK-76 yarns are uniformly coated with pre-vulcanized natural rubber latex. Quasi-static tensile tests are performed on plain (uncoated) and NR-coated samples at the strain rates of 0.006 s−1, 0.06 s−1 and 0.6 s−1. The force and strain at peak, and the tenacity of the plain and NR-coated yarns are obtained for each strain rate. The results show that the peak force in the plain samples increases with strain rate to a maximum of 163 N. The tenacity (breaking force per denier) of the uncoated yarns also, in correspondence, increases with strain rate. In contrast, the tenacity of the NR-coated samples remained constant at but a lower value than that of the plain samples. It is observed that peak force sustained by the NR-coated yarns is insensitive to strain rate and up to 560% higher than that supported by the plain yarns. The peak strain of both the plain and NR-coated samples varies with strain rate in a comparable fashion. However, the peak strain values of the NR-coated yarn are greater by an average of 20% than of the plain yarn. The experimental data thus reveal that NR coating has a constructive effect on the peak force and peak strain of the yarn but decreases its tenacity to a constant value. Micrographs of the fractured samples obtained from Field Emission Scanning Electron Microscope are studied to explore the role of NR in the failure mechanism of the coated yarn.
Computational Study of Single-Sided Ventilation Through a 3-Dimensional Room
Authors: Idris A. , Huynh B. P.
Published: October 2013

Ventilation flow through a 3-dimensional rectangular-box room is investigated numerically, by using a commercial Computational Fluid Dynamics (CFD) software package. The room has all its window openings located on one wall, and the wind is assumed to blow parallel to this wall. The standard K-epsilon turbulence model is used. Air’s flow rate and flow pattern are considered in terms of wind speed and the openings’ characteristics, such as their number, location, size and shape. For a constant total area of the openings, it is found that ventilation rate increases with more openings, especially when they are widely separated or positioned at different heights.
Thermal Conductivity and Thermal Transport Relaxation Time of CNT Packed Beds
Authors: Liu K. , Cui S. , Qi X. , Chen C. , Hu X.
Published: October 2013

We report on experimental measurements of transient heat transfer characteristics of carbon nanotube (CNT) aggregates for the temperature range from 120K to 370K. Giant thermal transport relaxation time (τ) is observed: about 100s at room temperature and increased up to 260s at lower temperatures, one order of magnitude bigger than the biggest value reported so far in literatures. These unusual big τ values may imply significant thermal transport phase lag across CNT contacts. A relaxation time based model is proposed to characterize the transient thermal transport behavior between contacting CNTs. This finding may stimulate new ways to improve the efficiency of thermal energy conversion by using nanoscale materials.
CFD Simulation and Optimization of the Center-to-Ends Oxidation Furnace Airflow Distributor Geometry to Investigate Uniform Airflow
Authors: Heidari Amir , Montazerinejad Sara , Badrnejad Ramin
Published: October 2013

In this paper different rectangular and trapezoidal ducts have been simulated to optimize airflow uniformity inside the oxidation furnace by computational fluid dynamics (CFD) technique. The optimizations have been done in different duct geometries to satisfy homogenous air flow pattern over the whole process room. Results have shown that airflow uniformity is the main factor for the best quality of the produced fiber during oxidation. Oxidation process is primarily an exothermic reaction, so consistent and uniform airflow is essential to successfully remove heat of oxidation from each filament across the web to obtain quality product.

In our study, the oven geometry is very simple and consists of multi zones and provides a homogenous airflow parallel to the fiber hand. It is noticeable that airflow turbulence is minimized to prevent cosmetic damage to fiber tows. Results demonstrate our optimized air-distributor designs provide the requested uniform airflow and eliminate non ventilated dead zones between the boxes.
Data Reduction of Friction Factor of Compressible Flow in Micro-Channels
Authors: Kawashima D. , Asako Y.
Published: October 2013

This paper focuses on data reduction of friction factor of compressible fluid flowing through micro-channels. The both pressure and temperature are required to calculate the friction factor of compressible flow. Therefore, in the past data reduction of many experiments, the friction factors have been obtained under the assumption of isothermal flow since temperature measurement of compressible flow in micro-channels is quite difficult due to the experimental technique limitation. The authors find that the temperature of the fluid can be obtained from the pressure under the assumption of one dimensional flow in an adiabatic channel (Fanno flow). In this paper, the temperatures obtained by our proposed equation are compared with results of numerical simulations and friction factors are also compared.
Chip Design for Coupled Nonlinear Structronic Thermo-Electro-Elastic/Control Systems
Authors: Tzou H. S. , Li Huiyu , Li Hua
Published: October 2013

The objective of this study is to demonstrate the feasibility that a fully-coupled nonlinear piezo(electric)-thermoelastic/control structronic systems can be represented by a single micro-electronic chip. This non-volatile chip is a poTable.lle miniature hardware that serves as a design standard for future calibration and diagnosis of the original “large-scale” structronic system and it can be used anywhere after any catastrophic disruption in extreme hostile environments. Distributed control of a nonlinear structronic beam system (i.e., an elastic beam laminated with distributed sensors/actuators and coupled with control electronics) subjected to mechanical and temperature excitations has been investigated recently. This study is to design an integrated electronic circuit chip encompassing the complete piezothermoelastic and control behavior of the nonlinear structronic beam system. The fully coupled nonlinear beam equations are first discretized into a number of “elements” and each element can be implemented by an active circuit block including operational amplifiers, resistors, capacitors, and other nonlinear multipliers. Signals from the integrated circuit chip of the coupled nonlinear piezothermoelastic beam system are favorably compared with analytical solutions.
Stress Analysis and Sealing Performance Evaluation in Bolted Flange Connections With Ring Joint Gasket Subjected to Internal Pressure
Authors: Kondo Koji , Tsubaki Shota , Sawa Toshiyuki , Sato Koji , Omiya Yuya
Published: October 2013

Bolted flange connections with ring joint gaskets have been used to seal the inner fluid under higher pressure and higher temperature condition when soft gasket cannot be used in the connection. The ring joint gaskets are assumed that they can seal inner fluid by the metal-metal contact between the ring joint gasket and the grooves of flanges under higher pressure condition. However, no research on the characteristics and sealing performance evaluation for the bolted flange connections with metal ring gasket has been conducted. Therefore, assembly procedures and tightening methods of the connection with ring joint gaskets is empirically. It is important to know the characteristics such as the contact gasket stress distribution, the sealing performance and the sealing mechanism in the bolted flange connections for determining optimum tightening methods and the bolt preload. In this paper, the leakage tests for the bolted flange connections (3″) with the octagonal ring joint gaskets are conducted. Measuring the leak rate of inner fluid from the connections using the pressure drop method, the sealing performance of the connections with the ring joint gaskets is evaluated. In addition, using the 3-D FEM stress calculations, the gasket contact stress distributions for the connections with the octagonal ring joint gaskets are examined. Using these results, the optimum bolt preload of the connection with octagonal ring joint gaskets are discussed. Furthermore, the leakage tests for the bolted flange connections (20″) with the octagonal ring joint gaskets are conducted in the case where the bolt tightening is carried out according to both ASME PCC-1 and JIS B 2251, respectively. The optimum tightening methods for the connection with octagonal ring joint gaskets are discussed.
Application of Tornado-Flow Fundamental Hydrodynamic Theory to the Study of Blood Flow in the Heart and Main Vessels: Design of New Implantable and Accessory Devices for Cardiovascular Surgery
Authors: Bockeria Leo A. , Kiknadze Gennady I. , Agafonov Andrei V. , Gachechiladze Ivan A. , Gorodkov Alexander Y.
Published: October 2013

The study of the hydrodynamic structure of Tornado-like swirling viscous flows has proved that these flows possess a strictly organized laminar structure which can be exhaustively described using the exact solution of nonstationary Navier-Stocks and Continuity equations [6]. The flows of this type belong to the class of quasi-potential self-organizing swirling flows that serve the restoration of equilibrium in nature. These flows are characterized by a high efficiency of medium transportation while the energy losses are minimized. This is manifested in a significant decrease of hydrodynamic resistance and special organization of the boundary layer. Recent studies performed in Bakulev Research Center for Cardiovascular Surgery (Moscow, RF) have proved that the structure of blood flow corresponds to the class of Tornado-like swirling flows. This allows modeling the optimum geometry of the surgically reconstructed flow channel of the heart and major arteries in order to exclude excessive flow disturbances. Most currently used substituting implantable devices contacting with the blood do not take into account the peculiar hydrodynamic properties of blood flow in the heart and great vessels. This leads to the formation of undesirable disturbance of the hydrodynamic flow structure, i.e. stagnant or separation zones, which can create conditions for thrombus formation and hyperplasia. Therefore, the exact solution can serve as a basis for the design of implantable devices contacting with blood flow without significant distortion of its structure. The following devices have been proposed.

- The aortic valve prosthesis, whose flowing surface has a convergent circular cross-section in the open position. Use of this prosthesis should provide significant reduction in the intensity of anticoagulant therapy after implantation.

- Blood vessel prosthesis with radial elasticity and convergent shape in accordance with the replaced section of artery.

- Circulatory assist device, whose working chamber contains directing profile on the inner surface corresponding to the Tornado-like flow streamlines.

- Hydrodynamic bench for physical modeling of the Tornado-like flow with specified characteristics, allowing testing of implantable devices contacting with blood flow under physiological conditions. The implantable devices for cardiovascular surgery designed on the basis of exact solutions of nonstationary hydrodynamics equations for the Tornado-like swirling flows will be more effective and safe, will reduce the rehabilitation time, and improve the quality of life of patients after surgery.
An Experimental Study of Perpendicular Acoustic Disturbances Effect on Flow Over an Aerofoil at Low Reynolds Numbers
Authors: Genç M. Serdar , Akpolat M. Tuğrul , Açıkel H. Hakan , Karasu İlyas
Published: October 2013

In this study, the effect of perpendicular acoustic excitation on laminar separation bubble over a NACA2415 aerofoil and stall characteristics of the aerofoil was investigated experimentally at low Reynolds numbers (50000 and 75000) and various angles of attack on the aerofoil using force measurement, pressure measurement and smoke-wire flow visualization techniques. The experiments of resonance characteristics of test section of the wind tunnel showed that the frequencies used for acoustic control were not equal to the peak (resonance) frequencies of the wind tunnel test section. The experimental results of acoustic control showed that when acoustic excitation of a certain frequency was applied, the length of the laminar separation bubble was shortened owing to the energy added to the flow by acoustic excitation. Because of the shortened laminar separation bubble, coefficient of lift was increased. Furthermore, at the stall angles the separated flow was forced to reattach to the surface of the aerofoil, so the stall angle was increased from 12° to 17° and maximum coefficient of lift was increased from 1.16 to 1.24 at Re = 50000 and from 13° to 18° and maximum coefficient of lift was increased from 1.18 to 1.34 at Re = 75000.