bluuebunny/crossref_metadata_2025 huggingface dataset:
Shell Side Flow and Heat Transfer Performances of Trisection Helical Baffle Heat Exchangers
Authors: Chen Yaping , Dong Cong , Wu Jiafeng
Published: April 2014

The flow and heat transfer performances of three trisection helical baffle heat exchangers with different baffle shapes and assembly configurations, and a continuous helical baffle scheme with approximate spiral pitch were numerically simulated. The four schemes are two trisection helical baffle schemes of baffle incline angle of 20° with a circumferential overlap baffle scheme (20°TCO) and a end-to-end helical baffle scheme (20°TEE), a trisection mid-overlap helical baffle scheme with baffle incline angle of 36.2° (36.2°TMO), and a continuous helical baffle scheme with baffle helix angle of 16.8° (18.4°CH). The pressure or velocity nephograms with superimposed velocity vectors for meridian slice M1, transverse slices f and f1, and unfolded concentric hexagonal slices H2 and H3 are presented. The Dean vortex secondary flow field, which is one of the key mechanisms of enhancing heat transfer in heat exchangers, is clearly depicted showing a single vortex is formed in each baffle pitch cycle. The leakage patterns are demonstrated clearly on the unfolded concentric hexagonal slices. The results show that the 20°TCO and 18.4°CH schemes rank the first and second in shell-side heat transfer coefficient and comprehensive indexes ho/Δpo and ho/Δpo1/3. The 20°TEE scheme without circumferential overlap is considerably inferior to the 20°TCO scheme. The 36.2°TMO scheme is the worst in both shell-side heat transfer coefficient and comprehensive index ho/Δpo1/3.
On Sustainability Assesment of Machining Processes
Authors: Raza Syed Waqar , Deiab Ibrahim Mostafa
Published: April 2014

There is an increased interest in sustainability assessment of manufacturing systems and processes because of the growing global interest in sustainable manufacturing practices. The current sustainability assessment models present a holistic approach, e.g. LCA, without much focus on process specific details. This paper uses a ‘XSI’ approach for defining sustainability indices (e.g. Energy Sustainability Index, ESI). These sustainability metrics can quantify machining processes in terms of impact on the environment and power consumption in a flexible manner, so that various material removal processes can be rated on a uniform scale. In addition, the concept of Normalization, with respect to the ‘feature-of-interest’ is introduced, thus presenting a flexible rating system in terms of process types (turning, milling etc.) and perspectives (material removal, quality etc.). A user-friendly calculator is developed, which converts a set of inputs for the machining scenario into a set of measurable rating quantities and indices including but not limited to production rate, production cost, tool life/cost, energy consumption and environmental burden. This will enable the manufacturing engineer to make an informed decision about parameter selection and process design for sustainability. Machining of hard-to-machine materials such as Titanium Alloys is such a scenario, which is used as a case study to validate the proposed approach.
Modeling and Fabrication of Heterogeneous Three-Dimensional Objects Based on Additive Manufacturing
Authors: Huang Pu , Deng Dongping , Chen Yong
Published: April 2014

Heterogeneous object modeling and fabrication has been studied in the past few decades. Recently the idea of digital materials has been demonstrated by using Additive Manufacturing (AM) processes. Our previous study illustrated that the mask-image-projection based Stereolithography (MIP-SL) process is promising in fabricating such heterogeneous objects. In the paper, we present an integrated framework for modeling and fabricating heterogenous objects based on the MIP-SL process. Our approach can achieve desired grading transmission between different materials in the object by considering the fabrication constraints of the MIP-SL process. The MIP-SL process planning of a heterogeneous model and the hardware setup for its fabrication are also presented. Test cases including physical experiments are performed to demonstrate the possibility of using heterogeneous materials to achieve desired physical properties. Future work on the design and fabrication of objects with heterogeneous materials is also discussed.
Non-Destructive Evaluation of Composite Adhesive Kissing Bond
Authors: Liu Yingtao , Johnston Joel , Chattopadhyay Aditi
Published: April 2014

Adhesive bonded joints have been increasingly employed in aerospace, automotive, and other mechanical systems due to the advantages of uniform stress distribution, less stress concentration, light in weight, etc. However, the early damage stage of the adhesive bond joints, which are usually named as kissing bond, can significantly impact the structural integrity and safety. Kissing bond is difficult to detect and identify using current non-destructive evaluation (NDE) techniques since there is no clearly gap or interface between the bond area. Attempts using advanced ultrasonic methods have reached limited success, but more reliable methods need to be developed before adhesive joints can be more widely applied to the engineering field. This paper focuses on the development of detection method using digital image correlation (DIC) technique. Three types of adhesive kissing bond joint samples were fabricated using different contamination recipe to simulate the kissing bonds. The performance of the fabricated joint samples were tested using uniaxial hydraulic test frame and the detection capability of DIC system was investigated. The noncontact strain field measurement method using DIC can indicate the existence of kissing bonds with limited load. The results of DIC measurement is encouraging and can be further used for the NDE estimation of mechanical properties of the kissing bond.
Structural Behavior of Microbeams Actuated by Out-of-Plane Electrostatic Fringing-Fields
Authors: Ouakad Hassen M.
Published: April 2014

In this paper, we present an investigation of the static behavior of a doubly-clamped microbeam actuated electrically through out-of-plane electrostatic fringing-fields. The distributed electrostatic force is caused by the asymmetry of the fringing-fields. This is actually due to the out-of-plane asymmetry of the beam and its two actuating stationary electrodes. The electric force was approximated by means of fitting the results of two-dimensional numerical solution of the electrostatic problem using Finite-Element Method (FEM). Then, a reduced-order model (ROM) was built using the Galerkin decomposition with linear undamped modes of a clamped-clamped beam as base functions. The ROM equations are solved numerically to get the static response of the considered micro-actuator when actuated by a DC load. Results shows possibility of having three different regimes for this particular MEMS device: a bending regime, a catenary regime, and an elastic regime. Eigenvalue problem is then solved to get the variation of the fundamental natural frequency when the system is deflected by a DC load. Results show that controlling the microbeam stroke, with a DC voltage on the gate electrodes, enables us to tune the system frequency, resulting in a possibility of a tunable MEMS device without a pull-in scenario.
Experimental Study of Thermoelectric Properties of SWCNTs and SiC Nanoparticles and its Composites Doped With Sol-Gels
Authors: Khan Mujibur R. , Jones Miletus , Bugarin Luz , Sandoval Salvador
Published: April 2014

Thermoelectric (TE) properties of Single wall carbon nanotubes (SWCNTs) and Silicon carbide (SiC) nanoparticles after treated with sol-gel dopants at elevated temperature. Different combinations of P and N type sol-gels were used. The combinations were Boron-Antimony, Aluminum-Antimony, Aluminum-Phosphorus and Boron–Phosphorus. The nanoparticles were randomly distributed on a nonconductive glass substrate and hot and cold junctions were created using silver epoxy and Alumel (Ni-Al) wire. The carbon nanotubes used were approximately 60% semiconducting and 40% metallic. Voltage (mV), current (μA) and resistance (Ω) were measured across the distributed nanoparticles within 160° C temperature difference. The Seebeck coefficient for pristine SWCNTs was 0.12 mV/oC. When doped with Boron-Antimony the Seebeck coefficient increased to 0.981 mV/°C. On the hand, SiC nanoparticles showed no TE effect at pristine form, but when infused with SWCNTs substantial TE effect was present. Even though the Seebeck coefficient was in a similar range with different SWCNT concentrations (wt%), current, resistance and Power factor (P.F.) changed with wt% of nanotubes. Resistance of the nanotube samples slightly decreased with the increase in temperature. Finally, the SiC+SWCNT composites were prepared using the sintering process at around 1500° C. Thermoelectric and Mechanical properties of the composites were tested. The structure-property relation was analyzed using SEM (scanning electron microscope) and XRD (X-ray diffraction). It was revealed that fiber like SWCNTs created randomly distributed network with Nano contact junctions inside the SiC matrix and enhance thermoelectric and mechanical properties in the combined SiC+SWCNTs material system. Put abstract text here.
Development of Gas Compressor Diagnostic Program Using Knowledge Based Management Concept
Authors: Sulaiman Shaharin Anwar , Abdul Rahman Khairil Ikhwan , Jasmani Mohd Shahrizal
Published: April 2014

Gas compressor reliability is vital in oil and gas industry because of the equipment criticality which requires continuously operations. Currently, plant operators often face difficulties in predicting appropriate time for maintenance and would usually rely on time-based predictive maintenance intervals as recommended by Original Equipment Manufacturer. Delayed decision on compressor maintenance intervention has caused prolonged downtime due to poor readiness of spare parts and resources. The paper discussed on development of a software-based tool which is able to assist machinery engineers to quantify performance deterioration of gas compressor and predict optimum time for maintenance activities. Maintenance history data is collected and analysed regularly and maintenance advices are subsequently produced based on the input parameters. Natural gas compressors of an oil producing offshore platform at Peninsular Malaysia are used as a case study of this project. It was found that isentropic efficiency and head decrease, but gas power increases parabolically with time for the low pressure compressors, suspected due to heavy component fouling. From these information, Compressor Performance Monitoring Program is developed which able to compute the fouling level of the compressor in terms of performance indicators deviations. The results are then being utilized to estimate future maintenance requirements based on historical data. In general, this software provides a powerful tool for gas compressor operators to realize predictive maintenance approach in their operations.
Phase-Field Simulations of Bubble Growth Under Convective Conditions
Authors: Badillo Arnoldo A.
Published: April 2014

Although many years have past from the pioneer work of Lord Rayleigh [1] on bubble growth in the inertia controlled regime and later from Scriven [2], Plesset and Zwick [3] for the diffusion controlled regime, we are still missing mathematical model able to predict accurately both situations. Advances in computational power open the possibility of exploring up-close the transport phenomena in the vicinity of the liquid-vapor interface at an unprecedented resolution. Nonetheless, a high numerical resolution is not enough to fully solve the general problem of bubble growth. New models based on a sharp-interface interpretation of the liquid-vapor interface, have proven to provide accurate results in the diffusion controlled regime, however, these models must assume the interface temperature at the saturation value, restricting their application to physical situations where the evaporation rate satisfies the Stefan condition and bubbles are big enough as to neglect the curvature effects in the interface temperature. In an attempt to provide a more general framework to study bubble growth, a new phase-field model has recently been derived, where no assumption is made on the interface temperature. In this new model, the evaporation rate depends on the local interface temperature and not directly on the heat balance at the liquid-vapor interface. In principle, this particular feature of the model should allow us to simulate both, the inertia and diffusion controlled regimes, but the model has only been validated for the latter. The next step in the validation process is the simulation of bubble growth under convective conditions. Experiments of single bubbles growing and rising up under normal gravity conditions have shown that the growth exponent is about 0.8, in contrast to the value of 1.0 for the inertial controlled regime and 0.5 for the diffusion controlled regime. In this work, fully three dimensional phase-field simulations of bubble growth under convective conditions are presented, where the predicted bubble size and growth exponent compare very well to experimental observations.
Method for Individual Control of Multiplexed Droplet Generation in Digital Microfluidic Devices
Authors: Schertzer Michael J. , Yang Zhifang , Ben-Mrad Ridha , Sullivan Pierre E.
Published: April 2014

This investigation presents two methods for multiplexed droplet generation in digital microfluidic devices. Analytical and experimental results show that the number of electrical output signals required for multiple reagent systems can be reduced by electrically connecting all but one electrode in each droplet generation path on the device. Both methods reduce the number of electrical signals required for generating droplets from multiple reservoirs by M(N−1), where M is the number of manipulation electrodes in the generation path and N is the number of reservoirs on the device. The first method uses individually controlled reservoirs to minimize the manipulation of the fluid in the unused reservoir, while the second method individually controls one of the electrodes in the generation pathway to allow for closed loop control of droplet generation. In both cases, droplets are kept at rest by simultaneously activating or deactivating all adjacent electrodes. These methods can be easily integrated into devices with multiple reservoirs without computational expense or prior knowledge of the electrode activation sequence. They can also be used in concert with droplet control algorithms for pin constrained systems to further reduce the number of output channels required in a digital microfluidic device.
Pressure Exchange Heat Pump: Natural Gas Residential Air Conditioning
Authors: Garris Charles A. , Liang Chunlei
Published: April 2014

There is a strong societal need for a thermally-based air conditioning system which can provide cooling in the summer to small homes and businesses. There is currently no technology available today that can fill this vast market in a cost-effective manner. This paper discusses a potentially important technology which has the potential of contributing to this need, as well as helping to reduce carbon emissions. The paper discusses this technology, it potential, and describes some of the preliminary computational work that will lead to its ultimate development.
Tire-Terrain Normal and Longitudinal Dynamics and Slip Power Losses of an Unmanned Ground Vehicle
Authors: Salama Mostafa , Vantsevich Vladimir V.
Published: April 2014

Studies of the tire-terrain interaction have mostly been completed on vehicles with steered wheels, but not much work has been done regarding skid-steered Unmanned Ground Vehicles (UGV). This paper introduces a mathematical model of normal and longitudinal dynamics of a UGV with four skid-steered pneumatic tire wheels. Unlike the common approach, in which two wheels at each side are treated as one wheel (i.e., having the same rotational speeds), all four wheels in this study are independently driven. Thus the interaction of each tire with deformable terrain is introduced as holonomic constraints.

The stress-strain characteristics for tire-soil interaction are analyzed based on modern Terramechanics methods and then further used to determine the circumferential wheel forces of the four tires. Contributions of three components of each tire circumferential force to tire slippages are modeled and analyzed when the tire normal loads vary during vehicle straight-line motion. The considered tire-soil characteristics are mathematically reduced to a form that allows condensing the computational time for on-line computing tire-terrain characteristics. Additionally, rolling resistance of the tires is analyzed and incorporated in the UGV dynamic equations.

Moreover, the paper describes the physics of slip power losses in the tire-soil interaction of the four tires and applies it to small skid-steered UGV. This study also formulates an optimization problem of the minimization of the power losses in the tire-soil interactions due to the tire slippage.
Floating Type Ocean Wave Power Station (Wells Type Runner Work Submerged in Seawater)
Authors: Okamoto Shun , Eshima Toru , Kanemoto Toshiaki , Umekage Toshihiko
Published: April 2014

The authors have invented the unique ocean wave power station, which is composed of the floating type platform with a pair of floats lining up at the interval of one wave pitch and the counter-rotating type wave power unit boarding on the middle position of the platform. Such profiles may make the flow velocity at the runner twice faster than that of the traditional fixed type (OWC). The counter-rotating type wave power unit is composed of the tandem runners submerged in the seawater and the peculiar generator with double rotational armatures. The tandem runners counter-rotate in keeping each rotational direction constant, even at the oscillating flow, where the relative rotational speed is also twice faster than that in the single runner/armature type. It can be expected to make the runner size larger, namely the output higher because the torques are counter balanced in the unit and never act on the platform.

At preliminary research, the single stage Wells type runner was boarded on the above platform, while the behavior of the platform and the performance of the power unit were investigated experimentally. The runner works fruitfully in response to the oscillating platform.
Micro Thermal Lab in a Droplet
Authors: Gao Meng , Gui Lin
Published: April 2014

Droplet-based microfluidic system has the potential to provide a high throughput platform for applications in chemical and biological analysis. In this report, the concept of micro thermal lab in a droplet was proposed. A droplet of room temperature liquid-metal (Gallium-base alloy) was used to perform the thermal experiments. By applying controllable heating power, the liquid-metal droplet worked as an electrical resistor, generating Joule heat to accurately control its temperature. A proportional-integral-derivative (PID) temperature controller was used to control the heating power. Because the liquid-metal droplet has high surface-area-to-volume ratio and high thermal conductivity, it can be cooled down rapidly just by natural convection when left in atmosphere with the heating power switched off. Because of its small heat capacity and high heat conductivity, the liquid-metal droplet has rapid thermal response and uniform temperature distribution inside, which is ideal for a thermal experiment. This liquid-metal droplet can work as a micro thermal lab, which can offer a well-programmed, easily controllable, and thermally uniform microenvironment for on-chip chemical and biological analysis, such as PCR, cell culture and so on.
Implant Localization in Human Body Using Adaptive Least-Squares Based Algorithm
Authors: Çamlıca Ahmet , Fidan Barış , Yavuz Mustafa
Published: April 2014

In this study, we focus on the problem of localizing an implant or a capsule device in the human body by a mobile sensor unit using distance measurements. As a particular distance measurement technique, time of flight (TOF) based approach involving ultra wide-band signals is used, noting the important effects of the medium characteristics for different organs and tissue. We propose a least-squares based adaptive algorithm with forgetting factor to estimate the 3-D location of an implant in the human body. After discussing convergence properties of the proposed localization algorithm, we perform simulations to analyze the transient characteristics of the proposed algorithm. Different white Gaussian noises are added to emulate the TOF measurement noises and environmental disturbances, and it is observed that the proposed algorithm is robust to such noises/disturbances. The algorithm is successful in keeping the estimation error at a very low admissible level.
A Leader-Following Formation Control of a Group of Car-Like Mobile Robots
Authors: Lee Ho-Hoon
Published: April 2014

This paper proposes a leader-following formation control strategy for a group of car-like mobile robots. The leader follows its desired trajectory while the rest of robots are following the leader in a specified formation. The proposed formation control computes desired driving force and steering torque for each robot. The proposed control consists of a formation control scheme and a kinematic trajectory generation scheme for the leader of a group. The nonholonomic constraints of the car-like mobile robots are taken into account in the design of the formation control and trajectory generation scheme, in which the Lyapunov stability theorem and the loop shaping method are used as design tools. Under certain conditions, the proposed formation control guarantees asymptotic stability while keeping all internal signals bounded. The effectiveness of the proposed control has been shown with realistic computer simulations.
Lyon-Type Integral Forms of Wall Friction, Heat- and Mass Transfer Closure Relationships for Non-Equilibrium Two-Phase Flows: Generalization for Annular and Rod Cluster Geometries
Authors: Kornienko Yuri
Published: April 2014

The main goal of this paper is to describe new approach to constructing generalized closure relationships for pipe, annular and sub-channel transfer coefficients for wall friction, heat and mass transfer. The novelty of this approach is that it takes into account not only axial and transversal parameter distributions, but also an azimuthal substance transfer effects. These constitutive relations, which are primordial in the description of single- and two-phase one-dimensional (1D) flow models, can be derived from the initial 3D drift flux formulation. The approach is based on the Reynolds flow, boundary layer, and substance transfer generalized coefficient concepts. Another aim is to illustrate the validity of the “conformity principle” for the limiting cases. The method proposed in this paper is founded on the similarity theory, boundary layer model, and a phenomenological description of the regularity of the substance transfer (momentum, heat, and mass) as well as on an adequate simulation of the flow structures. With the proposed generalized approach it becomes possible to develop an integrated in form and semi-empirical in maintenance structure analytical relationships for wall friction, heat and mass transfer coefficients.
Enhanced Human Bone Marrow Mesenchymal Stem Cell Functions in 3D Bioprinted Biologically Inspired Osteochondral Construct
Authors: Holmes Benjamin , Zhang Lijie Grace
Published: April 2014

Cartilage defects, which are caused by a variety of reasons such as traumatic injuries, osteoarthritis, or osteoporosis, represent common and severe clinical problems. Each year, over 6 million people visit hospitals in the U.S. for various knee, wrist, and ankle problems. As modern medicine advances, new and novel methodologies have been explored and developed in order to solve and improve current medical problems. One of the areas of investigation that has thus far proven to be very promising is tissue engineering. Since cartilage matrix is nanocomposite, the goal of the current work is to use nanomaterials and nano/microfabrication methods to create novel biologically inspired tissue engineered osteochondral scaffolds for facilitating human bone marrow mesenchymal stem cell (MSC) differentiation. 3D printed polymer constructs were designed to mimic the osteochondral region of articulate joint, and to have enhanced mechanical characteristics when compared to traditional designs. Fabricated scaffolds were also subject to surface modification, both with a chemically functionalized acetylated collagen coating and through absorption via poly-L-lysine coated carbon nanotubes. In vitro proliferation results demonstrated not only that incorporation of the biomimetic carbon nanotubes and poly L-lysine coating and acetylated collagen can induce more proliferation of MSCs than controls, but that more controlled and biomimetically designed features also enhance proliferation of MSCs.
Characterizing High Temperature Thermoelectric Modules
Authors: Mahajan Satchit B. , Pierce Reginald D. , Stevens Robert J.
Published: April 2014

With the accelerating improvements and interests in high temperature thermoelectric materials and their applications for power generation, there is the emerging need to fully characterize thermoelectric modules. One of critical challenges in testing modules, especially at high temperatures, is being able to accurately control and measure heat rates transferred across a module. Many of the current characterization techniques are limited to solely measuring the electrical response and ignore the heat transfer. The new technique, described within, is able to accurately measure the three key characteristic properties, namely Seebeck coefficient, electrical resistance, and thermal conductance of a thermoelectric module over temperature ranges from 50 to 650°C. To ensure isothermal surfaces and minimize heat rate errors, a primary heater is encased in a guard heater. Rapid pulsed electronic loading allows for rapid voltage-current scans while avoiding thermal drift. The thermal conductivity of a reference material is used to validate the performance of the guard heater assembly and heat monitoring setup.
The Study of a Liquid Droplet Falling Through Two Immiscible Layers of Liquids
Authors: Mesa Bianca
Published: April 2014

In an exploratory experiment, we noticed the unusual behaviors of liquid droplets falling through layers of oil and water. A rectangular container was filled with an aqueous solution at the bottom and a layer of oil on top. A dropper was used to control the size of the droplet entering the liquid column. In addition, water was mixed with a small amount of Bromothymol Blue dye, a chemical indicator, to visualize the detailed flow processes. It was noticed that initially, the liquid droplet moved through the oil layer and was stopped at the oil/water interface, supported by surface tension and the buoyancy of the oil layer between the liquid droplet and the water below. As time passed, the support was weakened and the droplet would start to fall quickly through the water. Two types of droplets were used. The first case was a salt water solution with NaOH, and the second consisted of balsamic vinegar and NaOH. As soon as the salt water droplet touched the aqueous solution, it collapsed and sank as well as spread rapidly at the interface. The sinking motion eventually dragged the spreading fluid back to its center and then down. For the balsamic vinegar case, a trace amount of the droplet spread rapidly at the interface while the main portion of the droplet would first sink and then spontaneously explode. The difference in behavior is mainly due to the surface tension of the droplet in water. The underlying mechanisms of the droplet’s flow instability are from the effects of diffusion weakening the surface tension.
CFD Study on Counterflow Ceramic Microchannel Heat Exchanger With Different Fins
Authors: Chu W. X. , Ma T. , Zeng M. , Wang Q. W.
Published: April 2014

The conventional heat exchangers cannot satisfy the high efficiency and power requirements due to the low heat transfer performance and large volume. With the development of micro-scale manufacture technology, the ceramic micro-channel heat exchangers are recommended to be used to the highly-efficiency power and propulsion systems, especially the very high temperature conditions. The present paper analyzes the thermal hydraulic performance of the alumina-based ceramic microchannel heat exchangers with four different fins (straight, Z-shaped, airfoil and S-shaped). The numerical results show that the maximal heat transfer rate and heat transfer effectiveness of the heat exchanger with Z-shaped fins reach 90.7 W and 61%, respectively. The temperature distribution of both fluid sides and solid body is predicted. Moreover, the pressure drop and the ratio of E/k are used to evaluate the general heat exchanger performance. The ratio of E/k is smaller than unit of ten at the low Reynolds number and increases greatly at high Reynolds number.
Fire Retardancy of Polymeric Materials Incorporated With Nanoscale Inclusions
Authors: Ghazinezami A. , Jabbarnia A. , Asmatulu R.
Published: April 2014

Polymeric materials have a wide variety of applications in many manufacturing industries. However, because of the molecular structures and chemical compositions of polymeric materials, they have considerably low resistances against the fire/heat. Although these materials are highly flammable, their flame retardancy can be improved significantly by incorporating with flame retardant nanomaterials. Nanoclay and nanotalc are some of the examples of the flame retardant nanomaterials which are highly cost effective and environmentally friendly for these applications. Thus, these inclusions have a great potential to improve thermal, electrical, and mechanical properties of the new materials. This study is mainly focused on the effects of nanoparticle additions in the polyvinyl chloride (PVC) in terms of the flame retardancy. Five sets of nanocomposite materials were prepared using the solvent casting method at different weight percentages of the nanomaterials. The flame retardancy values of the resultant nanocomposite samples were determined using the ASTM UL 94 standard tests. The test results were also supported with the thermogravimetric analysis (TGA) tests. Surface characterization of the resultant materials was carried out using scanning electron microscopy (SEM). Test results showed that the flame retardancy values of the new nanostructured materials were significantly enhanced in the presence of nanoscale inclusions, which may be useful for various industrial applications.
Dynamic Analysis of Bulk Acoustic Wave Piezoelectric Micropumps: Effects of Inlet-Outlet Port Angles and Overall Pump Size
Authors: Sayar Ersin , Farouk Bakhtier
Published: April 2014

Dynamic structural and fluid flow analysis of bulk acoustic wave piezoelectric valveless micropumps are carried out for the transport of water. The micropumps consist of trapezoidal prism inlet/outlet elements; the pump chamber, a thin structural layer and a piezoelectric element (PZT-5A), as the actuator. Governing equations for the flow fields and the structural-piezoelectric bi-layer membrane motions are considered. For the compressible flow formulation, an isothermal equation of state for the working fluid is employed. Two-way dynamic coupling of forces and displacements between the solid and the liquid domains in the systems are considered where actuator deflection and motion causes fluid flow and vice-versa. The effects of inlet-outlet port angles and overall pump size on the flow rate are investigated. The flow rate is found to increase with decreasing outlet convergence angle and increasing inlet divergence angle. In the second part of the present work, the size of the entire micropump is scaled to 50%, 100%, and 200% respectively while electrical parameters are kept constant.
Computational Modeling of Ducted Wind Turbines for Residential Applications
Authors: Buehrle Bridget , Kishore Ravi , Priya Shashank
Published: April 2014

As wind turbines are increasingly being adopted for meeting growing energy needs, their implementation for personal home use in the near future is imminent. There are very few studies conducted on these small-scale turbines in the one to two meter diameter range because the power generated at this scale is not sufficient to justify the cost of installation and maintenance. The problem is further complicated by the fact that these turbines are normally mounted at low altitudes and thus there is necessity to have the optimum operating regime in the wind speed range of 3–10 mph (1.34–4.47 m/s). This study analyzes the turbine performance with a diffuser at these dimensions and demonstrates the pathway that can meet these challenges. The design was modeled using commercial computational fluid dynamics code. Two-dimensional modeling using actuator disk theory was used to optimize the diffuser design. A statistical study was then conducted to reduce the computational time by selecting a descriptive set of models to test and characterize the effect of prominent parameters rather than evaluating all the possible combinations of input parameters. Individual dimensions were incorporated into JMP software and randomized to design the experiment. The results of the JMP analysis are discussed in this paper. Consistent with the literature, a long outlet section (one to three times the length of the diameter) coupled with a sharp angled inlet was found to provide the highest amplification for a wind turbine diffuser.
Finite Volume Solution of the Radiative Transfer Equation Using NVD and TVD Schemes in Unstructured Grids
Authors: Coelho P. J.
Published: April 2014

Discretization schemes based on the normalized variable diagram (NVD) and total variation diminishing (TVD) schemes are applied to the solution of the radiative transfer equation (RTE) in unstructured grids. The success of the application of these schemes to Cartesian grids has been previously demonstrated. However, their extension to unstructured grids is not straightforward. A few methods to overcome this difficulty have been proposed, and successfully applied to the solution of a scalar transport equation and to the Navier-Stokes equations. These methods are applied here to the solution of the RTE, along with a new one, recently proposed, for several test cases in which the analytical solution or other reliable numerical solutions are available for comparison. The results demonstrate that although the NVD and TVD schemes are much more accurate than the step and mean flux interpolation schemes, their order of accuracy in the case of unstructured grids is lower than in Cartesian grids. Moreover, in contrast to Cartesian grids, the NVD and TVD schemes are not strictly bounded in unstructured grids, and unphysical solutions may occur. The alternative method proposed to implement the NVD and TVD schemes is generally more accurate than previous ones, but also computationally more demanding.
Softness Measurement Technics of Human Skin by Indentation Devices Imitating Palpation
Authors: Sakuma Atsushi
Published: April 2014

The characteristics of human skin are easily changed by the states of the body because it is very sensitive to environmental transformation. And the development of the condition measurement technology of human skin is very important for improvement in QOL because it reflects body condition. Then, various devices for the condition measurement of human skin had been developed but there was no technique which can evaluate the skin by objective parameter easily.

In this paper, spherical indentation testing is studied to evaluate the dimension and rigidity of thin soft-tissues like human skin. Here, the Hertz contact theory is functionally expanded to evaluate indentations for the thin tissues. In the expansions, the technique used for evaluating the thickness of finite specimens is first explained by analyzing the experimental results of indentations. Then, the Young’s modulus of the tissue with finite thickness is theoretically derived by defining an equivalent indentation strain for the analysis of the indentation process. The expansions are examined to evaluate its reliability by applying them to measure Young’s modulus of some thin materials. Furthermore, this technology is applied to the elasticity investigation of the human skin. Especially, the measurement results of elasticity characteristics of the skin of human face are shown as the first report. The influences of sex and ultraviolet rays and so on are discussed to reveal the mechanics of human skin in this report. Moreover, it is discussed about the validity of the device which measures the elasticity of the skin of human face.
Numerical Investigations of Heat Transfer Enhancement of Water-Based Al2O3 Nanofluids in a Sinusoidal-Wall Channel
Authors: Ozbolat Veli , Sahin Besir
Published: April 2014

This research numerically investigates the heat transfer of water-Al2O3 nanofluids in a two dimensional sinusoidal wavy channel. Simulation studies are performed for fully developed flow conditions in a channel with eight waves. The temperature of the input fluid is taken to be less than that temperature of wavy walls. The governing continuity, momentum and energy equations are numerically solved using finite volume method based on SIMPLE technique. Numerical simulations were carried out for a Reynolds number ranging from 400 to 1600 and a nanofluid volume fraction, Ø where 0≤Ø≤8%. The effect of distance between channel walls are studied by varying Hmin/Hmax ratio from 0.3 to 0.5 for keeping wave length and wave amplitude values fixed. The effect of these parameters on local and average Nusselt numbers and heat transfer enhancement are presented and discussed. The results revealed that the addition of nano-particles can increase heat transfer significantly.
Performance Investigation on Single Phase Pulse Detonation Engine Using Computational Fluid Dynamics
Authors: Debnath Pinku , Pandey K. M.
Published: April 2014

Pulse detonation engines (PDEs) are new concept propulsion technologies and unsteady propulsion system that operates cyclically and typically consists of four stages, filling of fuel/air mixture, combustion, blow down and purging. Out of these four processes, combustion is the most crucial one since it produces reliable and repeatable detonation wave. Detonation is a supersonic combustion process which is essentially a shock front driven by the energy release from the reaction zone in the flow right behind it. It is based on supersonic mode of combustion and causes rapid burning of a fuel-air mixture, typically tens of thousands of times faster than in a flame, that utilize repetitive detonations to produce thrust or power. PDE offers the potential to provide increased performance while simultaneously reducing engine weight, cost, and complexity relative to conventional propulsion systems currently in service. It has the potential to drastically reduce the cost of orbit transfer vehicle system as well as space vehicle attitude control system and can be used for wide range of military, civil and commercial applications. Due to its obvious advantages, worldwide attention has been paid to the scientific and technical issues concerning PDE. The present study deals with the convergence and divergence nozzle effects on specific thrust and pressure of Pulse Detonation Engine (PDE) using computational fluid dynamics (CFD). Pulse Detonation Engine having 88.3cm length and 9.5cm diameter combustion chamber, convergence nozzle, detonation tube and divergence nozzle were design in Gambit 2.3.16. FLUENT 6.3 predict the flow physics of pressure and specific thrust (Fs), increase in divergence nozzle compared to convergence nozzle and specific thrust of detonation tube was changed with the change of flight Mach number. A three dimension computational unstructured grid was developed which gives the best meshing accuracy as well as computational results. RNG k-ε turbulence model was used for the mass flow rate, pressure and velocity contours analysis with standard wall function.
An Integrated Modeling Method to Evaluate Fleet Safety Performance of New Vehicle Designs
Authors: Samaha Randa Radwan , Prasad Priyaranjan , Marzougui Dhafer , Cui Chongzhen , Kan Cing-Dao (Steve) , Eskandarian Azim
Published: April 2014

A methodology for Evaluating Fleet, i.e., self and partner, Protection (EFP) of new vehicle designs is developed through a systems modeling approach driven by structural and occupant modeling and real world crash and full scale test data. The EFP methodology consists of a virtual model simulating the real world crash environment (i.e., different types of vehicles, impact velocities, impact directions, impact types, etc.). A concept or new vehicle design could be introduced into this model to evaluate the safety of its occupants and those of other vehicles with which it is involved in crashes. The initial implementation of EFP methodology is to frontal crashes where the modeled crash configurations are derived from a new crash taxonomy based on real world structural engagement. Simulation data to drive the methodology is obtained from finite element structural models of the vehicles. Occupant responses are based on three dimensional articulated rigid body models of the occupant and the passenger compartment. The occupant is restrained by seat belts and airbags and the structural deformations and kinematics of the passenger compartment needed to drive the occupant models are predicted by the finite element structural models. Both the structural and the occupant models are subjected to validation and robustness checks for the modeled crash configurations. The aggregate of injury risk across vehicle classes, impact speeds, occupant sizes, and crash configurations, weighted by relative frequency of the specific event in real world crashes, is used as a measure of overall societal safety. Results from a proof-of-concept application are presented.
Hollow Fiber Membrane (HFM) Facilitated CO2 Delivery to a Cyanobacteria Layer for Biofuel Production
Authors: Kalontarov Michael , Jung Erica E. , Jain Aadhar , Ahsan Syed Saad , Erickson David
Published: April 2014

Photosynthetic bacteria have been shown to be advantageous organisms for biofuel production due to high CO2 fixation efficiencies, fast growth rates, and lower water requirements. Recently, cyanobacteria been metabolically engineered to efficiently secrete their products into a surrounding solution. This has the advantage of potentially eliminating the requirement to harvest and post-process the organisms in order to extract a biofuel, which is one of the most energy and water expensive processes in most biodiesel production strategies. Lagging behind the development of these organisms however has been the development of new photobioreactor (PBR) strategies that can efficiently delivery light and inorganic carbon to the bacteria while extracting the secreted product and O2 from the solution phase. Hollow fiber membranes (HFMs) are a method for bubble-less gas exchange that has been shown to be effective at enhancing mass transfer in applications such as wastewater and landfill treatment. HFM technology could be used to overcome the mass transport challenges associated with photobioreactors. HFM modules have been used to increase mass transfer of CO2 to the bulk media in bench scale PBRs; however, the use of HFM fibers as both a mean to exchange and deliver a gas phase throughout a PBR has not been explored. We have characterized the passive transport along a single fiber in a miniature reactor in previous work. Here we extend our work to arrays of HFM fibers. We performed a range of experiments to characterize bacteria growth rate and distribution as a function fiber spacing and active transport through the fibers, and report optimized values for these variables.
Nonlinear Dynamics of Ultrasound Contrast Agent Microbubbles: Simulation and Experimentation
Authors: Carroll James M. , Burritt Sean A. , Calvisi Michael L. , Lauderbaugh Leal K.
Published: April 2014

The nonlinear response of ultrasound contrast agent microbubbles is investigated through various simulations in regimes of clinical relevance. A spherical model is used based on a compressible form of the Rayleigh-Plesset equation that is combined with a thin-shell model developed by Lars Hoff to simulate the radial response of contrast agents subject to ultrasound. The response of a Sonazoid contrast agent is analyzed through the application of techniques from dynamical systems theory such as phase portraits, Poincaré sections, bifurcation diagrams, and Lyapunov exponents to illustrate the qualitative dynamics and transition to chaos that occurs under certain changes in system parameters. The dynamic response of the contrast agent is shown to be similar regardless of the filling gas assumed or the presence of blood or water as the external medium. The effect of continuous and pulsed acoustic forcing is also compared. Furthermore, an experimental setup for investigating the dynamic response of contrast agents subject to ultrasound is presented that uses a standing acoustic wave to trap and drive bubbles at a prescribed frequency. The feasibility of the apparatus is demonstrated through high-speed images of an air bubble trapped at the antinode of the acoustic chamber.
Numerical Investigation of Natural and Forced Convection of Ionic Liquids
Authors: Paul Titan C. , Morshed A. K. M. M. , Fox Elise B. , Visser Ann E. , Bridges Nicholas J. , Khan Jamil A.
Published: April 2014

The paper focused on the numerical simulation of natural and forced convection of N-butyl-N-methylpyrrolidinium bis{trifluoromethyl)sulfonyl} imide ([C4mpyrr][NTf2]), ionic liquids (ILs). For natural convection heated from below in a square enclosure and forced convection flow through a pipe with uniform heat flux condition was considered. In numerical simulation the dimensions of the natural convection enclosure and forced convection tube are considered same as the experimental setup. Both constant and temperature dependent thermophysical properties of ILs are applied in forced convection and only temperature dependent properties are applied in natural convection simulation. The temperature dependent thermophysical properties such as density, viscosity, thermal conductivity, and heat capacity of ILs are measured experimentally. Higher accuracy was observed for temperature dependent models. The numerical results were compared with the experimental data of natural and forced convection, reported reasonably good agreements between experimental and numerical results.
Axisymmetric Model of an Intracranial Saccular Aneurysm: Theory and Computation
Authors: Curtis Colin W. , Calvisi Michael L.
Published: April 2014

An axisymmetric model of an intracranial saccular aneurysm is presented and analyzed. The model assumes a simplified spherical geometry for the aneurysm in order to develop insight into the mechanisms that effect wall shear stress and deformation of the membrane. A theoretical model is first developed based on Stokes’ equations for viscous flow in order to derive a stream function that describes vortical flow inside a sphere representative of flow inside a real aneurysm. This flow pattern is implemented in a finite element model of a spherical aneurysm using the software COMSOL Multiphysics. The results indicate close agreement between the theoretical and computational models in terms of the flow streamlines and location of the maximum wall shear stress. Furthermore, the computational model accounts for the deformation and stress of the membrane, showing regions of maximum tension and compression at opposite poles of the saccular membrane. This work elucidates many important results regarding the mechanics of saccular aneurysms and provides a basis for developing more physiologically realistic analyses.