bluuebunny/crossref_metadata_2025 huggingface dataset:
Hybrid RANS/LES Simulation of Corner Stall in a Linear Compressor Cascade
Authors: Xia Guoping , Medic Gorazd , Praisner Thomas J.
Published: July 2018

Current design-cycle Reynolds-averaged Navier–Stokes (RANS) based computational fluid dynamics (CFD) methods have the tendency to over-predict corner-stall events for axial-flow compressors operating at off-design conditions. This shortcoming has been demonstrated even in simple single-row cascade configurations. Here we report on the application of hybrid RANS/large eddy simulation (LES), or detached eddy simulation (DES), for simulating the corner-stall data from the linear compressor cascade work conducted at Ecole Centrale de Lyon. This benchmark data set provides detailed loss information while also revealing a bimodal behavior of the separation which, not surprisingly, is also not well modeled by RANS. The hybrid RANS/LES results presented here predict bimodal behavior similar to the data only when special treatment is adopted to resolve the leading-edge endwall region where the horseshoe vortex (HV) forms. The (HV) is shown to be unstable, which produces the bimodal instability. The DES simulation without special treatment or refinement in the HV region fails to predict the bimodal instability, and thus the bimodal behavior of the separation. This, in turn, causes a gross over-prediction in the scale of the corner-stall. The HV region is found to be unstable with rolling of the tertiary vortex (TV) over the secondary vortex and merging with the primary HV. With these flow dynamics realized in the DES simulations, the corner stall characteristics are found to be in better agreement with the experimental data, as compared to RANS and standard DES approaches.
Investigation on Redesigning Strategies for Water-Hammer Control in Pressurized-Piping Systems
Authors: Fersi Mohamed , Triki Ali
Published: July 2018

This paper explored and compared the effectiveness of the inline and the branching redesign strategies used to control water-hammer surges initiated into existing steel piping systems. The piping system is handled, at its transient sensitive regions, by replacing an inline, or adding a branching, short-section made of high- or low-density polyethylene (HDPE or LDPE) pipe-wall materials. The Ramos model was used to describe the transient flow, along with the method of characteristics implemented for numerical computations. The comparison of the numerical solution with experimental data available from the literature and alternative numerical solution evidenced that the proposed model could reproduce satisfactorily the magnitude and the phase shift of pressure head evolution. Further, the robustness of the proposed protection procedures was tested with regard to water-hammer up- and down-surge mechanisms, taken separately. Results demonstrated that both utilized techniques provided a useful tool to soften both water-hammer up- and down-surges. Additionally, the amortization of pressure-head-rise and -drop was sensitive to the short-section material and size. Moreover, the branching strategy illustrated several enhancements to the inline one in terms of period spread-out limitation, while providing acceptable pressure-head damping.
Influence of Rotating Directions on Hydrothermal Characteristics of a Two-Pass Parallelogram Channel With Detached Transverse Ribs
Authors: Liou Tong Miin , Chang Shyy Woei , Huang Chih Yung , An Lan I , Chan Shu Po
Published: July 2018

The detailed Nusselt number distributions on leading and trailing endwalls together with the Fanning friction factors of a rotating two-pass parallelogram ribbed channel are simultaneously measured under forward and backward rotations. The tested Reynolds number, rotation number, density ratio, and buoyancy number are respectively in the ranges of 5000 < Re < 15,000, 0 < Ro < 0.3, 0.044<Δρ/ρ < 0.2, and 0 < Bu < 0.142. The area-averaged leading and trailing Nusselt numbers at forward rotations are 0.69–1.77 and 0.85–1.98 relative to the static-channel Nusselt number references, respectively. With backward rotations, the ratios of regionally averaged Nusselt numbers between rotating and static channels for leading and trailing endwalls fall in the respective range to 0.86–2 and 0.91–1.76. At both forward and backward rotations, all the f factors over leading endwall (LE) and trailing endwall (TE) are elevated from the static-channel levels and increased by increasing Ro. Channel averaged f/f0 ratios are respectively raised to 1.21–2.21 and 1.21–2.1 at forward and backward rotations. As the heat transfer enhancements (HTE) attributed to the presence of detached transverse ribs taking precedence of the accompanying f augmentations, all the thermal performance factors are above unity in the range of 1.26–2.94. Relative to the similar rotating two-pass parallelogram channel with attached 90 deg ribs, the detached ribs generate the higher degrees of heat transfer enhancements with the larger extents of f augmentations.
Design of Three-Dimensional, Triply Periodic Unit Cell Scaffold Structures for Additive Manufacturing
Authors: Mohammed Mazher Iqbal , Gibson Ian
Published: July 2018

Highly organized, porous architectures leverage the true potential of additive manufacturing (AM) as they can simply not be manufactured by any other means. However, their mainstream usage is being hindered by the traditional methodologies of design which are heavily mathematically orientated and do not allow ease of controlling geometrical attributes. In this study, we aim to address these limitations through a more design-driven approach and demonstrate how complex mathematical surfaces, such as triply periodic structures, can be used to generate unit cells and be applied to design scaffold structures in both regular and irregular volumes in addition to hybrid formats. We examine the conversion of several triply periodic mathematical surfaces into unit cell structures and use these to design scaffolds, which are subsequently manufactured using fused filament fabrication (FFF) additive manufacturing. We present techniques to convert these functions from a two-dimensional surface to three-dimensional (3D) unit cell, fine tune the porosity and surface area, and examine the nuances behind conversion into a scaffold structure suitable for 3D printing. It was found that there are constraints in the final size of unit cell that can be suitably translated through a wider structure while still allowing for repeatable printing, which ultimately restricts the attainable porosities and smallest printed feature size. We found this limit to be approximately three times the stated precision of the 3D printer used this study. Ultimately, this work provides guidance to designers/engineers creating porous structures, and findings could be useful in applications such as tissue engineering and product light-weighting.
Finite Element Based Optimization of Human Fingertip Optical Elastography
Authors: Khan Altaf A. , Kearney Steven P. , Royston Thomas J.
Published: July 2018

Dynamic elastography methods attempt to quantitatively map soft tissue viscoelastic properties. Application to the fingertip, relevant to medical diagnostics and to improving tactile interfaces, is a novel and challenging application, given the small target size. In this feasibility study, an annular actuator placed on the surface of the fingertip and driven harmonically at multiple frequencies sequentially creates geometrically focused surface (GFS) waves. These surface wave propagation patterns are measured using scanning laser Doppler vibrometry. Reconstruction (the inverse problem) is performed in order to estimate fingertip soft tissue viscoelastic properties. The study identifies limitations of an analytical approach and introduces an optimization approach that utilizes a finite element (FE) model. Measurement at multiple frequencies reveals limitations of an assumption of homogeneity of material properties. Identified shear viscoelastic properties increase significantly as frequency increases and the depth of penetration of the surface wave is reduced, indicating that the fingertip is significantly stiffer near its surface.
Comparison of Two Models for Prediction of Seismic Streamer State Using the Ensemble Kalman Filter
Authors: Vidar Grindheim Jan , Revhaug Inge , Pedersen Egil , Solheim Peder
Published: July 2018

Towed marine seismic streamers are extensively utilized for petroleum exploration. With the increasing demand for efficiency, leading to longer and more densely spaced streamers, as well as four-dimensional (4D) surveys and more complicated survey configurations, the demand for optimal streamer steering has increased significantly. Accurate streamer state prediction is one important aspect of efficient streamer steering. In the present study, the ensemble Kalman filter (EnKF) has been used with two different models for data assimilation including parameter estimation followed by position prediction. The data used are processed position data for a seismic streamer at the very start of a survey line with particularly large cable movements due to currents. The first model is a partial differential equation (PDE) model reduced to two-dimensional (2D), solved using a finite difference method (FDM). The second model is based on a path-in-the-water (PIW) model and includes a drift angle. Prediction results using various settings are presented for both models. A variant of the PIW method gives the overall best results for the present data.
Design and Kinematic Analysis of a 3RRlS Metamorphic Parallel Mechanism for Large-Scale Reconfigurable Space Multifingered Hand
Authors: Zhao Chong , Guo Hongwei , Liu Rongqiang , Deng Zongquan , Li Bing
Published: July 2018

Capturing noncooperative targets in space has great prospects for aerospace application. In this work, the knuckle unit of a large-scale reconfigurable space multifingered hand (LSRSMFH) for multitask requirements is studied. A plurality of knuckle units is connected in series to form a finger of the LSRSMFH. First, the lockable spherical (lS) joint, a new metamorphic joint that can function as a Hooke (lS1) or spherical (lS2) joint and is driven by shape memory alloy (SMA) material, is proposed. Based on the lS joint, this paper presents a new metamorphic parallel mechanism (MPM) (i.e., 3RRlS MPM), which has four configurations, namely, 3RRlS1, 3RRlS2, 2RRlS1-RRlS2, and 2RRlS2-RRlS1 configuration. The degree-of-freedom (DOF), overconstraint, and parasitic motion of the 3RRlS MPM are analyzed using screw theory, of which the DOF can be changed from 1 to 3. The 3RRlS1 configuration has a virtual constraint, and the 3RRlS2 configuration has parasitic motions. The results indicate that the mechanism motion screws can qualitatively represent the mechanism parasitic motions, and it is verified by deriving the kinematic equation of the 3RRlS MPM based on its spatial geometric conditions, the workspace of the 3RRlS MPM is further solved. The kinematic analysis indicates that the 3RRlS MPM can realize the folding, capturing, and reconfiguring conditions of the LSRSMFH.
Analyses of Long-Term Off-Design Performance Strategy and Operation of a High-Pressure Ratio Intercooled Brayton Helium Gas Turbine Cycle for Generation IV Nuclear Power Plants
Authors: Gad-Briggs A. , Pilidis P. , Nikolaidis T.
Published: July 2018

The intercooled cycle (IC) is a simplified novel proposal for generation IV nuclear power plants (NPP) based on studies demonstrating efficiencies of over 45%. As an alternative to the simple cycle recuperated (SCR) and the intercooled cycle recuperated (ICR), the main difference in configuration is no recuperator, which reduces its size. It is expected that the components of the IC will not operate at optimum part power due to seasonal changes in ambient temperature and grid prioritization for renewable sources. Thus, the ability to demonstrate viable part load performance becomes an important requirement. The main objective of this study is to derive off-design points (ODPs) for a temperature range of −35 °C to 50 °C and core outlet temperatures (COTs) between 750 °C and 1000 °C. The ODPs have been calculated using a tool designed for this study. Based on the results, the intercooler changes the mass flow rate and compressor pressure ratio (PR). However, a drop of ∼9% in plant efficiency, in comparison to the ICR (6%) was observed for pressure losses of up to 5%. The reactor pressure losses for IC have the lowest effect on plant cycle efficiency in comparison to the SCR and ICR. Characteristic maps are created to support first-order calculations. It is also proposed to consider the intercooler pressure loss as a handle for ODP performance. The analyses brings attention to the IC an alternative cycle and aids development of cycles for generation IV NPPs specifically gas-cooled fast reactors (GFRs) and very-high-temperature reactors (VHTRs), using helium.
Effect of the Separation Distance on the Aeroacoustic Source of Multiple Shallow Cavities
Authors: Shaaban Ayman A. , Ziada Samir
Published: July 2018

Flow over ducted shallow cavities can excite fluid resonant oscillations. A common industrial application is the flow in corrugated pipes that can be modeled as a series of consecutive shallow cavities. In the current study, the effect of the separation distance on the aeroacoustic source of multiple shallow cavities is investigated. The standing wave method (SWM) is used to measure the source, where multiple microphones reconstruct the acoustic standing wave upstream and downstream of the cavities. The effect of the ratio between the separation distance to cavity length is investigated for a practical range from 0.5 to 1.375 for two- and three-cavity configurations. At low and intermediate sound levels, constructive hydrodynamic interference, resulting in a strong source, is observed for the extremum spacing ratios of 0.5 and 1.375. However, at high excitation levels, 10% and higher, the source, slightly but consistently, decreases upon increasing the separation ratio. These trends persist for both the double- and triple-cavity configurations. On the other hand, the separation distance of destructive interference is found to depend on the number of cavities of the tested configuration. Particle image velocimetry (PIV) measurements of the constructive interference cases show strong synchronized vorticity shedding in all cavities. Each cavity contribution to the total aeroacoustic source is then examined by means of Howe's analogy, and the percentage contribution of each cavity is found to depend on the excitation level.
Deposition of Variable Bead Diameter Arrays by Self-Focusing Electrohydrodynamic Jets
Authors: Martinez-Prieto Nicolas , Fratta Gabriela , Cao Jian , Ehmann Kornel F.
Published: July 2018

Electrohydrodynamic (EHD) processes were used for direct writing of bead arrays with controllable bead sizes. Experiments were conducted to align layers of bead-on-string structures in an effort to create three-dimensional patterns. The results show that the jet focuses on previously deposited droplets allowing for the selective deposition of material over already deposited patterns. Jet attraction to already deposited solutions on the substrate is attributed to the charge transport at the liquid ink–metal collector interface and the dielectric properties of the water/poly(ethylene oxide) (PEO) solution under an electric field. The deposition process consists of three steps: (1) deposition of a layer of bead-on-string structures, (2) addition of extra volume to the beads by subsequent passes of the jet, and (3) evaporation of the solvent resulting in an array of beads with varying sizes. Patterns with up to 20 passes were experimentally obtained. The beads' height was seen to be independent of the number of passes. The process reported is a simple, fast, and low-cost method for deposition of bead arrays with varying diameters.
Parameterization of Large Variability Using the Hyper-Dual Meta-Model
Authors: Bonney Matthew S. , Kammer Daniel C.
Published: July 2018

One major problem in the design of aerospace components is the nonlinear changes in the response due to a change in the geometry and material properties. Many of these components have small nominal values and any change can lead to a large variability. In order to characterize this large variability, traditional methods require either many simulation runs or the calculations of many higher-order derivatives. Each of these paths requires a large amount of computational power to evaluate the response curve. In order to perform uncertainty quantification (UQ) analysis, even more simulation runs are required. The hyper-dual meta-model (HDM) is introduced and used to characterize the response curve with the use of basis functions. The information of the response is generated with the utilization of the hyper-dual (HD) step to determine the sensitivities at a few number of simulation runs to greatly enrich the response space. This paper shows the accuracy of this method for two different systems with parameterizations at different stages in the design analysis.
Study of the Dynamic and Thermal Behaviors of an Air Flow in a T-Bifurcation
Authors: Riahi Ali , Pelle Julien , Chouchene Lilia , Harmand Souad , Ben Jabrallah Sadok
Published: July 2018

This paper presents a numerical and experimental study of a turbulent flow of air in a T-bifurcation. This configuration corresponds to a stator containing radial vents oriented vertically to the rotor–stator air gap in electrical machines. Our analysis focuses on the local convective heat transfer over the internal surface of the vents under a turbulent mass flow rate. To model the cooling installation in this region, computational fluid dynamics simulations and an experiment using particle image velocimetry (PIV) are performed. The resulting flow generally produces recirculation zones in various channels. The effect of the flow ratio and diameter of the bifurcation on the dynamic and thermal behavior of the flow is also examined. In this study, we apply a numerical approach based on the k–ω shear stress transport (SST) turbulence model (using the commercial software, “comsolmultiphysics”) to numerically solve the Navier–Stokes equations and energy equation of the system under consideration. We describe the different hypotheses necessary to formulate the equations governing the problem, initial conditions, and boundary condition. The velocity in the bifurcation calculated using the simulation is compared with that obtained by the experiment and it reveals a good agreement. The effect of the branch diameter of the bifurcation and flow ratio on the heat transfer is specifically analyzed in this research work.
Statistical Approach to Radiative Transfer in the Heterogeneous Media of Thin-Wall Morphology—I: Theory
Authors: Gusarov A. V.
Published: July 2018

Foams, three-dimensional (3D)-printed cellular and honeycomb structures, and very oblate particles dispersed in a matrix are the examples of heterogeneous media with thin-wall morphology. Phase boundaries can also be considered by this approach. Statistical description is proposed to estimate the effective radiative properties of such media. Three orientation models are studied: (i) isotropic, (ii) surface elements parallel to a plane, and (iii) surface elements parallel to an axis. Radiative transfer equations (RTEs) are obtained and analyzed in the framework of the homogeneous phase approach (HPA) and the multiphase approach (MPA). Analytical expressions are obtained for the absorption, extinction, and scattering coefficients, the scattering phase function, and the radiative thermal conductivity for very oblate particles dispersed in an absorbing scattering matrix. The reflective properties of the platelets and their preferential orientation can be used to optimize the radiative thermal conductivity.
An Adaptive Aggregation-Based Approach for Expensively Constrained Black-Box Optimization Problems
Authors: Cheng George H. , Gjernes Timothy , Gary Wang G.
Published: July 2018

Expensive constraints are commonly seen in real-world engineering design. However, metamodel based design optimization (MBDO) approaches often assume inexpensive constraints. In this work, the situational adaptive Kreisselmeier and Steinhauser (SAKS) method was employed in the development of a hybrid adaptive aggregation-based constraint handling strategy for expensive black-box constraint functions. The SAKS method is a novel approach that hybridizes the modeling and aggregation of expensive constraints and adds an adaptive strategy to control the level of hybridization. The SAKS strategy was integrated with a modified trust region-based mode pursuing sampling (TRMPS) algorithm to form the SAKS-trust region optimizer (SAKS-TRO) for single-objective design optimization problems with expensive black-box objective and constraint functions. SAKS-TRO was benchmarked against five popular constrained optimizers and demonstrated superior performance on average. SAKS-TRO was also applied to optimize the design of an industrial recessed impeller.
An Integrated Type and Dimensional Synthesis Method to Design One Degree-of-Freedom Planar Linkages With Only Revolute Joints for Exoskeletons
Authors: Shen Zefang , Allison Garry , Cui Lei
Published: July 2018

Exoskeletons can assist wearers to relearn natural movements when attached to the human body. However, most current devices are bulky and heavy, which limit their application. In this paper, we integrated type and dimensional synthesis to design one degree-of-freedom (DOF) linkages consisting of only revolute joints with multiple output joints for compact exoskeletons. Type synthesis starts from a four-bar linkage where the output link generates the first angular output. Then, an RRR dyad is connected to the four-bar linkage for the second angular output while ensuring that the overall DOF of the new mechanism is 1. A third output joint is added in a similar manner. During each step, dimensional synthesis is formulated as a constrained optimization problem and solved via genetic algorithms. In the first case study, we developed a finger exoskeleton based on a 10-bar-13-joint linkage for a natural curling motion. The second case study presents a leg exoskeleton based on an 8-bar-10-joint linkage to reproduce a natural walking gait at the hip and knee joints. We manufactured the exoskeletons to validate the proposed approach.
A Review of Ground-Effect Diffuser Aerodynamics
Authors: Ehirim O. H. , Knowles K. , Saddington A. J.
Published: July 2018

The ground-effect diffuser has become a major aerodynamic device on open-wheel racing and sports cars. Accordingly, it is widely considered to be indispensable to their aerodynamic performance, largely due to its significant downforce contribution. However, the physics and characteristics that determine how it generates downforce and its application in the auto racing industry require an in-depth analysis to develop an understanding. Furthermore, research that could generate further performance improvement of the diffuser has not been defined and presented. For these reasons, this review attempts to create a systematic understanding of the physics that influence the performance of the ground-effect diffuser. As a means of doing this, the review introduces research data and observations from various relevant studies on this subject. It then investigates advanced diffuser concepts mainly drawn from the race car industry and also proposes a further research direction that would advance the aerodynamic performance of the diffuser. It is concluded that although the diffuser will continue to be paramount in the aerodynamic performance of racing cars, research is needed to identify means to further enhance its performance.
Fuel Stratification and Partially Premixed Combustion With Neat n-Butanol in a Compression Ignition Engine
Authors: Dev Shouvik , Gao Tongyang , Yu Xiao , Ives Mark , Zheng Ming
Published: July 2018

Homogeneous charge compression ignition (HCCI) has been considered as an ideal combustion mode for compression ignition (CI) engines due to its superb thermal efficiency and low emissions of nitrogen oxides (NOx) and particulate matter. However, a challenge that limits practical applications of HCCI is the lack of control over the combustion rate. Fuel stratification and partially premixed combustion (PPC) have considerably improved the control over the heat release profile with modulations of the ratio between premixed fuel and directly injected fuel, as well as injection timing for ignition initiation. It leverages the advantages of both conventional direct injection compression ignition and HCCI. In this study, neat n-butanol is employed to generate the fuel stratification and PPC in a single cylinder CI engine. A fuel such as n-butanol can provide additional benefits of even lower emissions and can potentially lead to a reduced carbon footprint and improved energy security if produced appropriately from biomass sources. Intake port fuel injection (PFI) of neat n-butanol is used for the delivery of the premixed fuel, while the direct injection (DI) of neat n-butanol is applied to generate the fuel stratification. Effects of PFI-DI fuel ratio, DI timing, and intake pressure on the combustion are studied in detail. Different conditions are identified at which clean and efficient combustion can be achieved at a baseline load of 6 bar IMEP. An extended load of 14 bar IMEP is demonstrated using stratified combustion with combustion phasing control.
Experimental Investigation of Fuel Anti-Knock-Index Requirements in Three Small Two-Stroke Engines for Remotely Piloted Aircraft
Authors: Ausserer Joseph K. , Polanka Marc D. , Litke Paul J. , Baranski Jacob A.
Published: July 2018

Small remotely piloted aircraft (10–25 kg) that are powered by internal combustion engines typically operate on gasoline with an anti-knock index (AKI) > 80. To comply with the single-battlefield-fuel initiative [Department of Defense (DoD) Directive 4140.25], interest has increased in converting power plants for these platforms to run on low-AKI fuels such as diesel and Jet-A with AKIs of ∼20. It has been speculated that the higher losses (short circuiting, incomplete combustion, heat transfer) that cause these engines to have lower efficiencies than their conventional-scale counterparts may also relax their required fuel AKI. The fuel-AKI requirements of three two-stroke spark ignition (SI) engines with 28, 55, and 85 cm3 displacements were mapped, and the performance was compared to that on 98 ON (octane number) fuel. Switching from 98 ON fuel to 20 ON (Jet-A and diesel equivalent AKI) fuel while maintaining optimum combustion phasing led to a 3–5 crank-angle degree (CAD) reduction in burn angle, a 2–3% increase in power, and a 0.5–1% (absolute) increase in fuel-conversion efficiency at non-knock-limited conditions through shortening of the CA0–CA10 burn angle. The efficiency improvement translates to a 6% increase in range or endurance. The results indicate that abnormal combustion is not a significant obstacle to operating small commercial-off-the-shelf (COTS) engines on low-AKI fuels and that most of the power and efficiency improvements demonstrated in previous heavy-fuel conversion efforts were the result of modifications made to accommodate low-volatility fuels, not the faster burn rate of the low-AKI fuels themselves.
Process Design of Cyclic Water Flooding by Real-Time Monitoring
Authors: Pourabdollah Kobra
Published: July 2018

The gradual decline in the oil production rate of water flooded reservoirs leads to decrease in the profit of water flooding system. Although cyclic water injection (CWI) was introduced to reduce the descending trend of oil production in water flooded reservoirs, it must be optimized based upon the process parameters. The objective of this study is to develop all process design criteria based upon the real-time monitoring of CWI process in a naturally fractured reservoir having five producing wells and five injector wells completed in an Arab carbonated formation containing light crude oil (API = 42 deg). For this aim, a small pilot oil field was selected with water injection facilities and naturally producing oil wells and all data were collected from the field tests. During a five years' field test, the primary observations at the onset of shutdown periods of the water injection system revealed a repeatable significant enhancement in oil production rate by a factor of plus 5% leading us to assess the application of CWI. This paper represents the significant parameters of pressure and productivity affected during CWI in naturally fractured carbonate reservoirs based upon a dual porosity generalized compositional model. The results hopefully introduce other oil producer companies to the potential of using CWI to increase oil production in conventional water injection systems. The results also outline situations where such applications would be desirable.
Production of Al Metal Matrix Composites Reinforced With Carbon Nanotubes by Two-Stage Melt-Based HPDC-CE Method
Authors: Larianovsky Natalya , Popov Vladimir , Katz-Demyanetz Alexander , Fleisher Alex , Meyers Douglas E. , Chaudhuri Ray S.
Published: July 2018

Carbon nanotubes (CNTs) are well known as perfect reinforcement for high strength and lightweight composites due to their high specific strength, thermal, electrical, and mechanical characteristics. One of the important challenges is to obtain a homogeneous dispersion of CNTs in metal matrix, so development technologies for producing metal matrix composites (MMCs) is of great interest. Melting followed by solidification, may be successfully utilized for synthesizing CNT-reinforced aluminum-based MMCs. In this study, Al/CNT composites have been produced by direct injection of CNTs in pure aluminum using high-pressure die casting (HPDC) method. The as-produced billets were subjected to cyclic extrusion (CE) to refine CNT agglomerates and to increase CNT dispersion in aluminum. Current investigation demonstrates that more than 50% efficiency of combined HPDC-CE production method has been achieved. The resulting composites demonstrated improved mechanical properties.
Scalable Manufacturing of AgCu40(wt %)–WC Nanocomposite Microwires
Authors: Guan Zeyi , Hwang Injoo , Pan Shuaihang , Li Xiaochun
Published: July 2018

Nanoparticle reinforced metals recently emerge as a new class of materials to empower the functionality of metallic materials. There is a remarkable success in self-incorporation of nanoparticles to bulk metals for extraordinary properties. There is also a strong demand to use nanoparticles to enhance the performance of metallic microwires for exciting opportunities in numerous applications. Here, we show for the first time that silver–copper alloy (AgCu) reinforced by tungsten carbide (WC) (AgCu40 (wt %)–WC) was manufactured by a stir casting method utilizing a nanoparticle self-dispersion mechanism. The nanocomposite microwires were successfully fabricated using thermal drawing method. By introducing WC nanoparticles into bulk AgCu40 alloy, the Vickers microhardness was enhanced by 63% with 22 vol % WC nanoparticles, while the electrical conductivity dropped to 20.1% International Annealed Copper Standard (IACS). The microwires of AgCu40–10 vol % WC offered an ultimate tensile strength of 354 MPa, an enhancement of 74% from the pure alloy, and an elongation of 5.2%. The scalable manufacturing method provides a new pathway for the production of metallic nanocomposite micro/nanowires with outstanding performance for widespread applications, e.g., in biomedical, brazing, and electronics industries.
A Study of On-Machine Micro Milling Cutter Condition Inspection Based on Machine Vision
Authors: Zhang Xi , Shi Yuanyuan , Zhang Benzheng , Si Chunying
Published: July 2018

In order to inspect the condition of micro milling cutter automatically and accurately in the online process, a dedicated micro milling cutter condition inspection system was established in this paper, which can effectively inspect micro cutter condition from both radial and axial direction. The key methods—the automatic dimension measurement and the fusion method for compositing all-in-focus cutting edge image of micro milling cutters—are studied. The experiments verify that the proposed methods and the developed inspection system can fulfill the needs of industrial applications.
A Validation/Uncertainty Quantification Analysis for a 1.5 MW Oxy-Coal Fired Furnace: Sensitivity Analysis
Authors: Díaz-Ibarra Oscar H. , Spinti Jennifer , Fry Andrew , Isaac Benjamin , Thornock Jeremy N. , Hradisky Michal , Smith Sean , Smith Philip J.
Published: July 2018

A validation/uncertainty quantification (VUQ) study was performed on the 1.5 MWth L1500 furnace, an oxy-coal fired facility located at the Industrial Combustion and Gasification Research Facility at the University of Utah. A six-step VUQ framework is used for studying the impact of model parameter uncertainty on heat flux, the quantity of interest (QOI) for the project. This paper focuses on the first two steps of the framework. The first step is the selection of model outputs in the experimental and simulation data that are related to the heat flux: incident heat flux, heat removal by cooling tubes, and wall temperatures. We describe the experimental facility, the operating conditions, and the data collection process. To obtain the simulation data, we utilized two tools, star-ccm+ and Arches. The star-ccm+ simulations captured flow through the complex geometry of the swirl burner while the Arches simulations captured multiphase reacting flow in the L1500. We employed a filtered handoff plane to couple the two simulations. In step two, we developed an input/uncertainty (I/U) map and assigned a priority to 11 model parameters based on prior knowledge. We included parameters from both a char oxidation model and an ash deposition model in this study. We reduced the active parameter space from 11 to 5 based on priority. To further reduce the number of parameters that must be considered in the remaining steps of the framework, we performed a sensitivity analysis on the five parameters and used the results to reduce the parameter set to two.
Bone Remodeling Under Vibration: A Computational Model of Bone Remodeling Incorporating the Modal Behavior of Bone
Authors: Ostadi Moghaddam A. , Mahjoob M. J. , Nazarian A.
Published: July 2018

Developing precise computational models of bone remodeling can lead to more successful types of orthopedic treatments and deeper understanding of the phenomenon. Empirical evidence has shown that bone adaptation to mechanical loading is frequency dependent, and the modal behavior of bone under vibration can play a significant role in remodeling process, particularly in the resonance region. The objective of this study is to develop a bone remodeling algorithm that takes into account the effects of bone vibrational behavior. An extended/modified model is presented based on conventional finite element (FE) remodeling models. Frequency domain analysis is used to introduce appropriate correction coefficients to incorporate the effect of bone's frequency response (FR) into the model. The method is implemented on a bovine bone with known modal/vibration characteristics. The rate and locations of new bone formation depend on the loading frequency and are consistently correlated with the bone modal behavior. Results show that the proposed method can successfully integrate the bone vibration conditions and characteristics with the remodeling process. The results obtained support experimental observations in the literature.
An Analytical Poroelastic Model of a Nonhomogeneous Medium Under Creep Compression for Ultrasound Poroelastography Applications—Part II
Authors: Islam Md Tauhidul , Reddy J. N. , Righetti Raffaella
Published: July 2018

An analytical theory for the unconfined creep behavior of a cylindrical inclusion (simulating a soft tissue tumor) embedded in a cylindrical background sample (simulating normal tissue) is presented and analyzed in this paper. Both the inclusion and the background are considered as fluid-filled, porous materials, each of them being characterized by a set of mechanical parameters. Specifically, in this derivation, the inclusion is assumed to have significantly higher interstitial permeability than the background. The formulations of the effective Poisson's ratio (EPR) and fluid pressure in the inclusion and in the background are derived for the case of a sample subjected to a creep compression. The developed analytical expressions are validated using finite element models (FEM). Statistical comparison between the results obtained from the developed model and the results from FEM demonstrates accuracy of the proposed theoretical model higher than 99.4%. The model presented in this paper complements the one reported in the companion paper (Part I), which refers to the case of an inclusion having less interstitial permeability than the background.
Numerical Study and Optimization of Corrugation Height and Angle of Attack of Vortex Generator in the Wavy Fin-and-Tube Heat Exchanger
Authors: Li Wei , Khan Tariq Amin , Tang Weiyu , Minkowycz W. J.
Published: July 2018

Wavy fins have been considered as an alternative of the straight fins in compact heat exchangers (CHEs) for better heat transfer performance, which can be augmented by considering vortex generators (VGs). This work is related to numerical investigation and optimization of corrugation height of fin and angle of attack of delta winglet type VGs in a wavy fin-and-tube heat exchanger. For this purpose, three-dimensional (3D) Reynolds-averaged Navier-Stokes analysis and a multi-objective genetic algorithm (MOGA) with surrogate modeling are performed. Numerical simulation is carried out to study the effect of delta winglets with varying the corrugation height of wavy fin in three rows of tubes with staggered tube arrangements. The corrugation height (H) and angle of attack (α) vary from 0.3 mm to 1.8 mm and 15 deg to 75 deg, respectively. Results are illustrated by investigating the flow structures and temperature contours. Results show that increasing the corrugation height of wavy fin and angle of attack of delta winglets enhances the heat transfer performance of heat exchanger while friction factor is also increased. Employing delta winglets has augmented the thermal performance for all corrugation heights and superior effect is observed at a higher corrugation. To achieve a maximum heat transfer enhancement and a minimum pressure drop, the optimal values of these parameters (H and α) are calculated using the Pareto optimal strategy. For this purpose, computational fluid dynamics (CFD) data, a surrogate model (neural network), and a multi-objective GA are combined. Results show that optimal orientation of delta winglets with respect to corrugation height can improve both the thermal and hydraulic performance of the heat exchanger.
Forced Convective Heat Transfer in a Channel Filled With a Functionally Graded Metal Foam Matrix
Authors: Bai Xiaohui , Kuwahara Fujio , Mobedi Moghtada , Nakayama Akira
Published: July 2018

Fully developed forced convective heat transfer within a channel filled with a functionally graded metal foam matrix was investigated analytically for the case of constant wall heat flux. A series of functionally graded metal foam matrices of the same mass (i.e., the same solidity) were examined in views of their heat transfer performances. The porosity either increases or decreases toward the heated wall following a parabolic function. Among the metal foam matrices of the same mass, the maximum heat transfer coefficient exists for the case in which the porosity decreases toward the heated wall (i.e., more metal near the wall). The heat transfer coefficients in such channels filled with a functionally graded metal foam matrix are found 20–50% higher than that expected from the increase in the effective thermal conductivity. Hence, functionally graded metal foam matrices are quite effective to achieve substantially high heat transfer coefficient with an acceptable increase in pressure drop.
Investigation of Mixed Convection Heat Transfer Through Metal Foams Partially Filled in a Vertical Channel by Using Computational Fluid Dynamics
Authors: Kotresha Banjara , Gnanasekaran N
Published: July 2018

Two-dimensional computational fluid dynamics simulations of mixed convection heat transfer through aluminum metal foams partially filled in a vertical channel are carried out numerically. The objective of the present study is to quantify the effect of metal foam thickness on the fluid flow characteristics and the thermal performance in a partially filled vertical channel with metal foams for a fluid velocity range of 0.05–3 m/s. The numerical computations are performed for metal foam filled with 40%, 70%, and 100% by volume in the vertical channel for four different pores per inch (PPIs) of 10, 20, 30, and 45 with porosity values varying from 0.90 to 0.95. To envisage the characteristics of fluid flow and heat transfer, two different models, namely, Darcy Extended Forchheirmer (DEF) and Local thermal non-equilibrium, have been incorporated for the metal foam region. The numerical results are compared with experimental and analytical results available in the literature for the purpose of validation. The results of the parametric studies on vertical channel show that the Nusselt number increases with the increase of partial filling of metal foams. The thermal performance of the metal foams is reported in terms of Colburn j and performance factors.
The Effects of Designers' Contextual Experience on the Ideation Process and Design Outcomes
Authors: Hu Wan-Lin , Reid Tahira
Published: July 2018

Personal context-specific experience can affect how a designer evaluates a design problem and proposes solutions. However, this effect was seldom discovered in a quantitative manner in problem-solving design tasks. This paper uses empirical evidence and quantitative methods to show the effects of novice designers' contextual experience on design tasks, particularly as it relates to the design process and design outcomes. Thirty-three people performed two design tasks while their cognitive states were assessed using electroencephalography (EEG). Moreover, the objective ratings (i.e., quantity, novelty and quality) from prospective users were analyzed to gauge the effect of contextual experience on design outcomes. Results suggest that during ideation, contextual experience has a negative effect on mental states associated with creativity and also on the novelty evaluations of the proposed solutions in the tested design tasks. This research advances the development of design methods for novice designers.
Magnetohydrodynamic Mixed Convective Flow Due to a Vertical Plate With Induced Magnetic Field
Authors: Nandkeolyar R. , Narayana M. , Motsa S. S. , Sibanda P.
Published: July 2018

The steady hydromagnetic flow of a viscous, incompressible, perfectly conducting, and heat absorbing fluid past a vertical flat plate under the influence of an aligned magnetic field is studied. The flow is subject to mixed convective heat transfer. The fluid is assumed to have a reasonably high magnetic Prandtl number which causes significant-induced magnetic field effects. Such fluid flows find application in many magnetohydrodynamic devices including MHD power-generation. The effects of viscous dissipation and heat absorption by the fluid are investigated. The governing nonlinear partial differential equations are converted into a set of nonsimilar partial differential equations which are then solved using a spectral quasi-linearization method (SQLM). The effects of the important parameters on the fluid velocity, induced magnetic field, fluid temperature and as well as on the coefficient of skin-friction and the Nusselt number are discussed qualitatively.
Planning the Selection and Assignment of Security Forensics Countermeasures
Authors: Bajramovic Edita , Bochtler Jürgen , Zid Ines Ben , Lainer Andreas
Published: July 2018

Cybersecurity incidents are stressful, complex in nature, and are frequently not systematically considered in daily tasks. When correctly managed, operational readiness procedures ensure the availability of data required to successfully and quickly recover from a security incident, while lessening the adverse effect. Therefore, protective measures, such as implementation of data diodes, are playing an essential role in defending instrumentation and control (I&C) systems. In addition, applicability of the newest forensic and digital evidence-related standards to the nuclear domain is being evaluated. Results of such evaluation are being considered in the three-dimensional and two-dimensional modeling of cybersecurity relevant assets. The development of the new IEC 63096, downstream standard of IEC 62645, will also support the proposed evaluation and modeling. However, IEC 63096 covers not only forensic and incident management-related security controls but also a broad range of cybersecurity controls. This paper will further explore the security degree-specific selection and overall assignment of forensic-related security controls for the nuclear domain. Results from ongoing prototype developments will be used to demonstrate possible alternative selections and assignments, along with their contribution to different security metrics.
Seismic Damage at the Fukushima Daiichi Nuclear Power Station With Emphasis on Unit 1
Authors: Akimoto Kazuhiro
Published: July 2018

This paper analyzes and reviews various seismic damage at the Fukushima Daiichi Nuclear Power Station (F1) caused by the Great East Japan Earthquake (the Earthquake) on March 11 in 2011. Moreover, descriptions of various F1 accident reports on on-site seismic damage are comparatively analyzed. At first, impacts of the Earthquake and tsunami as well as damage at four influenced Nuclear Power Stations (NPSs), including F1, are comparatively analyzed. Although no safety-related equipment were seismically damaged at F1, there occurred various on-site seismic damage which should be learned at NPSs worldwide in preparation for next possible beyond-design-basis disasters. Particularly damaged were the main administration building as well as various on-site high-voltage equipment to receive off-site electric power. Owing largely to this on-site damage F1 lost the off-site power, eventually leading the entire NPS to station black-out. Other on-site seismic damage includes loss of an emergency data transmission system, roads, coolant water tanks, leakage of radio-contaminated water from spent fuel pools (SFP), presumably the Unit-1/2 exhaust stack among others.
Numerical
Investigation on the Modified Bend Geometry of a Rotating Multipass Internal Cooling Passage in a
Gas Turbine Blade
Authors: Pattanaprates Naris , Juntasaro Ekachai , Juntasaro Varangrat
Published: July 2018

The present work is aimed to investigate whether the modification to the bend geometry of a multipass internal cooling passage in a gas turbine blade can enhance heat transfer and reduce pressure drop. The two-pass channel and the four-pass channel are modified at the bend from the U shape to the bulb and bow shape. The first objective of the work is to investigate whether the modified design will still improve heat transfer with reduced pressure drop in a four-pass channel as in the case of a two-pass channel. It is found out that, unlike the two-pass channel, the heat transfer is not improved but the pressure drop is still reduced for the four-pass channel. The second objective is to investigate the rotating effect on heat transfer and pressure drop in the cases of two-pass and four-pass channels for both original and modified designs. It is found out that heat transfer is improved with reduced pressure drop for all cases. However, the modified design results in the less improvement on heat transfer and lower reduced pressure drop as the rotation number increases. It can be concluded from the present work that the modification can solve the problem of pressure drop without causing the degradation of heat transfer for all cases. The two-pass channel with modified bend results in the highest heat transfer and the lowest pressure drop for rotating cases.