bluuebunny/crossref_metadata_2025 huggingface dataset:
Superficial keratectomy as a treatment for non‐healing corneal ulceration associated with primary corneal endothelial degeneration
Authors: Bayley Kellam D. , Read R. A. , Gates M. Carolyn
Published: October 2018

Objective

To analyze a study population of dogs with primary corneal endothelial degeneration (PCED) for information on the patterns of disease and to report the efficacy of superficial keratectomy (SK) for resolution of non‐healing corneal ulcers associated with PCED.

Animals studied

Primary corneal endothelial degeneration was diagnosed in 238 dogs between 1998 and 2017. Corneal ulceration associated with PCED was present in 89 dogs (109 eyes), of which 47 eyes were treated with SK.

Procedures

A retrospective assessment of medical records was performed to determine the signalment patterns of PCED, and the success rate of the SK procedure for resolving PCED‐associated corneal ulceration. Descriptive statistics were reported on the signalment of PCED cases, with odd ratios and confidence intervals calculated to detect breed predispositions.

Results

Primary corneal endothelial degeneration was diagnosed in 238 dogs, 40.8% were female and 59.2% were male, with a mean age at diagnosis of 11.4 years. Dachshunds, Dalmatians, English Springer Spaniels, Welsh Springer Spaniels, Chihuahuas, Cocker Spaniels, and Golden Retrievers were significantly over‐represented. All PCED‐affected Dalmatians developed associated corneal ulceration. Follow‐up information was available for 41/47 eyes treated with SK. At the first reassessment, 87.8% were healed which increased to 97.6% with subsequent monitoring. Four eyes (9.8%) had late corneal ulcer occurrence following SK, at a median time following SK of 182 weeks post‐surgery.

Conclusions

Superficial keratectomy was an effective option for resolving painful non‐healing corneal ulcers associated with PCED. Dalmatians may be at increased risk of developing PCED‐associated corneal ulceration.
Comparison of pollution diffusion between river mouth inflow (RMI) and beach uniform inflow (BUI) in sudden water accident
Authors: Pan Fanghui , Wang Youbao , Zhang Xinxi , Huang Junsheng , Jiang Yongbin , Hu Xiaobing , Li Sheng
Published: October 2018

Recently high‐frequency sudden pollution originated from an explosion of industrial plants, transportation accidents and oil spills was often continuously diffused into downstream water. In this paper, the features of pollution diffusion including the boundary shape, concentration gradients and covered area from the two typical sudden water accidents of river mouth inflow (RMI) and beach uniform inflow (BUI) were investigated and compared by utilizing computational fluid dynamic (CFD) model and lab‐scale experiments. It was found that a circular boundary shape was formed when diffusion velocity was slower than threshold velocity of 0.0016 m/s, however, a long strip of boundary was replaced at the speed of more than 0.0016 m/s from RMI, using CFD simulation under lab‐scale. The coincidence degree of diffusion over time in terms of covered area and boundary shape between CFD simulation and the lab‐scale experiment was reached to 97.6–99.6% both in RMI and BUI. The result indicated that CFD was applied to simulate the pollution diffusion from the two patterns of sudden water accidents under full‐scale. Results showed that a sharp peak was capable of appearing in mainstream and there was a ring current appearing in side wing from RMI. However, the mainstream with a gentle peak and the side wing with symmetrical diffusion were arising in BUI. In addition, a high concentration gradients and a clear concentration contours were both exhibited in RMI and BUI. The results may assist in offering emergency response to control sudden pollution diffusion, further supporting the scope of pollution hazard assessment and ecological remediation to recover pollution region.
Water footprint assessment considering intermediate products: model and a 2016 case study of China
Authors: Zhi Yuan , Hamilton Paul B. , Wang Xiufeng , Liang Longyue
Published: October 2018

Analysing intermediate products within a water footprint (WF) across different economic sectors can show the root causes of water usage and is helpful for water resource management and policy making. However, conventional methods and data for a WF rarely assess the input and output of intermediate products directly and comprehensively. Therefore, this study proposes an approach to access the WF of intermediate products as well as final products in each sector of an economy’s water sustainability profile. An Economic Input‐output‐based Life‐Cycle Assessment (EIO‐LCA) framework is designed for the accounting, which describes the intermediate WF products of each sector in a material‐product network. This method is implemented into a 2016 case study for a comprehensive Chinese WF. The results showed that the total WF of Chinese inhabitants (consumers) in 2016 was 5.76 × 1011 m3, and the top three sectors with the largest WF were agriculture (1.78 × 1011 m3), food (1.05 × 1011 m3) and machinery manufacturing (5.68 × 1010 m3); agriculture provided the largest quantity of virtual water contained in its intermediate product for the other sectors. From the perspective of producers, the total WF of the Chinese economic sectors in 2016 was 5.84 × 1011 m3. The sectors with the largest direct water use were agriculture (2.20 × 1011 m3), electricity (7.64 × 1010 m3) and chemical Industry (2.35 × 1010 m3); and large parts of their direct water usage were consumed to prepare intermediate products for other sectors. The results of this study show that a more inclusive approach provides an enhanced qualitative and resource‐ethical view for water accounting and management.
Guaranteeism in Administrative Acts
Authors: Rabell-Garcia Enrique
Published: October 2018

Under the reform of article 1 of the Federal Constitution (June 10, 2011), all government authorities have the obligation to respect human rights. The main inquiry of this essay is whether the Executive can, ex officio, revoke administrative acts for violations of human rights or stop enforcing a law it deems unconstitutional. Following this line of inquiry, for the purposes of this essay, the hypothesis is affirmative. The first part of this work analyzes several techniques and their comprehensive interpretation. Doctrine and comparative law are used to frame the issue. The second part consists of a constitutional analysis of article one under several legal interpretation theories to obtain preliminary results. The third part focuses particularly on revocation in the Administrative Procedure Act and the Mexican Federal Tax Code, in addition to relevant case law. Lastly, it is concluded that, in certain cases involving legal certainty, revocation can apply; however, refusal to enforce a law deemed unconstitutional cannot.
‘Emprender sin descuidar la casa’: posiciones y dinámicas organizativas en una asociación productiva de mujeres rurales
Authors: Mora Guerrero Gloria Miryam , Constanzo Belmar Jorge Dagoberto
Published: October 2018

El presente estudio explora el proceso de conformación de un emprendimiento de tipo asociativo por mujeres rurales, al igual que su relación con los roles de género en el ámbito doméstico. Por medio de observaciones participantes y entrevistas, se trabajó con usuarias del Programa de Formación y Capacitación para Mujeres Campesinas, en La Araucanía, región que se localiza en el sur de Chile. Conforme con un corpusteórico de enfoque constructivista, se caracterizaron las diferentes posiciones que ocupan las mujeres al interior de sus organizaciones, según la forma como articulan su rol asociativo con la división sexual del trabajo tradicional en sus grupos familiares. En ese sentido, las conclusiones alientan la generación de metodologías que fomenten la participación de las mujeres en emprendimientos asociativos, y consideren a la vez sus intereses y colocaciones en las estructuras de género de las zonas rurales.
Neumonía adquirida en la comunidad: una revisión narrativa
Authors: Martínez Vernaza Samuel , Soto Chavez Maria Juliana , Mckinley Estefania , Gualtero Trujillo Sandra
Published: October 2018

La neumonía adquirida en la comunidad (NAC) continúa siendo una de las principales causas de mortalidad en Colombia, pues es responsable de 13 de cada 100.000 muertes. Su principal agente etiológico es el Streptococcus pneumoniae, seguido por Haemophilus influenzae y Staphylococcus aureus. Se han identificado algunos factores de riesgo como comorbilidades y factores de exposición epidemiológica, los cuales incrementan la posibilidad de contraer una infección por microrganismos específicos. Su diagnóstico debe basarse tanto en la clínica como en hallazgos paraclínicos e imagenológicos. Herramientas como las escalas CURB-65 y PSI asociadas al criterio clínico permiten calcular el riesgo de mortalidad y el área de atención del paciente según su clasificación. En esta revisión se consideran los diferentes elementos para una adecuada evaluación y manejo del paciente que cursa con NAC, el uso de algunos biomarcadores, situaciones especiales para apreciar, como la neumonía severa, y estrategias para una adecuada prevención.
Incidence of Acute Pyelonephritis in Hospitalized Children under 5 Years Old with Positive Urine Culture
Authors: Castaño González Alexandra , Ruiz Peláez Juan Gabriel
Published: October 2018

Introduction: Urinary tract infection is a major cause of child morbidity. The diagnosis of acute pyelonephritis is important to decide the treatment. Methods: Retrospective observational study. We collected information of urinalysis, urine Gram and urine culture of hospitalized children between 3 months and 5 years old, with suspected urinary tract infection between January 2008 and December 2010. In patients with positive urine culture, the results of renal scintigraphy (Gamma scan) were evaluated to estimate the incidence of acute pyelonephritis. Results: We identified 1,463 medical records. Urinary culture was obtained in 237 patients, of whom 54.4% were positive. Renal scintigraphy was obtained in 93 of these patients and 59.1% were positive. Conclusions: The incidence of acute pyelonephritis in patients with confirmed urinary tract infection was 59.1%.
Nonlinear Series-Type Tuned Mass Damper-Tuned Sloshing Damper for Improved Structural Control
Authors: Love J. S. , Lee C. S.
Published: October 2018

A novel type of dynamic vibration absorber (DVA) is proposed, which consists of a tuned mass damper (TMD) and tuned sloshing damper (TSD) connected in series to the structure. The system enables the expensive viscous damping devices (VDDs) associated with traditional TMDs to be omitted from the design. A linearized equivalent mechanical model and a nonlinear multimodal model are developed to investigate the proposed system. A TMD–TSD is nonlinear due to the quadratic damping associated with liquid drag, which ensures the system performance is amplitude-dependent. Simple expressions for the optimal TSD–TMD mass ratio, tuning, and damping ratios are employed to design a TMD–TSD coupled to a single degree-of-freedom (SDOF) structure. Frequency response curves for the structure, TMD, and TSD degrees-of-freedom are created for several excitation amplitudes, and the nonlinear behavior of the system response is evident. The performance of the TMD–TSD is evaluated against traditional TMD and TSD systems—with the same total mass—by computing the effective damping produced by each system. The proposed system is found to provide a superior acceleration reduction performance and superior robustness against changes to the frequency of the primary structure. The proposed system is, therefore, an effective and affordable means to reduce the resonant response of tall buildings.
Application of the Transient Heat Transfer Measurement Technique Using Thermochromic Liquid Crystals in a Network Configuration With Intersecting Circular Passages
Authors: Steurer Anika , Poser Rico , von Wolfersdorf Jens , Retzko Stefan
Published: October 2018

The present study deals with the application of the transient thermochromic liquid crystal (TLC) technique in a flow network of intersecting circular passages as a potential internal turbine component cooling geometry. The investigated network consists of six circular passages with a diameter d = 20 mm that intersect coplanar at an angle θ = 40 deg, the innermost in three, the outermost in one intersection level. Two additional nonintersecting passages serve as references. Such a flow network entails specific characteristics associated with the transient TLC method that have to be accounted for in the evaluation process: the strongly curved surfaces, the mixing and mass flow redistribution at each intersection point, and the resulting gradients between the wall and passage centerline temperatures. All this impedes the choice of a representative fluid reference temperature, which results in deviations using established evaluation methods. An alternative evaluation approach is introduced, which is supported by computational results obtained from steady-state three-dimensional (3D) Reynolds-averaged Navier–Stokes equations (RANS) simulations using the shear-stress transport (SST) turbulence model. The presented analysis uncouples local heat transfer (HT) coefficients from actually measured local temperatures but uses the time information of the thermocouples (TC) instead that represents the fluid temperature step change and evolution along the passages. This experimental time information is transferred to the steady-state numerical bulk temperatures, which are finally used as local references to evaluate the transient TLC experiments. As effective local mass flow rates in the passage sections are considered, the approach eventually allows for a conclusion whether HT is locally enhanced due to higher mass flow rates or the intersection effects.
A New Observer Design for Aging Detection of Supercapacitors
Authors: Magarotto E. , Massieu J.-F. , Dorléans P. , Oukaour A.
Published: October 2018

In this paper, a new aging detection method of a supercapacitor is proposed through the study of the charge process. Good indicators to describe this aging are equivalent series resistance (ESR) and capacitance evolution, which are online unmeasurable parameters of the component model. The proposed model belongs to the class of state and parameter affine nonlinear system. A new adaptive nonlinear observer is designed to estimate, under different aging phases, both states and parameters using measurements only available at each sampling instant. This unusual observer contains an adaptive gain, an unknown parameter into the measured output equation, and the control signal into state matrix. This discrete-continuous observer is proved to be globally exponentially convergent under some sufficient conditions. Theoretical results are implemented for two cases of study, the first one through some simulations and the second one applied on real data for different sampling times and different values of observer gain. Results highlight good performances of the observer in online parameter estimation; thus, the component aging is clearly shown.
Thermophoresis of Nanoparticles in Dilute Gases
Authors: Wang Jun , Xia Guodong
Published: October 2018

The thermophoresis of nanoparticles in the free molecule regime plays an important role in the nucleation, collision and coagulation of nanoparticles. In this contribution, on the basis of a rigorous gas kinetic theory, the theoretical expressions for the thermophoretic force on nanoparticles suspended in dilute gas mixtures are derived, wherein the non-rigid-body interactions between the gas molecules and the nanoparticle are taken into account. The analytical formulas in the present work are consistent with those under the rigid-body collision assumption. Negative thermophoresis, is found to be possible for nanoparticles in the free molecule regime, by which the thermophoretic force exerted on the suspended nanoparticle is from low to high temperature, i.e., opposite to the direction of normal thermophoresis.
Simulation of Incompressible Multiphase Flows Using the Artificial Compressibility Method
Authors: Mortezazadeh Mohammad , Hejranfar Kazem
Published: October 2018

The Eulerian methods are susceptible to generate the nonphysical spurious currents in the multiphase flow simulations near the interfaces. This paper presents a new Eulerian method to accurately simulate the velocity fields, especially near the multiphase flow interfaces and prevents the numerical results from generating the nonphysical currents. A Eulerian central difference finite-volume scheme equipped with the suitable numerical dissipation terms is used to simulate incompressible multiphase flows. The interface is captured by Flux Corrected Transport-Volume of Fluid method (FCT-VOF). Increasing the accuracy near the sharp gradients, such as interface, the conservative form of incompressible Navier-Stokes equations is solved to locally conserve the properties. The main feature of this algorithm is its ability to control the pressure gradient oscillation and also spurious currents near the interface; two common problems in multiphase flow simulations, and as a result improves the accuracy of the simulation by artificial numerical dissipations. The results show the FCT-VOF is able to precisely calculate the interface, and the numerical dissipation terms are the powerful device to prevent the spurious currents.
Status Review for the Prediction Methods of the Radial Force Caused by a Centrifugal Pump or Volute During Off-Design-Point Operation
Authors: Messele Mekuannint , Engeda Abraham
Published: October 2018

Volutes are often used on the discharge of a centrifugal pump and compressor to provide efficient gathering of flow moving radially outward and direct to a single tangential exit point. To provide this efficiency, volutes are sized to provide near zero circumferential static pressure distribution at the Best Efficiency Point (BEP). However, as the compressor or pump operates away from BEP, a circumferential variation in static pressure is created within the diffuser and is felt by the impeller. This non-uniform static pressure can also be felt in the journal bearings. Accounting for this radial loading is essential when sizing journal bearings for the pump or compressor to work properly. The volute has been the subject of numerous extensive theoretical, numerical and experimental studies, because the volute strongly affects the overall performance, stability, operating range and the location of the best efficiency point of the pump or compressor. This paper reviews the status of methods for predicting the volute-induced radial force and also attempts to provoke renewed interest and possibly encourage more work to contribute towards a more accurate prediction of the volute-induced radial force. Both pumps and compressor are now being built with increasing pressure ratios, higher speeds and larger sizes, thus giving importance to the need for more accurate radial force prediction methods.
Perforated-Plate Turbulence: Orifice Versus Converging Nozzle
Authors: Yang Yang , Ting David S.-K. , Ray Steve
Published: October 2018

The classical grid turbulence is revisited in an effort to better understand the role of the finite-thickness flow passage of the turbulence generator. The virtually zero-thickness orificed perforated plate (OPP) is contrasted with its reversed counterpart, the converging-nozzled perforated plate (CNPP). The respective turbulent flows are detailed via a triple-wire of a constant-temperature hot wire anemometer. The two flows are compared in terms of the spatial evolution of the essential turbulence characteristics, including the various turbulence intensities and length scales. As expected, a higher level of turbulence resulted from the sharp edges of the OPP. Surprisingly, the finite-thickness converging passages of the CNPP caused the other turbulence parameters to behave rather perplexingly.
Vortex Identification Study of a Turbulent Cavity Flow
Authors: Hammad Khaled J.
Published: October 2018

A combined vortex identification and Proper Orthogonal Decomposition (POD) analysis is applied to high-resolution Particle Image Velocimetry (PIV) measurements of a turbulent flow past an open shallow cavity. The PIV measurements, at a cavity depth based Reynolds number of 42,000, capture the flow structure and turbulence, upstream, over, and downstream an open cavity having a length-to-depth ratio of four. Vorticity and second invariant Q of the velocity gradient tensor analysis are used to identify the vortical structures and the overall flow field features. POD analysis is applied to the vorticity and Q fields to identify the most energetic vortical structures and flow features. The results demonstrate the superiority of the combined Q-criterion and POD analysis in identifying distinct vortical structures and their evolution.
RANS Modelling of a Swirling Flow Interacting With a Conical Bluff Body
Authors: Song J. , Kharoua N. , Khezzar L. , Alshehhi M.
Published: October 2018

Phase separation using swirling flows is a technique used in inline separators. In the present study, an existing separator device generates a swirling flow which interacts with a conical hollow bluff body to where the air phase is collect. We use the commercial CFD code Fluent to simulate and investigate the characteristics of single-phase turbulent swirling flow interaction with a solid conical bluff body on a laboratory-scale model. The simulation work employed different RANS turbulence models; namely, RNG k-ε, SST k-ω and RSM. A constant velocity was imposed at the inlet of the computational domain while a constant pressure was prescribed at the outlet. The results are validated against experimental measurements. The effect of flow rate was investigated. The resulting flow is investigated around the bluff body and within the whole outlet pipe downstream of the swirl generator because the separation depends strongly on the flow behavior in this extended region. The core flow reversal persists up to the bluff body at high flow rates. This is significant in terms of phase behavior in the separation application in addition to the loads on the bluff body. The profiles of the tangential velocity corresponded to a Rankine vortex swirling flow type along the whole axial distance. The results show that the RSM gives the best accuracy among the three RANS models compared with the experimental data. The rate of swirl decay decreases as the flow rate increases. For the lowest flow rate, the swirl decay followed an exponential trend which becomes almost linear for the highest flow rate considered. At low swirl intensities, the pressure peaks are observed on the bluff body apex while, at high swirl intensities, the reversal flow generates the lowest pressure at the centerline affecting the cone as well.
Analysis on Energy-Saving Reconstruction of Jinshan Water Pumping Station in Zhenjiang
Authors: Luo Yin , Gong Bo , Yuan Shouqi , Sun Hui , Xiong Zhixiang
Published: October 2018

For the reason that current pump performance parameters and its piping system do not match, a new plan was proposed in this study to improve the low efficiency and reduce the high-energy consumption of Zhenjiang water intake pump station. According to the measured data in the field and the design information of the pumping station system, the simulation model of the pumping station is established with the help of commercial software Flowmaster. Based on this model, the simulation of various operating conditions is carried out. Considering the running condition of the pump station in the past years, the design condition spectrum of the new pump station is finally formed. On the purposes of optimizing the scheduling and decreasing the reconstruction cost, the implementation plan of pump station reconstruction was determined. Under the guidance of the plan, the work of design, manufacturing, testing, installation and debugging of a new type of double suction pump are completed in combination with the actual situation. The results show that the cost of electricity can be saved by 35,000 dollars and the cost of reconstruction can be recovered in less than one year. This study realizes energy-saving in the pumping station operation.
Fluid-Structure Interaction Simulations of Flexible Cylinders in Confined Axial Flow
Authors: Degroote Joris , Delcour Lucas , De Moerloose Laurent , Dolfen Henri , Vierendeels Jan
Published: October 2018

Flexible cylinders surrounded by a fluid flow that is dominantly aligned with the axis of the cylinders can be found in several applications. Examples with a flow confined to a narrow region around the cylinder(s) can be found in tube bundles of heat exchangers and reactor cores and also in air-jet weaving machines. This research analyses the flow-induced vibration of these two different cases with flexible cylinders in confined axial flow using numerical fluid-structure interaction (FSI) simulations.

The FSI simulations of both cases use a partitioned framework, meaning that a computational fluid dynamics (CFD) solver is coupled with a finite element analysis (FEA) structural solver. The dynamic and kinematic equilibrium conditions at the contact surface between the fluid and the structure are satisfied by performing coupling iterations between both solvers in each time step. Convergence of these iterations is accelerated using quasi-Newton coupling techniques.

For the case of the tube bundle, the modal characteristics have been identified for a tube bundle when they are submerged in an axial fluid flow. Furthermore, different types of flow-induced vibration have been studied. The flow speed has been increased in an FSI simulation of a single cylinder surrounded by an annular fluid domain, resulting first in static buckling and then in flutter at higher flow speeds.

For the case of the air-jet weaving machines, the cylinder represents a smooth yarn which is accelerated by an air jet in the main nozzle of the machine, consisting of a long tube with small diameter. FSI simulations of a yarn clamped at the upstream end have been performed using the arbitrary Lagrangian-Eulerian formulation with deforming grids in the fluid domain.

This work demonstrates the feasibility of analyzing and predicting flow-induced vibration of cylinders in confined axial flow by performing FSI simulations. The results of simulations are compared with those of experiments for tubes in axial flow and for a yarn in a nozzle of an air-jet weaving machine.
Influence of Numerical Dissipation on Draft Tube Flows
Authors: Jiang Yao , Yang Liu , Nadarajah Siva
Published: October 2018

Hydro-turbines are operated at loads above or below the best efficiency point (over- or part-load), where turbulent flow structures are formed in the draft tube. The goal of the project is to investigate turbulent flows present in the draft tube through a thorough numerical investigation. In the context of numerical simulations, a focus is made on the numerical scheme. Steady and unsteady simulations with the k-ωom SST turbulence model are applied with a novel eddy-preserving limiter scheme for draft tube flows. The application of the eddy-preserving limiter scheme allows to better resolve the flow field. Numerical results are validated through a comparison to experimental data.
Computational Analysis on Aerodynamics and Vortex Formation of Sleep Apnea
Authors: Wang Junshi , Han Pan , Sanchez Yaselly , Xi Jinxiang , Dong Haibo
Published: October 2018

The fluid dynamics of air flow in the pharynx is critical to the vibration of the uvula and to the generation of the snoring sound. In this work, a combined experimental and computational approach was conducted to study the aerodynamics of the flow field in the human airway. An anatomically accurate pharynx model associated with different uvula kinematics was reconstructed from human magnetic resonance images (MRI) and high-speed photography. An immersed-boundary-method (IBM)-based direct numerical simulation (DNS) flow solver was used to simulate the corresponding unsteady flows in all their complexity. Analysis has been performed on vortex dynamics and pressure oscillation at various points of interest. Computations with varying airway obstructions, uvula kinematics, and vibrating frequencies were conducted to study the effect of the three factors on the vortex formation and pressure oscillation, respectively. It is found that the vortex formation is significantly affected by the airway width. The fast Fourier transformation (FFT) analysis of the pressure time history revealed the existence of higher order harmonics of the base frequency at significant amplitudes. It was also found that the pressure tended to oscillate more violently at higher uvula vibrating frequencies. Results from this work are expected to bring novel understanding on the sound producing in patients with sleep apnea and provide guidance for surgical interventions.
Kinematics and Hydrodynamics of Invertebrate Undulatory Swimming
Authors: Tian Jianghong , Han Pan , Deng Xiaolong , Lindengren Royce E. , Liu Geng , Ren Yan , Dong Haibo
Published: October 2018

Dorsoventral undulation is adopted by aquatic mammals for propulsion. However, it is not too common to find invertebrate aquatic animals that undulate their bodies in the vertical plane, which results from antiphasic contractions of dorsal and ventral muscles. To explore the mechanisms of the soft-bodied propulsion, in this work, an annelid swimmer employing up and down undulatory swimming mode is chosen, and the related kinematics and hydrodynamics are studied using a combined experimental and computational approach.

A fully calibrated photogrammetry system with three highspeed cameras from different views is used to record the forward swimming motion of this invertebrate swimmer, namely leech. The vertically undulating kinematics are then reconstructed from those videos. With the detailed reconstruction, the undulating wavelength and amplitude distribution the swimmer exhibits during propulsion are quantified. Kinematics analysis results show that the invertebrate swimmer swims in a vertical anguilliform mode and the wavelength is about 0.7BL (body length) when it swims at a velocity of 1.5BL/s. An in-house immersed-boundary-method based flow solver is used to conduct the numerical simulations, with which the hydrodynamic performance and wake structures are investigated. The thrust generation and power consumption of the undulating body are described quantitatively. Furthermore, along the undulating body, the pressure distributions are studied.
Experimental Investigation of Liquid Cooling Through Shallow Copperclad Cavities With Etched Pin-Fin Arrays
Authors: Lam Yin , Okamoto Nicole , Shabany Younes , Lee Sang-Joon John
Published: October 2018

Heat removal is an increasing engineering challenge for higher-density packaging of circuit components. Microchannel heat sinks with liquid cooling have been investigated to take advantage of high surface-to-volume ratio and higher heat capacity of liquids relative to gases. This study experimentally investigated heat removal by liquid cooling through shallow copperclad cavities with staggered pin-fin arrays. Cavities with pin-fins were fabricated by chemical etching of a copperclad layer (nominally 105 μm thick) on a printed-circuit substrate (FR-4). The overall etched cavity was 30 mm wide, 40 mm long, and 0.1 mm deep. The pins were 1.1 mm in diameter and were distributed in a staggered arrangement. The cavity was sealed with a second copperclad substrate using an elastomer gasket. This assembly was then connected to a syringe pump delivery system. Deionized water was used as the working fluid, with volumetric flow rate up to 1.5 mL/min. The heat sink was subjected to a uniform heat flux of 5 W on the underside. Performance of the heat sink was evaluated in terms of pressure drop and the convection thermal resistance. Pressure drop across the heat sinks was less than 10 kPa, dominated by wall surface area rather than the small surface area contributed by cylindrical pins. At low flow rate, caloric thermal resistance dominated the overall thermal resistance of the heat sink. When compared to a microchannel without pins, the pin-fin microchannel reduced convective thermal resistance of the heat sink by approximately a factor of 4.
Nozzle Orientation Effects on the Turbulent Structure of Submerged Twin Jets
Authors: Nwaiwu Chidiebere F. , Agelin-Chaab Martin , Tachie Mark F.
Published: October 2018

Nozzle orientation effects on the turbulent structure of submerged twin jets were investigated experimentally. The twin jets were offset from the free surface by the ratio, h/d = 2, where h is the offset height displacement and d is the nozzle’s hydraulic diameter. The experiments were conducted using a pair of rectangular nozzles having an aspect ratio of 3, oriented in both the minor and major axes. The Reynolds number based on the jet exit velocity and nozzle hydraulic diameter was maintained at 4622. The results show a 74% increase in the attachment length for the nozzle oriented in the major axis relative to the minor. The streamwise velocity at the free surface accelerated at a 58% higher rate for the minor axis orientation compared to that of the major axis. The joint probability density function show a dominance of the fast streamwise fluctuation in the generation of the Reynolds shear stress.
Numerical Simulation of Formation of Melt Jets in Melt-Coolant Interactions
Authors: Contreras-Serna Jorge , Schiaffino Arturo , Kotteda V. M. Krushnarao , García-Cuéllar Alejandro J. , Kumar Vinod
Published: October 2018

Fragmentation of molten metal droplets is an important process in steam explosions caused by melt-coolant interactions. Ciccarelli and Frost (1994) found the formation of melt jets (or spikes) in hot melt drops immersed in water. In order to gain insight into this mechanism, they carried out experiments where melt jets were formed in a stratified water/liquid metal system with local generation of high-pressure vapor at the interface. This paper is dedicated to investigating how melt jets are formed in this mechanism when a stratified water/liquid metal system is analyzed. Also, a study of the most significant parameters in this process is performed. A 2D computational fluid dynamics (CFD) simulation is carried out using ANSYS Fluent software to study these phenomena by having water above hot liquid metal, a vapor film in between and a pressure pulse in the vapor film. The results show that the larger the pressure or density, the greater the melt jet length. In order to confirm this, deep neural network algorithm created by TensorFlow library was implemented to facilitate the understanding of the studied phenomena. The formation of melt jets observed in Ciccarelli and Frost’s experiments is also observed in current simulation.
Evaluation of Models for Droplet Shear Effect of Centrifugal Pump
Authors: Dabirian Ramin , Cui Shihao , Gavrielatos Ilias , Mohan Ram , Shoham Ovadia
Published: October 2018

During the process of petroleum production and transportation, equipment such as pumps and chokes will cause shear effects which break the dispersed droplets into smaller size. The smaller droplets will influence the separator process significantly and the droplet size distribution has become a critical criterion for separator design. In order to have a better understanding of the separation efficiency, estimation of the dispersed-phase droplet size distribution is very important. The objective of this paper is to qualitatively and quantitatively investigate the effect of shear imparted on oil-water flow by centrifugal pump.

This paper presents available published models for the calculation of droplet size distribution caused by different production equipment. Also detailed experimental data for droplet size distribution downstream of a centrifugal pump are presented. Rosin-Rammler and Log-Normal Distributions utilizing dmax Pereyra (2011) model as well as dmin Kouba (2003) model are used in order to evaluate the best fit distribution function to simulate the cumulative droplet size distribution. The results confirm that applying dmax Pereyra (2011) model leads to Rosin-Rammler distribution is much closer to the experimental data for low shear conditions, while the Log-Normal distribution shows better performance for higher shear rates. Furthermore, the predictions of Modified Kouba (2003) dmin model show good results for predicting the droplet distribution in centrifugal pump, and even better predictions under various ranges of experiments are achieved with manipulating cumulative percentage at minimum droplet diameter F(Dmin).
Numerical Investigation of the Efficiency of the Treatment Shaft for Separation of Suspended Solids in Wastewater Treatment
Authors: Mamouri Sina Jahangiri , Ghalib Saad A. , Bénard André
Published: October 2018

A combined sewer system is a facility that collects both municipal sewage and surface runoffs. These facilities may overflow (combined sewer overflow or CSO) during large storms which results in serious pollution, i.e. the flows exceed the capacity of the treatment plant. An approach to reduce the number of combined sewer overflows is to store rainfall runoffs temporarily [1]. The Treatment Shaft system is a relatively new but proven patented technology (U.S. Patent [2] and other patents) that includes the necessary CSO control and treatment, with less footprints than existing systems, and at a reduced cost. In this system, wastewater is collected in a large shaft equipped with baffles and partitions designed to ensure a very slow velocity within the system. In this study, the efficiency of the Treatment Shaft system for separation of solid contents without the use of flocculation agents is investigated. Moreover, the effect of geometry modifications on the separation efficiency is evaluated. For this purpose, a Computational Fluid Dynamics (CFD) approach for multiphase flow of particulate wastewater is used to evaluate the performance of various Treatment Shaft designs for a 10-year, 1-hour rainstorm event. It is shown that the Treatment Shaft is an effective technology to separate particles larger than 175μm, and more than 50% of the particles of size 175μm or more are settled. Additionally, several design variations are assessed and a design with a less footprint is specified.
On Non-Spherical Nanoparticle Dynamics in Turbulent Flows
Authors: Tian L. , Ahmadi G.
Published: October 2018

Dispersion and deposition of non-spherical nano- and micro-particles suspended in turbulent flows was studied. Due to the non-spherical morphology, the coupled equations of translational and rotational motions of particles were solved and the corresponding particle trajectories were evaluated. For nano-particles with the scale comparable to the gas mean free path, the Brownian diffusion effects that becomes important was included in both translational and rotational motions. Particular attention was given to the interactions of nano-ellipsoidal particles and fluid motions at different scales. Examples of nano-ellipsoidal particle dispersion and deposition in ducts and respiratory tracks were presented and discussed. Such information is useful for understanding the transport processes of asbestos and nano-fibers in human airways for inhalation risk assessment studies.
Effect of Non-Newtonian Blood Flow on Coronary Artery Hemodynamics in a Cohort of Patients With Stenosed Artery
Authors: Abbasian Majid , Shams Mehrzad , Valizadeh Ziba , Moshfegh Abouzar , Javadzadegan Ashkan
Published: October 2018

Wall shear stress (WSS) distribution in stenosed arteries has been known as an important hemodynamic factor to correlate with atherosclerosis and associated disturbances in blood flow. WSS depends on various factors such as geometric complexity and tortuosity of the artery, stenosis severity and morphology as well as blood rheological properties. We conducted a numerical simulation of blood flow using Ansys CFX software in 9 patient-specific coronary artery models with 3 classes of stenosis severity: mild, moderate and severe. For this purpose, we compared some numerical results between two non-Newtonian models and Newtonian blood flow viscosity using 9 patient-specific coronary artery models including the full range of real (physiological) stenosis, reconstructed from 3DQCA (quantities coronary angiography). Incompressible and steady state form of Navier-Stokes equations were used as governing equations. Flow was considered laminar and artery walls were assumed to be rigid. Results showed that the magnitude of WSS usually increases by decreasing the cross-section area of arteries. Despite the difference in the WSS magnitude between different models in each artery, the trend of variation of WSS along the artery was the same in all three models. The local peak point of WSS along the artery occurs at the stenosis location, same for all models.
An Integrated Approach for the Teaching of Pipe Network Analysis Using Project Based Learning
Authors: Ibrahim I. , B. Khalid M. W. , Shoukat G. , Sajid M.
Published: October 2018

This paper discusses the results of a study regarding the impact of using Project-Based Learning (PBL) to enhance the understanding of the concepts related to Pipe Network Analysis, a subtopic of Fluid Mechanics, studied by students enrolled in a mechanical engineering degree. It has been frequently reported by students and professors alike, that a lecture-only approach is not effective in terms of helping students grasp the fundamentals of a subject, nor does it help students in actual problem solving where different variables have to be catered to, which may have been ignored in a conventional lecture. Therefore, in this study, a more open-ended, complex project-based approach was used in addition to the lectures on the subject of Pipe Network Analysis. The project required students to design a pipe network for a scaled setup based on specified fluid flow and pressure head requirements at different nodes. An experimental setup that implemented these pipe networks was also developed in order to validate the theoretical results. The students’ grades and their documented responses were used as the criterion for compiling and analyzing the results. We also describe how we incorporated PBL into the classrooms in order to improve the learning experience, and evaluate the efficacy of the proposed method. The overall results show that the students were proactively engaged in the PBL activity, linking their knowledge to the real world, which ultimately led to improved concept development.
Nucleate Boiling Heat Transfer and Bubble Dynamics of Water-in-Polyalphaolefin Nanoemulsion
Authors: Xu Jiajun , McLaurin James , Beckett Cyree
Published: October 2018

In this study, an experimental study of the nucleation heat transfer and bubble dynamics inside the Water-in-PAO nanoemulsion fluid has been performed. Synchronized highspeed video and infrared thermography are used here to capture time-resolved temperature distribution data for the boiling surface and direct visualization of the bubble cycle. Data gathered included measurements of bubble growth versus time, as well as temperature history of the heater surface underneath the bubbles. Our findings demonstrate a substantial increase in nucleate heat transfer (i.e., heat transfer coefficient), and significantly different bubble dynamics of nanoemulsion fluid compared to pure water. The bubble growth rate of the nanoemulsion lies in the diffusion-controlled regime, and the growth data fit a power law at n ≈ 0.3. This is similar to the authors’ previous study of a similar fluid and is very different from conventional fluids. While the heat transfer mechanisms behind are not completely understood yet, it is hypothesized that the interfacial structures and thermal transport between surfactant molecules surrounding water nanodroplets and the base PAO fluid at elevated temperature may contribute to that.
Wetness Effect on Transonic Moist-Air Flow Through a Compressor Rotor
Authors: Moriguchi Shota , Miyazawa Hironori , Furusawa Takashi , Yamamoto Satoru
Published: October 2018

In this study, we simulated moist-air flows through a 3-D transonic compressor rotor, NASA Rotor 37, to investigate the thermophysical effects of evaporation of water droplets on 3-D compressor aerodynamics. The obtained results indicated that the total pressure ratio increased in the moist-air cases when compared with dry-air case as a result of the cooling due to evaporation. While the choking mass-flow rate is almost identical for the dry-air case and the moist-air cases, the operating curve was shifted to nearly choked state in the moist-air cases. Besides this, unsteady flows were obtained at higher mass-flow rate in the moist-air cases when compared with the dry-air case. As a result, a significant deterioration in the operation was observed in the moist-air cases. This is due to the rapid and significant evaporation of water droplets after the passage shock. A secondary flow streaming radially outside toward the tip through the separated region intensified and contributed to a formation of large blockage around the tip region.
Numerical Study on Transient Dynamics in a Centrifugal Pump Considering Clearance Flow
Authors: Jiang Chen-Xing , Wang Xi , Kang Na-Xin , Zhang Xiang-Yuan , Shuai Zhi-Jun , Li Wan-You
Published: October 2018

This paper investigates the transient flow characteristics and the forces on the impeller in a single-stage centrifugal pump considering the clearance flow. The finite volume method is employed to simulate the dynamics process. First, Numerical simulation is carried out in a commercial code CFX. The external performance characteristics, internal flow structure and pressure fluctuation in the two different models, with clearance and without clearance, are compared. It is found that the existence of the clearance flow can generate more vortex and hydraulic loss, which makes the flow state more complicated. Besides, the transient radial and axial forces on the impeller are analyzed. And an optimized model with modified chamber flow field is proposed, which can provide a theoretical foundation on the structure design of the centrifugal pump.
Probabilistic Analysis of Creep-Induced SGTR for NPP
Authors: Li Wenjing , Zhu Wentao , Yu Xinli , Wei Wei
Published: October 2018

Severe accident analysis is the technical basis of severe accident prevention and mitigation, and severe accident phenomenon analysis can provide important technical support for Level-2 Probabilistic Safety Analysis (L2 PSA) and severe accident management of NPP. This paper evaluates the probability of creep-induced steam generator tubes rupture (SGTR) which might lead to direct release of radioactive material to environment based on Risk-Oriented Accident Analysis Methodology (ROAAM). According to Larson-Miller creep failure model, the material parameters are provided first, then a two-loop NPP model is established with MAAP4 code to assess the temperature and pressure of the pipes for typical sequences, and eventually the probability of creep-induced SGTR phenomenon for typical sequences is calculated.
The Deep-Coupling and Preprocessed Photon Transport Based on RMC Codes
Authors: Qingquan Pan , Kan Wang
Published: October 2018

The conventional method for neutron-photon coupling transport calculation lacks of clear physical meanings, where the process of neutron transport and photon transport are independent, and only ensures the numbers of photons to be coupling with the neutrons. At the same time, when dealing with photoelectric effect, the nuclear data will be processed frequently, increasing the amount of calculation. By modifying the RMC codes, the deep-coupling and preprocessed photon transport is achieved. This new coupling method can satisfy the physical requirements and reduce the computational complexity while ensuring the accuracy of the calculation. At the same time, the preprocessing of the photoelectric effect nuclear data can accelerate the calculation without changing the calculation results. Through the deep-coupling and preprocessed photon transport method, the RMC codes can finished the high-precision shielding calculation. A typical LWR component is calculated with the new method, and the results prove the effectiveness.