bluuebunny/crossref_metadata_2025 huggingface dataset:
Bacterial contamination and prevalence of antimicrobial resistance phenotypes in raw fruits and vegetables sold in Delhi, India
Authors: Saksena Rushika , Malik Manika , Gaind Rajni
Published: November 2019

Fresh fruits and vegetables contaminated with microbial pathogens can cause outbreaks of food poisoning and other enteric diseases if consumed raw. The objective of the present study was to determine the bacterial contamination and antibiotic resistance in fresh produce sold in Delhi, India. One hundred fifty samples of fruits and vegetables generally consumed raw were collected from retail and wholesale vendors of Delhi‐NCR, India. Microbial contamination was studied by culturing 25 g of each sample. Antimicrobial resistance testing was performed for isolated pathogens and resistance phenotypes determined. Overall, 97.3% of fruit and vegetables sampled were contaminated with pathogens. In over 75% of samples, coliforms were detected with Escherichia coli in 17.4%. Majority of vegetables were contaminated with coliforms particularly ginger (100%), cabbage (80%), cucumber (75%), and tomato (75%). Extended spectrum beta‐lactamases (ESBL) was detected in eight (5.7%) isolates, carbapenem resistance in four with three metallo‐β‐lactamases producers. E. coli was isolated at a significantly higher rate from retail shops viz‐a‐viz wholesale markets (p value = .04). As high level of contamination with potential human pathogens is present in fruits and vegetables sold in wholesale markets and retail shops in Delhi‐NCR, the study underlines the need for stricter regulations and implementation of standards.

Practical applications

The present study highlights the high level of contamination with potential human pathogens including coliforms present in fruits and vegetables sold in wholesale markets, self‐service retail shops and road side push carts in Delhi‐NCR, India. Presence of extended spectrum beta‐lactamases and metallo beta‐lactamases producing organisms in fruits and vegetables is a concerning food safety issue. Therefore, the study underlines the need for periodic monitoring of produce at various levels of production and sale are required to achieve satisfactory levels of microbial load.
An explicit test of Pleistocene survival in peripheral versus nunatak refugia in two high mountain plant species
Authors: Pan Da , Hülber Karl , Willner Wolfgang , Schneeweiss Gerald M.
Published: November 2019

Pleistocene climate fluctuations had profound influence on the biogeographical history of many biota. As large areas in high mountain ranges were covered by glaciers, biota were forced either to peripheral refugia (and possibly beyond to lowland refugia) or to interior refugia (nunataks). However, nunatak survival remains controversial as it relies solely on correlative genetic evidence. Here, we test hypotheses of glacial survival using two high alpine plant species (the insect‐pollinated Pedicularis asplenifolia and wind‐pollinated Carex fuliginosa) in the European Alps. Employing the iDDC (integrative Distributional, Demographic and Coalescent) approach, which couples species distribution modelling, spatial and temporal demographic simulation and Approximate Bayesian Computation, we explicitly test three hypotheses of glacial survival: (a) peripheral survival only, (b) nunatak survival only and (c) peripheral plus nunatak survival. In P. asplenifolia the peripheral plus nunatak survival hypothesis was supported by Bayes factors (BF> 100), whereas in C. fuliginosa the peripheral survival only hypothesis, although best supported, could not be unambiguously distinguished from the peripheral plus nunatak survival hypothesis (BF = 5.58). These results are consistent with current habitat preferences (P. asplenifolia extends to higher elevations) and the potential for genetic swamping (i.e., replacement of local genotypes via hybridization with immigrating genotypes [expected to be higher in the wind‐pollinated C. fuliginosa]). Although the persistence of plants on nunataks during glacial periods has been debated and studied over decades, this is one of the first studies to explicitly test the hypothesis instead of solely using correlative evidence.
Comprehensive Comparison of Liposomal Bupivacaine with Femoral Nerve Block for Pain Control Following Total Knee Arthroplasty: An Updated Systematic Review and Meta‐Analysis
Authors: Liu Yuan , Zeng Jun‐feng , Zeng Yi , Wu Yuan‐gang , Bao Xian‐chao , Shen Bin
Published: November 2019

To compare the efficacy of liposomal bupivacaine (LB) and femoral nerve block following total knee arthroplasty, we conducted this systematic review and meta‐analysis. 11 trials with 2,908 patients were included in this study. The pooled data demonstrated that total morphine consumption equivalents during the hospital stay was significantly increased in FNB group. In addition, LB has significantly better outcome in view of the postoperative functional recovery, such as the odds of fall, the incidences of straight leg rise (SLR), the number of patients who can walk independently in the day of surgery,the ambulation distance at POD1, the number of patients discharged at POD1. Consistent with the faster functional recovery, liposomal bupivacaine shortens the length of hospital stay. However, there was no significant difference between LB and FNB in terms of Visual Analogue Score (VAS) during the hospital stay. All in all, liposomal bupivacaine has significantly better outcome in view of the postoperative functional recovery and the length of hospital stay compared with femoral nerve block following the total knee arthroplasty.
The Global and the Local: Tracing the Trajectory of the Largest Biometric Identity Program
Authors: Rawat Pragati , Morris John C.
Published: November 2019

How did the largest national biometric identity program chart a successful trajectory for itself? We employ the actor‐network theory in a novel case of unprecedented scale to trace the trajectory of a complex government program in India. The program created a huge local network of human actors and technical artifacts and their resultant actions shaped the interests of the global network positively, thus managing the political support and flow of funds for the project. Modern strategies of minimalist design, open application program interfaces, and the fast pace of implementation strengthened the position of the program as the obligatory passage point.

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Sourcing and Procurement Cost Allocation in Multi‐Division Firms
Authors: Fang Fang , Natarajan Harihara Prasad
Published: November 2019

Through Central Procurement Organizations (CPOs), large firms with multiple divisions have begun adopting a center‐led sourcing approach that allows firms to centralize strategic sourcing activities, while permitting decentralized execution by divisions, allowing the firm to leverage large purchase volumes with vendors. This new center‐led procurement environment has brought a new decision requirement: How should a CPO select vendors for each division's requirements to minimize the firm's total procurement cost and simultaneously develop a fair and alignment‐inducing mechanism to allocate the costs (and savings) of company‐wide procurement to the divisions? Past research and current practice have not addressed this linkage between vendor selection and cost allocation in multi‐division firms. This work models this sourcing and procurement cost allocation (SPC) problem facing CPOs of large firms as a mixed‐integer optimization problem. This model is flexible and can incorporate several commonly‐used cost allocation rules. We show that the SPC problem is NP‐hard. Therefore, to support practical decision‐making in this context, we develop a tailored solution approach for the SPC problem. Our approach enhances the base model by adding strong valid inequalities. We tested our model and its enhancements in an extensive numerical study, solving over 160 instances. Results reveal that (a) the CPO can ensure fair cost allocation at a modest cost (relative to the centralized solution) with our model, and (b) the proposed tailored approach is effective and necessary in solving a wide variety of instances.
Using Hidden Information and Performance Level Boundaries to Study Student–Teacher Assignments: Implications for Estimating Teacher Causal Effects
Authors: Lockwood J. R. , McCaffrey D.
Published: November 2019

A common problem in educational evaluation is estimating causal effects of interventions from non-experimental data on students. Scores from standardized achievement tests often are used to adjust for differences in background characteristics of students in different non-experimental groups. An open question is whether, and how, these adjustments should account for the errors in test scores as measures of latent achievement. The answer depends on what information was used to assign students to non-experimental groups. Using a case-study of estimating teacher effects on student achievement, we develop two novel empirical tests about what information is used to assign students to teachers. We demonstrate that assignments are influenced by both information that is unobserved by the researcher, and error prone test scores. We develop a model that is appropriate for this complex selection mechanism and compare its results with common simpler estimators. We discuss implications for the broader problem of causal modelling with error prone confounders.
Perceptions of Past Parenting and Adult Attachment as Vulnerability Factors for Suicidal Ideation in the Context of the Integrated Motivational–Volitional Model of Suicidal Behavior
Authors: Zortea Tiago C. , Gray Cindy M. , O’Connor Rory C.
Published: November 2019

Objective

We aimed to investigate whether perceptions of past parenting and current attachment orientations are associated with key components of the Integrated Motivational–Volitional (IMV) Model of Suicidal Behavior. We investigated the relationship between perceptions of past parenting, attachment, suicide ideation, defeat, entrapment, coping, and resilience.

Method

A total of 730 adult participants responded to an online questionnaire comprised of psychological measures. An initial regression analysis indicated that memories of past parenting and attachment were associated with suicide ideation. Four mediation models were tested based on the IMV model, all controlling for depressive symptoms.

Results

In the first model, attachment orientations mediated the relationships between perceptions of past parenting dimensions and defeat. In the second, defeat mediated the relationships between attachment orientations and entrapment. In the third, entrapment mediated the relationship between defeat and suicidal ideation, but coping did not moderate the defeat–entrapment relationship. In the final model, entrapment mediated the relationship between defeat and suicide ideation, with resilience moderating this relationship.

Conclusions

The findings are novel and congruent with the core principles of the IMV model. Clinical implications suggest the protective effect of resilience and strengthening of self‐compassion attitudes to reduce the effect of insecure attachment strategies.
Moving beyond categorization to understand affective influences on real world health decisions
Authors: Ferrer Rebecca A. , Ellis Erin M.
Published: November 2019

This paper provides an overview of affect and health decision‐making research, with a focus on identifying gaps, opportunities, and challenges to guide future research. We begin by defining common categorical distinctions of affective processes that influence health decisions: integral (i.e., related to the decision) and incidental (i.e., normatively unrelated to the decision) influences, and current (experienced in the moment) and anticipated (“cognitive representations” of future affect) affect. We then summarize key discoveries within the most common categories of affective influences on health decision making: current integral affect, current incidental affect, and anticipated integral affect. Finally, we highlight research gaps, challenges, and opportunities for future directions for research aimed at translating affective and decision science theory to improve our understanding of, and ability to intervene upon, health decision making.
Digitaria sanguinalis seed dormancy release and seedling emergence are affected by crop canopy and stubble
Authors: Oreja F H , Batlla D , de la Fuente E B
Published: November 2019

Digitaria sanguinalis is a troublesome annual weed that causes important yield losses in different crops. Despite this, there is scarce information about different aspects of its biology under field conditions. New knowledge about the establishment process of this species will be of paramount importance in order to maximise the effectiveness of weed management. The aims of this paper were to evaluate the effect of stubble found on the surface on seed dormancy levels through the season, the effects of stubble and soyabean crop canopy on seedling emergence and to determine the field emergence pattern as a consequence of seed dormancy level at dispersal time. Seeds on the soil surface, which showed a high dormancy level at the beginning of autumn, were released from dormancy by low winter temperatures and germinated during spring as temperatures rose, showing a transient surface seedbank. Seeds covered by stubbles had delayed the emergence in the field due to lower alternating temperatures perceived by the surface seedbank. On the other hand, the presence of a soyabean crop and stubble together reduced the number of seedlings. Seeds with a high dormancy level at dispersal time showed a delayed emergence in the next season when compared with seeds with a lower dormancy level. However, the final number of seedlings was similar. Both stubble on surface and crop canopy are useful factors to lessen and delay the seedling emergence allowing the design of weed management strategies in order to diminish the population levels of this species.
Ensuring the Future of Nuclear Power
Authors: Duffey Romney , Pioro Igor
Published: November 2019

In the early 2000s, the talk was of a so-called Nuclear Renaissance with hundreds of new nuclear plants to be ordered. We should be seeing the fruits of that now, but we are not. There have been several factors that have led to the stagnation of nuclear power industry. To revive the sector, it is important to evaluate the current status of the nuclear power industry, examine the requirements that all new power technologies in open and competitive markets must meet, and determine whether present and future nuclear-power technologies look to be capable of achieving those goals.
A Method to Determine Material Length Scale Parameters in Elastic Strain Gradient Theory
Authors: Song Jingru , Wei Yueguang
Published: November 2019

With specimen size decrease for advanced structural materials, the measured mechanics behaviors display the strong size effects. In order to characterize the size effects, several higher-order theories have been presented in the past several decades, such as the strain gradient theories and the micro-polar theories, etc. However, in each higher-order theory, there are several length scale parameters included, which are usually taken as the material parameters and are determined by using the corresponding theoretical predictions to fit experimental results. Since such kind of experimental approaches needs high techniques, it is very difficult to be performed; therefore, the obtained experimental results are very few until now; in addition, the physical meanings of the parameters still need to be investigated. In the present research, an equivalent linkage method is used to simply determine the elastic length parameters appeared in the elastic strain gradient theory for a series of typical metal materials. We use both the elastic strain gradient theory and the higher-order Cauchy-Born rule to model the materials mechanics behaviors by means of a spherical expanding model and then make a linkage for both kinds of results according to the equivalence of strain energy densities. The values of the materials length parameters are obtained for a series of typical metal systems, such as the face-centered cubic (FCC), body-centered cubic (BCC), and hexagonal close-packed (HCP) metals.
A Simulation Data-Driven Design Approach for Rapid Product Optimization
Authors: Shao Yanli , Zhu Huawei , Wang Rui , Liu Ying , Liu Yusheng
Published: November 2019

Traditional design optimization is an iterative process of design, simulation, and redesign, which requires extensive calculations and analysis. The designer needs to adjust and evaluate the design parameters manually and continually based on the simulation results until a satisfactory design is obtained. However, the expensive computational costs and large resource consumption of complex products hinder the wide application of simulation in industry. It is not an easy task to search the optimal design solution intelligently and efficiently. Therefore, a simulation data-driven design approach which combines dynamic simulation data mining and design optimization is proposed to achieve this purpose in this study. The dynamic simulation data mining algorithm—on-line sequential extreme learning machine with adaptive weights (WadaptiveOS-ELM)—is adopted to train the dynamic prediction model to effectively evaluate the merits of new design solutions in the optimization process. Meanwhile, the prediction model is updated incrementally by combining new “good” data set to reduce the modeling cost and improve the prediction accuracy. Furthermore, the improved heuristic optimization algorithm—adaptive and weighted center particle swarm optimization (AWCPSO)—is introduced to guide the design change direction intelligently to improve the search efficiency. In this way, the optimal design solution can be searched automatically with less actual simulation iterations and higher optimization efficiency, and thus supporting the rapid product optimization effectively. The experimental results demonstrate the feasibility and effectiveness of the proposed approach.
CFD Analysis of Premixed Combustion in a Two Stroke Polygon Engine
Authors: Anderson Kevin R. , Mendez Christian
Published: November 2019

The numerical modeling of the premixed combustion occurring in the chamber of a polygon engine is presented in this paper. This research is being carried out to support the analysis and design of a lightweight, two-stroke, six-sided, in-plane, polygon engine. Results for average combustion chamber temperature, turbulent flame speed, progress variable, and Damkohler number versus piston position are presented for methane (CH4), diesel (C10H22), and ethanol (C2H50H) fuels, respectively.
Effect of Microscopic Vortices Caused by Flow Interaction With Solid Obstacles on Heat Transfer in Turbulent Porous Media Flows
Authors: Huang Ching-Wei , Srikanth Vishal , Li Haodong , Kuznetsov Andrey V.
Published: November 2019

Turbulent flow in a homogeneous porous medium was investigated through the use of numerical methods by employing the Reynolds Averaged Navier-Stokes (RANS) modeling technique. The focus of our research was to study how microscopic vortices in porous media flow influence the heat transfer from the solid obstacles comprising the porous medium to the fluid. A Representative Elementary Volume (REV) with 4 × 4 cylindrical obstacles and periodic boundary conditions was used to represent the infinite porous medium structure.

Our hypothesis is that the rate of heat transfer between the obstacle surface and the fluid (qavg) is strongly influenced by the size of the contact area between the vortices and the solid obstacles in the porous medium (Avc). This is because vortices are regions with low velocity that form an insulating layer on the surface of the obstacles. Factors such as the porosity (φ), Pore Scale Reynolds number (Rep), and obstacle shape of the porous medium were investigated. All three of these factors have different influences on the contact area Avc, and, by extension, the overall heat transfer rate qavg. Under the same Pore Scale Reynolds number (Rep), our results suggest that a higher overall heat transfer rate is exhibited for smaller contact areas between the vortices and the obstacle surface. Although the size of the contact area, Avc, is affected by Rep, the direct influence of Rep on the overall heat transfer rate qavg is much stronger, and exceeds the effect of Avc on qavg. The Pore Scale Reynolds number, Rep, and the mean Nusselt number, Num, have a seemingly logarithmic relationship.
Influence of Turbulence Models in Transient Simulations of Inducers Under Steady Operation
Authors: Gwiasda Björn , Mohr Matthias , Herrmann-Verspagen Dennis , Böhle Martin
Published: November 2019

A significant uncertainty in full transient 3D-CFD simulations of inducers is the used turbulence model. To investigate the influence of different turbulence models (Spalart-Allmaras, SST, SSG) on the transient effects experiments and simulations are performed for two inducers. In this paper the results of simulations are represented that are performed under noncavitating conditions to exclude the additional influence of the cavitation model in order to gain an isolated understanding for the influence of turbulence models. Comparison of transient data from simulations as well as experiments determines the influence of the turbulence model. For the investigations two different inducers are designed with different leading edges. One inducer with a straight leading edge and one with a back swept leading edge. All other geometrical parameters are kept constant, such as the hub contour which is purely axial.
CFD Simulations of the Rheological Behavior of Aqueous Foam Flow Through a Half-Sudden Expansion
Authors: Dallagi Heni , Al Saabi Ahmad , Faille Christine , Benezech Thierry , Augustin Wolfgang , Aloui Fethi
Published: November 2019

Aqueous foam is a non-Newtonian complex fluid. Its flow through the singularities presents many fundamental aspects. The rheological character of the foams flowing in this kind of geometries can create important disturbance on its behavior, according to the flow rate set and therefore a modification in its texture and in the nature of its established regime. During this study, numerical simulation for the case of a half-sudden expansion was developed using the Herschel-Bulkley rheological model. The model is used to describe the response of foams during under flowing conditions through this type of singularity. Obtained CFD results are focused on the pressure losses, velocity fields of the foam flow in various positions of the channel using different qualities (variation of void fraction) for lower velocities’ case (one-dimensional regime) and for the three-dimensional regime. Firstly, we validated the use of this type of non-Newtonian foam flow fluid to describe the flow reorganization through a half-sudden. In a second step, we used an experimental database to validate our CFD pressure losses and velocity fields. The comparison of these results with those obtained experimentally by Chovet shows a good agreement for lower speed foam flow, but with some uncertainty for higher foam flow velocities.
A Study of Multiphase Flow and Heat Transfer in Proton Exchange Membrane Fuel Cells With Perforated Metal Gas Diffusion Layers
Authors: Berning Torsten , Tanaka Shiro
Published: November 2019

A numerical analysis of a proton exchange membrane fuel cell (PEMFC) that contains a perforated metal plate at the cathode side has been conducted. The model utilizes the Eulerian multi-phase approach to predict the occurrence and transport of liquid water inside the cell. The PEMFC that was modelled contained micro-channels at both anode and cathode side. Results suggest that despite the fact that the inlet gases are fully saturated (RH = 100%), the holes in the metal sheet remain in the single phase, and the predicted maximum current densities are accordingly high. The high thermal conductivity of the metal sheets result in only a moderate temperature increase in the cell, and the fuel cell membrane is predicted to be hydrated under all conditions investigated. The fact that the cathode channel and the holes in the metal sheet remain dry is attributed to the high pressure drop inside the flow channel.
Global Sensitivity Analysis for Stay Vane and Casing Design of Reaction Hydraulic Turbine
Authors: Cho Hyunkyoo , Shrestha Ujjwal , Choi Young-Do , Park Jungwan
Published: November 2019

Global sensitivity analysis (GSA) estimates influence of design variables in the entire design domain on performance measures. Hence, using GSA, important design variables could be found for an engineering application with high dimension which require computationally expensive analyses. Then, similar engineering applications could use selected variables to carry out design process with smaller dimension and affordable computational cost. In this study, GSA has been carried out for the performance measures in design of stay vane and casing of reaction hydraulic turbines. Global sensitivity index method is used for GSA because it can fully capture the effect of interaction between the design variables. For efficiency, genetic aggregation surrogate models are constructed using the responses of computational fluid dynamic (CFD) analysis. Global sensitivity indices for the performance measures of stay vane and casing have been evaluated using the surrogate models. It is found that less than three design variables among 12 are effective in the design process of stay vane and casing in reaction hydraulic turbines.
Predicting Cooling Fan Noise of Electric Motor Using Compressible Large Eddy Simulation
Authors: Kaneko Kimihisa , Yamamoto Tsutomu
Published: November 2019

This paper describes prediction of aeroacoustics from a rotating machinery fan using compressible Large Eddy Simulation (LES). The fan is installed semi-opened space located between the fan cover and the body of rotating machinery such as a electric motor. The fan distributes air from the fan cover intake onto the cooling fins. The Reynolds number of the rotating fan is 9 × 105; its Mach number is approximately 0.1. Under the low Mach number regime, hybrid computational aeroacoustics (hybrid CAA) method, which is solved turbulent flow and acoustics separately, is generally used. However, we used a direct CAA method because interaction between pressure fluctuation from the turbulence and sound propagation should be considered.

For the direct CAA method approach, compressible Navier–Stokes equations are solved. Density is calculated from the ideal gas law. To compute turbulence phenomena, LES is used as the turbulence model. The Dynamic Smagorinsky Model is used for the subgrid scale. The sound propagation speed is approximately 10 times faster than the flow speed.

Therefore, the numerical schemes, time step, and computational grids size were evaluated with line sound source in the two-dimensional domain as a fundamental study to determine the numerical schemes. Subsequently we evaluated the sound pressure level with the electric motor fan, which is an experimental structure.

Through verification of the direct CAA model, we obtained the following results. (1) The predicted pressure fluctuation spectra show good agreement with the experimentally obtained spectra. Specifically, the blade passing frequency (BPF) and trend of the pressure fluctuation decay in the inertial turbulence subrange were predicted. (2) The predicted sound pressure spectra also show good agreement with BPF. Specifically, the acoustic mode and broadband turbulence noise level were predicted.
Numerical Calibration of 3D Printed Five-Hole Probes for the Transonic Flow Regime
Authors: Passmann Maximilian , aus der Wiesche Stefan , Joos Franz
Published: November 2019

This paper presents a method for a cost- and time-effective calibration procedure for five-hole probes for the transonic flow regime based on additive manufacturing and a numerical calibration routine. The computational setup and calibration routine are described in detail. The calibration procedure is tested on a custom-built L-shaped conical probe of 30° half-angle with a flat tip and an outer diameter of 2.4mm. The probe tip is manufactured in stainless steel using DMLS. Numerical calibration is carried out over a Mach number range of 0.2 to 1.4 and pitch and yaw angles of ±45°. The numerical calibration charts are validated with wind tunnel tests and the expected accuracy of the numerical calibration method is quantified. Exemplary results of area traverses up- and downstream of a linear transonic turbine cascade with tip clearance are presented and discussed briefly.
Investigation on the Effects of Torque Converter Blade Thickness Based on FSI Simulation
Authors: Liu Cheng , Guo Meng , Wei Wei , Yan Qingdong , Li Pengyu
Published: November 2019

A lot of efforts were put into the design of torque converter blade angles and the analysis of transient flow behaviors; yet little is known about the influence of the blade thickness distribution on the performance or structural response of a torque converter. This study proposed a parameterized blade thickness design model and analyzed the effects of the blade thickness on hydrodynamic performance and structural response using fluid-structure interaction (FSI) models. Both one-way FSI model and two-way FSI model were built and evaluated against test data, and it was found that the transient two-way FSI model outperformed the steady-state FSI model in terms of both flow and structure simulations. It was found that the stall torque ratio and peak efficiency exhibited positive correlations with blade thicknesses, whereas the stall capacity constant was inversely related to blade thicknesses. Both numerical and experimental results suggested that the pump-turbine interaction induced serious flow fluctuations, and FSI simulations were required in the design process to avoid potential resonance.
Transient Simulation on Unbalanced Torque of Piston Type Valve Cores During Dynamic Motion
Authors: Hou Cong-wei , Mu Juan , Li Wen-qing , Jin Zhi-jiang , Qian Jin-yuan
Published: November 2019

Piston type valve cores are widely adopted in check valves, globe valves, pressure reducing valves and so forth. With the irregular inlet flow channel, the bottom of piston type valve core exits unbalanced torques usually. The unbalanced torque causes the valve core to squeeze sealing elements and increases the energy consumption. To analyze the unbalanced torque on the bottom of the piston type valve core, a transient numerical model of the piston type valve core is established and the simulation results are compared with the theoretical formula for the purpose of validation. The dynamic flow characteristics are studied to investigate pressure characteristics on the bottom of the piston type valve core with the dynamic motion of the valve core. Meanwhile, pressure characteristics under different valve core displacements are obtained, and the sensitive range of the unbalanced torque is found. This work can be helpful for the further structural optimization on the valves with piston type valve cores.
CFD Investigation of a PEMFC Stack Assembly
Authors: Anderson Kevin R. , Murphy Andrew
Published: November 2019

In this study 3-D CFD modeling of a cylindrical stack Proton-exchange membrane fuel cell (PEMFC) is provided. The H2O-O2 PEMFC uses a 10.8 mm2 area membrane and Platinum (Pt) catalyst. The paper presents the methodology for the PEMFC commercial software module, the set-up of the Computational Fluid Dynamics (CFD) geometry, mesh and boundary conditions. Results for the current-voltage performance curves and 3-D contour plots of the fluid, heat and species concentrations within the PEMFC are given. Results are presented for a low-temperature fuel cell using NAFION membrane and a high-temperature fuel cell using BZY membrane.
Performance Improvement of Electro-Hydraulic Servo Valve Using a Feed-Forward Control and an Input Shaping Filter
Authors: Lee Illyeong , Iwan Istanto , Choi Saeryung , Huh Junyoung
Published: November 2019

The control performance of hydraulic systems is basically influenced by the performance of electro-hydraulic servo valve used in a hydraulic control system. In this study, the authors propose a control design to improve the control performance of servo valves with a non-contact eddy current type displacement sensor. Mathematical model for the valve is obtained through an experimental identification process. A PI-D controller together with a feedforward (FF) controller is applied to the valve. To further improve the response of the servo valve, an input shaping filter (ISF) is incorporated into the valve control system. Finally, the effectiveness of the proposed control system is verified experimentally.
CFD-Simulation of Centrifugal Fan Performance Characteristics Using Ideal and Real Gas Models for Air and Organic Fluids
Authors: Fritsche Manuel , Epple Philipp , Hasselmann Karsten , Reinker Felix , Wagner Robert , aus der Wiesche Stefan , Russwurm Hans
Published: November 2019

Efficient processes with organic fluids are becoming increasingly important. The high tech fluid Novec™ is such an organic fluid and is used, for example, as a coolant for highperformance electronics, low-temperature heat transfer applications, cooling of automotive batteries, just to mention a few. Thus, efficient designed fans for the transport of organic fluids are becoming more and more important in the process engineering. CFD-simulations are nowadays integral part of the design and optimization process of fans. For air at the most usual application conditions, i.e. no extreme temperatures or pressures, the ideal gas model is in good agreement with the real gas approach.

In the present study, this real gas approach for organic fluids have been investigated with CFD methods and, the deviation from the ideal gas model has been analyzed. For this purpose, a simulation model of a centrifugal fan with volute has been designed as a test case. First, the ideal gas model approach has been compared with the real gas approach model of Peng-Robinson for air using the commercial solver ANSYS CFX. Thereafter, the same comparison has been performed using the organic fluid Novec™.

After a detailed grid study, the entire fan characteristics, i.e. the design point and the off-design points, have been simulated and evaluated for each fluid (air and Novec™) and gas model (ideal gas and Peng-Robinson real gas). The steady state simulations of the centrifugal fan have been performed using the Frozen Rotor model. The simulation results have been compared, discussed and presented in detail.
Investigation of Unsteady Performance Characteristics of a Submersible Axial-Flow Pump for Different IGV and Blade Pitch Angles
Authors: Kim Youn-Sung , Shim Hyeon-Seok , Kim Kwang-Yong
Published: November 2019

This paper presents a study of the effects of blade pitch angle and inlet guide vane (IGV) angle on the performance of a submersible axial-flow pump. To analyze the interaction effects between the IGVs and the rotor blades, both steady and unsteady three-dimensional Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model were solved. Hexahedral meshes were used in the computational domain and a grid-dependency test was performed to obtain an optimal number of grid nodes. The performance curves obtained by numerical simulation showed good agreement with experimental data. The results show that the fluctuation of hydraulic efficiency and head coefficient increased significantly under overload conditions as the IGV setting angle increased. Additionally, both the steady and unsteady performance characteristics were shown to be quite dependent on the combination of IGV angle and blade pitch angle, because the relative velocity at leading edge played an important role in the performance under overload conditions.
Operational Performance and Locally Resolved Outflow of Brush Seals
Authors: Schur Fabian , Friedrichs Jens
Published: November 2019

As a result of the superior leakage efficiency of brush seals compared to conventional labyrinth seals, compliant contacting filament seals are used to increase the efficiency of jet engines as well as stationary gas and steam turbines. The widespread application of brush seals at different and varying pressure differences combined with variable contacting velocities at the rotor surface requires a profound understanding of the influences of different design parameters on the operational leakage performance. In order to systematically investigate the impact of different design parameters on sealing performance, a new cold air test rig was developed. The new test rig with rotating shaft enables hot-wire anemometry measurements downstream of the seals. These measurements provide insight into the locally resolved flow structure in addition to the integral leakage measurements. For the investigations, one welded and five different clamped brush seals at rotational speeds up to 3000rpm and pressure differences across the seals up to 500kPa are considered. Therefore, the influence of two different designs on the flow through the bristles is presented. For the clamped brush seals, variations of the front and backing plate are investigated. Additionally, the effects of bristle diameter and three different axial inclinations of the bristle pack on the sealing efficiency are shown. Furthermore, initial wear development during the first 30 to 60 hours of brush seal operation at varying experimental conditions is presented and linked to the design parameters. Consequently, the effects of major design aspects on the operational performance of brush seals are examined and presented.
Mixing of Dry Air With Water-Liquid Flowing Through an Inverted U-Tube for Power Plant Condenser Applications
Authors: Yousef Khaled , Hegazy Ahmed , Engeda Abraham
Published: November 2019

This paper presents a Computational Fluid Dynamic (CFD) simulation for dry air/water-liquid and two-phase flow mixing in a vertical inverted U-tube using the mixture multiphase and turbulence models. This study is to investigate the flow behaviors and underlying some physical mechanisms encountered in dry air/water-liquid flow in the inverted U-tube. Water flows through the inverted U-tube while the dry air is entrained using the side-tube installed after the water flow downward. The inverted U-tube is tested at water mass flow rates of 2,4,6 and 8 kg/s, air mass flow rates, 0.000614–0.02292 kg/s, with dry air volume fractions 0.2–0.9. The obtained results are compared with the experimental data for model validation and the present CFD model is able to give an acceptable agreement. Also, the results show that, at water mass flow rate of 2 kg/s, there are vortices and turbulent intensity disturbances are noticed at the inverted U-tube higher part, which refers to an air entrainment occurrence from the side-tube. Theses disturbances starts to be stabilized at air mass flow rate around 0.00736 kg/s and air volume fraction, αa = 0.75. This means, if the air mass flow rate increases above this limit, the air entrainment may be blocked. On the other side, at water mass flow rate of 4 kg/s, there are little noticed disturbances until air mass flow rate of 0.00368 kg/s and αa = 0.43 and thereafter stabilized. After this point for water mass flow rate of 4 kg/s, increasing air mass flow rate may block the water flow and the whole inverted U-tube system possible stop flowing. Therefore, this study is able to estimate the required operational conditions and mass ratios for stable air entrainment process. Beyond these operational conditions, air entrainment may be blocked and the whole system discontinues its normal induced gravitational flow. In addition, this study proves that the inverted U-tube is able to generate a vacuum pressure up to 53.382 kPa based on the present geometrical configuration. This generated low-pressure by the inverted U-tube can be used for engineering applications which are working under vacuum and need continuous evacuating form the dry air and non-condensable gases. Furthermore, these findings motivate the utilizing of inverted U-tube for the air evacuation purposes for less power consuming in power plants.
Numerical Design of a Partial-Support Axial Blood Pump
Authors: Liu Guangmao , Jin Donghai , Wang Mengyu , Gui Xingmin
Published: November 2019

Partial-support is the main support mode for “less sick” patients with severe heart failure. But there were fewer partial-support blood pumps for clinical use. An implantable partial-support axial blood pump was developed for heart failure patients. To gain better hemolytic performance and lower pump thrombus risk, the rotor blades were extended to the contractive section of the rotor hub while cone-bearing was adopted. The hydraulic and hemolytic performance of the blood pump was simulated and analyzed by computational fluid dynamics (CFD) method. The flow velocity, hydraulic efficiency, exposure time, scalar shear stress (SSS) and hemolytic performance of the axial blood pump was analyzed. The numerical results showed that the axial blood pump could produce a 1–8 Lpm flow rate with a 54.7–186.7 mmHg pressure head when the pump rotating from 9000 to 13000 rpm. The hydraulic efficiency and SSS distribution corresponded with the typical performance of a blood pump. The mean hemolysis index of the blood pump calculated by the Giersiepen’s model was 5.0 × 10−5%. After extending the rotor blades to the contractive section of the rotor hub, the spiral flow at the inlet of the rotor impeller was reduced. Hemolysis in the blood pump was improved because the exposure time was reduced and the blood damage caused by SSS was reduced.. The designed blood pump satisfies the clinical requirements of partial-assist for less-sick heart failure patients.
Numerical Simulation of Airflow and Ellipsoidal Particle Deposition in Human Upper and Central Respiratory Tract
Authors: Kiasadegh Morteza , Dehghani Zahra , Naseri Arash , Abouali Omid , Ahmadi Goodarz
Published: November 2019

Steady airflow pattern during a full breathing cycle in human upper and central respiratory tract was simulated by solving the Navier-Stokes and continuity equations. For ellipsoidal fiber trajectory analysis under cyclic breathing condition, several user defined functions (UDFs) were developed and coupled to the ANSYS-Fluent discrete phase model (DPM). The developed model accounted for solving the coupled translational and rotational equations of motion of ellipsoidal fibers. The airway passage model was extended from the vestibule to the fifth generation of the bronchial bifurcations obtained mostly from computed tomography (CT) scan. A constant flow rate of 15 L/min was used to simulate the normal breathing condition. The velocity and pressure fields for different regions of the respiratory track were evaluated and used for Lagrangian particle trajectory analysis. Total and regional depositions of each region for a range of ellipsoidal particle diameter and aspect ratios were evaluated and the results compared with the experimental data.
Experimental Study of Mixing of Two-Layer Density-Stratified Fluid by a Vortex Ring
Authors: Cao Lile , Ito Ryo , Degawa Tomohiro , Matsuda Yu , Takamure Kotaro , Uchiyama Tomomi
Published: November 2019

This study experimentally investigates the mixing of a two-layer density-stratified fluid of water (upper layer) and aqueous sodium chloride (NaCl) solution (lower layer) induced by the interaction between a vortex ring and the density interface. The vortex ring, which consists of water, is launched from an orifice in the upper layer toward the density interface, after which its motion, along with the behavior of the lower fluid, is visualized through a planar laser-induced fluorescence method. The Atwood number that expresses the nondimensional density jump across the density interface is set at 0.0055, and the Reynolds number Re of the vortex ring is varied from 2050 to 3070. The visualization experiment clarifies that the vortex ring penetrating the density interface is bounced while collapsing in the lower fluid. Furthermore, it elucidates that the bounced upper fluid entrains the lower fluid into the upper layer by inducing a second vortex ring consisting of the lower fluid. Thus, this study reveals the effect of Re on the mixing of the upper and lower fluid induced by the launched vortex ring.
Aerodynamic Design and Assessment of a Compact, Single Stage Axial Fan for Low Noise Emission
Authors: Kessler Daniel , Giesecke Daniel , Friedrichs Jens , Leuschner Jörg
Published: November 2019

Axial fans used in automotive and especially in locomotive cooling systems have to follow several, partially contrary specifications. In addition to geometrical and aerodynamic specifications, acoustic limits must be taken into account for new fan stage designs. Legislation will tweak axial fan requirements in the future further and further to lower their noise emission and maximize their efficiency.

The main focus of this paper is to design and test a single stage axial fan for locomotive cooling systems with high aerodynamic efficiency and low noise emissions. The fan stage is designed to be installed in a so-called tower construction. The available construction space is limited. Therefore, special attention is paid to reduce the axial length. Extensive blade sweep and dihedral are implemented in the design process. The fan stage design is validated by experimental tests including aerodynamic and acoustic studies.

During the aerodynamic studies, it was found that an often used approximation about the static pressure downstream the fan cannot be applied. Downstream the fan stage no further components are installed. Therefore, the static pressure at this position must be approximated. An alternative approach is developed using the results of additional studies including a downstream pipe and scaling factors. The results of the approach are plausible.

The acoustic tests were carried out at a fan test facility at TU Braunschweig. To evaluate the impact of the halls acoustic repercussion on the test results, different tests were done. Additionally, another axial fan was tested which has been investigated a few years ago in an acoustic test chamber.

The studies show the positive effect of the design methodology on aerodynamic and acoustic of the fan stage. All requirements were achieved as well as a reduction of the axial length of the fan stage.
Mechanism of Wall Turbulence Modulation With Premixed Hydrogen Combustion
Authors: Ohta Takashi , Onishi Yuta , Sakai Yasuyuki
Published: November 2019

In order to clarify the mechanism of modulation of turbulence structures such as quasi-streamwise vortices affected by a flame propagating toward a wall, we perform a direct numerical simulation of wall turbulence with premixed hydrogen-air combustion using a detailed chemical reaction mechanism. As a result, existing quasi-streamwise vortices in turbulence near the wall are found to be suppressed, disappearing as the flame approaches. Hence, the turbulent flow tends to become laminar. Moreover, according to the analysis of the vorticity transport equation, it is found that the suppression is due to thermal expansion of the flame rather than an increase in viscosity. From the viewpoint of chemical reactions, it is revealed that thermal expansion inside turbulence vortices is mainly caused by reactions involving H2 and H2O2.