bluuebunny/crossref_metadata_2025 huggingface dataset:
Flash sintering of 3YSZ/Al2O3‐platelet composites
Authors: Jia Yongjie , Su Xinghua , Wu Yajuan , Wang Zhenjun , Meng Leichao , Xu Xiqing , Zhang Anni
Published: November 2019

Preparation of 3YSZ/Al2O3‐platelet composites always requires high temperature, long duration, and/or high pressure. Herein, 3YSZ/Al2O3‐platelet composites are prepared at low temperature of 492°C‐645°C in 30 seconds by flash sintering under the electric field of 300‐800 V/cm. The influence of electric field and current limit on the densification and grain growth of composites is investigated. The onset temperature for flash sintering is determined by electric field, which is decreased with increasing the electric field. Under the constant electric field, the current limit has a great effect on the density and grain size of composite. The flash‐sintered 3YSZ/Al2O3‐platelet composites exhibit relatively high hardness and elastic modulus. Both Joule heating and defects generation are proposed to be responsible for the rapid densification in flash sintering. This work demonstrates the feasibility of employing the flash sintering to prepare ceramic composites with fine grain size.
Bump‐head sunfish Mola alexandrini photographed in the north‐west Pacific Ocean mesopelagic zone
Authors: Sawai Etsuro , Yamada Morihiko
Published: November 2019

We report a bump‐head sunfish Mola alexandrini (120–130 cm estimated total length) photographed from a manned submersible at a depth of 220 m off Kagoshima Prefecture, Japan, in May 2004. Mola alexandrini is often misidentified as the ocean sunfish Mola mola. This individual represented three records for this species: first record by a manned submersible, second record from the mesopelagic zone in the north‐west Pacific Ocean and a new distributional record from Kagoshima Prefecture, Japan.
Virucidal effects of various agents—including protease—against koi herpesvirus and viral haemorrhagic septicaemia virus
Authors: Amtmann Anette , Ahmed Ibrahim , Zahner‐Rimmel Petra , Mletzko Adam , Jordan Lisa Katharina , Oberle Martin , Wedekind Helmut , Christian Jürgen , Bergmann Sven Michael , Becker Anna Maria
Published: November 2019

In a search for alternative, environmentally friendly and effective disinfecting agents, a commercially available protease—Neutrase®—was tested in this work for inactivation of koi herpesvirus (KHV) and of viral haemorrhagic septicaemia virus (VHSV). For comparison, the stability of these viral pathogens in similar configurations at various pH values and concentrations of peracetic acid or quicklime, typically used for disinfection, was tested. Therefore, virus suspensions were incubated with various concentrations of different agents for 24 hr and the titre of the remaining infectious particles was determined by virus titration. Furthermore, the treatment of both viruses, with the agents at concentrations that were previously appointed as effective, was also examined in the presence of solid material (quartz sand). All procedures investigated in this study, including the protease treatment, were able to reduce the titre of KHV and VHSV below the detection limit of the titration. Although further studies are necessary, this is the first report of the application of a protease for the inactivation of the selected fish pathogens, demonstrating the great potential of the latter for disinfection.
The lived experience of adults with cystic fibrosis: what they would tell their younger selves about the gut
Authors: Cave L. , Milnes L. J.
Published: November 2019

Background

Little is known about adults’ experience of living with cystic fibrosis (CF) specifically in relation to the gut. However, their unique perspectives may be meaningful to children with CF and inform the understanding and practice of dietitians. The present study aimed to explore adults’ lived experience of the CF gut and how they learnt to manage the gut as they were growing up.

Methods

Semi‐structured interviews were conducted with adult inpatients (n = 10). Interviews were audio‐recorded, transcribed verbatim and accounts analysed using interpretative phenomenological analysis.

Results

Three super‐ordinate themes were identified: taking Creon, the learning process and this much I (now) know. Participants accounts of how CF affects the gut predominantly focused on taking Creon (pancreatin, Mylan). Various strategies were employed for coping with peer responses to taking Creon at school. Several participants reached adulthood before they understood and/or accepted that taking Creon consistently needed to be normal for them. Knowledge and understanding developed over time, with ‘CF experience’ and was shaped by family, CF care teams and other children with CF. All had unmet information needs when growing up. Having key explanations earlier, to make connections between eating, taking Creon, gaining weight and growth, did or would have helped most participants. Participants urged children to be assertive, ask questions and not only be involved in managing their diet and gut, but also begin to take control of this aspect of their CF.

Conclusions

Supporting development of knowledge, skills and confidence to manage diet and the gut needs to be integral to care throughout childhood.
The effect on pregnant women's prenatal attachment of a nursing practice using the first and second Leopold's maneuvers
Authors: Celik Meryem , Ergin Ayla
Published: November 2019

Objective

This study aimed to determine the effect on pregnant women's prenatal attachment of a nursing practice using the first and second Leopold's maneuvers.

Method

This experimental, randomized and controlled study was conducted in a pregnancy class of a training and research hospital in Kocaeli, Turkey from September 2016 to September 2017. Its sample included 100 pregnant women, 50 in the experimental group and 50 in the control group (https://www.random.org, accessed: 09.20.2016). Data were collected using a personal information form, the Prenatal Attachment Inventory (PAI) and the Fetal Position Awareness Scale (FPAS). The study offered education that included fetal development, the first and second Leopold's maneuvers, and Leopold's maneuvers were administered in the 28th week of the women's pregnancy and re‐administered in the 32nd and 36th weeks of pregnancy. No intervention was administered to the control group in these weeks, but the scales were administered.

Results

The sociodemographic, obstetric, social support and baby‐related characteristics of the groups were similar (p > .05). There were no statically significant differences between their mean PAI and FPAS scores in the 28th week of pregnancy (p > .05). The experimental group's mean PAI and the FPAS scores in the 32nd and 36th weeks of pregnancy were significantly higher than those of the control group (p < .01).

Conclusion

The study concluded that Leopold's maneuvers affected the pregnant women's prenatal attachment levels.
Health Empowers You: Impact of a School‐Based Physical Activity Program in Elementary School Students, Georgia, 2015‐2016
Authors: Hyde Eric T. , Gazmararian Julie A. , Barrett‐Williams Shannon L. , Kay Christi M.
Published: November 2019

BACKGROUND

Most youth in the United States do not meet the recommended 60 minutes of daily physical activity (PA). The school environment offers an opportunity to engage students in PA. The purpose of this study was to evaluate the impact of a comprehensive school‐based physical activity program on student PA across student‐level and school‐level characteristics.

METHODS

PA levels from 3294 fourth grade students in 24 intervention schools and 7 control schools in metropolitan Atlanta, Georgia were measured during the 2015‐2016 academic year. PA measures included daily steps in school, steps taken in physical education class (PE), and percent of PE class time spent in moderate‐to‐vigorous physical activity (MVPA). Intervention effectiveness was assessed using generalized estimating equations adjusting for sex and school‐level socioeconomic status (SES).

RESULTS

After adjusting for sex and school‐level SES, intervention students had significantly higher increases in average daily steps (p < .05), steps taken in PE (p < .01), and percent of PE class spent in MVPA (p < .01) than control students.

CONCLUSIONS

Our findings demonstrate the effectiveness of CSPAPs in increasing PA. Further research using randomized controlled trials of large‐scale implementations, longer follow‐up periods, and more diverse student sample is warranted.
A Community–Academic Partnership for School‐Based Nonviolence Education: The Healthy Power Program
Authors: Dunn Melissa , Drew Christa , O'Brien Joseph , Wood Michael , Mora Eriberto , Diener Sam , Perry Donna J.
Published: November 2019

BACKGROUND

Youth violence is a significant problem affecting community health. Community–academic partnerships can advance youth nonviolence education by synergizing the strengths of collaborators while working toward a common goal. We describe a collaboration between an urban public middle school, community nonprofit, and university‐based graduate school of nursing in implementing and evaluating the Healthy Power program, a school‐based youth nonviolence program for middle‐school boys.

METHODS

A participatory program evaluation approach was used to plan and implement evaluation of the Healthy Power program with a cohort of 8 students. Collaborative planning allowed for the selection of measures that reflected program objectives and were of value to community partners while also scientifically sound. A mixed‐methods approach included a focus group and a pretest–posttest with quantitative items and open‐ended questions.

RESULTS

While the quantitative pre‐posttest did not show any significant change, the open‐ended questions and focus group suggested that students had advanced their understanding and application of conflict resolution skills.

CONCLUSIONS

The findings support the usefulness of community–academic partnerships for peace/conflict resolution education and program evaluation. Such programs may benefit from mixed methods of evaluation.
Promotions and Race: An Analysis of Wage Returns and Job Satisfaction
Authors: Tripp Sophie , Fadlon Yariv
Published: November 2019

Using a nationally representative sample of workers in the United States, we find evidence to suggest the wage returns to promotions for black males are about 48 per cent of the wage returns that white males earn. As black males earn, on average, significantly less than white males, the gap in the wage returns to promotions creates a larger impact on the absolute returns. Despite the racial gap in the monetary reward to a promotion, we do not find evidence to suggest that black males are less satisfied with their job following a job promotion compared with white males.
Is spinal computed tomography necessary in pediatric trauma patients?
Authors: Eren Burak , Karagoz Guzey Feyza
Published: November 2019

Background

To investigate the prevalence of findings of spinal injury on computed tomography (CT) images of pediatric trauma patients and to define indicators for the possible presence of spinal injuries.

Methods

Spinal CT for pediatric trauma patients (age ≤ 12 years) over a 2‐year period was retrospectively evaluated for the presence of findings suggestive of spinal injury.

Results

Of the 773 patients reviewed, 19 (2.4%) showed traumatic spinal lesions on their spinal CT images. These patients were significantly older than those without spinal lesions (mean age 7.9 ± 3.3 years vs 6.1 ± 3.3 years; P = 0.02). The prevalence of spinal trauma was significantly lower in patients aged 0–8 years than in those aged 9–12 years (P = 0.025). Spinal injury was significantly higher in female patients (P = 0.014). Most of the spinal injuries were located at the lumbar and sacral vertebral levels, and most did not cause neurological complications or require surgical treatment. Important indicators of the possible presence of spinal injuries were pain, tenderness, or ecchymosis over the spine, a low Glasgow Coma Scale score (≤12), head injury (for cervical injuries), or intrathoracic injuries and pelvic fractures (for lumbar and sacral injuries).

Conclusions

Most spinal CT examinations for the diagnosis of spinal injuries in children did not show positive findings. Thus, many children were exposed to an unnecessary high dose of radiation. New clinical evaluation criteria and indicators should be defined to diagnose spinal injuries and avoid unnecessary radiological examinations.
The Political Dimension of Cash Transfers in Latin America and Sub‐Saharan Africa: A Comparative Perspective
Authors: Scarlato Margherita , d'Agostino Giorgio
Published: November 2019

This article compares the consolidated experience of conditional cash transfers in Latin America with a variety of models of cash transfers (CTs) in middle‐ and low‐income countries in Sub‐Saharan Africa. We explore the recent literature with the aim to highlight the underlying political economy factors that have underpinned the emergence and scaling up of various kinds of social protection strategies in the two regions. Some implications and policy suggestions are drawn regarding the opportunities and challenges for CTs in the future.

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Immunolocalization of c‐Fos, ELOVL5 and oestradiol in the ewe vulva in relation to oestrus behaviour after treatment with lipopolysaccharide
Authors: Dobson Hilary , Tilston Valerie , Ressel Lorenzo
Published: November 2019

Sudden activation of the stress axis by a lipopolysaccharide endotoxin (LPS) significantly reduces ewes' sexual attractivity to rams by delaying all signs of oestrous behaviour. To understand mechanisms involved in attracting male interest, we examined c‐Fos (nuclear activation), ELOVL5 (enzyme involved in pheromone synthesis) and oestradiol receptors (ER) using immunohistochemistry on ewe vulval tissue at 0, 31 and 40 hr in the ovarian follicular phase with or without exposure to LPS at 28 hr (5 groups of 4 ewes per group). While there was intense staining for immunoreactive (IR)‐c‐Fos and IR‐ELOVL5 in the vulval epithelium and sebaceous glands, there were no differences in intensity between groups of ewes. The absence of IR‐ER staining in vulval epithelium and sebaceous/sweat glands was unexpected. Differences in ram behaviour towards ewes in the ovarian follicular phase and after LPS treatment do not appear to involve quantitative changes in vulval c‐Fos, ELOVL5 or ER, but subtle qualitative differences in individual‐specific compounds (attraction pheromones) remain an option.
New Rural Community? Narratives from Second Home Owners about Everyday Life in a Tourist Region in Finnish Lapland
Authors: Tuulentie Seija , Kietäväinen Asta
Published: November 2019

Nowadays, second homes are important for rural development and rural communities in many parts of the world. Second home owners are more committed to the place than tourists and other occasional visitors. However, they are not counted as full members of the local community, which is often seen as a coherent group of like‐minded people. This study examines the concept of community in the context of second home owners in a popular tourist region of Finnish Lapland. The study is based on diaries kept for one year by ten second home owners. The diaries are analysed as narratives that record happenings that the writers see as worth narrating. They show that various social contacts as well as media and nature create the entirety of the attachment to the second home place. Social contact occurs in many places, from services to nature environments. Also residents’ association seems to be an important forum of social influence. The authors suggest that more spaces for socialising are needed in order to have interaction between permanent residents and second home owners.
Competing Explanations of Competing Explanations: Accounting for Conflict Between Scientific and Folk Explanations
Authors: Shtulman Andrew , Legare Cristine H.
Published: November 2019

People who hold scientific explanations for natural phenomena also hold folk explanations, and the two types of explanations compete under some circumstances. Here, we explore the question of why folk explanations persist in the face of a well‐understood scientific alternative, a phenomenon known as explanatory coexistence. We consider two accounts: an associative account, where coexistence is driven by low‐level associations between co‐occurring ideas in experience or discourse, and a theory‐based account, where coexistence reflects high‐level competition between distinct sets of causal expectations. We present data that assess the relative contributions of these two accounts to the cognitive conflict elicited by counterintuitive scientific ideas. Participants (134 college undergraduates) verified scientific statements like “air has weight” and “bacteria have DNA” as quickly as possible, and we examined the speed and accuracy of their verifications in relation to measures of associative information (lexical co‐occurrence of the statements' subjects and predicates) and theory‐based expectations (ratings of whether the statements' subjects possess theory‐relevant attributes). Both measures explained a significant amount of variance in participants' responses, but the theory‐based measures explained three to five times more. These data suggest that the cognitive conflict elicited by counterintuitive scientific ideas typically arises from competing theories and that such ideas might be made more intuitive by strengthening scientific theories or weakening folk theories.
The unusual di‐domain structure of Dunaliella salina glycerol‐3‐phosphate dehydrogenase enables direct conversion of dihydroxyacetone phosphate to glycerol
Authors: He Qinghua , Toh Joel Dewei , Ero Rya , Qiao Zhu , Kumar Veerendra , Serra Aida , Tan Jackie , Sze Siu Kwan , Gao Yong‐Gui
Published: November 2019

Dunaliella has been extensively studied due to its intriguing adaptation to high salinity. Its di‐domain glycerol‐3‐phosphate dehydrogenase (GPDH) isoform is likely to underlie the rapid production of the osmoprotectant glycerol. Here, we report the structure of the chimeric Dunaliella salina GPDH (DsGPDH) protein featuring a phosphoserine phosphatase‐like domain fused to the canonical glycerol‐3‐phosphate (G3P) dehydrogenase domain. Biochemical assays confirm that DsGPDH can convert dihydroxyacetone phosphate (DHAP) directly to glycerol, whereas a separate phosphatase protein is required for this conversion process in most organisms. The structure of DsGPDH in complex with its substrate DHAP and co‐factor nicotinamide adenine dinucleotide (NAD) allows the identification of the residues that form the active sites. Furthermore, the structure reveals an intriguing homotetramer form that likely contributes to the rapid biosynthesis of glycerol.
Description of Gas Hydrate Using Digital Core Technology
Authors: Li Shuxia , Li Shuang , Pang Weixin
Published: November 2019

As a new energy source with abundant resources, clean combustion, and high calorific value, gas hydrates have received much attention in recent years. However, the sampling cost is relatively high because the gas hydrates exist in deep seas and frozen soils. Digital core technology can reconstruct hydrate cores without destroying rock samples. In this paper, the advanced image processing technology is used to process the gas hydrate computed tomography (CT) scan image, and a three-dimensional hydrate digital core model is constructed, which can depict the sample's pore structure features. avizo software is used for filtering and image segmentation; the porosity is calculated as 35.90%, the hydrate saturation is 36.92%, and the pore network model is established. The pore radius is mostly distributed in 0–1 × 102 µm, and the average pore radius is 168.131 µm; the throat radius is mostly distributed in 0.5–1×102 µm. The seepage simulation on the pore scale is carried out, and the absolute permeability is calculated to be 76.8 µm2. Compared with conventional physical experiments, the digital core technology can obtain the true distribution of the pores inside the hydrate core, which is very helpful for analyzing the physical parameters of the hydrate core. The digital core technology is of great significance in the study of hydrate reservoirs.
Stagnation Flow and Heat Transfer From a Finite Disk Situated Perpendicular to a Uniform Stream
Authors: aus der Wiesche Stefan
Published: November 2019

The stagnation flow and heat transfer from the blunt surface of a finite circular disk subjected to a uniform stream of an incompressible fluid is revisited in this paper. A laminar boundary layer analyses was carried out employing the method developed by Frössling. The involved auxiliary functions were calculated for several Prandtl numbers. It was found that the exact knowledge of the velocity at the outer edge of the boundary layer was essential to achieve an accurate velocity solution. In addition to the analytical work, computational fluid dynamics (CFD) simulations and an experimental study were carried out. The analytical treatment enabled a clear discussion of the effect of the Prandtl number on convective heat transfer from a blunt disk. A primary and a secondary effect were distinguished based on the rigorous analytical treatment. The boundary layer theory offered a rather efficient calculation method, and its results were in an excellent agreement with available literature data.
On Scouring Efficiency of Flush Waves in Sewers: A Numerical and Experimental Study
Authors: Alihosseini Maryam , Thamsen Paul Uwe
Published: November 2019

In sewer sediment management, the removal of depositions using hydraulic flushing gates has recently gotten great attention. Despite numerous investigations, the complex process of sediment transport under flushing waves is not yet well understood. The present work aims to calibrate and validate a coupled computational fluid dynamics and discrete element method (CFD-DEM) to study the fluid-sediment interaction in sewers. The CFD part of the simulation was carried out in the software Ansys Fluent which is two-way coupled to the DEM software EDEM. The multiphase model volume of fluid (VOF) was used to simulate the flushing wave, while the sediments were handled as DEM particles using the discrete phase model (DPM). To validate the 3D model, experimental work has been performed in a circular laboratory pipe with sand and gravel of different size distributions. A construction of a sluice gate was installed to realize the flushing event, which is similar to a dam-break wave. The evolution of the sediment bed and the scouring efficiency of the waves were examined under different flushing conditions. The results showed that the CFD-DEM method could be used to investigate the performance of flushing devices and various features of sediment transport which are not easy to obtain in the laboratory or field.
Visualizing Test on the Distribution Rule of Coarse Particles in a Double Blade Pump
Authors: Wu Xianfang , Tian Xiao , Tan Minggao , Liu Houlin
Published: November 2019

As a typical fluid mechanics problem, pump blockage has always been a hot research topic. The obtaining of the distribution of coarse particles in the solid-liquid two-phase flow pump is the basis of improving its non-blocking performance. High-speed photography technique is applied to do visualizing test and research on the distribution of coarse particles in a double blade pump. The effects of particle concentration, particle density and particle diameter on the distribution of coarse particles in the solid-liquid two-phase flow pump at different phases are studied. Besides, the variation of hydraulic performance of the double blade pump under different parameters is also analyzed. The results show that the particles in the impeller mainly located in the vicinity of the blade pressure surface, and the distribution of the particles in each section of the volute is quite different. The great difference in particle density can result in obviously uneven distribution of particles. With the increase of particle diameter, particle density and particle concentration, the pump head and efficiency both decrease while the shaft power increase on the contrary. This research results can also provide a basis for the optimization design of solid-liquid two-phase flow pumps.
Experimental Investigation on Flow and Breakup of Two-Dimensional Liquid Jets
Authors: Jaberi Amin , Tadjfar Mehran
Published: November 2019

Studying of injectors with non-circular geometries has recently come to the spotlight of researchers as a potential technique to improve the liquid injection characteristics of different systems. In this work, the flow physics and breakup of two-dimensional liquid jets issued from flat slits into still air were experimentally investigated. Three injectors with aspect ratios of 30, 60 and 90 and thickness of 0.35 mm were manufactured to obtain two-dimensional liquid flow at the nozzle exit. The tests were performed for a wide range of volume flow rate, varying from 10 L/h to 240 L/h. Backlight shadowgraphy and high speed photography were employed to capture the flow dynamics of the jets. In order to capture every detail of the flow, photos of the liquid jet were taken from two views with 90° from each other. Using the visualizations, different regimes of the jet flow were explored and a regime map was proposed to distinguish these regimes based on the non-dimensional parameters of the liquid jet. Moreover, quantitative description of the main features of jet flows were obtained using an in-house image processing program. Measurements of different parameters including convergence length, maximum width, breakup length, sheet thickness to name a few, were conducted.
Visualization of Microbubble Distribution Inside Turbulent Boundary Layer Along Flat and Curved Solid Surfaces
Authors: Murai Yuichi , Saito Daichi , Ushiyama Daiki , Park Hyun Jin , Tasaka Yuji
Published: November 2019

How microbubbles behave inside turbulent boundary layers are investigated experimentally. Water electrolysis is applied for generation of microbubbles in water, of which electrodes are flash mounted on the solid wall in the upstream section of the measurement area. Four kinds of solid surfaces are examined to compare the microbubble distribution. For a circular cylinder of the radius R = 22 mm at Re = 5,000, we found that microbubbles depart from the surface earlier than the liquid boundary layer. For an elliptic cylinder of the curvature radius of R = 60 mm and a hydrofoil of NACA0040, microbubble injection made the separation point move downstream in the range of 9,000 < Re < 90,000. To compare the effect with the cases of flat solid surfaces (R = infinity), we visualized three-dimensional distribution of microbubbles with color-coded volumetric illumination technique. The result has shown formation of microbubble clusters intermittently, which has Coulomb potential due to negative electric charge on bubble interfaces.
A Statistical Approach for Modeling Stochastic Rebound Characteristics of Solid Particles
Authors: Haider G. , Asgharpour A. , Zhang J. , Shirazi S. A.
Published: November 2019

During production of oil and gas from wells, solid particles such as removed scales or sand may accompany petroleum fluids. These particles present in this multiphase flow can impact inner walls of transportation infrastructure (straight pipelines, elbows, T-junctions, flow meters, and reducers) multiple times. These repeated impacts degrades the inner walls of piping and as a result, reduce wall thickness occur. This is known as solid particle erosion, which is a complex phenomenon involving multiple contributing factors. Prediction of erosion rates and location of maximum erosion are crucial from both operations and safety perspective. Various mechanistic and empirical solid particle erosion models are available in literature for this purpose. The majority of these models require particle impact speed and impact angle to model erosion. Furthermore, due to complex geometric shapes of process equipment, these solid particles can impact and rebound from walls in a random manner with varying speeds and angles. Hence, this rebound characteristic is an important factor in solid particle erosion modeling which cannot be done in a deterministic sense. This challenge has not been addressed in literature satisfactorily. This study uses experimental data to model particle rebound characteristics stochastically. Experimental setup consists of a nozzle and specimen, which are aligned at different angles so particles impact the specimen at various angles. Information regarding particle impact velocities before and after the impacts are obtained through Particle Tracking Velocimetry (PTV) technique. Distributions of normal and tangential components of particle velocities were determined experimentally. Furthermore, spread or dispersion in these velocity components due to randomness is quantified. Finally, based on these experimental observations, a stochastic rebound model based on normal and tangential coefficients of restitutions is developed and Computational Fluid Dynamics (CFD) studies were conducted to validate this model. The model predictions are compared with experimental data for elbows in series. It is found that the rebound model has a great influence on erosion prediction of both first and second elbows especially where subsequent particle impacts are expected.
Multi-Objective Optimization of a High Specific Speed Centrifugal Volute Pump Using 3D Inverse Design Coupled With CFD Simulations
Authors: Zhang Luying , Davila Gabriel , Zangeneh Mehrdad
Published: November 2019

This paper presents three different multi-objective optimization strategies for a high specific speed centrifugal volute pump design. The objectives of the optimization consist of maximizing the efficiency and minimizing the cavitation while maintaining the Euler head. The first two optimization strategies use a 3D inverse design method to parametrize the blade geometry. Both meridional shape and 3D blade geometry is changed during the optimization. In the first approach Design of Experiment method is used and the efficiency computed from CFD computations, while cavitation is evaluated by using minimum pressure on blade surface predicted by 3D inverse design method. The design matrix is then used to create a surrogate model where optimization is run to find the best tradeoff between cavitation and efficiency. This optimized geometry is manufactured and tested and is found to be 3.9% more efficient than the baseline with little cavitation at high flow. In the second approach the 3D inverse design method output is used to compute the efficiency and cavitation parameters and this leads to considerable reduction to the computational time. The resulting optimized geometry is found to be similar to the more computationally expensive solution based on 3D CFD results. In order to compare the inverse design based optimization to the conventional optimization an equivalent optimization is carried out by parametrizing the blade angle and meridional shape. Two different approaches are used for conventional optimization one in which the blade angle at TE is not constrained and one in which blade angles are constrained. In both cases larger variation in head is obtained when compared with the inverse design approach. This makes it impossible to create an accurate surrogate model. Furthermore, the efficiency levels in the conventional optimization is generally lower than the inverse design based optimization.
Simulations of Tubular UAV With Vectored Thrust in Near-Hovering Regimes in the Presence of Side Winds
Authors: Matveev Konstantin I. , Wheeler Miles P.
Published: November 2019

An innovative unmanned aerial vehicle with a tubular body and a vectored thruster is considered in this study. In order to optimize the vehicle design and develop effective means for its control, aerodynamic characteristics of this vehicle need to be known. Computational fluid dynamics studies employing STAR-CCM+ software have been carried out for this UAV in near-hovering regimes. Aerodynamic simulations employed the SST k–ω turbulence model, γ transition model, and a virtual actuator disk model. After conducting a validation study with a cylinder in axial flow, modeling of the UAV setup was completed for a range of propulsor orientations and cross winds. The aerodynamic phenomena are found to become more complex with increasing the propulsor angle with respect to the main body axis and in stronger cross winds due to interactions between the incident flow, the propulsor jet, and the body surface. At the propulsor deflection angle of 15°, the horizontal aerodynamic force on the body was augmented by 0.02–0.07 of the propulsor thrust magnitude in various wind conditions, whereas the axial downward force increased by 0.01–0.03 of the thrust. In cross winds with the relative velocity magnitude of 0.65, the horizontal aerodynamic force on the body increased by about 0.25 of the propulsor thrust magnitude, while the axial downward force increased by about 0.05 of the thrust.
Experiments on Turbulent Air-Water Swirling Flow in a Pipe With a Circular Disk
Authors: Tianxing Zhang , Almheiri Ayesha , Khezzar Lyes , Alshehhi Mohamed , Salam Saqib
Published: November 2019

This paper presents an experimental study conducted on turbulent single and two-phase swirling flow in a circular pipe with a bluff body. Laser Doppler Velocimetry (LDV) was used to measure liquid velocity radial profiles. The measurements were performed in a closed water-air loop system with a horizontal test section of length 610 mm and 41 mm internal diameter. The measurement campaign was performed at different axial locations to document the flow field without and with the presence of an air core respectively. The measurements were conducted with water flow rates which corresponded to Reynolds numbers based on pipe diameter and average liquid velocity of 14,500 and 19,450 for single phase and liquid-gas swirling flow, respectively. Analysis of the results reveals a more noticeable reverse flow along the whole pipe intensifying rather than being dampened as expected due to the swirl decay. High-speed photography shows that at a GLR = 0.3% the gas core does not touch the bluff body but breaks down just ahead of the disk surface.
Study on the Influence of Centrifugal Pump Inlet Flow Field Instability and Methods of Adjustment
Authors: Qian Bo , Chen Jinping , Wu Peng , Huang Bin , Wu Dazhuan
Published: November 2019

The quality of centrifugal pump inlet flow field is an important factor that affecting the performance of pump. Studies have proved that the vortex in the inlet area can also bring an extra flow instability to pump, which results in a hydro-induced vibration. This phenomenon is more common and significant in the pumps with an elbow tube, which is often applied to minimize installation size, before pump inlet. Therefore, it is necessary to look into the influence of inlet flow field instability on pump performance especially the vibration performance. The methods of adjusting pump inlet flow field is also worthy of being studied in the meantime. In this study, the influence of inlet vortex on the performance of centrifugal pump with an elbow inlet tube is investigated by means of CFD analysis. The flow is significantly affected when going through the elbow tube inlet and then turbulence is generated as a result, which enters the impeller at the next moment. The turbulence brings an asymmetrical flow condition at the impeller suction area, which can intensify pressure pulsation and hydro-induced vibration. In order to reduce the turbulence, two modifications on the elbow inlet tube are investigated in this study. A specially designed vane is deployed inside the inlet tube in the MOD1, and the MOD2 is added with two splitter vanes on the basis of the MOD1. The turbulent flow in the elbow inlet tube can be reordered as it is controlled by the vanes. The difference on pump performances that the inlet vane has made is specifically simulated and compared. The flow fields of the inlet tube influenced by the vane is also investigated on the vortex distribution and velocity vector distribution. The MOD1 has a generally smaller pressure fluctuation amplitude than the prototype in the impeller inlet area while the pressure fluctuation amplitude of the MOD2 in the impeller inlet area is stronger than the prototype. It is considered as a consequence of multiple effects, which are, the rise of velocity because of flow area replacement by the vanes making the flow field less stable as well as the wake flow induced by the vanes increasing the instability of the flow field. Therefore, although the flat vanes can help adjusting the flow field, their negative influences also act in the opposite way. It is worthwhile to find the balance between the benefits and the costs in flow field stability of installing adjusting vanes. The selection of parameter, number and installation position needs to be further investigated. The numerical results of the MOD1 are also validated through experimental investigations.
Theoretical and Numerical Studies on the Performance of Shock Vector Control
Authors: Wu Kexin , Kim HeuyDong
Published: November 2019

The transverse injection into a supersonic flow is a significant application that appeared in numerous aerodynamic applications, such as drag reduction and fluidic thrust vectoring control. Nowadays, fluidic thrust vector control is gradually replacing mechanical thrust vector control to redirect various air vehicles. Shock vector control is very popular in fluidic thrust vector control field due to lots of advantages, such as simple structure, more integrated control effect, and quick vectoring response. In present works, numerical simulations and theoretical analyses were conducted to investigate the shock vectoring performance in a three-dimensional rectangular nozzle. To validate the reliability and accuracy of the present numerical methodology, static pressure distributions along upper and lower nozzle surfaces in the symmetry plane were compared with experimental data published by NASA. It was evident that present numerical results present great approximations with experimental data. Control variables of the slot injector were studied, which not only include slot length and slot width but also contain uniform mass flow ratio and injection pressure ratio. Performance variations were illustrated clearly, such as static pressure distributions along upper and lower nozzle surfaces, deflection angle, resultant thrust coefficient, and thrust efficiency. Useful conclusions were obtained for further investigations on shock vector control.
Experimental Investigations of a Comb-Like Film Cooling Scheme
Authors: Li Hao-Ming , Ghaly Wahid , Hassan Ibrahim
Published: November 2019

The performance of a simple slot is perfect, but it does not have structural integrity. A new advanced cooling scheme with perfect performance and practical structural integrity is presented. Based on the crucial effect of the counter-rotating vortex pair (CRVP) on the film cooling effectiveness (η), the new scheme is composed of a comb-like structure and a blind slot, in which the comb structure maintains the mechanical strength, and the blind slot is intended to eliminate the CRVP and produce a smooth coolant film. The new scheme is investigated experimentally with the transient thermochromic liquid crystal (TLC) technique. Two classic geometries, the cylindrical hole and the simple slot, were also measured. The agreement of their results with the published data validated the present experimental facilities. The experimental results of the Comb scheme demonstrated that, with practical structural integrity, the new scheme has perfect performance, which bears comparison with the simple slot. Consequently, the success of the Comb scheme proved the crucial CRVP effect on η.
Experimental Study of Thermal Performance and Flow Behaviour With Winglets Vortex Generators in a Circular Tube
Authors: Nurizki A. , Islam Md. , Alam Md.
Published: November 2019

Vortex generator (VG) is one of the passive techniques which could improve the heat transfer with relatively low pressure drop. Vortex generators create streamwise longitudinal vortices which does not decay until far downstream that leads to have higher heat transfer with a lower pressure drop. The objectives of this experiment were to study the heat transfer and flow characteristics of fully developed turbulent flow due to different arrangement of VGs in a tube. The experiments were performed by using delta winglet vortex generators in a 52 mm circular copper tube. The flow regime varied from 6000 to 27000 Reynolds number. Four vortex generators with 45° angle of attack were used inside the circular tube. Different parameters of the VGs studied in this experiment such as lengths (L = 10, 15, and 20 mm) and arrangements (R = 0° to −15°). The results indicate that the length affected friction factor (f) and Nusselt number (Nu) significantly. L20 reached the highest f and Nu. The staggered arrangement concludes a significant drop on friction factor and a significant increase on Nusselt number. Consequently, the thermal performance of all staggered arrangement cases could reach a significant rise compared to the inline arrangement. The oil flow visualization could track down the trace of vortex behind the VG. The inline arrangement showed a strong vortex formed as a result of VG which was related to higher f while the staggered arrangement indicated a weak vortex.
Numerical Method for Studying Bearing Gap Pressure Wave Development and Subsequent Performance Mapping of Externally Pressurized Gas Journal Bearings
Authors: Lawrence Tom M. , Kemple Marvin D.
Published: November 2019

In previous work, numerical methods were developed to determine the pressure waves (pressure distribution) in the bearing gap of round externally pressurized gas bearings (EPB’s) that were pressurized through porous liners (PL bearings) or through liners with rows of feedholes (FH bearings). When integrated and differentiated these pressure portraits yield the net hydrodynamic force (FH) between the shaft and the bushing and the mass flow rates through the bearing gap. These results successfully replicated force-deflection curves and mass flow rate data for experimentally tested prototype FH and PL bearings over a wide range of mass flow constriction and clearances. Subsequently the numerical study was expanded to a broader design space of clearance and mass flow compensation. Also, a bearing performance mapping method of mapping the normalized bearing load over the clearance-eccentric deflection plane was developed for different levels of mass compensation. These performance maps produced a very interesting result as they indicated certain areas in the design space of FH bearings where static instability (negative stiffness) would be encountered. This static instability was not observed in the experimental data but is noted in references as known to occur in practice. Because this numerical method is based on the development of pressure wave portraits, the FH pressure wave could then be “dissected” in the areas of the onset of static instability which gave much insight as to the possible causes of static instability. This initial work, then, was perhaps the first to predict where in design space static instability would occur and yield some insight via examination of the corresponding pressure waves as to the cause. The numeric techniques developed, however are in no way limited to non-rotating bearings but are extensible to rotating bearings. The method is also easily extensible to examination of any configuration of feedholes or orifices. Nor is it limited to parallel deflections but can yield results for unbalanced loads. The method is also not limited to round bearings but can be applied to any cross-section configuration of bearing gap cross section such as a 3 lobed bearing or a slotted 3 lobed bearing. Examination of the resulting pressure wave development patterns for different scenarios can be examined to garner insight as to the causes of differing performance that can be applied to alterations towards optimization. Thus sharing in detail the developed numerical method underlying these studies seems worthwhile.
Experimental Study on the Friction Drag Reduction of Hydrogel Paint in a Boundary Layer on Flat Plate
Authors: Takagi Youhei , Hino Takanori , Nishimura Masanari , Aso Hiromi
Published: November 2019

The drag reduction effect of hydrogel paint was experimentally investigated with the resistance test in a circular water tank. The hydrogel and non-hydrogel paints were coated on the 1.7-meters flat plate and the total drag force was measured with a one-component force meter up to the middle Reynolds number of 1.5 × 106. The attachment of turbulence stimulator at the leading edge on the plate was also considered. The remarkable drag reduction was observed at the low Reynolds number of laminar-turbulent transition region and the hydrodynamic mechanism of its drag reduction was discussed.
Optimizing a Segmented Transmission Line Model for Dynamic Flows in Arbitrarily Tapered Pipelines
Authors: Wiens Travis
Published: November 2019

Previous work by the authors has presented a new method of modeling dynamic laminar flows in pipelines with changing cross sectional area. This method utilizes a number of Transmission Line Models (TLM), each with a single linear taper, as segments to model the pipeline. The Segmented Transmission Line Model (STLM) allows for fast computation, especially with the use of a variable time-step ODE solver for a system-level simulation (typically required for modeling of fluid power components). This paper presents an optimized version, including best practices for segmenting the pipeline based on accuracy and computation time.