bluuebunny/crossref_metadata_2025 huggingface dataset:
Prevalence of Helicobacter pylori infection with healthy subjects in Japan
Authors: Hirayama Yoji , Kawai Takashi , Otaki Junji , Kawakami Kohei , Harada Yoshimi
Published: December 2014

Background and Aim

Only few large‐scale epidemiological studies have examined the prevalence of Helicobacter pylori (H. pylori) infection in Japan. The aim of the present study was to estimate the prevalence and incidence of H. pylori infection in Japan in terms of gender, age and region.

Methods

Serum anti‐H. pylori antibody testing was included in workers' annual health checks conducted by T‐company's health insurance association in 2008. The testing was continued for the next 5 years in 35‐year‐old subjects.

Results

The total number of subjects was 21 144 (18 398 males and 2746 females). Stratified for age, there were 5016 subjects (male : female = 4219:797) in their 30s, 8748 (7770:978) in their 40s, 5589 (4807:782) in their 50s, and 1769 (1584:185) in their 60s. The H. pylori seropositive rate (male : female) was 27.5% (27.5:27.7) overall, 18.0% (18.3:16.1) in subjects in their 30s, 22.9% (22.7:24.7) in those in their 40s, 37.4% (37.2:38.2) in those in their 50s, and 46.1% (45.7:49.2) in those in their 60s. The prevalence of H. pylori seropositivity increased as age increased; however, no significant differences were seen between genders or among regions (χ2 test).

The numbers of 35‐year‐old subjects from 2008 to 2012 were 1072, 1107, 941, 1065, and 940, respectively. The corresponding H. pylori seropositive rates were 17.4, 17.4, 14.3, 13.3, and 14.0%, respectively.

Conclusion

The Japanese H. pylori infection rate had already declined to 27.5% in 2008, with subjects in the 35–70 age range. The prevalence of H. pylori infection is also decreasing gradually from 2008 to 2012.
Evaluation of gastric cancer diagnosis using new ultrathin transnasal endoscopy with narrow‐band imaging: Preliminary study
Authors: Kawai Takashi , Yanagizawa Kyosuke , Naito Sakiko , Sugimoto Hiroko , Fukuzawa Masakatsu , Gotoda Takuji , Matsubayashi Jun , Nagao Toshitaka , Hoshino Sumito , Tsuchida Akihiko , Moriyasu Fuminori
Published: December 2014

Background and Aim

The new developed ultrathin transnasal endoscope, the GIF‐XP290N, makes possible a resolving power similar to the GIF‐H260 at a distance of 3 mm. In this study, using the GIF‐XP290N, we evaluated whether endoscopic diagnosis (discrimination between benign and malignant) of gastric lesions is possible using nonmagnified narrow‐band imaging (NBI) endoscopy.

Methods

The subjects were 255 consecutive patients who underwent screening of the gastrointestinal tract using new ultrathin transnasal endoscopy. Their average age was 65.2 ± 11.4 years. The male‐female ratio was 2.5:1. All cases were examined using conventional white‐light imaging (WLI) and nonmagnified NBI. When a depressed lesion was detected in the stomach, it was examined using WLI, then NBI close examination (at about 3 mm). We observed the mucosal structure of the lesion using close visualization with NBI. Concerning mucosal structural changes, we looked for a clear demarcation line between the lesion and the surrounding mucosa, and loss, irregularity, or nonuniformity of the lesion mucosal microsurface pattern.

Results

A total of 52 depressed lesions were examined. The histological diagnosis was cancer for 8 lesions, and noncancer for 44 lesions. WLI examination yielded a sensitivity of 50.0% (4/8), specificity of 63.6% (28/44), and accuracy 61.5% (32/52). On the other hand, NBI close examination yielded a sensitivity of 87.5% (7/8), specificity of 93.2% (41/44), and accuracy of 92.3% (48/52), significantly higher.

Conclusion

NBI close examination using ultrathin transnasal endoscopy enables mucosal diagnosis even without magnification and was considered to be an effective technique for improving endoscopic diagnosis.
THE EFFECT OF BASEMENT FAULT REACTIVATION ON THE TRIASSIC – RECENT GEOLOGY OF KURDISTAN, NORTH IRAQ
Authors: Burberry C. M.
Published: December 2014

The Zagros orogenic belt is underlain by a complex faulted Precambrian basement. Major fault trends originating in this basement have been invoked to explain large‐scale structural changes along the strike of the orogen, e.g. the development of the Kirkuk Embayment (Kurdistan, Iraq) and the Lurestan Salient (Iran). However, within the Kirkuk Embayment, these structural trends have not previously been considered as an interacting group of faults which are periodically reactivated. This contribution first presents a revised basement fault map for the Kirkuk Embayment, created from interpreted gravity data, existing fault maps and remote sensing lineament analyses. This map is then compared to surface structure maps, published facies maps and source rock maturity data using GIS techniques. The object is to define the relationship between the basement faults and surface structures, fades and source‐rock maturity through time.

Surface anticline orientation and location, as well as a number of major facies changes within the cover sequence, and the maturity of Triassic source rocks, are constrained by the interaction of the Najd and Transverse fault trends. A third basement trend, the Nabitah trend, has a more subtle effect on Phanerozoic geology. The Kirkuk Embayment can be divided into a series of semi‐independent basement blocks, defined by these basement fault trends. The interaction of these semi‐independent blocks has created local but predictable differences in surface structures, sediment thickness and facies, and variations in the maturity of Triassic source units across the Kirkuk Embayment. An understanding of the location and behaviour of basement faults within this hydrocarbon province is therefore a valuable predictive tool in exploration.
Formation of a small impact structure discovered within the Agoudal meteorite strewn field, Morocco
Authors: Lorenz C. A. , Ivanova M. A. , Artemieva N. A. , Sadilenko D. A. , Chennaoui Aoudjehane H. , Roschina I. A. , Korochantsev A.V. , Humayun M.
Published: December 2014

A relic impact structure was recognized within the strewn field of the Agoudal iron meteorite. The heavily eroded structure has preserved shatter cones in a limestone basement, and remnants of autochthonous and allochthonous breccias. Fragments of iron incorporated into the allochthonous breccia have a chemical composition (Ni = 5.16 wt%, Ir = 0.019 ppm) similar to that of the Agoudal meteorite, supporting a syngenetic origin of the strewn field and the impact structure. The total recovered mass of Agoudal meteorite fragments is estimated at approximately 500 kg. The estimated size of the SE–NW‐oriented strewn field is 6 × 2 km. Model calculations with minimal preatmospheric size show that a similar meteorite strewn field plus one small crater with observed shock effects could be formed by fragmentation of a meteoroid approximately 1.4 m in diameter with an impact angle of approximately 60° from the horizontal. However, the most probable is an impact of a larger, 3–4 m diameter meteoroid, resulting a strewn field with approximately 10 craters, 10–30 m in diameter each, plus numerous meteorite fragments. The calculated scattering area of meteorite shrapnel ejected from these impact craters could completely cover the observed strewn field of the Agoudal meteorite.
Disempowered, passive and isolated: how teenage mothers' postnatal inpatient experiences in the UK impact on the initiation and continuation of breastfeeding
Authors: Hunter Louise , Magill‐Cuerden Julia , McCourt Christine
Published: December 2014

Teenage mothers in the UK and other developed English‐speaking nations are among those least likely to breastfeed. Evidence suggests more young mothers intend to breastfeed than actually start, indicating that their post‐birth experiences militate against initiating breastfeeding. We aimed to explore how the inpatient experiences of a group of young women who gave birth as teenagers influenced their feeding decisions and experiences, and ascertain their ideals for breastfeeding support. Six focus groups or interviews were conducted with 15 women aged 16–20 who had intended to breastfeed or breastfed. Women were recruited from teenage parent groups in Oxfordshire, UK. Ethical approval was obtained from the relevant authorities. Data were analysed inductively using a thematic approach. Three overriding themes of ‘postbirth experience on Labour Ward: disempowered and passive’; ‘the postnatal ward: alien, alone and exposed’; and ‘being there: a need for relational support’ were identified. Sub‐themes on Labour Ward were ‘feelings at birth: ‘so tired and so dazed’; ‘deliver, stitch, dress’; and ‘initiating feeding’. Participants described care that followed set routines, discouraging their initiating breastfeeding by compounding feelings of dependence and encouraging a passive role as midwives took control, often deciding when and how babies should be fed. Sub‐themes on the postnatal ward were ‘an alien environment’; ‘feeling exposed and judged’; and ‘miscommunications’. The young mothers' breastfeeding support requirements reflected those known to be desired by older women, but they particularly wanted guidance and esteem support to be provided by a health professional, while looking to their peers for emotional support.
Rare cause of absence of femoral arterial pulse: Bilateral common iliac artery hypoplasia
Authors: Tekgündüz Kadir Şerafettin , Ceviz Naci , Kantarcı Mecit , Demirelli Yaşar , Olgun Haşim , Caner İbrahim , Şahin İrfan Oğuz , Yolcu Canan
Published: December 2014

Congenital anomaly of the iliac arteries is rare, and, given that patients are generally asymptomatic, diagnosis in the newborn period is difficult. Herein is presented the case of a newborn with bilateral hypoplasia of the common iliac arteries, seen on multi‐slice computed tomography while investigating the absence of femoral pulse. This anomaly is a rare cause of absence of femoral arterial pulse.
Successful treatment of relapsing autoimmune thrombotic thrombocytopenic purpura with rituximab
Authors: Sankararaman Senthilkumar , Jeroudi Majed , Ibrahim Hassan
Published: December 2014

Thrombotic thrombocytopenic purpura (TTP) is a rare but life‐threatening condition characterized by thrombotic microangiopathy. The standard treatment for TTP is plasmapheresis. For refractory or relapsing cases, various immunosuppressive agents have been tried, and among them rituximab has shown promising results. TTP is rarer in the pediatric age group and the use of rituximab in children with TTP is limited. Reported herein is the successful treatment of relapsing autoimmune TTP with rituximab in a 12‐year‐old girl.
Diffuse cerebral vasospasm with infarct after intrathecal cytarabine in childhood leukemia
Authors: Yoon Jong Hyung , Yoon Ju Young , Park Hyeon Jin , Son Meong Hi , Kim Su‐Hyun , Kim Woojun , Kim Ho Jin , Lee Sang Hyun , Park Byung‐Kiu
Published: December 2014

Although the varied neurotoxicity of intrathecal (IT) chemotherapy for treatment of childhood acute leukemia is well known, most are related to transient post‐puncture headache, drug‐induced arachnoiditis, or leukoencephalopathy after methotrexate or cytarabine. Cerebral vasospasm leading to acute infarct after IT chemotherapy is very uncommon in children. Reported herein is a rare case of diffuse cerebral vasospasm with subsequent cerebral infarct after IT cytarabine in a 7‐year‐old boy with acute lymphoblastic leukemia, who successfully recovered with supportive management, and a review of the literature.
Cyclic fluctuation of blood pressure in neonatal neuroblastoma
Authors: Fujishiro Jun , Sugiyama Masahiko , Ishimaru Tetsuya , Uotani Chizue , Tsuchida Shinya , Takahashi Naoto , Shiozawa Ryosuke , Takita Junko , Iwanaka Tadashi
Published: December 2014

Herein is described a case of neonatal neuroblastoma with cyclic blood pressure fluctuation and elevated catecholamines. The fluctuations stabilized after treatment with α‐adrenergic blocker and the perioperative course was uneventful. The possibility of catecholamine‐related symptoms including hypertension, heart failure, and blood pressure fluctuations should be considered in the treatment for neuroblastoma; if they are present, treatment with α‐blockers is effective.
Rare but threatening complication of otitis media: Lateral sinus thrombosis
Authors: Kafadar İhsan , Sözen Mukaddes Esra , Büyüktaş Aytaç Didem , Yalçın Koray
Published: December 2014

Although appropriate use of antibiotics has decreased mortality, lateral sinus thrombosis is a rare, important intracranial complication of acute otitis media. Herein is described the case of a 5‐year‐old patient with lateral sinus thrombosis after acute otitis media. We emphasize the need to be alert for lateral sinus thrombosis when treating acute otitis media.
Antenatal ultrasound visualization of left testis that then vanished after birth
Authors: Ito Yasuo , Kitamura Hajime
Published: December 2014

A 10‐month‐old infant was referred for disappearance of the left testis, which had been confirmed as present on antenatal ultrasound at 38 weeks of gestation, as well as at the newborn physical exam and the 4 month exam. The right testis was enlarged, whereas the left testis was palpated as a nubbin. The right testis measured on ultrasound was 1.6 × 0.8 × 1.0 cm; the testicular volume was 0.67 cm3. The left nubbin was hyperechoic, and accurate measurement of testicular components was difficult. At the age of 1 year 8 months, with the diagnosis of left vanishing testis, inguinal exploration was undertaken to rule out intra‐abdominal cryptorchidism. A fibrous nodule that connected to the spermatic vessels and the vas deferens was resected. Histopathology indicated a testicular remnant containing seminiferous tubules, hemosiderin deposits, calcification and marked fibrosis of the stroma, suggesting hemorrhagic infarction in utero.
Rare coincidence of familial central core disease and hemophagocytic lymphohistiocytosis
Authors: Lee Jin Sook , Lim Byung Chan , Kim Ki Joong , Hwang Yong Seung , Seong Moon‐Woo , Park Sung Sup , Park Sung‐Hye , Chae Jong‐Hee
Published: December 2014

Central core disease is a congenital myopathy caused by mutations in RYR1. A 6‐year‐old girl was admitted due to difficulty in running and climbing stairs. Another 13 members through the four generations had similar symptoms, indicating autosomal dominant inheritance. Muscle biopsy showed the characteristic central cores in predominant type 1 fibers. She later developed hemophagocytic lymphohistiocytosis. Mutation analysis identified c.14582G>A in RYR1, and c.1693delG and c.2954 + 5G>A in UNC13D. To our knowledge, this is the first case of a patient with central core disease, carrying a RYR1 mutation in a Korean large family, who had concurrent familial hemophagocytic lymphohistiocytosis.
Wheezing as a sign of cor triatriatum sinister culminating in multiple organ failure
Authors: Lee Meng‐Luen , Chen Ying‐Cheng , Lee Ming‐Sheng , Chien Jien‐Wen
Published: December 2014

Cardiac asthma or cardiac wheezing (CW) refers to a syndrome of dyspnea and wheezing that mimicks asthma clinically. Reported herein is the case of a 2‐month‐old boy who presented with refractory wheezing as a sign of cor triatriatum sinister (CTS) that culminated in overwhelming multiple organ failure in a short time. On the day of admission, oxygen saturation (SpO2) was <80%. Heart rate was 198 beats/min and respiratory rate 58 breaths/min. Chest radiogram showed pulmonary edema. Electrocardiogram showed right atrial enlargement and right ventricular hypertrophy. N‐terminal pro‐brain natriuretic peptide (NTproBNP) was very high at >20 000 pg/mL. Two‐dimensional echocardiography with Doppler showed CTS, which was complicated with severe pulmonary arterial hypertension due to flagrant pulmonary venous obstruction. Cardiac surgery was undertaken, after which pulmonary edema subsided, SpO2 increased to ≥96%, and NTproBNP dropped to normal. He was discharged 11 days later, and was free of cardiac, pulmonary, renal, and neurological sequelae at 24 month follow up.
Obesity hypoventilation syndrome in a 12‐year‐old child requiring therapeutic phlebotomy: Case report and review of the literature
Authors: Branstiter G. Wesley , Lempert Nathaniel L , Sotomayor Talia , Crombet Ofelia , Murray Pamela J , Patra Kamakshya P
Published: December 2014

The childhood obesity epidemic involves unusual and underrecognized complications associated with this clinical and public health problem. Obesity hypoventilation syndrome (OHS) is defined as the triad of obesity, daytime hypoventilation, and sleep‐disordered breathing in the absence of an alternative neuromuscular, mechanical or metabolic explanation for hypoventilation. We herewith report a 12‐year‐old boy who was diagnosed with OHS. The patient improved with phlebotomy and bi‐level positive airway pressure. To the best of our knowledge, this is the first reported case of secondary polycythemia due to OHS requiring therapeutic phlebotomy.
Space-time patterns of soil pH in submountain beech ecosystems in the West Carpathians
Authors: Janík Rastislav , Schieber B. , Bublinec E.
Published: December 2014

The results of pH values monitoring performed for 26 years (1988–2013) in Štiavnické vrchy Mts (middle Slovakia) are summarised. The accumulative trend of acidifying components of forest soils downwards the soil depth has been confirmed. The pH values of soil, exposed to a severe airborne pollution load in the past, were in general lower: from 5.42 in the surface humus decreasing to 4.93 at a soil depth of 0.25 m. On the other hand, the pH values of throughfall and precipitation in open area were comparable. The lower pH values were found in lysimetric water within the forest stand plot at 0.10 m depth (4.50 in 2009). The absolute highest pH were found in the forest throughfall and reached the values of 6.40 in year 1999.The annual dynamics exhibited the highest pH values in the winter and spring. On the other hand, the lowest values were recorded in summer period.
A Simplified Test Station for Alkaline Fuel Cell
Authors: Aremo B. , Adeoye M. O. , Obioh I. B.
Published: December 2014

For most of the last four decades, the alkaline fuel cell (AFC) has been largely overlooked in favor of the polymer electrolyte membrane fuel cell (PEMFC) and the solid oxide fuel cell (SOFC). However, the persistently high costs and complexities of the PEMFC and the SOFC have led to renewed interest in the AFC in recent times. This work reports the designs of custom test fixtures and electronics instrumentation relevant for AFC electrode testing and system optimization. Features implemented in the designs include a real-time voltage measurement unit (VMU), electronic load circuit, and electrolyte heater system. Validation experiments indicated a close agreement between the VMU’s readings, Nernst equation predictions, and readings from a digital voltmeter. The electrolyte heater system’s temperature measurement module was validated with its ability to replicate a cooling profile of ethanol similar to that obtained from a mercury-in-glass thermometer. Materials selection, design considerations, and fabrication steps for other test station components, such as the button-cell test apparatus and the half-cylinder electrolyte heater, were presented. The test station was used for polarization studies of aluminum-air AFC under different conditions of potassium hydroxide (KOH) electrolyte temperature and concentration. The studies revealed optimum values of electrolyte temperature and concentration for the AFC electrode to be 70 °C and 4 M KOH, respectively.
Atomization Characteristics of Camelina-Based Alternative Aviation Fuels Discharging From Dual-Orifice Injector
Authors: Sivakumar D. , Sakthikumar R. , Raghunandan B. N. , Hu John T. C. , Puri S. K. , Jain A. K.
Published: December 2014

The atomization characteristics of blends of bioderived camelina hydrogenated renewable jet (HRJ) alternative fuel with conventional aviation kerosene (Jet A-1) discharging into ambient atmospheric air from a dual-orifice atomizer used in aircraft engines are described. The spray tests are conducted in a spray test facility at six different test flow conditions to compare the atomization of alternative fuels with that of Jet A-1. The fuel sprays are characterized in terms of fuel discharge, spray cone angle, drop size distribution, and spray patternation. The measurements of spray drop size distribution are obtained using laser diffraction based Spraytec equipment. The characteristics of fuel discharge and cone angle of alternative fuel sprays do not show any changes from that of Jet A-1 sprays. The characteristics of spray drop size, evaluated in terms of the variation of mean drop size along the spray axis, for the alternative fuel sprays remain unaffected by the variation in fuel properties between the alternative fuels and Jet A-1. The measurements on spray patternation, obtained using a mechanical patternator at a distance 5.1 cm from the atomizer exit, show an enhanced fuel concentration in the vicinity of spray axis region for the alternative fuel sprays discharging from the dual-orifice atomizer.
Thermodynamic Analysis of Solar Heat Pump Assisted Heating Systems
Authors: Siyahhan Türkgenç Zozan , Çebi Alican , Celen Ali , Dalkılıç Ahmet Selim , Wongwises Somchai
Published: December 2014

In this study, a system has been developed which can be used for heating buildings by utilizing solar energy, which is free and abundant in our country, with the aim of minimizing fossil based fuel consumption especially at wintertime and this system’s efficiency has been analyzed mathematically with numerical methods.

First of all, in this study the performance of a solar heat pump system is examined. The city of Antalya is chosen for this study which is in the southern region of Turkey with an abundant source of solar energy. The usability of solar energy throughout the year is examined and its application areas in building heating with the utilization of heat pumps are determined. In addition an auxiliary system with an alternative energy source is considered in case solar energy is insufficient by itself.

In order to determine all of the above, energy analysis of the system is performed. The advantages of the solar heat pump heating system are studied considering the amount of energy saved and the efficiency of the system. Thermodynamic and thermoeconomic analysis has been carried out in order to determine how effectively the solar energy is utilized by the system and the advantages of solar heat pump.
Research on the Performance of Shaftless Water-Jet Propulsion
Authors: Cao Puyu , Wang Yang , Li Guidong , Qian K. X.
Published: December 2014

This paper presents the results of an investigation on the feasibility and superiority of the shaftless water-jet propulsion. Resulting from the elimination of the upstream driving shaft, the shaftless model is a rim driven propulsion where shaftless water-jet pump and intake duct are the major parts. The computational fluid dynamics (CFD) methodology was used to calculate the performance and visualise the flow of the shaftless water-jet installation, and the numerical model was validated with available experimental data.

As the result of reducing the velocity circulation at the inlet of the rotor, there was nearly 2% increment in the performance prediction of the shaftless water-jet pump than the traditional. Based on the theoretical formula, it infers that the increasing flow rate and head of the shaftless pump would deliver more thrust to the vessel on the design condition (vs=30knot), and the variation of jet velocity ratio would contribute to extending of propulsion efficiency.

Flow field analysis has proved that the removal shaft could minimise the velocity non-uniformity and eliminate the flow separation around the shaft, so there would be less energy losses in the intake duct. With the improvement of intake duct, it also reduces the backflow and blocking at the shroud. Furthermore it produces a more uniform inflow for the rotor to ensure better efficiency and reliability of the propulsion.

Performance analysis shows that the shaftless model delivers more thrust (3%) than the traditional on the design speed. In order to match the resistance, the shaftless water-jet propulsion has to decrease the rotation speed of the engine to compensate for the increment of thrust, it means that the shaftless model could possess more efficiency (4%) and save more energy for operating. On the off-design condition, the shaftless model is proved to extend the working range and broaden the high efficiency region resulting from the increment of output volume.
A Continuum Approach to Permeation With Interfacial Leakage: A Space Seal Approach
Authors: Garafolo Nicholas G. , Wischt Rachel J.
Published: December 2014

Prior analyses in elastomer space-seals thrived on the assumption that mass flow over/through a seal was due to permeation. In fact, the state-of-the-art space-seal leakage prediction method relies on this assumption. Well-documented efforts have shown that the aforementioned prediction method is versatile in its ability to predict leak rates in nominal operational conditions. Its merits, however, fall short in the application of low seal contact loading and in applications with substantial space environmental exposure (e.g., ultraviolet radiation, atomic oxygen). In response to this shortfall, a unique method and analysis was recently developed to parse total leakage into interfacial leakage and permeation, with the intent of capturing the effects of surficial degradation; results highlighted that while permeation dominated interfacial leakage for high contact seal loading, the interfacial component was not negligible. Furthermore, the interfacial component was shown to dominate permeation for low contact pressure, as would be the case with a faulty docking mechanism. Presented herein is a novel continuum approach to seal leakage that retains the compressible permeation approach previously developed and enhances the overall fidelity by incorporating interfacial leakage with entrainment terms which describe the movement of mass orthogonal to the seal-counter face boundary (i.e., mass transfer from the elastomer to the interfacial zone). Integral to the proposed model, the interfacial leakage component is a function of seal contact pressure, pressure gradient, and, ultimately, space environmental exposure. Also presented is an application of the model to a candidate, elastomer space seal. Results showed an improved prediction and provide a measure of verification and validation to the proposed seal leakage model.
CFD Simulation of the Flow Characteristics of NACA 0012, NACA 6409, and DHMTU Airfoils in Ground Effect
Authors: Sharma Saurabh , Clement Shibu
Published: December 2014

Ground effect is a phenomenon caused by the presence of a fixed boundary layer below a wing. This results in an effective increase in lift to drag ratio of the airfoil. The available literature on this phenomenon is very limited; also the types of airfoils used in traditional aircrafts are not suited for ground effect vehicles, so a computational study has been done comparing traditional airfoils (NACA series) with ground effect airfoil (DHMTU).

In this paper, the aerodynamic characteristics of a NACA 6409, NACA 0012, DHMTU 12-35.3-10.2-80.12.2[1] section in ground effect were numerically studied and compared. In 2D simulation, the flow around each of the airfoils has been investigated for different turbulence models viz. Spalart Allmaras turbulence model and k-ε Realizable turbulence models. Lift coefficient, drag coefficient, pitching moment coefficient and lift to drag ratio of each airfoil was determined on several angles of attack from 0 to 10° (0°, 2°, 4°, 6°, 8°, 10°) and different ground clearances (h/c=0.2, 0.4, 0.6, 0.8, 1.0). The results of the CFD simulation indicate a reduction in drag coefficient and an increase in lift coefficient, thus an overall increment in lift to drag ratio of the airfoils, when flying in proximity to the ground. Also DHMTU airfoils have shown a greater consistency in Cm behavior with decreasing height-to-chord (h/c) ratio.
Experimental Characterization of the Separate Flow Induced by a Wall-Mounted Bump
Authors: Fadla Fawzi , Keirsbulck Laurent , Aloui Fethi , Laval J-P.
Published: December 2014

The dynamical behavior of the flow separation induced by a wall-mounted two-dimensional bump is studied. The present investigation is based on an experimental approach that aims to provide further insight into the separate flow dynamic in such configuration. The main interest is devoted to the separation Reynolds number dependency. A general feature of separated flows dynamics is also addressed by statistical and structural information derived from the present experimental approach. Results are presented for turbulent water inflow for a moderate Reynolds-number range from 165 to 605 based on friction velocity and channel half-height (so-called Kármań number). The ratio of the bump height h and the channel full height H is 0.335. The unsteady separation process and the associate instability mechanism are very sensitive to small perturbations. So, in order to preserve the flow physics, all of the experimental techniques employed in the present study are non-intrusive. An examination of the high resolved velocity fields showed that for a moderate Kármań number, a separate area exists. Under this condition, a thin region of reverse flow was formed above the bump and a large-scale vortical activity, characterized by low-frequencies, are clearly observed. The reported results do not only yield the expected turbulent separation bubble dependencies. They also show that the well known coexisting instabilities process, which find their origin in laminar flow regime, persist for higher Kármań numbers.
Experimental and Numerical Investigation of a Domestic Refrigerator
Authors: Zhang Chaolei , Lian Yongsheng , Kempiak Michael , Hitzelberger Erik , Crane Scott
Published: December 2014

An integrated experimental and numerical investigation was carried out to gain insight into the heat transfer phenomena and flow characteristics inside a domestic refrigerator. A refrigerator model was constructed using insulation foam sheets according to the inner dimensions of a household refrigerator. A reversal heat leak analysis was conducted on the constructed model in a temperature-controlled chamber, where the chamber temperature was lower than the inner temperature of the refrigerator. A temperature-controlled heater was mounted where the evaporator was. The heater was enclosed in a heater box to heat the air and to maintain a high temperature in the refrigerator. A variable speed fan was used to force air circulation. Thermocouples were used to measure the temperature at specified positions and to measure the average temperature difference across the refrigerator side walls. The correlation between the status of the heater and the control temperature variation pattern was analyzed. Heat loss rate was calculated using the data from the thermocouples too. The calculated heat loss rate closely matched the generated heat by the heater and the fan. Moreover, according to the results with different input voltages, the variation trend of the heat flux density was analyzed. A conjugate heat transfer analysis was conducted based on the constructed model using Fluent. The heater was modeled as a heat volume source and the fan was modeled using a pressure jump condition based on the experiment result. Comparisons were made between the experimental and numerical results. The predicted heat loss rate and the heat flux density through the walls matched very well with the experimental results. And the variation trend of the heat flux density with different input voltages also showed the same trend as the experimental result. And the airflow pattern and the temperature distribution were also analyzed in detail.
Comparison of Sharp Interface and Smoothed Profile Methods for Laminar Flow Analysis Over Stationary and Moving Boundaries
Authors: Mohaghegh Fazlolah , Mousel John , Udaykumar H. S.
Published: December 2014

This study is a comparison of two techniques for simulation of particulate flows on fixed Cartesian grids: Sharp interface Method (SIM) (Udaykumar et al., 2001, 2002, 2003) and a modified version of Immersed Boundary Method (Peskin, 1977) (IBM) known as Smoothed Profile Method (SPM) (Nakayama and Yamamoto, 2005; Luo et. al, 2009). Different cases were studied includes flow over one or two moving and stationary particles. Predictions of the drag coefficient shows that SPM and SIM are very close to the experiments. SIM slightly under-predicts the value of the drag coefficient while SPM has a small over-estimation. Moreover, SPM is more accurate on coarse grids. However, with refinement of the grid SIM approaches the exact values very fast leading to better results on fine grids. Flow pattern and vortex structures of SPM and SIM are almost the same. Both methods are capable of analyzing the wake flow. Unlike SIM, SPM is able to simulate the flow when two particles are in contact. When two particles are in motion and are very close in a way that the two interfaces overlap, SPM shows a repulsion force between two spheres which reduces the accuracy in comparison with SIM. However, SPM can achieve the collision of two particles without problem.
Model Reduction and Analysis of NS-DBD Based Control of Stalled NACA0015 Airfoil
Authors: Mohan Arvind T. , Gaitonde Datta V.
Published: December 2014

Recent years have seen increased emphasis on mathematical model reduction using modal decomposition techniques of high dimensional flow field data from experiments as well as numerical simulations. These tools decode the complex unsteady flow-field into several modes. Different tools highlight different flow dynamics. In the experimental community, Proper Orthogonal Decomposition (POD) has been the most commonly used technique, ranking modes by their relative energy content, without concern for temporal aspects. However, many dynamics are not highlighted by the most energetic structures. In transitional flows for example, structure growth is a more a more important indicator of the turbulent effects. The Dynamic Mode Decomposition (DMD) technique highlighted by Schmid [1] achieves this by ranking modes by the most dynamically varying flow features. In this work, we use DMD and POD to analyze flow past a NACA0015 airfoil at Reynolds number of 100,000 and AoA=15 degree, without and with control. The specific control technique employed is based on the Nano-second Pulsed Dielectric Barrier Discharge (NS-DBD) actuator. Experimentally validated high fidelity 3-D numerical simulations are employed to generate the required snapshots. From the DMD modes, the dominant time-varying flow structures associated with the two cases are identified, and their stability characteristics are compared. DMD and POD modes are compared to each other. The DMD modes highlight the dynamically varying nature of the flow-field. A Floquet stability analysis of the eigenvalues from DMD for both the no-control and control cases is presented. Further, the original flow field is reconstructed from the DMD modes and their individual modal behavior has been analyzed to show the effect of control authority on the flow.
Effect of Tip Clearance on Suction Performance at Different Flow Rates in a Mixed Flow Pump
Authors: Jung Yo Han , Min Young Uk , Kim Jin Young
Published: December 2014

This paper presents a numerical investigation of the effect of tip clearance on the suction performance and flow characteristics at different flow rates in a vertical mixed-flow pump. Numerical analyses were carried out by solving three-dimensional Reynolds-averaged Navier-Stokes equations. Steady computations were performed for three different tip clearances under noncavitating and cavitating conditions at design and off-design conditions. The pump performance test was performed for the mixed-flow pump and numerical results were validated by comparing the experimental data for a system characterized by the original tip clearance. It was shown that for large tip clearance, the head breakdown occurred earlier at the design and high flow rates. However, the head breakdown was quite delayed at low flow rate. This resulted from the cavitation structure caused by the tip leakage flow at different flow rates.
Flow Behaviour Around Square and Circular Obstacles in 2D and 3D Configurations Using Lattice Boltzmann Method
Authors: Abassi Wafik , Aloui Fethi , Ben Nasrallah Sassi , Keirsbulck Laurent , Legrand Jack
Published: December 2014

The investigation of wakes of bluff bodies in a channel is still relevant despite the large number of works devoted on it, in both experimental and numerical studies. This attractiveness is mainly due to its related applications and practical interest in varied engineering fields.

The understanding of dynamic flow behavior and the topology of the instability structures occurring in the wake is essential in order to optimize the obstacle shape according to the desired objectives.

A confined laminar flow around a square and a circle, placed in a channel is numerically investigated in this work using Lattice Boltzmann method. The study is then extended to 3D computations with horizontal cylinder within a square then a circular cross-section mounted inside a rectangular duct.

The Reynolds number (Re), based on the maximum velocity and the cross-section height varies between 50 and 120 and the blockage ratio is r=1/3. This geometry is representative of a passive method to enhance mixing in the laminar channel flow. LBM was built up on the D2Q9 and D3Q19 model for respectively 2D and 3D computations. The single relaxation time approach called the lattice-BGK method was adopted.

The topology of the vortex-shedding phenomena and wake behavior according the Reynolds numbers, for both geometries of the obstacle are focused. The effect of wall confinement on the flow transition to the vortex shedding regime is discussed. Velocity profiles and integral parameters such as recirculation length and Strouhal number were investigated.

The numerical results are supported by literatures works results for the same configuration showing the performance of LBM as numerical tools simulation for such kind of flows.
CFD Study the Influence of Solid Phase on the Pump Performance
Authors: Strongin Mikhail P.
Published: December 2014

In the water transportation applications of the liquid-solid mixture pumping is very common. Among these applications the submersible well pumps, dewatering, drainage, and irrigation could be mentioned. In this work, CFD study of influence of amount of solid phase in the solid-liquid mixture on the pump parameters is presented. Two stages vertical mixed flow pump was modeled. Fluent 14.5.7 commercial code was used for simulations. Mixer multiphase model can be used to model multiphase flows where the phases move at different velocities, but assume local equilibrium over short spatial length scales. Therefore, it was chosen for mixture model. SST k-ω model for turbulence was selected. Multi-reference frame approach was used for rotation domains. All mixtures in the presented work have water as their primary phase; the secondary phase is assumed to be a continuum of solid spherical particles of silicon with diameters that range from 0.1 mm to 0.4 mm. The load of the solid particles ranges from 0.5% to 10% of volume fraction of the mixture on the pump inlet. The total number of the mesh cells was 9 million.

Calculations of the pump head for mixture and for pure water were done using the same water flow rate.

Comparison of the results shows that they are close within ∼1% difference. It needs to be emphasized that the pump head is determined by the liquid phase. On the other hand, the efficiency of the pump with high solid phase load was much lower in comparison with the same flow rate of water for pure water case. These results may help in designing pumps for transporting liquid-solid mixture.
Incorporating Light and Algal Effects Into CFD for Photobioreactor Design
Authors: Hochhalter Matthew , Gent Stephen P.
Published: December 2014

The objective of this research is to develop models that represent the effects of light and algae and incorporate these effects within a computational fluid dynamics (CFD) model of a photobioreactor (PBR). Several factors, including nutrient availability, carbon dioxide concentration, light intensity, and frequency of high and low light intensity periods, affect the efficiency of biomass yield within a photobioreactor. However, even with a general understanding of the affecting factors, scaling up of photobioreactors from a laboratory to a commercial level exist and provide a challenge concerning efficiency. The development and execution of an integrated light, algae, and CFD model can provide insight into more cost and time efficient configurations of PBRs. In depth CFD studies have been used to predict thermal-fluid effects, including bubble-liquid interaction and temperature profiles; however, studies concerning algae-liquid interactions appear sparsely. In order to better understand up-scaling issues, new modifications of previous CFD methods incorporate an algae particle tracking method, as well as light modeling. The particle tracking method considers the individual algae cell as a volume-less and mass-less particle that follows the liquid velocity profiles within the PBR. The light model takes into account algal concentration as well as bubble location and bubble concentration. The integration of the models allows for the average intensity of light experienced by an algae cell to be numerically estimated, alongside the frequency of light and dark periods the particle experiences. The long term goal of this research is to develop an algae growth model that incorporates light intensity and the flashing light effect. The present research is a continuum of previous work aimed at pursuing the optimum design of a column PBR which is commercially viable and effective at producing algal biofuels and bioproducts.
Experimental Study of Scale Effects on the Scaling Law for Tip Vortex Cavitation Noise
Authors: Park Jisoo , Park Cheolsoo , Choo Youngmin , Seong Woojae
Published: December 2014

Novel scaling law for the tip vortex cavitation (TVC) noise is derived from the physical basis of TVC, employing the Rankine vortex model, the Rayleigh-Plesset equation, the lifting surface theory, and the number of bubbles generated per unit time (N0). All terms appearing in the scaling law have physical or mathematical grounds except for N0. Therefore, to experimentally validate the N0 term, experiments are designed to keep the same TVC patterns as velocities and dimensions vary. Optimal shooting conditions with a velocity and size variation are determined from the scaling exponents, cavitation numbers and Reynolds numbers at each condition. To avoid wall effects and flow field interaction, two hydrofoils are optimally arranged by using computational fluid dynamics (CFD) for size variation. Images taken by a high speed camera are used to count N0, considering similitude of the spectra of nuclei. Scaling exponents curve fitted from five velocities and cavitation inception numbers have an exponent value of 0.371, which is closely placed on scaling exponents curve deduced from Schlichting’s friction coefficients fitting with Reynolds number. The tendency that N0 is proportional to a velocity and inversely proportional to a size can be confirmed by this study.
Compartment Method for Dynamic Multi-Scale Simulation of Precipitation Reactors
Authors: Metzger Lukas , Kind Matthias
Published: December 2014

Precipitation crystallization is one possibility to produce nano-scaled solid particles from the liquid phase. High nucleation and growth rates are generated by mixing two well soluble reactants and their subsequent reaction to a sparingly soluble product. These primary processes can be very fast. Therefore experimental access to internal parameters is given insufficiently due to predominantly very short process times. Computational Fluid Dynamics (CFD) based methods are a promising tool to gain insight into those inaccessible processes. Unfortunately, 3D modeling of complex precipitation reactors poses enormous difficulties and computational costs to CFD especially in the production scale under the aspect of macroscopic flowfields down to microscale modeling of mixing, rheology and particle formation. Therefore, a new methodic approach is presented that is able to handle these complex interactions. Due to local and temporal multiscale complexity, it is not advisable to model the complete apparatus. One basic principle of the methodical consideration is the arrangement of cross-linked compartments to reduce the huge unsimulatable control volume in its complexity and dimensions. Thereby, population balance equations (PBE) are solved, using CFD measured, average state variables, with a discrete one-dimensional High Resolution Finite Volume (HRFV) algorithm. Nevertheless appropriate fundamental kinetics for primary and secondary processes have to be implemented. Besides the new methodic approach, this paper deals with the influence of temporal supersaturation buildup on the product particle distribution. It is shown that important conclusions about the mixing behavior of Confined Impinging Jet mixers (CIJMs) can be drawn by coupling CFD and external population balancing even without any micromixing model. The contribution provides an insight into the methodic approach and first derived results.
Internal Stresses and Breakup of Porous Aggregates in Homogeneous Isotropic Turbulence
Authors: Vanni Marco
Published: December 2014

The stresses acting on aggregates smaller than the Kolmogorov length scale in homogeneous isotropic turbulence were estimated by a two-scale numerical simulation. The fluid dynamics at the scales larger than the Kolmogorov length scale was calculated by a Direct Numerical Simulation of the turbulent flow, in which the aggregates were modeled as point particles. Then, we adopted Stokesian Dynamics to evaluate the phenomena governed by the smooth velocity field of the smallest scales. At this level the disordered structure of the aggregates was modeled in detail, in order to take into account the role that the primary particles have in generating and transferring the internal stress. From this result, it was possible to evaluate the internal forces acting at intermonomer contacts and determine the occurrence of breakup as a consequence of the failure of intermonomer bonds. The method was applied to disordered aggregates with isostatic and highly hyperstatic structures, respectively.
The Transient Evolution of Bubbles in Turbulent Channel Flows
Authors: Tryggvason Gretar , Lu Jiacai
Published: December 2014

Direct numerical simulations of multiphase flows, where every spatial and temporal scale are fully resolved, provide data that allows not only unprecedented insight into the dynamics of the flow but should also aid in the development and testing of models for the unresolved scales in two-fluid and large eddy simulations. DNS of bubbly flows in vertical channels have showed that the structure of such flows is relatively simple but also relatively insensitive to some of the closure terms in equations governing the average flow. Furthermore, most of those simulations have been done for modest Reynolds numbers and uniform bubble size. Here we describe results from a simulation of the transient motion of a larger and more complex system and discuss how the results may help in developing models for the average flow.