bluuebunny/crossref_metadata_2025 huggingface dataset:
Everolimus‐associated perianal ulcers in an eight‐month‐old heart transplant recipient
Authors: Spehl Marco S. , Fleck Thilo , Schauer Franziska , Meiss Frank , Stiller Brigitte
Published: October 2017

mTOR inhibitors have a wide spectrum of therapeutic applications in adults and children. Little is known, however, about serious adverse effects in children undergoing mTOR inhibitor therapy. Oral ulcers are common and sometimes severe, but no other gastrointestinal involvement has been reported so far. Here we present a case of everolimus‐associated perianal ulcers in an eight‐month‐old infant, 3 months after heart transplantation, which necessitated the drug's discontinuation. In a thorough series of diagnostic tests, we identified no other cause for the progressive perianal ulceration. The recognition and appropriate management of mTOR inhibitors' adverse effects in pediatric patients are essential and remain challenging.
Repeated ultraviolet irradiation induces the expression of Toll‐like receptor 4, IL‐6, and IL‐10 in neonatal human melanocytes
Authors: Song Hee Jin , Lee Si Hyub , Choi Gwang Seong , Shin Jeonghyun
Published: October 2017

Background

Human melanocytes express Toll‐like receptor 4 (TLR4), which regulates ultraviolet (UV)‐induced cutaneous immunosuppression in Langerhans cells. Lipopolysaccharide (LPS) stimulation increases melanocyte pigmentation and TLR4 expression, while inducing local innate inflammatory responses.

Aims

We investigated whether UV radiation induces TLR4 expression in neonatal human melanocytes (NHMs) and how this affects the immune system.

Methods

We cultured NHMs with LPS treatment or with one‐time or repeated UVA or UVB exposure, and investigated and compared the effects on TLR4 expression, melanin contents, and cytokine production.

Results

NHMs in the resting state did not express TLR4. LPS stimulation induced TLR4 expression and increased pigmentation. TLR4 expression was not detected after single‐dose UVA or UVB treatment, but pigmentation increased. Repeated UV treatment induced TLR4 expression and increased pigmentation. LPS stimulation and repeated UV treatment increased IL‐6 secretion, and repeated UVB treatment increased IL‐10 secretion.

Conclusion

These results suggest that human melanocytes may actively participate in UV‐induced immune modulation.
The intestinal nematode inhibits T‐cell reactivity by targeting P‐GP activity
Authors: Donskow‐Łysoniewska K. , Krawczak K. , Kozłowska E. , Doligalska M.
Published: October 2017

Host immunosuppression occurs during chronic nematode infection, partly due to effector T‐cell hyporesponsiveness. The role of P‐glycoprotein (P‐gp), a member of the ABC transporter family, has been assessed in T‐cell activity. This study assesses the possible role of P‐gp in T‐cell activity during nematode infection. Our findings indicate that blockade of P‐gp in vivo increased protection against Heligmosomoides polygyrus nematode infection and was associated with the enhanced T‐cell activity. Three P‐gp‐inhibitors, verapamil (VRP), cyclosporine (CsA) and tariquidar (XR9576), were used to determine the influence of nematode infection on the P‐gp function of T cells. The influence of the nematode on the uptake, efflux and kinetics of extrusion in T‐cell subsets CD4+ and CD8+ was assessed by the accumulation of Rho123 dye. The results indicate that H. polygyrus infection contributes to the inhibition of T‐cell function by elevating P‐gp activity. The blockade of P‐gp in the T cells of infected mice led to an impressive increase in T‐cell proliferation and IL‐4 cytokine release through the upregulation of NF‐κB activation. These results provide the first evidence that the P‐gp function of T cells is altered during nematode infection to open the way for further studies aiming to explore the role of P‐gp in host‐parasite interactions.
Unexpandable lung from pleural disease
Authors: Huggins John T. , Maldonado Fabien , Chopra Amit , Rahman Najib , Light Richard
Published: October 2017

Unexpandable lung is a common complication of malignant pleural effusions and inflammatory pleural diseases, such as pleural infection (e.g. empyema and complicated parapneumonic effusion) and noninfectious fibrinous pleuritis. Unexpandable lung due to pleural disease may be because of an active pleural process, and is referred to as malignant or inflammatory lung entrapment.

An unexpandable lung may also be encountered in the setting of remote pleural inflammation resulting in a mature fibrous membrane overlying the visceral pleura preventing full expansion of the lung. This condition is termed trapped lung and may be understood as a form of defective healing of the pleural space. Trapped lung typically presents as a chronic, stable pleural effusion without evidence of active pleural disease. An unexpandable lung most often manifests itself as an inability of fully expanding the lung with pleural space drainage. Patients will either develop chest pain preventing complete drainage of the pleural space or develop a post‐procedure pneumothorax.

Pleural manometry and radiological imaging are useful in the assessment of an unexpandable lung. Pleural manometry can demonstrate abnormal lung expansion during drainage and imaging will demonstrate abnormal visceral pleural thickening found in trapped lung or malignant and inflammatory lung entrapment.
Magnesium supplementation: A consideration in dialysis patients
Authors: Apetrii Mugurel , Covic Adrian , Massy Ziad A.
Published: October 2017

Even though disorders of magnesium (Mg) balance are common in dialyzed patients, this cation is often neglected. Many factors interfere with serum magnesium including diet, medications (eg, antacids or phosphate binders), and the dialysis prescription. Mg supplementation may help reduce serum phosphate concentration, PTH, and interfere with vascular calcification and bone mineralization. It could also decrease the all‐cause and cardiovascular mortalities, although the results of current studies are conflicting. As with many other variables that influence hard endpoints in nephrology, additional research directly targeting the role of Mg supplementation in dialyzed patients are required. Nevertheless, a current risk/benefit assessment suggests that supplementation of Mg targeting high normal serum levels may represent a plausible option to improve the outcome of dialysis patients.
Phenotypic Prenatal Diagnosis of Chronic Granulomatous Disease: A Useful Tool in The Absence Of Molecular Diagnosis
Authors: Kulkarni M. , Gupta M. , Madkaikar M.
Published: October 2017

Chronic granulomatous disease (CGD) is an inherited immunodeficiency disorder affecting the microbicidal function of the phagocytes. It is characterized by susceptibility to recurrent infections leading to significant morbidity and mortality. Antibacterial and antifungal prophylaxis, though, has significantly reduced the rate and severity of the infections; the breakthrough infections still remain a challenge. Currently, allogenic haematopoietic stem cell transplantation is the only curative option which is very expensive and unavailable for many due to lack of suitable donor. Thus, prenatal diagnosis (PND) forms an important component of management in the affected families. PND is challenging in families approaching late in pregnancy with an uncharacterized molecular defect. In such cases, PND can be performed by analysis of NADPH activity of fetal blood (FB) neutrophils at 18–20 weeks of gestation. Cord blood samples at 18 weeks of gestation from healthy control were used to establish normal ranges for NBT and DHR. PND was offered for six pregnancies (NBT: n = 3, DHR: n = 6) with index cases of CGD confirmed by abnormal NBT and DHR analysis. NBT and DHR tests were found to be negative for all the six cases, confirming the same on samples post‐delivery. NBT and DHR tests offer a rapid and sensitive PND of CGD in the absence of facilities for molecular diagnosis. It was observed that addition of CD15 along with CD45 led to an accurate DHR analysis. It is recommended to perform the diagnosis with adequate precautions only at centres with considerable experience and expertise in the diagnosis of CGD.
Prospective evaluation of outcome of dogs with intrahepatic portosystemic shunts treated via percutaneous transvenous coil embolization
Authors: Culp William T. N. , Zwingenberger Allison L. , Giuffrida Michelle A. , Wisner Erik R. , Hunt Geraldine B. , Steffey Michele A. , Mayhew Philipp D. , Marks Stanley L.
Published: October 2017

Objective

To report outcome and complications after percutaneous transvenous coil embolization (PTCE) and evaluate the clinical, laboratory, and imaging changes in dogs with intrahepatic portosystemic shunts (IHPSS) pre‐PTCE and post‐PTCE.

Study design

Prospective clinical trial.

Animals

Twenty‐five dogs (15 dogs in imaging subgroup) with IHPSS.

Methods

Clinical signs, hematologic, and biochemical parameters were recorded before and 3 months after PTCE. All dogs received the same medical treatment and underwent PTCE. In the imaging subgroup, ultrasonography, hepatic portal scintigraphy, and computed tomography‐angiography were performed pre‐PTCE and post‐PTCE.

Results

All evaluated bloodwork values improved by at least 50% of their initial value, by 3 months post‐PTCE. Liver volume increased after PTCE (P = .001), but remained lower than normal in 11/15 dogs. Hepatic arterial fraction decreased after PTCE (P = .029), consistent with increased portal blood flow to the liver. Twenty‐four of 25 dogs were available for reevaluation at 3 months, and all abnormal clinical signs had resolved in 22/24 dogs.

Conclusion

PTCE appears promising as a treatment for IHPSS, as clinical signs resolved in most cases, bloodwork abnormalities often normalized, and the procedure was performed safely with minimal complications. PTCE increased hepatic portal perfusion and liver volume in most dogs. These promising results justify a future randomized clinical trial comparing PTCE, other attenuation options, and medical management alone.
Effect of superabsorbent polymer on soil and plants on steep surfaces
Authors: Khodadadi Dehkordi Davoud
Published: October 2017

In this study, a superabsorbent polymer (SAP; Super‐AB‐A‐200) was used for the amendment of the water‐holding capacity of soil on a steep surface. Three concentrations of SAP [0.20, 0.40 and 0.60% (w w−1)] and a control (0%) were blended with sandy soil. This study aimed to evaluate the evaporation rate, water retention capacity and saturated water content of polymer‐treated soils for determining plant survival and seed germination rate through cylinder and steep surface experiments. The results demonstrated that sandy soil treated with SAP showed significantly enhanced soil water holding compared with the controls. Furthermore, the seed germination rate was significantly higher in polymer‐treated soils than in the controls. The survival times of grass and ligneous plants were lengthened under water stress conditions. Finally, treatment with 0.40% SAP was the optimum selection for sandy soil amendment on steep surfaces.
Sorption and desorption behaviours of 2,4‐D and glyphosate in calcareous soil from Antalya, Turkey
Authors: Ozbay Bilge , Akyol Nihat Hakan , Akyol Gokce , Ozbay Ismail
Published: October 2017

2,4‐Dichlorophenoxyl acetic acid (2,4‐D) and glyphosate are used extensively as a herbicide in vicinity of Antalya, Turkey. Laboratory batch experiments were conducted to investigate the sorption isotherm and sorption‐desorption characteristics of 2,4‐D and glyphosate. Results indicated that degree of sorption of glyphosate was approximately 50 times higher than 2,4‐D (Kd= 34.43 vs. 0.66 L/Kg). The sorption of 2,4‐D and glyphosate was described by linear and rate‐limited processes for soil. Organic carbon content was most likely responsible for sorption behaviour of 2,4‐D and glyphosate. The rapid desorption can be attributed to soft carbon fraction (humic/fluvic acid and lipids) whereas slower desorption can be responsible by hard carbon fraction (black carbon, kerogen) of soils that led to chemically nonideal behaviour (hysteresis). Sorption of 2,4‐D was low due to most likely deactivation of organic carbon surfaces by excess carbonate fraction, whereas strong binding of glyphosate onto organic carbon causing high sorption behaviour.
Chloroplast DNA markers for Echinochloa taxa
Authors: Zhang J‐P , Fu F , Liu C , Lin Z‐X , Wang Y‐Y , Ye C‐Y , Lu Y‐L
Published: October 2017

The genus Echinochloa (Poaceae) includes numerous problematic weeds over a wide range of ecoregions in the world. To date, molecular markers for species identification and assessing phylogenetic relationship are still limited in the genus Echinochloa. In this study, we developed seven chloroplast molecular markers based on divergent chloroplast regions of E. crus‐galli and E. oryzicola. Furthermore, Marker #1 (psbA) was examined in more than 200 Echinochloa accessions and a phylogenetic tree grouped these Echinochloa accessions into four clades. Additionally, two different E. crus‐galli varieties (E. crus‐galli var. crus‐galli, E. crus‐galli var. praticola) and E. colona were successfully distinguished by this marker. The developed molecular markers contribute to better identification of Echinochloa taxa.
Ivermectin and its target molecules: shared and unique modulation mechanisms of ion channels and receptors by ivermectin
Authors: Chen I‐Shan , Kubo Yoshihiro
Published: October 2017

Ivermectin (IVM) is an antiparasitic drug that is used worldwide and rescues hundreds of millions of people from onchocerciasis and lymphatic filariasis. It was discovered by Satoshi Ōmura and William C. Campbell, to whom the 2015 Nobel Prize in Physiology or Medicine was awarded. It kills parasites by activating glutamate‐gated Cl− channels, and it also targets several ligand‐gated ion channels and receptors, including Cys‐loop receptors, P2X4 receptors and fernesoid X receptors. Recently, we found that IVM also activates a novel target, the G‐protein‐gated inwardly rectifying K+ channel, and also identified the structural determinant for the activation. In this review, we aim to provide an update and summary of recent progress in the identification of IVM targets, as well as their modulation mechanisms, through molecular structures, chimeras and site‐directed mutagenesis, and molecular docking and modelling studies.

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Study on Vortex Structures and Intermittency in Two-Oscillating Grid Turbulence With Viscoelastic Fluids Based on Wavelet Analysis
Authors: Wang Yue , Li Yongyao , Cai Weihua , Wang Lu , Li Fengchen , Yao Liming
Published: October 2017

In this paper, two-oscillating grid turbulence with/without viscoelastic additives was performed experimentally by particle image velocimetry. Two classical drag-reducing additives-polymer (Polyacrylamide, PAM) and cationic surfactant (cetyltrimethyl ammonium chloride, CTAC) were chosen. The experiments were carried out under the classical concentration (25ppm) and three different grid oscillation frequencies. Two-dimensional wavelet transform was utilized to investigate multi-scale characteristics of vortex structures and intermittency based on wavelet coefficient. The results showed that at the same decomposition level, the existence of viscoelastic additives attenuates the high-frequency components of fluctuation velocity. The small-scale intermittency is remarkably inhibited by viscoelastic additives especially for scale parameter smaller than 24. Besides, CTAC additives show different effect from PAM additives. Therefore, turbulent drag reduction with additives also happens in two-oscillating grid turbulence without wall effect.
Comparison Between NACA 65 Profile and Circular Arc Blade Based on Numerical Investigation
Authors: Bian Tao , Han Qianpeng , Böhle Martin
Published: October 2017

For the axial flow fans NACA profiles have been well explored. However, the development and production of NACA profiles are also very expensive. Due to their lower cost of production circular arc blades are also applied to axial flow fans. But there is few information in the open literature focusing on flow loss and behavior of circular arc blades. Therefore, one question remains: how much is the difference of flow loss and behavior between NACA profiles and circular arc blades. In this paper NACA 65 profile and circular arc blade are examined by numerical method. The paper shows the flow loss of both blades in dependence of incidence, Reynolds number and spacing ratio. The occurrence of flow behavior, such as separation bubbles on the leading edge and flow structure on the sidewall is examined and discussed. The flow structure is given on basis of numerical flow picture. Additionally, the flow loss in the sidewall region of both investigated blades are worked out and compared.
Cleaning Sequence Counters Clogging: A Quantitative Assessment Under Real Operation Conditions of a Wastewater Pump
Authors: Gerlach Stefan , Thamsen Paul Uwe
Published: October 2017

Wastewater pumps show a high tendency to failures due to clogging by textiles and fibrous material as constituents of wastewater. High costs for manual cleaning and operational safety concerns create a high pressure for action for operators of wastewater pumping systems. An adaption of the existing wastewater system using different pumping technologies, retrofitting screening facilities, macerators or grinders is very costly with indistinct success. The implementation of operational approaches, i.e. counter measures embedded in the control system, are therefore preferable for all operators. In Berlin a so-called Cleaning Sequence was tested in a field test in close cooperation with the local operator Berliner Wasserbetriebe. For the implementation a large wastewater pumping station was selected where the large wastewater pumps show a high number of clogging events while being crucial for operational safety during peak-load. For a 3 month testing campaign 53 clogging events were countered using the Cleaning Sequence. For 89 percent of the cases the cleaning effect was sufficient and no further manual removal of clogging material was necessary.
Gas-Induced Motion of an Object in a Liquid-Filled Housing During Vibration: Part II — Experiments
Authors: O’Hern Timothy J. , Torczynski John R. , Clausen Jonathan R. , Koehler Timothy P.
Published: October 2017

We develop an idealized experimental system for studying how a small amount of gas can cause large net (rectified) motion of an object in a vibrated liquid-filled housing when the drag on the object depends strongly on its position. Its components include a cylindrical housing, a cylindrical piston fitting closely within this housing, a spring suspension that supports the piston, a post penetrating partway through a hole through the piston (which produces the position-dependent drag), and compressible bellows at both ends of the housing (which are well characterized surrogates for gas regions). In this system, liquid can flow from the bottom to the top of the piston and vice versa through the thin annular gaps between the hole and the post (the inner gap) and between the housing and the piston (the outer gap). When the bellows are absent, the piston motion is highly damped because small piston velocities produce large liquid velocities and large pressure drops in the Poiseuille flows within these narrow gaps. However, when the bellows are present, the piston, the liquid, and the bellows execute a collective motion called the Couette mode in which almost no liquid is forced through the gaps. Since its damping is low, the Couette mode has a strong resonance. Near this frequency, the piston motion becomes large, and the nonlinearity associated with the position-dependent drag of the inner gap produces a net (rectified) force on the piston that can cause it to move downward against its spring suspension. Experiments are performed using two variants of this system. In the single-spring setup, the piston is pushed up against a stop by its lower supporting spring. In the two-spring setup, the piston is suspended between upper and lower springs. The equilibrium piston position is measured as a function of the vibration frequency and acceleration, and these results are compared to corresponding analytical results (Torczynski et al., 2017). A quantitative understanding of the nonlinear behavior of this system may enable the development of novel tunable dampers for sensing vibrations of specified amplitudes and frequencies.
Influence of an Adaptive Blade System on Unsteady Flow Conditions in a 2D Compressor Cascade
Authors: Peter Julija , Tilcher David Konstantin , Meyer Robert , Thamsen Paul Uwe
Published: October 2017

The flow field inside a compressor is characterized by highly unsteady flow effects. Consequently, the performance of a compressor is significantly influenced by the complex flow field. Especially at off-design conditions, flow separation and tip clearance flow cause vortex structures and thus increased losses. The objective of this paper is to give an insight into the effect mechanism of the movable stator vanes as an adaptive system to affect unsteady flow conditions. The experiments were conducted in a stator cascade in a water channel at a Reynolds number of Re = 500 000. Inlet guide vanes with movable flaps were used to simulate the periodic variation of the inlet flow angle. As parameters, the mean stagger angle of the stator cascade as well as the phase shift between the sinusoidal movement of the stator and the inlet guide cascade were varied. By using the optical measurement technique High-Speed Particle Image Velocimetry (HS-PIV), the flow fields upstream and downstream of the stator cascade were captured. Overall, the results revealed that the loss coefficient is strongly dependent on the phase shift between the inlet guide cascade and the stator cascade. Using certain phase shifts, a reduction in losses of up to 20% was achieved by the movable stator cascade.
Educational Results Obtained Using an Improved Two-Dimensional Panel Method Code in Undergraduate Fluid Dynamics and Aerodynamics Courses
Authors: Spall Robert , Hodson Joshua
Published: October 2017

Undergraduate required fluid dynamics and elective aerodynamics courses include substantial material on analysis techniques for forces acting on bodies in external flows. These methods include momentum integral analysis, and, for aerodynamic applications, lift computed using circulation and the Kutta-Joukowski theorem. The author presented in a previous FED meeting code development and preliminary classroom results for the implementation of a fully interactive, two-dimensional potential flow solver for flow over both rigid and flexible thin-airfoil (or sail) geometries. The intent of the development was to design a code that could be used as a virtual wind tunnel. The solver was developed in Fortran 90/95 with user interface and graphics routines developed using the high-level plotting library DISLIN for use on Windows-based computers. The analysis code solves the potential flow equations for single or multiple airfoils using a vortex panel method in which the vortex strength varies linearly along the panel and is continuous from one panel to the next. A variety of controls are available to adjust airfoil shapes and angles-of-attack. The user may also specify either rigid thin airfoil shapes, or flexible airfoils in which the final equilibrium shapes are determined by the pressure distribution. Available graphics include velocity vectors, pressure coefficient contours, and streamlines. Lift, axial and normal force coefficients are also output in the form of bar graphs. Several improvements have been implemented in the code, based on early student feedback, to improve its suitability for educational purposes in fluid dynamics and aerodynamics classes. These include pressure plot distributions over the airfoils, the inclusion of standard NACA 4-digit airfoil definitions, the output of velocity and pressure data about a closed contour for use in circulation and momentum integral analysis calculations, and improvements regarding compatibility for use on computers of widely varying screen resolutions. In this work to be presented, recent improvements to the code, and subsequent educational/student learning results based on a series of Qualtrics online student survey questions are presented. These survey questions query the students understanding of a) momentum integral analysis, b) circulation, c) lift calculations using the Kutta-Joukowski theorem, d) airfoil-to-airfoil fluid flow interactions, e) the necessity for attention to details when performing engineering analysis. The code may be downloaded for use by educators and students at other universities.
Fuel-Spray Simulation With Valve Motion Perpendicular to Closing Direction
Authors: Ishii Eiji , Yasukawa Yoshihito , Yoshimura Kazuki , Ogura Kiyotaka
Published: October 2017

Particulate matter (PM) in exhaust gas from automotive engines causes air pollution. Multiple injections of fuel into the combustion chamber is one of the solutions to decrease PM; a uniform air/fuel mixture and short fuel-spray duration by using multiple injections are effective to decrease PM. To form the uniform air/fuel mixture, fuel sprays from fuel injectors needs to be uniform during injections. Unsteady valve-motions, especially those perpendicular to the closing direction, cause spray swings that form un-uniformity of air/fuel mixture. It is difficult to measure valve motions in the space of a few micrometer within a stainless steel body during fuel injections. Fuel-spray simulation is useful to study the effect of valve motion on the un-uniformity of fuel sprays. In fuel-spray simulation, jets passing through nozzles need to be simulated with the valve motion. We previously developed a particle/grid hybrid method that integrated the inner flow simulation using a grid method with a fuel breakup simulation using a particle method. In this study, we studied the effects of valve motions perpendicular to the closing direction on fuel sprays in order to decrease the un-uniformity of air/fuel mixture. First, we observed fuel-spray behaviors during measurements; a fuel injector with multi-holes was selected, and spray patterns were recorded by a CCD camera with a Xenon flash lamp. The jets passing through the nozzles changed their profiles over time, and the widths of the jets changed from thin to thick at almost the same time. The simulated spray behaviors with valve motion in the front-to-rear direction showed the same trends as those in measurement. It is assumed that because the positions of the six nozzles on the orifice cup were assigned asymmetrically in the front-to-rear direction, asymmetric flow distribution caused the valve motion.
Fluid-Structure Interaction With a Fully Integrated Multiphysics Environment
Authors: Grasselt David , Höschler Klaus , Sain Chetan Kumar
Published: October 2017

The paper is focusing on Fluid-Structure Interaction (FSI) process modelling to look for the aero-elastic equilibrium with commercial software packages. The center of intention is to prove whether Ansys Workbench is capable to handle industrial size FSI applications on the one side and to identify possible excitation regions in the example case on the other. The three steps taken to come to a thermal-enhanced bidirectional fluid-structure approach within a fully integrated (monolithic) multiphysics environment are explained: aerodynamic assessment, thermo-structure mechanical setup and unidirectional coupling, as well as bidirectional coupling. Each subchapter describes the specific challenges, how they are solved and which results can be obtained or expected. The paper is focusing on the setup of a bidirectional process chain and does not set the thematic priority on detailed modelling and its results.
Experimental and Computational Characterization of a Large-Scale, Underwater Towed SPIV System
Authors: Harrison Emily L. , Ramsey Joseph P. , Jiang Li
Published: October 2017

A new underwater Stereoscopic Particle Image Velocimetry (SPIV) Torpedo system was designed and constructed at the Naval Surface Warfare Center, Carderock Division for testing in the David Taylor Model Basin. The purpose of the work was to conduct a shakedown test of the new SPIV system to ensure it properly captured SPIV images, and successfully resolved both the in- and out-of-plane velocity fields. To test the system, SPIV measurements were taken on the free-stream flow in the basin and the canonical flow field produced by a circular cylinder at Reynolds numbers around 100,000. After successfully measuring the flow fields, cylinder results were compared to large eddy simulation results that were obtained using NavyFOAM.
Computational Modeling of Particulate Pollutant Transport in a Ventilated Room in the Presence of Two Heated Breathing and Rotating Manikins
Authors: Keshavarz Seyed Ali , Salmanzadeh Mazyar , Ahmadi Goodarz
Published: October 2017

Recently, attention has been given to indoor air quality due to its serious health concerns. Clearly the dispersion of pollutant is directly affected by the airflow patterns. The airflow in indoor environment is the results of a combination of several factors. In the present study, the effects of thermal plume and respiration on the indoor air quality in a ventilated cubicle were investigated using an unsteady computational modeling approach. The person-to-person contaminant transports in a ventilated room with mixing and displacement ventilation systems were studied. The effects of rotational motion of the heated manikins were also analyzed. Simulation results showed that in the cases which rotational motion was included, the human thermal plume and associated particle transport were significantly distorted. The distortion was more noticeable for the displacement ventilation system. Also it was found that the displacement ventilation system lowered the risk of person-to-person transmission in an office space in comparison with the mixing ventilation system. On the other hand the mixing system was shown to be more effective compared to the displacement ventilation in removing the particles and pollutant that entered the room through the inlet air diffuser.
Experimental and Numerical Study of Bubble Drag Reduction on a Flat Plate
Authors: Qin ShiJie , Wu DaZhuan
Published: October 2017

The presence of near wall bubbles may reduce the skin friction drag. This phenomenon has been studied by well designed experiments and combined computational fluid dynamics (CFD) and population balance model (PBM) simulations in this paper. Drag reductions and bubble distributions over a flat plate have been implemented in cavitation tunnel experiments at various flow speeds and air injection rates. CFD-PBM modeling for bubble drag reduction (BDR) has been modified and validated by the flat plate experiments. Drag and lift forces are fully modeled, and bubble breakup and coalescence are calculated. A wide range of bubble sizes are well captured base on the aforementioned numerical consideration. And this modeling work can be further used to design full-scale BDR ships and to discover detailed BDR mechanisms. The predicted drag reductions and bubble distributions are in reasonable accordance with the experimental results. Approximately 30% of BDR is achieved both in the numerical and experimental results. The influence of flow speeds and air injection rates on drag reductions and bubble distributions is discussed. In particular, the mechanism of BDR is analyzed based on the detailed flow filed profiles from numerical simulations. Higher air injection rates generally lead to thicker bubble layer thickness from the rear-part of buffer region (20 < y+ < 30) to turbulent region (y+ > 30). And noticeable increases of air volume fraction in the laminar region (y+ < 5) and forepart of buffer region (5 < y+ < 20). The change of the velocity gradient in the near wall region is considered to be directly related to drag reduction.
Comparative Study on Hydraulic Performance of Single-Suction Centrifugal Pump and Double-Suction Centrifugal Pump
Authors: Wang Chaoyue , Wang Fujun , Zou Zhichao
Published: October 2017

In engineering applications, design and manufacture of double-suction impeller are on the basis of single-suction impeller. However, there is a lack of clear view on the differences of hydraulic performance between single-suction centrifugal pump and double-suction centrifugal pump which has the same blades. In this paper, a single-suction centrifugal pump and double-suction centrifugal pump with the same blades are investigated respectively, and their hydraulic performances have been compared in terms of external characteristics, flow pattern, pressure fluctuation and cavitation characteristics. In operating range of 0.6Q0∼1.1Q0, results show that the efficiency of double-suction pump is 4.14% higher than that of single-suction pump stably, and the head of single suction pump is 3.5% higher than that of double-suction pump stably. Single-suction impeller and double-suction impeller have similar jet-wake structure in impeller outlet, but the amplitude of velocity of single suction impeller changes more sharply. In the vicinity of rated condition, the amplitude of pressure fluctuation of double suction pump is about half that of the single suction pump, and the cavitation performance of double suction pump and single suction pump are basically the same. These quantitative results show that pressure fluctuation characteristics and cavitation performance of single-suction pump and double-suction pump with the same blades have little difference in the vicinity of rated condition. Compared with single-suction pump, the head of double-suction pump has declined, while the efficiency has improved remarkably. The research results have significant guidance on excavating the potential of excellent hydraulic models and guiding the design of double-inlet multistage double-suction centrifugal pump.
Parametrization of High-Speed Train Streamline Shape
Authors: Sun Zhenxu , Zhang Ye , Yang Guowei
Published: October 2017

In the past decade, the high speed trains (HSTs) in China have experienced a booming development, with the design of CRH380A as a predominant example. A series of brand new HSTs have been developed with high aerodynamic performance, which includes the running resistance, the lift of the trailing car, pressure waves when trains pass by each other, aerodynamic noise in the far field, etc. In order to design HSTs with better aerodynamic performance, it is necessary to perform aerodynamic shape optimization, especially to optimize the streamline shape of HSTs. Parametrization is the basis for the whole optimization process, since good parametrization approach not only affects the optimization strategy, but also determines the design space and optimization efficiency. In the present paper, a series of work related to the streamline shape parametrization performed by the author in recent years have been introduced. Four different parametrization approaches have been exhibited, which are Local Shape Function method (LSF) and Free-Foam Deformation method (FFD), Modified Vehicle Modeling Function method (MVMF), Class function/Shape function Transformation method (CST). These methods could be categorized into two kinds: shape disturbance approach (LSF and FFD) and shape description approach (MVMF and CST). Among these four methods, some are developed by the authors while some are locally modified so as to meet the parametrization of the streamline shape. The detailed process of these four approaches are exhibited in the present paper and the characteristics of these four approaches are compared.
Experimental Investigation of Tip Cavitating Vortices in Axial-Flow Pump
Authors: Zhang Desheng
Published: October 2017

The primary goal of this work focuses on the cavitating vortices in the tip region of an axial-flow pump with 3 and 4 blades mainly based on the high-speed imaging experiments, with special attention on the trajectory and dynamics of a large-scale cavitation structure. The hydraulic and cavitation performance between two impellers were compared, and it can be found that the model with 4 blades has a relative wide range of stable operating conditions as well as the better anti-cavitation ability. By the analysis of the cavitation curves, it confirms that the highly unsteady tip cavitation cloud near the blade trailing edge should be responsible for the severe degradation of the performance. According to the detailed study on the cavitation evolution in the two impellers, it is observed that the trajectory of tip cavitating vortices for different flow rates seems very similar determined by the operating conditions. However, the dynamics varies significantly, which is associated with the blade loading and flow passage width.
Numerical Simulation on the Organic Fluid Two-Phase Flow and Heat Transfer in the PEMFC Cooling Plate for Waste Heat Recovery
Authors: Yu Lili , Zhuge Weilin , Zhang Yangjun , Peng Jie
Published: October 2017

The proton exchange membrane fuel cell (PEMFC) system is becoming one of the most potential power systems for automotive applications in the future. Though the efficiency of PEMFC is high, almost half of the hydrogen energy is taken away by coolant without being utilized. Organic Rankine Cycle (ORC) could be used for the waste heat recovery of PEMFC. The working fluid of ORC flows directly into the fuel cell stack and cool the stack as the same time. In this paper, the feasibility of R245ca as the coolant of PEMFC and working fluid of ORC is studied. A simulation model of the fluid flow and heat transfer of R245ca in PEMFC cooling plates is set up with the CFD software package FLUENT. The Volume of Fluid (VOF) model is used to simulate the two-phase flow. Results show that R245ca can efficiently remove the waste heat and ensure uniform temperature distribution in PEMFC.
Assessment of Cavitating Flow Aggressiveness on a Hydrofoil: Experimental and Numerical Approaches
Authors: Carrat Jean-Bastien , Fortes-Patella Regiane , Franc Jean-Pierre
Published: October 2017

The aggressiveness of a partial cavity on a hydrofoil in a cavitation tunnel is investigated from a joint numerical and experimental analysis. The numerical approach is based on a homogeneous equilibrium model and a barotropic law for the liquid/vapor mixture [1, 2] for cold water. The unsteady behavior of the cavity appears in good agreement with experiments although the maximum cavity length is underestimated and the cloud shedding frequency overestimated. The flow aggressiveness is estimated by using the energy approach proposed by Fortes-Patella et al. [3, 4]. The technique predicts a maximum in flow aggressiveness located in the region where the cloud cavity is shed and increases as a power of the flow velocity between 2 and 3.
Development and Commissioning of a Supersonic Blow Down Wind Tunnel for Educational Purposes
Authors: Passmann Maximilian , aus der Wiesche Stefan
Published: October 2017

A cost-effective test rig is presented that allows for the experimental investigation of supersonic flows for educational purposes. The individual units for the test rig were designed and built by students as part of their degrees. The test rig allows for operating times up to 10 seconds and features a nozzle test section, that can house different test objects. The divergent part of the de Laval nozzle geometry is designed using the method of characteristics for planar two-dimensional supersonic flow. State of the art 3D printing technology has been utilized to manufacture the nozzle geometry. Both optical and pneumatic measurement techniques have been adopted for the current setup. A z-type schlieren setup with two parabolic mirrors is used to perform flow visualization. The entire run can be recorded with a digital high speed camera. Stagnation pressure and temperature are measured in the pressure reservoir. Measurements are used to demonstrate basic thermodynamic effects such as the depressurization of gas-filled pressure vessels. Schlieren photography is used to graphically derive the Mach number and some aspects of Mach waves, oblique shock waves, and expansion waves are discussed. Finally, some effects of surface roughness on the flow field are addressed in this paper. Initial tests with the untreated nozzle geometry led to a fine pattern of very weak oblique shock waves in the supersonic part of the nozzle, that were caused by the finite layer thickness of the printer.
Implementation of Immersed Boundary Method in WENO Scheme to Simulate Shock-Structure Interaction
Authors: Xu Min , Yang Tao , Wei Mingjun
Published: October 2017

In the present work, a sharp interface immersed boundary method using ghost-cells is implemented in a traditional 5th-order WENO scheme for shock capturing. To avoid non-physical negative density and pressure involved in high order conservative schemes, a cut-off flux limiter is introduced to enforce the positivity-preserving property, which allows to simulate the flow near vacuum and with strong discontinuities. The combined approach was first benchmarked by a steady oblique shock reflection problem with an exact solution from the oblique shock theory. Then, the algorithm was tested for singularity treatment by another classical problem of shock interaction with a forward facing step. For problems with moving boundaries, the new approach was validated against well-tested numerical solutions of a prescribed moving cylinder problem and a shock-lifting-off-cylinder problem. The agreement in all the benchmark studies shows the accuracy and capability of the current algorithm, in its simple form, to simulate the shockwave interacting with stationary obstacles or moving structures, where the structures′ motion can be either prescribed or determined by fully-coupled dynamics with surrounding flows. Finally, the approach was applied to investigate the impact of shock waves on a deformable body modeled by spring-linked plates, with different spring constants being considered.
Study on Small Fluctuation Stability in Air Cushion Surge Chamber Based on State Space Method
Authors: Liu Jiachun , Zhang Jian , Yu Xiaodong , Xie Hui
Published: October 2017

In this paper, on the basis of the state space method and actual system arrangement, the small fluctuation mathematical model of the water conveyance system with air cushion surge chamber (ACSC) was established. According to the basic equations of ACSC, the ideal gas state equation and the units constant output equation, the formula describing the stable cross-section area (SCSA) of ACSC was deduced, and the small fluctuation stability (SFS) of water conveyance system was analyzed. The corresponding results showed that the air chamber constant had a great influence on the SCSA of ACSC. When the air chamber constant became larger, the quality of the system small fluctuation went worse. The higher upstream water level and the lower initial air chamber height will lead to a smaller initial air chamber constant of ACSC, which is destructive for the stability of the system small fluctuation; As long as the equivalent air quality and air chamber volume are constant, good quality system small fluctuations could be obtained when the initial air chamber height is small and the area of ACSC is large.
Experimental Study on the Effects of Surface Roughness on the Behaviors of Hydrodynamic Instabilities of Couette-Taylor Flow
Authors: Monfared Mostafa , Gaied Lamia , Berrich Emna , Shirani Ebrahim , Bigerelle Maxence , Aloui Fethi
Published: October 2017

Couette-Taylor flow is a type of fluid flow that occurs in the annulus between differentially concentric cylinders, when the outer cylinder is fixed and the inner cylinder rotates and the rotation rate exceeds a critical value. In this research we have studied the effect of surface roughness on the hydrodynamic structures of Couette-Taylor Flow. The PIV technique has been applied for flow visualization. At first, for a smooth surface, the different flow patterns include Couette flow, Taylor vortex flow, wavy vortex flow, modulated wavy vortex flow and turbulent flow. They are investigated numerically and experimentally. The transition Taylor number for every flow regime is also taken into consideration. The results showed that the numerical results correspond quite well to the experimental data. Then, the different surface conditions for inner cylinder which are studied are: a smooth one, a sandpaper-type P180, a canvas plastic with different wire-mesh roughness. They are used to study the effects of surface roughness on the flow structures and critical Taylor numbers.

The experimental results showed that the roughness causes a delay in the appearance of the first instabilities.
Development of Impulse Pressure System for a Large Size Butterfly Valve
Authors: Lee Gi-Chun , Choi Byung-Oh , Lee Young-Bum , Park Jong-Won , Lee Jae-Ho , Kim Jae-Hoon
Published: October 2017

Manufacturing companies have a need for performance and life test equipment to improve the detection of leakage and damage on the seat of valve discs. In the present study, in order to develop such equipment, we first obtained failure data information from the fields, analyzed failure modes based on field data collected from customers, and then obtained our own field data using measuring equipment. Second, we designed and manufactured specific performance and life test equipment. The concept used to fabricate this equipment can be adapted for use with other valves, for example, ball valves and gate valves of various sizes, ranging from 400 mm to more than 2,000 mm. Although increasing the pressure is not difficult in small-sized valve systems, large-sized valve systems require the use of super-large pumps to increase the valve’s internal pressure. Therefore, in this study, the impulse pressure reappearance technique was developed to solve flow shortage during durability test.
Experimental and Numerical Study of the Cloud Cavitating Flow Around a Slender Cylinder With a Petals-Shaped Section
Authors: Wang Yiwei , Huang Jian , Xu Chang , Yu Chao , Huang Chenguang , Wu Xiaocui
Published: October 2017

Three-dimensional flow structures of sheet-to-cloud transition have attracted a lot of attentions in the past years. Cloud cavitating flow around a slender cylinder with the petals shaped section was investigated by experimental and numerical methods. The experiment was performed in a launching system on the basis of the SHPB technology with a high-speed camera. The numerical method was established with large-eddy simulation (LES) and volume of fraction (VOF) approach. Numerical results agree well with experimental data. Interesting phenomena of three-dimensional evolution are observed, especially in which the U-type shedding of cavities are generated repeatedly in the channels along the inner region. Analysis of the unsteady evolution of cavitating flow is performed, and emphasis is placed on the study of the relationship between flow structures around the ridges and channels. Results demonstrate that the pressure gradient variation in the tangential direction of the cylinder is essential for the unsteady development of the cavity including re-entry jet and local shedding. Interactions between the cavity and vortex are also analyzed, which indicates that the U-type cavity/vortex shedding is jointly induced by the re-entry jet and tangential vortex.