bluuebunny/crossref_metadata_2025 huggingface dataset:
Overexpression of claudin‐5 but not claudin‐3 induces formation of trans‐interaction–dependent multilamellar bodies
Authors: Rossa Jan , Lorenz Dorothea , Ringling Martina , Veshnyakova Anna , Piontek Joerg
Published: June 2012

Tight junctions (TJs) regulate paracellular barriers and claudins (Cld) form the backbone of TJ strands. To elucidate the molecular mechanism of claudin polymer formation, TJs were reconstituted by claudin transfection of TJ‐free HEK293 cells. Therewith, typical TJ stands can be found at cell–cell contacts. In addition, overexpression of Cld5‐YFP induces formation of huge intracellular multilamellar bodies. In contrast, Cld3 does not induce similar structures. Inhibition of trans‐interaction of Cld5 by Y148A substitution diminished formation of multilamellar bodies. These results demonstrate claudin subtype‐specific oligomerization. Cld3 and Cld5 localize to the plasma membrane differentially. Phosphorylation at T207 of Cld5 was suggested to participate in regulation of Cld5 internalization. However, prevention of potential phosphorylation by T207A substitution did not increase Cld5 amount in the plasma membrane of transfected cells. Taken together, if carefully evaluated, transfection of claudin constructs in nonpolar cells is a powerful strategy to improve understanding of subcellular targeting and assembly of TJ proteins.
Barriers and more: functions of tight junction proteins in the skin
Authors: Kirschner Nina , Brandner Johanna M.
Published: June 2012

Although the existence of tight junction (TJ) structures (or a secondary epidermal barrier) was postulated for a long time, the first description of TJ proteins in the epidermis (occludin, ZO‐1, and ZO‐2) was only fairly recent. Since then, a wealth of new insights concerning TJs and TJ proteins, including their functional role in the skin, have been gathered. Of special interest is that the epidermis as a multilayered epithelium exhibits a very complex localization pattern of TJ proteins, which results in different compositions of TJ protein complexes in different layers. In this review, we summarize our current knowledge about the role of TJ proteins in the epidermis in barrier function, cell polarity, vesicle trafficking, differentiation, and proliferation. We hypothesize that TJ proteins fulfill TJ structure‐dependent and structure‐independent functions and that the specific function of a TJ protein may depend on the epidermal layer where it is expressed.
Regulation of tight junctions in human normal pancreatic duct epithelial cells and cancer cells
Authors: Kojima Takashi , Sawada Norimasa
Published: June 2012

To investigate the regulation of tight junction molecules in normal human pancreatic duct epithelial (HPDE) cells and pancreatic cancer cells, we introduced the human telomerase reverse transcriptase (hTERT) gene into HPDE cells in primary culture and compared them to pancreatic cancer cell lines. The hTERT‐transfected HPDE cells were positive for PDE markers and expressed claudin‐1, claudin‐4, claudin‐7, and claudin‐18, occludin, tricellulin, marvelD3, JAM‐A, zonula occludens (ZO)‐1, and ZO‐2. The tight junction molecules, including claudin‐4 and claudin‐18 of normal HPDE cells, were in part regulated via a protein kinase C signal pathway by transcriptional control. In addition, claudin‐18 in normal HPDE cells and pancreatic cancer cells was markedly induced by a PKC activator, and claudin‐18 in pancreatic cancer cells was also modified by DNA methylation. In the marvel family of normal HPDE cells and pancreatic cancer cells, tricellulin was upregulated via a c‐Jun N‐terminal kinase pathway, and marvelD3 was downregulated during Snail‐induced epithelial–mesenchymal transition.
Loss of INI1 Protein Expression Defines a Subgroup of Aggressive Central Nervous System Primitive Neuroectodermal Tumors
Authors: Miller Suzanne , Ward Jennifer H. , Rogers Hazel A. , Lowe James , Grundy Richard G.
Published: June 2012

Pediatric embryonal brain tumors can be difficult to classify. Atypical teratoid rhabdoid tumors (ATRT) contain rhabdoid cells, while primitive neuroectodermal tumors (PNETs) are composed of “small round blue cells.” Loss of INI1 is a common event in ATRT; therefore, we investigated if the loss of INI1 protein expression was also observed in central nervous system (CNS) PNET and pineoblastoma. A histological review of 42 CNS PNETs and six pineoblastomas was performed. INI1 expression was assessed by immunohistochemistry. Sequencing was performed on the mutational hotspots of INI1. INI1‐immunonegative tumors were further investigated using fluorescence in situ hybridization. Epithelial membrane antigen (EMA) protein expression was assessed in six CNS PNETs to further define the phenotype. Five CNS PNETs without rhabdoid cell morphology were immuno‐negative for both INI1 and EMA. Of these primary CNS PNET patients, three died <11 months postdiagnosis, which was dissimilar to the INI1‐immunopositive primary CNS PNETs where 18/24 (75%) patients were alive 1 year postdiagnosis. We have identified a small subgroup of CNS PNETs which lack INI1 protein expression, but have no evidence of rhabdoid cell morphology. INI1 protein loss may occur through mechanisms other than gene deletion. INI1 immunohistochemistry should be performed for all CNS PNET cases.
Validation of the Korean version of the Eppendorf Schizophrenia Inventory as a screening measure to detect adolescents at ultra‐high risk for psychosis
Authors: Chung Young‐Chul , Kang Nam‐In , Im Yong‐Jin , Kim Sung‐Wan , Cho In Hee , Lee Young Moon , Kwon Jun Soo
Published: June 2012

Aim: No validated self‐report scale is available for use as a screening tool to detect non‐help‐seeking adolescents at ultra‐high risk (UHR) for psychosis in a community setting. The study aims to examine the reliability and validity of the Korean version of the Eppendorf Schizophrenia Inventory (K‐ESI) for assessing adolescents at UHR for psychosis in a community setting.

Methods: In the first study, to confirm the reliability and discriminant validity of the K‐ESI, community sample (782 adolescents, 281 young adults, 122 early and middle‐aged adults) and outpatients with schizophrenia (109) were recruited. A single cross‐sectional survey was performed using the K‐ESI for the community sample and the K‐ESI and Positive and Negative Syndrome Scale for patients. In the second study, the Korean version of Youth Self Report (K‐YSR) was administered initially to 1002 students. Of the 217 students whose scores were equal to or higher than the cut‐off point of the K‐YSR, 120 who agreed to an in‐depth evaluation were interviewed using the Comprehensive Assessment of At‐Risk Mental States to confirm the predictive validity of the K‐ESI.

Results: The K‐ESI showed good internal consistency and excellent test–retest reliability and discriminant validity. However, the factor structure in adolescents was substantially different from that of the original ESI. The best cut‐off point for the K‐ESI to identify UHR adolescents was 29, with a sensitivity of 77% and a specificity of 70%.

Conclusion: The results revealed that the K‐ESI can be used as a valid and reliable instrument to identify adolescents at UHR for psychosis in a community setting.
Self‐Doubt
Authors: Braslow Matthew D. , Guerrettaz Jean , Arkin Robert M. , Oleson Kathryn C.
Published: June 2012

The need for understanding serves as a theme throughout social and personality psychology. It is reflected in people’s striving toward a shared, social construction of reality (e.g., conformity, uniformity) that runs through so much of the history of theory and research in the field. Stemming from this core motivation, the literature is peppered with illustrations of the preeminence of certainty as a goal (e.g., clarity, consistency, consonance, and related constructs) and the ultimate objective of cultural consensus. Yet, the role of doubt in the form of shaky certainty about the basis for beliefs in attitudes – or doubts about one’s self‐esteem or self‐concept – has increasingly taken center stage. This review takes the self‐competence element (vs. self‐liking element) of self‐worth judgments as its focus and provides an integration of individual difference approaches and experimental investigations of self‐doubt. Long neglected, self‐doubt increasingly appears critical for understanding some of the surprising, ironic, and self‐defeating cognitive, emotional, and behavioral findings seen in the achievement realm.
An Initial Log Analysis of Usage Patterns on a Research Networking System
Authors: Boland Mary Regina , Trembowelski Sylvia , Bakken Suzanne , Weng Chunhua
Published: June 2012

Usage data for research networking systems (RNSs) are valuable but generally unavailable for understanding scientific professionals’ information needs and online collaborator seeking behaviors. This study contributes a method for evaluating RNSs and initial usage knowledge of one RNS obtained from using this method. We designed a log for an institutional RNS, defined categories of users and tasks, and analyzed correlations between usage patterns and user and query types. Our results show that scientific professionals spend more time performing deep Web searching on RNSs than generic Google users and we also show that retrieving scientist profiles is faster on an RNS than on Google (3.5 seconds vs. 34.2 seconds) whereas organization‐specific browsing on a RNS takes longer than on Google (117.0 seconds vs. 34.2 seconds). Usage patterns vary by user role, e.g., faculty performed more informational queries than administrators, which implies role‐specific user support is needed for RNSs. Clin Trans Sci 2012; Volume 5: 340–347
Resistance to environmental stress requires the RNA chaperones CspC and CspE
Authors: Shenhar Yotam , Biran Dvora , Ron Eliora Z.
Published: June 2012

Stress response is essential for adaptation and for survival during environmental changes. A major factor in these responses is RpoS (σS), the master regulator of stationary phase and of the general stress response in Escherichia coli. RpoS is regulated by a complex network at several levels – transcription, translation and proteolysis. Previous studies indicated that rpoS transcripts are stabilized by overexpression of the cold shock proteins CspC and CspE. Here we demonstrate the importance of this transcript stabilization in the regulatory networks governing σS activity. We show that upon entry into stationary‐phase rpoS transcripts are stabilized and this stabilization is necessary for the increased activity of σS. The increase in rpoS transcript stability requires at least one of the cold shock proteins CspC and CspE. We also show that the cellular concentration of CspC – but not CspE – increases concurrently with the increase in rpoS transcript stability, probably accounting for this stabilization. These data expand previous data showing that upon heat shock there is a reduction in CspC levels, coupled to a reduced half‐life of heat shock gene transcripts. Taken together, it appears that CspC levels modulate transcript stability upon exposure to environmental stress while CspE acts as a ‘housekeeping RNA chaperone’ under general stress conditions.
Surgical treatment for portosystemic encephalopathy in patients with liver cirrhosis: Occlusion of portosystemic shunt in combination with splenectomy
Authors: Tashiro Hirotaka , Ide Kentaro , Amano Hironobu , Kobayashi Tsuyoshi , Onoe Takashi , Ishiyama Kohei , Kuroda Shintaro , Tazawa Hirofumi , Kono Hirotaka , Aikata Hiroshi , Takahashi Shoichi , Chayama Kazuaki , Ohdan Hideki
Published: June 2012

Aim:  Operative ligation of the portosystemic shunt may control hepatic encephalopathy effectively, but the subsequent increase in portal vein pressure (PVP) leads to high mortality. Splenectomy can decrease inflow into the portal system, resulting in decreased portal pressure.

Methods:  We retrospectively examined the effect of splenectomy in combination with shunt closure on portosystemic encephalopathy.

Results:  Clinical symptoms of encephalopathy disappeared in all six patients who underwent splenectomy in combination with portosystemic shunt ligation, with the exception of one patient who had relapsing encephalopathy after 6 months. Follow‐up computed tomography showed complete obliteration of the portosystemic shunts, except in the one patient with relapsing encephalopathy who underwent balloon‐occluded retrograde transvenous obliteration for the remaining splenorenal shunt 8 months after surgery. PVP significantly decreased after splenectomy. PVP did not increase to the baseline PVP value after ligation of the shunts, except in two patients who had elevated PVP after surgery: PVP increased from 18 to 19 mmHg after ligation in one patient and from 18 to 23 mmHg in one patient.

Conclusion:  Splenectomy followed by surgical ligation of the portosystemic shunt may be feasible and safe for cirrhotic patients with portosystemic shunts.
Mammary gland carcinoma in a dog with peripheral blood and bone marrow involvement associated with disseminated intravascular coagulation
Authors: Jaillardon Laetitia , Barthélemy Anthony , Goy‐Thollot Isabelle , Pouzot‐Nevoret Céline , Fournel‐Fleury Corinne
Published: June 2012

A 7‐year‐old female Leonberger dog was referred to the National Veterinary School of Lyon Teaching Hospital with a 2‐day history of anorexia and bleeding. A mammary mass had been removed 7 months earlier, but histologic examination was not performed. On physical examination, the dog was depressed and had pale mucous membranes and numerous petechiae and hematomas. Significant laboratory findings were moderate thrombocytopenia, prolonged prothrombin, activated partial thromboplastin, and thrombin times, hypofibrinogenemia, and increased concentration of fibrin(ogen) degradation products. A peripheral blood smear, buffy coat preparation, and bone marrow aspirate contained low numbers of large atypical cells that had moderate nuclear:cytoplasmic ratios, oval nuclei with multiple prominent nuclei, and basophilic cytoplasm with villous projections. A small nodule was found in the left inguinal mammary gland, and a fine‐needle aspirate contained cells similar to those in blood and bone marrow. In samples of blood, bone marrow, and the mammary mass, the neoplastic cells were immunoreactive for cytokeratin. The diagnosis was mammary carcinoma with secondary disseminated intravascular coagulation (DIC) and disseminated tumor cells in bone marrow and circulating tumor cells in blood; this diagnosis was not confirmed by histopathologic examination. Owing to clinical deterioration and the poor prognosis, the dog was euthanized and a necropsy was not performed. This is the first report of a canine mammary carcinoma with circulating tumor cells and secondary DIC.
TRIBUTE TO BOB SHARPLES
Authors: SORABJI RICHARD
Published: June 2012

Bob Sharples joined me in London in a different college in 1973, and we worked closely together for 37 years until his untimely death at the age of 61. Our collaboration included innumerable research seminars, many teaching classes and publications and a very good number of conferences, with an emphasis on post-Aristotelian Philosophy. He became one of the world's leading experts on the school of Aristotle and the leading scholar in the English-speaking world on Aristotle's greatest interpreter and defender, Alexander of Aphrodisias. His characteristically generous messages to participants after seminars were an immense aid to everyone else's research. He taught not only in University College, London, where he became Professor and Head of the Department of Greek and Latin, but also in the Institute of Classical Studies, and for the Open University. His courage in bereavement and illness was remarkable, and his enormous bibliography, printed here, but excluding individual book reviews and posthumous forthcoming publications, is one sign of the indelible mark he has left on the subject.
Respect response to Dixon et al. (2012) ‘Perpetrator programmes for partner violence: Are they based on ideology or evidence?’
Authors: Debbonaire Thangam , Todd Jo
Published: June 2012

Purpose. This article is a commentary on Dixon, Archer, & Graham‐Kevan's (2012) critique of the Respect position statement on gender, which concluded by calling for abandoning either Respect or the Respect accreditation system.

Methods. The article starts by providing some factual information about Respect and about the accreditation system mentioned in Dixon et al. It then picks up on five specific aspects of the discussion: research notions, prevalence, homicide, the relevance of gender to work on intimate partner violence, and our work to support male victims.

Results. Dixon et al. critique one document in order to call for the abandonment of a system of accreditation which is not connected to that document. Dixon et al. ignored other relevant research (such as that on partner homicide) and practice evidence that contradicts their assertions. This includes ignoring the existence of Respect's work with male victims, including running the male victims helpline.

Conclusions. Respect work is informed by knowledge and experience from research and practice. There is substantial evidence from research to support the position statement on gender. The accreditation standard and system of accreditation was established before the position statement was written and is not included. Respect provides valuable services for male victims and for male and female perpetrators.
Scientific reasoning in early and middle childhood: The development of domain‐general evidence evaluation, experimentation, and hypothesis generation skills
Authors: Piekny Jeanette , Maehler Claudia
Published: June 2012

According to Klahr's (2000, 2005; Klahr & Dunbar, 1988) Scientific Discovery as Dual Search model, inquiry processes require three cognitive components: hypothesis generation, experimentation, and evidence evaluation. The aim of the present study was to investigate (a) when the ability to evaluate perfect covariation, imperfect covariation, and non‐covariation evidence emerges, (b) when experimentation emerges, (c) when hypothesis generation skills emerge, and (d), whether these abilities develop synchronously during childhood. We administered three scientific reasoning tasks referring to the three components to 223 children of five age groups (from age 4.0 to 13.5 years). Our results show that the three cognitive components of domain‐general scientific reasoning emerge asynchronously. The development of domain‐general scientific reasoning begins with the ability to handle unambiguous data, progresses to the interpretation of ambiguous data, and leads to a flexible adaptation of hypotheses according to the sufficiency of evidence. When children understand the relation between the level of ambiguity of evidence and the level of confidence in hypotheses, the ability to differentiate conclusive from inconclusive experiments accompanies this development. Implications of these results for designing science education concepts for young children are briefly discussed.
Assessment of Enhanced Multi-Dimensional Limiting Process for Multi-Dimensional Flows
Authors: Kim Kyu Hong , Park Jung Ho
Published: June 2012

In this paper, a new limiting process based on the Multi-dimensional Limiting Process, called enhanced Multi-dimensional Limiting Process is developed and tested with several cases. The enhanced Multi-dimensional Limiting Process, e-MLP has a number of useful features of MLP limiter such as multi-dimensional monotonicity and straightforward extensionality to higher order interpolation. It is applicable to local extrema and prevents excessive damping in a linear discontinuous region through application of appropriate limiting criteria. It is efficient because a limiting function is applied only to a discontinuous region. In addition, it is robust against shock instability due to the strict distinction of the computational domain and the use of regional information in a flux scheme as well as a high order interpolation scheme. The new limiting process was applied to numerous test cases. Through these tests, we could confirm that e-MLP enhances the accuracy and efficiency with both continuous and discontinuous multidimensional flows.
Efficient and Accurate Limiting Strategy for Discontinuous Galerkin Methods on Triangular and Tetrahedral Meshes
Authors: Park Jin Seok , Kim Chongam
Published: June 2012

The present paper deals with the robust, accurate and efficient limiting strategy for discontinuous Galerkin methods for high speed compressible flow. The present limiting strategy is a continuous work of extending multi-dimensional limiting process (MLP), which has been successful in finite volume methods (FVM), into discontinuous Galerkin (DG) methods on triangular and tetrahedral meshes. Based on successful analyses and implementations of the MLP slope limiting in FVM, MLP is applicable into DG framework with the MLP-based troubled-cell marker and the MLP slope limiter. It is observed that the proposed approach yields outstanding performances in resolving non-compressive as well as compressive flow features.
Studies on Flow Transition Under Simulated Low Pressure Turbine Conditions Based on a High Order LES Model
Authors: Biswas Debasish , Jimbo Tomohiko
Published: June 2012

Boundary layer transition is an important phenomenon experienced by the flow through gas turbine engines. A substantial fraction of the boundary layer on both sides of a gas turbine airfoil may be transitional. The extended transition zone exist due to strong favorable pressure gradients, found on both near the leading edge portion of the suction side and the pressure side, which serve to stabilize the boundary layer and consequently delay the transition process, even under high free-stream turbulence intensity (FSTI) in practical gas turbine. It is very important to properly model and predict the high FSTI transition mechanism, since boundary layer transition leads to substantial increase in friction coefficients and heat transfer rate. Near wall turbulence production is thought to be largely absent in the non-turbulent zone. The intermittent nature of transition need to be taken into account in developing improved transition model. Much has been learned from the to date, but the nature of separated flow transition is still not completely clear, and existing models are still not robust as needed for accurate prediction. Therefore, in the present work a high order LES turbulent model proposed by the author is used to predict the separated flow transition. The experimental data of Volino is chosen for this comparison purpose. In his experimental work, the flow through a single-passage cascade simulator is documented under both high and low FSTI conditions at several different Reynolds numbers. The geometry of the passage (in Volino’s work) corresponds to that of the “Pak-B” airfoil, which is an industry supplied research airfoil that is representative of a modern, aggressive LP turbine design. Volino’s data included a complete documentation of cases with Re as low as 25,000 and also the documentation of turbulent shear stress in the boundary layer under both high and low FSTI.
Modeling of a One-Equation LES for Plant Canopy Flows
Authors: Hiraoka Hisashi
Published: June 2012

A one-equation-type subgrid-scale (SGS) model was proposed in order to enable the large eddy simulation (LES) of plant canopy flows. The SGS kinetic energy equation was derived from the equations of continuity and Navier-Stokes. This equation was closed by modeling the unknown terms according to the physical meaning of each term in the equation. The wake production term in the SGS kinetic equation could be derived analytically. However, the wake dissipation term did not appear when the SGS kinetic energy equation was derived from the basic equations.
A Stable Compact Finite Difference Method With Skew-Symmetric Form for LES of Variable Density Flows
Authors: Takeichi Kota , Tamano Shinji , Morinishi Yohei
Published: June 2012

The objective of this study is to develop a reliable high-order numerical method for the large eddy simulation (LES) of variable density flows. To improve both the numerical accuracy and stability, we use the compact finite difference method (compact FDM) for the transport equation of compressible flows, in which the skew-symmetric form of the convection term is adopted. In the LES of turbulent flows, the reliability of computational results depends strongly on both the reliability of the subgrid scale (SGS) model and the accuracy of the numerical method. First, the reliability is investigated by performing numerical simulations with unresolved grid resolution for compressible turbulent channel flows without SGS models. Then, we perform the LES of compressible turbulent channel flows with several dynamic and non-dynamic SGS models, and compare turbulence statistics with the corresponding DNS data.
A New Hybrid RANS/LES Modeling Methodology for CFD Applications
Authors: Alam Mohammad F. , Walters D. Keith , Thompson David S.
Published: June 2012

The primary weakness of current hybrid RANS/LES (HRL) models lies in the treatment of the “transition zone,” where the value and the physical interpretation of the eddy viscosity changes from LES to RANS, or vice versa. In order to address this problem, the initial version of a new HRL modeling methodology has been developed that incorporates two separate turbulent stress parameters (one from the LES model and the other from the RANS model). In this paper, the viability of the new model is demonstrated by predictions of the flow over a backward facing step, which is one of the canonical test cases used for the validation of turbulence models. The simulation results of backward facing step flow at ReH = 37,000 provided by Menter’s Shear Stress Transport (SST) model, a new version of Detached Eddy Simulation (DES) i.e. delayed DES model, and the new model are compared with experiments. Mesh sensitivity of the models is also studied employing two different types of mesh, in order to test the wide applicability of the HRL models in various realistic flow simulations. Pressure and skin friction distributions and mean velocity profiles obtained with the new HRL model show improved agreement with the experimental measurements versus DES, and less sensitivity to the mesh details. Turbulent kinetic energy profiles of both the new model and the RANS model show qualitatively good agreement with experiments.
Applicability of Turbulence Models on Characteristics Prediction of Centrifugal Pumps
Authors: Wang Yong , Liu Houlin , Yuan Shouqi , Tan Minggao , Shu Minhua
Published: June 2012

In order to research the applicability of turbulence model on characteristics prediction of centrifugal pumps at the design condition, standard k-ε turbulence model, k-ω turbulence model and SST turbulence model are selected, which are commonly used in the numerical prediction for head, efficiency and NPSHr of the centrifugal pumps. By using commercial code ANSYS CFX, the all three turbulent models are used to predict the characteristics of six centrifugal pumps with the different specific speeds at the design condition, which are varied from 34.3 to 260.5. The calculation results are compared with the experimental data, and the comparison indicates that all the prediction results obtained from different turbulence models are more or less different from the experimental data. The head and efficiency predicted by SST turbulence model and k-ω turbulence model are closer and they are all bigger than that predicted by k-ε turbulence model. For low specific speed centrifugal pumps, the head and efficiency predicted by SST model and the NPSHr predicted by k-ε turbulence model are more closer to the experimental values; while for the medium and high specific speed centrifugal pumps, the head and efficiency predicted by k-ε turbulence model are better than that predicted by other models. The k-ω turbulence model and k-ε turbulence model are the best choice to predict NPSHr of medium and high specific speed centrifugal pumps respectively.
Modelling Multiphase Jet Flows for High Velocity Emulsification
Authors: Ryan David , Simmons Mark , Baker Mike
Published: June 2012

Single phase steady-state Computational Fluid Dynamics (CFD) simulations are presented for turbulent flow inside a Sonolator (an industrial static mixer). Methodology is given for obtaining high quality, converged, mesh-independent results. Pressures, velocities and local specific turbulent energy dissipation rates throughout the fluid domain are obtained for three industrially-relevant mass flow rates at a fixed nozzle orifice size. Discharge coefficients calculated at the orifice are compared to literature values and to pilot plant experiments for initial validation. Streamlines in the flow are used to illustrate the presence of recirculation zones after the nozzle. Thus, residence time and peak local specific turbulent energy dissipation rates are calculated from streamline data as a function of inlet position. Values of local specific turbulent energy dissipation rate obtained are used to infer drop sizes for emulsification of a multiphase mixture under dilute, homogeneous flow conditions. The results show that different drop size distributions may be produced depending on the inlet condition of the multiphase mixture.
CFD Simulations of Cap-Bubbly Two-Phase Flows Using Two-Group Interfacial Area Transport Equation
Authors: Wang Xia , Sun Xiaodong
Published: June 2012

Knowledge of cap-bubbly flows is of great interest due to its role in understanding of flow regime transition from bubbly to slug or churn-turbulent flow. One of the key characteristics of such flows is the existence of bubbles in different sizes and shapes associated with their distinctive dynamic natures. This important feature is, however, generally not well captured by available two-phase flow models. In view of this, a modified two-fluid model, namely a three-field two-fluid model, is proposed. In this model, bubbles are categorized into two groups, i.e., spherical/distorted bubbles as Group-1 while cap/churn-turbulent bubbles as Group-2. A two-group interfacial area transport equation (IATE) is implemented to describe the dynamic changes of interfacial structure in each group, resulting from intra- and inter-group interactions and phase changes due to evaporation and condensation. Attention is also paid to the appropriate constitutive relations of the interfacial transfers due to mechanical and thermal non-equilibrium between different fields. The proposed three-field two-fluid model is used to predict the phase distributions of adiabatic air-water flows in a narrow rectangular duct. Good agreement between the simulation results from the proposed model and relevant experimental data indicates that the proposed model may be used as a reliable computational tool for two-phase flow simulations in narrow rectangular flow geometry.
Numerical Prediction of Low Mach Number Jet Noise Ejected From Slit Nozzle
Authors: Yamaguchi Minoru , Iwata Yusuke , Akishita Sadao , Ogami Yoshifumi
Published: June 2012

Prediction of the low Mach number jet noise ejected from rectangular nozzle with high aspect ratio is described. Firstly measurement of the jet noise was conducted in semi-anechoic wind tunnel at the low Mach number flow condition. We were found that the sound power of the jet obeyed 6-th power of jet velocity. This means the jet noise is resulted not from quadrupole distribution in the shear flow of jet, but from dipole distribution on the surface of the exit of the nozzle. The model of vortex sound is applied as the sound generation mechanism at numerical simulation. The sound emission from the vortices in the shear flow is modified with the compact Green’s function representing the scattering effect from the surface of the exit of the nozzle in the lower frequency range. It is also modified with the non-compact Green’s function in the higher frequency range. Lastly calculated sound spectra are compared with measured spectra. The comparison will prove effectiveness of this modeling.
Shear-Thickening Flow Between Coaxial Cylinders
Authors: Ashrafi Nariman , Haghighi Habib Karimi
Published: June 2012

The effects of nonlinearities on the stability are explored for shear thickening fluids in the narrow-gap limit of the Taylor-Couette flow. A dynamical system is obtained from the conservation of mass and momentum equations which include nonlinear terms in velocity components due to the shear-dependent viscosity. It is found that the critical Taylor number, corresponding to the loss of stability of Couette flow becomes higher as the shear-thickening effects increases. Similar to the shear thinning case, the Taylor vortex structure emerges in the shear thickening flow; however they quickly disappear thus bringing the flow back to the purely azimuthal flow. Naturally, one expects shear thickening fluids to result in inverse dynamical behavior of shear thinning fluids. This study proves that this is not the case for every point on the bifurcation diagram.
Numerical Investigation of Countercurrent Two-Phase Flows Using Three-Dimensional Volume-of-Fluid Simulations
Authors: Gue´don Gae¨l , Colombo Emanuela , Inzoli Fabio
Published: June 2012

Several engineering plants and components, such as nuclear reactors, boilers, bubble columns, chemical reactors or oil/gas wells may be characterized by two-phase flows. Appropriate and safe operation of these systems may be supported by the accurate prediction of the multiphase flow pattern with consistent estimation of the void fraction and flooding phenomenon. A preliminary approach for modeling flow patterns in countercurrent two-phase flows in vertical systems, based on the volume-of-fluid (VOF) method, is here presented. The general objective of the study is to investigate the feasibility of large scale two-phase systems simulations using the VOF method. The specific objective is to provide a first set of qualitative information about the fluid dynamics structures in this flow at specific operating conditions. Three-dimensional simulations are performed using a finite volume commercial CFD code. Validation of the numerical approach is achieved with experimental data taken from literature for typical air-water flows in bubble columns. The interaction of the downward water recirculation with the bubbles of air is indeed representative of a bubbly countercurrent two-phase flow and therefore may be a valuable test case. The use of the VOF method is here privileged, since no further closure relations are needed for exchange coefficients between the continuous and dispersed phases, and for breakup and coalescence of bubbles/drops. The validated model is therefore most likely applicable in complex situations where the flow behavior is unknown. Finally a specific analysis of a countercurrent two-phase flow is presented with the objective of simulating the flow within an industrial pipe where two immiscible fluids, with different density are injected. A fluid “A” is injected at the bottom of the pipe and it is supposed to exit the pipe in the upper part. A fluid “B”, immiscible in “A”, is injected at the top of the pipe in countercurrent and it is supposed not to influence the path of fluid “A” from inlet to the exit. Fluid “B” may be used for reacting somehow with fluid “A”, but in this paper only the fluid dynamic condition is considered.
An Approach of Computational Hemodynamics for Cardiovascular Flow Simulation
Authors: Liu J. L. , Qian Y. , Itatani K. , Miyakoshi T. , Murakami A. , Ono M. , Shiurba R. , Miyaji K. , Umezu M.
Published: June 2012

Computational fluid dynamics (CFD) is one of available methods to quantitatively evaluate the treatments of cardiovascular disease. However, currently, applications of this technology to cardiac surgery are few due to the complexity of performing physiological simulation. Here, we used CFD to study the outcome of the Norwood surgical procedure for palliating hypoplastic left heart syndrome in a 33-month-old child. The Reynolds number for post-surgical flow calculated at the peak of systole was about 4000, consistent with turbulent flow. During diastole, by contrast, the flow reduced to low speed, suggesting the strong transition flow from systole to diastole. Therefore, to improve the simulation of transitional flow, we determined that time step intervals of 10−5 second were best in using the k–ε turbulence model. We also develop a new boundary condition to simulate blood pressure wave reflection from peripheral vessels in order to physiologically capture pressure recovery and correctly obtained flow through each arch-branch and flow pattern in the coronary. Then we computed time-varying energy losses, local pressure, and wall shear stress at the anastomosis to evaluate the surgical outcome. The results suggest the time step and boundary conditions that take account of pressure wave reflection improve simulation of cardiovascular flow.
Subchannel Analysis of Single-Phase Flow Sodium Tests With Non-Uniform Radial Power Distributions
Authors: Pramuditya Syeilendra , Ninokata Hisashi
Published: June 2012

Subchannel analysis calculations for sodium experimental data have been performed. Performance of several conventional flow resistance and mixing models was assessed, by comparing predicted outlet temperature profiles against experimental data. By using conventional method, it was found that the results agree well with the experimental data, with RMS errors between 3.4–5.6%. Calculations by employing non-uniform control volume for each subchannel have also been performed. This variation of control volume is due to the presence of wire spacer. The subchannel control volumes are varied based on dividing every wire axial pitch into 12 segments (H/12). It is showed that this simple method is able to simulate the flow field in a relatively more realistic way. It was found that the results by employing this simple method agree well with experimental data, in which the RMS errors are between 4.1–9%. The advantages of this H/12 method are its simplicity and its ability to reproduce the flow field inside subassembly.
A Numerical Investigation of the Effects of Flow Pulsations on the Drag Force Over a Cylinder
Authors: D’herde Eric , Guessous Laila
Published: June 2012

Flow over a cylinder is a fundamental fluid mechanics problem that involves a simple geometry, yet increasingly complex flow patterns as the Reynolds number is increased, most notably the development of a Karman vortex with a natural vortex shedding frequency fs when the Reynolds number exceeds a value of about 40. The goal of this ongoing study is to numerically investigate the effect of an incoming free-stream velocity pulsation with a mean Reynolds number of 100 on the drag force over and vorticity dynamics behind a circular cylinder. This paper reports on initial results involving unsteady, laminar and incompressible flows over a circular cylinder. Sinusoidal free-stream pulsations with amplitudes Av varying between 25% and 75% of the mean free-stream velocity and frequencies f varying between 0.25 and 5 times the natural shedding frequency were considered. Of particular interest to us is the interaction between the pulsating frequency and natural vortex shedding frequency and the resulting effects on drag. Interestingly, at frequencies close to the natural frequency, and to twice the natural frequency, a sudden drop in the mean value of the drag coefficient is observed. This drop in the drag coefficient is also accompanied by a change in the flow and vortex shedding patterns observed behind the cylinder.
A Full Eulerian Finite Difference Method for Hyperelasic Particles in Fluid Flows
Authors: Sugiyama Kazuyasu , Ii Satoshi , Takeuchi Shintaro , Takagi Shu , Matsumoto Yoichiro
Published: June 2012

A full Eulerian finite difference method has been developed for solving a dynamic interaction problem between Newtonian fluid and hyperelastic material. It facilitates to simulate certain classes of problems, such that an initial and neutral configuration of a multi-component geometry converted from voxel-based data is provided on a fixed Cartesian mesh. A solid volume fraction, which has been widely used for multiphase flow simulations, is applied to describing the multi-component geometry. The temporal change in the solid deformation is described in the Eulerian frame by updating a left Cauchy-Green deformation tensor, which is used to express constitutive equations for incompressible hyperelastic materials. The present Eulerian approach is confirmed to well reproduce the material deformation in the lid-driven flow and the particle-particle interaction in the Couette flow computed by means of the finite element method. It is applied to a Poiseuille flow containing biconcave neo-Hookean particles. The deformation, the relative position and orientation of a pair of particles are strongly dependent upon the initial configuration. The increase in the apparent viscosity is dependent upon the developed arrangement of the particles.
Numerical Simulation of Formation and Breakup of a Compound Jet by the Front–Tracking/Finite Difference Method
Authors: Vu Truong V. , Homma Shunji , Wells John C. , Takakura Hideyuki , Tryggvason Gretar
Published: June 2012

The formation and breakup of an axisymmetric immiscible, viscous, laminar compound jet flowing vertically downward into and breaking up in another immiscible liquid is studied numerically. We use a front-tracking/finite difference method to track the unsteady motion and the breakup of the compound jet interfaces, which are governed by the incompressible Navier-Stokes equations for Newtonian fluids. We consider the formation and breakup of a three-fluid compound jet in which the inner fluid density is greater than the shell’s fluid density, and compare with the case when the inner fluid density is less than the shell’s fluid density. The effects of interfacial tensions in terms of Weber number are investigated. An increase in Weber number leads to an increase in the breakup length of the compound jet and a decrease in the size of compound drops.
Numerical Simulations of Droplets on Porous Structures by Use of Lattice Boltzmann Method
Authors: Matsukuma Yosuke , Inoue Gen , Minemoto Masake
Published: June 2012

This paper demonstrates numerical simulations of droplet on gas diffusion layer of the polymer electrolyte fuel cell. The lattice Boltzmann method for incompressible two-phase flows at high density ratios were applied for the simulations in order to precisely predict the shape and moving velocity of water droplet surrounding by the air in the gas channel. Simulations were conducted in 2D and 3D and height and moving velocity of droplet were compared with experiment as a function of mean gas velocity in the gas channel. The droplet heights by the simulations were qualitatively agreed with the experimental data, while the simulation results of moving speed of droplet somewhat overestimated the experimental results.
Numerical Analysis of Ventilated Cavitation Using Non-Condensable Gas Injection on Underwater Vehicle
Authors: Kim Dong-Hyun , Ha Cong-Tu , Park Warn-Gyu , Jung Chul-Min
Published: June 2012

Supercavitating torpedo uses the supercavitation technology that can reduce dramatically the skin friction drag. The present work focuses on the numerical analysis of the condensable/non-condensable cavitating flow around the supercavitating torpedo. The governing equations are the Navier-Stokes equations based on the homogeneous mixture model. The cavitation model uses a new cavitation model which was developed by Merkle (2006). The multiphase flow solver uses an implicit preconditioning scheme in curvilinear coordinates. The ventilated cavitation is implemented by non-condensable gas injection on backward of cavitator cone and the base of the torpedo.
Design Optimization of Cryogenic Pump Inducer Considering Suction Performance and Cavitation Instability
Authors: Watanabe Hiroyoshi , Tsukamoto Hiroshi
Published: June 2012

This paper presents the result of design optimization for three-bladed pump inducer using a three-dimensional (3-D) inverse design approach, Computational Fluid Dynamics (CFD) and DoE (Design of Experiments) taking suction performance and cavitation instability into consideration. The parameters to control streamwise blade loading distribution and spanwise work (free vortex or non-free vortex) for inducer were chosen as design optimization variables for the inverse design approach. Cavitating and non-cavitating performances for inducers designed using the design variables arranged in the DoE table were analyzed by steady CFD. Objective functions for non-cavitating operating conditions were the head and efficiency of inducers at a design flow (Qd), 80% Qd and 120% Qd. The volume of the inducer cavity region with a void ratio above 50% was selected as the objective function for inducer suction performance. In order to evaluate cavitation instability by steady CFD, the dispersion of the blade surface pressure distribution on each blade was selected as the evaluation parameter. This dispersion of the blade surface pressure distribution was caused by non-uniformity in the cavitation length that was developed on each inducer blade and increased when the cavitation number was reduced. The effective design parameters on suction performance and cavitation instability were confirmed by sensitivity analysis during the design optimization process. Inducers with specific characteristics (stable, unstable) designed using the effective parameters were evaluated through experiments.
Sensitivity Analysis of a Centrifugal Compressor Using the Linearization Method
Authors: Asli Majid , Tousi Abolghasem M.
Published: June 2012

In this paper the behavior of a centrifugal compressor in response to little variations of some geometric and thermodynamic factors is presented. First-order sensitivity analysis is applied. At first, design equations were specified and linearization was done according to variable and target parameters. These new equations were solved based on parameters and so these linear equations lead to some charts which indicate the effects of little variation in geometric and thermodynamic factors on some performance parameters. The accuracy of this first-order analysis is verified by CFD analysis for a sample case. The two results for the case of 2 percent increase in impeller inlet radius typically are found to be in good agreement. Their agreement shows that the linearization method can be applicable for sensitivity analysis of some simple cases with little acceptable error. The simplicity of this method makes it prominent among other methods like CFD.
Twenty Five Years of Mesh Generation: A Personal Perspective
Authors: Dawes William N.
Published: June 2012

Since starting research in CFD the early 1980’s as a PhD Student I have worked with a variety of mesh types and topologies. The main application areas have been in aerospace, mostly in turbomachinery, but also in racing car aerodynamics and in the oil & gas process industries. The first meshes I used were simple, sheared H meshes for blade-to-blade flows; these were — and still are — perfectly adequate for this class of simulation and are in use to this day in routine design all around the world. However, most application areas are fundamentally more complex, both in terms of geometry and of flow physics, and necessitate more complex mesh systems. Current simulation trends are relentlessly towards using fully featured, fully 3D geometry and effective, high-productivity mesh generation systems have become of central significance. Over the past twenty five years I have worked with simple structured meshes, multi-block meshes, unstructured meshes based both on Delaunay and advancing front paradigms and, more recently, on octree-based cut-Cartesian meshes and associated body-conformal, hybrid meshes. This has gone hand in hand with increasing interest in computational geometry and geometry editing and parameterisation to support automated design optimisation. This paper represents my personal perspective on these experiences.