bluuebunny/crossref_metadata_2025 huggingface dataset:
Datos histopatológicos para la identificación de una reacción por material de relleno en patología bucal. Revisión bibliográfica y presentación de tres casos / Histopathologic features to identify a filler material reaction in oral pathology. Literature..
Authors: Sulbarán Prieto Ana Celia , Bustillo Rojas Jairo Alberto
Published: December 2016

ABSTRACT. Background: Filler materials injections in orofacial tissues is a practice that grows annually and may be followed by a reaction involved from small inflammatory nodules to large and diffuse granulomas, it’s may develop month or years after de procedure, making it difficult the diagnosis. Objective: Identify histopathological features of a reaction to materials filler through a literature review and report three cases in orofacial region. Method: We made an exhaustive investigation of scientific articles related with filler materials commonly used in orofacial region and clinical cases of foreign body reaction by filler material with emphasis in the histopathological features. The search was made in the database PubMed and Scholar Google from the 2004 - 2015 period. Additionally, we collect three cases diagnosed as foreign body reaction by exogenous material in oral pathology laboratory of Anzoátegui state, Venezuelan. Results: We found just 10 articles with clinical cases and its histopathological features. Other 3 review articles explain specific characteristics for each filler material. Based on this review, we confirm the 3 cases presented. Conclusions: Few studies describe the histopathological features of a filler material reaction and the kind of material; nevertheless, were synthesized for the confirmation of cases.
Dossier temático: Odontología legal y forense / Thematic Dossier: Legal and Forensic Dentistry
Authors: Mon Núñez José Medín , Escobar Velásquez Luz Dary , Zárate Rodríguez Juan Carlos
Published: December 2016

En este editorial, tres destacados especialistas latinoamericanos, quienes sirvieron como editores invitados, introducen el dossier Odontología Legal y Forense. Los autores presentan un perfil resumido del trabajo odontológico y su importancia cuando se pone al servicio de la ley, principalmente en temas de identificación. Adicionalmente, listan los temas generales de los artículos que contiene el dossier.
Función motora oral del lactante como estímulo de crecimiento craneofacial / Infant Oral Motor Function as a Stimulus for Craniofacial Growth
Authors: López Rodríguez Yuli Natalia
Published: December 2016

Background: The growth of the craniofacial complex is essential for infant health as it is one of the best predictors of overall growth. Moreover, the facial development depends on stimuli such as suction, breathing, chewing, and swallowing, which induce an adequate facial anatomy and shape face structure. The motor activity is also influenced by the type of feeding that is part of child development. Purpose: To analyze the effects of oral motor function in the proper development of craniofacial structures in children, while considering biological mechanisms and type of feeding. Methods: A critical review of literature was carried out with the aim of analyzing the relationship between biological mechanisms, type of feeding, and infant oral functional processes as mechanisms to stimulate craniofacial growth. Results: An appropriate oral motor function induces optimal craniofacial growth. The type of feeding is a determinant of growth. Breastfeeding is essential for optimal craniofacial growth and the prevention of dentomaxillofacial anomalies. Craniofacial shape and function depend of the balance between bone structure and muscle mechanical load. Conclusion: Breastfeeding is the best way to promote growth and development of craniofacial structures, maturation of infant oral motor function and the incidence decrease of malocclusion indicators. Craniofacial growth depends of a favorable bone and muscle condition.
Niños con hemofilia y su atención odontológica por estomatología pediátrica. Revisión de la literatura / Children with Hemophilia and their Dental Care by Pediatric Stomatology. Review of Literature
Authors: Grandas Ramírez Ángela Liliana
Published: December 2016

ABSTRACT. Purpose: To carry out systematic review of literature about diagnostics, severity, and dental treatment considerations of children with Hemophilia A. Methods: The search for articles and other document was conducted through the databases available at the National Library System of the National University of Colombia. The English and Spanish terms used in the search were “pediatric dentistry,” “hemophilia A,” dental care,” “coagulation factors,” and/or “coagulation disorders.” Results: The sample consisted of 29 articles that met the inclusion criteria. Hemophilia A is a congenital disorder caused by a deficiency of coagulation factor VIII. Treatment of hemophilia depends on its severity and focuses on avoiding risking life of children due to preventable bleeding by timely applying local therapies such as tranexamic acid or factor VIII, depending on dental needs. Dental treatment of hemophilia A should be interdisciplinary and must emphasize primary health care, health promotion, and prevention in order to avoid invasive dental treatments that could cause bleeding. In addition, treatments seek to maintain oral health and to provide quality of life to children living with hemophilia A.
La odontología en el diagnóstico del maltrato infantil / Dentistry and Child Abuse Diagnosis
Authors: Doria Martínez Ana Milena , Navarro Chong Melissa Ivette
Published: December 2016

Abstract. Background: Child abuse was first described in 1868 by pathologist Ambrosio Tardieu, but it was until the last century when the role of the dentist became relevant to early diagnose this syndrome. Several studies have shown that close to 50 % of head and face trauma is caused by physical abuse of which lips are the most commonly injured site (54 %), followed by oral mucosa, teeth, gums, and tongue. Complications of certain oral pathologies may be related to abuse for negligence. Bite marks have been associated to sexual abuse combined with oral lesions that appear as a result of sexually transmitted diseases. Parafunctional habits such as dental clenching (bruxism) have been linked to psychological abuse. Purpose: An extensive and detailed literature review of the clinical characteristics and proper handling when providing dental treatment to a child, who is presumably being abused, was carried out. The aim is for a dentist to early detect, document, consult with other professionals, and report cases of child abuse to authorities.
Comparison of Gas Hold-Up Profiles in Co-Current, Counter-Current and Batch Bubble Column Reactors Measured Using Gamma Densitometry and Surface of Revolution Method
Authors: Hernandez-Alvarado Freddy , Kalaga Dinesh V. , Banerjee Sanjoy , Kawaji Masahiro
Published: December 2016

Bubble column reactors are widely used in many industrial processes and can be operated in different modes (co-current, counter-current and batch). However, very little information has been reported on how the hydrodynamics, mixing and mass transfer characteristics vary with respect to different modes of operation. Non-invasive gamma-ray densitometry measurements have been performed to obtain the axial and radial gas hold-up profiles in co-current, counter-current and batch bubble columns. The axisymmetric tomographic reconstruction was performed using the Abel transformation, Schollenberger et al. (1997) and surface revolution methods. The present work presents (1) the effect of superficial gas and liquid velocities on axial and radial gas hold-up profiles, (2) the variation of gas hold-up profiles with respect to three modes of operation, and (3) comparison of available reconstruction methods with a new surface revolution method which does not require a function to fit the chordal values. The counter current operation shows a higher gas hold-up specifically at the center top of the column. The increment in gas hold-up with the increasing superficial gas velocity is higher for batch bubble column operation. The surface of revolution method is shown to be capable of predicting gas hold-up profiles for all three modes of operation.
Numerical Analysis of Particulate Flow Applied to Fluid Loss Control in Fractured Channels
Authors: Barbosa Marcos Vinicius , De Lai Fernando C. , Junqueira Silvio L. M.
Published: December 2016

The aim of this work is to numerically investigate the particulate flow applied to filling fractures in wellbores during the drilling operation. In order to do so, the drill hole is considered in the vertical position and the fracture is defined transversal to the borehole. The wellbore is assumed to be impermeable throughout its entire length, except for the fluid inlet, outlet and the fracture point. The fracture is impermeable so that the fluid loss occurs only at its end. The analysis procedure is divided into two parts: the first one regards to the fluid loss due to the presence of a fracture in a channel (which is treated as a single-phase flow). This is a necessary step to correctly determine the boundary condition at the end of fracture by associating the amount of fluid to be lost according to a specific pressure. In the second part, the fracture filling process with the fluid-solid flow is accomplished as some of the particles carried along the channel flow take the fluid path being eventually lost through the fracture. The fracture filling process is finished when the fluid loss reduction achieves a steady plateau, despite the complete fracture obturation provided by the particles deposition. The particulate flow is numerically modeled via an Eulerian-Lagrangian approach. The Dense Discrete Phase Model (DDPM) deals with the phase coupling; the particle collisions (which happen mainly inside the fracture) are modeled through the Discrete Element Method (DEM). Results are shown in terms of both the historic of the fluid loss and the channel inlet pressure. The influence of geometric (fracture length), particle injection (diameter, concentration and density) and flow parameters (Reynolds number and fluid dynamic viscosity) over the length, height and position of the particle bed formed along the fracture as well the filling time is investigated. A better understanding of the fracture filling process is provided since all sensitivity parameters can alter not only the geometric characteristics of the bed and the steady state fluid loss, but also the time required to finish the process. The Reynolds number increases with the particles bed initial position and due to the higher flow velocity the bed length is increased as well. However, the bed height is reduced and the time required to partially obturate the fracture is raised. For safety issues in the operation during the filling process the increase of Re has shown a smaller pressure buildup in the system. To improve the fluid loss reduction at the end of the filling process, a decrease of Re and an increase of fluid viscosity is required. Such reduction is more dramatic when the diameter and the density of the particles are decreased.
Magnitude and Location of Maximum Erosion in S-Bend With Water-Sand Mixture
Authors: Mazumder Quamrul H. , Zhao Siwen
Published: December 2016

Solid particle erosion is a process that removes material from the inner surface of flow handling devices by repeated impact of entrained particles in the flow. Erosion is a leading cause of unpredicted and premature failure within different industrial equipment such as pumps, pipes, valves and fittings. Understanding the magnitude and location of erosion in the geometry is essential to the prevention of failure. S-bend geometry is used to redirect flows in automotive, chemical processing, oil, and food handling industries. An investigation was conducted using both CFD and experimentation methods to identify the location of maximum erosion. Three different s-bend geometries with 12.7 mm inside diameter and r/D ratios of 1.5, 2.5, and 3.5 were used in the current study. Investigations were performed at three different water velocities each with six different particle sizes ranging from 50 to 300 microns. Due to multiple constraints associated with the test loop, one s-bend geometry was used in the experiment with 12.7 mm inside diameter and an r/D ratio of 1.5. CFD analysis and experimental results showed reasonably good agreement.
Herschel-Bulkley Viscoplastic Flow in Tubes of Non-Circular Cross-Section
Authors: Letelier Mario F. , Siginer Dennis A. , Godoy Felipe , Rosas César
Published: December 2016

Flow of a Herschel-Bulkley (H-B) fluid in tubes of non-circular cross-section in investigated analytically. This study complements results presented in [1] where the equation of motion was solved in tubes of arbitrary cross-section for Bingham type of fluids, and the shapes of plug zones centered on the tube axis and stagnant zones attached to the corners were predicted when the cross-section is triangular and square. In this paper we investigate the effect of the power index in the H-B model on the flow for values greater and lesser than unity, considering thus the shear-thinning and shear-thickening effects, which could not be accounted for with the Bingham model. The equation of motion is solved when the cross-section is an equilateral triangle or a square by means of the shape factor method previously introduced in [2]. Thus, shear-thickening and shear-thinning effects are accounted for and related to the tube geometry in predicting the existence and the extent of undeformed regions in the flow field.
Influence of Fixed Pitch Angle on the Performance of Small Scale H-Darrieus
Authors: Parra-Santos Teresa , Palomar Trullen Diego J. , Gallegos Armando , Uzarraga Cristobal N. , Regidor-Sanchez Maria , Castro Francisco
Published: December 2016

The performance of a Vertical Axis Wind Turbine (VAWT) is numerically analyzed. Influence of fixed pitch angle is studied to get tendencies on the characteristic curves. The set up corresponds with an H-Darrieus with three straight NACA airfoils attached to a vertical shaft. Two-dimensional, transient, Navier Stokes equations are solved with a Third-Order Muscl scheme using SIMPLE to couple pressure and velocity. At least three revolutions must be simulated to get the periodic behaviour. Transition SST turbulence model has been chosen based on literature. Pitch angles of −6° and −10° have been analyzed with Tip Speed Ratios ranging from 0.7 and 1.6. The pitch angle of −10° improves the performance of the wind turbine. Instantaneous and averaged power coefficients as well as detailed flow field around the airfoils are shown.
Flying Fish Sculls to Taxi and Perturbs Wing Lift With Travelling Waves to Land
Authors: Bandyopadhyay Promode R.
Published: December 2016

The top 200 meters of oceans abound in life forms since photosynthesis is possible in that layer. Competition and predator-prey (swordfish-flying fish, 102–104 to 1 mass ratio) interactions are intense here. Chased by predators, a flying fish (FF) — a pleuston — frantically escapes from the water and becomes airborne. Here we report the visual observations of oceanic surface and body distortions of FF to surmise the mechanisms of propulsion during taxiing and landing. FF leaps, not when it is chased, but when the additional energy required for further increase in speed underwater exceeds that required to leap.1 The higher metabolic cost of transport of regular flapping flight in air than in water is circumvented by gliding. We examine the BBCTV video2 by Richard Attenborough, the noted naturalist. An FF may camber its wings like parafoils and may also twist the outer half of the wings during taxiing and climbing. To produce thrust during taxiing, the FF sculls with the lower lobe of the tail fin to produce a reverse Karman vortex jet; there is rapid flicking of the lower lobe of the tail fin tangentially over the surface. The body acts as a chaotic damped and driven pendulum to produce the high-velocity wide flick. To damp after takeoff, it becomes a single asymmetric pendulum. Unpowered (foil) gliding follows. For descent, the wings are shaped, untwisted parafoils and, just prior to touchdown, travelling waves are superimposed, producing, in contrast to taxiing, an impressively smooth small-angle-of-attack tail touchdown on water without any nose-down. The spiked crowns of Richtmyer-Meshkov interface instability are visible on the ocean surface during leaping but not during landing. Trailing hydraulic jumps are observable during landing but not during leaping. The leap is a high-acceleration and Weber number dominated (inertia/capillary forces) phenomenon, but the landing involves little impact force and is dominated by Froude number forces (inertia/gravity forces). The evidence suggests that, prior to leaping and while still underwater, the FF reads the surface wind direction to align the flight path.
Computational Study Comparing Reduced Chemical Mechanisms With the PDF Method in Non-Premixed Flames
Authors: Chen Lu , Battaglia Francine
Published: December 2016

Reactive flow simulations involving turbulence-chemistry interactions can be very challenging because of the strong non-linear coupling between chemistry and fluid dynamics. Furthermore, the chemistry is described with hundreds of reactions, which is prohibitive to solve using computational fluid dynamics (CFD). Using a reduced set of mechanisms that contains a subset of the important species is more practical. However, the species modeled must capture the key combustion characteristics of interest, such as ignition, species distributions and major pollutant formation. Previously, the authors used the joint probability density function (PDF) to study the non-premixed turbulent flames, and continue the work here. New CFD simulations were conducted for a non-premixed turbulent syngas flame using four reduced mechanisms models (3-step, 8-step, 9-step and 12-step reactions) to assess the predictive capabilities in the calculation of turbulence-chemistry interactions. The performance of the different reduced mechanism models was assessed and compared with previous PDF model results and the experimental results of Correa and Gulati (1992, “Measurements and Modeling of a Bluff Body Stabilized Flame,” Combustion and Flame, 89(2)). The predictions of temperature and species from the reduced mechanisms of the 3-step and 8-step were found to have differences as large as 20%. It was also found that the reduced 12-step mechanism was able to represent the strong turbulence-chemistry interactions in the syngas flame and demonstrated good ability of predicting species distribution. Therefore, a simplified chemical mechanism model was successfully developed to simulate the non-premixed syngas flame. The 12-step reduced mechanism will guide other reduced mechanism models for syngas fuels. However, the PDF method still gives the best predictions of temperature and requires the smallest computational time.
Adjoint-Based Aerodynamic Design of Complex Aerospace Configurations
Authors: Nielsen Eric J.
Published: December 2016

An overview of twenty years of adjoint-based aerodynamic design research at NASA Langley Research Center is presented. Adjoint-based algorithms provide a powerful tool for efficient sensitivity analysis of complex large-scale computational fluid dynamics (CFD) simulations. Unlike alternative approaches for which computational expense generally scales with the number of design parameters, adjoint techniques yield sensitivity derivatives of a simulation output with respect to all input parameters at the cost of a single additional simulation. With modern large-scale CFD applications often requiring millions of compute hours for a single analysis, the efficiency afforded by adjoint methods is critical in realizing a computationally tractable design optimization capability for such applications.
Dynamic Performance of Spring-Loaded Pressure Relief Valve for High Temperature and High Pressure Steam
Authors: Yang Liu , Wang Chao , Zhang Jian , Lu Ronghua , Yu Xinhai
Published: December 2016

In this study, the complete dynamic performance of the high temperature and high pressure steam pressure relief valve (HTHP PRV) from pop up to reseating was simulated by CFD software which combined with moving mesh capabilities and multiple domains. An experimental setup was established for the testing of HTHP PRV in accordance with the standard of ASME PTC 25. The dynamic performance of HTHP PRV was recorded accurately. For the transient simulation of HTHP PRV, a domain with opening boundaries connected to the outlet of PRV was proposed to avoid the direct definition of the pressure at the PRV outlet and handle the critical flow. It also can describe the surrounding flow field and help us to understand the influence of the PRV discharge on the environment better. The simulation results were verified by experimental ones. The resultant force on the disk and the lift were monitored and analyzed. A detailed contour of the compressible steam flowing through the HTHP PRV was obtained, including small scale flow features in the back pressure chamber. The effect of the adjusting sleeve on the dynamic performance of HTHP PRV was also investigated in details. The blowdown increases linearly by 0.163% with the adjusting sleeve moves by each millimeter in the direction of departing from the disk. This study sheds a light of understanding of the dynamic characteristics of HTHP PRV.
Optimization of Looped Airfoil Wind Turbine (LAWT™) Design Parameters for Maximum Power Generation
Authors: Song Binhe , Banerjee Subhodeep , Syrovy George , Agarwal Ramesh K.
Published: December 2016

The looped airfoil wind turbine (LAWT™) is a patented new technology by EverLift Wind Tecnology, Inc. for generating power from wind. It takes advantage of the superior lift force of a linearly traveling wing compared to the rotating blades in conventional wind turbine configurations. Compared to horizontal and vertical axis wind turbines, the LAWT™ can be manufactured with minimal cost because it does not require complex gear systems and its blades have a constant profile along their length [1]. These considerations make the LAWT™ economically attractive for small-scale and decentralized power generation in rural areas. Each LAWT™ is estimated to generate power in the range of 10 kW to 1 MW. Due to various advantages, it is meaningful to determine the maximum power generation of a LAWT™ by optimizing the structural layout.

In this study, CFD simulations were conducted using ANSYS Fluent to determine the total lift and drag coefficient for a cascade of airfoils. The k-kl-ω turbulence model was used to account for flow in the laminar-turbulent transition region. Given the lift and drag coefficients and the kinematics of the system, an analytical formula for the power generation of the LAWT™ was developed. General formulas were obtained for the average lift and drag coefficients so that the total power could be predicted for any number of airfoils in LAWT™. The spacing between airfoils was identified as the key design parameter that affected the power generation of the LAWT™. The results show that a marked increase in total power can be achieved if the optimum spacing between the airfoils is used.
The Developments of Axial Flow Pump System Researches in China
Authors: Liu Chao
Published: December 2016

The axial-flow pump system research and technological innovation in China are introduced. The research trend on hydraulic performance of the axial flow pump system are discussed. The applications of axial-flow pump hydraulic model and recent progress are presented. Through inductive characteristics of axial flow pump system, the classification of the system is put forward according to the installation position of the motor namely the shaft extension type axial-flow pump system and the tubular axial-flow pump system. The innovation applying of the different types of axial-flow pump systems in a number of pumping station projects are introduced respectively. From the perspective of technological development and application prospects of axial-flow pump system are analyzed. The limitations of the traditional pump selection method are discussed, and the applicable rationality of a new method of pump selection for the axial-flow pump system, is introduced. The variable angle adjustment formula and applicability based on the test data of axial-flow pump system are introduced. The harmfulness to the pump units from the intake vortex and the safety measures are analyzed. The research results of the vortices in the pump sump and the measures of vortices prevention and elimination are described. As regarding the real and potential problems in research development on axial-flow pump system, the suggestions for further deepen researches are presented.
Study on the Characteristics of Rayleigh-Benard Convection With Viscoelastic Fluids
Authors: Cai Weihua , Ye Qin , Chen Jianping , Zhang Hongna , Wei Tongzhou , Li Feng-chen
Published: December 2016

In order to investigate the viscoelastic effect on classical thermal convective system-Rayleigh-Bénard convection (RBC), this paper uses direct numerical simulation to study the RBC system with viscoelastic fluid. By comparing the instantaneous velocity vector and temperature between Newtonian fluid and viscoelastic fluid cases, it is found that under certain conditions viscoelastic fluid has delayed the generation of RBC. Besides, the addition of viscoelastic fluid can enhance heat transfer based on Nusselt number and the heat transfer mechanism is interpreted based on the thickness of moment and temperature boundary layers.
Small and Full-Scale Modeling for the Application of Wall Solar Chimneys
Authors: Park David , Battaglia Francine
Published: December 2016

A solar chimney is a natural ventilation technique that has a potential to save energy consumption as well as to maintain the air quality in the building. However, studies of buildings are often challenging due to their large sizes. The objective of the current study was to determine relationships between small- and full-scale solar chimney system models. In the current work, computational fluid dynamics (CFD) was utilized to model different building sizes with a solar chimney system, where the computational model was validated with the experimental study of Mathur et al. The window, which controls entrainment of ambient air, was also studied to determine the effects of window position. Correlations for average velocity ratio and non-dimensional temperature were consistent regardless of window position. Buckingham pi theorem was employed to further non-dimensionalize the important variables. Regression analysis was conducted to develop a mathematical model to predict a relationship among all of the variables, where the model agreed well with simulation results with an error of 2.33%. The study demonstrated that the flow and thermal conditions in larger buildings can be predicted from the small-scale model.
Vector Control of Synthetic Jets Using an Asymmetric Slot
Authors: Kobayashi Ryota , Nishibe Koichi , Watabe Yusuke , Sato Kotaro , Yokota Kazuhiko
Published: December 2016

This is a fundamental study on the jet vectoring control by means of adjusting the synthetic jet Strouhal number (frequency) without slot shape change with time in actuators. This work involved introduction of asymmetric slots with various beak lengths in free synthetic jets for various frequencies, experimentally and numerically. Furthermore, the behavior of synthetic jets was compared with that of the continuous jets. In our experiment, velocity measurements for both types of jets were performed using a hot-wire anemometer with an I-type probe and a traverser, and flow visualization for observing the behavior of the jets was performed using the smoke wire method. Through the experiment, typical flow patterns and time-averaged velocity distributions of synthetic jets for various beak lengths and Strouhal number were demonstrated. The time-averaged velocity was measured at a reference point on the slot centerline to evaluate the degree of the bend of the jets and the obtained data was used in the Strouhal number-beak length map.
CFD Simulations of Aerosol Particles Deposition in a Venturi Meter Used in Smoke Sampling Devices
Authors: Melhem Omar A.
Published: December 2016

Smoke sampling devices are used in several fields to study dynamics of smoke aerosols. An important criterion in designing smoke sampling devices is that flow paths leading to where the sample is characterized are constructed such that deposition of aerosol particles along the paths is minimized. Sampling devices often include a Venturi flow meter installed downstream of the smoke source, which may significantly alter the composition of the aerosol reaching the sample analyzer. The current work employs Computational Fluid Dynamics (CFD) to model particle deposition within the flow meter and to examine the effects of different design parameters. This study focuses on particles with sizes ranging from 0.01 to 100 microns, for which three main mechanisms for deposition can be identified: inertial impaction, gravitational sedimentation, and Brownian diffusion. It has been shown that inertial deposition is negligible for ultrafine particles (5–560 nm) and it becomes noticeable for particles in the micron size range. Also, deposition fractions increase with increasing particle sizes. Moreover, inertial particle deposition increases with increasing volume flow rates.
Efficiency of Diffuse and Sharp Interface Strongly Coupled Fluid Structure Interaction Methods in Fixed and Moving Boundaries
Authors: Mohaghegh Fazlolah , Udaykumar H. S.
Published: December 2016

Efficiency of different types of immersed boundary methods in the fluid structure interaction (FSI) analysis is studied for different cases. Two different formulations of smoothed profile method (SPM) [1, 2] as diffuse interface approaches are compared with the ghost fluid method (GFM) [3, 4] as sharp interface method (SIM) [5]. First, the original SPM which has two pressure Poisson equations (SPM2P) is modified to a novel formulation for SPM with only one pressure Poisson equation (SPM1P) and then validated. The efficiency study is performed for SPM1P, SPM2P and SIM. The results show that when the solid object is fixed, the explicit solution of SIM is faster than the two SPMs. However, when the solid is moving and strongly coupled formulations is used, SPM1P will be the fastest method. It is shown that the efficiency of the strongly coupled formulations depends on the number of subiterations required in each time step to reach the converged implicit solution. SPM1P and SPM2P need less number of subiterations in comparison with SIM and they are faster. When the added mass effect is high, the efficiency of SPM becomes more noticeable as the required number of subiterations is significantly less in SPM. Finally, SPM1P is faster than SPM2P in all cases however, the accuracy of SPM2P in predicting the flow pattern is better than SPM1P.
Aerodynamic Load Maps of Bluff-Body Combinations in Incompressible Flow
Authors: Motahari Nicholas , Hiremath Nandeesh , Komerath Narayanan
Published: December 2016

Prior work showed high-resolution maps of aerodynamic load coefficients for various geometric shapes, as well as parametric variations on canonical models. The problem of obtaining predictions on new shapes using generalized interpolations and combinations of canonical shapes, is explored in this paper. Two cases are considered. The first is that of an engine container used as a helicopter slung load. Full scale flight data provide the dynamics, so that the effects of different uncertainties and simplifications are examined. The progression is from interpolated Fourier coefficient data on an approximate, canonical shape, to dynamic simulation at different levels of fidelity. The second case is one of predicting the aerodynamic load map of a complex practical shape — a road vehicle used as a slung load, starting by combining data on canonical shapes. In both cases, this paper presents predictions using approximations; the future work expects to present wind tunnel results on a scale model of the engine container, and on an actual combination of canonical shapes. The cylinder approximation gives a good prediction of the flight test dynamics history and divergence speed. Adding a drag estimate for the tethers achieves good correlation with the flight test trail angle behavior, with some error apparent at the highest speed. However, this error underpredicts drag, which may be the effect of support structure including flat-plate baffles, not yet modeled. In the second case, a weighted combination of Fourier coefficients for a cylinder and a rectangular prism, gives a good representation of the drag and side force coefficient maps for a HumVee model; correlation of the yawing moment is less accurate.
Pressure Fields Around a Rotor Blade in Reverse Flow
Authors: Hiremath Nandeesh , Shukla Dhwanil , Huang Zujia , Komerath Narayanan
Published: December 2016

The flowfield and pressure distribution of a rotor blade in reverse flow is studied using stereoscopic particle image velocimetry. The 2-bladed teetering rotor with rigid NACA0013 untwisted untapered blades, with manually set collective and cyclic pitch, is operated at advance ratios from 0.7 to 1.0. Results are presented from azimuths 240 and 270 degrees, where the velocity field in chordwise sectional planes at two radial stations are analyzed, at two advance ratios. The paper is focused on two aspects. First is calculation of the total circulation around each blade section, and around the strong sharp-edge vortex seen below the blade in these sections. The second is the surface and flowfield pressures derived from the 3-component velocity field obtained from closely-spaced planes, after interpolation to satisfy the mass continuity equation. The pressure extraction technique is being developed using a yawed-cylinder test case, and shows good success in satisfying continuity between data planes.
Elliptical Shape Hole-Pattern Seals Performance Evaluation Using Design of Experiments Technique
Authors: Jin Hanxiang , Untaroiu Alexandrina
Published: December 2016

Hole-pattern annular gas seals have been proven to be very effective in reducing leakage flow between high and low pressure sections in turbomachinery. This type of seal has two distinct flow regions: an annular jet-flow region between the rotor and stator, and cylindrical indentions in the stator that serve as cavities where flow recirculation occurs. As the working fluid enters the cavities and recirculates, its kinetic energy is reduced, resulting in a reduction of leakage flow rate through the seal. The geometry of the cylindrical cavities has a significant effect on the overall performance of a hole-pattern annular gas seal. Previous studies have been primarily focused on cylindrical cavities that are perpendicular to the axis of the seal and have indicated that the performance may be improved by varying the depths, spacing, and diameters of the cavities. However, to date the effects of elliptical cylinder cavities has yet to be investigated. In this study, the effects of elliptical shape hole pattern geometry on the leakage and dynamic response performance of an industry-relevant hole-pattern seal design are investigated using a combination of computational fluid dynamics (CFD), hybrid bulk flow/CFD analysis, and design of experiments techniques. A CFD model of the baseline hole-pattern seal was first developed and validated against experimental data. A design of experiments (DOE) study was then performed to investigate the effect that various elliptical shape cavities had on the leakage rate through the seal. CFD simulations were run for multiple geometry configurations of the cylindrical cavities to evaluate the seal performance at each of the design points. The design space was defined by varying the values of five geometrical characteristics: the major and minor radius of hole, the angle between the major axis and the axis of the seal, the spacing between holes along the seal axis, and hole spacing in the circumferential direction. Quadratic polynomial fitting was then used to analyze the sensitivity of different design variables with respect to the different outputs. This detailed analysis allowed for a greater understanding of the interaction effects from varying all of these design parameters together as opposed to studying them one variable at a time. Response maps generated from the calculated results demonstrate the effects of each design parameter on seal leakage as well as the relationships between the design parameters. The data from this analysis was also used to generate linear regression models that demonstrate how these parameters affect the leakage of the seal. The results of this study could aid in improving future designs of hole-pattern annular gas seals.
A Novel Fix to Reduce the Log-Layer Mismatch in Wall-Modeled Large-Eddy Simulations of Turbulent Channel Flow
Authors: DeLeon Rey , Senocak Inanc
Published: December 2016

The log-layer mismatch arises when a Reynolds-averaged Navier-Stokes (RANS) model is blended with a large-eddy simulation (LES) model in a hybrid fashion. Numerous researchers have tackled this problem by simulating a turbulent channel flow. We show that the log-layer mismatch in hybrid RANS-LES can be reduced substantially by splitting the mean pressure gradient term in the wall-normal direction in a manner that keeps the mass flow rate constant. Additionally, an analysis of the wall-normal variation of the friction velocity shows a constant value is recovered in the resolved LES region different than the value at the wall. Second-order turbulence statistics agree very well with direct numerical simulation (DNS) benchmarks when scaled with the friction velocity extracted from the resolved LES region. In light of our findings, we suggest that the current convention to drive a turbulent periodic channel flow with a uniform mean pressure gradient be revisited in testing eddy-viscosity-based hybrid RANS-LES models as it appears to be the culprit behind the log-layer mismatch.
Computational Analysis of 3D Fin-Fin Interaction in Fish’s Steady Swimming
Authors: Han Pan , Liu Geng , Ren Yan , Dong Haibo
Published: December 2016

Three-dimensional numerical simulations are used to investigate the hydrodynamic performance and the wake patterns of a sunfish in steady swimming. Immersed boundary method for deformable attaching bodies (IBM-DAB) are used to handle complex moving boundaries of one solid body (fish body) attached with several membranes (fins). The effects of the vortices shed from both the dorsal and anal fins on the hydrodynamic performance of the caudal fin are analyzed by prescribing an undulatory swimming kinematics to a full body sunfish model. Results show that both the dorsal fin vortices and the anal fin vortices can increase the thrust and efficiency of the caudal fin comparing to caudal fin only case. This is because the dorsal/anal fin not only can feed vorticity into the caudal fin wake via vortex shedding, but also can modulate the flow in the downstream in a way of forming a jet with stronger backward component.
Electrohydrodynamics (EHD)-Induced Flow in Different Channel Configurations
Authors: Ngo C. C. , Sanghvi M. , Patel J.
Published: December 2016

Electrohydrodynamics (EHD) is the study of flow field induced by an electric field. The concept behind EHD is to transform electrical energy into kinetic energy. The induced kinetic energy can then be utilized for many applications such as chip-integrated cooling, drying in the food industry, reducing drag of aircrafts, spraying of dielectric material for printing, controlling particulate matter emissions as well as EHD thrusters and pumping. The focus of the present study is the use of EHD to induce flow in various channel configurations. The operation principle of an EHD pump is based on the interaction among electrically charged particles inside the dielectric fluid and their migration to the grounded plate. Corona discharge, produced by applied high voltage difference, is an electrical discharge brought on by the ionization of fluid surrounding the electrodes. For the current work, this applied voltage to the electrode is in the order of 10–30 kV generated by a DC power supply while the resulting electric current generated is very small in the order of μA to mA. EHD pumps are becoming more attractive for industrial application nowadays due to the lack of moving parts, simple and compact design with light structural weight as compared to conventional pumps or cooling fans. In addition, there is less operating noise and no vibration during the operation of EHD pumps.

The main focus of our present work is to perform an experimental study to determine the induced flow rate at different applied voltages using various channel and wire electrode configurations. The basic experimental setup consists of an EHD pump test section, a high-voltage power supply, an air velocity transmitter and a data acquisition system. EHD pump test sections with different geometries of channel (e.g., circular, square and rectangular channels with the same cross-sectional area) along with different wire electrode configurations were constructed and tested. Measurements were taken from the corona threshold voltage to the sparkover voltage. The objective of the present study is to evaluate various designs of EHD pumps by comparing the EHD pumping efficiency.
Numerical Analysis of Turbulent Flow Over a Wavy Wall in a Channel
Authors: Martins Segunda Vinicius , Ormiston Scott , Tachie Mark
Published: December 2016

A commercial CFD code (ANSYS CFX, release 16.2) is used to predict the turbulent flow phenomena over a wavy wall. The present work will provide numerical simulations of flow in a channel with a wavy lower wall using a variety of turbulence models available in the CFD commercial code. Eddy viscosity models and Second Moment Closure models were used with wall function available. Those turbulence models had different predictions for the flow field, in which were evaluated: velocity profiles, pressure distribution, wall shear stress, recirculation region and turbulence quantities. A comparison between their predictions will be presented. The validation of results is performed by comparison to experimental data from previous studies and also LES simulations.
Spectral Analysis and Discussion on the Velocity Fluctuation in Drag Reducing Channel Flow by Surfactant Additives
Authors: Kaiho Yuichi , Hara Shumpei , Tsukahara Takahiro , Kawaguchi Yasuo
Published: December 2016

It is known as the Toms effect that the wall friction coefficient is reduced by adding a small amount of polymer or surfactant into a water flow. In the drag-reducing flow, it is expected that a time scale of turbulent velocity fluctuation is changed by relaxation time due to viscoelasticity. In the present study, experimental analysis of the turbulent velocity fluctuation was performed with temporal characteristics in surfactant solution flow. The velocity fluctuations were measured by using a two-component laser Doppler velocimeter system on turbulent channel flow. And then, we performed statistical operation on those data and examined the time scale. From spectra analysis, it was found that very low frequency velocity fluctuations existed near the wall region in the surfactant solution flow. It was also revealed that the strong anisotropy occurred not only with the intensity but also with frequency distribution in turbulent velocity fluctuations. Moreover, the turbulence contributes nothing to the Reynolds shear stress and behaves as a wave motion. It was concluded that the turbulent eddies and viscoelasticity were two factors contributing to turbulent generation in the viscoelastic turbulent flow, with each factor having its own time scale.
Proposal and Verification of Estimation Method for Turbulent Frictional Drag of Irregularly Roughened Surface From the Roughness Curve Measurement
Authors: Gunji Manami , Shoen Taiga , Mieno Hirohisa , Kawaguchi Yasuo
Published: December 2016

The relationship between the pressure drag of a Tayler-Couette flow over rough structures including semi-sphere shaped, conically-shaped and painting irregularly distributed on a wall surface was investigated experimentally. A concentric cylinder device composed of an inner test cylinder and an outer cylinder was employed. The 2-dimensional roughness height of painting surfaces are measured by inline profile measuring instrument, and the roughness curve and the probability density function (PDF) of 2-dimensional roughness height can be obtained at the same time. Then, the 3-dimensional roughness surface can be modeled by the “Set of Multi dispersed Cone Model” which is characterized by the PDF of 2-dimensional peak heights. The PDF of 3-dimensional roughness can be calculated based on bayesian estimation method. After that, the total friction irregular roughness surface can be estimated by summing the contribution of cones composing the SMCM. For the verification of estimation, the estimated value was compared with the measured friction. As a result, it was found that prediction results of five cylinders with sand-grain type roughness by present estimation method agree very well with experiment results, except for one cylinder with relatively smooth and long wave length wavy.
Evaluation of Turbulence Models for the Numerical Study of Reciprocating-Mechanism Driven Heat Loop
Authors: Popoola Olubunmi T. , Bamgbade Ayobami A. , Cao Y.
Published: December 2016

A bellows-type Reciprocating-Mechanism Driven Heat Loops (RMDHL) is a novel heat transfer device that could attain a high heat transfer rate through a reciprocating flow of the working fluid inside the heat transfer device. Although the device has been tested and validated experimentally, analytical or numerical study have not been undertaken to understand its working mechanism and to provide guidance for the device design. In a bid to improve the accuracy of the numerical models of the RMDHL, seven turbulence models for fluid flow have been alternately adapted and implemented in an existing numerical RMDHL model. The obtained results were studied and compared with prior experimental results to gain confidence and select the most suitable turbulence modeling techniques. The Boussinesq approximation has been used and the governing equations have been numerically solved using the CFD solver FLUENT. For the three-dimensional fluid flow, the turbulence models were studied are the Standard, RNG, and Realizable k-ε Models, Standard and SST k-ω Models, Transition k-kL-ω Model and the Transition SST Model. The result of each numerical simulation have been analyzed and ranked using a numerical model calibration template. It was found that the standard k-ω Models provided the least accurate results while the RNG-k-ε Model provided the most accurate predictions. It is expected that the results will help improve the accuracy of the work on the RMDHL modeling.