bluuebunny/crossref_metadata_2025 huggingface dataset:
Karl Pearson—The Scientific Life in a Statistical Age by Theodore M. Porter: A Review
Authors: David Herbert A.
Published: March 2009

Porter presents an excellent account of the young Karl Pearson and his extraordinarily varied activities. These ranged from the Cambridge Mathematical Tripos Exams to German history and folklore, and included free thought, socialism, the woman's question, and the law. Returning to science, Pearson produced the famous Grammar of Science. He decided on a career in statistics only at age 35. Porter emphasizes Pearson's often acrimonious but largely successful battles to show the wide applicability and importance of statistics in many areas of science and public affairs. Eugenics became a passion for Pearson. Avoiding all formulas Porter fails to give any concrete ideas of even Pearson's most important contributions to statistical theory. We try to sketch these here.
National Cholesterol Education Panel ΙΙΙ Guidelines Performance Role in Preventing Myocardial Infarction in a Large Cohort Without a History of Coronary Artery Disease: Korea Acute Myocardial Infarction Registry Study
Authors: Yoon Yeonyee E. , Rivera Juan J. , Kwon Dong‐A , Chae In‐Ho , Jeong Myung‐Ho , Rha Seung‐Woon , Blumenthal Roger S. , Nasir Khurram , Chang Hyuk‐Jae ,   other Korea Acute Myocardial Infarction Registry Investigators
Published: March 2009

The Third Report of the Adult Treatment Panel National Cholesterol Education Program (NCEP‐ATPIII) guidelines are widely used for the primary prevention of a coronary event. These guidelines were developed using experimental data from studies that enrolled mostly Caucasian patients. The pathogenesis of atherosclerosis varies with ethnicity. Given these two circumstances, the authors sought to investigate the performance of the guidelines in a large Asian cohort. The Korea Acute Myocardial Infarction Registry (KAMIR) includes data collected between November 2005 and December 2006 from 41 referral centers in South Korea. A retrospective review of the clinical data was performed. After patients with a history of coronary heart disease (CHD), CHD equivalent, and those taking lipid‐lowering medications were excluded, 2969 individuals (76% men; 61±12 years) were enrolled. The recommendations for lipid‐lowering treatments according to the NCEP‐ATPΙΙΙ were examined in the context of the cohort. A total of 38%, 66%, and 8% of the study participants had hypertension, were smokers, and had a family history of premature CHD, respectively. When patients were stratified by the number of risk factors present and their 10‐year CHD risk, 69% diagnosed with an acute myocardial infarction did not qualify for drug therapy. Irrespective of the age group examined (young, intermediate, and old), the percentage of patients who did not qualify for a lipid‐lowering pharmacologic intervention was higher than 60%. NCEP‐ATPIII underestimates CHD risk in individuals of Asian descent. Further studies are needed to improve primary CHD prevention in this patient population.
The Ecumenical Assembly for Justice, Peace and the Integrity of Creation
Authors: Falcke Heino
Published: March 2009

The Vancouver assembly of the World Council of Churches in 1983, in part through the efforts of Heino Falcke and the delegates from the GDR, called on the WCC “to engage member churches in a conciliar process of mutual commitment to justice, peace and the integrity of creation”. In the GDR, the high point of this conciliar process was an Ecumenical Assembly of Churches and Christians which met in three sessions in 1988 and 1989, and which, not least because of the involvement of peace, environmental and human rights groups, made unprecedented demands for the reform of the GDR and influenced the citizens' movements and political parties formed at the time of the peaceful revolution of autumn 1989. As envisaged at the Vancouver assembly, the conciliar process was intended to link the issue of peace, a priority at that time for many WCC members in the northern hemisphere, with that of global justice, an overriding concern for churches in the South. In the course of preparations for the Ecumenical Assembly in the GDR, however, the discourse of justice was applied to GDR society itself, something that was reflected in the 10,000 proposals from parishes, groups and individuals for the assembly, and in the “testimonies of concern” with which the assembly opened its first session in February 1988. In this article,1 which comes from a conference in Dresden in April 1999 to mark the 10th anniversary of the final session of the Ecumenical Assembly, Falcke reflects on how the assembly changed from being a Christian, church gathering to becoming an emerging opposition within civil society.
Using Frontier Portfolios to Improve Make‐to‐Order Operations
Authors: Yue Jinfeng , Xia Yu , Tran Thuhang , Chen Bintong
Published: March 2009

Make‐to‐order (MTO) manufacturers face a common problem of maintaining a desired service level for delivery at a reasonable cost while dealing with irregular customer orders. This research considers a MTO manufacturer who produces a product consisting of several custom parts to be ordered from multiple suppliers. We develop procedures to allocate orders to each supplier for each custom part and calculate the associated replenishment cost as well as the probability of meeting the delivery date, based on the suppliers' jobs on hand, availability, process speed, and defective rate. For a given delivery due date, a frontier of service level and a replenishment cost frontier are created to provide a range of options to meet customer requirements. This method can be further extended to the case when the delivery due date is not fixed and the manufacturer must “crash” its delivery time to compete for customers.
Helium-Air Exchange Flow Rate Measurement Through a Small Opening
Authors: Fumizawa Motoo , Horiuchi Hidenori
Published: March 2009

Buoyancy-driven counter flows of helium-air were investigated through horizontal and inclined small openings. Counter flows may occur following a window opening as ventilation, fire in the room as well as a pipe rupture accident in a high temperature gas-cooled nuclear reactor [1]. The counter flows also occur following the fusion reactor accident of LOVA that takes place through the breaches of vacuum vessel penetration duct [2]. The experiment has carried out by a test chamber filled with helium and flow was visualized by the smoke wire method. The flow behavior has recorded by a high-speed camera with a computer system. The image of the flow was transferred to the digital data, thus the flow velocity was measured by PTV software. The mass fraction in the test chamber was measured by electronic balance. The detected data was arranged by the densimetric Floude number of the counter flow rate that derived from the dimensional analysis. The method of mass increment was developed and applied to measure the counter flow rate. By removing the cover plate placed on the top of the opening, the counter flow initiated. Air enters the test chamber and the mass of the gas mixture in the test chamber increased. The volumetric counter flow rate was evaluated from the mass increment data. In the case of inclination openings, the results of both methods were compared. The inclination angle for maximum densimetric Floude number decreased with increasing length-to-diameter ratio of the opening. For a horizontal opening, the results from the method of mass increment agreed with those obtained by other authors for a water-brine system.
Visualization of Swirling Flows Using PIV in a Plating Bath
Authors: Umeda Shinzaburo , Shigeyama Shinji , Horii Kiyoshi
Published: March 2009

A uniform plating system useful in a chemical plating industry has been developed. For plating of tubes, uniform plating thickness has been achieved. The demands of a plating industry such as an uniform thickness plating and the gap plating between two parts were crucial. The development of new plating system was based on fluid dynamic control using flip-flop flows. Small swirls produced by flip-flop flows would give thorough mixing of liquid and take away the phenomenon that wakes behind tubes occur. For clarifying these phenomena, the velocity variations in a plating tank were measured using two-dimensional PIV. Basic experiments using flip-flop flows, conventional flows and jet flows were performed.
Fine Atomization and Low Penetration Fuel Spray by Using a Multi-Swirl Nozzle for Automobile Engines
Authors: Yasukawa Yoshihito , Okamoto Yoshio
Published: March 2009

Improving fuel economy and reducing exhaust emissions of automobile engines have become very important. The direct injection gasoline engine has the advantage of reduced fuel consumption, but it also has disadvantages related to exhaust emissions. Weak mixing of fuel with air due to short mixing time and fuel liquid-film adhering to the engine cylinder walls cause emission problems. To reduce these emissions, injectors need to provide fine atomization, low fuel penetration (length of fuel spray), and spray formation control. In this study, we developed a multi-swirl nozzle that forms a thin liquid-film at the nozzle outlet for fine atomization; the thin liquid-film easily breaks up into small droplets. We investigated the fuel spray characteristics of these nozzles experimentally and numerically. Using a long-distance microscope, we found that a liquid-film formed at the nozzle outlet even if its diameter was small. This is an effect of the centrifugal force from the swirl flow. Experimental results also showed that the multi-swirl nozzle reduced the size of coarse droplets (irregular, large droplets) and shortened fuel penetration. We also simulated numerically the fuel flow of the multi-swirl nozzle. Numerical analysis described the swirling flow that the multi-swirl nozzle generated above the nozzle inlet and the thin liquid-film at the nozzle outlet.
Experimental Study on Drag-Reducing Turbulent Boundary Layer Flows of Surfactant Solutions
Authors: Itoh M. , Tamano S. , Inoue T. , Yokota K.
Published: March 2009

In this study, the influence of a drag-reducing surfactant on the turbulent boundary layer under different solution concentrations and temperatures was extensively investigated using a two-component laser-Doppler velocimetry system. It is found that the drag reduction ratio DR at the temperature T = 20°C becomes larger downstream, and decreases with the increase of concentration from C = 65 to 150 ppm. The DR for C = 100 ppm becomes smaller with the increase of the temperature from T = 25 to 35°C, and the DR at T = 20°C is smaller than DR at T = 25°C. For the different solution concentrations and temperatures, the value of the mean velocity scaled by the friction velocity increases with increasing the amount of drag reduction. For the present experimental conditions tested, the peak value of streamwise turbulence intensity seems to be not related to the amount of DR directly and to be affected by the low Reynolds number effect strongly.
CFD Air Flow Channel Optimization for a Low NOx Operation of a Big Steam Boiler
Authors: Prisecaru Tudor I. , Popa Elena , Prisecaru Malina Mihaela
Published: March 2009

One of the Romanian big power plant (Turceni) of 2400 MWe installed power has seven Benson boilers of 1035 t/h each, using Romanian pulverized lignite. Until 2008, every one of them has to be revamped in order to emit less than 500 mg/Nm3 of NOx at full load and 6% oxygen content in the flue gas. The problem has been very complex due to the fact that all these steam boilers have been commissioned since 1968, without any design preparation concerning low NOx emissions. Step by step, all the technological measures have been performed, so the burning process of the Romanian low heat power lignite, has been able to produce low NOx emissions by the help of supplementary stages of air injections. The last problem and the subject of the presented paper, occurred regarding the possibility to inject enough and equal airflow rate through sixteen nozzles before the end of the boiler’s furnace. The complexity of this problem consisted not only in a lot of technical constraints concerning to the starting place of the air pipes, but also to the path of the pipes (with very big dimensions) and to a very low influence in pressure drop losses towards the existent air ducts. A special supplementary problem has been that one to create the simplest shape of the air inlet elbow from the main existent air ducts, in order to suck the strictly necessary airflow rate at the lowest possible pressure drop loss. Due to the fact that the boiler’s dimensions are too big to use only one air pipe toward the nozzles, two air manifolds are considered starting from two main different air ducts and feeding eight nozzles each; this fact has complicated the task further, in order to balance the airflow rate inside the two manifolds. This complex problem has been solved by the help of CFD Fluent code and has been considered also the subject of one of the team member’s PhD dissertation. Special meshing techniques have been used in order to optimize the cells’ number. For CFD results validation a special 1:50 transparent scaled model of the furnace has been constructed and performed using a laser — Doppler anemometer to determine the airflow rate and velocity, inside the air channels and at the nozzles’ exits to the furnace.
The Effects of Splitter Plates on Turbulent Boundary Layer on a Long Flat Plate Near the Trailing Edge
Authors: Jodai Yoshifumi , Takahashi Yoshikazu , Ichimiya Masashi , Osaka Hideo
Published: March 2009

An experimental investigation has been made on a turbulent boundary layer near the trailing edge on a long flat plate. The flow was controlled by an additional splitter plate fitted to the trailing edge along the wake center line. The length of the splitter plate, l, was varied from a half, to five times the trailing edge thickness, h. Measurements of base pressure behind the trailing edge and of mean velocity and pressure distribution in the turbulent boundary layer on the flat plate were made under the freestream zero-pressure gradient. The absolute value of the base pressure coefficient of the long flat plate was considerably smaller than that of the short flat plate without the splitter plate. A significant increase in the base pressure coefficient was achieved with the splitter plate (l / h ≧ 1), fitted to the long flat plate. Within an inner layer in the turbulent boundary layer near the trailing edge, the mean velocity increased more than that in the upstream position in the case without the splitter plate. With the splitter plate, however, the base pressure rise made the mean velocity distribution more closely approach that of a fully-developed turbulent boundary layer.
Pulsating Flow for Mixing Intensification in a Twisted Curved Pipe
Authors: Timite Brahim , Castelain Cathy , Peerhossaini Hassan
Published: March 2009

This work concerns the manipulation of a twisted curved pipe flow for mixing enhancement. Previous work [1,2,3] has shown that geometrical perturbations to a curved pipe flow can increase mixing and heat transfer by chaotic advection. In this work the flow entering the twisted pipe undergoes a pulsatile motion. The flow was studied experimentally and numerically. The numerical study is carried out by CFD code (Fluent 6) in which a pulsated velocity field is imposed as an inlet condition. The experimental setup involves principally a “Scotch-yoke” pulsatile generator and a twisted curved pipe. Laser Doppler velocimetry (LDV) measurements have shown that the Scotch-yoke generator produces pure sinusoidal instantaneous mean velocities with a mean deviation of 3%. Visualizations by laser-induced fluorescence (LIF) and velocity measurements, coupled with the numerical results, have permitted analysis of the evolution of the swirling secondary flow structures that develop along the bends during the pulsation phase. These measurements were made for a range of steady Reynolds number (300 ≤ Rest ≤ 1200), frequency parameter (1 ≤ α = r0.(ω/υ)1/2 < 20), and two velocity components ratios (β = Umax,osc/Ust). We observe satisfactory agreement between the numerical and experimental results. For high β, the secondary flow structure is modified by a Lyne instability and a siphon effect during the deceleration phase. The intensity of the secondary flow decreases as the parameter α increases during the acceleration phase. During the deceleration phase, under the effect of reverse flow, the secondary flow intensity increases with the appearance of Lyne flow. Experimental results also show that pulsating flow through a twisted curved pipe increases mixing over the steady twisted curved pipe. This mixing enhancement increases with β.
Experimental Study on the Stability of the Flow Behind an Accelerating Circular Cylinder
Authors: Inasawa A. , Toda K. , Asai M.
Published: March 2009

Disturbance growth in the wake of a circular cylinder moving at a constant acceleration is examined experimentally. The cylinder is installed on a carriage moving in the still air. The results show that the critical Reynolds number for the onset of the global instability leading to a self-sustained wake oscillation increases with the magnitude of acceleration, while the Strouhal number of the growing disturbance at the critical Reynolds number is not strongly dependent on the magnitude of acceleration. It is also found that with increasing the acceleration, the Ka´rma´n vortex street remains two-dimensional even at the Reynolds numbers around 200 where the three-dimensional instability occurs to lead to the vortex dislocation in the case of cylinder moving at constant velocity or in the case of cylinder wake in the steady oncoming flow.
Purely Meshless Smoothed Particle Hydrodynamics Computations of Taylor Vortex Flows
Authors: Salvans-Tort Josep , Catrakis Haris J.
Published: March 2009

A purely meshless implementation of SPH (Smoothed Particle Hydrodynamics) is investigated to validate the accuracy of SPH as a method for fully meshless computations of Taylor vortex flows, i.e. without the need for any particle re-meshing. The continuity and Navier-Stokes equations together with appropriate initial and boundary conditions, as well as an equation of state, are solved for water using purely meshless SPH, i.e. in which no re-meshing of smoothed particles is employed. The exact analytical unsteady solution is compared with the SPH computational results and good agreement is found. The results show that it is not necessary to employ particle re-meshing, which had previously been claimed to be an essential ingredient for SPH simulations of Taylor vortex flows. In the present purely meshless SPH simulations, regular as well as irregular initial distributions of smoothed particles are investigated with the minimum inter-particle spacing scale and maximum interparticle void scale monitored as functions of time to ensure limited particle clustering, spreading, and void formation. Our results show convergence of the computed solution to the analytical solution, with increasing number of the smoothed particles and with decreasing time step. In our computations, the highest-order derivatives corresponding to the viscous terms are directly computed, i.e. without any artificial viscosity. These findings suggest the utility of this approach as a promising tool for purely meshless SPH direct numerical simulations and large-eddy simulations of turbulent flows.
Active Flow Control of Turbulent Refractive Interfaces in Separated Shear Layers for Laser Beam Propagation
Authors: Zubair Fazlul R. , Catrakis Haris J.
Published: March 2009

The behavior of turbulent refractive interfaces, and means for the optimization of these interfaces, is essential in various basic and applied studies concerning the propagation of optical wavefronts such as laser beam wavefronts through turbulence or optical imaging through turbulence. In this study, the structure of turbulent refractive interfaces and aero-optical interactions along laser beam propagation paths, in unforced and forced separated compressible shear layers, are examined through use of direct imaging and pulsed plasma actuators. Dielectric-barrier discharge (DBD) pulsed plasma actuators are used to excite the flow prior to separation. Our interest is in searching for the frequencies and amplitudes of the forcing that produce direct suppression of the large scale turbulent interfaces and, thereby, direct reduction of the laser wavefront aberrations. Whole-field shadowgraph imaging of pure-air separated shear layers is conducted for control off vs. control on cases at various forcing frequencies, in order to explore the effects of plasma forcing on the large-scale flow behavior. Direct profiling of forced vs. unforced turbulence-aberrated laser wavefronts propagated transversely through shear layers is conducted using high-resolution Shack-Hartmann microlens arrays. Evidence is presented showing significant reduction of the turbulence-induced laser aberrations, for forced vs. unforced shear layers, indicating the presence of a mechanism of suppression, i.e. disorganization, of large-scale organized structures by high-frequency pulsed plasma forcing.
Polymer/Surfactant Effects on Generated Volume and Pressure of CO2 in EOR Technology
Authors: Bakhtiyarov Sayavur I. , Shakhverdiyev Azizaga Kh. , Panakhov Geilani M. , Abbasov Eldar M.
Published: March 2009

Dense phase gases (carbon dioxide, nitrogen, light hydrocarbons, etc.) are used to develop miscibility with crude oil in enhanced oil recovery processes. Due to the certain reasons, carbon dioxide (CO2) flooding is considered the fastest-growing improved oil recovery method. However, due to the low viscosity of dense CO2, displacement front instabilities and a premature CO2 breakthrough is observed in many cases. An alternative scheme to the traditional methods of oil recovery by injection of carbon dioxide gas is the technology developed by the NMT, IGDFF and IMM, which proposes in-situ CO2 generation as a result of the thermochemical reaction between water solutions of the gas-forming (FG) and gas-yielding (GY) chemical agents injected to the productive horizons. This technique excludes CO2 injection from surface communication systems and does not require expensive delivery equipment. This process allows avoiding many negative consequences of CO2 injection technology. Based on the in-situ CO2 generation concept, several new technological schemes were developed in order to provide an integrative effect on the productive horizons. In this paper we present the results of the experimental studies on effect of polymer and surfactant additives on generated CO2 miscibility. The solutions of gas-yielding (GY) agent with different concentrations of surfactants and polymer additives were used as a reacting agent in these laboratory studies. Within the limits of the experimental conditions stochiometric reactions between gas-yielding (GY) and gas-forming (GF) water solutions were simulated. The tests were conducted on the experimental set up designed and built for these purposes. In the first series of experiments a polyacrylamide was added to the gas-yielding (GY) agent in the concentrations 0.1, 0.25 and 0.5 wt.%. A dynamics of the pressure changes during stoichiometric reaction was recorded. It is shown that the pressure of the generated CO2 gas significantly depends on concentration of the polymer additive and, as a consequence, on viscosity of the water solution. It slightly depends on the concentration of the surfactant added to the GY reactant.
Flow Around the Revolving Propeller Blades in Low Reynolds Number Field
Authors: Arai Nobuyuki , Yoshida Hironori , Hiraoka Katsumi
Published: March 2009

By studying the flow around the revolving propeller blades, an improvement of the propulsion efficiency can be found. We made the propeller blade optimized to get good propulsion efficiency by the Adkins & Liebeck’s propeller theory in low Reynolds number field. We call this blade “Prop00”. In order to investigate the flow around the propeller blades, distributions of pressure on the surface of the revolving propeller blade in some pitch angles were measured by wind tunnel testing. For Prop00, it was observed that the contour lines of Cp are dense near the trailing edge of blade’s tip. And it is thought that the separation may exist around the tip of blade. In order to compare the flow characteristics and to get the hint of improvement of the shape of the propeller blades, three different shape types of propeller blades, rectangle, trapezoid, and inverted trapezoid, were made. We call these blades “Prop01”, “Prop02”, and “Prop03”, respectively. According to the pressure distribution, it’s necessary to improve the shape of the propeller which suppresses the effect by a separation to improve the propulsion efficiency more. We took some photographs of tufts on the revolving blades with stroboscope to investigate vectors of the flow on the blade surface. These photographs are taken under identical conditions of the direct pressure measurement. It was observed that tufts tend to bent to the outer side direction by centrifugal force. However, differences on tufts bending were observed in the regions of the leading and the trailing edges at same radius. The tufts at the trailing edge region more bent to the tip of blade than that at leading edge region. Then, it is thought that separation and crossflow on the blade surface exist. We thought that the stability of the flow around the trailing edge is lost by the separation and the boundary layer transition. Furthermore, universal CFD software is used to study the improvement of the propeller performance. By using FLUENT 6 as universal CFD software, the result of CFD was compared with the result of wind tunnel testing.
Numerical Simulation for the Collision of a Vortex Ring With Solid Particles
Authors: Yagami Hisanori , Uchiyama Tomomi
Published: March 2009

This study is concerned with the numerical simulation of the collision between a vortex ring and an ensemble of small glass particles. The vortex ring, convecting with the self-induced velocity in a quiescent air, collides with the particles. The Reynolds number for the vortex ring is 2600, and the particle diameters are 50 and 200μm. Immediately after the collision with the vortex ring, the 50μm particles surround the vortex ring, forming a dome. The 200μm particles disperse more due to the collision with the vortex ring. This is attributable to the centrifugal effect of the large-scale eddy. The collision between the vortex ring and the particles induces an organized three-dimensional vortical structure inside the vortex ring. It also reduces the strength of vortex ring and the convective velocity.
CFD Prediction of Boundary Layer Transition and Separation on an Airfoil at Varying Angle of Attack
Authors: Wolgemuth Nicole M. , Walters D. Keith
Published: March 2009

This study analyzes the predicted flow over a NACA 0012 airfoil at varying angles of attack and three different Reynolds numbers. The ability of three different turbulence models to predict boundary layer separation and transition behavior is investigated. Particular interest is paid to prediction of the separation bubble that develops near the leading edge of the airfoil suction surface prior to stall. The FLUENT CFD solver was used to simulate turbulent airflow over the airfoil. The three turbulence models include the standard and realizable forms of the k-ε model, available in FLUENT, as well as a recently developed transition-sensitive k-ω model that was implemented into the solver using user-defined functions. By employing the new, transition-sensitive model, computed properties of the flow field were found to be closer to experimental data than results produced by utilizing built-in turbulence models. Most importantly, the new, transition-sensitive model predicts the occurrence of the separation bubble, which the other models are unable to predict. The new model also clearly reproduces the laminar, transitional, and turbulent flow that occurs over the airfoil.
A One-Dimensional-Subgrid Based Wall Function for Use With Coarse Near-Wall Meshes
Authors: Fairchilds Landrum , Walters D. Keith
Published: March 2009

A common alternative to full resolution of the near-wall region in computational fluid dynamics (CFD) simulations is the use of wall functions that decrease the mesh requirements in this region. This paper presents an alternative to current wall functions based on numerically approximating a turbulent velocity profile using a one-dimensional subgrid contained within wall-adjacent control volumes (cells). Use of the subgrid allows approximation of boundary layers of varying height relative to the first layer sizing. Most significantly, this includes boundary layers with heights smaller than the first layer cells themselves. Use of the subgrid allows wall adjacent primary grid sizes to vary from low-Re model sizing of y+ ≈ 1 to grid sizes of y+ ∼ 1000 or more without significant loss in accuracy versus fully resolved simulations, and with computational costs similar to currently used wall functions. The development of the new method is presented and results are shown from two demonstration test cases — flow over a flat plate and axial flow over a cylindrical body. The results are compared to low-Re modeling with a very fine near wall mesh, and to currently used wall functions.
A Flexible, Yet Robust Coupled Method for Fluid Structure Interaction
Authors: Zhang Sijun
Published: March 2009

A flexible robust method coupling computational fluid dynamics (CFD) and computational structural dynamics (CSD) is developed for the general applications of aeroelastic analyses. This coupling is achieved through a Multi-Disciplinary Computing Environment (MDICE), which allows several computer codes of ‘modules’ to communicate in a highly efficient fashion. The present approach offers the advantage of utilizing well-established single-disciplinary codes in a multi-disciplinary framework. The flow solver is density-based for modeling compressible, turbulent flow problems using structured and/or unstructured grids. A modal approach is employed for the structural response. The flow and structural solvers are fully coupled via successive iterations within each physical time step. Three aeroelastic cases were analyzed with the proposed method; they are steady flow/modal analysis of an AGARD 445 wing, transient flow/modal analysis of the AGARD 445 wing, and vertical tail buffeting of F/A-18.
Wall Pressure Fluctuations in the Reattachment Region of a Backward Facing Step
Authors: Lee Yu-Tai , Farabee Theodore M. , Blake William K.
Published: March 2009

Steady mean flow fields and turbulent flow characteristics obtained from solving the Reynolds Averaged Navier Stokes (RANS) equations with a k-ε isotropic turbulence model are used to predict the frequency spectrum of wall-pressure fluctuations for flow past a backward facing step. The linear source term (LST) of the governing fluctuating-pressure equation is used in deriving the final double integration formula for the fluctuating wall pressure. The integrand of the solution formula includes the mean-flow velocity gradient, modeled turbulence normal fluctuation, Green’s function and the spectral model for the interplane correlation. An anisotropic distribution of the turbulent kinetic energy is implemented using a function named anisotropic factor. This function represents a ratio of the turbulent normal Reynolds stress to the turbulent kinetic energy and is developed based on an equilibrium turbulent flow or flows with zero streamwise pressure gradient. The spectral correlation model for predicting the wall-pressure fluctuations is obtained through modeling of the streamwise and spanwise wavenumber spectra. The nonlinear source term (NST) in the original fluctuating-pressure equation is considered following the conclusion of Kim’s direct numerical simulation (DNS) study of channel flow. Predictions of frequency spectra for the reattachment flow past a backward facing step (BFS) are investigated to verify the validity of the current modeling. Detailed turbulence features and wall-pressure spectra for the flow in the reattachment region of the BFS are predicted and discussed. DNS and experimental data for BFSs are used to develop and validate these calculations. The prediction results based on different modeling characteristics and flow physics agree with the observed turbulence field.
Numerical Study of Two-Dimensional Co-Flowing Turbulent Jets
Authors: Abdel-Salam Tarek
Published: March 2009

The present study reports numerical analysis of turbulent jets. This study investigates the effect of initial jet velocity on the location of the merging and combining points of two dimensional co-flowing turbulent jets. Flow geometry under consideration is three co-flowing rectangular jets. Effects of inner jet and outer jets exit velocities are investigated. Numerical results are obtained with a finite volume CFD code. Turbulence is treated with a two equation k-e model. Different jet velocities have been examined corresponding to Reynolds numbers of 2,000 to 35,000. Structured grids are used in the present study. Results show that the initial velocity of the inner jet has significant effect on the merging and combining points.
A Supercritical-Fluids Simulator Applied to Flows of Arbitrary Substance in Arbitrary Conditions
Authors: Yamamoto Satoru , Yano Shinichi , Ishigame Akira , Furusawa Takashi
Published: March 2009

The supercritical-fluids simulator developed by our group is applied to the simulation of flows of arbitrary substance in arbitrary conditions. This simulator is based on the preconditioning method coupled with the PROPATH database. Since the database has the set of thermal properties for 48 substances, the present method can be applied to such substances. In this paper, substances such as carbon-dioxide, water, and nitrogen in several pressure and temperature conditions are calculated and the calculated results are compared with each other.
Numerical Simulation of Particle Motion in a Jig Separator
Authors: Asakura Kuniomi , Nagao Minoru , Mizuno Midori , Harada Shusaku
Published: March 2009

The motion of particles in a jig separator is investigated numerically. The motion of particles is expressed by the BBO-type equation. Three-dimensional flow is simulated by the SIMPLE algorithm. The contact forces among particles are calculated by a discrete element method (DEM) extended to particles of different sizes. The results of simulation show that particles with the same settling velocities and different diameters can also be separated. To analyze the motion of particles in the jig, an equation for the response time of a particle that included added mass, gravity, and drag forces is derived.
Velocity and Pressure Measurements of a Mach 0.85 Axisymmetric Jet
Authors: Mann Richa , Ukeiley Lawrence S. , Seiner John M.
Published: March 2009

The turbulent properties of a heated and unheated Mach 0.85 axisymmetric jet have been studied. The velocity field of the jet at static temperature ratios of 0.87 and 2.34, was measured in the streamwise radial plane using Particle Image Velocimetry. The velocity measurements were acquired between streamwise locations of 3D and 8D downstream from the nozzle exit. Proper Orthogonal Decomposition (POD) was applied to the velocity field using snapshot POD. The POD analysis showed that the eigenvalues of the heated jet had higher fraction of energy. The POD eigenfunctions or modes of the streamwise velocity of both jets were similar, while the POD modes of the radial velocity of both jets were very different. The POD modes of radial velocity of the unheated jet were symmetrical about the jet centerline, and the modes of the heated jet seemed to merge at the centerline. The near field pressure measurements were acquired just outside the shearlayer. A linear array of five pressure transducers was placed at 7° to the nozzle lipline, so that it would be parallel to the shear layer. The transducers in the array were spaced one diameter apart. Pressure measurements were acquired at streamwise locations between 4.25D and 10.25D from the nozzle exit. Based on the slope of the pressure spectra, the propagating events in the two jets were identified. The POD was also applied to the pressure data, and the POD modes of the two jets were compared. The peak in the amplitude of the POD mode of the heated jet was at a higher frequency. With increasing mode numbers, the peak in the POD mode of both jets shifted to a downstream location.
Flow Induced Unstable Structure of Liquid Crystalline Polymer Solution in L-Shaped Slit Channels
Authors: Narumi Takatsune , Fukada Jun , Hasegawa Tomiichi
Published: March 2009

An experimental study has been conducted on unstable structures induced in two dimensional slit flows of liquid crystalline polymer solution. 50wt% aqueous solution of hydroxyl-propylcellulose (HPC) was utilized as a test fluid and its flow behavior in L-shaped slit channels with cross section of 1mm height and 16mm width was measured optically. The inner corner of the L-shaped channel was rounded off in order to clarify the influence of the radius of curvature on the unstable behavior. A conversing curved channel was also tested. The flow patterns of HPC solution in the channels were visualized with two crossed polarizers and we observed that typical wavy textures generated in the upstream of the corner almost disappeared after the corner flow. However, an unstable texture was developed again only from the inner corner in downstream flow. The fluctuation of orientation angle and dichroism were also measured with a laser opto-rheometric system and it was found that the unstable behaviors of HPC solution have periodic oscillatory characteristics at a typical frequency. In the inner side flow after the corner, the periodic motion became larger toward the downstream and then higher harmonic oscillations were superimposed. Larger rounding off of the inner corner suppressed the redevelopment of unstable behavior, and it is considered that the rapid re-growth of unstable behavior was caused by rapid deceleration at the corner flow. Moreover, the unstable structure was stabilized with accelerated (elongated) region in the corner flow and the converging channel was helpful to obtain stable structure in the downstream region.
Reconsideration of Cavitation Inception Theory
Authors: Yano Takeru , Fujikawa Shigeo , Yu Tao
Published: March 2009

The nonlinear dynamics of a spherical gas bubble in a liquid water is reconsidered on the basis of the Rayleigh-Plesset equation with particularly emphasis on the unstable behavior with respect to infinitesimal perturbations. The evolution of bubble radius after the discontinuous change of ambient pressure is theoretically analyzed, and the classical critical pressure and critical radius are re-derived as a saddle-node bifurcation point, when the center and saddle on the phase plane merge into a degenerate unstable singular point in the phase plane. Before the saddle-node bifurcation, there is a separatrix issuing from and entering into the saddle point in the inviscid limit. We propose a new criterion for cavitation inception: the ambient pressure that makes the separatrix pass through the initial bubble radius. This criterion gives a cavitation inception pressure higher than the classical one. The effects of viscosity and thermal conductivity are also discussed.
Microscopic Characteristics of Functional Fluid Suspended Diamond Particles Under the High-Voltage Alternating Electric Field
Authors: Obara Hiromichi , Ibata Ryousuke , Kawai Yusuke , Matsudair Yasuaki
Published: March 2009

The microscopic characteristics of a functional fluid for a micro polishing process were investigated by microscopic observation and micro particle image velocimetry. This functional fluid, which consists of suspended micro scale diamond particles in insulated silicon oil, has two specific flow structures under a high-voltage alternating electric field. One flow structure consists of a reciprocating flow generated in one direction between the electrodes under low-electric-field and high-frequency conditions. The other flow structure consists of a rotational flow formed under high-electric-field and low-frequency conditions. These specific flow structures contribute actively to a polishing process and to the development of micro fluidic devices in the future. In the present study, the effect of the electric field on specific flow structures and the mechanism of the induced flow are clarified.
Evaluation of the Influences of Surface Tension on the Bubble Measurement Using a Single-Tip Optical Fiber Probe
Authors: Ozawa Yusuke , Saito Takayuki
Published: March 2009

The optical probe method has been repeatedly improved in order to measure bubbles and droplets efficiently and reliably in gas-liquid two-phase flows, since the application of an optical fiber to measure them was proposed early eighties. However, simultaneous measurement of their diameters and velocities has been thought to need at least two optical fiber probes. To break through this situation, we newly developed a Single-Tip Optical fiber Probe (S-TOP) which realizes simultaneous measurement of diameters and velocities of minute bubbles/droplets. In the S-TOP measurement, the relation between the reflected-light intensity at the wedge-shaped probe tip and the tip-surface area covered with a phase is cleverly used to realize the simultaneous measurement. The surface tension and probe-surface wettability intensively influence the S-TOP signals. The main aim of the present study is to strictly evaluate the influences of surface tension and wettability on the bubble measurement in order to develop precise and reliable S-TOP method. In the present study, we specify the gradient of leading edge (or trailing edge) of the S-TOP signal is proportional to the gas-liquid interface velocity. In the measurement of bubbles and droplets via S-TOP, this relation is effectively utilized. The influences of surface tension and probe-surface wettability on this relation are quantitatively discussed. At surface tension higher than about 50mN/m, the surface tension is dominant. On the other hand, at lower than this value, the wettability is dominant. On the basis of improvement in the consideration of the above results, the authors demonstrate the simultaneous measurement of diameters and velocities of small bubbles with about 200 mm in diameter.
Experimental Study on the Receptivity of Shear Layer Separating at a Rear-Edge of Boundary-Layer Plate
Authors: Asai Masahito , Imai Takeshi
Published: March 2009

Receptivity of the free shear layer developing from a 90-degrees rear-edge of boundary-layer plate to acoustic disturbances is examined experimentally to clarify the dependency of the receptivity coefficient on the rear-edge curvature. The results show that for finite rear-edge curvatures, the receptivity coefficient decreases with increasing the disturbance frequency while it is almost independent of the frequency for the sharp rear-edge over the frequency range examined. The decrease in the receptivity coefficient for the rounded rear-edge is attributed to the fact that the sound-induced Stokes layer which is the vorticity fluctuation developing into the free-shear instability mode is shed into the off-centerline of the separated shear layer.
Characteristics of the Diffuser/Nozzle Valve-Less Micro-Pump
Authors: Tanaka Seiichi , Tsukamoto Hiroshi , Miyazaki Koji
Published: March 2009

In this study we have developed a valve-less micro-pump with one diffuser shaped element and a chamber with a diaphragm; the vibration of which produces an oscillating flow. The pressure-loss in a nozzle is lower than that in a diffuser, and therefore one-way flow is realized in the nozzle direction. The frequency characteristics and the pump characteristics are measured. The maximum total pump head and volumetric flow rate are 0.8 kPa and 2.4 ml/min respectively. The effect of working-fluid viscosity on pump characteristics is also discussed using water and glycerin-water solutions. As a result, the pump performances were found to decrease with increasing fluid viscosity and the pump performance depended on the Reynolds number of oscillating flow. The experimental results are discussed using a simplified model based on the Bernoulli’s theory for unsteady flow in pump.
Parametric Surveys of the Effects of Wake Passing on High Lift LP Turbine Flows Using LES
Authors: Tomikawa K. , Horie H. , Iida M. , Arakawa C. , Ooba Y.
Published: March 2009

In this study, Large Eddy Simulation (LES) was applied to predict the boundary layer development within unsteady wake induced linear turbine cascade of Low Pressure turbine (LPT) blades. In the calculation, unsteady wake was simulated by moving cylindrical bars upstream of the blade. The Multiblock method with a parallel computational algorithm was introduced to use the large computational domain with necessary grid refinement. It was demonstrated that the results were good agreement with experiments, and confirmed that a separation bubble of suction side was suppressed by the incoming wakes. Under the condition of significant effect of compressibility, separation point and reattachment point moved to the rear of the blade. In addition, under the condition of low Reynolds number, loss coefficient showed a tendency depending on Strouhal number.
Movement of Vortices in Flow Field of Supersonic Impinging Jet
Authors: Sakakibara Yoko , Endo Masaki , Iwamoto Junjiro
Published: March 2009

This paper presents a movement of vortices which generate in a flow field of a supersonic impinging jet. The jet is exhausted from a convergent nozzle at nozzle pressure ratio 3.0 and impinges on a flat plate perpendicularly. Using the shadowgraph method, the flow field is visualized and the changes of the jet structure caused by the motion of vortices are examined. In addition, the frequency of such oscillation is measured using schlieren system and the flow field is numerically simulated. Symmetric TVD scheme is applied to solve three dimensional Euler equations. As a results, the free jet under this condition are found to oscillate helically and it is shown that this oscillation mode is related to the motion of vortices moving around the jet and separation bubble which is generated between the plate shock and the plate.
Numerical Study of Interaction Between Natural Convection Flow and Horizontal Wind
Authors: Sakai S. , Watanabe Y.
Published: March 2009

When a large-scale fire, such as a town area fire by an earthquake disaster and forest fire, happens, there can be a fire whirlwind, which is a strong flow including strong flame and sparks. It is sometimes called a firestorm. Fire whirlwind is exposed to high heat, and possesses high heat itself. Therefore, the fire whirlwind is very dangerous. The whirlwind moves and promotes spread of a fire and may enlarge the damage rapidly. Various studies are performed about fire whirlwind, but the property and outbreak mechanism of the whirlwind are not elucidated enough till now. Therefore, in this study, we pay our attention to the flow that is a basic phenomenon of fire whirlwind, and examine the influence that a natural convection gives to outbreak and behavior of fire whirlwind by numerical computation. The numerical analysis performed three-dimensional calculation with analysis software FLUENT6.1. Firstly, a model of the fire domain is constructed. The model is referred from an example of large-scale fire at the Great Kanto Earthquake (1923 in Japan), and natural convection is observed for different heat flux. Then, it is analyzed in a similar model whether a whirlwind occurs or not, after natural convection is fully-developed with changing velocity of the air flow from the side. Furthermore, it is analyzed in a model in which a fire occurs at random whether a whirlwind occurs or not after natural convection is fully-developed with changing velocity of the air flow from the side. As a result of analysis, a whirlwind occurs. The whirlwind sometimes moves and extinct. Then, the influence that a natural convection gives outbreak of the whirlwind is evaluated with changing heat flux and velocity of wind.