bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Simulation of Flow Development Downstream Four Perforated Plates for Flow Measurement Accuracy
Authors: Laribi Boualem , Ait Amrane Abdellaziz , Hadj-Abdellah Abdellah 
Published: December 2014

Several plates are described in the standard like a flow conditioners. A numerical simulation is done to study the development of the turbulent flow with the presence of four perforated plates. Three of the perforated plates are described in the standard ISO 5167 namely ZANKER, NOVA and NEL plates. The fourth one is a new design and proposed plate. The main goal is a comparative simulation of the four perforated plates to produce the fully developed pipe flow which is a prerequisite for flow measurement accuracy. The flow is analysed in a circular pipe of 100mm diameter.
The disturber used for the simulation is a 90° double bend in two perpendicular planes. The geometry of the perforated plates is different with four types of perforations at different diameters. The flow is insured by air at a Reynolds number of 2.5×105.
The numerical analysis is conducted by the CFD code Fluent which is based on the resolution of the Navier-Stokes equations with k-ε like turbulence model. The parameter discussed in this study is the velocity.
The results show the effectiveness of perforated plates to obtain the fully developed pipe flow at length z/D=20 downstream the disturbers. Downstream this station the contour seems to reach the fully developed pipe flow like at station z/D=100 where the flow is supposed fully developed, and don’t exhibit any instabilities of the velocity contour. Contrary, in the stations upstream we found instability of the flow structure. From some stations we show how much the turbulent mixing downstream the perforated plates is important to reach the fully developed pipe flow. The effectiveness of CFD code Fluent to predict flow development in different installations is done where good predictions are presented.
Heat Transfer Enhancement in Channels With Natural Convection Flow by Kármán Vortex Streets
Authors: Mathis Paul , Herpers Matthias , Müller Dirk 
Published: December 2014

In this study, a new method of enhancing heat transfer in heated channels with purely natural convection flow is presented. Blunt bodies which serve as vortex promoters are introduced into the channel, leading to Kármán vortex streets. Vortex shedding behind cylinders and other blunt bodies leads to a convective mixing of the flow, bringing cooler fluid from the center of the channel to the heated walls. Consequently, the temperature gradient is increased and by that the heat transfer.
The purpose of this work is investigating a parameter field in order to identify optimal geometrical parameters for maximizing heat transfer in heated vertical channels. This is done without adding any active mechanical devices for forced convection, but instead by passive means only, meaning cylinders in particular.
A parameter study comprising geometrical degrees of freedom like diameter and position of the vortex promoting bodies and different wall temperatures is performed numerically, indicating a heat transfer enhancement of up to 47.4% compared to the reference case without vortex promoters. The CFD results are compared to heat delivery measurements and visualization data.
CFD Modeling for Optimizing the Fluid Dynamics Patterns of Refractory Lining Drying Process in a Vertical Lime Kiln
Authors: Cristea Eugen-Dan , Sarandrea Luca , Galbiati Massimo 
Published: December 2014

This paper presents a 3D Computational Fluid Dynamics (CFD) modeling of flow, combustion and heat transfer processes into an internal enclosure acting as a combustion chamber, confined by the newly patented air cooled “corner ring”, the lower shaft vertical side walls, the vault and the limestone packed bed, located in a vertical twin-shaft regenerative lime kiln. The numerical simulation is restricted only to the kiln first start-up preliminary phase, with the goal to optimize the thermo-fluid dynamics patterns established during the first heat-up of wet gunning refractory concrete lining of the air cooled “corner ring”, to avoid refractory damages.
The present work is performed in the frame of the commercial general-purpose code ANSYS-CFX R14.5. The CFD model is run under transient flow conditions accomplished by the drying burners operated in single-stage “on-off” control mode, to fit at the best the heat-up curve by optimization of the fluid dynamics patterns, with the goal to prevent local hot spots on the refractory lining. The industrial data collected through the supervision system and the local provisional instrumentation on the vertical twin-shaft regenerative lime kiln, model RD15, commissioned in India on September last year, are used to set the test-case and to partially validate the numerical simulation results.
This CFD numerical simulation represents an useful engineering tool, on behalf of refractory designer and commissioning engineer, for the prediction of the refractory lining behavior during the kiln first start-up.
Large-Eddy Simulation of Reactive Pollutant Dispersion Over Street Canyons of Different Aspect Ratios
Authors: Du T. Z. , Liu Chun-Ho , Zhao Y. B. 
Published: December 2014

In urban areas, pollutants are emitted from vehicles then disperse from the ground level to the downstream urban canopy layer (UCL) under the effect of the prevailing wind. For a hypothetical urban area in the form of idealized street canyons, the building-height-to-street-width (aspect) ratio (AR) changes the ground roughness which in turn leads to different turbulent airflow features. Turbulence is considered an important factor for the removal of reactive pollutants by means of dispersion/dilution and chemical reactions.
Three values of aspect ratio, covering most flow scenarios of urban street canyons, are employed in this study. The pollutant dispersion and reaction are calculated using large-eddy simulation (LES) with chemical reactions. Turbulence timescale and reaction timescale at every single point of the UCL domain are calculated to examine the pollutant removal. The characteristic mechanism of reactive pollutant dispersion over street canyons will be reported in the conference.
Numerical Study of Turbulent Convective in Upward Flows of Supercritical Water in the Triangular Lattice Fuel Rod Bundle
Authors: Modirshanechi Mohsen , Hooman Kamel , Abdi Iman Ashtiani , Forooghi Pourya 
Published: December 2014

Convection heat transfer in upward flows of supercritical water in triangular tight fuel rod bundles is numerically investigated by using the commercial CFD code, ANSYS Fluent© 14.5.
The fuel rod with an inner diameter of 7.6 mm and the pitch-to-diameter ratio (P/D) of 1.14 is studied for mass flux ranging between 550 and 1050 kg/m2s and heat flux of 560 kW/m2 at pressures of 25 MPa.
V2F eddy viscosity turbulence model is used and, to isolate the effect of buoyancy, constant values are used for thermo-physical properties with Boussinesq approximation for the density variation with temperature in the momentum equations. The computed Nusselt number normalized by that of the same Reynolds number with no buoyancy against the buoyancy parameter proposed by Jackson and Hall’s criterion. Mentioned results are compared with V2F turbulence model whereas strong nonmonotonic variation of the thermo-physical properties as function of temperature have been applied to the commercial CFD code using user defined function (UDF) technique.
A significant decrease in Nusselt number was observed in the range of 10-6<Grq/Reb3.425Prb0.8<5×10-6 before entering a serious heat transfer deterioration regime. Based on an analysis of the shear-stress distribution in the turbulent boundary layer and the significant variation of the specific heat across the turbulent boundary layer, it is found that the same mechanism that leads to impairment of turbulence production in concentric annular pipes is present in triangular lattice fuel rod bundles at supercritical pressure.
Numerical Study on Hydraulic Performances of Pump as Turbine With Forward-Curved Blades
Authors: Wang Tao , Kong Fanyu , Yang Sunsheng , Fu Yanxia 
Published: December 2014

A reserved running centrifugal pump can work as a hydraulic turbine with its wide application in industrial energy recovery and the development of micro-hydraulic power. In order to improve the efficiency from the point of turbine working condition, the impeller with forward-curved blades was designed and the hydraulic performances were further analyzed based on the commercial software ANSYS CFX 12.0 in this study. Moreover, to improve the computational accuracy of numerical simulations on turbines, the grid number, the turbulence model, the circumferential flow distribution in the clearance between the volute and the impeller as well as the grid distribution in the boundary layer were considered.
According grid independency analysis, the 1.2 million grids’ number was assumed for numerical simulations. Considering the consuming time and computational stability, as well as the accuracy of the CFD calculation, the k–ε turbulence model was chosen for further calculations. The shaft power and the efficiency of the turbine were more close to the experimental data as the whole computational flow domain in the clearance between the volute and the impeller was connected on the impeller domain. Compared with the performance curves with or without grids in the boundary layer, the boundary layer with grids used in the PAT during numerical simulations was more close to the experimental one.
Compared with the experimental data, the H-Q curves of the hydraulic performances of the turbine with forward-curved blades predicted by CFD were positioned under the experimental one. With respect to the efficiency of the turbine, the various ranges of the efficiency is less than 5%, even there is some deviations between the CFD and experimental results. Therefore, the good agreement of the hydraulic performances between CFD and experimental results in present study indicates that the proposed numerical methods can adequately capture the internal flow in a hydraulic turbine with forward-curved blades, and can also provide a reliable reference for the design of hydraulic turbines.
The Effect of Viscosity Ratio on the Hydrodynamics of Separation From an Oil-Coated Particle
Authors: Mehrabian Sasan , Abbaspour Nima , Bussmann Markus , Acosta Edgar 
Published: December 2014

Separating oil from solid particles is of great importance in many industrial processes including the extraction of bitumen from oil sands, and the remediation of oil spills. The usual approach is to separate the oil from the solid by introducing another liquid (e.g. water). Separation is often assisted by fluid mixing, and chemical addition. Yet while oil-water-particle separation has been well studied from a chemical standpoint, little research has taken into account the effect of hydrodynamics on separation. In this work, the separation of oil from a single oil-coated spherical particle falling through an aqueous solution was evaluated as a function of viscosity ratio. Solvents were used to modify the viscosity of the oil. The experiments were recorded using a high-speed camera and post-processed using the MATLAB image-processing toolbox. A CFD model has also been developed to study this phenomenon.
The results indicate that when viscous forces are strong enough, the oil film deforms, flows to the back of the sphere, and forms a tail that eventually breaks up into a series of droplets due to a capillary wave instability. When the viscosity ratio is small (i.e. the oil is less viscous than the solution), a thin tail forms quickly, the growth rate of the instability is high, and hence the tail breaks very quickly into smaller droplets. When the viscosity ratio is high (i.e. the oil is more viscous), more time is required for the deformation/separation to initiate, and the tail is thicker and breaks more slowly into larger droplets. It was observed that when the viscosity ratio is close to 1, the rate of separation is increased and maximum separation is achieved.
Multi-Scale Simulations of Climate-Change Influence on Chicago Heat Island
Authors: Conry Patrick , Fernando H. J. S. , Leo L. S. , Sharma Ashish , Potosnak Mark , Hellmann Jessica 
Published: December 2014

Over the past half century, burgeoning urban areas such as Chicago have experienced elevated anthropogenic-induced alteration of local climates within urbanized regions. As a result, urban heat island (UHI) effect in these areas has intensified. Global climate change can further modulate UHI’s negative effects on human welfare and energy conservation. Various numerical models exist to understand, monitor, and predict UHI and its ramifications, but none can resolve all the relevant physical phenomena that span a wide range of scales. To this end, we have applied a comprehensive multi-scale approach to study UHI of Chicago.
The coupling of global, mesoscale, and micro-scale models has allowed for dynamical downscaling from global to regional to city and finally to neighborhood scales. The output of the Community Climate System Model (CCSM5), a general circulation model (GCM), provides future climate scenario, and its coupling with Weather Research and Forecasting (WRF) model enables studies on mesoscale behavior at urban scales. The output from the WRF model at 0.333 km resolution is used to drive a micro-scale model, ENVI-met. Through this coupling the bane of obtaining reliable initial and boundary conditions for the micro-scale model from limited available observational records has been aptly remedied. It was found that the performance of ENVI-met improves when WRF output, rather than observational data, is supplied for initial conditions. The success of the downscaling procedure allowed reasonable application of micro-scale model to future climate scenario provided by CCSM5 and WRF models. The fine (2 m) resolution of ENVI-met enables the study of two key effects of UHI at micro-scale: decreased pedestrian comfort and increased building-scale energy consumption. ENVI-met model’s explicit treatment of key processes that underpin urban microclimate makes it captivating for pedestrian comfort analysis. Building energy, however, is not modeled by ENVI-met so we have developed a simplified building energy model to estimate future cooling needs.
Direct Numerical Simulation of Compressible Flow Past a Low Pressure Turbine Blade at High Incidence
Authors: Ranjan Rajesh , Deshpande S. M. , Narasimha Roddam 
Published: December 2014

A direct numerical simulation (DNS) code has been developed to solve the compressible Navier-Stokes equations. This code is capable of handling unstructured grids, often a requirement for simulating flow past complex geometrical shapes like turbine and compressor blade passages. The code is validated for a compressible turbulent channel flow.
Flow past a low pressure (LP) turbine blade passage is computed at Re = 51,831 based on axial chord length and incoming velocity, and angle of incidence = 45.5° with respect to axial chord. Several interesting fluid-dynamical phenomena including multiple separation bubbles and laminar-turbulent-laminar transition cycles are noticed on the suction side of the blade. Also a strong curvature effect is seen in the boundary layer near the leading edge on the suction side, where use of higher order boundary layer theory will be needed.
Direct Numerical Simulation and Linear Stability Analysis of the Flow in a Pebble Bed
Authors: Ward P. , Hassan Y. , Merzari E. , Fischer P. 
Published: December 2014

The flow in a tightly packed array of spheres is important to various engineering fields. In nuclear engineering applications, for instance, researchers have proposed core geometries of the pebble bed reactor (PBR) type cooled by gas or molten salt. Proper core cooling, both at operation and during accident conditions, is a key issue that must be addressed in any reactor design; and the limited amount of data available for the complicated geometry of PBR cores makes this task even more complex. A detailed understanding of coolant flow patterns and properties must be developed in order to meet safety requirements and ensure core longevity.
We address this issue by using the spectral-element computational fluid dynamics code Nek5000, developed at Argonne National Laboratory, to conduct both large eddy simulation (LES) and direct numerical simulation (DNS) of fluid flow through a single face-centered cubic sphere lattice with periodic boundary conditions. Moreover, a statistical analysis of the flow field and a global linear stability analysis of the laminar flow were performed in order to investigate the mechanism of laminar-turbulent transition in this geometry. One of the main objectives of the present study is, in fact, to determine how the Reynolds number affects the development of asymmetries within the flow patterns.
Study on Pressure Fluctuation and Fluctuation Reduction of a Micro Vortex Pump
Authors: Zhang Feixi , Wu Peng , Wu Dazhuan 
Published: December 2014

With the increasing demand of small-flow and high-head pumps, vortex pump, which can be used in industry, agriculture, medical and aerospace etc., has become more and more popular as low specific pump. However, the pressure fluctuation of fluid in the vortex pump would cause flow noise and vibration which may result in damage to the equipment. Clearly, it is important to reduce the fluctuation causing by fluid flow as much as possible.
This study examined and discussed the law of pressure fluctuation in a micro vortex pump by the method of numerical simulation. In addition, a random distribution method was applied to design two new impellers with different blade spacing. Moreover, the influence on pressure fluctuation of different blade positions was predicted by theoretical analysis and CFD analysis.
The results show that the blade passing frequency is dominative in the pressure fluctuation. Although the average static pressure distribution on the circumference of the micro vortex pump increased gradually along inlet to outlet, the pressure pulse amplitudes were fluctuant and the maximum amplitude area was close to the stripper. Affected by the vortex motion in the pump, there were clutters in the spectrum from inlet to outlet even for the vortex pump with uniform circumferential blade spacing. The study also indicated that uneven circumferential spacing would yield additional frequency in the spectrum compared with even one and reduce the magnitude of the dominant frequency without decreasing the performance of the pump sharply.
Based on the consequence, this paper proves the feasibility of applying uneven blade spacing to reduce pressure fluctuation in a vortex pump. And it could be meaningful for the noise and vibration reduction as well as development of vortex pumps.
Review of Expander Selection for Small-Scale Organic Rankine Cycle
Authors: Saghlatoun Saeedeh , Zhuge Weilin , Zhang Yangjun 
Published: December 2014

After more than twenty years working on the selection of an appropriate expander for Organic Rankine cycles and wide research and attentions about its influence on the performance and total cost of waste heat recovery systems, now there is a good-enough background studies and achievement for large scale applications. But small-scale industries is like a art space to modify and revise the previous results.
As it is clearly known, in small-scale applications and industries especially in internal combustion engines, besides the investigation of performance, physical properties and final efficiency of expander, other parameters should be analyzed accurately like manufacturing cost, availability, reliability, sensitivity to operating condition fluctuations.
Due to a significant role of expander equipment to enhance the efficiency of ORC system in the first step expanders is investigated.
In this paper, as per related operating characteristics, a complete comparison of small-scale expanders will be debated to guide designers to select more appropriate and the best efficient expansion machine as per their requirements. According to available literatures there is more need to do research about different types of expanders with various operating conditions in small-scale industries.
Multi-Scale Near-Wall Averaging and Two-Phase Logarithmic Law for a CFD Two-Fluid Model
Authors: Vaidheeswaran Avinash , Buchanan John R. , Guilbert Paul , Lopez de Bertodano Martin 
Published: December 2014

A considerable amount of work has been done in the past to improve the solution methodology using the two-fluid model in the near-wall region. This includes the works of Larrateguy et al. [1], and Moraga et al. [2], based on a multi-scale bubble-center averaging technique. However one shortcoming is that the primitive variables must be recovered from the bubble-center averaged variables. This makes it difficult to implement it in a commercial CFD code. The current research focuses on an engineering approach to overcome this issue. A multi-scale near-wall averaging technique is proposed which separates the effects of bubble dynamics from its geometry in this region.
In addition, the averaged volume fraction profile makes the CFD approach consistent with the modified logarithmic law of Marie et al. [3]. A step function volume fraction distribution was assumed in the near-wall region while developing the theory. However, the volume fraction prediction obtained from CFD calculations is not uniform in this region. The proposed near-wall averaging technique resolves this issue and makes the CFD implementation of the modified wall function approach consistent with the theory of Marie et al. [3].
Managing Knowledge and Information by Students
Authors: Świgoń Marzena , Weber Karsten 
Published: December 2014

The concept of Personal Knowledge and Information Management (PKIM) is based, among others, on two theories: Personal Information Management (PTM) and Personal Knowledge Management (PKM), which hitherto were both subjects of separate studies. Moreover, the concept of PKIM is related to IL, which is a concept of information skills and competences of individuals — a person who manages knowledge has to be information literate. Some of the empirical studies results in the field of PKIM, started in Poland and recently continued in Germany, are presented. As the research method an unstructured questionnaire with open questions was used. Given the results of the survey as well as taking into account the subject literature, the concepts of PIM, PKM, and Information Literacy (IL) seem to be compatible and connected with each other. Our respondents perceive Knowledge and Information as well as knowledge management (KM) and information management (IM) in the context of learning and studying as integrated areas of interests. Although they do see differences between them, interconnections and relations seem more important. Furthermore, KM and IM are recognized as tools of coping with information overload. All aspects that have repercussions on KM and IM are related to three categories: personal characteristics, environment (macro and micro environment), and knowledge and information sources.