bluuebunny/crossref_metadata_2025 huggingface dataset:
Relations Between Design Activities and Interactional Characteristics in Novice-Expert Design Consultations: ‘What’ is Done ‘How’
Authors: Deken Fleur , Kleinsmann Maaike S. , Aurisicchio Marco , Bracewell Rob B. , Lauche Kristina
Published: July 2010

This study investigated processes in novice–expert consultation meetings in an organizational context to identify ‘what’ is done ‘how’ by novices and expert in consultation discourses. A conceptual model was developed for studying novice–expert design discourses at a fine-resolution level. An empirical study was performed at Rolls-Royce Aerospace Engineering. In total 7 audio-records were captured of meetings between trainees (novices) and expert designers, which occurred over the course of 3 trainee teams’ design projects. Relations were investigated between two coding schemes, namely the activity coding scheme and the conversational flow coding scheme. It was found that certain activities in the meeting were more often performed by either novices or experts, whereas other activities were more often performed collaboratively. Based on the results, implications for design engineering practitioners were derived and suggestions for further research are provided.
The Design and Testing of a Low-Cost, Globally-Manufacturable, Multi-Speed Mobility Aid Designed for Use on Varied Terrain in Developing and Developed Countries
Authors: Winter Amos G. , Bollini Mario A. , DeLatte Danielle H. , O’Hanley Harrison F. , Scolnik Natasha K.
Published: July 2010

Mobility aids that are currently available in developing countries do not fully meet users’ needs. People require a device that is maneuverable within the home and that can travel long distances on rough roads. To address this problem, we have designed the Leveraged Freedom Chair (LFC), a wheelchair-based mobility aid capable of navigating virtually any terrain by optimally utilizing upper body power for propulsion through a variable-speed lever drivetrain. The lever system achieves a 4:1 change in mechanical advantage, equating to leverage that ranges from 0.42X to 1.65X a standard wheelchair hand rim. In comparative trials, the LFC demonstrated capabilities that far exceed those of any mobility aid currently available in the developing world; it was able to cruise on smooth surfaces at 2m/s (5mph), climb muddy, grassy hills with a 1:3 slope, and navigate terrain with a coefficient of rolling resistance as high as 0.48. This operational flexibility should make the LFC usable on any terrain, from rural walking paths to tight indoor confines, and greatly increase the mobility of people with disabilities in developing countries. The LFC may also be attractive to wheelchair users in developed countries, as its performance breadth exceeds that of currently available products.
Valuable Theoretical Lessons Learned From the Application of Metamodels to a Variety of Industrial Problems
Authors: Wang Liping , Beeson Don
Published: July 2010

Metamodeling techniques are now being widely used by many industries to replace complex and expensive simulation models so that optimization and probabilistic design studies can be done in a more practical and affordable way. Due to the complexity of many engineering design systems and to the lack of a deep understanding of the metamodeling methods by engineers, many questions related to metamodeling accuracy, confidence, robustness, efficiency, etc. are now frequently asked. The need to establish comprehensive guidelines for engineers to correctly and efficiently apply metamodeling methods to their optimization and probabilistic design tasks is becoming more and more important. Based upon experiences and lessons learned at General Electric in recent years, this paper discusses important metamodeling mathematical details and addresses several common issues engineers are likely to encounter when applying metamodeling techniques to realistic engineering problems. The paper provides detailed guidelines on the best practices of metamodel creation and its application to the design process. Many results from benchmark examples and real applications are included to justify certain guidelines and rules of thumb.
A Perspective for Evaluating Wikis as a Medium for Communication Within Engineering Design Teams
Authors: Walthall Carolynn J. , Devanathan Srikanth , Kisselburgh Lorraine , Ramani Karthik , Hirleman E. Daniel , Yang Maria C.
Published: July 2010

Wikis, freely editable collections of web pages, are showing potential for a flexible documentation and communication tool for collaborative design tasks. They also provide a medium that can be further transformed by properly understanding both the need for flexibility as well as support for design thinking early in the design process. The purpose of this work is to analyze the different dimensions of the wiki from a communication perspective as applicable to design. With a focus on communication in design, we will explore the advantages and disadvantages of using wikis in student engineering design teams. Our ultimate goal is to better support the design process while exploiting the potential for increasing the shared understanding among teams using a wiki. By introducing a wiki in a globally distributed product development course, students gain hands-on experience in using wikis as a design tool. Feedback from students will be collected through questionnaires and used to improve and transform the wiki as a support tool for communication during early design collaboration.
The Canonical Form of All Planar Linkage Topologies
Authors: Shai Offer
Published: July 2010

The current paper shows that all the planar linkages can be constructed from given components called, Assur Graphs, which can be ordered in a table with infinite numbers of rows and columns. In the paper we term this order the canonical form of the planar linkages. This canonical form is proved to be an ordered hierarchy of several levels, enabling systematic generation of all its members. The work has originated from the concept of Assur groups, long known in the field of kinematics, and used to decompose any linkage into basic kinematical atoms. In this paper we introduce a systematic procedure for generating all Assur groups thus finding all the topologies of plane linkages. The work in 2D is based upon known but new mathematical theorems which prove it to be complete and sound. The paper also indicates how this work can be extended into 3D linkages. The mathematical foundation of this work contains several new theorems that have been published by the rigidity theory community during the past six years.
Nano-Scale Impact Dynamics of Ultra-Thin Bonded Layers
Authors: Teodorescu Mircea , Theodossiades Stephanos , Rahnejat Homer
Published: July 2010

The paper highlights the complex issues involved in impact dynamics at nano-scale, prevalent in MEMS. The role of protective layers on the silicon substrate is investigated. It is found that the expected viscoelastic behavior of these layers is not activated due to the very short (almost instantaneous) impact times.
A Model for Product Development Performance Monitoring Based on Analytic Network Process
Authors: Akman Gu¨ls¸en , Okudan Gu¨l E.
Published: July 2010

A well-designed performance measurement system can assess the impact of product development on the whole company. To this end, a set of suitable product development measures can provide valuable information for managing the activities and continuous improvement of the product development process. In this paper, via our literature review, we first establish the gaps with regards to the product development performance measurement. Then, we identify performance criteria for assessing product development process effectiveness based on competitive priorities (cost, quality, flexibility, delivery and innovation) followed by an ANP analysis to develop a model for Product Development Performance Monitoring (PDPM). Finally, using a two tier survey setting, the validity and reliability of the PDPM model are ascertained, and field data for its usage as an assessment tool for product development is demonstrated. The field study was conducted by participation of a sample of manufacturing companies in Turkey.
Support for the Use of Hierarchical Temporal Memory Systems in Automated Design Evaluation: A First Experiment
Authors: Hartung Josh , McCormack Jay , Jacobus Frank
Published: July 2010

Computational synthesis tools that automatically generate solutions to design problems are not widely used in industry despite many years of research. This deficiency can be attributed to the lack of value that these tools provide for the user in terms of time saved in design or quality improvements in the design. In order to provide sufficient quality of solution, it is proposed that more human-like evaluation of solution quality is needed including qualitative concepts, the ability to allow for anecdotal input, and general inclusion of ambiguous information. A hierarchical temporal memory system (HTM) is proposed as a viable approach for capturing design quality from exemplars and subsequently recognizing the presence of that quality in other designs. This paper includes a first experiment in using HTMs for learning and recognizing quality in the form of the visual style characteristics of Hepplewhite, Stickley, and Greene & Greene chair backs. Results show that HTMs develop a similar storage of quality to humans and are therefore a promising option for capturing and recognizing multi-modal quality information in future design automation projects.
Interactive Design Navigational Tools
Authors: Oberoi Sharad , Finger Susan
Published: July 2010

For both student and professional design teams, the design and development process requires that collaborators build and retain knowledge through discussions, creating documents and sharing artifacts. Key to supporting these knowledge building activities is the development of an infrastructure that supports effective knowledge management. This paper presents the framework for an information management technology called DesignWebs, which assimilates the product structures from the evolving set of documents and discussions about an engineering artifact. A DesignWeb enables users to see evolving connections between concepts by using a navigable web-based interface that synthesizes the design knowledge from multiple sources of information.
Framing Sustainability in Human-Centered Product Design
Authors: Oehlberg Lora A. , Agogino Alice M. , Beckman Sara L.
Published: July 2010

Engineers today have access to a myriad of tools for developing sustainable products that have minimal environmental impact. Although consumer interest in sustainability is increasing, it is still not foremost on the minds of many consumers. Engineers are thus faced with the dilemma of developing sustainable solutions for consumers who may not yet want or be able to articulate sustainability needs. We explore this issue by examining user research conducted by students in a graduate-level product design course. We present findings on how users define and describe sustainability, how sustainability needs interact with other user needs, and what tradeoffs people make and feelings people have when faced with sustainability trade-offs. We present a case study of one design team’s findings about sustainability, and how those findings affected the formulation of the team’s mission statement and product strategy. Based on these results, we propose recommendations for how to facilitate the design of innovative and sustainable consumer products.
Management of Transitioning Teams During Design Projects
Authors: Vargas Hernandez Noe , Rangel Jose G. Davila , Delgado Angel E.
Published: July 2010

The objective of this paper is to provide ideas on how to better manage a team transition in a design project. Team transitions can be planned or can occur unexpectedly, in either case, disruption can be diminished by taking the appropriate measures. We present an approach on team transitioning and relate it to our experience with undergraduate senior design teams working on a collaborative project that lasts 1 year while the course is limited to 1 semester. Our observations and recommendations include where to start, damage containment measures, how to retrieve the project’s knowledge, what to look for in a replacement team, and how to improve the odds in the event of an unexpected transition.
Optimal Motion Planning of Manipulators With Elastic Links and Joints in Generalized Point-to-Point Task
Authors: Rahimi H. N. , Korayem M. H. , Nikoobin A.
Published: July 2010

Finding optimal trajectory is critical in several applications for robots from payload transport between two given states in a prescribed time such that a cost functional is minimized. This paper is concerned with the path planning of flexible robotic arms in point-to-point motion, based on indirect solution of optimal control problem. Dynamic modelling technique based on the combined Euler–Lagrange formulation and assumed modes method is applied, then by implementing the Pontryagin’s minimum principle; necessary conditions for optimality are derived. Nonlinear states and control constraints are treated without any simplifications or transforming them into sequences of systems with linear equations. By these means, the modelling of the complete optimal control problem and the accompanying boundary value problem is automated to a great extent. Finally, the performance of method is illustrated through the computer simulations.
OPAS: Ontology Processing for Assisted Synthesis of Conceptual Design Solutions
Authors: Christophe Franc¸ois , Sell Raivo , Bernard Alain , Coatane´a Eric
Published: July 2010

This article focuses on a key phase of the conceptual design, the synthesis of structural concepts of solution. Several authors have described this phase of Engineering Design. The Function-Behavior-Structure (FBS) is one of these models. This study is based on the combined use of a modified version of Gero’s FBS model and the latest developments of modeling languages for systems engineering. System Modeling Language (SysML) is a general-purpose graphical modeling language for specifying, analyzing, designing, and verifying complex systems. Our development shows how SysML types of diagrams match with our updated vision of the FBS model of conceptual design. The objective of this paper is to present the possibility to use artificial intelligence tools as members of the design team for supporting the synthesis process. The common point of expert systems developed during last decades for the synthesis of conceptual solutions is that their knowledge bases were application dependent. Latest research in the field of Ontology showed the possibility to build knowledge representations in a reusable and shareable manner. This allows the construction of knowledge representation for engineering in a more generic manner and dynamic mapping of the ontology layers. We present here how processing on ontology allows the synthesis of conceptual solutions.
Product Architecture Definition and Analysis Using Matrix-Based Multiple-Domain Approaches
Authors: Deubzer Frank , Lindemann Udo
Published: July 2010

Design Synthesis is most commonly supported by creativity methods based on functional product representations. As the design of a new product is in most cases following a predecessor, designers do not start from scratch. The mentioned circumstances enable the support of design synthesis by application of design rules or grammars. The use of rules by automated algorithms allows for the systematical derivation of variations of a product. Algorithms are meant to enable innovative solutions by recommending a great variety of variants to give the designers new impulses for product design. As a downside, the rules for the algorithms have to be described in advance, and thus are inheriting known components and functional structures. The identification of potentials and constraints for improvement of a product’s architecture requires detailed analysis. New solutions are often depending on novelties on different levels of abstraction (for example system, subsystem or component level). Algorithmic procedures usually are not able to allow for this comprehensive task. Thus, automatized mechanisms can only deliver limited innovative solutions. Common methods for the definition of innovative solutions, such as functional modeling methods, the TRIZ methodology, or the Morphological Matrix require accompanying analysis and the fixation onto one level of detail as well. To solve this dilemma, we propose an approach combining powerful analysis methods, required for the identification of potentials and constraints within product architectures on the one hand and the systematic definition of new solutions by systematic and partially automatized methods on the other hand. Exhaustive literature research has pointed out several methods, whose application can benefit a comprehensive approach. Amongst them is the definition of functional models, design synthesis by automatized system definition as well as the analysis of product architectures by the use of Design Structure Matrix and Multiple-Domain Matrix Approaches. The proposed approach should allow for the support of radical innovations by considering the overall product structure. Goal of the approach is the consideration of different levels of detail and the analysis of a comprehensive solution space compared to the definition of discrete solutions delivered by common methods. As a result, the approach is applied to different products on different levels of detail and the publication points out the potential and outcome: the systematic definition of a comprehensive solution space, new solutions as a result of comparison and evaluation of the solution space, the widening of the solution space, and a comprehensive evaluation of results.
Three-Dimensional Simulation of Turbulent Gas-Solid Flow and Heat Transfer in a Pipe
Authors: Mansoori Z. , Dadashi A. , Saffar-Avval M. , Behzad F. , Ahmadi G.
Published: July 2010

Three-dimensional simulation of turbulent gas-solid flow with heat transfer for a vertical pipe is performed in this study and the results are presented. The approach is based on an Eulerian/Lagrangian four-way interaction formulation considering turbulent hydrodynamic and thermal intensities and time scales equations. Inter-particles and particle-wall interactions are accounted for with an inelastic collision model. Numerical model validation is performed for an upward pipe gas-solid flow with constant wall heat transfer.
Effects of Negatively Sloped Jet Inclination Angle and Other Parameters on Air Curtain Performance
Authors: Traboulsi Samir R. , Hammoud Ali H. , Khalil M. Farid
Published: July 2010

Tilted air jet planes are used as barriers between two environments of different temperature, humidity and quality. Entrainment of one environment fluid (air) into the curtain by shear layer mixing contributes to both the sensible and the latent heat load on the other environment and the impingement of the air curtain formed. Perturbation of one side affects the shape of the air jet and might endanger its integrity. Protrusion present in the direction of the flow impacts the performance of the air curtain and defeats its purpose of existence. Computational Fluid Dynamics (CFD) – Fluent 6.3.26® method is used to evaluate the performance of the air curtain formed by negatively sloped tilted jet plane and is also validated by comparing the CFD calculations results with experimental results. Qualitative design combination of various parameters and various levels of obstruction in the direction of the flow(s) are proposed to achieve optimal performance of the air curtain.
Investigation of Closed Valve Operation Using Computational Fluid Dynamics
Authors: Dyson G. , Teixeira J.
Published: July 2010

Predicting the head of a centrifugal pump operating at closed valve remains a difficult task. The nature of the flow regime and the influence of geometric features on this flow is uncertain. In this paper both the flow regime and the influence on that regime by geometry is investigated using a commercially available CFD RANS code. A CFD methodology is presented that takes account of the difficult boundary conditions. This methodology is then used to present the flow regime in a volute pump against the background of available research. The theory of solid body rotation, as a major influence on the closed valve head, is shown by the CFD simulations to be analogous to but not representative of the actual flow regime. The nature of the flow is impulsive and unsteady with fluid interchange occurring between the pump collector and the impeller vane passages. At the inlet the pump impeller experiences a strong steady outflow from the impeller blade tip. This spiralling flow must be accommodated within the computational solution. The impeller outlet is filled with a vortex driven by the flow which cannot be accommodated within the stalled stator passageways. The annular gap between the impeller and collector is filled with a pulsating flow whose frequency is determined by the number of vanes within the impeller. Model validation was carried out by reference to experimental papers and time averaged closed valve head values obtained under standard performance testing.
Thermal Chaotic Mixing in a Two Rod Mixer With Imposed Heat Flux
Authors: Le Guer Yves , El Omari Kamal
Published: July 2010

We investigate the mixing and heat transfer enhancement in a two rod mixer for a highly viscous fluid. The mixer is composed of two circular rods maintained vertically in a cylindrical tank. The rods and tank can rotate around their revolution axis. Chaotic flows are obtained by imposing temporal modulations of the rotational wall velocities. The fluid is incompressible, Newtonian and the thermophysical properties, at first approximation, are kept constant with temperature. We study the effect of different stirring protocols and flow configurations leading to chaotic flows on the efficiency of mixing and heat transfer for the particular wall boundary condition of constant heat flux (i.e. Neumann condition). For this purpose we use different statistical indicators as tools to characterize the mean value of fluid temperature and its homogenization. The results show a significant enhancement of heat transfer for the case of an alternated stirring protocol (a result we have already obtained for the constant wall temperature boundary condition [1]).
Advancing Suction Performance in Hydrocarbon Liquids
Authors: Kaupert Kevin A. , Kamio Keijun
Published: July 2010

Details are presented on design investigations to advance the suction performance of inducers combined with centrifugal impellers for pumping liquid hydrocarbons such as liquefied natural gas (LNG). In particular minimizing the NPSHr3 is emphasized over the entire flow range. Design advances are made with the combined efforts of computational fluid dynamics, analytical methods, and test results. In particular the focus here is on inducer flow incidence and resulting blade loading by examining the NPSHr3 performance of the variable pitch and constant pitch helical style inducers for use over the full flow rate range taken as 35% to 130% of the pump BEP. Results indicate the combined centrifugal impeller with a variable pitch inducer tends to have lower NPSHr3 at BEP and below the pump BEP flow rate, but the constant pitch inducer can have superior performance near the pump maximum flow rate.
Modeling of the Film Drainage Effect on Colliding Particle Statistics in Dilute Turbulent Gas-Solid Flows
Authors: Fede P. , Simonin O.
Published: July 2010

The general purpose of this paper is the modeling of particle-turbulence interaction and particle-particle collisions taking place in dilute gas-solid flows. Direct numerical simulation of a homogeneous isotropic turbulence coupled with discrete particle simulation have been carried out with a model taking into account the effect of the film drainage between colliding particles. The results show that, depending on the particle Stokes number, the particle kinetic energy is strongly modified by the fluid drainage effect. In the frame of the joint fluid-particle approach, taking into account the correlations induced by the turbulence on the colliding velocities, a model has been derived and compared with the DNS results.
Effect of the Section Area of Volute in Low Specific Speed Centrifugal Pumps on Hydraulic Performance
Authors: Zhang Xiang , Wang Yang , Fu Jianhui , Dai Cui , Wang Caihong
Published: July 2010

The volute of low specific speed centrifugal pumps has a great impact on the performance of the pump in that the highest efficiency can only be achieved when the impeller is matched with a well-designed volute. At off-BEP conditions, the performance of pumps declines as a consequence of a mismatch between characteristics of the impeller and the volute. The section area is the most important factor of volute. Numerical simulations and experimental researches have been carried out on the routine-designed impeller and the non-overloading designed impeller (different impeller outlet blade angle between two types of impellers) in the hope of finding out the effect of the section area of volute on low specific speed centrifugal pumps. It has been found that the uneven flow rate on different volute sections caused by the backflow between volute and impeller is one of the reasons for the efficiency decline of pumps at off-BEP conditions, especially in the low flow rate condition. It has also been found that the routine-designed impeller is more easily affected by the section area of volute than non-overloading designed impeller.
Hydrodynamic Investigations of a Dielectrophoretically Trapped and Agitated Microparticle
Authors: Williams Stuart J. , Wereley Steven T.
Published: July 2010

Understanding the fluid dynamics of a particle in suspension is important for a complete investigation of many hydrodynamic phenomena, including microfluidic models. Dielectrophoresis (DEP) is a technique that can translate and trap particles through induced polarization when in the presence of non-uniform electric fields. Here, DEP has been used to capture and suspend a single 10.1 μm diameter spherical particle in a microfluidic channel. Procedures and results for controlled, oscillatory dielectrophoretic agitation of the suspended particle are shown. Hydrodynamic investigations are discussed including the incorporation of micron-resolution particle image velocimetry (μPIV).
Direct Numerical Simulations of Colliding Particles Suspended in Homogeneous Isotropic Turbulence
Authors: Ernst M. , Sommerfeld M.
Published: July 2010

Direct numerical simulations of particle-laden homogeneous isotropic turbulence are performed to characterize the collision rate as a function of different particle properties. The fluid behaviour is computed using a three-dimensional Lattice Boltzmann Method including a spectral forcing scheme to generate the turbulence field. Under assumption of mass points, the transport of spherical particles is modelled in a Lagrangian frame of reference. In the simulations the influence of the particle phase on the fluid flow is neglected. The detection and performance of inelastic interparticle collisions are based on a deterministic collision model. Different studies with monodisperse particles are considered. According to the executed simulations, particles with small Stokes number possess a collision rate similar to the prediction of Saffman and Turner [1], whereas particles with larger Stokes numbers behave similarly to the theory of Abrahamson [2].
Flow in Cavities With Curved Boundaries
Authors: Ovando Guillermo E. , Prince Juan C. , Ovando Sandy L.
Published: July 2010

Fluid dynamics for a Newtonian fluid in the absence of body forces in a two-dimensional cavity with top and bottom curved walls was studied numerically. The vertical walls are fixed and the curved walls are in motion. The Navier-Stokes equations were solved using the finite element method combined with the operator splitting scheme. We analyzed the behaviour of the velocity fields, the vorticity fields and the velocity profiles of the fluid inside the cavity. The analysis was carried out for two different Reynolds numbers of 50 and 500 with two ratios (R = 1, −1) of the top to the bottom curved lid speed. For these values of parameters the flow is characterized by vortex formation inside the cavity. The spatial symmetry on the flow patterns are also investigated. We found that when the velocities of the top and bottom walls have opposite direction only one cell is formed in the central part of the cavity; however when the velocities of the top and bottom walls have the same direction the vortex formation inside the cavity is more complex.
Three-Dimensional Numerical Simulation of Electro-Wetting on Dielectric
Authors: Wang Ze , Wang Wei , Sun Yuanyuan
Published: July 2010

We investigate three-dimensional flows for electro-wetting on dielectric by numerically solving Navier-Stokes equation with Level set function. The level set method is used to compute the surface pressure of droplet. The droplet is divided into three zones. One is acted by the electric field, the other is affected by the electric field and the third is not affected by electric field. The voltage influence can be extended to the droplet surface effectively by handling pressure boundary, which was proved to plays an important role in numerical simulation.
Structure and Pressure Drop in Particle-Laden Gas Flow Through a Pipe Bend: A Numerical Analysis by the Euler/Lagrange Approach
Authors: Lai´n S. , Sommerfeld M.
Published: July 2010

The structure of particle-laden gas flows in a horizontal-to-vertical elbow is investigated numerically for analysing the required modelling depth. The numerical computations are performed with the fully coupled Euler-Lagrange approach considering all the relevant forces: drag, gravity-buoyancy and lift forces (slip-shear and slip-rotational). Moreover, interparticle and particle-rough wall collisions are taken into account by means of stochastic approaches. The effect of the different mechanisms, i.e. wall roughness, inter-particle collisions and mass loading, on the flow structure in the bend and the resulting pressure drop are investigated.
Modeling of Gas-Liquid Flow Through an Interconnected Channel Matrix
Authors: Crandall Dustin , Ahmadi Goodarz , Smith Duane H.
Published: July 2010

The motion of a less viscous, non-wetting gas into a liquid-saturated porous medium is known as drainage. Drainage is an important process in environmental applications, such as enhanced oil recovery and geologic CO2 sequestration. Understanding what conditions will increase the volume of gas that can saturate an initially water-saturated porous medium is of importance for predictions of the total CO2 volume that can be sequestered in known geologic formations. To further the understanding of how drainage flow properties are related to different injection flow-rates, a porous medium consisting of interconnected channels and pores was manufactured to perform bench-top experiments of drainage. Additionally, a finite-volume model of this interconnected channel matrix was constructed. Numerical simulations of constant-rate injection into the model porous medium are first shown to compare favorably to the bench-top experiments. The fluid and injection properties of the drainage process were then varied to evaluate the flow conditions which would maximize the volume of gas trapped within the porous medium. In particular, CO2 displacing brine within the porous medium was modeled, with representative subsurface temperatures and fluid properties. It was shown with these fluid conditions a higher final saturation of the invading less-viscous CO2 was obtained, as compared to air into water experiments at similar injection rates.
Numerical Simulation and Flow Field Measurement of High Efficiency Axial-Flow Pump
Authors: Zhang De-sheng , Shi Wei-dong , Chen Bin , Guan Xing-fan
Published: July 2010

In order to analyze the flow characteristics of a high efficiency axial-flow pump, the behavior of the flow in an adjustable axial-flow pump bas been analyzed by numerical simulations of the entire stage based on Fluent software. The prediction data shows agreement with the experimental results. Numerical results show that the static pressure on pressure side of rotor blades increases slightly at radial direction, and remains almost constant in circumferential direction at design conditions, while it increases gradually from inlet to exit on suction side along the flow direction. The static pressure, total pressure and velocity at inlet, rotor blade exit and stator outlet were measured by five-hole probe. The experimental results show, inlet flow is almost axial and the prerotation is very small at design conditions. The meridional velocity and circulation distributions are almost uniform at rotor blades exit at design condition. The residual circulation still exists at downstream of stator, and the absolute flow angle at radial direction is almost consistent at design conditions, but Cu increases linearly from hub to tip at small flow rate conditions. To determine the influence of the hub leakage, a contrast experiment was accomplished. The measurement results show that hub leakage results in the decrease of efficiency, and the meridional velocity and circulation at rotor blade exit, especially near hub leakage region are influenced by the leakage.
Optically Induced Electrohydrodynamics and Electrokinetic Colloidal Aggregation
Authors: Williams Stuart J. , Kumar Aloke , Wereley Steven T.
Published: July 2010

Recently, we have demonstrated a novel optically induced AC electrokinetic technique that rapidly, continuously and selectively concentrates micro and nanoparticles on an electrode surface [1–3]. This is demonstrated with a highly focused near-infrared (1,064 nm) laser beam applied to parallel plate electrodes separated by 50 μm without the need for photosensitive materials. This dynamic optically-induced technique can be applied towards a variety of lab-on-a-chip applications. This paper will explain the fundamental physical mechanisms involved, necessary in order to replicate and implement this technique. This dynamic fluid and particle manipulation technique may prove valuable to a variety of applications in micro- and nanotechnology.
Liquid-Solid Flows Above Deposit in Pipe: Prediction of Hydraulic Gradient and Deposit Thickness
Authors: Matousˇek Va´clav , Krupicˇka Jan
Published: July 2010

A predictive model for the pressure drop in a slurry flow above a stationary bed was presented at the last Liquid-Solid Flow Symposium in 2007. Since then the model has been further refined and validated using experimental data from the tests performed at the Institute of Hydrodynamics ASCR and from the literature. The new version of the model enables to choose a set of appropriate equations in order to predict the hydraulic gradient (the frictional pressure drop) and the thickness of the stationary bed for pipe flows of various average velocities of slurry and delivered concentrations of solids. The paper describes the structure and components of the model and discusses model predictive abilities by comparing model predictions with the new experimental data gained for slurries of two different fractions of sand (respectively fine to medium and medium sands) at various velocities and solids concentrations in a 100-mm pipe.
A Simplified Particle-Turbulence Interaction PDF Model: Application to Deposition Modelling in Turbulent Boundary Layer
Authors: Aguinaga Sylvain , Simonin Olivier , Bore´e Jacques , Herbert Vincent
Published: July 2010

This paper presents a new PDF model for turbulent fluid-particles interactions in the near wall region. Such models have already been presented by Swailes & Reeks [1] or more recently by Van Dijk & Swailes [2]. The PDF approach allows calculating directly the spatial evolution of the wall normal particles velocity distribution. As shown by Swailes & Reeks [1] this approach as many advantages. First, all the statistical moments used (concentration, mean velocity, fluctuating velocities) are contained in the PDF. Thus all the equations for those moments are coupled together within the PDF equation. Second, the boundary conditions can be easily specified, even for the most complex cases as partial absorption. The present study proposes to simplify the fluid particle interaction term of the PDF equation with a new closure model. This simplification is inspired by the BGK models. The paper presents first the model and its numerical implementation. It is evaluated in a wall bounded homogenous turbulence as described by Swailes & Reeks [1]. The results of the present model are then compared to those obtained by Swailes & Reeks [1]. The model is also applied to a channel flow boundary layer configuration. Those simulations illustrate the mechanisms responsible for particles dispersion in the boundary layer turbulence.
Active Flow Control for Reduction of Fluctuating Aerodynamic Forces of a Blunt Trailing Edge Airfoil
Authors: Naghib Lahouti Arash , Hangan Horia
Published: July 2010

Vortex shedding from the base of two dimensional bluff bodies is accompanied by three dimensional wake instabilities. These instabilities manifest as streamwise and vertical vorticity components which occur at a certain spanwise wavelength. The spanwise wavelength of the instabilities (λz) depends on several parameters, including profile geometry and Reynolds number. The present study aims to determine λz for a blunt trailing edge airfoil, which is comprised of an elliptical leading edge, followed by a rectangular section. Results of numerical simulations of flow around the airfoil at Re(d) = 500, 800, 1200, and 17,000, and flow visualization at Re(d) = 2200 indicate that λz has an average value of 2.2d. An active flow control mechanism based on the three dimensional wake instabilities is proposed, to attenuate the fluctuating aerodynamic forces of the airfoil. The mechanism is comprised of trailing edge injection ports distributed across the span, with a spacing equal to λz. Injection of a secondary flow leads to excitation of the three dimensional instabilities and disorganization of the von Ka´rma´n vortex street. Numerical simulations at Re(d) = 500 and 17,000 indicate that the flow control mechanism can attenuate the fluctuating aerodynamic forces significantly, and reduce mean drag using a relatively small injection mass flow rate.
Passive Flow Control of a Flat Plate With Trailing Edge Spanwise Sinusoidal Perturbation
Authors: Doddipatla Lakshmana Sampat , Hangan Horia , Durgesh Vibhav , Naughton Jonathan W.
Published: July 2010

The effect of Spanwise Sinusoidal Perturbation (SSP) control method on blunt trailing edge profiled body is studied using simultaneous pressure and Particle Image Velocimetry (PIV) measurements at different vertical and horizontal locations to study the changes in the streamwise and spanwise vortices. Proper Orthogonal Decomposition (POD) is then used to identify changes in the near wake structure associated with coherent energy redistribution due to control. Integral properties such as the base drag and strength of the vortex shedding decrease compared to the base case. The SSP also redistributes the relative energy among different modes, enhancing the streamwise vortices and suppressing the von Karman Benard rolls as a result.
Experimental Characterization of Flow Induced Vibration in Fully Developed Turbulent Pipe Flow
Authors: Thompson Andrew S. , Maynes Daniel , Shurtz Thomas , Blotter Jonathan D.
Published: July 2010

In this paper we present results of an experimental investigation that characterizes the wall vibration of a pipe with a fully-developed turbulent flow passing through it. Experiments were conducted in a water flow loop where the influences of average fluid speed, pipe diameter, pipe wall thickness, and pipe material on the overall pipe vibration were investigated. The pipe vibration was characterized by accelerometer instruments mounted on the surface of the pipe at multiple locations and the rms of the pipe wall acceleration, velocity, and displacement were measured. Simultaneous measurements of the local temporal fluctuations in the wall pressure were also obtained. Specifically, experiments were conducted in test sections of internal diameters of 3.81 cm – 10.16 cm, pipe wall thickness to diameter ratio ranging from 0.06 – 0.10, and with PVC, aluminum, and stainless steel pipe materials. The experiments were conducted with average fluid speeds ranging from 0 – 11.5 m/s with an accompanying range in the dynamic pressure from 0 – 1 atm. The results show that the rms of the acceleration is proportional to the average fluid speed raised to the 2.12 power. Also, the rms of the pipe surface velocity and the pipe displacement scale with the average fluid speed to the 1.62 and 1.16 powers respectively. Further, the rms of the pipe acceleration and pipe speed increase with increasing pipe diameter, while the pipe modulus of elasticity appears to exert negligible influence on the magnitude of the measured vibrations. The rms of the wall pressure fluctuations scale with the fluid speed raised to the 2.0 power.
Labyrinth Seal Discharge Coefficient for Rectangular Cavities
Authors: Suryanarayanan Saikishan , Morrison Gerald L.
Published: July 2010

A labyrinth seal leakage prediction equation can be developed by considering the seal as a series of orifices and cavities. CFD simulations are used to investigate the discharge coefficient’s dependence of each tooth upon the seal geometry and flow conditions for multi-toothed, teeth on stator, straight through labyrinth seals with rectangular cavities. The discharge coefficient for the first tooth of the labyrinth seal was found to be a function of tooth width to clearance ratio and Reynolds number. It was found that the ratio of the discharge coefficients of a downstream tooth of the labyrinth seal to that of the inlet tooth is a function of the carry over coefficient. The carry over coefficient is a measure of the amount of kinetic energy entering a cavity that is dissipated by turbulence in the cavity. It was observed that the expansion factor (compressibility effect) is a function of tooth pressure ratio. The models developed in this paper for discharge coefficient and expansion factor coupled with the carry over coefficient model presented in our earlier work provide a leakage prediction algorithm that is validated against prior experiments.
Parallel Flow in Ordered Fibrous Structures: An Analytical Approach
Authors: Tamayol A. , Bahrami M.
Published: July 2010

In this study, fully-developed flow parallel to ordered fibrous structures is investigated analytically. The considered fibrous media are made up of inline (square), staggered, and hexagonal arrays of cylinders. Starting from the general solution of Poisson’s equation, compact analytical solutions are proposed for both velocity distribution and permeability of the considered structures. In addition, independent numerical simulations are performed for the considered patterns over the entire range of porosity and the results are compared with the proposed solutions. The developed models are successfully verified through comparison with existing experimental data, collected by others, and the present numerical results over a wide range of porosity. The results show that for the ordered arrangements with high porosity, the parallel permeability is independent of the microstructure geometry; on the other hand, for lower porosities the hexagonal arrays results in lower pressure drop, as expected.
Numerical Analysis of Airfoil NACA0015 and Centrifugal Pump’s Cavitation Characteristic Based on the Thermodynamic Effects
Authors: Liu Demin , Liu Shuhong , Wu Yulin , Xu Hongyuan
Published: July 2010

Cavitation is not only driven by the pressure difference, but also affected by the temperature difference. In high temperature water or cryogenic fluids, temperature decline of liquids is caused by latent heat of vaporization. The cavitation characteristics in this conditions are different from that of room temperature. The thermodynamic effects of cavitation have very important application in the fluid machine, so high temperature and low temperature cavitation are comprehensively applied at the astronautics. The presented paper researched thermodynamics cavitation based on the Rayleigh-Plesset equation and deduced a new thermodynamics cavitation model with fully considering thermodynamic effects on the basic transport equation. The airfoil NACA0015 was calculated by the new model and the thermal cavitation characteristic was calculated at different temperature, that is, 25°C, 50°C and 100°C. Besides, the pressure coefficient was contrasted with experiment data at different temperature. The centrifugal pump’s suction performance curve was calculated at 25°C and 100°C respectively, and the main conclusion is that the suction performance of the pump at the high temperature is better than that at the normal temperature. The thermodynamic effects of cavitation model are more accurate at predicated centrifugal pump’s suction performance, which can provide beneficial referenced indicator for energy conservation.
Flow in Slowly Varying Microchannels of Rectangular Cross-Section
Authors: Akbari Mohsen , Sinton David , Bahrami Majid
Published: July 2010

Laminar fully developed flow in streamwise-periodic microchannels of rectangular cross-section has been studied in this work. Based on the lubrication approximation, an analytical approach is proposed for the frictional flow resistance. Using the analytical model developed for straight channels of arbitrary cross-section, compact models are developed for linear and sinusoidal wall shapes. The models are then examined with two asymptotic two-dimensional flows of: (a) very narrow and (b) very tall channels and compared with the available experimental and numerical data in the literature. An independent numerical study is also performed to evaluate the proposed models for the three-dimensional flow case. Effects of the channel aspect ratio and deviation factor on the pressure drop are also investigated. Results for the three-simensional flow show that the proposed compact models capture the trend of the numerical data with good accuracy.
Numerical and Experimental Study on a Wall Shear Stress Calibration Setup for Hot-Film Probes by the Use of a Radial Flow Cell Assay
Authors: Kipp H. , Hellmann D.-H. , Bo¨hle M.
Published: July 2010

In the present work, a calibration setup for flush-mounted hot-film sensor probes in turbulent and transitional flow regimes is evaluated experimentally and numerically. The diverging flow characteristic of a radial flow cell assay (RFC) is used to investigate position dependant wall shear stress distributions for different flow conditions in water. With regard to further quantitative wall shear stress measurements in hygienic designed multistage pumps, the new sensor calibration setup has to be applicable for a wall shear stress range up to 460 Pa. Due to the temperature-sensitive internal resistance shift and fluctuating sensor responses in the examined flow regimes, classical hot-film calibrations are limited to a small range of temperature differences and wall shear stresses. The limitation of the classical calibration technique is demonstrated in this work. As a more appropriate procedure a different calibration method is used. Herein, the sensor is calibrated in dependency of analytical wall shear stress distributions, temperatures as well as voltage responses. Thus, the measurement accuracy is improved by interpolating the measured wall shear stress values solely from measured temperatures and signal voltage responses. Emphasis is placed on the influence of varying fluid temperatures between 14.5 °C up to 20°C within the investigated wall shear stress range. Additionally, numerical simulations of the RFC are performed with commercial Computational Fluid Dynamics-Codes (CFD). As turbulence model the k-ω-SST-model with enhanced wall treatment is used. The experimental response is compared with the numerical and calculated results at a fluid temperature of 20°C. The results demonstrate that the new calibration setup reproduces the wall shear stress range very accurately.