bluuebunny/crossref_metadata_2025 huggingface dataset:
Design of a Protective Curtain System for High Rotational Speed Agricultural Disc Mowers
Authors: Ciappi Raquel , Miller Bradley , Petfield Stephen , Uthgenannt Christopher , Glancey James , Smith Kevin , Harkcom Melanie
Published: July 2010

A new protective curtain system for agricultural disc mowers has been designed and validated through a combination of novel testing methods. In order to understand performance requirements and choose the best solution to the problem, computer modeling, as well as small and full scale prototype testing was conducted. The new curtain system improves upon the current production design by adding a flexible joint between the top of the shroud and the curtain. This results in a reduction of force exerted on the crops by the curtain, the key performance metric for this project. A full scale prototype (P1) was constructed in order to confirm concept functionality, which led to a second generation prototype (P2) made of a heavier weight curtain fabric, in order to meet safety metrics. This new mounting method will improve cutting quality by reducing the force exerted on the crop by the curtain, while still meeting the safety requirements, in addition to providing a superior, more marketable product for Case-New Holland and higher crop yield for the customer.
A Hierarchical Model Validation of Predictive Models for Engineering Product Development
Authors: Youn Byeng D. , Jung Byung C. , Xi Zhimin , Kim Sang Bum
Published: July 2010

As the role of predictive models has increased, the fidelity of computational results has been of great concern to engineering decision makers. Often our limited understanding of complex systems leads to building inappropriate predictive models. To address a growing concern about the fidelity of the predictive models, this paper proposes a hierarchical model validation procedure with two validation activities: (1) validation planning (top-down) and (2) validation execution (bottom-up). In the validation planning, engineers define either the physics-of-failure (PoF) mechanisms or the system performances of interest. Then, the engineering system is decomposed into subsystems or components of which computer models are partially valid in terms of PoF mechanisms or system performances of interest. Validation planning will identify vital tests and predictive models along with both known and unknown model parameter(s). The validation execution takes a bottom-up approach, improving the fidelity of the computer model at any hierarchical level using a statistical calibration technique. This technique compares the observed test results with the predicted results from the computer model. A likelihood function is used for the comparison metric. In the statistical calibration, an optimization technique is employed to maximize the likelihood function while determining the unknown model parameters. As the predictive model at a lower hierarchy level becomes valid, the valid model is fused into a model at a higher hierarchy level. The validation execution is then continued for the model at the higher hierarchy level. A cellular phone is used to demonstrate the hierarchical validation of predictive models presented in this paper.
Optimization of Piezoelectric Uniflex Microactuators
Authors: Kommepalli Hareesh K. R. , Rahn Christopher D. , Tadigadapa Srinivas A.
Published: July 2010

Microactuators provide controlled motion and force for applications ranging from RF switches to rate gyros. Large amplitude response in piezoelectric actuators requires amplification of their small strain. This paper studies the performance of a uniflex actuator in terms of its displacement and blocking force compared to uniflex and flextensional actuators. A uniflex microactuator combines the strain amplification mechanisms of a unimorph and flexural motion to produce large displacement and blocking force. Analytical models for displacement and blocking force for all the three actuators are used in optimization, to study their relative performance. The uniflex actuator outperforms both unimorph and flextensional actuators in displacement, but, the unimorph actuator generates more blocking force. The uniflex actuator can therefore be used in applications that demand higher displacement and lower blocking force compared to a unimorph actuator.
2D Multi-Objective Placement Algorithm for Free-Form Components
Authors: Jacquenot Guillaume , Bennis Fouad , Maisonneuve Jean-Jacques , Wenger Philippe
Published: July 2010

This article presents a generic method to solve 2D multiobjective placement problem for free-form components. The proposed method is a relaxed placement technique combined with an hybrid algorithm based on a genetic algorithm and a separation algorithm. The genetic algorithm is used as a global optimizer and is in charge of efficiently exploring the search space. The separation algorithm is used to legalize solutions proposed by the global optimizer, so that placement constraints are satisfied. A test case illustrates the application of the proposed method. Extensions for solving the 3D problem are given at the end of the article.
Symmetry in a Bistable MEMS Device With Force Gage and Comb Drive
Authors: Zirbel Shannon
Published: July 2010

This photo shows a bistable microelectromechanical (MEMS) device that incorporates many common elements of microsystems, including the comb drive and force gage. This device also is designed to exhibit bistable behavior. The photo emphasizes the symmetry of the device.
Biosensor Microassembly Platform: Design and Automation
Authors: Malima Asanterabi , Busnaina Ahmed , Somu Sivasubramanian
Published: July 2010

We present a custom built Biosensor Microassembly Platform (BMP) for assembling a nanoparticles-based microscale in-vivo biosensor. Conducting directed assembly of nanoparticles on a 0.01 mm2 microchip is a very challenging problem. Complexities arise from assembling micro-components of different materials, and assembling antibody functionalized nanoparticles into their predetermined nanoscale trenches on the biosensor. Using our designed platform, we merge vision information with motion control efficiently, so that precise manipulation of the stages and microscopes facilitates the assembly process of the in-vivo biosensor. Along with Biosensor Microassembly Platform system design and automation, we demonstrate assembly of an in-vivo biosensor which has numerous applications in biomedical and health industry.
Off-Center Force Gage on a Tristable MEMS Device
Authors: Zirbel Shannon
Published: July 2010

This photo shows a force gage attached to a tristable microelectromechanical (MEMS) device. While the force gage is common in Microsystems, this photo shows how movement during shipping can jostle the device out of its manufactured position.
Mechanical and Piezoelectric Properties of PZT Nanofibers
Authors: Xu Shiyou , Shi Yong
Published: July 2010

This paper reports the measurement of the mechanical and piezoelectric properties of Lead Zirconate Titanate (PbZr52Ti48O3, PZT) nanofibers. Partially aligned PZT nanofibers were fabricated by sol-gel electrospinning process. The diameters of the fiber were tuned from 50 to 150 nm by changing the concentration of the sol-gel in the precursor. The fiber consists of nanocrystal grains with average grain size of 10 nm. The Young’s modulus of individual fiber was obtained by nanoscale three-point bending using Atomic Force Microscope (AFM), which was 42.99GPa. Titanium strip was used as the substrate to collect the nanofibers for the three-point bending test to measure the piezoelectric response. The output voltages from the nanofibers under different strain were recorded by Labview, and the highest value of the output voltage was 0.17±0.005V. These results have shown that PZT nanofibers have great potential in nano sensor and actuator applications.
Kinematics and Statics of Cooperative Multi-Robot Aerial Manipulation With Cables
Authors: Michael Nathan , Kim Soonkyum , Fink Jonathan , Kumar Vijay
Published: July 2010

This paper addresses the forward and inverse kinematics of payloads carried by aerial robots. We address the cases with one, two, and three aerial robots and derive the kinematics and conditions for stable static equilibrium. For the case with one or two robots, we can establish the maximum number of equilibrium positions. The three-robot case is seen to be much harder primarily because of the non-negative tension constraints. We restrict the set of possible solutions to the forward and inverse problems by considering the equations of static equilibrium and kinematic constraints. Analytic and numeric methods to determine equilibrium configurations and stability are presented.
Requirement Analysis and Negotiation for Feasible Service Development
Authors: Watanabe Kentaro , Kimita Koji , Akasaka Fumiya , Shimomura Yoshiki
Published: July 2010

Service design has been generally discussed in the engineering field in recent years. Many manufacturers have been focusing more on services than on products themselves. To ensure the feasibility of designed services, a service designer should consider not only customer values but also the requirements of a service provider. However, there are few standard methods to deal with the service provider’s requirements and to reflect them in the service design. In this research, the authors suggest a method to describe service provider’s requirements for the service design based on the Service Engineering methodology. In addition, the authors propose a design process to analyze service providers’ requirements and adjust the specifications of a designed service in order to fulfill the requirements of both service providers and service receivers simultaneously.
Design of Honeycomb Meta-Materials for High Shear Flexure
Authors: Ju Jaehyung , Summers Joshua D. , Ziegert John , Fadel George
Published: July 2010

A numerical study for a functional design of honeycomb meta-materials targeting flexible shear properties (about 6.5MPa effective shear modulus and 15% maximum effective shear strain) is conducted with two material selections — polycarbonate (PC) and mild-steel (MS), and five honeycomb configurations. Cell wall thicknesses are found for each material to reach the target shear modulus for available cell heights with five honeycomb configurations. PC honeycomb structures can be tailored with 0.4 to 1.3mm cell wall thicknesses to attain the 6.5MPa shear modulus. MS honeycombs can be built with 0.2mm or lower wall thicknesses to reach the target shear modulus. Sensitivity of wall thickness on effective properties may be a hurdle to overcome when designing metallic honeycombs. The sensitivity appears to be more significant with an increased number of unit cells in the vertical direction. PC auxetic honeycombs having 0.4 to 1.9 mm cell wall thicknesses show 15% maximum effective shear strain without local cell damage. Auxetic honeycombs having negative Poisson’s ratio show lower effective shear moduli and higher maximum effective shear strains than the regular counterparts, implying that auxetic honeycombs are candidate geometries for a shear flexure design.
A Comparison of Metamodel-Assisted Pre-Screening Criteria for Multi-Objective Genetic Algorithms
Authors: Mari´n Vero´nica E. , Rinco´n Jose´ A. , Romero David A.
Published: July 2010

Over the last few years, research activity in approximation (e.g. metamodels) and optimization (e.g. genetic algorithms) methods has improved upon current practices in engineering design and optimization of complex systems with respect to multiple performance metrics, by reducing the number of evaluations of the system’s model that are needed to obtain the set of non-dominated solutions to a given multi-objetive optimal design problem. To this end, several authors have proposed to enhance Multi-Objective Genetic Algorithms (MOGAs) with metamodel-based pre-screening criteria (PSC), so that only those solutions that have the most potential to improve the current approximation of the Pareto Front are evaluated with the (costly) system model. The main goals of this work are to compare the performance of several PSC with an array of test functions taken from the literature, and to study the potential effect on their effectiveness and efficiency of using multi-response metamodels, instead of building independent, individual metamodels for each objective function, as has been done in previous work. Our preliminary results show that no single PSC is observed to be superior overall, though the Minimum of Minimum Distances and Expected Improvement criteria outperformed other PSC in most cases. Results also show that the use of multi-response metamodels improved both the effectiveness and efficiency of PSC and the quality of solution at the end of the optimization in 50% to 60% of test cases.
Kinematic Convexity of Planar Displacements Based on an Approximately Bi-Invariant Metric
Authors: Ge Q. J. , Wu Jun , Purwar Anurag , Gao Feng
Published: July 2010

This paper explores the concept of kinematic convexity of planar displacements as an extension of the projective convexity in computational geometry to planar kinematics. This is achieved with the help of planar quaternions which converts planar displacements into points in the space of planar quaternions called the image space. In this way, projective convexity of points in the image space is developed and used as a representation of kinematic convexity of planar displacements. To address the issue of distance metric for planar displacements, we explored the connection between planar quaternions and quaternions and formulated the concept of kinematic convexity in the space of quaternions where a bi-invariant metric exists. An example is provided in the end to illustrate the use of kinematic convexity for estimating the “closest distance” from a fixed body to a moving body undergoing a rational Be´zier motion.
Interactive Dimensional Synthesis and Motion Design of Planar 6R Closed Chains via Constraint Manifold Modification
Authors: Wu Jun , Purwar Anurag , Ge Q. J.
Published: July 2010

In this paper, we present an interactive, visual design approach for the dimensional synthesis of planar 4R, 5R, and 6R closed chains for a given rational motion using constraint manifold modification. This approach is implemented in an interactive software tool that provides mechanism designers with an intuitive way to determine the dimensional parameters of planar mechanisms, and in the process equips them with an understanding of the design process. The theoretical foundation of this work is based on representing planar displacements with planar quaternions which can be seen as points in a special higher dimensional projective space (called the image space), and on formulating the kinematic constraints of closed chains as algebraic surfaces in the image space. Kinematic constraints under consideration limit the positions and orientation of the coupler in its workspace. In this way, a given motion of a mechanism in the Cartesian space maps to a curve in the image space that has to stay within the bounds of the algebraic surfaces. Thus, the problem of dimensional synthesis is reduced to determining parameters of equations that describe algebraic surfaces. This paper is an extension of our previous work in which we had presented some preliminary results based on an optimization method. We show that the interactive approach presented here is general in nature, and can be easily used for the dimensional synthesis of any mechanism for which kinematic constraints can be expressed algebraically. The process of designing is fast, intuitive, and especially useful when an optimization based approach would be computationally demanding, and mathematically difficult to formulate. This simple approach also provides a basis for students and early designers to learn and understand the process of mechanism design by simple geometric manipulations.
FlexDex™: A Minimally Invasive Surgical Tool With Enhanced Dexterity and Intuitive Actuation
Authors: Awtar Shorya , Trutna Tristan T. , Abani Rosa , Nielsen Jens M. , Mansfield Andrew B.
Published: July 2010

This paper presents the design and fabrication of a novel minimally invasive surgical (MIS) tool — FlexDex™ — that provides enhanced dexterity, intuitive actuation, and natural force feedback in a cost-effective compact package. These attributes are accomplished by means of a fundamentally new MIS tool design paradigm that employs a tool reference attached to the surgeon’s arm, and utilizes a virtual center at the tool input that coincides with the surgeon’s wrist. The resulting physical configuration enables a highly intuitive one-to-one mapping of the surgeon’s arm and hand motions at the tool input to the end-effector motions at the tool output inside the patient’s body. Furthermore, a purely mechanical design ensures low-cost, simple construction, and natural force feedback. A functional decomposition of the proposed design paradigm and associated physical configuration is carried out to identify key modules in the system. This allows for the conceptual and detailed design of each module, followed by system-level integration. The key innovative aspects of the tool design include a three-dimensional parallel-kinematic virtual center mechanism, a decoupled 2DoF end-effector design, and the associated transmissions system.
Turbulent Solid-Liquid Two-Phase Flow Simulation With Turbulence Intensity and Time Scale Model
Authors: Mansoori Z. , Saffar-Avval M. , Nojabaii B. , Behzad F. , Ahmadi G.
Published: July 2010

Two-dimensional simulation of turbulent solid-liquid flow is carried out. The modeling is established for a two-phase flow of solid particles in a vertical pipe water flow. Governing equations of flow and turbulence field are solved in an Eulerian-Lagrangian approach by the use of k-τ (turbulence time scale) model and trajectories of the particles are obtained using the Lagrangian method with a deterministic inter-particle collision model. Comparison between the results of the model for mean and r.m.s velocities of the liquid and solid phase with the experimental results shows a good agreement. The effect of variation of particle density and concentration are studied.
Teaching How to Use the CFD Approach by an Example: Hydrodynamics Within a Passenger Car Compartment in Motion
Authors: Polanco Geanette , Garci´a Nelson , Rojas Luis
Published: July 2010

The CDF methodology is applied to the study of the air flow around a 2-D car and its interaction with the cabin internal air. The flow visualization or computational works enable engineers to calculate different car characteristics like drag coefficient, external and internal air flow patterns, etc. Therefore, the teaching of this approach to student is a very important task to take into account in the formation process of new engineers. This work shows the numerical simulation of a specific passenger car compartment configuration solving the Navier-Stokes equations along with the k-e turbulence model using the finite volume method. The indoor air flow is produced by the interaction between the cabin inner air with the external flow through two glass windows (one in the front seat and one in the back seat). This configuration represents a common situation for the passenger car compartment. The study covers two different car speeds, 50 and 100 km/h. The flow field is studied in both steady state and transient conditions with time step of 0.01 s, for both car speeds, 50 km/h and 100 km/h. The different steps of the CFD work are commented to show to the reader the distinct states that must be cover in this kind of work. As results of the detailed methodology followed, the influence of the domain size on the flow fields is highlighted, the requirement of a better mesh quality is exposed and flow field results are analyzed using two different forms of graphic representations. The results show the physics behavior of the flow and the presence of flow structures, as for instance, indoor air recirculation zones delimited by internal seats, as well as, the vortex presence at the back of the cabin.
Simulation of Rarefied Gas Flows in MEMS/NEMS Using a Molecular Method
Authors: Ghezel Sofloo Hadi , Ebrahimi Reza , Shams Alireza
Published: July 2010

In this work, the development of a two-dimensional Direct Simulation Monte Carlo (DSMC) Program for pressure boundaries using unstructured cells and its applications to typical micro-scale gas flows are described. For the molecular collision kinetics, variable hard sphere molecular model and no time counter collision sampling scheme have been used. Applications to micro-scale gas flows include micro-nozzel, nano channel and slider air bearing. The aim is to further test the treatment of pressure boundaries. For slider air bearing gas flows of the computer hard drive, the simulated gas pressures, at different rotating speeds, have a very good agreement with previous studies. The applicability of the treatment of pressure boundaries using the equilibrium Maxwell-Boltzmann distribution function was discussed in terms of the magnitude of the local Knudsen number at the pressure boundary for micro-nozzles and slider air bearing applications.
Temporal Development of the Wake of a Non-Impulsively Started Circular Cylinder
Authors: Tonui Nelson , Sumner David
Published: July 2010

Flow around a circular cylinder “impulsively” set into motion was investigated experimentally using the particle image velocimetry (PIV) technique. The experiments were conducted in water in an X-Y towing tank at a Reynolds number of Re = 500. Since a true impulsive start can only be approximated in physical experiments, the objective was to determine the experimental conditions for which the cylinder could be considered impulsively started. The dimensionless acceleration parameter was varied from a* = 0.5 to 10, and the temporal development of the near-wake recirculation zone was examined from the initial start until the wake became asymmetric. With increasing acceleration parameter, at a given elapsed time from the start of motion, there was an increase in the length of the recirculation zone, the maximum vorticity within the recirculation zone, the streamwise location of the primary attached eddies from the base of the cylinder, and the strength (circulation) of the primary eddies. The results showed that the spatial development of the recirculation zone was strongly dependent on the distance traveled by the cylinder following the start of motion, rather than the method of acceleration, and the flow around the circular cylinder could be considered impulsively started for a* ≥ 0.5.
Evaluation of the Flow Inside a Side Channel Pump by the Application of an Analytical Model and CFD
Authors: Bo¨hle Martin , Mu¨ller Thorsten
Published: July 2010

The flow inside a channel pump is indeed complex and has not been understood completely until now. Especially, if the flow is to be optimised with respect to flow losses and/or acoustics details of the flow must be known and evaluated. In the present paper the flow physics of a side channel pump are examined. The paper starts with a description of the flow phenomenon occurring in the impeller, the side channel and on the interface of the impeller and the side channel. From this consideration an analytical model is derived which describes the efficiencies of the impeller and the side channel. In order to apply this model the exchange volume flow rate between the impeller and the side channel must be known. This flow quantity is calculated by CFD simulations. Finally, both the analytical model and CFD are used for the analysis of the flow inside a model side channel pump. The results of the analytical model are compared with the CFD-results and by doing this it is checked whether the results of the analytical model are in agreement with the CFD-results. Furthermore the CFD-results are used to demonstrate the dominant flow phenomenon inside a side channel pump. At the end a procedure for the evaluation of the flow inside a side channel pump is described.
Ultrasonically Driven Cavitating Atomizer: Prototype Fabrication and Characterization
Authors: Akafuah Nelson K. , Salazar Abraham J. , Saito Kozo , Srinivasan Vedanth
Published: July 2010

A new device, ultrasonic cavitating atomizer (UCA), has been developed that uses ultrasonically driven cavitation to produce fine droplets. In the UCA the role of cavitation is explicitly configured to enhance the breakup of the liquid jet exiting the nozzle into fine droplets; the pressure modulation also assists the breakup process. The experimental study involves the fabrication of a prototype and the building of an experimental rig to test the prototype using water as the working fluid. The parameters tested include liquid injection pressure, horn tip frequency and liquid flow rate. The result shows improvement in the atomization of water with the application of ultrasonic cavitation.
Thermodynamic Effect on a Cavitating Inducer in Liquid Hydrogen
Authors: Goncalve`s Eric , Fortes Patella Regiane , Rolland Julien , Pouffary Benoit , Challier Guillaume
Published: July 2010

This study was led in collaboration with the French space agency (CNES) and the rocket engine division of Snecma. The main aims were the simulations and the analyses of cavitating flows in the rocket engine turbopump inducers, where the run fluids are LH2 and LOx under cryogenic conditions. A ρ(P,T) state law modeling the cavitation phenomenon was integrated by the laboratory LEGI in the commercial CFD code Fine/Turbo™, developed by Numeca International. Various 3D numerical results are given for an inducer geometry and comparisons are made with experimental data (head drop curves) obtained by NASA.
Multi-Model Formulation for Compressible Multiphysics and Multiphase Flows: An Efficient Coupling Algorithm
Authors: Verhaegen Julien , Massoni Jacques , Daniel Eric
Published: July 2010

A coupling between a general multiphase flows model and a two-phase dilute flow model is presented. Both models are based on Eulerian approach (two fluids models) and compressible flows are considered. This coupling permits to solve problems in which a multiphase description (involving N phases) is necessary to obtain a good physical behavior of the flow on short times: it corresponds to a given location on the computational domain. Then the flow is developing and far from the location of the initial establishment of the flow, a simpler model can be used, for example a dilute two-phase model one. A methodology for coupling both models is necessary in order to get efficient calculations and a physical consistency. This coupling is not only a challenge regarding the computing resources or the programming. We also require that the wave patterns are correctly transmitted through the coupling interface. We then developed specific Riemann solvers that allow the transmission of acoustic or material waves. We also require the preservation of the conservative quantities such as mass, momentum and energy. The method is checked on ID case: propagation of uniform flows, shock tubes. Multidimensional problem are also presented, showing the efficiency of the coupling methodology regarding CPU time.
X-Ray Flow Visualization of a Circular Hydraulic Jump
Authors: DiVall Megan R. , Heindel Theodore J.
Published: July 2010

The circular hydraulic jump is a product of the impingement of a vertical, circular jet upon a smooth horizontal surface. Previous studies of this phenomenon have used methods such as electrical contact probes, photography, and lasers to measure various features. This study utilizes X-ray computed tomography (CT) to visualize the circular hydraulic jump; analysis is then completed on the reconstructed 3D image. Time-averaged data of the film thickness before and after the jump and the jump radius, as measured from the X-ray CT images, compare well with available literature. Potential imaging improvements with the current equipment have been identified, particularly with respect to measuring film thickness.
3D Numerical Simulation and PEPT Experimental Investigation of Pressurized Gas-Solid Fluidized Bed Hydrodynamic
Authors: Fede P. , Moula G. , Ingram A. , Dumas T. , Simonin O.
Published: July 2010

The present paper is dedicated to numerical and experimental study of the hydrodynamic of a non-reactive isothermal pressurized fluidized bed. Experimental data have been obtained using PEPT technique allowing to track a particle trajectory inside a dense fluidized bed. A specific post-processing approach has been developed to compute the Eulerian time-averaged particle velocity field. The comparison with 3-dimensional numerical model predictions shows a good agreement in the core of the fluidized bed. In contrast, in the near wall region the numerical model overestimate the downward particle velocity. The modification of particle phase wall boundary condition improves the numerical predictions.
Localized Particle Concentration Measurement in Slurry Flows Using A-Scan Ultrasound Technique
Authors: Furlan John M. , Mundla Venkat , Kadambi Jaikrishnan , Hoyt Nathaniel , Visintainer Robert , Addie Greame
Published: July 2010

In the design of slurry transport equipment, the effects of solid particle concentration on hydraulic performance and wear have to be considered. This study involves examining the acoustic properties of slurry flows such as velocity, backscatter and attenuation as a function of volume fraction of solid particles. Ultrasound A-mode imaging method is developed to obtain particle concentration in a flow of soda lime glass particles (diameter of 200 micron) and water slurry in a 1″ diameter pipe. Based on the acoustic properties of the slurry a technique is developed to measure local solid particle concentrations. The technique is used to obtain concentration profiles in homogeneous (vertical flow) and non-homogeneous (horizontal flow) slurry flows with solid particle concentrations ranging from 1–10% by volume. The algorithm developed utilizes the power spectrum and attenuation measurements obtained from the homogeneous loop as calibration data in order to obtain concentration profiles in other (i.e. non-homogenous) flow regimes. A computational study using FLUENT was performed and a comparison is made with the experimental results. A reasonable agreement between the experimental and computational results is observed.
CFD Simulation of Liquid-Liquid Hydrocyclone: Oil/Water Application
Authors: Kharoua Nabil , Khezzar Lyes , Nemouchi Zoubir
Published: July 2010

In the present work, the oil-water separation occurring inside a de-oiling hydrocyclone is investigated numerically using the RSM [1] and the RNG k-ε [2] turbulence models combined with the multiphase mixture model of Manninen et al. [3] implemented in the commercial code FLUENT. Interesting results are obtained concerning the effects of the inlet oil concentration, the oil droplet size, and the flow rate on the separation efficiency. The results are in agreement with the experimental measurements of Colman et al., [4]. The separation efficiency is known to be unaffected for a large range of inlet oil concentrations (Colman et al. [4], Gomez et al. [5]) and this is confirmed in the present study. In addition to the overall performance parameters, remarkable results describing the flow field behavior are obtained. The radial profiles of the axial and tangential velocity components are discussed. The flow reversal on the axis and the swirling behavior are shown. Results concerning the pressure drops, the friction coefficient and the turbulent Reynolds stresses are also presented. Since detailed results on the flow field for de-oiling hydrocyclones are scarce, the present study might be useful for future studies aiming to improve liquid-liquid separation efficiency depending strongly on the inside flow field behavior.
Flow Stability in Rotating Cylinders With a Porous Lining
Authors: Subotic M. , Lai F. C.
Published: July 2010

The effects of porous sleeve properties on the flow stability in rotating cylinders are numerically investigated in this study. To this end, three-dimensional momentum equations for the porous and fluid layers are formulated separately in terms of velocity and vorticity. These equations are then numerically solved over a wide range of parameters (10−2 ≤ Da ≤ 10−5, 2000 ≤ Ta ≤ 5000) to determine the critical Taylor number for the onset of flow instability for various porous sleeve properties. The results obtained show that the presence of a porous sleeve in general has a stabilizing effect on the flow in the annulus.
Effects of Blade Outlet Width on Flow Field and Characteristic of Centrifugal Pumps
Authors: Tan Ming-gao , Liu Hou-lin , Yuan Shou-qi , Wang Yong , Wang Kai
Published: July 2010

The present deficiency about numerical simulation research on blade outlet width of centrifugal pumps is pointed out. In the case of different outlet widths, the flow field in six centrifugal pumps whose specific speed vary from 45 to 260 are simulated by using commercial code FLUENT and the characteristics are predicted. The standard k-ε turbulence model and SIMPLEC algorithm are chosen in FLUENT. The simulation is steady and moving reference frame is used to consider rotor-stator interaction. The research results show that the change of impeller outlet width has obvious impacts on characteristics at design point, flow field and the shape of performance curves. At nominal condition, the change of outlet width has more important effects on moderate specific speed centrifugal pumps. The flow field analysis indicates that blade outlet width change has an important effect on the location and area of low pressure region behind the blade inlet, jet-wake structure in impellers, the secondary flow in volute cross section and the back flow in impellers. The head-flow curve becomes more flat with the increase of outlet width. For moderate and low specific speed centrifugal pumps, the high efficiency area of efficiency-flow curve get bigger with the increase of outlet width and the area will be constant within certain outlet width change scope for high specific speed centrifugal pump. The research results agree well with experiment results.
Investigation of Fan Casing Aerodynamic Noise at the Blade Passing Frequency
Authors: Cai Jian-Cheng , Qi Da-Tong , Lu Fu-An
Published: July 2010

From our previous studies of fan casing vibroacoustics, it was found that noise caused by casing vibration was fairly small compared to its aeroacoustic counterpart. In the present work, a numerical study on the aerodynamic tonal noise of a centrifugal fan casing was carried out. A 3-D numerical simulation of turbulent unsteady flow on the whole impeller-volute configuration was performed using computational fluid dynamics (CFD) technique in order to obtain the pressure fluctuations on the casing wall which serve as aeroacoustic dipole sources. Three different flow rates were simulated: the best efficiency point (BEP), 1.382×BEP and the maximal flow rate (2.104×BEP). Fast Fourier Transform (FFT) was applied to the time series of pressure fluctuations to extract the blade passing frequency (BPF) component constituting the source term of the wave equation. Boundary element method (BEM) was used to solve the inhomogeneous frequency-domain wave equation. The influence of the casing on the sound field was taken into account in simulating the noise radiation by taking it as a rigid body. Results showed that the presence of the casing could greatly affect sound propagation. With the increase of flow rate, the radiated sound power rose drastically. The tonal blade noise was also investigated using Lowson’s formulation of rotor noise model, and the results showed that it’s smaller than the tonal casing noise.
Research on Hydraulic Structure of Low Pressure Pulsations Double-Suction Pumps Based on Unsteady Flow Numerical Simulation
Authors: Li Hong , Shen Zhenhua , Ji Liujin , Yuan Jianping , Yuan Shouqi
Published: July 2010

Low pressure pulsations double-suction pumps, which can reduce the pump outlet pressure pulsations, are widely used in paper-making technique processes. To design the proper geometric sizes and improve the inner flow will reduce the outlet pressure pulsations. From the aspect of the pump hydraulic design, several optimized projects to lower the pressure pulsations are proposed, such as optimizing the arrangement of blades, changing the shape of the blades, changing the size of base circle and the shape of tongue of the volute, etc. The unsteady flows in different time and different impeller positions in every project have been simulated using the CFD software. The outlet pressure distribution is caught and described as the 2-D graphs of pressure pulsations versus time by EXCEL and MATLAB. By comparing the results of all optimized schemes, it has been shown that the stagger arrangement of blades, the increased diameter of base circle, the ladder tongue of volute, more blades of impeller all can reduce the outlet pressure pulsations of centrifugal pump.
Influence of Rotational Speed on Thermodynamic Effect in a Cavitating Inducer
Authors: Kikuta Kengo , Yoshida Yoshiki , Hashimoto Tomoyuki , Nanri Hideaki , Mizuno Tsutomu , Shimiya Noriyuki
Published: July 2010

To estimate the influence of velocity on the thermodynamic effect, we conducted experiments in which the inducer rotational speed was changed in liquid nitrogen. The experiments in liquid nitrogen and in cold water allowed us to estimate the amplitude of the thermodynamic effect. In the experiment with lower rotational speed, suction performance was improved. The cavity length at lower rotational speed was shorter than that at higher speed. Thus, we confirmed that the degree of the thermodynamic effect depends on the rotational speed as lower rotational speed suppresses cavity length. Temperature depression was estimated based on a comparison of cavity length in liquid nitrogen and that in water. We found that the degree of temperature depression became smaller when the rotational speed was lower.
Influence of Peripheral Opening on the Central Core Flow Behaviour in a Rotor-Stator System
Authors: Abdel Nour Fadi , Debuchy Roger , Bois Ge´rard , Naji Hassan
Published: July 2010

This work relates to an experimental, theoretical and numerical study of a turbulent flow with separated boundary layers between a rotating disc (rotor) and a stationary one (stator) without any superposed radial flow. The originality of this study is that the pre-swirl ratio at the periphery of the cavity (Kp) is lower than the core swirl ratio (KB) corresponding to the solid body rotation, as predicted by Batchelor in the case of infinite discs: this is what the authors call a rotor-stator system with low pre-swirl ratio. Under these conditions, recent works have shown that the core swirl ratio (K) is a decreasing function of the radius, at least in the peripheral region. This behaviour has rather been observed in the cavities with superposed centripetal radial flow. In the present paper, this flow property is explained starting from an asymptotic approach which leads to step-by-step analytical computation method of the radial distribution of the core swirl ratio (K) and of the static pressure on the stator side p*. The validation of the theory is based both on experimental and numerical results. The experimental tests are carried out in a rotor-stator cavity for different values of the pre-swirl ratio, which is done by geometrical changes of the periphery of the system. The experimental data mostly include the velocity measurements and the turbulent correlations by hot-wire anemometry in interstice between the discs, as well as the static pressure measurements on the stator side. Comparisons with predictions from the CFD code Fluent are also provided. The numerical simulations are performed using the two-equation k – ω SST turbulence model, assuming a 2D-axisymmetric steady flow, in a domain corresponding to the inter-disks spacing and the peripheral outer region of the cavity. Computed and experimental values are in good agreement with the theoretical results.
DNS/DPS of Inertial Droplet Coalescence in Homogeneous Isotropic Turbulence and Comparison With PDF Model Predictions Using the Direct Quadrature Method of Moments
Authors: Wunsch Dirk , Belt Roel , Fede Pascal , Simonin Olivier
Published: July 2010

To analyze in detail the coalescence mechanisms and validate modeling approaches, deterministic Lagrangian simulations of droplet trajectories (DPS) coupled with Direct Numerical Simulations (DNS) of a Homogeneous Isotropic Turbulence (HIT) are performed. The influence of the colliding particle velocity correlations induced by the fluid turbulence on the rate of droplet coalescence is investigated for different particle inertia. The results are compared to predictions using the Direct Quadrature Method of Moments (DQMOM) accounting for coalescence. The particle diameter distribution is written as a summation of Dirac functions. This allows to derive Eulerian transport equations for the dispersed phase statistics, which account for coalescence and conserve the low-order moments of the particle size distribution. The collision terms are modeled applying the molecular chaos assumption in order to account for coalescence. Particle size distributions and moments obtained from DQMOM are compared to those of the DNS/DPS simulations in function of particle inertia.
Carrier Phase Turbulence in Fluid-Particle Flows (Plenary)
Authors: Crowe Clayton T. , Schwarzkopf John D.
Published: July 2010

Turbulence in the carrier phase of fluid-particle flows plays an important role in mixing and shear stress. The availability of a reliable model for turbulence is essential to the development of computational models that can be applied with confidence to engineering systems. The general approach is to add a term to the Navier-Stokes equations that represents the force on the fluid due to due to particle drag and to carry out the procedures used for single phase flows to derive equations for carrier-phase turbulence. The problem with this approach is presented. A flow configuration representing a basic test case, which can be used to judge the viability of any model, is introduced. A recently developed turbulence model using volume averaging and based on the turbulence energy-dissipation description of turbulence is presented. This model is applied to the basic test case and to experiments for particles dropping in a quiescent fluid and gas-particle vertical channel flow. The predictions show good agreement with experimental data.
Research of Tubular Pumping Systems on Dual-Directional Operation
Authors: Li Long , Ze Wang , Yang Xuelin , Li Dan
Published: July 2010

The tubular pumping system on dual-directional operation is used extensively for drainage and feedwater pumping stations of the cities and towns. The performance of the dual-directional operation of pumping systems is different with that of simple-way operation. The article described the three-dimensional fluid flow and the predicted performance of the numerical investigation inside a tubular pumping station on dual-directional operation, based on the Reynolds time-averaged Navier-Stokes equations and the realizable k-ε turbulent flow model, applied the law-of-wall and sliding mesh technique, and comparing with the experiment data. The main phenomena existing in pressure contours, velocity contours, velocity vectors and flow lines is showed. The disturbance of fluid flow from the pump outlet to pumping station channel is researched. The axial-whirling flow, circulation-vortex flow is discovered inside discharge diffuser of tubular pumping station on feed-directional operation. The axial-whirling flow is strengthened as a result of diffuse flow. The circulation-vortex flow of the impeller outlet is enhanced in the radius and reduced in the middle of discharge diffuser without guide vanes. There is more loss of head in discharge diffuser of the channel, comparing with that of the suction reducer. It was a close predicted performance of numerical simulation with that of the experiment in the best efficiency point. There was a more difference between the predicted performances with that of the experiment data on the feedwater-directional operation, comparing that of the drainagewater -directional operation.
Properties of Aerofoil and Blade Cascade in Hydraulic Machinery
Authors: Li Long , Hu Rongxia , Li Dan , Yang Fei
Published: July 2010

The hydrodynamic properties of the blade aerofoil differ from that of the airfoil of the blade cascade in a pump of low head. The numerical simulation of the flow quality in the impeller was made on a commercial axial pump of low head. The blade cascade flow in impeller was discussed, and the characteristic of the airfoil profile of the impeller blade was studied using the FLUENT software. The characteristic of the isolation aerofoil was compared with that of the aerofoil of impeller blade cascade. The research results show that the pressure on the surface of the aerofoil of blade cascade is higher than that of the corresponding isolation aerofoil, under the designed work conditions, at the same angle and the same place. On the same aerofoil, the change of pressure of aerofoil of the blade cascade is less than the pressure of the isolation aerofoil on high pressure side, but it was opposite on low pressure side.
Research on the Design Method of the Centrifugal Pump With Splitter Blades
Authors: Yuan Shouqi , Zhang Jinfeng , Tang Yue , Yuan Jianping , Fu Yuedeng
Published: July 2010

The research on a centrifugal pump of low specific speed with splitter blades was carried out in recent years by our group, is systematically introduced in this paper. The design method is summarized also. At the beginning, based on the former L9(34) orthogonal test, Particle Imagine Velocity (PIV) tests and Computational Fluid Dynamics (CFD) simulations were carried out for several designs with different splitter blade length. Results show that for an impeller with splitter blades the “jet-wake” flow at the impeller outlet is improved, and the velocity distribution inside the impeller is more uniform. This explains that the impeller with splitter blades shows higher performance (especially in head and efficiency). Meanwhile, the numerical simulation results were compared with the test results, which confirm that, CFD technology can be used to observe inner flow distribution and forecast pump performance tendency. Later, a further L9(34) orthogonal test, which adopt the blade number as a new variable, was designed to explore the relationship between geometry parameters of splitter blade and pump performance, and corresponding CFD simulations for the flow field with volute were also done. From the test results the influence of the main design parameters on the hydraulic performance of a centrifugal pump and its reasonable value range are determined. The simulations forecasted pump performance show good consistency with that from tests at the rated point, and the simulated error at other flow rates were analyzed. Thirdly, in order to save research cost, numerical simulations were done for the full flow field including the cavity inside the volute and impeller. By analyzing the distribution law of blade torque and turbulent kinetic energy in the impeller, the value fetching principle for the splitter blade inlet diameter is presented as “the splitter blades torque should be positive”, and by analyzing the distribution of blades loading, the flow distribution rules and pump performance influenced by different splitter blades off-setting angles and inlet diameters were discovered. The disk friction loss, which consuming much energy in centrifugal pumps, was also forecasted at various operating conditions. The results were compared with that from empirical formulas, which show great accordance at the rated point, and the forecasted results at off-design points were analyzed also. Finally, the research results and the design method for the centrifugal pump with splitter blades, such as how to select splitter blade number, the off-setting angle, the inlet diameter and the deflection angle, were summarized.