bluuebunny/crossref_metadata_2025 huggingface dataset:
Hands-On Water Purification Experiments Using the Adaptive WaTER Laboratory for Undergraduate Education and K-12 Outreach
Authors: Boyle Paul M. , Houchens Brent C.
Published: July 2009

A bench-top educational system, the Adaptive Water Treatment for Education and Research (WaTER) Laboratory, has been developed as part of a year-long capstone design project. The Adaptive WaTER Lab teaches students about the effectiveness of various water purification techniques. Stackable housings employ six different filtration and purification methods including: sediment filtration, carbon filtration, chemical disinfection, reverse osmosis, forward osmosis, and ultraviolet light disinfection. Filtration pressure is supplied by a hand or foot pump, and two rechargeable batteries are required for the UV sterilization unit. The advantages and limitations of each technique are investigated, with learning performance criteria measured by knowledge of: material costs, contaminant removal or neutralization capabilities (from large sediment to bacteria and viruses to chemicals), robustness and longevity, and power requirements and efficiencies. Finally, suitable combinations of treatment techniques are studied for specific contamination issues, with the ultimate goal of producing potable water. The importance of sustainable water use is also discussed. Background information and suggested experiments are introduced through accompanying educational packets. This system has had a successful impact on undergraduate education. The metrics of success include a published journal article, an awarded EPA P3 educational grant and a pending patent for the undergraduates involved in the development of the Lab. Other undergraduates are currently involved in a design for manufacturability study. Finally, the Lab has served as a demonstration tool in a new interdisciplinary engineering course “Integrated Approaches to Sustainable Development.” The Adaptive WaTER Lab has also been used in hands-on outreach to over 300 underrepresented K-12 students in the Houston area. Two high school students borrowed the original prototype of the Lab to use in an Earth Day demonstration, and one student recently worked on an individual project using the Lab. Because the Lab is portable and requires only human and solar power (to recharge the batteries via a solar backpack), it is also ideal for educational efforts in developing nations. Labs are currently being produced for outreach and donation via three international projects to install water purification systems and/or educational Labs in schools and clinics in Mexico, Lesotho and Swaziland, in collaboration with the Beyond Traditional Borders and Rice 360 health initiatives.
On the Impact of the Addition of Steady Flow to Oscillatory Flow in a Diffuser
Authors: King Cameron V. , Smith Barton L.
Published: July 2009

Separating oscillating and pulsating flows in an internal adverse pressure gradient geometry are studied experimentally. Simultaneous velocity-pressure measurements demonstrate that the minor losses associated with oscillating flow in an adverse pressure gradient geometry can be smaller or larger than for steady flow. The minor losses grow with increasing displacement amplitude in the range 10 < L0/h < 37. Losses decrease with Reδ in the range of 380 < Re < 740. The extent and duration of boundary separation increase with L0/h. It is found that the losses increase with increasing diffuser angle for 12° < θ < 30°. The addition of steady flow can cause the in decrease if the flow becomes more turbulent as a result, or increase when the flow was already turbulent.
Bubble Formation in a DC Electric Field
Authors: Chen Feng , Song Yaozu , Peng Yao
Published: July 2009

The effect of a DC electric field on the formation and the characteristics of a nitrogen bubble injected from an orifice were studied experimentally and theoretically. This study was the first to divide the bubble growth process into four stages (waiting, expansion, deformation and detachment) according to the variation of the bubble shape in order to analyze the bubble behavior in the electric field. During the waiting stage, the waiting interval decreases significantly as the electric field strength rises. In the expansion stage, the minor axis reaches a maximum that decreases with increasing the electric field strength. Within the deformation stage, the major axis achieves its maximum and so does the aspect ratio. As the electric field strength rises, both the maximums of the major axis and the aspect ratio increase. At the detachment stage, as the electric field strength is intensified, the major axis lengthens, the minor axis shortens and the aspect ratio lengthens. From the waiting stage to the detachment stage, the effect of the electric field on the major axis of the bubble is marginal, while with increasing the electric field strength, the minor axis decreases distinctly and thus the aspect ratio increases. To employ the four-stage model, the bubble growth process was analyzed in detail under the electric field. The electric stress exerted on the bubble surface was calculated. The results show that the electric stress compresses the bubble equator and elongates the poles of the bubble, causing the bubble to elongate along the electric field direction.
Cavitation Damage From an Induced Secondary Vortex
Authors: Moeny M. , Weldon M. , Stinebring D. , Straka W. , Pierzga M.
Published: July 2009

This paper will present the results from a water tunnel investigation of cavitation damage from a secondary flow induced by the interaction between a non-cavitating vortex and a fin at angle of attack. The experimental setup will be presented along with images illustrating the phenomenon. A hypothesis for the generation of the secondary flow cavitation will be proffered along with results of a preliminary mitigation scheme.
Rotordynamic Forces Acting on Three-Bladed Inducer Under Super-Synchronous/Synchronous Rotating Cavitation
Authors: Yoshida Yoshiki , Eguchi Masato , Motomura Taiichi , Uchiumi Masaharu , Kure Hirotaka , Maruta Yoshiyuki
Published: July 2009

Asymmetric cavitation, in which cavity lengths are unequal on each blade, is known as a source of cavitation induced shaft vibration in turbomachinery. To investigate the relationship of the uneven cavity length and rotordynamic force in a cavitating inducer with three blades, we conducted two experiments. In one, the growth of cavity unevenness at the inception of synchronous rotating cavitation in cryogenic flow was observed, and in the other, the rotordynamic fluid forces in water were examined by using a rotordynamic test stand with active magnetic bearings. Rotordynamic performances were obtained within a wide range of cavitation numbers and whirl/shaft speed ratios included super-synchronous/synchronous rotating cavitation. These experimental results indicate that the shaft vibration due to the rotating cavitation is one type of self-excited vibrations arising from the coupling of cavitation instability and rotordynamics.
A Numerical Study on Flow Boiling in Parallel Microchannels
Authors: Jeon Jinho , Lee Woorim , Suh Youngho , Son Gihun
Published: July 2009

Flow boiling in parallel microchannels has received attention as an effective cooling method for high-power-density microprocessor. Despite a number of experimental studies, the bubble dynamics coupled with boiling heat transfer in microchannels is still not well understood due to the technological difficulties in obtaining detailed measurements of microscale two-phase flows. In this study, complete numerical simulation is performed to further clarify the physics of flow boiling in microchannels. The level set method for tracking the liquid-vapor interface is modified to include the effects of phase change and contact angle. The method is further extended to treat the no-slip and contact angle conditions on the immersed solid. Also, the reverse flow observed during flow boiling in parallel microchannels has been investigated. Based on the numerical results, the effects of channel shape and inlet area restriction on the bubble growth, reverse flow and heat transfer are quantified.
Influence on the Axial Flow Fan Aerodynamic Characteristic Due to an Introduction of Internal Secondary Flow
Authors: Eberlinc Matjazˇ , Sˇirok Brane , Hocˇevar Marko , Dular Matevzˇ
Published: July 2009

Axial fans often show adverse flow conditions at the fan hub and at the tip of the blades. Modification of conventional axial fan blades is presented. Hollow blades were manufactured from the hub to the trailing edge at the tip of the blades. Hollow blades enabled the formation of self-induced internal flow through internal passages. The internal flow enters the internal radial flow passages of the hollow blades through the openings near the fan hub and exits through the tip trailing edge slots. Study of the influence of internal flow on the flow field of axial fan and modifications of axial fan aerodynamic characteristics is presented. The characteristics of the axial fan with the internal flow were compared to characteristics of a geometrically equivalent fan without internal flow. The results show integral measurements of performance testing using standardized test rig, and the measurements of local characteristics. The measurements of local characteristics were performed with a hot-wire anemometry, five-hole probe and computer-aided visualization. We attained reduction of adverse flow conditions near the blade tip trailing edge, boundary-layer reduction on the blade suction side and reduction of flow separation. Introduction of the self-induced blowing led to the preservation of external flow direction, defined by blade geometry and enabled maximal local energy conversion. The integral characteristic reached higher degree of efficiency.
Euler-Euler Large-Eddy Simulation Approach for Non Isothermal Particle-Laden Turbulent Jet
Authors: Masi Enrica , Be´dat Benoiˆt , Moreau Mathieu , Simonin Olivier
Published: July 2009

This paper presents an Euler-Euler Large-Eddy Simulation (LES) approach for the numerical modeling of non isothermal dispersed turbulent two-phase flows. The proposed approach is presented and validated by a priori tests from an Euler-Lagrange database, provided using discrete particle simulation (DPS) of the particle phase coupled with direct numerical simulation (DNS) of the turbulent carrier flow, in a non isothermal particle-laden temporal jet configuration. A statistical approach, the Mesoscopic Eulerian Formalism (MEF) [Fe´vrier et al., J. Fluid Mech., 2005, vol. 533, pp. 1–46], is used to write local and instantaneous Eulerian equations for the dispersed phase and then, by spatial averaging, to derive the LES equations governing the filtered variables. In this work, the MEF approach is extended to scalar variables transported by the particles in order to develop LES for reactive turbulent dispersed two-phase flows with mass and heat turbulent transport. This approach leads to separate the instantaneous particle temperature distribution in a Mesoscopic Eulerian field, shared by all the particles, and a Random Uncorrelated distribution which may be characterized in terms of Eulerian fields of particle moments such as the uncorrelated temperature variance. In this paper, the DPS-DNS numerical database is presented, LES Eulerian equations for the dispersed phase are derived in the frame of the Mesoscopic approach and models for the unresolved subgrid and random uncorrelated terms are proposed and a priori tested using the DPS-DNS database.
The Effects of Reynolds Number on the Aerodynamic Performance of Geometrically Similar Fans
Authors: Hanly K. , Grimes R. , Walsh P.
Published: July 2009

The cooling of portable electronic devices has become paramount in the last number of years due to the simultaneous increase in power consumption and reduction in package size. This has lead to an increase in the amount of heat that needs to be dissipated by these devices. Passive cooling techniques will no longer provide an adequate solution and therefore active cooling solutions need to be implemented. The use of miniature radial fans in conjunction with heatsinks is a possible solution. These types of fans are especially suited as they can be deployed in a low profile format. However, little is known about the aerodynamic effects of reducing the fan scale and therefore Reynolds number to the extent necessary for use in portable electronic device cooling. This paper looks to quantify deviation of aerodynamic performance with Reynolds number from that predicted by the fan laws. Before tests were carried out experimental facilities were calibrated. Four radial fans with diameters of 80, 40, 18.3 and 10mm were then tested at a number of different rotational speeds with measurements of pressure rise and flow rates recorded for each of these speeds. The measurements presented show the need for a homogonous experimental setup with the exact conditions replicated each time a test is carried out. Results also show that there is good correlation between the experimental results for pressure rise and flow rate at high Reynolds numbers in accordance with trends from high Reynolds number theory. However at the lower Reynolds numbers a fundamental change in flow phenomena emerges which alters the maximum pressure and flow characteristics.
Flow Property Measurements of Stirred-Tank Flow Across Three Reynolds Number Decades
Authors: Yang Yihong , Yoon Roe-Hoan , Telionis Demetri P. , Weber Asa , Foreman Don
Published: July 2009

The flow in stirred tanks is very complicated because it passes around the rotating impeller blades, interacts with the stationary baffles or stator blades leading to high-intensity turbulence, and then goes through loops and returns to the impeller region. A penetrating understanding of the flow in stirred tanks is necessary for the tank design and optimization, because it could have a significant impact to the overall design characteristics, which will affect directly the production, the quality of the product and the maintenance costs. Despite the recent advances in computational fluid dynamics (CFD), testing still plays a vital role in the development of high-performance stirred tanks. This paper describes measurements and results obtained by traversing a five-hole probe in a 6-m3 stirred tank. The three-dimensional flow field was obtained. The separation region was also detected. The majority of the measurements were conducted in the 6-m3 tank, but unique to this investigation are measurements we have conducted with Pitot tubes in an 160-m3 geometrically-similar full-scale tank. We also have earlier results obtained by Particle Image Velocimetry (PIV) in another geometrically-similar but much smaller tank, namely a 0.1m3 tank. This provides the unique opportunity to explore how such flows scale with size and speed, extending to Reynolds numbers that approach ten million. Some numerical results were also conducted, using the commercial code FLUENT, and the results are presented together with the experimental data.
A Direct Numerical Simulation of the Unsteady Development of a Deformable Rising Bubble in a Quiescent Liquid
Authors: Agarwal Alpana , Tai C. F. , Chung J. N.
Published: July 2009

An accurate finite-volume based numerical method for the simulation of an isothermal two-phase flow, consisting of a deformable bubble rising in a quiescent, unbounded liquid, is presented. This direct simulation method is built on a sharp interface concept and developed on an Eulerian, Cartesian fixed grid with a cut-cell scheme and marker points to track the moving interface. The unsteady Navier-Stokes equations in both liquid and gas phases are solved separately. The mass continuity and momentum flux conditions are explicitly matched at the true phase boundary to determine the interface shape and movement of the bubble. The highlights of this method are that it utilizes a combined Eulerian-Lagrangian approach, and is capable of treating the interface as a sharp discontinuity. A fixed underlying grid is used to represent the control volume. The interface, however, is denoted by a separate set of marker particles which move along with the interface. A quadratic curve fitting algorithm with marker points is used to yield smooth and accurate information of the interface curvatures. This numerical scheme can handle a wide range of density and viscosity ratios. The bubble is assumed to be spherical and at rest initially, but deforms as it rises through the liquid pool due to buoyancy. Additionally, the flow is assumed to be axisymmetric and incompressible. The bubble deformation and dynamic motion are characterized by the Reynolds number, the Weber number, the density ratio and the viscosity ratio. The effects of these parameters on the translational bubble dynamics and shape are given and the physical mechanisms are explained and discussed. Results for the shape, velocity profile and various forces acting on the bubble are presented here as a function of time until the bubble reaches terminal velocity. The range of Reynolds numbers investigated is 1 < Re < 100, and that of Weber number is 1 < We < 10.
Analysis of a Swashplateless Helicopter Rotor With Active Servopaddles
Authors: Brindejonc Anne , Malburet Franc¸ois , Aubourg Pierre-Antoine
Published: July 2009

The present paper describes a novel concept of actively controlled Hiller type servopaddle to achieve rotor primary control. The blades on the swashplateless rotor are coupled to a servopaddle with a piezoelectrically actuated aileron. The aileron commands the paddle pitch which generates a change in the paddle ap angle and blade pitch angle via a mechanical linkage. The system { blade, paddle, aileron} is independent from any other { blade, paddle, aileron} assembly. Therefore, the active servopaddle can create both cyclic and collective inputs. A four degree-of-freedom analysis including aileron dynamics has been developed to predict the dynamic behavior and assess the feasibility of such a swashplateless rotor. The analysis is used to investigate the effect of system parameters on the blade control authority.
Spatiotemporal Development of Transitional Wall Jets
Authors: Raben Samuel , Ng Wing F. , Vlachos Pavlos P.
Published: July 2009

Wall jets have many applications in engineering ranging from active flow control to film cooling. A typical wall jet is characterized by both spatial and temporal variation. Here we use Time Resolved-Digital Particle Image Velocimetry (TR-DPIV) to deliver high spatially and temporally resolved investigation of wall jets across a wide range of Reynolds numbers (150–10,000). We employ Proper Orthogonal Decomposition (POD) to post-process the data and generate low-order models describing the underlying physics. The results show the presence of near wall structures forming at the jet exit and convecting downstream directly influencing the transition to turbulence. Using the time coefficients associated with the POD modes, the frequency content of the individual modes is determined and the mechanism of energy transfer between the modes is quantified. This study provides the first spatiotemporally resolved experimental investigation of the transition to turbulence of a rectangular wall jet.
Cavitation in the Tip Region of the Rotor Blades Within a Waterjet Pump
Authors: Wu H. , Soranna F. , Michael T. , Katz J. , Jessup S.
Published: July 2009

Recent upgrades to the turbomachinery facility at JHU enable measurements of performance, as well as flow structure, turbulence and cavitation within a water-jet pump. The rotor, stator and pump casing in this optically index-matched facility are made of acrylic that has the same optical index of refraction as the working fluid, a concentrated solution of NaI in water. The essentially “invisible” blades allow unobstructed view and access to optical flow measurement techniques. Initial tests in water focus on observations on occurrence of cavitation in the vicinity of the narrow tip-gap. For the present design and operating conditions, near the leading edge, cavitation in the tip corner of the pressure side causes accumulation of bubbles along the pressure side that extends to mid blade. As rollup of a tip vortex starts, these bubbles cross the tip gap to the suction side, and become primary nuclei for cavitation inception within the tip leakage vortex (TLV). Bursting of this tip vortex as it migrates towards the pressure side of the neighboring blade generates a cloud of bubbles along the aft section of the passage. As the flow in the tip gap increases upstream of the trailing edge, cavitation also develops within the gap, along the pressure side corner.
Role of Hydraulic and Capillary Radii in Improving the Effectiveness of Capillary Model in Wicking
Authors: Masoodi Reza , Pillai Krishna M. , Varanasi Padma Prabodh
Published: July 2009

In this paper the liquid absorption under capillary pressure, or wicking, in cylindrical polymer wicks made of sintered polymer beads is studied experimentally and theoretically. Three different polymer wicks (made from Polycarbonate, Polyethylene and Polypropylene) and three different well-characterized liquids (Hexadecane, Decane and Dodecane) are used in the present experimental study. These experimental results are then compared with the predictions of the capillary model. The capillary and hydraulic radii used in the model are found to behave like two independent wicking parameters and are needed to be measured separately to improve the accuracy of the capillary model in predicting wicking in polymer wicks. Accurate measurement of the capillary radius ensured a good prediction by the capillary model of the final steady-state height in the large-pore wicks.
CFD Solution of a Two-Canopy Parachute in a Top-to-Top Formation With a Vent of Air From One of Its Canopy
Authors: Izadi Mohammad J.
Published: July 2009

A CFD study of a 3 Dimensional flow field around two bodies (Two Canopies of a Parachutes) as two bluff bodies in an incompressible fluid (Air) is modeled here. Formations of these two bodies are top-to-top (One on the top of the other) with respect to the center of each other. One canopy with a constant cross sectional area with a vent of air at its apex, and the other with a variable cross sectional area with no vent is studied here. Vertical distances of these two bodies are varied form zero to half, equal, double and triple radius of the body with a vent on it. The flow condition is considered to be 3-D, unsteady, turbulent, and incompressible. The vertical distances between the bluff bodies, cross sectional area, and also vent ratio of bluff bodies are varied here. The drag forces with static pressures around the two bodies are calculated. From the numerical results, it can be seen that, the drag coefficient is constant on the range of zero to twenty percent of the vent ratio and it decreases for higher vent ratios for when the upper parachute is smaller than the lower one, and it increases for when the upper parachute is larger than the lower one. Both Steady and Unsteady cases gave similar results especially when the distance between the canopies is increased.
Laser-Induced Fluorescence Thermometry for Joule Heating in AC Electrokinetic Chips
Authors: Williams Stuart J. , Chamarthy Pramod , Wereley Steven T.
Published: July 2009

AC electrokinetic manipulation of particles and fluids are important techniques in the development of lab-on-a-chip technologies. Most of these systems involve planar microelectrode geometries, generating high strength electric fields. When these fields are applied to a dielectric medium Joule heating occurs. Understanding electrothermal heating and monitoring the temperature in these environments is critical for temperature-sensitive investigations including biological applications. Additionally, significant changes in fluid temperature when subjected to an electric field will induce electrohydrodynamic flows, potentially disrupting the intended microfluidic profile. This work investigates heat generated from the interaction of AC electric fields and water at various electrical conductivities (from 0.92–390 mS/m). The electrode geometry is an ITO electrode strip 20 μm wide and a grounded, planar ITO substrate separated by a 50 μm spacer with microfluidic features. Laser Induced Fluorescence (LIF) is used to measure the experimental changes in temperature. A normalization procedure that requires a single temperature-sensitive dye, Rhodamine B (RhB), is proposed to reduce uncertainty. The experimental electrothermal results are compared to theory and computer simulations.
Experimental Investigations of the Onset of Rotating Stall
Authors: Johansson P. B. V. , Henriksson M.
Published: July 2009

This work focuses on analysis of data obtained in experimental investigations of a military fan in a whole-engine test facility. The data was simultaneously obtained by using multiple pressure sensors located at different axial and angular positions in the fan. In particular, the origin of rotating stall was investigated by analyzing the experimental data both in the frequency-time domain as well as the correlation in time between the typical pressure profile and the pressure profile for each revolution of the rotor. First, the measurement signal was high-pass filtered with a cut-off frequency slightly lower than the spool rotational frequency. These high frequency data were subjected to a typical pressure distribution test. Second, the measurement signal was low-pass filtered slightly lower than the spool rotational frequency. The low frequency part was investigated in the frequency-time domain. A quantitative measurement of an indicator of rotating stall is presented and its limitation for practical use is discussed.
Numerical and Experimental Investigation of Rotor-Stator Interactions in an Axial Turbine: Numerical Interface Assessment
Authors: Gagnon Jean-Mathieu , Ciocan Gabriel D. , Deschenes Claire , Iliescu Monica
Published: July 2009

In this paper, the rotor-stator interaction in an axial hydraulic turbine is studied with the help of a 2D test case and validation with experimental data. The computational method is presented in the first part of the paper along with the results from the shedding flow behind a square cylinder to investigate a numerical interface between non-matching meshes. The turbulent kinetic energy budget and the centerline velocity past the interface are analyzed and compared with literature. In the second part of the paper, knowledge gained from the 2D test case is applied to 3D simulation of a hydraulic turbine model. Potential interactions are studied using FFT of the time signal on different positions upstream and downstream of a sliding mesh interface. The wake dissipation is investigated for several meridional positions downstream of the turbine guide vanes. The numerical flow field is compared against 2D-LDV experimental measurements at the runner outlet. Numerical results are in good agreement with experimental data.
Optical Measurement of Base Film Thickness in Annular Two-Phase Flow
Authors: Schubring DuWayne , Ashwood Andrea C. , Hurlburt Evan T. , Shedd Timothy A.
Published: July 2009

Measurements of the film thickness of annular two-phase air-water flow have been taken using an optical technique that extracts the base film thickness, excluding the input of waves. Both horizontal and vertical conditions have been examined. The technique used, originally developed by Shedd and Newell, uses the pattern of diffuse light reflected from the liquid surface. Two correlations for average base film thickness are provided; one is a purely empirical fit, while the other employs a critical friction factor. An empirical relation for maximum horizontal asymmetry in terms of a Froude number is also provided.
Electrohydrodynamic (EHD) Pump in a Square Channel
Authors: Ngo C. C. , Brown N. M. , Lai F. C.
Published: July 2009

The electrohydrodynamics (EHD) technique has shown promising results in enhancing heat transfer and mass transport. It has endless potential in industrial applications such as drying technology, design of evaporators, condensers, electrostatic precipitator, plasma actuator, and micropumps in microfluidic, chip-integrated cooling, and drug delivery systems. In recent years, a significant amount of research has been directed to design EHD micropumps as researchers realize their attractive features (e.g., no moving part, simple fabrication process) are most suitable in the aforementioned microelectro-mechanical systems (MEMS). This paper evaluates the performance of an EHD pump in a vertical square (4 × 4 inch) channel with a non-intrusive wire-electrode configuration. The voltage and current characteristics of the EHD pump are measured such that numerical simulations can be carried out. Measurements were taken from the corona threshold voltage to the occurrence of sparkover with a 1 kV increment. Due to the corona wind generated, the average volume flow rate in the channel was as high as 10 liter per second subjected to a voltage difference of 25 kV.
Computational Studies on the Behavior of an Interface Separating Two Fluids Under Uniform Electric Field
Authors: Sharifi Payam , Esmaeeli Asghar
Published: July 2009

Direct Numerical Simulations (DNS) are carried out to study the dynamics of a horizontal interface separating two fluids, having different electrical properties, under the influence of a uniform electric field. A front tracking/finite difference scheme is used, in conjunction with Taylor’s leaky dielectric model, to solve the governing electrohydrodynamics equations in both fluids at finite Reynolds numbers. The methodology and the code is validated by comparing the results with those of the analytical studies developed at the linear stability limit and it is shown that a very good agreement exists between the two. The results of this study show interesting interface behavior depending on the parameters of the problem. In all the cases considered, the interface becomes unstable beyond a critical voltage and starts to oscillate as it moves toward its steady-state shape which is a vertical column pointing from the liquid of higher electric conductivity to the one with a lower conductivity. The shape of the column, however, will vary depending on the individual governing parameters.
DNA Hybridization Enhancement in Microarrays Using AC-Electrothermal Flow
Authors: Bottausci F. , Neumann T. , Mader M. A. , Mezic I. , Jaeger L. , Tirrell M.
Published: July 2009

We present numerical and experimental results on an innovative method to enhance the hybridization process in the field of microarray based analytics. Hybridization reaction based on biochip approaches take several hours due to the fact that these reactions are diffusion limited. To monitor the binding of fluorescent labeled analyte molecules to the probe molecules on the chip surface we use a home made fluorescent detection system that allows continues monitoring of the reaction on chip. Mixing is the key to overcome the diffusion barrier and increase reaction rate. We present a novel mixing device that increases reaction time The AC-electrokinetic signal produces an electrothermal flow that enhances the DNA binding. We show an optimization of the AC-signal and the electrodes design based on numerical simulations to obtain highest efficiency in mixing of analyte solutions and we report experimental results on dephosphorylation experiment.
Analysis of Passive Wake Mixing Techniques Using Time Resolved Digital Particle Image Velocimetry
Authors: Weiland Christopher , Michie Christopher , Vlachos Pavlos
Published: July 2009

Wake mixing is a common flow control technique that can be used in a multitude of applications to disrupt undesired flow structures. A Time Resolved Digital Particle Image Velocimetry (TRDPIV) experiment was performed to analyze the wake mixing properties of flow control approaches in the wake of a flat plate. Triangular winglet-type vortex generators, two lobed trailing edge geometries, and trailing edge blowing are examined and quantitative comparisons of their passive wake mixing properties are compared. The TRDPIV fields were analyzed using the Proper Orthogonal Decomposition as a metric for deducing wake coherency. Results indicate that the airfoil geometry plays a significant role in decreasing wake coherency. Additionally, the eigenmodes of the lobed geometries revealed the greatest differences in the dynamics of the flow between the low and high Reynolds number flows. This suggests these geometries are sensitive to the character of the boundary layer incident on the passive flow control devices.
An Improvement of a Cavitation Model and the Application to LES
Authors: Tsuda Shin-Ichi , Tani Naoki , Yamanishi Nobuhiro , Kato Chisachi
Published: July 2009

In this paper, we have improved a cavitation model implemented in “Front Flow/Blue (FFB)”, which is a solver of turbulent flows using the large-eddy simulation (LES) technique with high accuracy. To improve the cavitation model, we have carried out a survey of conventional cavitation models and performed a trade-off between the models based on some evaluation points such as accuracy, achievement, future potential, and computational cost. In the new cavitation model, the surface area of cavitation bubbles in each cell is also solved in addition to the volume fraction of the bubbles. Although the validation is in progress, the new cavitation model is expected to be useful to reproduce a detailed cavitation structure.
Air Entrainment Studies for a Supersonic Micro-Ejector System
Authors: Papadopoulos George , Tyll Jason , Drake Alan , Chue Randy , Williams John D. , Galambos Paul C.
Published: July 2009

Micro-ejectors offer a unique way of entraining relative large quantities of air without any moving parts, which when mixed with fuel can provide the necessary fuel-air mixture to power a micro-combustion system. Together, the micro-ejector and the micro-combustion systems can make up components of a unique air-breathing propulsion system. Larger scale ejector-based propulsion systems that operate a rocket ejector cycle have been constructed and operated in the past, dating back to the 1960s. Only very recently this same ejector system has been scaled down to the micro-size domain for use in applications other than propulsion, more specifically as a way of entraining and mixing fuel and air for use in micro-combustor applications. The present study involved the use of propane as ejector primary fluid, chosen for its high vapor pressure which allowed us to operate a March 2 nozzle with a throat height of 31 microns under high pressure and thus achieve various degrees of air entrainment based on the area ratio between the primary nozzle and ejector secondary duct. Experimental data showed the performance of the ejector system under the various area ratios studied. The degree of mixing of the primary jet is reviewed, specifically as it pertains to air entrainment performance.
The Improved Ultrasonic Flow Measuring Method
Authors: Gryshanova Iryna
Published: July 2009

The well-known transit time ultrasonic flow measuring method is based on determining of the difference in transit time of high frequency sound pulses that are transmitted along and against the flow stream. Having this information, the flowmeter can calculate average flow velocity and then the flowrate. The principle of measurement is simple but determining the true average velocity is difficult, especially to obtain custody transfer measurement accuracy in one-path ultrasonic flowmeters. This paper proposes an improvement of the mentioned flow measuring method. For this purpose it is not necessary to use extra devices complicating a design and causing additional pressure drop. The object in view is achieved by entering necessary correction during flowrate calculation. For that the stage-by-stage estimation of the flow profile correction factor, which considers a difference between average velocity along the sound path and average velocity for pipe cross-section is carried out depending on the flow regime. Correction is based on the offered original processing algorithm which in turn relies on the mathematical model of ultrasonic flowmeter, considering except for velocity distribution profile also influence of a pipeline wall roughness. Thus, even having only one pair of piezoelectric transducers, the improved method allows to increase an accuracy of flow measurement in the wide range covering laminar, transitive and turbulent flow modes.
CFD Simulation of the Whole Pump Station Inlet Flow Field
Authors: Daqing Zhou , Yuan Zheng , Ge Xinfeng
Published: July 2009

Wu-Hao-Gou pump station is one of many pump stations being going to build in order to meet the increasing need of water supply in the Shanghai city. Owing to limited building site, large discharge and multi water outlet direction, the design and arrangement of hydraulic structure become more difficult than usual pump station. In the paper, CFD method is used to simulate the whole inlet flow field and improve hydraulic performance of the pump station. Firstly, the whole hydraulic structure geometric model, combined by Penstock, transition passage, diversion channel, fore bay, suction bay and suction pipe, is built and subdivided with unstructured mesh. Secondly, inlet flow field of the original pump station scheme is simulated and analyzed with the SIMPLEC algorithm, the realizable k-ε turbulence model and the symmetric boundary hypothesis on the free surface. Thirdly, the better scheme is calculated with the same numerical method after taking some effective measurements. Lastly, the better scheme is simulated with the VOF model, as well as the numerical results are compared with the above symmetric boundary hypothesis model to reveal the fact that the main flow character is similar but some flow details differ between the two free surface model. Then, the physical model experiment will be performed to verify the better scheme in the next step.
Structure Vibration of Hydropower House Induced by Francis Turbine Basing on CFD
Authors: Peng Guangjie , Qin Liang , Wang Zhengwei , Tian Huijing , Luo Yongyao
Published: July 2009

The method of CFD is adopted to carry out 3-D unsteady turbulent flow simulation through the whole flow passage of 2# Francis turbine in Wanjiazhai hydropower station. The flow fields of spiral casing, stay vane, guide vane, runner, and tail tube are obtained. The pressure fluctuation of tail tube is also acquired and compared with the prototype test results in time domain and frequency domain. It shows that the numerical results and the experimental results are well identical. On the base, the problems of load distribution in the couple boundary between flow field of turbine and structure field of house and of hydraulic load transferring to machinery foundation by shaft are investigated. Consequently it achieves dynamic analogy of hydraulic load in hydropower house FEM analysis successfully. It provides method of analyzing hydropower house vibration accurately.
CFD-Based Match Design and Improving Performance for Francis Turbine Components
Authors: Guo Pengcheng , Luo Xingqi , Zheng Xiaobo , Liu Shengzhu
Published: July 2009

The CFD-based design tool is applied to investigate and improve the flow matching relationship and the hydraulic performance of Francis turbine components for a turbine rehabilitation project. At first numerical analysis of spiral casing with stay vanes was performed, the discharge angle distribution at the spiral casing outlet was obtained and according to the discharge angle distribution, the stay vanes were divided into 5 groups to correspond with the spiral casing discharge angle distribution. The circumferential relative position relationship between the stay vanes and the guide vanes was numerical investigated by altering the circumferential position of the stay vane, and the optimal matching relationship between the stay vane outflow angle and the guide vane inflow angle was obtained. Systemic measures of adopting negative rake angle blades, increasing blade number, increasing blade wrap angle, thickening blade exit edge, and reducing optimum unit speed were used to develop a new runner that replaced existing runner to damp the vibration of turbine units. And the model test comparison in the same conditions of the new runner and existing runner was carried out and the results showed that the severe vibration of the power building floor was eliminated.
Numerical Study of the Pulsating Flow at the Tongue Region of a Centrifugal Pump for Several Flow Rates
Authors: Barrio Rau´l , Parrondo Jorge , Blanco Eduardo , Ferna´ndez Joaqui´n
Published: July 2009

A numerical study is presented on the unsteady flow at the tongue region of a single suction volute-type centrifugal pump with a specific speed of 0.46. The flow through the pump, available at laboratory, was simulated by means of a commercial CFD software that solved the Reynolds averaged Navier-Stokes equations for three-dimensional unsteady flow (3D-URANS). A sensitivity analysis of the numerical model was carried out and the numerical predictions were compared with previous experimental results of both global and unsteady variables. Once validated, the model was used to study the flow pulsations associated to the interaction between the impeller blades and the volute tongue as a function of the flow rate, from partial load to overload. The study allowed relating the passage of the impeller blades with the tangential and radial velocity pulsations at some reference positions and with the pressure pulsations at the tongue region.
Two-Objective Shape Optimization of Sewers
Authors: Karvinen T. , Karvinen R.
Published: July 2009

Hydraulic characteristics of different sewer shapes are studied. The sewer must carry a very large flow rate for example in storm conditions, but most of the time there is very little flow at the bottom. This causes sedimentation of particles, which is avoided by having a high flow velocity. These are contradicting objectives in sewer design and therefore yield a multi-objective optimization problem. It is shown using a shape optimization procedure, that hydraulic characteristics of existing sewers can be improved. Using the optimization scheme, the Pareto-optimal solution of a shape optimization problem is found, for which the objectives are maximizing the flow velocity at low flow rates and maximizing the volume flow rate when the sewer is full. If the volume flow rate is to be maximized, almost a square cross-section is the best and the lower part of the sewer is very narrow if the velocity at the bottom is to be maximized. Hydraulic characteristics of sewers of different shapes are compared. In order to obtain optimal results in a reasonable time, an analytical treatment using the Manning formula is adopted and its results are compared with a numerical solution. Traditionally, in this kind of analysis the friction factor in the Manning formula is assumed constant. The validity of this assumption is confirmed using numerical modeling of flow (CFD).
Numerical Study of Turbulence Models in the Computation of Blood Flow in Cannulas
Authors: Salazar Felix A. , Rojas-Solo´rzano Luis R. , Antaki James F.
Published: July 2009

In recent years, CFD has become an increasingly used tool in the design of blood-based devices. However, the estimation of red blood cells damage (hemolysis) remains a very important challenge due to the complex rheology of blood and the turbulence present in most pumping devices. The objective of this study was to identify an appropriate turbulence model suitable for predicting hemolysis in Hemodialysis cannula. Several modern turbulence models were evaluated in comparison to Direct Numerical Simulation (DNS), which was used as the gold standard. The fluid dynamics in the cannula was modeled as a coaxial jet in which Reynolds’ number approached 2800. Based on comparison of velocity and stress time-averaged profiles, the Shear Stress Transport (SST) model with Gamma-Theta transition was identified as an optimal compromise between accuracy and computational cost.
Spatiotemporally-Resolved Dynamics of Dispersing Ferrofluid Aggregates
Authors: Williams Alicia M. , Vlachos Pavlos P.
Published: July 2009

Ferrohydrodynamics research has been approached predominantly from either numerical or basic experimental techniques. However, to date, these experimental techniques have been limited to ultrasonic point measurements or shadowgraphs due to the opacity of the ferrofluids. As a result, the complete dynamics of many ferrohydrodynamics flows have remained unexplored. In this work, Time Resolved Digital Particle Image Velocimetry (TRDPIV) is employed to fully resolve the dynamic interaction of ferrofluid aggregates with bulk nonmagnetic fluids. This topic is hydrodynamically rich, where shearing between the aggregate and bulk flow develop into the Kelvin-Helmholtz instability. Ferrofluid aggregates are mixed with fluorescent particles in order to enable visualization of the internal flow structure of the aggregate and generate quantitative velocity measurements. The TRDPIV measurements are made in a 15 mm square channel where ferrofluid retained by a 0.5 Tesla permanent magnet is studied as it disperses. The effects of both steady and pulsatile flows are quantified, as are the impact of varying the magnetic field gradients. In both steady and pulsatile flows, a recirculation region is observed within the ferrofluid, driven by the shear layer between the bulk flow and aggregate interface. The interaction of the aggregate with the flow is also governed by the aggregate height relative to that of the test section. Higher, larger aggregates are less stable, and therefore, more likely to be dispersed by the bulk flow. As the aggregate diminishes in size, it is both more stable and is less subject to shearing forces from the flow. Flow pulsatility enriches the dynamics of the flow and generates complex flow structures resulting from interaction between the aggregate and bulk flow. This work is the first to explore the rich spatiotemporal behavior of dispersing ferrofluid aggregates interacting with steady and unsteady bulk flows.
Numerical Evaluation and Comparison of Different Reduced Mechanisms for Predicting the Performance of a SOFC Operating on Coal Syngas
Authors: Elizalde-Blancas Francisco , Pakalapati Suryanarayana R. , Escobar-Vargas Jose A. , Celik Ismail B.
Published: July 2009

Three-dimensional numerical simulations of an anode supported button solid oxide fuel cell were performed using the code developed in house DREAM SOFC. The cell operates on coal syngas at atmospheric pressure and 1073 K. A gas phase mechanism and a heterogeneous mechanism are studied in this work to assess their influence on the performance of the button cell. Both mechanisms take into account the steam methane reforming reaction and water gas shift reaction. The implemented electrochemistry model allows the cell to simultaneously electrochemically oxidize H2 and CO. Results show that methane reforming from the bulk reactions is negligible compared to the catalyzed reactions. Also with a higher reformation the power delivered by the cell is improved. A small temperature difference of one degree is observed when both mechanisms are compared. The electrochemistry model does not require the ratio between current produced from H2 and CO to be prescribed a priori as an input. Under the operating conditions used in this study the model predicts the ratio to be around 4 for both mechanisms.