bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of Thermosyphon to Cool the Cutting Tip of a Drill
Authors: Jen Tien-Chien , Tuchowski Fern , Chen Yau-Min
Published: March 2009

This paper investigates using a thermosyphon in the center of a drill to move the heat generated at the cutting tip to the drill chuck in an effort to reduce the temperature at the drill tip. This study compared the heat transfer performance of a drill with a thermosyphon to the performance of a solid drill and a drill with a heat pipe under simulated drilling conditions. Results show that when using a drill with a thermosyphon the temperature of the drill tip was almost 60% lower than a solid drill for 45 and 55 volts and 37% lower for 35 volts. Compared to a drill with a heat pipe the maximum temperatures were reduced 18% to 36%. It was also shown that higher speed has an adverse effect on the operation of the thermosyphon, but in the worst case, the temperature increased by only 16%.
Will RANS Survive LES? A View of Perspectives
Authors: Hanjalic´ K.
Published: March 2009

The paper provides a view of some developments and a perspective on the future role of the Reynolds-averaged Navier-Stokes (RANS) approach in the computation of turbulent flows and heat transfer in competition with Large-eddy simulations (LES). It is argued that RANS will further play an important role, especially in industrial and environmental computations, and that the future increase in the computing power will be used more to utilize advanced RANS models to shorten the design and marketing cycle rather than to yield the way to LES. We also discuss some current and future developments in RANS aimed at improving their performance and range of applicability, as well as their potential in hybrid approaches in combination with the LES strategy. Limitations in LES at high Reynolds (Re) and Rayleigh (Ra) number flows and heat transfer are revisited and some hybrid RANS/LES routes are discussed. The potential of very large eddy simulations (VLES) of flows dominated by (pseudo)-deterministic eddy structures, based on transient RANS (T-RANS) and similar approaches is discussed and illustrated in an example of “ultra-hard” (very high Ra) thermal convection.
Measurements of Pressure Distribution in a Cavity Flow by Integrating the Material Acceleration
Authors: Liu Xiaofeng , Katz Joseph
Published: March 2009

In turbulence research, the velocity-pressure-gradient tensor in the Reynolds stress transport equation is critical for understanding and modeling of turbulence. Pressure is also of fundamental importance in understanding and modeling of cavitation. Motivated by the lack of experimental tools to measure the instantaneous pressure distribution away from boundaries, the paper introduces a non-intrusive method for simultaneously measuring the instantaneous velocity and pressure distribution over a sample area. The technique utilizes four exposure PIV to measure the distribution of material acceleration, and integrating it to obtain the pressure distribution. If necessary, e.g., for cavitation research, a reference pressure at a single point is also required. Two cameras and perpendicularly polarized Nd:Yag lasers are used for recording four exposures on separate frames. Images 1 and 3 are used for measuring the first velocity distribution, whereas images 2 and 4 give the second velocity map. The material acceleration is calculated from the velocity difference in sample areas shifted relative to each other according to the local velocity. Averaged omni-directional integration of the material acceleration over the entire flow field, while avoiding regions dominated by viscous diffusion, provides the pressure distribution. To improve the accuracy of the acceleration measurement, cross-correlation of the corresponding image correlation maps is implemented in areas with high velocity gradient. Applications of these procedures to synthetic flows show that the standard deviation of the measured instantaneous pressure from the theoretical value is about 2%. The system has been used to measure the instantaneous pressure and velocity distributions of a 2D cavity flow field in a water tunnel. Three pressure transducers mounted at different locations on the wall are being used for comparison and calibration. Detailed measurements of acceleration, vorticity and pressure distributions within the cavity shear layer indicate that the cavity shear layer flow exhibits highly unsteady behavior due to the self-excited oscillation.
DNS of the Near-Wall Heat Transfer in the Flume and Channel
Authors: Bergant Robert , Tiselj Iztok
Published: March 2009

Direct Numerical Simulation (DNS) of fully developed turbulent flow in a flume and channel was used to study the heat transfer near the wall. Two different geometries for numerical simulations of turbulent heat transfer in infinite channel and flume were used. Reynolds number based on friction velocity, channel half height (or flume height) and kinematic viscosity was set to Reτ = 170.8, whereas the Prandtl number was set to unity, Pr = 1. The computational domain of 2146×341.6×537 wall units and 2146×170.8×537 wall units was used for channel geometry and flume geometry, respectively. Comparison of these two different geometries with the same physics, were highlighted and discussed.
Computational Investigations of Pyrolysis in Porous Media: Impact of Heat and Mass Transfer
Authors: Biotteau Emilie , Plourde Fre´de´ric , Doan Son Kim , Lambelin Jean-Pierre
Published: March 2009

The present paper deals with impact of heat and mass transfer on pyrolysis mechanisms in a porous media. Importance of porous medium anisotropy is addressed by using a two-dimensional simulation of the problem. To do so, the energy equation is discretized in space by a central differencing while modeling of mass transfer is based on pressure instead of velocity formulation. The kinetics is assumed to follow the lumped-parameter model which is mainly described by a three competitive reactions scheme. Results shed light on the role of grain over the pyrolytic behavior. The grain structure is found to strongly affect heat conduction as well as flows of volatile products through the pores.
Thermal Conductivities of Individual Tin Dioxide Nanobelts
Authors: Shi Li , Hao Qing , Yu Choongho , Mingo Natalio , Kong Xiangyang , Wang Zhong Lin
Published: March 2009

We have measured the thermal conductivities of a 53-nm-thick and a 64-nm-thick tin dioxide (SnO2) nanobelt using a microfabricated device in the temperature range of 80–350 K. The uncertainty of the measurement result was estimated to be 10 percent. The thermal conductivities of the nanobelts were found to be significantly lower than the bulk values, and agree with our calculation results using a full dispersion transmission function approach. Comparison between measurements and calculation suggests that phonon-boundary scattering is the primary effect determining the thermal conductivities.
A Three-Dimensional Numerical Analysis Code for Shipping Water on Deck Using a Particle Method
Authors: Shibata K. , Koshizuka S. , Oka Y. , Tanizawa K.
Published: March 2009

A three-dimensional numerical analysis code for shipping water on deck was developed using MPS (Moving Particle Semi-implicit) method [1–2]. MPS is a particle method for incompressible flows. A ship motion model was developed using the particle method. Shipping water was analyzed using this code. The fluid behavior, the waveform of pressure, and the time integration of pressure on an imitated deck were in agreement with experiment. A visualization system for calculation result was also developed.
Numerical Simulations and Experimental Study of Hot Core Distortion Phenomenon in Aluminum Casting
Authors: Bakhtiyarov Sayavur , Overfelt Ruel A. , Suryawanshi Amit , Capps Johnathon
Published: March 2009

This paper presents the results of experimental and numerical studies of hot distortion phenomenon in the phenolic urethane cold box systems. Dual Pushrod Dilatometer has been used to measure a thermal expansion/contraction of phenolic urethane cold box sand core specimens at temperature range from 25° C to 800° C. The high temperature tensile tests showed that the tensile strength of the phenolic urethane cold box silica sand cores is significantly affected by the bench life, temperature and binders level. High temperature hot distortion furnace tests on cylindrical cores showed that some aluminum coatings increase the temperature limit when distortion starts, but can’t prevent it. The hot distortion test aluminum castings showed that regardless of the application of coating, the type of coating, and anti-veining additives, all cores (silica sand) with density less than the density of the molten metal (aluminum alloy) were significantly distorted. Numerical simulations of the liquid metal flow around the cylindrical sand core and analysis of dynamic forces acting on the core during fill process showed that a buoyancy force is the major contributor to the hot distortion. It is concluded that the one of the solutions in preventing the hot distortion of sand cores is increasing their weigh, which will balance the buoyancy force and will bring the resultant force to the minimum. The hot distortion test castings using zircon sand cores (both coated and non-coated) with density almost equal to the density of the molten aluminum proved our predictions, and hot distortion has been prevented.
Numerical Simulation for Mixed Convective Flow Over a Three-Dimensional Horizontal Backward Facing Step
Authors: Barbosa Saldana J. G. , Anand N. K. , Sarin V.
Published: March 2009

Laminar mixed convective flow over a three-dimensional horizontal backward-facing step heated from below at a constant temperature was numerically simulated using a finite volume technique and the most relevant hydrodynamic and thermal features for air flowing through the channel are presented in this work. The channel considered in this work has an aspect ratio AR = 4, and an expansion ratio ER = 2, while the total length in the streamwise direction is 52 times the step height (L = 52s) and the step length is equal to 2 times the step height (l = 2s). The flow at the duct entrance was considered to be hydro-dynamically fully developed and isothermal. The bottom wall of the channel was subjected to a constant high temperature while the other walls were treated to be adiabatic. The step was considered to be a thermal conductive block.
Design and Testing of a Natural Convection Experimental Setup on the External Surface of Heated Inclined Cylinders With a Constant Heat Flux Boundary Condition: Tests for Naked Cylinders
Authors: Sa´nchez Baquerizo Jaime Antonio , Duque Rivera Jorge W.
Published: March 2009

An experimental setup for natural convection heat transfer from inclined heated cylinders with a constant heat flux boundary condition has been designed and tested for various heat fluxes and inclination angles. For the horizontal cylinder experiment the results are in good agreement with [2] within the range of Ra* (1E5 to 1E6). For the variable inclination experiments, comparisons were made with a correlation available for inclined isothermal cylinders [1]. It was observed, that although the boundary conditions that have been compared are different, the decreasing tendency of the Nusselt number holds as the inclination of the cylinder increases. The results have been correlated in an experimental equation shown at the end of this paper.
Condensate Retention Model for Plain-Fin Heat Exchangers
Authors: ElSherbini A. I. , Jacobi A. M.
Published: March 2009

A model has been developed for predicting the amount of condensate retained as drops on the air-side of heat exchangers operating under dehumidifying conditions. For a coil with a given surface wettability, characterized by the advancing contact angle, the maximum diameter for a retained drop is obtained from a balance between gravitational and surface tension forces. A logarithmic function is used to describe the size-distribution of drops on fins, based on the fraction of fin-area covered by liquid. The volumes of individual drops are calculated by a geometric method for approximating the three dimensional shapes of drops on vertical and inclined surfaces. The total volume of condensate accumulated on a coil is then found by multiplying the size-distribution and volume functions and integrating over all drop diameters. The model is successful in predicting measurements by other researchers of the mass of condensate retained on plain-fin heat exchangers.
Particle Sizing Using Laser Diffraction
Authors: Jawad Badih A. , Riedel Chris H. , Bazzari Ahmad
Published: March 2009

The laser diffraction technique constitute an easy and fast on line measurement of drop sizes. Based on the well known theory of diffraction, a laser diagnostic technique is described for the measurement of droplet size distribution. Limitations of the technique are studied to identify accuracy of measurements when applied to dense sprays (i.e. diesel fuel). Drop size measurements are then conducted for different diesel fuel under different conditions of injection and chamber pressures. Results lead to better understanding of the atomization process.
A Minichannel Heat Exchanger System for Heating, Boiling, and Superheating Water by Radiant Combustion
Authors: Sawyer Mikel L. , Shaaban Aly H. , Salavani Reza
Published: March 2009

A minichannel steam generator is being developed for a fuel reformer. The reformer will convert jet fuel to a hydrogen-rich stream for a 10 kW fuel cell. A first model has been built and tested. It was a once-through design with of two sequential heat exchangers. Exhaust gases produced saturated liquid in the first unit. The second surrounded a radiant propane burner. The system heated 1.2 to 2.6 gm/s of de-ionized water to more than 650 °C at exit pressures from 106 to 240 kPa. These flows and temperatures meet the requirements for the 10 kW fuel reformer. The minichannel system operated across three regimes: liquid heating, boiling, and superheating. It used multiple channels in parallel. At certain locations, the number of the parallel channels was changed to restrain the total pressure drop. The channel hydraulic diameter was 0.14 cm. The Reynolds number for the water ranged from 620 to 1,260 in the boiling section and from 1,260 to 3,140 in the superheating section, based on averaged fluid properties. The total pressure drop in the heat exchanger pair ranged from 470 to 870 kPa. The water absorbed heat fluxes ranging from 0.3 to 1.2 W/cm2 in the single-phase regions and 4.7 to 9.8 W/cm2 in the boiling region. These values were based on the wetted wall area. The boiling data falls in the range of published results for similar mass flux. An increased capacity for absorbing heat flux was demonstrated as coolant mass flux or Reynolds number increased. This paper also discusses the reasons for calculating heat flux based on heated area and based on wetted channel area. The need to identify clearly the basis of heat flux is addressed.
3D Quasi-Unsteady Flow Simulation in a Centrifugal Pump: Comparison With the Experimental Results
Authors: Asuaje Miguel , Bakir Farid , Tremante Andres , Noguera Ricardo , Rey Robert
Published: March 2009

A 3D-CFD simulation of the impeller and volute casing of a centrifugal pump has been performed using commercial codes CFX 5.5 and CFX-TASCflow 2.12. The pump has an specific speed of 32 (metric units) and an outside impeller diameter of 400 mm. First, a 3D-flow simulation for the isolated impeller with a structured grid is presented. A sensitivity analysis regarding grid quality and turbulence models were also performed. A 3D quasi-unsteady flow simulation of the impeller-volute assembly is presented, as well. This flow simulation was carried out for several impeller blades and volute tongue relative positions. As a result, the radial thrust on the pump shaft were calculated for different flow rates. Experimental test were carried out in order to compare theoretical pressure fluctuations with the experimental ones measured by various unsteady pressure sensors placed on the impeller shroud and volute. The qualitative and quantitative results ratify numerical predictions.
Rayleigh-Taylor Instability Mechanism on Sonoluminescing Bubble
Authors: Karng Sarng Woo , Lee Yoon Pyo , Kwak Ho-Young
Published: March 2009

Air bubble trapped in water emits light stably at its collapse point when proper forcing amplitude and frequency of ultrasound are applied to the bubble. We investigated the Rayleigh-Taylor instability mechanism that causes deviation from sphericity of wall of the bubble at the collapse point in the sonoluminescence (SL) regime with rigorous analytical treatment. Our study revealed that the RT instability due to the bubble wall acceleration occurs when the gas density inside bubble exceeds a certain limit. Lagging motion of bubble to the ultrasound due to the viscoelastic behavior of bubble rather than viscous damping was a crucial parameter in determining the upper threshold of SL. The calculation results for the upper limit of stable sonoluminescence regime agreed well with experimental data.
Models and Experiments for Laminar Natural Convection From Heated Bodies in Enclosures
Authors: Teertstra Peter M. , Yovanovich M. Michael , Culham J. Richard
Published: March 2009

A combined experimental and analytical study of natural convection heat transfer in the enclosure formed between a convex shaped, isothermal heated body and its concave shaped, surrounding isothermal enclosure is presented. An experimental test program is conducted at atmospheric and reduced pressure conditions using a transient measurement technique for various enclosure configurations, including concentric cubes, cube-in-sphere, sphere-in-cube, and other geometries. Measurements are reported for a wide range of Rayleigh number, including the diffusive limit. An analytical modeling procedure is developed based on a composite solution of three asymptotic relationships, the conduction limit, the laminar boundary layer and transition flow convective limits. The composite model is in excellent agreement with the data, with an average RMS difference of 2–7% for all enclosure configurations and test conditions.
Computational Fluid Dynamics-Heat Transfer Meshless Control Volume Method
Authors: Arefmanesh Ali , Najafi Mohammad , Abdi Hooman
Published: March 2009

A novel meshless numerical technique to solve computational fluid dynamics-heat transfer problems is introduced. The theory behind the newly proposed technique hereafter named “The Meshless Control Volume Method” is explained and a number of examples illustrating the implementation of the method is presented. In this study, the technique is applied for one and two dimensional transient heat conduction as well as one and two dimensional advection-diffusion problems. Compared to other methods including the exact solution, the results show to be highly accurate for the considered cases. Being a meshless technique, the control volumes are arbitrary chosen, and they posses simple shapes which contrary to the existing control volume methods can overlap. The number of points within each control volume and, therefore the degree of interpolation can be different throughout the considered computational domain. Since the control volumes are of simple shapes, the integrals can be evaluated analytically.
Performance Comparison of Heat-Driven and Electric-Driven Ammonia Heat Pump Systems
Authors: Elgowainy Amgad , Shelton Samuel , Hogan James
Published: March 2009

The objective of this study is to evaluate the solid sorption technology for residential cooling applications. The solid sorption technology uses natural gas as the primary energy source for compressing and circulating the refrigerant in the air-conditioning system. The system delivered 6.7 kW of cooling at 35°C outdoor temperature. The cooling gas COP was 0.32 at 27.8°C outdoor temperature. An ammonia vapor compression system was established and tested by operating a steady state mechanical compressor in place of the cyclic thermal compressor to evaluate and verify the cyclic performance of the sorption system. The system’s thermal compressor efficiency was almost one-third that of the mechanical compressor based on the input power of the primary energy source for each compressor. The testing revealed that the cooling capacity at the air handler is about 1.75 kW less than that at the ammonia/glycol evaporator chiller due to parasitic power gains.
Design of Air and Liquid Cooling Systems for Electronic Components Using Concurrent Simulation and Experiment
Authors: Icoz T. , Verma N. , Jaluria Y.
Published: March 2009

The design of cooling systems for electronic equipment is getting more involved and challenging due to increase in demand for faster and more reliable electronic systems. Therefore, robust and more efficient design and optimization methodologies are required. Conventional approaches are based on sequential use of numerical simulation and experiment. Thus, they fail to use certain advantages of using both tools concurrently. The present study is aimed at combining simulation and experiment in a concurrent manner such that outputs of each approach drives the other to achieve better engineering design in a more efficient way. In this study, a relatively simple problem involving heat transfer from multiple heat sources, simulating electronic components, located in a horizontal channel was investigated experimentally and numerically. Two experimental setups were fabricated for air and liquid cooling experiments to study the effects of different coolants. De-ionized water was used as the liquid coolant in one case and air in the other. The effects of separation distance and flow conditions on the heat transfer and fluid flow characteristics were investigated in details for both coolants. Cooling capabilities of different cooling arrangements were compared and the results from simulations and experiments were combined to provide quantitative inputs for the design. The domains over which experimental or the numerical approach is superior to the other are determined. Simulations are used to guide the experiments and vice versa. It is found that the proposed optimization methodology can be implemented in the design of cooling systems for electronic components for faster and more efficient convergence. This methodology can also be extended to more complex and practical electronic systems.
Interaction of a Cold Wall Jet With a Natural Convective Flow in a Confined Opened Cavity
Authors: Couton D. , Marchal F. , Doan-Kim S. , Tanguy Ch.
Published: March 2009

The aim of this experiment was to analyze the interaction and the development of two flows in the rectangular confined cavity described in this paper. The first was a forced convective flow generated by injecting air at low temperatures inside the cavity in a horizontal direction through an opened area located in the cavity front. Inside this cavity, a natural convective plume was developed simultaneously. Different experimental techniques were used in order to describe either the mean and fluctuating air flow or the mean and fluctuating temperature field, and also to analyze the interaction between these two flows. Firstly, our set-up was validated with the free jet configuration: we obtained a well-known three-dimensional turbulent free jet. Without plume, analysis of the results showed that injection flow behavior corresponded to a characteristic 3D wall jet along the upper wall, with an 15400 injection Reynolds number. The Coanda effect maintained the jet along the upper wall. We determined the parameters of the main velocity law in relation to those detailed in the literature. After that, the main flow developed simultaneously in the longitudinal and vertical directions, so that a recirculation zone appeared. With the plume that developed over an obstacle, we observed that cold flow behavior changed, because of the combination of some of the main parameters: geometrical parameters, injection Reynolds number and temperature gradient between injected flow and plume. For example, with an injection Reynolds number equal to 15400, we measured the influence of the plume on the main flow through the changes in the dynamic and temperature profiles. Three regimes were obtained: the main flow was maintained and no natural convective plume was observed; the transitional regime was characterized by the main flow development along the obstacles, in spite of the development of the natural convective plumes; the natural convective flow modified the wall jet and unsteady classical natural convective “mushrooms” were observed. The topical results deal with the parametric study. We worked on a critical number characterizing the mixture of the jet and the plume. This number is defined as the ratio of the Grashof number to the Reynolds number of the mixture flow. When this critical value was exceeded, the natural convective plume was able to stop the inlet wall jet.
Surface Tension Evaluation Via Thermodynamic Analysis of Statistical Data From Molecular Dynamics Simulations
Authors: Wemhoff Aaron P. , Carey Van P.
Published: March 2009

Surface tension determination of liquid-vapor interfaces of polyatomic fluids using traditional methods has shown to be difficult due to the requirement of evaluating complex intermolecular potentials. However, analytical techniques have recently been developed that determine surface tension solely by means of the characteristics of the interfacial region between the bulk liquid and vapor regions. A post-simulation application of the excess free energy density integration (EFEDI) method was used for analysis of the resultant density profile of molecular dynamics (MD) simulations of argon using a simple Lennard-Jones potential and diatomic nitrogen using a two-center Lennard-Jones potential. MD simulations were also run for an approximation of nitrogen using the simple Lennard-Jones potential. In each MD simulation, a liquid film was initialized between vapor regions and NVE-type simulations were run to equilibrium. The simulation domain was divided into bins across the interfacial region for fluid density collection, and the resultant interfacial region density profile was used for surface tension evaluation. Application of the EFEDI method to these MD simulation results exhibited good approximations to surface tension as a function of temperature for both a simple and complex potential.
Application of Laser Interferometry for Transient Film Thickness Measurements
Authors: Kelly-Zion Peter , Collins William , Glawe Diana
Published: March 2009

A laser interferometry technique for making transient measurements of film thickness of the order of 10 to more than 1000 μm is described. The basis for these measurements was reported previously [1] but the technique was applied to solid glass slides and a slowly thinning silicone oil film. The current work describes an adaptation of the technique for the measurement of rapidly changing film thickness, as occurs with evaporating films. A beam from a helium-neon laser is focused on the film at an oblique angle. Some of the laser light is reflected off of the top surface of the film and some is reflected off of the bottom surface. The light reflected from the two surfaces forms a concentric interference fringe pattern which is projected onto a screen and recorded by a high-speed camera. The film thickness is directly related to the spacing of the fringes. To demonstrate the technique, measurements of the time-varying thickness of three evaporating films are presented and experimental considerations are discussed.
Microconductors on Polymer by Nanoink Printing and Pulsed Laser Curing
Authors: Chung Jaewon , Ko Seunghwan , Grigoropoulos Costas P. , Bieri Nicole R. , Dockendorf Cedric , Poulikakos Dimos
Published: March 2009

In this study, pulsed laser based curing of a printed nanoink (nanoparticle ink) combined with moderate and controlled substrate heating was investigated to create microconductors at low enough temperatures appropriate for polymeric substrates. The present work relies on (1) melting temperature depression of nanoparticles smaller than a critical size, (2) DOD (drop on demand) jettability of nanoparticle ink and (3) small heat affected zone of pulsed laser heating. In the experiment, gold nanoparticles of 3–7nm diameter dissolved in toluene solvent was used as ink. This nanoink was printed on a polymeric substrate which was heated to evaporate the solvent during or after printing. The overall morphology of the gold microline was determined during the printing process and was controlled by changing the substrate temperature during jetting. By employing a micro-second pulsed laser, the nanoparticles were melted and coalesced at a low temperature to form a conductive microline which has 4–5 times higher resistivity than the bulk value without damaging the temperature sensitive polymeric substrate.
Effectiveness of 6-Row Crossflow Heat Exchangers Alternating Circuitry
Authors: Chen Tony D.
Published: March 2009

Air-cooled heat exchangers with six tube rows are commonly seen in air-conditioning systems for large commercial and industry buildings. The analytical solutions of heat exchanger effectiveness for 6-row plate fin-and-tube heat exchangers with alternating circuitries have been derived and expressed explicitly in terms of heat capacity ratio, number of transfer units, and the dimensionless fluid temperature to the inlet of each row and section in this study. This set of exact solutions serve as a basic tool in designing heat exchanger circuitry to its most accurate effectiveness. Comparison of effectiveness between pure and alternating circuiting for 6-row crossflow heat exchangers shows that alternating circuiting could have less effectiveness than pure crossflow with identical circuiting from 1.0 to 7.9% for cases of NTUs range from 1.0 to 3.0 and capacity ratio of 0.5. Nevertheless, alternating circuit has its benefit of lowering the temperature difference between air- and refrigerant-flow, which leads to less pressure drop and less flow maldistribution, therefore resulting in better overall heat exchanger performance.
Geometry Effects on the Flow Rectification of a Dynamic Micro Diffuser: A Numerical Investigation
Authors: Sun Chen-Li , Huang Kun Hao
Published: March 2009

In this study, a numerical investigation is presented to characterize the geometry effects on the transient behaviors of a micro diffuser pump. Four parameters of the dynamic diffuser pump, half-angle, depth, length, and excitation frequency, are considered. A time-dependent sinusoidal pressure with fixed pressure amplitude (200 Pa) is applied at the inlet as the boundary condition. The results from the numerical analysis have been quantified in terms of average volumetric flow rate. Despite the corresponding low Reynolds numbers (Re < 10), circulation is observed for all tested half-angles. When the direction of pressure gradient switches, fluid flows against the pressure gradient and triggers flow separation near wall. The vortex then migrates from wall toward the center of diffuser with time. For 5° ≤ θ ≤ 35°, diffusers with larger half-angles show better rectification effects. For θ gt; 35°, net flow rate is nearly independent of half-angle. Shorter and deeper diffuser results in larger net flow rate regardless of its half-angle. The increase of the excitation frequency diminishes the flow rectification in micro diffuser.
Impact on Shoreline Region by Waves Generated From Submarine and Surface Piercing Slides
Authors: Ciobotaru Remus , Bidoae Razvan , Raad Peter E.
Published: March 2009

The generation of single large waves by a forced motion of solid bodies in a three-dimensional, rectangular channel is investigated. The moving bodies can have simple (idealized) or more complex shapes. The shape and characteristics of the imposed motion are shown to affect the dynamics of the resulting single wave. Waves generated by three different types of landslides are compared by recording the hydrodynamic force and run-up height on a solid plane wall. The three types of landslides investigated are: (i) bottom movement (submarine landslide), (ii) falling mass (partially submerged landslide), and (iii) sliding mass (subaerial landslide).
An Inverse Method Using a Genetic Algorithm to Determine Spatial Temperature Distribution From Infrared Tranmissivity Measurements in a Gas
Authors: Woodbury Keith A. , Graham Courtney , Baker John , Karr Charles
Published: March 2009

The ill-posed nature of inverse problems suggests that a solution be obtained through an optimization method. Genetic algorithms (GAs) effectively locate the global optimum, and are therefore an appealing technique to solve inverse problems. GAs mimic biological evolution, refining a set of solutions until the best solution is found. In this report, a genetic algorithm is developed and demonstrated based on a simple problem of determining the equation of a straight line. Then the GA is modified and implemented to estimate the temperature distribution in a gas based on the measured infrared tranmissivity distribution. The ulitimate task of this inverse method will be determination of the gas composition based on these transmissivity measurements.
An Experimental Investigation of Thermal Stratification in an Underground Water Reservoir
Authors: Dehghan Ali A.
Published: March 2009

Temperature stratification in a long-term underground water reservoir was studied experimentally. The cold water storage tank, which was selected for this study, is an underground water reservoir with a domed shape roof and equipped with wind towers (Baad-Gir) which are responsible for capturing wind from any direction and inducing airflow over the water surface. These historic reservoirs were used as a source of drinking cold water in hot arid central regions of Iran during hot and dry summer season. The cylindrical shape underground reservoir, with 12m in height and 12m in diameter, was filled with 15°C water from a nearby well in winter. Temperature data were taken every ten days from late April until mid-October. To obtain accurate experimental temperature data, water layers temperature was measured in vertical direction whilst cold water was extracted from bottom of the tank on a daily basis at a rate corresponding to the regional inhabitants water consumption. It was observed that stable thermal stratification was developed after charging the reservoir. The temperature of extracted water was in the range of 11.9–13.1 °C during the entire summer period whilst the outside ambient temperature was reached upto 42 °C. It is believed that the radiation heat exchange between the water surface and the storage ceiling, as well as the convective heat and mass transfer from the surface of water induced by airflow were primarily responsible for temperature profile change. However, the discharged water flow rate had a secondary effect on thermal stratification.
Effects of Mean Flow Profiles on the Instability of a Low-Density Gas Jet Injected Into a High-Density Gas
Authors: Vedantam Nanda Kishore , Parthasarathy Ramkumar N.
Published: March 2009

The effects of the mean velocity profiles on the instability characteristics in the near-injector region of axisymmetric low-density gas jets injected vertically upwards into a high-density gas medium were investigated using linear inviscid stability analysis. The flow was assumed to be isothermal and locally parallel. Three velocity profiles, signifying different changes in the mean velocity in the shear layer, were used in the analysis. The effects of the inhomogeneous shear layer and the Froude number (signifying the effects of gravity) on the instability for each set of mean profiles were delineated. At a large Froude number (negligible gravity), a critical density ratio was found for the three profiles at which the jet became absolutely unstable. The critical density ratio for each velocity profile was increased as the Froude number was reduced. A critical Froude number was found for the three sets of profiles, below which the jet was absolutely unstable for all the density ratios less than unity, which demarcated the jet flow into the momentum-driven regime and the buoyancy-driven regime.
Numerical Simulation of Heat Transfer Mechanisms During Femtosecond Laser Heating of Nano-Films Using 3-D Dual Phase Lag Model
Authors: Kunadian Illayathambi , McDonough J. M. , Tagavi K. A.
Published: March 2009

In the present work we investigate femtosecond laser heating of nanoscale metal films irradiated by a pulsating laser in three dimensions using the Dual Phase Lag (DPL) model and consider laser heating at different locations on the metal film. A numerical solution based on an explicit finite-difference method has been employed to solve the DPL heat conduction equation. The stability criterion for selecting a time step size is obtained using von Neumann eigenmode analysis, and grid function convergence tests have been performed. The energy absorption rate, which is used to model femtosecond laser heating, has been modified to accommodate for the three-dimensional laser heating. We compare our results with classical diffusion and hyperbolic heat conduction models and demonstrate significant differences among these three approaches. The present research enables us to study ultrafast laser heating mechanisms of nano-films in 3D.
Correlation Between Unsteady Loading and Tip Gap Flow Occurring in a Linear Cascade Produced by Simulated Stator-Rotor Interaction
Authors: Staubs Joshua , Mish Patrick , Devenport William J.
Published: March 2009

The response of a compressor rotor blade tip to disturbances simulating unsteady stator rotor interaction in the casing region of a turbomachine such as an axial propulsion pump or axial compressor has been studied. The measurements were performed using 24 microphones embedded in the surfaces of two blades of a linear cascade with tip gap and single sensor-hot wire anemomemetry within the tip gap at a single tip gap (tg/c = 0.033). The unsteady velocity measurements were made perpendicular to the blade camber line at the same locations at which the microphones were embedded. Relative motion of the blade tips and casing was simulated with a moving endwall. Unsteady periodic inflow from an upstream stator row was modeled using a set of vortex generators attached to, and moving with the endwall. The unsteady pressure was measured at eight tip gaps (tg/c = 0.00825, 0.0165, 0.022, 0.033, 0.045, 0.057, 0.079, 0.129) along the chord and the span of the blades for a blade chord Reynolds number of 390,000. Upon initial investigations, the pressure fluctuations appear to be almost a linear variation with tip gap up to tg/c = 0.057. With increasing tip gap past this, the pressure fluctuations begin to decrease. Both the pressure and velocity fluctuations increase significantly near the trailing edge of the cascade blade suggesting that the response involves both viscous and inviscid mechanisms.
Wind Flow Simulation Around NASA KSC Vehicle Assembly Building
Authors: Vu B. T. , Verdier M. J.
Published: March 2009

A model of the wind flow conditions around Kennedy Space Center (KSC) Vehicle Assembly Building (VAB) is presented. An incompressible Navier-Stokes flow solver was used to compute the flow field around fixed Launch Complex 39 (LC-39) buildings and structures. The 3-D flow field, including velocity magnitude and velocity vectors, was established to simulate the localized wind speeds and directions at specified locations in and around LC-39 buildings and structures. The results of this study not only help explain the physical phenomena of the flow patterns around LC-39 buildings but also are useful to the Shuttle personnel. Current Operations and Maintenance Requirements and Specifications (OMRS) for vehicle transfer operations are based on empirically derived historical data, and no detailed mathematical analysis of wind conditions around LC-39 structures has ever been accomplished.
Filtered Rayleigh Scattering Thermometry in a Premixed Sooting Flame
Authors: Kearney Sean P. , Grasser Thomas W. , Beresh Steven J.
Published: March 2009

Filtered Rayleigh Scattering (FRS) is demonstrated in a premixed, sooting ethylene-air flame. In sooting flames, traditional laser-based temperature-imaging techniques such linear (unfiltered) Rayleigh scatting (LRS) and planar laser-induced fluorescence (PLIF) are rendered intractable due to intense elastic scattering interferences from in-flame soot. FRS partially overcomes this limitation by utilizing a molecular iodine filter in conjunction with an injection-seeded Nd:YAG laser, where the seeded laser output is tuned to line center of a strong iodine absorption transition. A significant portion of the Doppler-broadened molecular Rayleigh signal is then passed while intense soot scattering at the laser line is strongly absorbed. In this paper, we demonstrate the feasibility of FRS for sooting flame thermometry using a premixed, ethylene-air flat flame. We present filtered and unfiltered laser light-scattering images, FRS temperature data, and laser-induced incandescence (LII) measurements of soot volume fraction for fuel-air equivalence ratios of φ = 2.19 and 2.24. FRS-measured product temperatures for these flames are nominally 1500 K. The FRS temperature and image data are discussed in the context of the soot LII results and a preliminary estimate of the upper sooting limit for our FRS system of order 0.1 ppm volume fraction is obtained.
Public Debates: Key Issue in the Environmental Licensing Process for the Completion of Cernavoda 2 NPP
Authors: Rotaru Ioan , Jelev Adrian
Published: March 2009

Societatea Nationala “NUCLEARELECTRICA” S.A., the owner of Cernavoda NPP, organized, in 2001, several public consultations related to environmental impact of the completion of the Cernavoda 2 NPP, as required by the Romanian environmental law, part of project approva. Public consultations on the environmental assessment for the completion of the Cernavoda NPP - Unit 2 took place between 15.08.2001–21.09.2001 in accordance with the provisions of Law No. 137/95 and Order No. 125/96. Romanian environmental legislation, harmonization of national environmental legislation with European Union, Romanian legislative requirements, information distributed to the public, issues raised and follow-up, they all are topics highlighted by this paper and they are addressing the environmental licensing process of the Cernavoda 2 NPP.
Radiochemical Separations for the Pretreatment of High-Level Nuclear Waste Solutions at the Savannah River Site
Authors: Hobbs D. T. , Peters T. B. , Duff M. C. , Barnes M. J. , Fink S. D. , Walker D. D.
Published: March 2009

A significant fraction of the high-level nuclear waste produced from fuel reprocessing operations at the Savannah River Site (SRS) must be pretreated to remove 137Cs, 90Sr and alpha-emitting radionuclides (i.e., actinides) prior to disposal onsite as low level waste. Separation processes planned at the SRS include caustic side solvent extraction for 137Cs and sorption onto monosodium titanate (MST) for 90Sr and alpha-emitters. The predominant alpha-emitting radionuclides in the highly alkaline waste solutions include plutonium isotopes 238Pu, 239Pu and 240Pu. This paper describes the planned Sr/actinide separation process and summarizes recent tests and demonstrations with simulated and actual tank waste solutions.
Project WAGR: The UK Demonstration Project for Power Reactor Decommissioning - The Core and Beyond
Authors: Benest Terry
Published: March 2009

The United Kingdom Atomic Energy Authority (UKAEA) has built and operated a wide range of nuclear facilities since the late 1940s. UKAEA’s present mission is to restore the environment of these facilities in a safe and secure manner. This restoration includes the decommissioning of a number of redundant research and power reactors. The Windscale Advanced Gas-cooled Reactor (WAGR) operated at an output of 33 MW (e) from 1963–1981 and comprised a carbon dioxide cooled, graphite moderated reactor using uranium dioxide fuel in stainless steel cans. WAGR was the prototype reactor used to develop technologies for the family of full-scale commercial AGRs that followed. Following shutdown, UKAEA decided to continue their research activities into the decommissioning phase to develop dismantling techniques and establish waste routes. The initial phases of the project involved the construction of the waste handling route and the design and construction of a remote dismantling machine and an interim ILW store. The reactor core and pressure vessel is now being dismantled in a programme of 10 campaigns. This paper will summarise the history of the reactor, the operation of the waste-processing route, the installed dismantling equipment and the successful completion of the first seven campaigns. The rapid completion of Campaign 6, “the reactor core and restraint structures”, will be described in detail. The paper will also describe work to develop remotely operated oxy-propane cutting equipment to dismantle the core support structures and the pressure vessel and due to be used in 2003/2004. Special attention will be given in this paper to the recent rapid progress in the remote dismantling campaigns and the low radiation doses incurred by operators.
The First Decommissioning of a Fusion Reactor Fueled by Deuterium-Tritium
Authors: Gentile Charles A. , Perry Erik , Rule Keith , Williams Michael , Parsells Robert , Viola Michael , Chrzanowski James
Published: March 2009

The Tokamak Fusion Test Reactor (TFTR), at the Plasma Physics Laboratory of Princeton University (PPPL) was the first fusion reactor fueled by a mixture of deuterium and tritium (D-T) to be decommissioned in the world. The decommissioning was performed over a period of three years and was completed safely, on schedule and under budget [1]. Provided is an overview of the project and detail of various factors which led to the success of the project. Discussion will cover management of the project, engineering planning before the project started and during the field work was being performed, training of workers in the field, the novel adaptation of tools from other industry, and the development of an innovative process for the use of diamond wire to segment the activated / contaminated vacuum vessel. The success of the TFTR decommissioning provides a viable model for the decommissioning of D-T burning fusion devices in the future.
Evaluation of Uncertainty Associated With Spatially Variable Properties
Authors: Kato Kazuyuki , Maeda Tadashi , Takase Hiroyasu
Published: March 2009

Uncertainties associated with spatially variable properties of geologic characteristics are especially important. However, these uncertainties cannot be specified in a deterministic manner because the process of formation or evolution of host rock is random and because the limited number of data is available for the statistic evaluation of this random process. We develop the hybrid model of fuzzy geostatistics for the appropriate treatment of uncertainties associated with spatially variable properties. For the application of the above method, we prepared the virtual field with heterogeneous hydraulic conductivity for the simulation of site characterization. In this simulation, we consider the situation that the limited number of boring data is available. The conventional method can determine only one variogram. In this case, uncertainties due to the ignorance are not appropriately handled and the degree of belief for the determined variogram is not specified. For the appropriate treatment of ignorance, we define the possible range of variogram in terms of fuzzy membership functions on the level of conservatism. A large number of heterogeneous hydraulic conductivity fields are realized by using corresponding variograms that sampled from the possible range of variogram. For each realized field, we compute the groundwater flow model and estimate the average flow velocity. Resulting many average flow velocities are processed by fuzzy rule to obtain the membership function of estimated average flow velocity. This can be used as the input data for the hybrid probabilistic and possibilistic safety assessment. Comparing with the previous work, the process of defining the membership function of average flow velocity becomes transparent and the reliability of safety assessment is enhanced.