bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Simulation of Spacing Effects on the Flow Past Two 2:1 Rectangular Cylinders in Tandem at Re = 200
Authors: Huang Zhu , Xi Guang , Zhang Wei 
Published: July 2013

The time-periodic flow over two rectangular cylinders in infinite medium is numerically investigated in this paper using the newly developed multidomain pseudospectral method. The two cylinders are arranged in tandem and both with length-to-width aspect ratio of 2; the incoming flow is assumed to be laminar and uniform, and the Reynolds number based on the cylinder width and the freestream velocity is fixed at 200.Computations are focusing on the effects of S, the ratio between the streamwise spacing of two cylinders (gap length) and the cylinder width, on the vortex shedding formations, evolving patterns and related aerodynamic performances of cylinders within the range 1 ≤ S ≤ 10.
Numerical results reveal that as S increases, there exists a critical value, Scr = 5, at which the mean drag coefficients of both cylinders behave notable jumps, and the root-mean-square values of lift and drag coefficients reach maxima. Meanwhile, the vortices behind the two cylinders are shedding in anti-phase mode at Scr, and their evolving patterns are further analyzed and interpreted.
Error Estimation Using Hybrid Methods
Authors: Celik Ismail , Karaismail Ertan , Elizalde Blancas Francisco , Parsons Don , Sezer Hayri 
Published: July 2013

New formalisms are developed for robust calculation of the discretization errors in CFD applications. The new methods are based on the premise that the true error (i.e. the difference between the exact solution and the numerical solution) on a given mesh is similar to the approximate error (i.e. the difference between the fine grid solution and the coarse grid solution). The proportionality constant can be calculated theoretically for a given scheme and it is, to a first order approximation, only a function of the grid refinement ratio. This method is called Approximate Error Scaling (AES) method.
Although AES is a viable method for error estimation it does not directly take into account the transport of error nor the error sources at the boundaries. To remedy this, a new method which is referred to, here and after, as the residual source in transport (REST-IC) method is formulated. This paper presents the theoretical details and the results from several test cases that are used for validation of the newly proposed methods.
Application to the 1D and 2D steady scalar transport equation and 2D Navier-Stokes (N-S) equations has revealed excellent performance with a pressure based segregated N-S finite volume solver. Implementation of these methods into CFD commercial codes such as ANSYS-FLUENT can be done with the help of expert developers of the code who can handle residuals for the selected equation and the variable through user defined subroutines.
CFD-Integrated in Preliminary Design of Unmanned Helicopter
Authors: Ridluan Artit , Charoenpon Attapon , Julniphitwong Achirakris , Thaworn Kasama 
Published: July 2013

In helicopter performance design and optimization, aerodynamics is the primary area. Therefore to achieve the required helicopter performance to accomplish the missions, the efficient design process in preliminary design phase is crucial. In a past, the preliminary design involved the simplified equations to account for the aerodynamic behavior of a rotorcraft, resulting in the loss of aerodynamic phenomena such as turbulence and vortex flow pattern, which contribute to the nonlinear behaviors.
In order to improve overall design process, we thus propose the preliminary design process without the iteration. The proposed preliminary design applied the recent blade design theories with CFD procedure integrated in the preliminary design. The main benefit of this new methodology is to access the detailed flow physics as quick as possible, thus allowing the designer to faster analyze and improve the performance of the helicopter in early stage of design process.
Based on the design results given by the proposed preliminary design methodology, the new blade design was configurationally changed. The redesigned blade was twisted configuration with ∼9 and ∼27 degrees at the cone at the tip and cone, respectively. The computational results showed that the twisted blade increased the lift by approximately 846% relative to the fist design. In addition, the design cycle can be completed in only one cycle and the design time spent is few days.
Investigation of Relative Importance of Some Error Sources in Particle Image Velocimetry
Authors: Harris Jeff , Smith Barton L. , Wilson Brandon 
Published: July 2013

Several error sources are analyzed for 2-component PIV, including: calibration, magnification variation, perspective, resolution, and the correlation algorithm noise floor. Several of these error sources are compared with previously published estimates. New experimental data and methods for measuring the contribution of each source to velocity uncertainty are presented.
The calibration uncertainty on the velocity measurement was found to be small (so long as reasonable care is taken in the calibration) and independent of the calibration target for a 2-component PIV setup. The perspective error and magnification variation were both calculated and experimentally found to be small. The light sheet thickness only has an effect when the thickness is greater than 1% of the distance from the light sheet to the camera lens plane. The spatial resolution may be so coarse as to not capture the smaller eddies in the flow, thus attenuating the measured fluctuations. The noise floor was found to contribute significantly to the uncertainty in the velocity measurements in sub-pixel displacement.
Experimental Analysis of Flow Crossover in a Solar Thermochemical Reactor
Authors: Mayer Luke J. , James Darryl L. 
Published: July 2013

As energy and fuel security continue to be of increasing importance to economies around the world, countries are looking to move away from oil dependency. Energy solutions are being sought in the area of solar fuels to meet these growing needs. Concentrated solar thermochemical technology has the potential to directly convert sunlight into a useable, carbon-neutral liquid fuel that can be easily stored and integrated into our existing forms of energy demand such as transportation and heating fuels. Ongoing research performed by several groups at Sandia National Laboratories seeks to fundamentally understand the complex physics and chemistry occurring within a solar thermochemical reactor prototype named the CR5 [counter-rotating-ring receiver/reactor/recuperator]. The CR5 utilizes a stack of counter-rotating disks with metal oxide reactive material fins which are cycled through oxidation and reduction zones. The metal oxide is thus used to reduce H2O and CO2 into H2 and CO respectively, which can be combined using known processes to form a liquid fuel.
The effectiveness of such a solar thermochemical reactor depends on its ability to efficiently integrate reduction and oxidation reactions, a solar receiver, thermal recuperation, and separation of end product gases. Efficient separation of end product gases within the reactor is of critical importance as without it, the crossover of gases occurs, which results in lower reduction rates, recombination of end product gases, and additional energy spent in downstream processes. A validation reactor model called the CR5v (v for validation) has been fabricated to validate numerical models of the reactor processes. Crossover testing is done without any chemical reactions (therefore with no O2 or H2 present), but rather by examining the flow of CO2 and Argon.
This work presents experimental crossover for the CR5v reactor as a function of ring rotation speed, internal purge gas, and sweep gas to injection gas ratio. Initial crossover experimental results from the CR5v reactor suggest that crossover levels are largely not affected by ring rotation, center purge or injection gas/sweep gas ratio. Argon flow remained on average at a crossover value of 52 %, while CO2 crossover levels were on average around 8 %. The crossover flow in the system is thought to be dominated by the flow rates of the two pumps used in the system and to a lesser degree, the geometry of the system.
Investigation of Flow Boiling Heat Transfer in Microgravity via Infrared Thermometry
Authors: Kommer Eric , Dessiatoun Serguei , Kim Jungho , Kim Tae Hoon , Solotych Valentin 
Published: July 2013

Flow boiling heat transfer is an important mechanism across a wide variety of engineering disciplines. The prediction of the heat transfer rate as a function of flow conditions and temperature has been based almost exclusively on experimentally derived correlations. The quality of these correlations depends on the accuracy and resolution of the measurement technique. In addition to the complexities of flow boiling phenomenon in earth gravity, engineering design of space systems requires knowledge of the gravity dependence for heat transfer prediction.
Current research has shown significant variations in the heat transfer during pool boiling as a function of gravity magnitude. Research into flow boiling in variable gravity environments is very limited at this time, and such data is needed if multiphase systems are to be designed for space applications.
The objective of this study is to develop, validate, and use a unique infrared thermometry method to quantify the heat transfer characteristics of flow boiling over a range of gravity levels. This new method allows high spatial and temporal resolution measurements, while simultaneously allowing the flow to be visualized. Validation of this technique is demonstrated by comparison with accepted data in earth gravity environments. Measurements taken in high, earth, and zero gravity environments are used to show how the heat transfer characteristics change with gravity.
A Methodology for Modelling Enclosure Radiation Heat Transfer Under Large Structural Deformation
Authors: Subia Samuel R. , Dempsey J. Frank , Crane Nathan K. , Thomas Jesse D. 
Published: July 2013

Finite element method (FEM) numerical simulations of heat transfer for high-temperature regimes often require modeling of grey-body enclosure radiation where enclosure geometry definitions are obtained as part of the model grid generation process. Owing to the expense of solving the radiation problem, typical FEM approaches loosely couple the radiative transfer solution as boundary conditions to a standard conduction formulation. When the problem at hand is thermal-mechanical and relative motion occurs between enclosure surfaces, the simulation code is tasked with providing a means of updating the original enclosure surface geometry to reflect the deformed configuration. While this scenario is manageable for contiguously meshed discretizations, the difficulty of updating enclosure geometry is greatly increased when the model admits sliding. Here the analysis code must employ both mechanical and thermal contact, relying heavily on geometric search and contact constraints to enforce closure for the conduction formulation.
General purpose large-deformation FEM structural codes employ surface contact utilities to provide geometric search and contact constraint definitions. This paper describes an ongoing effort to leverage contact utilities for solving the enclosure radiation problem in deforming and sliding mesh scenarios while having minimal impact to a traditional modeling approach. The current effort is divided into two areas, enclosure definitions and thermal contact, but the primary focus here is on enabling use of contact to provide definition of the enclosure. The proposed methodology is demonstrated on simple enclosure radiation models using SNL Sierra Mechanics Dash contact utilities and the Chaparral enclosure radiation library with Sierra Mechanics Structural and Thermal application codes.
Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energys National Nuclear Security Administration under contract DE-AC04-94AL85000.
Diesel Particulate Filter Retrofit of a 1500 kW Multi-Engine Genset Locomotive
Authors: Hedrick John , Fritz Steve , Plunkett Kathy 
Published: July 2013

This paper documents the initial test results of a locomotive diesel particulate filter (DPF) retrofit project. The locomotive used for this project was BNSF1284, a 1,566 kW National Railway Equipment Company (NREC) model 3GS21B, originally manufactured in April, 2008, and designed to be an Ultra-Low Emissions Locomotive (ULEL). This genset switcher locomotive uses three Cummins QSK19 Cummins 522 kW diesel-engine driven generator sets (Genset 1, 2, and 3) to provide the power needed to drive the traction motors.
The GT Exhaust Diesel Particulate Filter (DPF) retrofit system, installed on BNSF1284, uses catalyzed DPF elements. The DPF, and its catalyzed coating, offered significant hydrocarbons (HC), carbon monoxide (CO), and particulate (PM) emissions reduction. Additionally, the catalyzed coating should allow the diesel particulate filters to passively regenerate at moderate exhaust temperatures, thus keeping the engine back pressure within allowable limits of the manufacture.
The GT Exhaust DPF’s were installed in place of the standard mufflers on each of the three engines. The GT Exhaust DPF’s are roughly the same size as the stock muffler. The only locomotive modification needed to install the GT Exhaust DPF’s was to the muffler mounting platform, directly above the engine, where the exhaust pipe opening needed to be enlarged. There are no external modifications to the locomotive car body needed to install the GT Exhaust DPF’s.
After installation of the DPF’s, they were degreened by operating the engines at rated power for 20 hours. After degreening testing was performed according to Title 40 of the U. S. Code of Federal Regulations (CFR), Part 92, Subpart B. The addition of the DPF reduced the PM emissions to 0.016 g/kW-hr or 60 percent below the locomotive Tier 4 PM limits.
BNSF1284 was returned to revenue service in Richmond, California in March 2012, where the DPF performance will be tracked for 3,000 hours of operation as part of a California Air Resources Board (CARB) verification program.
SI Engine Piston Pin Motion Measurement as Related to Noise
Authors: Chen Yu , Deck Carol Lynn , Hall Christopher 
Published: July 2013

NVH is a necessary consideration in engine component development. The piston pin joint can be a significant contributor of mechanical noise in SI engines. Although there is literature on this subject, most of it is dealing with measurement using accelerometers for vibration analysis. This however does not indicate the fundamentals of the piston pin to connecting rod pin bore interaction mechanism. Limited research was found on this matter which prompted this investigation.
A measurement system was designed to determine the connecting rod small end bore clearance in real-time from the base and side of the pin bore. In this system, we applied a high precision displacement sensor to measure the pin motion, and a linkage was designed and fabricated to transfer the signal output out of the engine. This information was then correlated with accelerometer impact measurements to create a baseline for piston pin motion. Impacts were linked to the load reversal of the piston pin to connecting rod interface.
Advanced Tribological Assessment of Ring Coatings
Authors: Maschewske Max , Karrip Kimm , Deck Carol Lynn 
Published: July 2013

Friction reduction within the power cylinder assembly of internal combustion engines continues to be a one of the foremost focuses of engine manufactures. In an effort to better address this topic previously developed bench test rigs, such as the Falex, Cameron-Plint, and EMA-LS9 [1,2], have been utilized. These devices were formerly focused solely on wear mechanisms and material compatibility. Current development of new piston ring coatings has demanded significant refinements to the previously mentioned EMA-LS9 test rig for specific frictional characteristic evaluations. These developments have allowed for coefficient of friction ranking between various piston ring materials in addition to the influence and surface finish on coefficient of friction.
This paper examines how the test rig is utilized to characterize upper compression ring materials, surface treatments, and the impact of surface finish. The significance of these results will be examined as it applies to analytical evaluations. From these calculations a demonstration of the effect of surface finish on ring dynamics and gas flow, as well as future piston ring coating developments will be discussed.
Fabrication of Micro Organs Using a Digital Micro-Mirroring Microfabrication System
Authors: Hamid Qudus , Wang Chengyang , Sun Wei 
Published: July 2013

Micro-Electro-Mechanical Systems (MEMS) technologies have been very attractive and demonstrate the potential for many applications in the field of tissue engineering, regenerative medicine, and life sciences. These fields bring together the multidisciplinary field of engineering and integrated sciences to fabricate three-dimensional models that aides the exploration, generation or regeneration of organic tissues and organs. Presently, monolayer cell cultures are frequently used to investigate potential anti-cancer agents. The issues at hand are that these models give very little in terms of feedback on the effects of the microenvironment on chemotherapeutic and the heterogeneity of the tumor. Three-dimensional tumor and cancer models that mimic the actual disease are developed for in vitro investigations. These models create an environment that enables diseases to have an enhanced evaluation (compared to two dimensional) and eliminate the limitations of the traditional mainstays of cancer research. Three-dimensional Cancer models are economic, allow for biological characterizations. Cancer models are developed from investigations of the actual disease; computer tomography (CT) and magnetic resonance imaging (MRI) allow for biomodeling of the disease’s environmental conditions.
Unlike many traditional microfabrication techniques, the Digitial Micro-mirror Microfabrication (DMM) System eliminates the need for mask by incorporating a dynamic mask-less fabrication technique. The DMM is specifically designed for the developments of biologically inspired devices, whether it’s a multicellular spheroid, hollow fiber, or multicellular layer (MCL) models; the DMM has the potential to utilize its dynamic micro mirrors to build the tissue model according to its desired design and characteristics. Each model is specifically designed to mimic the in vivo conditions of the tissue of interest.
Cellular Honeycomb-Like Structures With Internal Buckling and Viscous Elements for Simultaneous Load-Bearing and Dissipative Capability
Authors: Barbarino Silvestro , Pontecorvo Michael E. , Gandhi Farhan S. 
Published: July 2013

Cellular structures with hexagonal unit cells show a high degree of flexibility in design. Based on the geometry of the unit cells, highly orthotropic structures, structures with negative Poisson’s ratios, structures with high strain capability in a particular direction, or other desirable characteristics may be designed. Much of the prior work on cellular structures is based on hexagonal honeycomb-like unit cells, without any inclusions. A companion paper to the current paper presented a vision of cellular honeycomb-like structures with diverse inclusions or internal features within the unit cells (such as contact elements resulting in stiffening behavior, buckling beams resulting in softening behavior, bi-stable elements producing negative stiffness or viscous dashpots producing dissipative behavior). That paper further went into details on linear springs as the most fundamental of inclusions.
In the present paper, a buckling beam and viscous dashpots are used as inclusions in the basic pin-jointed rigid-walled hexagonal unit cell. The buckling beam provides the cell with a high initial stiffness and load carrying capability. At loads beyond the critical buckling load, the unit cell softens (while still retaining the ability to carry a “design” load), and undergoes large deformation under incremental load. The viscous dampers undergo a correspondingly large stroke resulting in high dissipative capability and loss factor under harmonic or transient disturbance beyond the design load. In the paper, an analysis and design study of the cell behavior with variation in unit cell geometric parameters, buckling beam parameters and viscous dashpot parameters is presented. The analytical results in the paper are validated against ANSYS Finite Element results. Further, a prototype unit cell with an aluminum internal buckling beam and viscous dashpots is fabricated and tested under static and dynamic loads in an Instron machine. Good correlation is observed between the tests, the FE results and the analytical simulations when accounting for the non-linear behavior of the viscous dashpot used in the tests.
Nonlinear Guided Waves for Structural Health Monitoring: Numerical Algorithm and Application to Railroad Track
Authors: Nucera Claudio , Lanza di Scalea Francesco 
Published: July 2013

The University of California at San Diego (UCSD), under a Federal Railroad Administration (FRA) Office of Research and Development (R&D) grant, is conducting research to develop a system for in-situ measurement of the rail Neutral Temperature in Continuous-Welded Rail (CWR). It is known that CWR can break in cold weather and can buckle in hot weather. Currently, there is a need for the railroads to know the current state of thermal stress in the rail, or the rail Neutral Temperature (rail temperature with zero thermal stress), to properly schedule slow-order mandates and prevent derailments.
UCSD has developed a prototype for wayside rail Neutral Temperature measurement that is based on non-linear ultrasonic guided waves. Numerical models were first developed to identify proper guided wave modes and frequencies for maximum sensitivity to the thermal stresses in the rail web, with little influence of the rail head and rail foot. Experiments conducted at the Large-scale Rail NT Test-bed indicated a rail Neutral Temperature measurement accuracy of a few degrees. Field tests are planned at the Transportation Technology Center (TTC) in Pueblo, CO in June 2012 in collaboration with the Burlington Northern Santa Fe (BNSF) Railway.