bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rayleigh-Taylor Instability of a Shock Accelerated Gas Water Interface
Authors: Wang Xiao-Liang , Itoh Motoyuki 
Published: November 2021

Abstract
Rayleigh-Taylor instability at a gas-water interface has been investigated experimentally. Such instability was produced by accelerating a water column down a vertical circular tube employing shock wave impact. Accelerations from 50 to 100 times gravitational acceleration with fluid depths from 125 to 250 mm were studied. The resulting instability from small amplitude random perturbations was recorded and later analyzed using high-speed video images. Cavity formation was observed in the middle of the gas-water interface soon after the shock wave impact; bubbles and spikes then developed across the rest of the interfacial plane. Measurements of the growth coefficient of the bubbles and spikes show that they are nearly constant over different runs.
GenIDLEST: A Scalable Parallel Computational Tool for Simulating Complex Turbulent Flows
Authors: Tafti D. K. 
Published: November 2021

Abstract
The paper describes the framework, features, capabilities, and example applications of GenIDLEST, a computational tool for the time-dependent simulation of turbulent flows in complex geometries. Preliminary work in coupling GenIDLEST with GRID enabled software for distributed computing, data archiving, and visualization is also described.
Analysis of Centrifugal Pump Performing Under Two-Phase Flow Using Bleeding System
Authors: Zaher M. A. 
Published: November 2021

Abstract
A one dimensional two fluid model is used to study the performance of a centrifugal pump. Pumping of two-phase products in oil/geothermal industry offered a special multiphase pump. Test with different suction void fraction was used to predict the two-phase pump head data for two scales of pumps. With the new arrangement of bleeding and correct impeller design, a radical solution is offered to handle a multiphase flow. The physical mechanism responsible for transporting multiphase flow on efficiency, specific energy requirement and flow rate were also investigated.
Validation of the Combustion Space Simulation of a Glass Furnace Model
Authors: Golchert B. , Chang S. L. , Petrick M. , Zhou C. Q. 
Published: November 2021

Abstract
A completely coupled glass furnace simulation that combines calculations for the combustion space, glass melt, and radiative heat transfer throughout the furnace has been developed as part of a Department of Energy sponsored program. A major component of this program entailed the collection of an extensive set of data from an operating glass furnace for the purpose of validation. The data collected were compared with the results from computer simulations of the furnace based on the actual operating conditions. These comparisons indicated that the computated results were valid. This paper will present and discuss the gas velocity and gas temperature measurements/validation studies.
Modeling Large-Size Boilers As a Set of Heat Exchangers: Tips and Tricks
Authors: Cortés Cristóbal , Díez Luis I. , Campo Antonio 
Published: November 2021

Abstract
Practical calculation of the heat-recovery sections of large-size boilers is still based on approximate methods. On the one hand, CFD-based models cannot directly handle the geometric intricacy of tube bundles, and thus rely on volume-averaged source terms that demand empirical input. On the other hand, the standard, lumped heat exchanger calculation, which can be a far simpler and more robust alternative, fails in several important aspects, mainly related to the effects of thermal radiation and the coupling between several sections.
In this paper, we consider the diverse sections of a coal-fired utility boiler as a case study to show how to deal with these shortcomings. Under the objective of developing a simple monitoring method, we extend the traditional heat exchanger model to take into account most of the peculiarities of boiler superheaters, reheaters and economizers. Techniques range from the re-examination of analytical solutions to the auxiliary use of CFD calculations. The models are assembled to simulate the thermal performance of the boiler as a whole unit. Results are validated against actual measurements taken at a thermoelectric plant.
Influence of a Periodic Radiation Heat Source on Polymer Ignition
Authors: Zheng Guanyu , Bénard André , Wichman Indrek S. 
Published: November 2021

Abstract
The ignition process of a thermoplastic polymer is investigated numerically regarding to the influence of a periodic radiation source for a given range of frequency. The ignition process is initiated when a solid polymer receives a high radiation heat flux in convective flow environment. The solid polymer undergoes preheating, melting, and pyrolysis with the development of ignition. The combustible gases, as a result of condensed phase pyrolysis process, react with oxygen in the gas phase via combustion reaction. A two-dimensional multi-phase combustion model is utilized to predict the influence of periodic radiation on ignition. The ignition delay and combustion characteristics are examined with respect to the transient patterns of the external radiation sources.
Fire Behavior in a Poorly Ventilated Compartment
Authors: Wakatsuki K. , Ringwelski B. , Quintiere J. G. 
Published: November 2021

Abstract
The fire behavior of heptane burning in a poorly ventilated compartment was studied. The diameter of the heptane pan fires were varied and the ventilation opening size and location were adjusted. Two kinds of compartment fire experiment were conducted: (1) horizontal slits at the top and bottom of a wall, and (2) a single vent at the roof. Temperature, oxygen, fuel mass loss rate and differential pressure were measured. Extinction was studied with an oxygen meter to find the minimum oxygen concentration in the compartment achieved in ventilation-controlled fires. Extinguishments due to ventilation or complete fuel consumption was distinguished. Flow exchange was measured by differential pressure transducers. Particularly, flow exchange of ceiling vent was examined by calculation of flooding pressure difference, which will allow bi-directional flow. The wall vent case had oscillatory combustion (puffing), which sometimes leads to an increase in fire amplitude followed by extinction. This was not observed for the ceiling vent case. Video recording of the flame was conducted through a glass on sidewall. The fire behavior varied from conditions in which the flame extinguishes to cases of steady burning. In some cases, “ghosting flames” were observed.
Self-Preserving Properties of Unsteady Round Nonbuoyant Turbulent Starting Jets and Puffs in Still Fluids
Authors: Sangras R. , Kwon O. C. , Faeth G. M. 
Published: November 2021

Abstract
The self-preserving properties of round nonbuoyant turbulent starting jets, puffs and interrupted jets were studied experimentally and theoretically for flows in still and unstratified environments. The experiments involved dye-containing fresh water sources injected into still fresh water within a large fresh water tank with images of the flows obtained using a video camera. Near-source behavior varied significantly with source properties but self-preserving behavior was observed at distances greater than 20–30 source diameters from the source. Within the self-preserving region, normalized streamwise and radial penetration distances varied as functions of time, in accord with requirements for self-preservation, to the following powers: 1/2 for starting nonbuoyant jets and 1/4 for nonbuoyant puffs. Effects of injected fluid quantity for puffs were reflected by the location of the virtual origin which was independent of injected fluid volume for small volumes but became proportional to injected fluid volume for large volumes typical of interrupted jets.
Transport in Turbulent Jet Diffusion Flames With Annular Counterflow
Authors: Torii Shuichi , Chan Sze Man Simon , Yano Toshiaki 
Published: November 2021

Abstract
The present study deals with the augmentation of the turbulent shear effect on transport in turbulent jet diffusion flames due to the presence of air-suction flow and the possibility of extending the flame blow-off limits through augmentation. The experimental apparatus employed here comprises a fuel nozzle placed at the center of a concentric annulus with an outer cylinder encompassing the nozzle. The fuel jet is allowed to eject upwards and turbulent jet diffusion flames are formed by igniting the jet, then by increasing the volume flow rate of the fuel. The annular counterflow technique was employed to augment the turbulent shear effect. It is found that (1) the augmentation of turbulent shear effect exerted on the shear layer formed between the jet flames and the opposed flow of air causes an increase in temperature of the cold fuel gas at the flame center and an extension of flame blowoff limits; (2) flame lift-off heights are suppressed; (3) the lift-off propensity of the diffusion flame is alleviated by such augmentation.
A Procedure for View Factor Calculation Using the Finite-Volume Method
Authors: Chai John C. , Moder Jeffrey P. , Karki Kailash C. 
Published: November 2021

Abstract
This article presents a finite-volume method to calculate view factors between surfaces of control volumes. A simple approach, which does not lead to the increase in memory requirement with increasing angular grid, is used. The spatial and angular resolution errors are resolved by grid refinements. The procedure can handle straight-edged, inclined, and curved boundaries. Three problems are examined and the exact solutions are reproduced.
Apparent Radiative Properties and Radiation Scattering by a Semitransparent Hemispherical Shell
Authors: Fan Tai-Hsi , Fedorov Andrei G. 
Published: November 2021

Abstract
Knowledge of the apparent radiative properties of the semitransparent hemispherical shell placed on an opaque surface is of the fundamental interest and also important to a number of application in materials processing and manufacturing ranging from metallurgical slag foaming to batch foams in glass melting to hollow bead fabrication. This paper extends our recent work [7] on using the analytical and numerical ray tracing techniques to study radiative transfer in the system described. Specifically, the local volumetric heating rate and the scattering phase function of a thin hemispherical shell exposed to incident collimated radiation are calculated both analytically and numerically, and the results are discussed in detail. To further elucidate the results, the comparison is made of the total apparent transmittance of the hemispherical shell to a plane parallel layer of semitransparent material.
Consideration of the Scattering Effects in the Glass As a Participating Medium Using the Discrete Ordinates Method
Authors: Rodicio S. Coutin , Torres B. Restrepo 
Published: November 2021

Abstract
Three-dimensional radiative heat exchange in a commercial type of glass as a participating medium is predicted using the discrete ordinates method. The radiative transfer equation (RTE) is analyzed for an absorbing, re-emitting, and scattering medium enclosed by gray walls. The main objective of this work is to formulate the RTE in a three-dimensional enclosure represented by a rectangular glass furnace where scattering effects are considered in the prediction of the radiant intensity, temperature distribution, incident and emitted energy, and heat flux at the glass surface. A comparative study is performed for glass under scattering and non-scattering conditions. The influence of scattering effects in the radiant intensity will provide further understanding of their impact in the glass thermal behavior. Additionally, the results of a parametric study on the glass for different scattering coefficients, surface heat flux, wall emissivity, and the forward scattering are discussed. The S4 approximation of the discrete ordinates method is employed in this model.
Modeling of Transport Processes Within a Molten Carbonate Fuel Cell Stack
Authors: Ma Z. , Jeter S. M. , Abdel-Khalik S. I. 
Published: November 2021

Abstract
Concern over global warming due to emission of green house gases has generated considerable interests and intensive development of fuel cells. In order to reduce the fuel cell manufacturing costs and to improve its performance and reliability, a better understanding of the fuel and oxidant species transport processes within fuel cell stack is important for fuel cell design. Fuel and oxidant stream flow distributions within a stack have significant impact on fuel cell performance and efficiency. To this end, this investigation presents the effects of the fuel and oxidant flow distributions on fuel cell stack performance with a model of fluid flow, heat and mass transfer including the electrochemical reaction, within a molten carbonate fuel cell under different gas supply conditions.
Analysis for the Effect of Inverter Ripple Current on Fuel Cell Operating Condition
Authors: Gemmen Randall S. 
Published: November 2021

Abstract
The effect of inverter ripple current on fuel cell stack performance and stack lifetime remains uncertain. This paper provides a first attempt to examine the impact of inverter load dynamics on the fuel cell. Since reactant utilization is known to impact the mechanical state of a fuel cell, it is suggested that the varying reactant conditions surrounding the cell govern, at least in part, the lifetime of the cells. This paper investigates these conditions through the use of a dynamic model for the bulk conditions within the stack, as well as a one-dimensional model for the detailed mass transport occurring within the electrode of a cell. These two independent modeling approaches help to verify their respective numerical procedures. In this work, the inverter load is imposed as a boundary condition to the models. Results show the transient behavior of the reactant concentrations within the stack, and of the mass diffusion within the electrode under inverter loads with frequencies between 30 Hz and 1250 Hz.
Application of a New CFD Analysis Tool for SOFC Technology
Authors: Prinkey Michael T. , Gemmen Randall S. , Rogers William A. 
Published: November 2021

Abstract
FLUENT™, a commercial computational fluid dynamics (CFD) package, has been modified to include fuel cell electrochemistry. The model is being developed to account for three loss mechanisms present in fuel cells: ohmic overpotential, concentration overpotential, and electrochemical overpotential, each capable of temperature dependency. Because we envision this model to be applied to a wide range of geometries, the present model is also being developed to directly assess the electric potential field. This paper presents some preliminary results from the present model, and provides a summary status of our development.
The main results from the present study arise from an analysis of a single monolithic SOFC geometry. Several cases were analyzed in order to generate a typical steady-state V-I curve for the cell, which summarizes its performance. Results on the detailed distribution of various conserved quantities are also presented. The preliminary results are encouraging, and show that for the geometry under study, simple scale-up relations may hold. Additionally, the newly developed tool no longer requires the modeler to manually input approximate current flow information, which will be seen to be of great benefit in fuel cell analysis.
Modeling of Recuperative Heat Exchanger in a Joule-Thomson Cooler
Authors: Ng Kim Choon , Wang Jinbao , Xue Hong 
Published: November 2021

Abstract
To develop effective heat exchangers for miniature and micro Joule-Thomson (J-T) cooling system, the performance of a recuperative heat exchanger is analyzed and evaluated. The evaluation is based on a theoretical model of the Hampson-type counter-flow heat exchanger. The effect of the pressure and temperature-dependent properties and longitudinal heat conduction are considered. The results of the numerical simulation are validated with the corresponding experimental measurements. The performance of the heat exchanger on effectiveness, flow and various heat conduction losses as well as liquefied yield fraction are analyzed and discussed. The simulation model provides a useful tool for miniature J-T cooler design.
Tuning of Membership Functions in a Fuzzy Rule Set for Controlling Convergence of Laminar CFD Solutions
Authors: Dragojlovic Zoran , Kaminski Deborah A. , Ryoo Juntaek 
Published: November 2021

Abstract
Under-relaxation in an iterative CFD solver is guided by fuzzy logic to achieve automatic convergence with minimum CPU time. The fuzzy rule set uses information from a Fourier transform of a set of characteristic values. The control algorithm adjusts the relaxation factors for the system variables on each iteration and restarts the solver if divergence occurs.
Four problems of laminar fluid flow and heat transfer are solved. They include buoyancy driven flow in a square cavity, lid driven flow in a square enclosure, mixed convection over a backward facing step and Dean flow. The consideration of buoyancy driven flow in a square cavity took into account a case with isothermal vertical walls, as well as a case with heat conduction in the solid wall on the right hand side of the cavity. The incompressible Newtonian conservation equations are solved by the SIMPLER algorithm with simple substitution. In order to achieve the best performance of the fuzzy controller, a set of triangular membership functions was tuned by using a gradient method.
The fuzzy control algorithm with the optimal membership functions significantly reduced the CPU time needed for solving the problem, compared to performance of triangular membership functions before optimization. The improvement in speed of convergence varied from 10% in the case of Dean flow to 70% in the case of buoyancy driven flow in a square enclosure with isothermal walls. For all the problems considered, the fuzzy rule set provided convergence comparable in speed to that obtained with the best choice of constant relaxation factors. In the case of buoyancy driven cavity flow with conjugate heat transfer, the fuzzy controller outperformed any choice of constant relaxation factors.
Aerodynamics of Scallop Seal Flows in Turbomachinery
Authors: Chochua Gocha , Shyy Wei , Moore Jeffrey 
Published: November 2021

Abstract
Gas annular seals are commonly adopted for leakage control in turbomachinery applications. Scallop seal is an representative example of damper seals, and is attractive from rotordynamic stability viewpoint. To understand flow physics in such seals a computational analysis is developed to study compressible, turbulent flow in it. The following issues are addressed: (i) validation of results obtained using periodic boundary conditions accounting for turbulent and compressible flows, (ii) effect of the rotor rotation and inlet swirl ratio on flow development in the seal, (iii) extrapolation of the full-length results from limited periodic simulations, and (iv) breakdown of the friction factor on contributing pressure and shear stress components. The computational techniques presented can help address the design related issues more economically, and the findings offer insight into the fluid physics associated with a scallop seal.
Effects of Inlet Swirl Angle on Flow and Heat Transfer in Contoured Turbine Nozzle Guide Vanes
Authors: Lin Y.-L. , Schock H. J. , Shih T. I-P. , Bunker R. S. 
Published: November 2021

Abstract
Computations, based on the ensemble-averaged compressible Navier-Stokes equations closed by the shear-stress transport (SST) model of turbulence, were performed to investigate the effects of inlet swirl angle on the three-dimensional flow and heat transfer in two contoured endwall configurations. Swirl angles investigated include three constant angles (0°, 15°, 30°) and a linearly varying angle from +30° at one endwall to −30° at the other. For all swirl angles, the mass-flow rate through the nozzle was fixed so that the higher the swirl angle, the higher is the velocity magnitude. Of the two endwalls investigated, one has all of the contouring upstream of the airfoil (C1), and another has contouring that starts upstream of the airfoil and continues until the airfoil’s trailing edge (C2).
Computed results show that at all swirl angles investigated, the C2 configuration was able to reduce significantly secondary flows on the contoured endwall. Results also show that with reduced secondary flows, the heat-transfer coefficients are also reduced on the suction surface next to the juncture, where the airfoil meets the contoured endwall. On aerodynamics, the C2 configuration was found to produce essentially the same lift as the C1 configuration, but does so with less loss in stagnation pressure. For the C1 configuration, secondary flows are quite pronounced, and they increase slightly in size and in magnitude when swirl angle is increased. However, aerodynamic loss and surface heat transfer were found to decrease with increase in swirl angle. One explanation is that increasing the swirl angle shifted the stagnation zone downstream on the pressure surface to a flatter portion of the airfoil, producing a thicker boundary layer at the stagnation zone, and this changed considerably the evolution of the turbulent boundary layer. When the swirl angle varied linearly from +30° to −30°, increasing the velocity component towards the pressure surface was found to enhance instead of suppress the formation of secondary flows.
Experimental Investigation of Micro Heat Pipe Radiators in Radiation Environment
Authors: Wang Y. X. , Peterson G. P. 
Published: November 2021

Abstract
A flexible micro heat pipe radiator, fabricated by sintering an array of aluminum wires between two thin aluminum sheets, was developed as part of a program to conceptulize, develop, and test lightweight, flexible radiator fin structures for use on long-term spacecraft missions. A detailed experimental investigation was conducted to determine the temperature distribution, maximum heat transport capacity, and radiation efficiency of these micro heat pipe radiators in a radiation environment. Experimental results from three Aluminum-Acetone micro heat pipe radiators with wire diameters of 0.635 mm, 0.813 and 1.016 mm are presented, evaluated and discussed.
The results of the experimental program indicted that the maximum heat transport capacity and radiation efficiency, both increased with increasing wire diameter. The maximum heat transport capacity of the micro heat pipe radiator utilizing a wire diameter of 0.635 mm was 15.2 W. The radiators utilizing wire diameters of 0.813 mm and 1.016 mm never reached the maximum heat transport capacities for the given test conditions. In the tests, temperature distributions were recorded for several sink temperatures and indicated that as the sink temperature decreased the radiation efficiency decreased for a given heat input. The maximum heat transport capacity increased with increasing evaporating temperature for the micro heat pipe radiator utilizing a wire diameter of 0.635 mm. Comparison of micro heat pipe radiators with and without working fluid, indicated that significant improvements in temperature uniformity and radiation efficiencies could be obtained, especially at high heat fluxes. A maximum radiation efficiency of 0.95 was observed. In general, while some variation in performance was observed, all three micro heat pipe radiators were found to be capable of meeting the thermal requirements of long-term missions.