bluuebunny/crossref_metadata_2025_split huggingface dataset:
Scalable Heat Transfer Characterization on Film Cooled Geometries Based on Discrete Green’s Functions
Authors: Saavedra Jorge , Athmanathan Venkat , Paniagua Guillermo , Meyer Terrence , Straub Doug , Black James , Ramesh Sridharan 
Published: January 2021

Abstract
The aerothermal characterization of film-cooled geometries is traditionally performed at reduced temperature conditions, which then requires a debatable procedure to scale the convective heat transfer performance to engine conditions. This paper describes an alternative engine-scalable approach, based on Discrete Green’s Functions (DGF) to evaluate the convective heat flux along film-cooled geometries. The DGF method relies on the determination of a sensitivity matrix that accounts for the convective heat transfer propagation across the different elements in the domain. To characterize a given test article, the surface is discretized in multiple elements that are independently exposed to perturbations in heat flux to retrieve the sensitivity of adjacent elements, exploiting the linearized superposition. The local heat transfer augmentation on each segment of the domain is normalized by the exposed thermal conditions and the given heat input. The resulting DGF matrix becomes independent from the thermal boundary conditions, and the heat flux measurements can be scaled to any conditions given that Reynolds number, Mach number, and temperature ratios are maintained. The procedure is applied to two different geometries, a cantilever flat plate and a film-cooled flat plate with a 30 degree 0.125 in. cylindrical injection orifice with length-to-diameter ratio of 6. First, a numerical procedure is applied based on conjugate 3D unsteady Reynolds-averaged Navier–Stokes (URANS) simulations to assess the applicability and accuracy of this approach. Finally, experiments performed on a flat plate geometry are described to validate the method and its applicability. Wall-mounted thermocouples are used to monitor the surface temperature evolution, while a 10 kHz burst-mode laser is used to generate heat flux addition on each of the discretized elements of the DGF sensitivity matrix.
Effects of Attack Angle and Relative Thickness of Novel Wing-Shaped Turbulators on Turbulent Hydrothermal Performance in a Two-Pass Square Channel
Authors: Liou Tong-Miin , Chen Chieh-Chu , Wang Chun-Sheng 
Published: January 2021

Abstract
This work aims to combine the effects of the near-wall and core flow disturbance by proposing novel wing-shaped turbulators. The new turbulators are fabricated with the fused deposition modeling (3D printing) technology. To explore their effects on detailed flow fields, local temperature distributions, and pressure drops in a two-pass square channel, particle image velocimetry (PIV), infrared thermography (IR camera), and pressure transducer measurements are performed. The turbulator pitch, clearance, and truncation gap ratio based on the channel hydraulic diameter of 45.5 mm are, respectively, fixed at 0.7, 0.25, and 0.06. Varied parameters include turbulator attack angle (α = 10 deg, 15 deg, 20 deg, and 30 deg), maximum thickness to chord line ratio (t/C = 0.08, 0.13, 0.16, 0.20, and 0.23), and bulk Reynolds number (Re = 5000–20,000). From the experimental results and flow parameters analyzed, the dimensionless spanwise-averaged mean transverse velocity and cross-sectionally averaged vorticity magnitude are identified to be the most relevant ones to spanwise-averaged local Nusselt number ratio in the first and second pass. Among all examined cases and previous data with Fanning friction factor ratio (f¯/fo) less than 50, the case with α = 20 deg and t/C = 0.20 attains the highest thermal performance factor (TPF) and overall Nusselt number ratio Nu¯/Nuo up to 1.68 and 5.36, respectively. Furthermore, empirical correlations of Nu¯/Nuoandf¯/fo versus α, t/C, and Re are proposed.
A Perturbation Analysis Approach for Studying the Effect of Swelling Kinetics on Instabilities in Hydrogel Plates
Authors: Ilseng Arne , Skallerud Bjørn H. , Stokke Bjørn T. , Prot Victorien 
Published: January 2021

Abstract
The onset of surface instability during diffusion-driven swelling of hydrogels depends on the kinetics of the swelling process. Here, we outline a perturbation analysis framework using a finite difference approach for calculating the stability limit of swelling hydrogel plates with graded material properties accounting for kinetic effects. The framework is implemented as a Python routine which is made freely available. Results obtained for bilayered hydrogel plates illustrate that the onset of instability occurs earlier in time and at a lower global swelling ratio when kinetics is accounted for compared to the homogeneous swelling case. This work presents an accessible calculation tool for stability analysis of swelling gels, providing input for the design of novel hydrogel systems.
Shortcut Method for “L” and “Z” Pipe Bend Sizing
Authors: Jaćimović Nikola , Ivošević Miloš 
Published: January 2021

Abstract
In the engineering practice, it may often prove necessary to provide quick and relatively accurate estimates of piping routing and material requirements in very early stages of a project. In these cases, there is typically no time to perform detailed pipe stress analysis in order to obtain accurate routing, which allows for sufficient piping system flexibility, and the designer is constrained to the use of rule of thumb approach and good engineering judgment. This approach, although often used, may prove challenging in many situations, one of which is establishing sufficient pipe loop dimensions. Method proposed by the authors in Jacimovic and Ivosevic (2020, “Shortcut Method for Pipe Expansion Loop Sizing,” ASME J. Pressure Vessel Technol. 142(4), p. 041505) provides a procedure for quick estimation of U loops, while the present procedure aims to provide additional procedures for estimation of L and Z bends, thus completing the circle of shortcut methods for quick estimation of expansion requirements of piping systems.
Experimental Investigations on the Pressure Fluctuations in the Sealing Gap of Dry Gas Seals With Embedded Pressure Sensors
Authors: Luo Jingjing , Brillert Dieter 
Published: January 2021

Abstract
Dry gas–lubricated noncontacting mechanical seals (DGSs), most commonly found in centrifugal compressors, prevent the process of gas flow into the atmosphere. Especially when high speed is combined with high pressure, DGS is the preferred choice over other sealing alternatives. Even though the noncontacting seal is proved reliable, the ultrathin gas film can still lead to a host of potential problems due to possible contact. In order to investigate the flow field in the sealing gap and to facilitate the numerical prediction of the seal performance, a dedicated test facility is developed to carry out the measurement of key parameters in the gas film. Gas in the sealing film varies according to the seal inlet pressure, and the thickness of gas film depends on this fluctuated pressure. In this paper, the test facility, measurement methods, and the first results of static pressure measurements in the sealing gap of the DGS obtained in the described test facility are presented. An industry DGS with three-dimensional grooves on the surface of the rotating ring, where experimental investigations take place, is used. The static pressure in the gas film is measured, up to 20 bar and 8100 rpm, by several high-frequency ultraminiature pressure transducers embedded into the stationary ring. The experimental results are discussed and compared with the numerical model programed in matlab (Luo, J., Dohmen, H. J., and Benra, F. K., 2018, “Coupled Thermal-Structural-Fluid Numerical Analysis of Gas Lubricated Mechanical Seals,” ASME Paper No. GT2018-75458), the characteristic and magnitude of which have a good agreement with the numerical simulations. It suggests the feasibility of measuring pressure profiles of the standard industry DGS under pressurized dynamic operating conditions without altering the key components of the seal, and thereby affecting the seal performance.
On the Efficiency of a Conical Underplatform Damper for Turbines
Authors: Denimal E. , Wong C. , Salles L. , Pesaresi L. 
Published: January 2021

Abstract
Underplatform dampers (UPDs) are commonly used in aircraft engines to limit the risk of high-cycle fatigue of turbine blades. The latter is located in a groove between two consecutive blades. The dry friction contact interface between the damper and the blades dissipates energy and so reduces the vibration amplitudes. Two common geometries of dampers are used nowadays, namely wedge and cylindrical dampers, but their efficiency is limited when the blades have an in-phase motion (or a motion close to it), since the damper tends to have a pure rolling motion. The objective of this study is to analyze a new damper geometry, based on a conical shape, which prevents from this pure rolling motion of the damper and ensures a high kinematic slip. The objective of this study is to demonstrate the damping efficiency of this geometry. Hence, in a first part, the kinematic slip is approximated with analytical considerations. Then, a nonlinear dynamic analysis is performed, and the damping efficiency of this new geometry is compared to the wedge and the cylindrical geometries. The results demonstrate that the conical damper has a high damping capacity and is more efficient and more robust than the two others.
Optimal Estimation of the Roughness Coefficient and Friction Factor of a Pipeline
Authors: Santos-Ruiz Ildeberto , López-Estrada Francisco-Ronay , Puig Vicenç , Torres Lizeth , Valencia-Palomo Guillermo , Gómez-Peñate Samuel 
Published: January 2021

Abstract
This work addresses the estimation of two interrelated parameters of the fluid flow in pipes. First, a numerical and experimental evaluation of some proposed methods to compute the friction factor in turbulent regime is presented. Special attention is given to an explicit solution obtained through the Lambert W-function. Subsequently, a method to estimate the roughness coefficient using nonlinear optimization techniques is proposed, which then allows determining the friction factor from it. Numerical tests were performed for a wide range of operating points of a pipeline. In order to validate the proposed approach, experimental analysis was carried out on a pipeline pilot-plant. The results show the applicability and effectiveness of the proposed method.
Computational Simulation of Spontaneous Liquid Penetration and Depression Between Vertical Parallel Plates
Authors: Naghashnejad Mohammad , Shabgard Hamidreza , Bergman Theodore L. 
Published: January 2021

Abstract
A computational fluid dynamics model is developed to study the dynamics of meniscus formation and capillary flow between vertical parallel plates. An arbitrary Lagrangian–Eulerian approach is employed to predict and reconstruct the shape of the meniscus with no need to employ implicit interface tracking schemes. The developed model is validated by comparing the equilibrium capillary height and meniscus shape with those predicted by available theoretical models. The model was used to predict the capillary flow of water in hydrophilic (silver) and hydrophobic (Teflon) vertical channels with wall spacings ranging from 0.5 mm to 3 mm. It is shown that the computational model accurately predicts the capillary flow regardless of the channel width, whereas the theoretical models fail at relatively large wall spacings. The model captures several important hydrodynamic phenomena that cannot be accounted for in the theoretical models including the presence of developing flow in the entrance region, time-dependent formation of the meniscus, and the inertial effects of the liquid in the reservoir. The sharp interface tracking technique enables direct access to the flow variables and transport fluxes at the meniscus with no need to use averaging techniques.
High Pressure Vertical Axis Wind Pump
Authors: Keisar D. , Eilan B. , Greenblatt D. 
Published: January 2021

Abstract
A novel positive displacement, high pressure, vertical axis wind pump (HP-VAWP) was evaluated for the application of stand-alone high-pressure reverse-osmosis desalination and drip irrigation systems. The direct interface between a vertical axis wind turbine (VAWT) and a positive displacement pump that delivers a constant liquid volume per revolution has never been studied before. Understanding the interaction between turbine and pump efficiencies, where delivery pressure is determined by back-pressure alone, is critical for efficient design. Wind tunnel experiments were conducted on a small-scale two-bladed turbine (0.4 m2 cross-sectional area) that operated on a dynamic stall principle. At these small laboratory scales, the turbine and pump peak efficiencies were relatively low (15% and 28%, respectively); nevertheless, the system produced nearly constant pressures in excess of 1.5 bar for a broad operational range. Moreover, the system exhibited a basic self-priming capability, and the turbine could easily be braked by overloading the pump. A conservative field-scale analysis of an HP-VAWP system indicated that a medium-size turbine (12.5 m2 cross-sectional area) could attain a peak efficiency of 12.9%. Realistic efficiencies greater than 20% are attainable, significantly exceeding the 4%–8% typical peak efficiency of the widely used American multibladed wind pumps. Indeed, our research indicates that an HP-VAWP system is viable and requires further development. The benefits of zero carbon emissions during operation, high relative efficiency, and easy manufacturing and maintenance render the HP-VAWP ideal for stand-alone or off-grid environments.
Synergistic Technology Combinations for Future Commercial Aircraft Using Liquid Hydrogen
Authors: Rompokos Pavlos , Rolt Andrew , Nalianda Devaiah , Isikveren Askin T. , Senné Capucine , Gronstedt Tomas , Abedi Hamidreza 
Published: January 2021

Abstract
Liquid hydrogen (LH2) has long been seen as a technically feasible fuel for a fully sustainable greener aviation future. The low density of the cryogenic fuel would dictate the redesign of commercial aircraft to accommodate the large tanks, which are unlikely to be integrated within the whole internal volume of the wing. In the ENABLEH2 project, the morphological aspects of a LH2 aircraft design are discussed and a methodology for rapid concept comparative assessment is proposed. An exercise is then carried on to down-select short-to-medium range (SMR) and long-range (LR) concepts, able to carry 200 passengers for 3000 nmi and 414 passengers for 7500 nmi, respectively. The down-selection process was split into two phases with the first considering 31 potential airframe architectures and 21 propulsion-system arrangements. The second phase made the final down-selections from a short-list of nine integrated design concepts that were ranked according to 34 criteria, relating to operating cost, revenue, noise, and safety. Upon completion of the process, a tube and wing design with the tanks integrated into extended wing roots, and a blended-wing-body design were selected as the best candidates for the SMR and LR applications, respectively. Both concepts feature distributed propulsion to maximize synergies from integrating the airframe and propulsion systems.
Dynamic Instability Analysis of a Spring-Loaded Pressure Safety Valve Connected to a Pipe by Using Computational Fluid Dynamics Methods
Authors: Zheng Fengjie , Zong Chaoyong , Zhang Chao , Song Xueguan , Qu Fuzheng , Dempster William 
Published: January 2021

Abstract
As the ultimate protection of a pressure system, pressure safety valves (PSV) can respond in an unstable manner in the form of flutter and chatter, which will affect service life, reliability, and performance. In order to study the dynamic instability caused by multisource forces including the flow force, the spring compression force, and the pressure wave forces, a high-fidelity computational fluid dynamics (CFD) model of the system is proposed. A complete CFD model, incorporating the PSV, connected pipes, and the pressure vessel, is developed, in which advanced techniques in Fluent using User Defined Function (UDF) and Dynamic Layering method are combined to allow the PSV to be coupled to the system dynamics. Based on this model, the valve's opening and reclosing process is monitored to examine the influence of design parameters on the dynamic instability of the PSV. Specifically, the propagation of pressure waves along the connecting pipes is successfully captured, helping to assess the instability mechanism and provide the ability to optimize the design and setup of pressure relief systems.
Effect of Different Fuels on Combustion Instabilities in an Annular Combustor
Authors: Rajendram Soundararajan Preethi , Vignat Guillaume , Durox Daniel , Renaud Antoine , Candel Sébastien 
Published: January 2021

Abstract
Combustion instability in annular combustors of jet engines is a recurring issue. In this study, the characteristics of instabilities for different fuels are investigated by combining the instability maps obtained in a laboratory-scale annular combustor equipped with multiple swirling spray injectors (MICCA-spray) and flame describing functions (FDFs) from a single sector configuration (SICCA-spray). Two types of liquid fuels are injected as hollow cone sprays: heptane, which is fairly volatile, and dodecane, which is less volatile. Experiments are also conducted with gaseous propane, perfectly premixed with air, which serves as a reference. An instability map is systematically drawn by varying the global equivalence ratio and thermal power. The data indicate that the amplitude and frequency of instabilities depend, for the same operating point, on the fuel injection conditions (premixed or spray) and fuel type. Overall trends show that premixed propane is unstable in a broad operating domain. Injection of liquid fuels induces changes in flame time lag that modifies the unstable regions. For heptane, the instability map is closer to the propane reference map, whereas dodecane exhibits wider stable regions. An attempt is made to understand these features by examining the FDF, which gives the ratio of relative fluctuations in heat release rate to the relative fluctuations in velocity. The FDFs measured in a single sector configuration give access to gain and phase information that can be used to determine unstable bands and calculate an instability index guiding the interpretation of the differences in instabilities of the three fuels.
Simulation of Premixed and Partially Premixed Jet-in-Crossflow Flames at High Pressure
Authors: Stiehl Bernhard , Otero Michelle , Genova Tommy , Worbington Tyler , Reyes Jonathan , Martin Scott , Velez Carlos , Ahmed Kareem 
Published: January 2021

Abstract
In this paper, we explore the operational map of a lean axial-staged combustor of premixed and partially premixed reacting jet-in-crossflow flames at high -pressure (5 atm). This study attempts to expand the data to relatively high pressure and could significantly aid scaling to real gas turbine engine conditions at 20–30 atm. High-speed camera, particle image velocimetry (PIV), CH* chemiluminescence, temperature, and pressure measurements were taken and processed to allow accurate reconstruction of six operating points relative to computational fluid dynamics (CFD) simulations under minimal adjustments. Variation of lean main stage (φ = 0.575 and 0.73) and rich jet (φ = 1.1, 4, and 8) equivalence ratio has been investigated for a four mm axial jet. The fully premixed flames were found to be controlled by the crossflow temperature before ignition and the crossflow oxygen content during combustion. Analysis of flame shape and position for the partially premixed operating points describes a lee stabilized as well as a more unsteady windward flame branch. Adjustment of added jet fuel and crossflow temperature along with its corresponding oxygen level is required to attain a compact flame body. The risk of delaying combustion progress is significantly increased at a richer jet φ = 8 and an overshooting, spatially divided flame was attained with a main stage φ = 0.73. Control toward a compact flame body is critical to allow combustion at reasonable reaction rate.
Investigations on the Tribological Characteristics of TiO2-Doped Nanofluid Fuel (Biodiesel/Diesel Blend) at Different Contact Parameters
Authors: Saxena Vishal , Kumar Niraj , Saxena Vinod Kumar 
Published: January 2021

Abstract
The fuels (diesel/biodiesel blends) for diesel engines must possess a minimum of lubricating characteristics to prolong the life of some of the engine vital parts lubricated by the fuel itself. Hence, the tribological characteristic of the modified nanofluid fuel blends needs to be investigated for its suitability and sustainability. In the present study, an experimental analysis on the tribological aspect of fuel blends comprising 40% Acacia concinna biodiesel and 60% diesel (by volume) mixed with titanium dioxide (TiO2) nanoparticles in a concentration of 50–200 mg/l was conducted. The prepared fuel blends in varying volume concentrations were tested on a four-ball tribotester. The effects of varying operating parameters such as load and temperature as well as oxidation of biodiesel fuel blend on friction and wear behavior were evaluated with the help of three-dimensional (3D) surface plots (response surface methodology approach). Further, wear patch diameter, wear debris, wear volume, and flash temperature parameter were analyzed using optical micrographs and ferrographs. The obtained results revealed that despite having an influence of all parameters, the effect of TiO2 nanoparticles is more significant in improving the antiwear/friction characteristics of modified nanofluid fuel blends. It was observed that a TiO2 concentration of 150 mg/l in fuel blend was found to be the most suitable to reduce the friction, wear, and wear volume compared with those of diesel and biodiesel blend.
Multiscale Tomographic Wave–Matter Interaction Modeling to Enable Artifact-Free Material Defect Reconstruction
Authors: Steuben John C. , Michopoulos John G. , Iliopoulos Athanasios P. , Graber Benjamin D. , Birnbaum Andrew J. 
Published: January 2021

Abstract
Technologies for material defect detection/metrology are often based on measuring the interactions between defects and waves. These interactions frequently create artifacts that skew the quantitative character of the relevant measurements. Since defects can have a significant impact on the functional behavior of the materials and structures they are embedded in, accurate knowledge of their geometric shape and size is necessary. Responding to this need, the present work introduces preliminary efforts toward a multiscale modeling and simulation framework for capturing the interactions of waves with materials bearing defect ensembles. It is first shown that conventional approaches such as ray tracing result in excessive geometric errors. Instead, a more robust method employing solutions to the wave equation (calculated using the Finite Element Method) is developed. Although the use of solutions to the general wave equation permits application of the method to many wave-based defect detection technologies, this work focuses exclusively on the application to X-ray computed tomography (XCT). A general parameterization of defect geometries based on superquadratic functions is also introduced, and the interactions of defects modeled in this fashion with X-rays are investigated. A synthetic two-dimensional demonstration problem is presented. It is shown that the combination of parameterization and modeling techniques allows the recovery of an accurate, artifact-free defect geometry utilizing classical inverse methods. The path forward to a more complete realization of this technology, including extensions to other wave-based technologies, three-dimensional problem domains, and data derived from physical experiments is outlined.