bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of the Swirl Field on the Structure, Planner Drop Sizing and Large-Scale Instabilities of Flow-Blurring Spray
Authors: Gupta Abhishek Kumar , Yadav Keshav , Soni Surendra Kumar , Mishra Yogeshwar Nath , De Santanu 
Published: February 2024

Abstract
Effective atomisation is a governing parameter in a liquid-based gas turbine. Incorporating the swirling air with the spray influences the spray structure, drop dispersion, and large-scale unsteadiness. Therefore, reliable measurement of drop sizes, spray structure, and large-scale instabilities are necessary for the detailed analysis of the complex interaction of the spray droplets in the swirl airfield. We aim to investigate the spray structure, drop sizing, and large-scale unsteadiness of a flow-blurring (FB) spray under swirl airfield conditions. In previous studies, the drop size distribution in FB sprays in a stagnant medium has been characterized based on the point measurement tool, namely Phase Doppler Particle Analyzer (PDPA). However, the PDPA measurement is time-consuming, suffers issues related to multiple scattering in the dense region of the spray, and provides only the time-averaged statistics. Herein, we characterize FB spray under the influence of an external swirling air stream using structured laser illumination planar imaging (SLIPI) technique. The SLIPI technique eliminates unwanted optical signals due to the multiple scattering and provides shot-to-shot variations of the drop size mapping and spray structure.
A lab-scale experimental setup consisting of a centrally mounted FB atomiser with co-annular swirl air passage is operated at a fixed air-liquid mass ratio but with different swirl velocities. Following 1p-SLIPI technique, simultaneous Mie and LIF signals are recorded using two cameras, which are eventually used to obtain two-dimensional droplet Sauter mean diameter (SMD) contours. The calibration constant for the LIF/Mie ratio is deduced using PDPA measurements. The ensemble of instantaneous images is utilized for the proper orthogonal decomposition (POD) analysis to investigate the spatio-temporal features of the large-scale structure. The role of the swirling air on the different types of large-scale instabilities is explained based on the POD modes and energy contributions by the individual modes.
Studies on Unsteady Turbulence Flow Characteristics Associated With Stator-Rotor Interaction Originated Thermal Flow Phenomena Using a High Order LES Model
Authors: Biswas Debasish , Jimbo Tomohiko 
Published: February 2024

Abstract
Unsteady turbulence phenomena caused by stator-rotor interaction in today’s gas turbines which operates at higher temperature to meet the demand of increase in cycle performance by creating severe heat load in the turbine stages is a challenging problem worth paying attention. To avoid the damage of the material from high mean flow temperature cooling of both end-walls and the blades is very much essential. Understanding of the aerodynamics involved is important to implement the cooling technique. To study these phenomena 3-D unsteady Navier-Stokes analysis of a turbine stage is carried out as a base case. The experimentally observed effect of hot streak on the surface temperature distribution of the rotor blade and the unsteady pressure fluctuation associated with stator-rotor interaction are very well predicted by the numerical results. Since the flow associated with stator-rotor interaction is highly unsteady in nature, it is very important to have some understanding of the unsteady turbulence characteristics (unsteady nature of turbulence production and its dissipation and the corresponding fluctuation of pressure and temperature) in this type of thermal flow phenomena. After comparison of computed and experimental results, in our study emphasis is put to understand the unsteady turbulence characteristics based on turbulence production and its dissipation and the corresponding Q-criterion associated with stator-rotor interaction thermal flow phenomena.
Experimental Investigation of a Concentrated Photovoltaic System Integrated With Water Sprinkler Generating Electricity and Hot Water
Authors: Vyas Meet J. , Bhatt Devam , Shah Dev , Patel Lay , Banker Nitin 
Published: February 2024

Abstract
Power generation through solar photovoltaic (PV) is quite attractive due to direction generation of power from radiation and simplicity in construction. The major concern of the solar PV is 10–15% efficiency, i.e. larger land area requirement per kW of power generation. Concentrated solar PV system is one of the options to enhance the power generation in unit area. But the implication is increase in panel temperature, in turn, reducing the cell efficiency. The researchers proposed cooling of panels using water, air, phase change materials etc. to maintain lower temperature. This paper presents experimental investigation of a concentrating solar PV integrated with water sprinkler to enhance power and generate hot water. The experimentation has been performed in Ahmedabad, Gujarat (23.02°N, 72.57°E). Result analysis of various configurations of solar panels with and without concentrators and water sprinkler has been performed. To make sure the repeatability, each configuration has been experimented for two different days. Performance parameters such as electrical efficiency and overall efficiency have been used to compare the different configurations. The result analysis shows enhancement of power along with the generation of hot water in comparison to conventional solar PV system.
Topology Optimization Using Neural Network for Stress Constrained Problems
Authors: Shishir Md. Imrul Reza , Tabarraei Alireza 
Published: February 2024

Abstract
This paper introduces an innovative approach that utilizes neural networks to incorporate stress constraints into topology optimization. In this method, a neural network is trained to generate the topology density field using a loss function, while Fourier space projection is employed to control the length scale. The implementation takes advantage of JAX, a high-performance Python library for automatic differentiation, which enables end-to-end differentiability and automatic sensitivity analysis through backpropagation. The use of a neural network enables expressing the entire optimization process as a single differentiable function. This feature streamlines the optimization process and facilitates faster convergence, providing a significant advantage over conventional methods.
Model-Based Assist-as-Needed Control on a Provisional Pediatric Lower-Limb Orthosis
Authors: Wiebrecht Jason J. , Strick Jacob A. , Goo Anthony , Sawicki Jerzy T. 
Published: February 2024

Abstract
This paper describes the development and preliminary testing of a model-based assist-as-needed (MBAAN) controller for a provisional pediatric lower-limb exoskeleton. Assistive control methodologies for medical exoskeletons can vary drastically due to user-specific pathologies and therapy goals. The MBAAN controller presented combines a model-based assistive torque controller with an assist-as-needed control methodology, resulting in a user-specific assistive torque profile. The goal of this approach is to improve gait position reference tracking while decreasing user effort, quantified by user applied torque to the system. The controller uses a linearized model of the system identified through frequency response analysis to generate a preliminary assistance profile. The MBAAN controller utilized this torque profile along with position error weighting to provide assistance when the gait of a simulated user was underperforming a desired performance threshold. The controller was first implemented in simulation, and then in physical experimentation on a provisional hip-knee orthosis to guide a model leg. Both the simulation and physical experiment suggested that MBAAN control can provide subject-specific assistance. The results from the physical experiment demonstrated that the MBAAN controller reduced the root-mean-squared (RMS) position error by 21% and 22% for the hips and knees relative to the baseline comparison, respectively. The MBAAN controller was also able to reduce emulated user applied RMS torque to the system by 15% and 23% for the hips and knees, respectively. The results of this study suggest that MBAAN control can improve user gait tracking while reducing user effort on the provisional orthosis, motivating further assistive studies.
Mounting Systems for Electric Powertrains: Optimization and Parameter Sensitivity
Authors: Kaul Sudhir , Borra Chaitanya 
Published: February 2024

Abstract
Noise, vibration, and harshness (NVH) characteristics of electric powertrains have been receiving increasing attention due to the unique vibroacoustic characteristics of different electric motors commonly used in electric and hybrid vehicles. NVH characteristics of electric powertrains are unique due to several reasons including harmonics of electromagnetic forces, coupling of modes of the motor stator assembly, noise and vibration resulting from pulse width modulation, etc. While a traditional mounting system for an internal combustion engine typically needs to be designed for a frequency range of 0 to 200 Hz, the response of an electric powertrain is generally expected to exceed 2 kHz. Therefore, factors such as internal resonance, wave effects, and high-frequency noise and vibration are specifically unique to electric powertrains and their mounting systems. Two engine mounting configurations that have shown promising results for electric powertrains are the cradle mounting system (three-point mounting) and the saddle mounting system (four-point mounting). These two mounting systems provide a balance between mitigation of force transmissibility at lower and higher frequencies while being well-suited for transient loads. This paper investigates the sensitivity of force transmissibility and frequency response to some of the design parameters of the engine mounting systems for electric powertrains. The determination of optimal mounting system parameters is also investigated in this study. A spatial model with a discretized representation of each engine mount has been used for analysis since it is capable of capturing wave effects as well as high-frequency responses up to 10 kHz. Results indicate that the model can be used to determine an optimal configuration of the mounting system especially when a specific frequency bandwidth is targeted. The optimal four-mount system is seen to substantially reduce the overall force transmissibility. The viscoelastic parameters and the mass and inertia of the powertrain are not seen to influence the peak amplitudes of force transmissibility while slightly shifting the natural frequencies of the lower modes without influencing higher modes. The results of this study can be used for the design and development of robust mounting systems for electric powertrains while accounting for design constraints.
Prediction of Critical Heat Flux in Tube Bundles With Crossflow
Authors: Shah Mirza Mohammed 
Published: February 2024

Abstract
Evaporators and boilers with flow across horizontal tube bundles are widely used in industries including refrigeration and chemical processing. As yet there is lack of a well-verified correlation for predicting local or average CHF (critical heat flux) in such bundles. The available data and correlations are reviewed. The available methods for predicting bundle mean CHF were found to be too conservative. More realistic values of bundle average CHF are proposed based on published test data. The author’s well-verified correlations for CHF on a single tube with subcooled and saturated flow at zero quality across it are compared with test data for tubes in tube bundles together with other correlations. The author’s correlations agree well with all data while the others fail for data other than their own. Results of the comparison are presented and discussed. The needs for further research are identified.
Statistical Shape Modelling of the Lumbar Spine With Reference to Gender and Principal Component Analysis
Authors: Almalki Faris A. , Cortes Daniel H. 
Published: February 2024

Abstract
Numerical simulation of spine mechanics relies on anatomical features of the vertebrae. Statistical shape models aid in these simulations by including shape variability and differences between groups, facilitating finite element simulations for medical procedures. This study aims to develop a statistical shape model of the lumbar vertebrae and to determine shape differences between genders. This study used CT images and 3D segmentations from the Vertebrae Segmentation challenge (VerSe) with a total of 138 vertebrae from 46 patients consisting of L3, L4, and L5 vertebrae. From these segmentations, statistical shape models were created, using ShapeWorks software, for the overall and gender-specific means. Moreover, gender differences, principal component analysis and modes of variations were illustrated. Major differences in posterior elements between overall, male, and female means were identified. Regarding the principal component analysis, the first principal component accounted for 39.4% of the variation, which was distributed between the vertebrae in dissimilar patterns. The second principal component, accounting for 20.4% of the variation, was concentrated in L5. In conclusion, this study specifies locations in the lumbar vertebrae with significant differences between genders and identifies modes of variations in the sample using principal component analysis.
Attitude Control of a Satellite Applying the SDRE and H-Infinity Methods
Authors: Souza Luiz C. G. , Cubillos Ximena Celia Mendez 
Published: February 2024

Abstract
Space exploration is one of the main drivers of innovation and innovative technologies. Space missions are complex and high-cost procedure, involving several steps, where the Attitude Control System (ACS) needs to be robust, reliable and perform well. The ACS is responsible for the important phase that is injection of the satellite’s orbit where the angular velocities is extremely high until its attitude control associated with its normal mode of operation whose degree of pointing is extremely demanding compatible with the mission’s pointing requirements. The ACS of a satellite aims at determining and controlling the attitude of the satellite, and often cannot be repaired in space. On the others hand, when satellite dynamics involves plant uncertainties and large-angle maneuvers, linear control techniques are unable to design the ACS that meet the mission requirements. In this paper one investigates the performance and robustness of the union of the SDRE (State-dependent Riccati Equation) and the H-Infinite (H∞) control techniques. This investigation development a non-linear control algorithm with greater flexibility, which allows the space engineer to design an ACS with the balance between the performance of the SDRE technique with the robustness of the H∞ technique.
Design of Low Density Architectured Metamaterials With High Compressive and Torsional Stiffness
Authors: Liu Xiangbei , Jeon Joseph J. , Tiplea Anisia G. , Li Yan , Song Bo 
Published: February 2024

Abstract
Metamaterials are architected cellular networks with solid struts, plates, or shells that constitute the edges and faces of building cells. Certain metamaterial designs can balance light weight and high stiffness requirements, which are otherwise mutually exclusive in their bulk form. Existing studies on these materials typically focus on their mechanical response under uniaxial compression, but it is unclear whether a strut-based metastructure design with high compressive stiffness can exhibit high torsional stiffness simultaneously. Designing lightweight metastructures with both high compressive and torsional stiffnesses could save time and cost in future material development.
To explore the effect of unit cell design, unit cell number, and density distribution on both compressive and torsional stiffnesses, a computational design space was presented. Seven different unit cells, including three basic building blocks: body-centered cubic (BCC), face-centered cubic (FCC), and simple cubic (SC) were analyzed. All samples had a relative density of approximately 7%. It was found that a high compressive stiffness required a high concentration of struts along the loading direction, while a high torsional stiffness needed diagonal struts distributed on the outer face. Increasing unit cell numbers from 1 to 64 affected stiffness by changing the stress distribution globally. Non-uniform metastructure designs with strengthened vertical and diagonal struts towards the outer surface exhibited higher stiffness under either compressive or torsional loading. This study provides valuable guidelines for designing and manufacturing metamaterials for complex mechanical environments.
Investigation of the Influence of Nylon-6 vs. Nylon-66 on the Mechanical Performance of Composite Bone Tissue Scaffolds
Authors: Coburn Brandon , Joyce Robert , Salary Roozbeh (Ross) 
Published: February 2024

Abstract
Despite recent advances in bone tissue engineering, patient-specific treatment of bone pathology using porous osteoconductive scaffolds has faced clinical challenges, which to a great extent stem from a lack of mechanical strength as well as bioactivity (which are critical for osteogenesis, bone bridging, and ultimately bone healing). There is a need for synthesis of not only biocompatible, but also mechanically strong materials with low immunogenicity for bone regeneration. The goal of this industry-academia research work is to fabricate porous, biologically active, and mechanically robust bone tissue scaffolds for treatment of bone fractures, defects, and diseases. In pursuit of this goal, the overall objective of the work is to systematically investigate the effects of Nylon-6 as well as Nylon-66 on the mechanical properties of bone tissue scaffolds, fabricated using fused deposition modeling (FDM), which is a high-resolution additive manufacturing method.
In this study, the fabricated bone scaffolds were composed of cellulose fibers, polyamide (nylon), as well as polyolefin (referred to as PAPC hereafter), having complex internal microstructures, designed based on triply periodic minimal surfaces (including Schwarz Gyroid, Schwarz Primitive, Schwarz Diamond, and Neovius microstructures). Three types of scaffolding composite materials, i.e., PAPC-I (Nylon-6-based), PAPC-II (Nylon-6-based), and PAPC-V (Nylon-66-based) were utilized in this study. The FDM fabrication of the bone scaffolds was based on a microcapillary nozzle (heated at 215 °C for PAPC-II as well as 235 °C for PAPC-I and PAPC-V) with a diameter of 400 μm, a print speed of 10 mm/s, and a material flow of 120%. Material deposition was on a heated surface, kept at 80 °C for PAPC-II as well as 95 °C for PAPC-I and PAPC-V. A layer height and line width of 200 μm and 300 μm, respectively, were set for the 3D-fabrication process. To avoid filament breakage during the FDM material deposition process, retraction distance as well as retraction speed were reduced to 5 mm and 10 mm/s, respectively. In addition, due to the brittle nature of PAPC-V (having a high Nylon-66 content), it was preheated prior to feeding. The mechanical properties (such as elasticity modulus) of the FDM-fabricated bone scaffolds were characterized using compression testing. Overall, the outcomes of this study will pave the way for patient-specific fabrication of mechanically robust and bioactive bone tissue scaffolds with optimal medical properties for the treatment of bone pathology.
Effects of Foil Camber and Non-Zero Angle of Attack on The Unsteady Forces Produced by a Turbomachine Ingesting Turbulence
Authors: Owsley Isaiah J. , Goldschmidt Margalit Z. , Hanford Amanda , Lysak Peter , Jonson Michael L. 
Published: February 2024

Abstract
Turbomachinery rotor blades experience unsteady lift forces due to turbulence and circumferential variation in the inflow velocity. These forces can be a source of unwanted vibration and radiated sound. The unsteady force spectrum is often modelled to first order using a flat plate approach. However, it is known that mean loading effects can have a significant influence on airfoil unsteady lift for sinusoidal gusts with certain wavevector orientations [1]. To this end, the Atassi [1] gust response model for airfoils with camber and non-zero angle of attack has been incorporated into a rotor turbulence ingestion model [2] to determine the effect on the unsteady force spectrum. The Atassi gust model describes the interaction between a two-dimensional sinusoidal gust with a cambered foil placed at a small angle of attack to the mean flow. To apply this single harmonic gust response to the turbulence ingestion model, the gust responses for sinusoidal components with a distribution of wavevector angles are integrated based on an isotropic turbulence energy spectrum.
The updated turbulence ingestion model is then applied to a parametric study investigating the effects of foil geometry (specifically camber and non-zero angle of attack) on the unsteady forces produced from turbulence ingestion. The baseline geometry used for this study is the Sevik [3] rotor. To assess the sensitivity of the unsteady force spectrum to camber, predictions for a 0, 6, and 12% cambered foil with zero thickness at 0° angle of attack are generated. For these cases, foil camber effects are found to be largely negligible, except at low frequencies where the additional forces generated by streamwise gust components become dominant. The influence of non-zero angle of attack on the turbulence ingestion rotor force is also relatively minor for small angles of attack, but an increase of a few dB is predicted at higher frequencies as the angle of attack is increased to 15°. These results are generally consistent with measurements reported in the literature, where camber and angle of attack effects are shown to be weak, and the overall effects are much smaller than the changes in the sinusoidal gust responses due to the streamwise symmetry and averaging effect that occurs with isotropic turbulence. While the turbulence ingestion model was successfully extended to account for foil geometry effects using the Atassi gust response model, there is continued interest to explore the effects on the unsteady force spectrum when the simplifying assumption of isotropic turbulence is removed.
A Comparative Study on Insulation Materials in Tanks for the Storage of Cryogenic Fluids in Fire Incidents
Authors: Eberwein Robert , Hajhariri Aliasghar , Camplese Davide , Scarponi Giordano Emrys , Cozzani Valerio , Otremba Frank 
Published: February 2024

Abstract
Liquefied Hydrogen (LH2) or Liquefied Natural Gas (LNG) establish themselves as important energy carriers in the transport sector. Its storage requires tanks with Thermal Super Insulations (TSI) to keep the transported fluid cold. TSI has proven itself in various applications over a long time, but not in the land transport sector, where accidents involving collisions, fires, and their combination are to be expected. The focus of this study is to investigate the behavior of different types of TSI when exposed to a heat source that represents a fire. Therefore, a High-Temperature Thermal Vacuum Chamber (HTTVC) was used that allows the thermal loading of thermal insulation material in a vacuum and measuring the heat flow through the TSI in parallel. Within this study, 5 samples were tested regarding 3 different types of MLI, rock wool, and perlites. The thermal exposure caused different effects on the samples. In practice, this can be connected to the rapid release of flammable gases as well as a Boiling Liquid Expanding Vapour Explosion (BLEVE). These results are relevant for the evaluation of accident scenarios, the improvement of TSI, and the development of emergency measures.