bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flow Behavior and Heat Transfer Characteristics Between Outer and Slotted Inner Cylinders
Authors: Yuasa Tomohisa , Kaneko Akiko , Abe Yutaka 
Published: October 2021

Abstract
The performance of air-cooled generators can be improved only if they have efficient system designs for heat removal. An air-cooled generator is composed of a pair of coaxial cylinders, namely, a fixed outer cylinder (stator) and a rotating inner cylinder (rotor); the rotor has axial slits. In this study, we experimentally and numerically clarified the flow behavior and the heat transfer characteristics of rotating coaxial cylinders by simulating a salient-pole rotor in an air-cooled generator. The flow behavior in the slit between the salient poles was observed by using a high-speed video camera. We measured the temperature on the slit walls to investigate the heat transfer. The velocity fields and the heat transfer coefficient between the rotor and the stator were obtained via a numerical simulation. From the results, we experimentally and numerically observed the vortex structure in the slit. The local Nusselt numbers on the front-side wall of the slits near the impinging flow were higher than those on the back-side wall near the separated flow. The local Nusselt numbers on the front-side wall were high because the gap flow between the cylinders impinged on the front-side wall and promoted heat transfer. By contrast, the local Nusselt numbers on the back-side wall were low because a separated flow appeared near the back-side wall, where the hot fluid was retained, thereby causing the separated flow to disturb the heat transfer on the back-side wall.
Remaining Useful Life Estimation and Prognostication of SAC305 Printed Circuit Boards for Dynamic Conditions of Temperature and Vibration Loads
Authors: Lall Pradeep , Thomas Tony , Blecker Ken 
Published: October 2021

Abstract
This study focuses on the feature vector identification and remaining useful life (RUL) estimation of SAC305 solder alloy printed circuit boards (PCBs) of two different configurations during varying conditions of temperature and vibration. The feature vectors are identified using the strain signals acquired from four symmetrical locations of the PCB at regular intervals during vibration. Two different types of experiments are employed to characterize the PCB's dynamic changes with varying temperature and acceleration levels. The first type of analysis emphasizes the vibration characteristic for varying acceleration conditions while holding the temperature levels constant, and the second studies the shift in characteristics for various ambient temperatures by maintaining constant acceleration levels. The above analyses attempt to imitate an electronic board's actual working conditions in an automobile subjected to varying temperature and vibration environments. The strain signals acquired during each of these experiments are compared based on both time and frequency domain characteristics. Different statistical and frequency-based techniques were used to identify the strain signal variations with changes in the environment and loading conditions. The feature vectors in predicting failure at a constant working temperature and load were identified, and as an extension to this work, the effectiveness of the feature vectors during varying conditions of temperature and acceleration levels is investigated. The principal component analysis (PCA) is used as the data reduction and pattern recognition technique to the different operating conditions of vibration environments. The residual of the autocorrelation function (ACF) of frequency and instantaneous frequency (IF) matrices shows behavior that can predict the packages' failure on the PCB irrespective of varying conditions of temperature and acceleration levels. This feature vector's effectiveness is verified on two different configurations of PCB and for the two separate analyses discussed prior in the study. The RUL of the packages was estimated using a deep learning approach based on long short-term memory (LSTM) network. This technique can identify the underlying patterns in multivariate time series data that can predict the packages' life. The ACF's residuals were used as the multivariate time series data in conjunction with the LSTM deep learning technique to forecast the packages' life at different varying temperatures and acceleration levels during vibration.
Effect of Synthesis Procedure on Particle Dispersion and Hardness of Al- Sic Functionally Graded Metal Matrix Composite
Authors: Hassan Noha M. , Antar May , Saleem Natalie , Aboukhelil Sara , Ghonim Lina 
Published: October 2021

Abstract
Fabrication of Functionally Graded Metal Matrix Composites (FGMMC) especially with high ceramic reinforcement's volume fraction is highly challenging. Depending on the processing technique and process parameters various defects may arise. This research aims to find the best procedure to make FGMMCs with the highest quality and minimum cost. A new method is proposed that incorporates lost-foam and melt infiltration with semicentrifugal casting to produce FGMMC. Experiments were performed to in-situ fabricate 6061-Aluminum alloy reinforced with gradient distributed Silicon carbide particles (Al/SiC FGMMC). Effect of SiC %, Al pouring temperature and rotational speed on the fabricated specimens hardness and reinforcement gradient were investigated using design of experiments and regression analysis. Results reveal the optimum procedure and process settings based on desired properties/gradient required. Mathematical model formulated captures the effect of these process parameters on process cost, and cost of poor quality. Improper selection of those parameters may lead to extensive losses due cost of poor quality which is 12 times higher than the material cost. The proposed manufacturing process proved satisfactory in ensuring proper dispersion. A desirability function can by used to determine the process parameters and volume fraction that minimizes the defects and gives superior properties for a specific application.
Comparative Analysis of the Wear Performance of Spindle Hook Teeth During Fieldwork
Authors: Gu Yanqing , Zhang Hongwen , Fu Xiuqing , Wang Lei , Wang Jun , Cai Yunxiao , Li Haiyang 
Published: October 2021

Abstract
The wear performance of the spindle hook teeth during fieldwork was compared, and the causes of the wear failure of the spindle hook teeth were analyzed. Samples of three kinds of spindle were obtained from the fixed installation position under continuous field operation conditions. The hardness, phase structure, elemental composition, and micromorphology of the spindle hook teeth were characterized using microhardness, X-ray diffractometer (XRD), energy spectrum analyzer (EDS), and scanning electron microscope (SEM) after cutting of the spindles. Results show that the coating hardness and element penetration zone of No.3 spindle hook tooth are the largest, and the surface coating phase structure of the three kinds of the spindle is mainly a body-centered cubic structure of Cr (211). Micro-crack and hole defects exist in the coating of all three kinds of the spindle. The thicknesses of the coating of No.1, No.2, and No.3 spindles are 74, 100, and 130 µm, respectively. During the field operation, the wear of the spindle hook tooth coating is caused by abrasive wear and fatigue wear, while the wear of the substrate is the result of the combined effect of abrasive wear and oxidation wear. Extracting the wear area and width of spindle hook teeth shows that the wear area of all three kinds of spindle hook teeth increases exponentially and the wear width changes linearly with the increase in the field operation area.
Online Signal Denoising Using Adaptive Stochastic Resonance in Parallel Array and Its Application to Acoustic Emission Signals
Authors: Kim Jinki , Harne Ryan L. , Wang K. W. 
Published: October 2021

Abstract
Signal denoising has been significantly explored in various engineering disciplines. In particular, structural health monitoring applications generally aim to detect weak anomaly responses (including acoustic emission (AE)) generated by incipient damage, which are easily buried in noise. Among various approaches, stochastic resonance (SR) has been widely adopted for weak signal detection. While many advancements have been focused on identifying useful information from the frequency domain by optimizing parameters in a post-processing environment to activate SR, it often requires detailed information about the original signal a priori, which is hardly assessed from signals overwhelmed by noise. This research presents a novel online signal denoising strategy by utilizing SR in a parallel array of bistable systems. The original noisy input with additionally applied noise is adaptively scaled, so that the total noise level matches the optimal level that is analytically predicted from a generalized model to robustly enhance signal denoising performance for a wide range of input amplitudes that are often not known in advance. Thus, without sophisticated post-processing procedures, the scaling factor is straightforwardly determined by the analytically estimated optimal noise level and the ambient noise level, which is one of the few quantities that can be reliably assessed from noisy signals in practice. Along with numerical investigations that demonstrate the operational principle and the effectiveness of the proposed strategy, experimental validation of denoising AE signals by employing a bistable Duffing circuit system exemplifies the promising potential of implementing the new approach for enhancing online signal denoising in practice.
Estimation of Turbulent Length Scales at a Turbocharger Inlet Using Particle Image Velocimetry
Authors: Banerjee Deb , Selamet Ahmet , Dehner Rick 
Published: October 2021

Abstract
Stereoscopic Particle Image Velocimetry measurements are carried out at the inlet of a turbocharger compressor at four different shaft speeds from 80,000 rpm to 140,000 rpm and over the entire range of flow rates from choke to mild surge. This paper describes the procedure used in processing the PIV data leading to the estimates of turbulent length scales – integral, Taylor, and Kolmogorov, to enhance the fundamental understanding and characterization of the compressor inlet flow field. The analysis reveals that at most operating conditions the three different length scales have markedly different magnitudes, as expected, while they have somewhat similar qualitative distributions with respect to the duct radius. For example, at 80,000 rpm and at a flow rate of 15.7 g/s (mild surge), the longitudinal integral length scale is of the order of 15 mm, the Taylor scale is around 0.5 mm, and the Kolmogorov scale is about 10 microns. With the onset of flow reversal, the turbulent kinetic energy and turbulent intensity at the compressor inlet are observed to increase rapidly, while the magnitudes of the Kolmogorov scale and to a certain extent, the Taylor scale are found to decrease suggesting that the increased turbulence gives rise to even smaller flow structures. The variation of length scales with compressor shaft speed has also been studied.
CFD Modelling for Gas-Liquid and Liquid-Liquid Taylor Flows in the Entrance Region of Microchannels
Authors: Etminan Amin , Muzychka Yuri S. , Pope Kevin 
Published: October 2021

Abstract
This paper presents a CFD-based simulation method for air/water and water/dodecane Taylor flows through an axisymmetric microchannel with a circular cross-sectional area. A systematic analysis is conducted by exploring the effects of different superficial velocities and apparent viscosities on the hydrodynamics of a slug flow regime. A concentric junction is employed to make bubbles of air in a continuous flow of water and slugs of water in a continuous flow of dodecane oil. A time-history study is conducted to predict the air-bubble and water-slug evolution processes, in particular at the moment of slug breakup. The results show that the larger apparent viscosity ratio of phases involved in the liquid-liquid flow generates a more stable interface. However, the liquid slug length is less and film thickness is slightly larger in liquid-liquid compared to gas-liquid flow. Furthermore, variations in gas and liquid holdups are correlated by the superficial velocity ratio. The numerical analysis developed in this paper is in good agreement with the correlations and data in the literature.
Experimental Study on Heat Transfer of Dielectric Barrier Discharge Plasma Actuator Considering Heat Conduction of Dielectric Material
Authors: Hatamoto Asami , Emori Kenta , Nishida Hiroyuki 
Published: October 2021

Abstract
The plasma actuator is an active flow control device utilizing the atmospheric dielectric barrier discharge. It has many advantages, and it is expected to be applied to a number of fluidic machines including enhancement of convection cooling. However, there is a significant problem when we apply the plasma actuator in the field of cooling, that is the actuator itself is a heat generation source due to the discharge. Although some research efforts have been devoted to understanding the heating characteristics of the plasma actuators, they made discussions only on the surface temperature, and any quantitative discussions on the amount of heating to the dielectric were not performed. The purpose of this study is to quantitatively discuss the heat transfer to the dielectric surface of the plasma actuator. For this purpose, the heat transfer coefficient and temperature of the wall-surface jet are estimated by applying it to a theoretical solution of the one-dimensional heat conduction inside the actuator. The time variation of temperature of the dielectric surface is measured using the IR camera. As a result, the estimation was reasonable near the electrode edge, but unphysical values were obtained downstream because of the small temperature rise and two-dimensional heat conduction in the dielectric. In the future, we need to analyze considering two-dimensional heat conduction utilizing numerical calculation.
Movement of Myoblast Flowing Through Electric Field Perpendicular to Flow Channel
Authors: Hashimoto Shigehiro , Yoshinaka Kiyoshi 
Published: October 2021

Abstract
The sorting technology with little invasion to cells would be applied to regenerative medicine and diagnosis. In this study, dielectrophoresis is focused on. The dielectrophoretic effect on the flowing myoblasts was maximized by adjusting several parameters: the shape of the electrodes, the amplitude and frequency of the alternating current. The suspension of C2C12 (mouse myoblast cell line) was injected into the channel, and the movement of each flowing cell was analyzed at the microscopic movie image. A pair of titanium-coated (200 nm thick) asymmetric surface electrodes (a triangular electrode with a tip angle of 0.35 rad and a rectangular reference electrode with a flat edge) was manufactured by photolithography technique. With the alternating square cyclic wave at the frequency of 3 MHz and the amplitude of current of ± 7.5 mA, 70 μm movement along the electric field (perpendicular to the main flow direction) of the cell was obtained. The movement along the electric field is governed by several parameters of the cell: the diameter, the deformation ratio, and the direction of the major axis. The method can be applied to cell sorting.
Impacts of Circular Liquid Jet Injection Angle Into Low Subsonic Crossflow
Authors: Kasmaiee Si. , Tadjfar M. , Kasmaiee Sa. 
Published: October 2021

Abstract
One of the most common ways to obtain mixing between liquid and air, is by injecting the liquid jet into an incoming gaseous crossflow. The physics of this mixing flow is very complicated due to the presence of many flow interfacial instabilities. Usually, a perpendicular liquid jet into the cross flow airstream is used as the standard method of mixing. In the present work, the effect of the injection angle of the liquid flow emanated from a circular nozzle into airstream was experimentally investigated. The flow characteristics of the liquid jet were visualized by diffused backlight shadowgraph technique and high-speed photography. Water was used as the working liquid and tests were conducted into an incoming airstream at room temperature and pressure. A circular nozzle with 1.5 mm in diameter was used. The injection angles of the 30, 45, 60 and 90 degrees of the liquid jet into the airstream were considered. Different parameters of liquid jet flow such as breakup length and trajectory were measured. It was found that at low angles the path was independent from the momentum ratio.
Volume of Fluid Simulations of Copper Droplet Splat and Sensitivity to Modeling Methods
Authors: Florio Laurie A. 
Published: October 2021

Abstract
Liquid droplet interactions with solid surfaces are fundamental to a wide range of phenomena from novel manufacturing processes, ice accretion on surfaces, to ablation and fouling build-up when droplets are carried with fluid flow along a flow path. Computational fluid-dynamics based simulations offer a controlled environment in which to explore the details of the droplet motion, deformation, or break-up and solidification and melting as droplet impingement on a surface occurs. The operating, material, or geometric conditions can be altered and the resulting changes in the droplet related phenomena can be used to gain the information needed to control the droplet related processes for an intended purpose. The present work investigates the sensitivity of the predicted splat development as a single copper droplet impact upon a cool copper substrate to variations in a volume of fluid based computational modeling method.
One liquid copper droplet is assigned an initial velocity and temperature and is set to impact a cold solid copper surface. The splat profile, as time progresses, is compared to the results in the literature. Among the computational modeling method changes investigated are the surface tension treatment, the solution method for the volume fraction equation, the volume fraction time sub-step calculation method, the volume fraction cut-off value and Courant number, the frequency of the volume fraction updates, the volume fraction discretization method, the mushy zone parameter, and mesh refinement. The study results can be used to provide information to aid in the generation of the models that can more accurately interrogate droplet-surface interactions.
Control Optimization Through Prediction-Based Wastewater Management
Authors: Tilcher David Konstantin , Popescu Florin , Sommer Harald , Thamsen Lauritz , Thamsen Paul Uwe 
Published: October 2021

Abstract
As part of a collaborative research project (OPTIMA) by Fraunhofer FOKUS, Engineering Company Prof. Dr. Sieker mbH, Department of Distributed and Operating Systems and Department of Fluid System Dynamics, TU Berlin, an „Intelligent Pumping Station” is being developed. In this research project, the operation of wastewater pumping stations is to be optimized by integrating precipitation forecasts and recording operating conditions on one hand, and by integrating historical data on use and operation on the other. The individual strategies for optimizing the operation of pumping stations and the possibilities of data integration will be systematically investigated.
The focus of this paper is on the method for developing an optimized pump control. It examines how knowledge of predicted inflow can be used to achieve energy savings and a reduction in wastewater overflows. This method is based on the development of an algorithm in which detailed consideration of pump specifics and future pumping station inflow can be used to predict all possible suction head level curves for the considered period of time. Depending on the target criterion — minimum energy consumption per transported cubic meter or minimum overflow volume — the algorithm calculates the optimum path from all possible suction chamber level curves.
A Three-Dimensional Phase Field Based Nonorthogonal Multiple-Relaxation-Time Lattice Boltzmann Method for Interface Tracking
Authors: Zhang Shengyuan , Tang Jun , Wu Huiying 
Published: October 2021

Abstract
Based on a conservative Allen-Cahn phase field method, a three-dimensional nonorthogonal multiple-relaxation-time (MRT) lattice Boltzmann (LB) model for interface tracking in multiphase flow is proposed in this paper. Different from the traditional MRT LB model, the transformation matrix in the present model is constructed based on a set of nonorthogonal basis vectors to simplify the transformation process between the discrete velocity space and the moment space. Therefore, a higher computational efficiency is achieved by the present model. The present model is developed on two different three-dimensional lattice sets (D3Q19 and D3Q27) to obtain a thorough perspective about the performance of the nonorthogonal matrix. Coupled with the nonorthogonal transformation matrix, simplified discrete source terms are also developed for both two lattice sets to further improve the efficiency of the present model. Numerical tests demonstrate that compared with the traditional MRT LB model, the present model shows a significantly higher computational efficiency and better stability while maintaining a comparable accuracy. It is also found that the D3Q19 nonorthogonal model does not obviously weaken the accuracy of D3Q27 nonorthogonal model while D3Q27 nonorthogonal model dose not decrease the stability of the D3Q19 nonorthogonal model, which is different from the orthogonal model.
The Four Stage Development of Starting Turbulent Buoyant Plumes
Authors: Tran Thanh , Bhaganagar Kiran 
Published: October 2021

Abstract
Turbulent heated and buoyant plumes have important applications in the atmosphere such as wildland fire plumes, volcanic plumes, and chemical plumes. The purpose of the study is to analyze the turbulence structures, and to understand the stages of the development of the starting turbulent plumes. For this purpose, data generated from an in-house Weather Research Forecast model coupled with Large-eddy simulation (WRF-bLES) with two-way feedback between the buoyant plume and the atmosphere developed has been used. The release of both dense gases (Co2, So2) and, buoyant gases (He, NH3, heated air) from a circular source at the bottom of the domain have been investigated. The simulations of the axisymmetric plume were performed at a high Reynolds number of 108. Vortex Identification methods were used to extract the Coherent structures and the large-scale features of the flow. The results have demonstrated that both the dense and the buoyant heated plumes with different initial characters exhibited universal characteristics and the development of the starting plumes occurred in four characteristic stages: Stage 1 is the plume acceleration stage, followed by stage 2 which corresponds to the formation of the head of the plume which grows spatially. Stage 3 is when the plume head is fully formed and the flow transitions to quasi-steady-state behavior. The final stage is the fully developed plume.
The identification of the four-stage development of the plume in the neutral environment is the first step in studying the turbulent heated and buoyant plumes development in order to characterize realistic plumes and to quantify the extent of mixing at each of these stages. This work has important contributions to fundamental fluid dynamics of buoyant plumes with implications on forecasting the plume trajectory of smoke, wildland fire, and volcanic plumes.