bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comprehensive Analysis of Fluid-Structure Interactive Schemes for Modeling Aircraft Water Impact Scenarios
Authors: Megharaja Suraj Jain , Bayandor Javid 
Published: October 2020

Abstract
Aircraft emergency water landings (ditching) are uncommon but remain an ever-present possibility. Therefore, crashworthiness standards as part of the Federal Aviation Regulations demand such situations to be accounted for during the certification phase. The criteria require aircraft to prove its ability to survive ditching and be able to float after impact for a duration long enough for the passengers to be rescued. In emergency scenarios, it is preferred to choose an open body of water as the landing location as opposed to hard terrain. It would be prohibitively expensive to test impacts of this nature to cover all required certification cases. The data collection can also be a tedious process. Due to these hindrances, performing numerical validation of aircraft water ditching (fluid-solid) interactions has become more important than ever. In case of hard terrain impact, most of the energy is absorbed by the frame of an aircraft. However, in water impacts, the initial load is distributed over the skin. As a result, the ability of an aircraft to withstand crash becomes dependent on the strength of the shear panels to allow an effective transfer of impact energy to damage-absorbing members and mechanisms before failling. Large full-scale simulations to capture the structural response of an aircraft under severe impact loading however can be computationally intensive. This work focusses on comparative analysis of numerical strategies for assessing fluid-structural Interactions. Two of the methods considered are Lagrangian, and Arbitrary Lagrangian and Eulerian (ALE) schemes.
For preliminary validations, the experimental studies performed by other research groups have been used to investigate the effect of mesh refinement and computational time on the Lagrangian and ALE schemes. These simulations will provide a basis for selecting the right formulations when developing fluid-solid interactive models for aerospace applications. Based on the results of the studies conducted, the most computationally efficient scheme was then used to perform the simulations of an aircraft fuselage section when impacting water in an emergency landing situation. The fuselage model used in this project was pre-validated against a rigid terrain experimental drop test before it was applied to the ditching studies. Overall, this investigation aims at assessing advanced modeling techniques and approaches that can pave the way for analysis-assited water impact certification and, ultimately, certification by analysis.
Thermal-Fluid Analysis and Optimization of Micro-Scale Heat Sinks With Slip Boundary Condition Using Entropy Generation Minimization Method
Authors: Pourghasemi Mahyar , Fathi Nima , Anderson Kevin R. 
Published: October 2020

Abstract
Performance of a micro-scale heat sink with slip boundary condition at walls is evaluated using entropy generation minimization (EGM) approach. Optimum geometrical parameters and working conditions are obtained by applying two different constraints of fixed microchannel height and constant maximum pressure drop. It has been observed that with fixed channel height constraint, the optimum aspect ratio and Reynolds number are 2.5 and 700, respectively. Slip boundary condition has negligible effect on optimum working parameters while it enhances the thermal performance of the heat sink by almost 4% at fixed height constraint. At maximum pressure drop constraint, the optimum working parameters are aspect ratio of 2.25 and Reynolds number of 850. Slip on the microchannel walls reduces pressure drop and enhances the thermal performance of the heat sink by 11%.
Performance Evaluation of a New Configuration of Direct Contact Humidification Dehumidification (DCHDH) Desalination System
Authors: Aguiar Fernando G. , Kandlikar Satish G. 
Published: October 2020

Abstract
In the present study, the performance of a humidification-dehumidification (HDH) desalination system with the humidifier and the dehumidifier contained in the same enclosure is evaluated. In this design the humidifier system is composed of a vertical copper tube coated with a hydrophilic air-laid paper layer in which saline water is dripped and hot water (from 42.3 to 79.4 °C) flows inside to heat the humidifier system while the dehumidifier consists of an aluminum plate with internal channels for cold water (16 °C) flow. The experimental results show a pure water production rate per unit system volume up to 19.13 L/m3h at a water temperature of 79.4 °C at the evaporator inlet and a hot water mass flow rate of 135 mL/min. This new design has potential for application in desalination systems, especially sin mall systems for use by families living in arid regions.
Active High-Throughput Micromixer Using Injected Magnetic Mixture Underneath Microfluidic Channel
Authors: Surendran Athira N. , Zhou Ran 
Published: October 2020

Abstract
Microfluidics has a lot of applications in fields ranging from pharmaceutical to energy, and one of the major applications is micromixers. A challenge faced by most micromixers is the difficulty in mixing within micro-size fluidic channels because of the domination of laminar flow in a small channel. Hence, magnetic field generated by permanent magnets and electromagnets have been widely used to mix ferrofluids with other sample fluids on a micro level. However, permanent magnets are bulky, and electromagnets produce harmful heat to biological samples; both properties are detrimental to a microfluidic chip’s performance. Taking these into consideration, this study proposes rapid mixing of ferrofluid using a two-layer microfluidic device with microfabricated magnet. Two microfluidic chips that consist of microchannels and micromagnets respectively are fabricated using a simple and low-cost soft lithography method. The custom-designed microscale magnet consists of an array of stripes and is bonded below the plane of the microchannel. The combination of the planar location and angle of the array of magnets allow the migration of ferrofluids, hence mixing it with buffer flow. Parametric studies are performed to ensure comprehensive understanding, including the angle of micro-scale magnets with respect to the fluidic channels, total flow rate and density of the array of magnets. The result from this study can be applied in chemical synthesis and pre-processing, sample dilution, or inducing reactions between samples and reagent.
High Speed Imaging of Bubble Interface Motion in a Tapered Microgap
Authors: Chauhan Aranya , Kandlikar Satish G. 
Published: October 2020

Abstract
The current industrial trend requires development of efficient heat dissipation systems. A tapered microgap on the heater surface provides an efficient pool boiling heat transfer technique in dissipating large heat fluxes. This study is focused on capturing the high-speed images of bubble nucleation, growth and expansion processes. The interface velocities are estimated by tracking the interface of the growing bubble. The insight into interface motion will help in estimating the magnitude of the expanding force and predicting the pressure recovery effect during two-phase flow in the gap. The expansion force helps in establishing high flow rates resulting in high heat transfer coefficient (HTC) and critical heat flux (CHF) values. The effect of design parameters such as taper angle and height of the microgap on the bubble growth patterns are evaluated. The results show that the bubbles are nucleated and are then confined in the narrow gap. The tapered configuration propels the leading bubble interface in the flow direction and eventually the entire bubble in that direction. The bubble motion causes liquid to enter from the narrow region of the microgap. This effect, combined with the pressure recovery resulting from the two-phase flow in the expanding section of the microgap provides a bubble pumping mechanism. This configuration results in improving both the critical heat flux and heat transfer coefficient during pool boiling.
Fundamental Insight on Morphological Changes of Graphene Nanoplatelets-Copper (GNP-Cu) Coatings: Effects of Repetitive Pool Boiling Tests
Authors: Rishi Aniket M. , Gupta Anju 
Published: October 2020

Abstract
Being an extremely vigorous process involving a continuous intense bubble activity, repetitive pool boiling study is essential for many industrial applications. In this work, we have utilized highly thermally conductive and highly wettable graphene nanoplatelets (GNP) to form GNP-Copper based composite coatings for enhancing the pool boiling heat transfer performance. A multi-step electrodeposition technique was implemented to develop robust coatings on the copper substrates. Repetitive pool boiling studies were conducted on the 2% GNP-Cu coating which achieved the highest CHF of 286 W/cm2 and HTC of 204 kW/m2-°C. After investigating the effect of repetitive boiling on deposited GNP layers and morphology, it was found that GNP were reduced to form r-GNP (reduced GNP) and small increment in pore sizes was observed. Additionally, with repetitive boiling, it was observed that the heat transfer coefficient was continuously increased and compared to pristine copper surface 2% GNP-Cu coating yielded ∼456% increment in HTC at the end of third repetitive test.
A Proposed Approach for Accurate Estimation of Interface Surface Area in Multiphase Simulations
Authors: Shipkowski Simon Peter , Perez-Raya Isaac , Kandlikar Satish G. 
Published: October 2020

Abstract
Multiphase simulations and computational methods with precisely quantified interfaces are important for variety of engineering applications. A few of these applications are: heat transfer utilizing boiling processes, optimizing combustion, and additive printing/deposition processes. In these applications, calculating the length of the interface between two phases (e.g. a vapor and liquid) is particularly critical. Errors in the calculation of the size of the interface propagate over subsequent time steps thereby producing inaccurate rates of phase-change, fluid velocities, and convection heat transfer. This work proposes a method to reduce the reduce error in interface calculations in multiphase simulations. The proposed method uses the interface inclination and the vapor volume-fraction on each computational cell to compute the interface surface area. Moreover, this work provides details on proper declaration and computation of mass transfer with the Volume-of-Fluid sharp interface tracking algorithm. The performance of the proposed approach is compared with the accepted method that estimates interface surface area with gradients of vapor volume fractions. Computer simulations of spherical bubble growth in superheated liquid demonstrate the relevance of the proposed approach. Results indicate that the errors with the accepted method could propagate to 20% (relative to the theoretical estimation) in the prediction of bubble growth rate and fluid velocities. The proposed approach leads to errors of less than 1% in the prediction of bubble growth rate and fluid velocities.
Simulation of Subcooled Flow Boiling in Manifold Microchannel Heat Sink
Authors: Luo Yang , Zhang Jingzhi , Li Wei 
Published: October 2020

Abstract
The manifold microchannel (MMC) heat sink has become the most popular one among emerging technologies for high heat flux thermal management because of its high surface-to-volume ratio. Even though numerous numerical studies have been performed for the single-phase flow in the MMC heat sink, researches on two-phase flow boiling/condensation in this type of microchannel is seldomly reported because of its issues with flow pattern prediction. In the present work, a numerical approach involving two-phase interface capturing, phase change and solid heat conduction is conducted for the simplified MMC unit cell model. Heat and mass transfers of Lee model and interfacial heat resistance model for phase change are validated by the single bubble growth problem. Besides, both phase-change models are shown to provide good predictions against the experimental temperature database, with all of the data points falling within −5% to +20% and −5% to +10% error bands for Lee model and interfacial resistance model, respectively. Furthermore, a liquid-vapor interface region with thin thickness and accurate interface temperature can be obtained by the interfacial resistance model coupled with homogeneous nucleation-site model.
3D Investigation of Droplet Generation in a Miniaturized Coflowing Device Using Micro-Computed Tomography
Authors: Schuler Julia , Neuendorf Laura Maria , Petersen Kai , Kockmann Norbert 
Published: October 2020

Abstract
For many applications, such as liquid-liquid or gas-liquid reactions, the generation of monodisperse droplets is of major interest. Therefore, knowledge about the physics of droplet formation is essential and the subject of numerous studies. Droplet formation is usually investigated using optical cameras, which makes optical accessibility necessary. Furthermore, properties defining droplet evolution is obtained from 2D images. In this work, we present a methodology for the 3D investigation of droplet formation in the laminar regime using micro-computed tomography. A special imaging concept and image processing, incorporating the use of a convolutional neural network, is presented. Water droplets are injected into a continuous polydimethylsiloxane stream in a coflowing configuration using a cannula with an inner diameter di = 800 μm and an outer diameter do = 1050 μm that is centered in a thin polymer tube with an inner diameter di = 1600 μm. Volume flow rates of polydimethylsiloxane and water are varied between 0.2 and 0.3 mL min−1. Furthermore, the influence of cannula positioning on droplet formation is investigated. Different quantitative 3D properties are extracted from the CT scans, such as droplet volume and surface of the interface. Thereby, different stages of droplet formation can be identified and the physical understanding of droplet formation is improved.
Fully-Developed Convective Heat Transfer and Pressure Drop in a Square Duct With Baffle Inserts Using CFD Analysis
Authors: Christensen Lasse U. , Holebæk Stefan , Thanabalasingham Nisanthan , Hærvig Jakob , Sørensen Henrik 
Published: October 2020

Abstract
The scope of this project is to investigate how the geometry of baffles affect heat transfer and pressure loss of a fluid flow at Re = 1000 through a square duct. For this purpose, Large Eddy Simulations are performed to investigate the effect of baffle height and baffle width. Focus is on the fully-developed flow that repeats itself at streamwise stations. The flow field predicted by Computational Fluid Dynamics simulations was validated using Particle Image Velocimetry.
The different designs are evaluated in terms of Nusselt number, Nu and a loss coefficient, f, which are normalised using a reference geometry consisting of a square duct without baffles. The two parameters are additionally combined into a performance parameter eta η = (Nu/Nu0)/(f / f0)(1/3).
It was found that adding baffles can result in a quadrupling of η. Reducing the height of baffles decreases heat transfer, while significantly reducing pressure loss and ultimately leading to a higher η. Reducing baffle height was also found to increase the temperature gradient at the upper wall and reduce it at the lower wall. Reducing baffle width resulted in the largest temperature gradient, but lead to poor heat transfer within the fluid.
Contact Line Pinning and Depinning Prior to Rupture of an Evaporating Droplet in a Simulated Soil Pore
Authors: Chakraborty Partha P. , Derby Melanie M. 
Published: October 2020

Abstract
Altering soil wettability by inclusion of hydrophobicity could be an effective way to restrict evaporation from soil, thereby conserving water resources. In this study, 4-μL sessile water droplets were evaporated from an artificial soil millipore comprised of three glass (i.e. hydrophilic) and Teflon (i.e. hydrophobic) 2.38-mm-diameter beads. The distance between the beads were kept constant (i.e. center-to-center spacing of 3.1 mm). Experiments were conducted in an environmental chamber at an air temperature of 20°C and 30% and 75% relative humidity (RH). Evaporation rates were faster (i.e. ∼19 minutes and ∼49 minutes at 30% and 75% RH) from hydrophilic pores than the Teflon one (i.e. ∼24 minutes and ∼52 minutes at 30% and 75% RH) due in part to greater air-water contact area. Rupture of liquid droplets during evaporation was analyzed and predictions were made on rupture based on contact line pinning and depinning, projected surface area just before rupture, and pressure difference across liquid-vapor interface. It was observed that, in hydrophilic pore, the liquid droplet was pinned on one bead and the contact line on the other beads continuously decreased by deforming the liquid-vapor interface, though all three gas-liquid-solid contact lines decreased at a marginal rate in hydrophobic pore. For hydrophilic and hydrophobic pores, approximately 1.7 mm2 and 1.8–2 mm2 projected area of the droplet was predicted at 30% and 75% RH just before rupture occurs. Associated pressure difference responsible for rupture was estimated based on the deformation of curvature of liquid-vapor interface.
Impact of low and no alcohol beers on purchases of alcohol: interrupted time series analysis of British household shopping data, 2015–2018
Authors: Anderson Peter , Jané Llopis Eva , O’Donnell Amy , Manthey Jakob , Rehm Jürgen 
Published: October 2020

ObjectiveTo assess the impact of new low and no alcohol beers and reformulated beers in Great Britain on household purchases of grams of alcohol.DesignInterrupted time series analysis.SettingPurchase data from Kantar Worldpanel’s household shopping panel for 2015–2018.Participants64 286 British households.InterventionsIntroduction of new no and low alcohol beers during 2017–2018 and reformulation of existing beers to contain less alcohol during 2018.Main outcome measuresAverage alcoholic strength of beer and number of grams of alcohol purchased by households.ResultsAs assessed by British household purchase data, 46 new low and no alcohol beer products were introduced during 2015–2018, with a step-jump in volume purchased occurring at the beginning of March 2017 (event 1). During 2015–2018, 33 beer products were reformulated to contain less alcohol, with a step-jump in volume purchased occurring during mid-March 2018 (event 2). Interrupted time series analyses found a combined associated impact of both events with relative reductions of alcohol by volume of beer between 1.2% and 2.3%; purchases of grams of alcohol within beer between 7.1% and 10.2%; and purchases of grams of alcohol as a whole between 2.6% and 3.9%. The reductions were greater for reformulation than for the introduction of new low and no alcohol products. Reductions were independently higher for younger age groups of shoppers and for households that bought the most alcohol.ConclusionsEven though the events were associated with significant beneficial changes, the volume of purchases of new low and no alcohol beer products (2.6% of the volume of all beers purchased during 2018) and of new reformulated beer products (6.9% of the volume of all beers purchased during 2018) was very small. This indicates that there are future opportunities to increase the volume of such products so as to reduce the harm done by alcohol.
Dynamic prediction of overall survival: a retrospective analysis on 979 patients with Ewing sarcoma from the German registry
Authors: Liu Chuchu , Rueten-Budde Anja J , Ranft Andreas , Dirksen Uta , Gelderblom Hans , Fiocco Marta 
Published: October 2020

ObjectivesThis study aimed at developing a dynamic prediction model for patients with Ewing sarcoma (ES) to provide predictions at different follow-up times. During follow-up, disease-related information becomes available, which has an impact on a patient’s prognosis. Many prediction models include predictors available at baseline and do not consider the evolution of disease over time.SettingIn the analysis, 979 patients with ES from the Gesellschaft für Pädiatrische Onkologie und Hämatologie registry, who underwent surgery and treatment between 1999 and 2009, were included.DesignA dynamic prediction model was developed to predict updated 5-year survival probabilities from different prediction time points during follow-up. Time-dependent variables, such as local recurrence (LR) and distant metastasis (DM), as well as covariates measured at baseline, were included in the model. The time effects of covariates were investigated by using interaction terms between each variable and time.ResultsDeveloping LR, DM in the lungs (DMp) or extrapulmonary DM (DMo) has a strong effect on the probability of surviving an additional 5 years with HRs and 95% CIs equal to 20.881 (14.365 to 30.353), 6.759 (4.465 to 10.230) and 17.532 (13.210 to 23.268), respectively. The effects of primary tumour location, postoperative radiotherapy (PORT), histological response and disease extent at diagnosis on survival were found to change over time. The HR of PORT versus no PORT at the time of surgery is equal to 0.774 (0.594 to 1.008). One year after surgery, the HR is equal to 1.091 (0.851 to 1.397).ConclusionsThe time-varying effects of several baseline variables, as well as the strong impact of time-dependent variables, show the importance of including updated information collected during follow-up in the prediction model to provide accurate predictions of survival.