Volume of Fluid Simulations of Copper Droplet Splat and Sensitivity to Modeling Methods

2021 ◽  
Author(s):  
Laurie A. Florio
Keyword(s):  
Computational Modeling ◽  
Volume Fraction ◽  
Liquid Droplet ◽  
Copper Substrate ◽  
Volume Of Fluid ◽  
Modeling Method ◽  
Courant Number ◽  
Geometric Conditions ◽  
Study Results ◽  
Wide Range

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.

The Influence of Barrier and Applied Voltage Parameters on the Impulse Surface Discharge Characteristics

2020 ◽  
Vol 11 (11) ◽  
pp. 17-27
Author(s):  
Vadim V. VOEVODIN ◽  
◽  
Marina V. SOKOLOVA ◽  
Viktor R. SOLOV’YEV ◽  
Nikolay Yu. LYSOV ◽  
...  
Keyword(s):  
Applied Voltage ◽  
Voltage Pulse ◽  
Discharge Zone ◽  
Surface Discharge ◽  
Initial Surface ◽  
Barrier Material ◽  
Dielectric Barrier ◽  
Discharge Ignition ◽  
Study Results ◽  
Wide Range

The results from an experimental study of impulse surface discharge occurring in an electrode system containing a dielectric plate are presented. On one of its sides, the plate had a corona-producing electrode made of 50 mm thick copper foil grounded through a current shunt for measuring the discharge current. On its other side, the plate had a high-voltage electrode, to which the voltage from a pulse generator was applied. The article presents the results from measurements of the initial voltage and the sizes of the surface discharge area in air when applying single voltage pulses with different pulse front steepness in the range 0,1–3,4 kV/ms and amplitude in the range 7–15 kV. The measurements were carried out for different dielectric barrier materials with the e values from 2 to 35. The dielectric barrier thickness was 0,9–1,8 mm. The study results have shown that the initial surface discharge ignition voltage depends essentially on the voltage pulse parameters, whereas the barrier characteristics have a weaker effect on this voltage. It has been determined that the discharge has different discharge zone length and different structure depending on the dielectric barrier properties and applied voltage parameters. The streamer zone sizes decrease with increasing the barrier material e value at the same voltage pulse steepness and increase with increasing the steepness for each barrier material. The data obtained for a wide range of external conditions can be used in numerical modeling of discharge.

CRIMINOLOGICAL FEATURES OF CORRUPTION-RELATED CRIMES IN THE FUEL AND ENERGY COMPLEX

2020 ◽  
pp. 23-27
Author(s):  
Сергей Иванович Вележев ◽  
Антон Михайлович Седогин
Keyword(s):  
Legal Protection ◽  
Criminal Activity ◽  
Criminal Cases ◽  
Law Enforcement Agencies ◽  
Energy Complex ◽  
Significant Damage ◽  
Study Results ◽  
Wide Range ◽  
Illegal Activities ◽  
High Level

В представленной статье авторами рассматриваются вопросы уголовно-правовой охраны топливно-энергетического комплекса Российской Федерации от преступных проявлений, в том числе от коррупционной противоправной деятельности должностных лиц. Такие действия причиняют значительный ущерб нормальному функционированию предприятий топливно-энергетического комплекса. Авторами приводятся результаты исследования некоторых криминологических характеристик должностных лиц, совершивших преступления коррупционного характера. Дан анализ причин и условий, способствующих совершению вышеуказанных противоправных действий. Определена типовая модель преступника для данной категории преступлений и его характеристики: в первую очередь, это высокий уровень компетентности, специальное образование и т. д. Авторами отмечается высокий уровень латентной преступности в данной отрасли. Предложены некоторые пути профилактики данной категории правонарушений. Исследование проводилось на основе анализа конкретных уголовных дел, возбужденных следственными органами по результатам оперативно-розыскной деятельности правоохранительных органов. In the article the authors consider the issues of criminal and legal protection of the fuel and energy complex of the Russian Federation from criminal activity including corrupt illegal practices of officials. The authors cite the results of some criminological characteristics study of the fuel and energy complex staff committed corruption crimes. As a result of these illegal actions significant damage is caused to the normal functioning of the fuel and energy enterprises. Such officials` actions determine not only a wide range of other illegal activities, but also lead to public outcry and discredit the industry as a whole. The analysis of the reasons and conditions contributing to the above illegal actions commission is given. A typical model of a criminal for a given crime category and its characteristics are determined. First of all it is a high level competence, special education, etc. A high level of latent crime in this industry is shown. The study results are presented on the example of specific criminal cases initiated by the investigating authorities based on the results of the operation detection activities of law enforcement agencies. Some ways of preventing this category of offenses are proposed.

scholarly journals Environmental Flow Assessment Considering Inter- and Intra-Annual Streamflow Variability under the Context of Non-Stationarity

Water ◽  
2018 ◽  
Vol 10 (12) ◽  
pp. 1737 ◽  
Author(s):  
Kang Ren ◽  
Shengzhi Huang ◽  
Qiang Huang ◽  
Hao Wang ◽  
Guoyong Leng
Keyword(s):  
Kendall Test ◽  
Environmental Flow ◽  
Mean Value ◽  
Test Method ◽  
Stationary Condition ◽  
Annual Streamflow ◽  
Riverine Ecosystems ◽  
Study Results ◽  
Wide Range ◽  
Streamflow Variability

A key challenge to environmental flow assessment in many rivers is to evaluate how much of the discharge flow should be retained in the river in order to maintain the integrity and valued features of riverine ecosystems. With the increasing impact of climate change and human activities on riverine ecosystems, the natural flow regime paradigm in many rivers has become non-stationary conditions, which is a new challenge to the assessment of environmental flow. This study presents a useful framework to (1) detect change points in runoff time series using two statistical methods (Mann-Kendall test method and heuristic segmentation method), (2) adjust data of the changed period against the original flow series into a stationary condition using a procedure of reconstruction; and (3) incorporate inter- and intra-annual streamflow variability with adjusted streamflow to evaluate environmental flow. The Jialing to Han inter-basin water transfer project was selected as the case study. Results indicate that a change point of 1994 was identified, revealing that the stationarity of annual streamflow series is invalid. The variations of reconstructed streamflow series are roughly consistent with original streamflow series, especially in the maximum/minimum values and rise/fall rates, but the mean value of reconstructed streamflow series is increased. The reconstructed streamflow series would further serve to eliminate the non-stationary of original streamflow, and incorporating the inter- and intra-annual variability would upgrade the ecosystem fitness. Selecting different criteria for the conservation of riverine ecosystems can have significantly different consequences, and we should not focus on the protection of specific objectives that will inevitably affect other aspects. This study provides a useful framework for environmental flow assessment and can be applied to a wide range of instream flow management approaches to protect the riverine ecosystem.

scholarly journals Two-Dimensional Numerical Modeling of Flow in Physical Models of Rock Vane and Bendway Weir Configurations

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 458
Author(s):  
Drew C. Baird ◽  
Benjamin Abban ◽  
S. Michael Scurlock ◽  
Steven B. Abt ◽  
Christopher I. Thornton
Keyword(s):  
Numerical Modeling ◽  
Physical Model ◽  
Numerical Models ◽  
Hydraulic Performance ◽  
Physical Models ◽  
Protection Measures ◽  
Design Engineers ◽  
Model Study ◽  
Study Results ◽  
Wide Range

While there are a wide range of design recommendations for using rock vanes and bendway weirs as streambank protection measures, no comprehensive, standard approach is currently available for design engineers to evaluate their hydraulic performance before construction. This study investigates using 2D numerical modeling as an option for predicting the hydraulic performance of rock vane and bendway weir structure designs for streambank protection. We used the Sedimentation and River Hydraulics (SRH)-2D depth-averaged numerical model to simulate flows around rock vane and bendway weir installations that were previously examined as part of a physical model study and that had water surface elevation and velocity observations. Overall, SRH-2D predicted the same general flow patterns as the physical model, but over- and underpredicted the flow velocity in some areas. These over- and underpredictions could be primarily attributed to the assumption of negligible vertical velocities. Nonetheless, the point differences between the predicted and observed velocities generally ranged from 15 to 25%, with some exceptions. The results showed that 2D numerical models could provide adequate insight into the hydraulic performance of rock vanes and bendway weirs. Accordingly, design guidance and implications of the study results are presented for design engineers.

scholarly journals Adherence to Ketogenic and Mediterranean Study Diets in a Crossover Trial: The Keto–Med Randomized Trial

Nutrients ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 967
Author(s):  
Matthew J. Landry ◽  
Anthony Crimarco ◽  
Dalia Perelman ◽  
Lindsay R. Durand ◽  
Christina Petlura ◽  
...  
Keyword(s):  
Randomized Trial ◽  
Randomized Clinical Trials ◽  
Secondary Analysis ◽  
Critical Factor ◽  
Detailed Examination ◽  
Diet Patterns ◽  
Time Points ◽  
Study Results ◽  
Wide Range ◽  
Diet Pattern

Adherence is a critical factor to consider when interpreting study results from randomized clinical trials (RCTs) comparing one diet to another, but it is frequently not reported by researchers. The purpose of this secondary analysis of the Keto–Med randomized trial was to provide a detailed examination and comparison of the adherence to the two study diets (Well Formulated Ketogenic Diet (WFKD) and Mediterranean Plus (Med-Plus)) under the two conditions: all food being provided (delivered) and all food being obtained by individual participants (self-provided). Diet was assessed at six time points including baseline (x1), week 4 of each phase when participants were receiving food deliveries (x2), week 12 of each phase when participants were preparing and providing food on their own (x2), and 12 weeks after participants completed both diet phases and were free to choose their own diet pattern (x1). The adherence scores for WFKD and Med-Plus were developed specifically for this study. Average adherence to the two diet patterns was very similar during both on-study time points of the intervention. Throughout the study, a wide range of adherence was observed among participants—for both diet types and during both the delivery phase and self-provided phase. Insight from this assessment of adherence may aid other researchers when answering the important question of how to improve behavioral adherence during dietary trials. This study is registered at clinicaltrials.gov NCT03810378.

scholarly journals Numerical Study on an Interface Compression Method for the Volume of Fluid Approach

Fluids ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 80
Author(s):  
Yuria Okagaki ◽  
Taisuke Yonomoto ◽  
Masahiro Ishigaki ◽  
Yoshiyasu Hirose
Keyword(s):  
Linear Theory ◽  
Volume Fraction ◽  
Numerical Study ◽  
Volume Of Fluid ◽  
Interfacial Wave ◽  
Validation Process ◽  
Two Phase ◽  
Numerical Diffusion ◽  
Mesh Resolution ◽  
Water Reactors

Many thermohydraulic issues about the safety of light water reactors are related to complicated two-phase flow phenomena. In these phenomena, computational fluid dynamics (CFD) analysis using the volume of fluid (VOF) method causes numerical diffusion generated by the first-order upwind scheme used in the convection term of the volume fraction equation. Thus, in this study, we focused on an interface compression (IC) method for such a VOF approach; this technique prevents numerical diffusion issues and maintains boundedness and conservation with negative diffusion. First, on a sufficiently high mesh resolution and without the IC method, the validation process was considered by comparing the amplitude growth of the interfacial wave between a two-dimensional gas sheet and a quiescent liquid using the linear theory. The disturbance growth rates were consistent with the linear theory, and the validation process was considered appropriate. Then, this validation process confirmed the effects of the IC method on numerical diffusion, and we derived the optimum value of the IC coefficient, which is the parameter that controls the numerical diffusion.

scholarly journals Factors Affecting Acoustic Properties of Natural-Fiber-Based Materials and Composites: A Review

Textiles ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 55-85
Author(s):  
Tufail Hassan ◽  
Hafsa Jamshaid ◽  
Rajesh Mishra ◽  
Muhammad Qamar Khan ◽  
Michal Petru ◽  
...  
Keyword(s):  
Sound Absorption ◽  
Natural Fiber ◽  
Volume Fraction ◽  
Fiber Type ◽  
Alkali Treatment ◽  
Acoustic Properties ◽  
Synthetic Fiber ◽  
Sound Insulation ◽  
Factors Affecting ◽  
Wide Range

Recently, very rapid growth has been observed in the innovations and use of natural-fiber-based materials and composites for acoustic applications due to their environmentally friendly nature, low cost, and good acoustic absorption capability. However, there are still challenges for researchers to improve the mechanical and acoustic properties of natural fiber composites. In contrast, synthetic fiber-based composites have good mechanical properties and can be used in a wide range of structural and automotive applications. This review aims to provide a short overview of the different factors that affect the acoustic properties of natural-fiber-based materials and composites. The various factors that influence acoustic performance are fiber type, fineness, length, orientation, density, volume fraction in the composite, thickness, level of compression, and design. The details of various factors affecting the acoustic behavior of the fiber-based composites are described. Natural-fiber-based composites exhibit relatively good sound absorption capability due to their porous structure. Surface modification by alkali treatment can enhance the sound absorption performance. These materials can be used in buildings and interiors for efficient sound insulation.

scholarly journals Robust Step Detection from Different Waist-Worn Sensor Positions: Implications for Clinical Studies

2020 ◽  
Vol 4 (1) ◽  
pp. 50-58
Author(s):  
Matthias  Tietsch ◽  
Amir Muaremi ◽  
Ieuan Clay ◽  
Felix Kluge ◽  
Holger Hoefling ◽  
...  
Keyword(s):  
Clinical Study ◽  
Clinical Studies ◽  
Neurological Diseases ◽  
Human Gait ◽  
Robust Solution ◽  
Step Detection ◽  
Study Protocols ◽  
Study Results ◽  
Wide Range ◽  
The Impact

Analyzing human gait with inertial sensors provides valuable insights into a wide range of health impairments, including many musculoskeletal and neurological diseases. A representative and reliable assessment of gait requires continuous monitoring over long periods and ideally takes place in the subjects’ habitual environment (real-world). An inconsistent sensor wearing position can affect gait characterization and influence clinical study results, thus clinical study protocols are typically highly proscriptive, instructing all participants to wear the sensor in a uniform manner. This restrictive approach improves data quality but reduces overall adherence. In this work, we analyze the impact of altering the sensor wearing position around the waist on sensor signal and step detection. We demonstrate that an asymmetrically worn sensor leads to additional odd-harmonic frequency components in the frequency spectrum. We propose a robust solution for step detection based on autocorrelation to overcome sensor position variation (sensitivity = 0.99, precision = 0.99). The proposed solution reduces the impact of inconsistent sensor positioning on gait characterization in clinical studies, thus providing more flexibility to protocol implementation and more freedom to participants to wear the sensor in the position most comfortable to them. This work is a first step towards truly position-agnostic gait assessment in clinical settings.

scholarly journals Computational Modeling and Constructal Design Theory Applied to the Geometric Optimization of Thin Steel Plates with Stiffeners Subjected to Uniform Transverse Load

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 220 ◽  
Author(s):  
Grégori Troina ◽  
Marcelo Cunha ◽  
Vinícius Pinto ◽  
Luiz Rocha ◽  
Elizaldo dos Santos ◽  
...  
Keyword(s):  
Computational Modeling ◽  
Design Theory ◽  
Degrees Of Freedom ◽  
Volume Fraction ◽  
Geometric Optimization ◽  
Steel Plates ◽  
Transverse Load ◽  
Constructal Design ◽  
Thin Steel ◽  
Reference Plate

Stiffened thin steel plates are structures widely employed in aeronautical, civil, naval, and offshore engineering. Considering a practical application where a transverse uniform load acts on a simply supported stiffened steel plate, an approach associating computational modeling, Constructal Design method, and Exhaustive Search technique was employed aiming to minimize the central deflections of these plates. To do so, a non-stiffened plate was adopted as reference from which all studied stiffened plate’s geometries were originated by the transformation of a certain amount of steel of its thickness into longitudinal and transverse stiffeners. Different values for the stiffeners volume fraction (φ) were analyzed, representing the ratio between the volume of the stiffeners’ material and the total volume of the reference plate. Besides, the number of longitudinal (Nls) and transverse (Nts) stiffeners and the aspect ratio of stiffeners shape (hs/ts, being hs and ts, respectively, the height and thickness of stiffeners) were considered as degrees of freedom. The optimized plates were determined for all studied φ values and showed a deflection reduction of over 90% in comparison with the reference plate. Lastly, the influence of the φ parameter regarding the optimized plates was evaluated defining a configuration with the best structural performance among all analyzed cases.

scholarly journals Conduction and convection heat transfer characteristics of water-based au nanofluids in a square cavity with differentially heated side walls subjected to constant temperatures

2014 ◽  
Vol 18 (suppl.1) ◽  
pp. 189-200 ◽  
Author(s):  
Primoz Ternik ◽  
Rebeka Rudolf
Keyword(s):  
Heat Transfer ◽  
Rayleigh Number ◽  
Base Fluid ◽  
Volume Fraction ◽  
Heat Transfer Characteristics ◽  
Square Cavity ◽  
Onset Of Convection ◽  
Transfer Characteristics ◽  
Wide Range ◽  
Water Based

The present work deals with the natural convection in a square cavity filled with the water-based Au nanofluid. The cavity is heated on the vertical and cooled from the adjacent wall, while the other two horizontal walls are adiabatic. The governing differential equations have been solved by the standard finite volume method and the hydrodynamic and thermal fields were coupled together using the Boussinesq approximation. The main objective of this study is to investigate the influence of the nanoparticles? volume fraction on the heat transfer characteristics of Au nanofluids at the given base fluid?s (i.e. water) Rayleigh number. Accurate results are presented over a wide range of the base fluid Rayleigh number and the volume fraction of Au nanoparticles. It is shown that adding nanoparticles in a base fluid delays the onset of convection. Contrary to what is argued by many authors, we show by numerical simulations that the use of nanofluids can reduce the heat transfer rate instead of increasing it.

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