Effects of Pulsatility on the Laminar Mixing Surface in Converging Microchannel Flows

2002 ◽  
Author(s):  
D. L. Hitt ◽  
M. McGarry ◽  
R. D. Prabhu
Keyword(s):  
Nonlinear Behavior ◽  
Numerical Data ◽  
Interfacial Area ◽  
Interfacial Structure ◽  
Micro Scale ◽  
Flow Mixing ◽  
Laminar Mixing ◽  
Microchannel Flows ◽  
Mixing Techniques ◽  
The Impact

With the growing interest and development of microfluidic systems, the need for micro-scale laminar flow mixing techniques is evident. Traditional mixing methods often rely upon turbulent flow for mixing which is generally not present on the micro-scale and so alternative approaches must be sought. In this work, we report on the impact of flow pulsatility on the laminar mixing surface/interface formed between two converging microchannel flows. The motivation behind the study is to assess the potential for pulsatility as a possible MEMS-mixing strategy. A 3-D computational model of the converging flow at a 90° junction is developed using the Fluent6® CFD software and the volume-of-fluid algorithm is used to track time-dependent behavior of the interface downstream of the junction. Results thus far have shown that for certain parametric regimes a complex, evolving interfacial distortion can form which propagates and persists downstream of the junction. Time-series for the total interfacial area and the interfacial motion have been extracted from numerical data and spectral analyses have been performed; some interesting nonlinear behavior has been observed. Of particular importance, the results also show that the complexity of the interfacial structure is only significant at higher frequencies (order of kHz) which is appropriate for MEMS-based pumping devices.

scholarly journals Magnetization Reversal and Dynamics in Epitaxial Fe/Pt Spintronic Bilayers Stimulated by Interfacial Fe3O4 Nanoparticles

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4354
Author(s):  
Thomas Kehagias ◽  
Dimitrios Karfaridis ◽  
Camillo Ballani ◽  
Laura Mihalceanu ◽  
Christoph Hauser ◽  
...  
Keyword(s):  
Magnetization Reversal ◽  
Fe3o4 Nanoparticles ◽  
Spin Current ◽  
Interfacial Area ◽  
Electron Beam Evaporation ◽  
Interfacial Structure ◽  
Blocking Temperature ◽  
Strong Impact ◽  
Threading Dislocations ◽  
The Impact

We have explored the impact of elevated growth and annealing temperatures on the local interfacial structure of thin Fe(12 nm)/Pt(10 nm) spintronic bilayers, epitaxially grown on MgO (100), and their correlation to magnetization reversal and dynamics. Electron-beam evaporation growth and subsequent annealing at 450 °C causes significant roughening of the MgO/Fe interface with irregular steps and multilevel (100) MgO surface terraces. Consequently, threading dislocations emerging at the step edges propagated in the Fe layer and terminated at the Fe/Pt interface, which appears pitted with pits 1.5–3 nm deep on the Fe side. Most of the pits are filled with the overlying Pt, whereby others by ferrimagnetic Fe3O4, forming nanoparticles that occupy nearly 9% of the Fe/Pt interfacial area. Fe3O4 nanoparticles occur at the termination sites of threading dislocations at the Fe/Pt interface, and their population density is equivalent to the density of threading dislocations in the Fe layer. The morphology of the Fe/Fe3O4/Pt system has a strong impact on the magnetization reversal, enhancing the coercive field and inducing an exchange bias below 200 K. Furthermore, low-temperature spin pumping and inverse spin Hall effect voltage measurements reveal that below their blocking temperature the nanoparticles can influence the spin current transmission and the spin rectification effects.

scholarly journals The Impact of Microclimate on the Reproductive Phenology of Female Populus tomentosa in a Micro-Scale Urban Green Space in Beijing

2021 ◽  
Vol 13 (6) ◽  
pp. 3518
Author(s):  
Xiaoyi Xing ◽  
Li Dong ◽  
Cecil Konijnendijk ◽  
Peiyao Hao ◽  
Shuxin Fan ◽  
...  
Keyword(s):  
Seed Dispersal ◽  
Spatial Variation ◽  
Air Temperature ◽  
Green Space ◽  
Populus Tomentosa ◽  
Early Spring ◽  
Reproductive Phenology ◽  
Primary Role ◽  
Micro Scale ◽  
The Impact

The spatial variation of poplars’ reproductive phenology in Beijing’s urban area has aggravated the threat of poplar fluff (cotton-like flying seeds) to public health. This research explored the impact of microclimate conditions on the reproductive phenology of female Populus tomentosa in Taoranting Park, a micro-scale green space in Beijing (range <1 km). The observed phenophases covered flowering, fruiting, and seed dispersal, and ENVI-MET was applied to simulate the effect of the microclimate on SGS (start day of the growing season). The results showed that a significant spatial variation in poplar reproductive phenology existed at the research site. The variation was significantly affected by the microclimate factors DMT (daily mean temperature) and DMH (daily mean heat transfer coefficient), with air temperature playing a primary role. Specifically, the phenology of flowering and fruiting phenophases (BBB, BF, FF, FS) was negatively correlated with DMT (−0.983 ≤ r ≤ −0.908, p <0.01) and positively correlated with DMH (0.769 ≤ r ≤ 0.864, p < 0.05). In contrast, DSD (duration of seed dispersal) showed a positive correlation with DMT (r = 0.946, p < 0.01) and a negative correlation with DMH (r = −0.922, p < 0.01). Based on the findings, the increase in air convection with lower air temperature and decrease in microclimate variation in green space can be an effective way to shorten the seed-flying duration to tackle poplar fluff pollution in Beijing’s early spring.

scholarly journals Advances and Challenging Issues in Subsurface Drainage Module Technology and BIOECODS: A Review

2018 ◽  
Vol 203 ◽  
pp. 07005 ◽  
Author(s):  
Abdurrasheed Sa'id Abdurrasheed ◽  
Khamaruzaman Wan Yusof ◽  
Husna Bt Takaijudin ◽  
Aminuddin Ab. Ghani ◽  
Muhammad Mujahid Muhammad ◽  
...  
Keyword(s):  
Drainage System ◽  
Numerical Data ◽  
Subsurface Drainage ◽  
Infiltration Capacity ◽  
Sustainable Solutions ◽  
Ecologically Sustainable ◽  
The Impact ◽  
Flow Attenuation ◽  
Permeability Rate ◽  
Over Time

Subsurface drainage modules are important components of the Bio-ecological Drainage System (BIOECODS) which is a system designed to manage stormwater quantity and quality using constructed grass swales, subsurface modules, dry and wet ponds. BIOECODS is gradually gaining attention as one of the most ecologically sustainable solutions to the frequent flash floods in Malaysia and the rest of the world with a focus on the impact of the subsurface modules to the effectiveness of the system. Nearly two decades of post-construction research in the BIOECODS technology, there is need to review findings and areas of improvement in the system. Thus, this study highlighted the key advances and challenges in these subsurface drainage modules through an extensive review of related literature. From the study, more work is required on the hydraulic characteristics, flow attenuation and direct validation methods between field, laboratory, and numerical data. Also, there is concern over the loss of efficiency during the design life especially the infiltration capacity of the module, the state of the geotextile and hydronet over time. It is recommended for the sake of higher performance, that there should be an onsite methodology to assess the permeability, rate of clogging and condition of the geotextile as well as the hydronet over time.

Micro-Scale Flow Simulations and Permeability Estimation of Cleat Networks in Coal

2016 ◽  
Vol 846 ◽  
pp. 42-47
Author(s):  
J. Busse ◽  
S. Galindo Torres ◽  
Alexander Scheuermann ◽  
L. Li ◽  
D. Bringemeier
Keyword(s):  
Gas Flow ◽  
Structural Information ◽  
Porous Matrix ◽  
Groundwater Levels ◽  
Micro Scale ◽  
Wide Range ◽  
Boltzmann Method ◽  
The Impact ◽  
Flow Experiments

Coal mining raises a number of environmental and operational challenges, including the impact of changing groundwater levels and flow patterns on adjacent aquifer and surface water systems. Therefore it is of paramount importance to fully understand the flow of water and gases in the geological system on all scales. Flow in coal seams takes place on a wide range of scales from large faults and fractures to the micro-structure of a porous matrix intersected by a characteristic cleat network. On the micro-scale these cleats provide the principal source of permeability for fluid and gas flow. Description of the behaviour of the flow within the network is challenging due to the variations in number, sizing, orientation, aperture and connectivity at a given site. This paper presents a methodology to simulate flow and investigate the permeability of fractured media. A profound characterization of the geometry of the cleat network in micrometer resolution can be derived by CT-scans. The structural information is fed into a Lattice Boltzmann Method (LBM) based model that allows the implementation of virtual flow experiments. With the application of suitable hydraulic boundary conditions the full permeability tensor can be calculated in 3D.

scholarly journals Numerical Study of Hydrodynamic Impact on Bubbly Water

2015 ◽  
Author(s):  
Mehdi Elhimer ◽  
Aboulghit El Malki Alaoui ◽  
Kilian Croci ◽  
Céline Gabillet ◽  
Nicolas Jacques
Keyword(s):  
Volume Fraction ◽  
Numerical Study ◽  
Numerical Data ◽  
Void Volume Fraction ◽  
Bubbly Liquid ◽  
Impact Loads ◽  
Hydrodynamic Impact ◽  
Physical Mechanisms ◽  
The Impact ◽  
The Relationship

The phenomenon of slamming on a bubbly liquid has many occurrences in marine and costal engineering. However, experimental or numerical data on the effect of the presence of gas bubbles within the liquid on the impact loads are scarce and the related physical mechanisms are poorly understood. The aim of the present paper is to study numerically the relationship between the void volume fraction and the impact loads. For that purpose, numerical simulations of the impact of a cone on bubbly water have been performed using the finite element code ABAQUS/Explicit. The present results show the diminution of the impact loads with the increase of the void fraction. This effect appears to be related to the high compressibility of the liquid-gas mixture.

scholarly journals Creating Model of Sustainable Performance based Green Management System on The Small and Medium Enterprises

2020 ◽  
Vol 9 (3) ◽  
pp. 340-349
Author(s):  
Vini Wiratno Putri ◽  
Ketut Sudarma
Keyword(s):  
Structural Equation ◽  
Quantitative Research ◽  
Small And Medium Enterprises ◽  
Numerical Data ◽  
Industrial Sector ◽  
Research Approach ◽  
Competitive Advantages ◽  
Green Management ◽  
Sustainability Performance ◽  
The Impact

The aims of this paper is to analyze the effect of the relationship between knowledge and on green management and its implication on competitive advantage and sustainable performannce. This study used a quantitative research approach that explains the phenomenon by collecting numerical data analyzed using structural equation modelling (SEM) with the WarpPLS program application. The population in this study were small or medium business owners (general managers) in the industrial sector in the city of Semarang. Knowledge and green management have a significant effect on competitive advantages and competitive advantages has a significant effect on the sustainability performance. It means that the knowledge and green management simultaneously shows a significant effect on competitive advantages and sustainability performance. The application of green management will also improve sustainability performance. The originality of this study is on the testing of simultaneous relationships between the factors making up the application of green management, namely knowledge as well as the impact of green management implementation on sustainability performance.

scholarly journals Straight to Low-Sinuosity Drainage Systems in a Variscan-Type Orogen—Constraints from Tectonics, Lithology and Climate

Minerals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 933
Author(s):  
Harald G. Dill ◽  
Andrei Buzatu ◽  
Sorin-Ionut Balaban
Keyword(s):  
Chemical Weathering ◽  
Current Model ◽  
Drainage System ◽  
Numerical Data ◽  
Structural Features ◽  
Acute Angle ◽  
Drainage Systems ◽  
Starting Point ◽  
Bedrock Lithology ◽  
The Impact

A holistic-modular approach has been taken to study the evolution of three straight to low-sinuosity drainage systems (=SSS) in an uplifted basement block of the Central European Variscides. The development of the SSS is described by means of a quadripartite model. (1) The geological framework of the SSS: Forming the lithological and structural features in the bedrock as a result of different temperature, pressure and dynamic-metamorphic processes. (2) Prestage of SSS: Forming the paleo-landscape with a stable fluvial regime as a starting point for the SSS. (3) Proto-SSS: Transition into the metastable fluvial regime of the SSS. (4) Modern SSS: Operation of the metastable fluvial regime Tectonics plays a dual role. Late Paleozoic fold tectonic creates the basis for the studied SSS and has a guiding effect on the development of morphotectonic units during the Neogene and Quaternary. Late Cenozoic fault tectonics triggered the SSS to incise into the Paleozoic basement. The change in the bedrock lithology has an impact on the fluvial and colluvial sediments as well as their landforms. The latter reflects a conspicuous modification: straight drainage system ⇒ higher sinuosity and paired terraces ⇒ hillwash plains. Climate change has an indirect effect controlling via the bedrock the intensity of mechanical and chemical weathering. The impact on the development of the SSS can be assessed as follows: Tectonics >> climate ≅ bedrock lithology. The three parameters cause a facies zonation: (1) wide-and-shallow valley (Miocene), (2) wide-angle V-shaped valley (Plio-Pleistocene), (3) acute-angle V-shaped valley (Pleistocene), (4) V-shaped to U-shaped valleys (Pleistocene-Holocene). Numerical data relevant for the hydrographic studies of the SSS are determined in each reference area: (1) Quantification of fluvial and colluvial deposits along the drainage system, (2) slope angles, (3) degree of sinuosity as a function of river facies, (4) grain size distribution, (5) grain morphological categorization, (6) grain orientation (“situmetry”), (7) channel density, (8) channel/floodplain ratios. Thermodynamic computations (Eh, pH, concentration of solubles) are made to constrain the paleoclimatic regime during formation of the SSS. The current model of the SSS is restricted in its application to the basement of the Variscan-Type orogens, to an intermediate crustal maturity state.

scholarly journals IMPACT OF TURBINE-STRUT CLOCKING ON THE PERFORMANCE OF A TURBINE CENTER FRAME

2021 ◽  
pp. 1-17
Author(s):  
Patrick Zeno Sterzinger ◽  
Filippo Merli ◽  
Andreas Peters ◽  
Stephan Behre ◽  
Franz Heitmeir ◽  
...  
Keyword(s):  
Flow Field ◽  
Numerical Data ◽  
Performance Impact ◽  
Test Vehicle ◽  
Low Pressure Turbine ◽  
Second Stage ◽  
University Of Technology ◽  
Turbine Vane ◽  
Carry Over ◽  
The Impact

Abstract Previous studies have indicated a potential for improving the performance of a Turbine Center Frame (TCF) duct by op- timizing the clocking position between the high-pressure-turbine (HPT) vanes and TCF struts. To assess the impact of clocking on the performance, a new test vehicle with a clockable ratio of HPT vanes to TCF struts, consisting of an HPT stage (aero- dynamically representative of the second-stage HPT engine), a TCF duct with non-turning struts, and a first-stage low-pressure turbine vane, was designed and tested in the transonic test tur- bine facility (TTTF) at Graz University of Technology. This paper quantifies the performance impact of clocking and describes the mechanisms causing TCF flow field changes, lever- aging both experimental and numerical data. Other areas in the TCF duct impacted by the choice of the HPT vane circumfer- ential position including the strength of unsteady HPT-TCF in- teraction modes, TCF strut incidence changes, and carry-over effects to the first LPT vane are additionally highlighted. Five-hole-probe (5HP) area traverses and kielhead-rake tra- verses were used to asses the flow field at the TCF-exit and calcu- late the pressure loss. The flow field at the TCF exit shows signif- icant differences depending on the circumferential position of the HPT vane. A relative performance benefit of 5% was achieved.

Characterization of Nonlinear Rattling Behavior of a Gear Pair Through a Validated Torsional Model

2021 ◽  
Author(s):  
Ata Donmez ◽  
Ahmet Kahraman
Keyword(s):  
Piecewise Linear ◽  
Nonlinear Behavior ◽  
Severity Index ◽  
System Response ◽  
Gear Pair ◽  
Computationally Efficient ◽  
Linear Solution ◽  
Set Up ◽  
The Impact ◽  
Gear Rattle

Abstract Dynamic response of a gear pair subjected to input and output torque or velocity fluctuations is examined analytically. Such motions are commonly observed in various powertrain systems and identified as gear rattle or hammering motions with severe noise and durability consequences. A reduced-order torsional model is proposed along with a computationally efficient piecewise-linear solution methodology to characterize the system response including its sensitivity to excitation parameters. Validity of the proposed model is established through comparisons of its predictions to measurements from a gear rattle experimental set-up. A wide array of nonlinear behavior is demonstrated through presentation of periodic and chaotic responses in the forms of phase plots, Poincaré maps, and bifurcation diagrams. The severity of the resultant impacts on the noise outcome is also assessed through a rattle severity index defined by using the impact velocities.

scholarly journals Cutaneous leishmaniasis a neglected tropical disease: community knowledge, attitude and practices in an endemic area, Northwest Ethiopia

2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Helina Fikre Tamiru ◽  
Yohana James Mashalla ◽  
Rezika Mohammed ◽  
Gloria Thupayagale Tshweneagae
Keyword(s):  
Cutaneous Leishmaniasis ◽  
Rural Areas ◽  
Neglected Tropical Diseases ◽  
Numerical Data ◽  
Northwest Ethiopia ◽  
Duration Of Treatment ◽  
Cross Sectional ◽  
Awareness Campaigns ◽  
Modern Treatment ◽  
The Impact

Abstract Background Cutaneous leishmaniasis is one of the neglected tropical diseases in the Ethiopian highlands and studies on assessment of knowledge, attitude and practice of the community in endemic areas are scanty. The study aimed to assess the knowledge, attitude towards cutaneous leishmaniasis and treatment seeking practices in people living in the endemic highlands areas in the Northwest, Ethiopia and to provide evidence-based information to guide development of appropriate interventions to reduce the impact of cutaneous leishmaniasis on communities. Methods Quantitative cross-sectional study was conducted in cutaneous leishmaniasis endemic districts (woredas) using a semi structured questionnaire. Households were randomly selected according to probability proportional to size of households in each enumeration area. Systematic random sampling of eligible households was based on the number of households recorded during listing of households. Descriptive statistics was used to describe numerical data, organise and summarise the data in a manner that gave meaning to the numerical form. Frequency tables were used to show descriptive analysis and regression analysis was used to determine correlation between variables. Results Majority of respondents 321(78.7%) lived in rural areas, age ranged between 18 and 85 years and most were farmers. Illiteracy was high (47.6%) among respondents and majority 358(87.8%) had seen patients with CL. Less than quarter (21.6%) had heard about sand flies and knowledge on the peak transmission period was low (46.3%). About 192 (47.1%) of the respondents indicated disfiguring lesions were the major clinical presentations, less than half 55(27.5%) of urban residents believed CL was treatable compared to 145(72.5%) of rural residents (P < 0.001). Traditional medicines were indicated as best treatment option by 209(51.2%) compared to 114(27.9%) for modern treatment. Major factors influencing treatment options included accessibility to treatment facilities, distance and short duration of treatment. Participants expressed negative experiential attitude and perceived control towards modern treatment because of inaccessibility and distance from where modern treatment is provided. Conclusion Priority should be given to primary prevention and appropriate awareness campaigns on lesion recognition. Information on modern treatment should be intensified.

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