scholarly journals Numerical Study of Bubble Breakup in Fractal Tree-Shaped Microchannels

2019 ◽  
Vol 20 (21) ◽  
pp. 5516
Author(s):  
Chengbin Zhang ◽  
Xuan Zhang ◽  
Qianwen Li ◽  
Liangyu Wu
Keyword(s):  
Stream Flow ◽  
Numerical Study ◽  
Flow Direction ◽  
Underlying Mechanism ◽  
Two Dimensional ◽  
Bubble Breakup ◽  
Hydrodynamic Behaviors ◽  
Different Levels ◽  
Inlet Capillary ◽  
Insight Into

Hydrodynamic behaviors of bubble stream flow in fractal tree-shaped microchannels is investigated numerically based on a two-dimensional volume of fluid (VOF) method. Bubble breakup is examined in each level of bifurcation and the transition of breakup regimes is discussed in particular. The pressure variations at the center of different levels of bifurcations are analyzed in an effort to gain further insight into the underlying mechanism of bubble breakup affected by multi-levels of bifurcations in tree-shaped microchannel. The results indicate that due to the structure of the fractal tree-shaped microchannel, both lengths of bubbles and local capillary numbers decrease along the microchannel under a constant inlet capillary number. Hence the transition from the obstructed breakup and obstructed-tunnel combined breakup to coalescence breakup is observed when the bubbles are flowing into a higher level of bifurcations. Compared with the breakup of the bubbles in the higher level of bifurcations, the behaviors of bubbles show stronger periodicity in the lower level of bifurcations. Perturbations grow and magnify along the flow direction and the flow field becomes more chaotic at higher level of bifurcations. Besides, the feedback from the unequal downstream pressure to the upstream lower level of bifurcations affects the bubble breakup and enhances the upstream asymmetrical behaviors.

Numerical study of Love wave propagation

Geophysics ◽  
1983 ◽  
Vol 48 (7) ◽  
pp. 833-853 ◽  
Author(s):  
K. R. Kelly
Keyword(s):  
Numerical Modeling ◽  
Wave Propagation ◽  
Love Wave ◽  
Fourier Transforms ◽  
Narrow Band ◽  
Numerical Study ◽  
Two Dimensional ◽  
Band Pass ◽  
The Waves ◽  
Insight Into

Love wave propagation is studied by investigating numerical modeling results for several examples of geologic interest. The modal characteristics of the results are clarified by the use of narrow band‐pass filters and two‐dimensional Fourier transforms in range and time. Such processing makes it possible to study changes in phase and group velocity for the various modes and to locate points of reflection. This permits one to gain insight into changes in the physical properties of the surface channel supporting the waves.

Simulation of Convective Flows in Sinusoidal Partitioned Enclosure

2009 ◽  
Author(s):  
S. H. Anilkumar ◽  
Biju T. Kuzhiveli
Keyword(s):  
Numerical Study ◽  
Valuable Insight ◽  
Two Dimensional ◽  
Flow And Heat Transfer ◽  
Aspect Ratios ◽  
Experimental Works ◽  
Isothermal Wall ◽  
Oriented Parallel ◽  
Rayleigh Numbers ◽  
Insight Into

A numerical study is carried out for natural convective flow and heat transfer in a two-dimensional enclosure with centrally located sinusoidal thin partition for a range of Rayleigh numbers, partition heights and aspect ratios. The partition is oriented parallel to the two vertical isothermal walls and the other surfaces are insulated. The flow and temperature distributions are taken to be two-dimensional. Transport equations are modeled by a stream function-vorticity formulation and are solved numerically by finite-difference approach. Comparisons with previously published numerical and experimental works are done and found to be in excellent agreement. The Rayleigh number varies from 103 to 106 and aspect ratio from 0.5 to 5. The results are presented for different fluids in the form of streamlines, vectors and isotherm plots. The variation of local Nusselt number over the sinusoidal partition and isothermal wall provide valuable insight into the physical processes.

Late Quaternary downcutting rates of the Qianyou river from U/Th speleothem Dates, Qinling mountains, China

2004 ◽  
Vol 62 (2) ◽  
pp. 194-200 ◽  
Author(s):  
Wang Fei ◽  
Li Hongchun ◽  
Zhu Rixiang ◽  
Qin Feizhou
Keyword(s):  
Late Quaternary ◽  
Underlying Mechanism ◽  
Interglacial Period ◽  
Qinling Mountains ◽  
Direct Response ◽  
Dating Method ◽  
Wet Weather ◽  
The City ◽  
Different Levels ◽  
Insight Into

Dating deposits in caves formed by rivers may yield insight into rates and processes of bedrock incision. Three cave passages at different levels have developed in the walls of the Qianyou River valley in the Qinling mountains, south of the city of Xian, China. Twelve speleothem samples near the position of palaeowater tables in three cave passages are dated by the 230Th dating method. The results show that the river cut down at the rate of 0.23 ± 0.02 mm/yr from 358,000 ± 38,000 to 247,000 ± 28,000 yr ago, 0.19 ± 0.03 mm/yr from 247,000 ± 28,000 to 118,000 ± 19,000 yr ago, and 0.51 ± 0.08 mm/yr from 118,000 ± 19,000 yr ago until today. These fall very close to the glacial–interglacial transition following marine oxygen isotope stages 10, 8, and 6, respectively. The increase in downcutting rates during the interglacial period is consistent with warm, wet weather, increasing rates of erosion. This may lead us toward an underlying mechanism for modulating incision that is not in a direct response to the presence of headwater glaciers.

scholarly journals Magnetic Effects on Microstructure and Solute Plume Dynamics of Directionally Solidifying Ga-In Alloy

JOM ◽  
2020 ◽  
Vol 72 (10) ◽  
pp. 3645-3651
Author(s):  
Andrew Kao ◽  
Natalia Shevchenko ◽  
Shengya He ◽  
Peter D. Lee ◽  
Sven Eckert ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Numerical Study ◽  
Flow Direction ◽  
Dendritic Structure ◽  
Underlying Mechanism ◽  
Transverse Magnetic ◽  
High Concentration ◽  
Plume Migration ◽  
Hydrodynamic Phenomenon ◽  
The Magnetic Field

Abstract The effects of applying a 0.2-T transverse magnetic field on a solidifying Ga-25 wt%In alloy have been investigated through a joint experimental and numerical study. The magnetic field introduced significant changes to both the microstructure and the dynamics of escaping high-concentration Ga plumes. Plume migration across the interface was quantified and correlated to simulations to demonstrate that thermoelectric magnetohydrodynamics (TEMHD) is the underlying mechanism. TEMHD introduced macrosegregation within the dendritic structure, leading to the formation of a stable “chimney” channel by increasing the solutal buoyancy in the flow direction. The resulting pressure difference across the solidification front introduced a secondary hydrodynamic phenomenon that subsequently caused solute plume migration.

Numerical Study on Two-dimensional Magnetic Photonic Crystals Made of Magnetized Ferrites

PIERS Online ◽  
2007 ◽  
Vol 3 (3) ◽  
pp. 305-307 ◽  
Author(s):  
Jie Xu ◽  
Ping Chen ◽  
Yue Shi ◽  
Xin-Yi Ji ◽  
Ai-Min Jiang ◽  
...  
Keyword(s):  
Photonic Crystals ◽  
Numerical Study ◽  
Two Dimensional ◽  
Magnetic Photonic Crystals

Co-planar two-dimensional Metal-Insulator-Semiconductor Capacitor: Numerical study of the device electrostatics.

2017 ◽  
Author(s):  
Varun Bheemireddy
Keyword(s):  
Space Charge ◽  
High Performance ◽  
Numerical Study ◽  
2D Materials ◽  
Space Charge Density ◽  
Two Dimensional ◽  
Short Channel ◽  
Metal Insulator ◽  
Metal Insulator Semiconductor ◽  
New Family

The two-dimensional(2D) materials are highly promising candidates to realise elegant and e cient transistor. In the present letter, we conjecture a novel co-planar metal-insulator-semiconductor(MIS) device(capacitor) completely based on lateral 2D materials architecture and perform numerical study of the capacitor with a particular emphasis on its di erences with the conventional 3D MIS electrostatics. The space-charge density features a long charge-tail extending into the bulk of the semiconductor as opposed to the rapid decay in 3D capacitor. Equivalently, total space-charge and semiconductor capacitance densities are atleast an order of magnitude more in 2D semiconductor. In contrast to the bulk capacitor, expansion of maximum depletion width in 2D semiconductor is observed with increasing doping concentration due to lower electrostatic screening. The heuristic approach of performance analysis(2D vs 3D) for digital-logic transistor suggest higher ON-OFF current ratio in the long-channel limit even without third dimension and considerable room to maximise the performance of short-channel transistor. The present results could potentially trigger the exploration of new family of co-planar at transistors that could play a signi significant role in the future low-power and/or high performance electronics.<br>

scholarly journals Design of a Novel Miniaturized Frequency Selective Surface Based on 2.5-Dimensional Jerusalem Cross for 5G Applications

2018 ◽  
Vol 2018 ◽  
pp. 1-6 ◽  
Author(s):  
Peng Zhao ◽  
Yihang Zhang ◽  
Rongrong Sun ◽  
Wen-Sheng Zhao ◽  
Yue Hu ◽  
...  
Keyword(s):  
Resonant Frequency ◽  
Equivalent Circuit ◽  
Equivalent Circuit Model ◽  
Frequency Selective Surface ◽  
Size Reduction ◽  
Two Dimensional ◽  
Physical Insight ◽  
Frequency Selective ◽  
Significant Size ◽  
Insight Into

A compact frequency selective surface (FSS) for 5G applications has been designed based on 2.5-dimensional Jerusalem cross. The proposed element consists of two main parts: the successive segments of the metal traces placed alternately on the two surfaces of the substrate and the vertical vias connecting traces. Compared with previous published two-dimensional miniaturized elements, the transmission curves indicate a significant size reduction (1/26 wavelengths at the resonant frequency) and exhibit good angular and polarization stabilities. Furthermore, a general equivalent circuit model is established to provide direct physical insight into the operating principle of this FSS. A prototype of the proposed FSS has been fabricated and measured, and the results validate this design.

scholarly journals Generation of Reverse Meniscus Flow by Applying An Electromagnetic Brake

2021 ◽  
Author(s):  
Alexander Vakhrushev ◽  
Abdellah Kharicha ◽  
Ebrahim Karimi-Sibaki ◽  
Menghuai Wu ◽  
Andreas Ludwig ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Lorentz Force ◽  
Applied Magnetic Field ◽  
Numerical Study ◽  
Flow Direction ◽  
Experimental Studies ◽  
Submerged Entry Nozzle ◽  
Mean Flow ◽  
Slab Caster ◽  
The Mean

AbstractA numerical study is presented that deals with the flow in the mold of a continuous slab caster under the influence of a DC magnetic field (electromagnetic brakes (EMBrs)). The arrangement and geometry investigated here is based on a series of previous experimental studies carried out at the mini-LIMMCAST facility at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The magnetic field models a ruler-type EMBr and is installed in the region of the ports of the submerged entry nozzle (SEN). The current article considers magnet field strengths up to 441 mT, corresponding to a Hartmann number of about 600, and takes the electrical conductivity of the solidified shell into account. The numerical model of the turbulent flow under the applied magnetic field is implemented using the open-source CFD package OpenFOAM®. Our numerical results reveal that a growing magnitude of the applied magnetic field may cause a reversal of the flow direction at the meniscus surface, which is related the formation of a “multiroll” flow pattern in the mold. This phenomenon can be explained as a classical magnetohydrodynamics (MHD) effect: (1) the closure of the induced electric current results not primarily in a braking Lorentz force inside the jet but in an acceleration in regions of previously weak velocities, which initiates the formation of an opposite vortex (OV) close to the mean jet; (2) this vortex develops in size at the expense of the main vortex until it reaches the meniscus surface, where it becomes clearly visible. We also show that an acceleration of the meniscus flow must be expected when the applied magnetic field is smaller than a critical value. This acceleration is due to the transfer of kinetic energy from smaller turbulent structures into the mean flow. A further increase in the EMBr intensity leads to the expected damping of the mean flow and, consequently, to a reduction in the size of the upper roll. These investigations show that the Lorentz force cannot be reduced to a simple damping effect; depending on the field strength, its action is found to be topologically complex.

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