scholarly journals Air entrapment and bubble formation during droplet impact onto a single cubic pillar

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Weibo Ren ◽  
Patrick Foltyn ◽  
Anne Geppert ◽  
Bernhard Weigand
Keyword(s):  
Numerical Simulations ◽  
Morphological Changes ◽  
Bubble Formation ◽  
Three Dimensional ◽  
Air Entrapment ◽  
Droplet Dynamics ◽  
Entrapped Air ◽  
The Impact ◽  
Insight Into ◽  
Vertical Impact

AbstractWe study the vertical impact of a droplet onto a cubic pillar of comparable size placed on a flat surface, by means of numerical simulations and experiments. Strikingly, during the impact a large volume of air is trapped around the pillar side faces. Impingement upon different positions of the pillar top surface strongly influences the size and the position of the entrapped air. By comparing the droplet morphological changes during the impact from both computations and experiments, we show that the direct numerical simulations, based on the Volume of Fluid method, provide additional and new insight into the droplet dynamics. We elucidate, with the computational results, the three-dimensional air entrapment process as well as the evolution of the entrapped air into bubbles.

Vortex rings impinging on walls: axisymmetric and three-dimensional simulations

1993 ◽  
Vol 256 ◽  
pp. 615-646 ◽  
Author(s):  
Paolo Orlandi ◽  
Roberto Verzicco
Keyword(s):  
Numerical Simulations ◽  
Strain Tensor ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Vortex Rings ◽  
Compression Phase ◽  
Vortex Pairing ◽  
The Impact ◽  
Good Agreement ◽  
Three Dimensional Simulations

Accurate numerical simulations of vortex rings impinging on flat boundaries revealed the same features observed in experiments. The results for the impact with a free-slip wall compared very well with previous numerical simulations that used spectral methods, and were also in qualitative agreement with experiments. The present simulation is mainly devoted to studying the more realistic case of rings interacting with a no-slip wall, experimentally studied by Walker et al. (1987). All the Reynolds numbers studied showed a very good agreement between experiments and simulations, and, at Rev > 1000 the ejection of a new ring from the wall was seen. Axisymmetric simulations demonstrated that vortex pairing is the physical mechanism producing the ejection of the new ring. Three-dimensional simulations were also performed to investigate the effects of azimuthal instabilities. These simulations have confirmed that high-wavenumber instabilities originate in the compression phase of the secondary ring within the primary one. The large instability of the secondary ring has been explained by analysis of the rate-of-strain tensor and vorticity alignment. The differences between passive scalars and the vorticity field have been also investigated.

Impact of Cavity on Sunroof Buffeting: A Two Dimensional CFD Study

2004 ◽  
Author(s):  
Chang-Fa An ◽  
Seyed Mehdi Alaie ◽  
Michael S. Scislowicz
Keyword(s):  
Fluid Dynamics ◽  
Wind Tunnel ◽  
Three Dimensional ◽  
Leading Edge ◽  
Two Dimensional ◽  
Deep Insight ◽  
Simulation Results ◽  
Dimensional Simulation ◽  
The Impact ◽  
Insight Into

Driven by fluid dynamics principles, the concept for buffeting reduction, a cavity installed at the leading edge of the sunroof opening, is analyzed. The cavity provides a room to hold the vortex, shed from upstream, and prevents the vortex from escaping and from directly intruding into the cabin. The concept has been verified by means of a two dimensional simulation for a production SUV using the CFD software — FLUENT. The simulation results show that the impact of the cavity is crucial to reduce buffeting. It is shown that the buffeting level may be reduced by 3 dB by adding a cavity to the sunroof configuration. Therefore, the cavity could be considered as a means of buffeting reduction, in addition to the three currently-known concepts: wind deflector, sunroof glass comfort position and cabin venting. Thorough understanding of the buffeting mechanism helps explain why and how the cavity works to reduce buffeting. Investigation of the buffeting-related physics provides a deep insight into the flow nature and, therefore, a useful hint to geometry modification for buffeting reduction. The buffeting level may be further reduced by about 4 dB or more by cutting the corners of the sunroof opening into smooth ramps, guided by ideas coming from careful examining the physics of flow. More work including three dimensional simulation and wind tunnel experiment should follow in order to develop more confidence in the functionality of the cavity to hopefully promote this idea to the level that it can be utilized in a feasible way to address sunroof buffeting.

scholarly journals Assessing the Impact of the Tropopause on Mountain Waves and Orographic Precipitation Using Linear Theory and Numerical Simulations

2015 ◽  
Vol 72 (2) ◽  
pp. 803-820 ◽  
Author(s):  
Nicholas Siler ◽  
Dale Durran
Keyword(s):  
Numerical Simulations ◽  
Linear Theory ◽  
Three Dimensional ◽  
Orographic Precipitation ◽  
Two Dimensional ◽  
Tropopause Height ◽  
Atmospheric Conditions ◽  
Mountain Waves ◽  
Wave Induced ◽  
The Impact

Abstract The partial reflection of mountain waves at the tropopause has been studied extensively for its contribution to downslope windstorms, but its impact on orographic precipitation has not been addressed. Here linear theory and numerical simulations are used to investigate how the tropopause affects the vertical structure of mountain waves and, in turn, orographic precipitation. Relative to the no-tropopause case, wave-induced ascent above the windward slope of a two-dimensional ridge is found to be enhanced or diminished depending on the ratio of the tropopause height to the vertical wavelength of the mountain waves—defined here as the “nondimensional tropopause height” . In idealized simulations of flow over both two-dimensional and three-dimensional ridges, variations in are found to modulate the precipitation rate by roughly a factor of 2 under typical atmospheric conditions. The sensitivity of precipitation to is related primarily to the depth of windward ascent but also to the location and strength of leeside descent, with significant impacts on the distribution of precipitation across the range (i.e., the rain-shadow effect). Using a modified version of Smith and Barstad’s orographic precipitation model, variations in are found to produce significant rain-shadow variability in the Washington Cascades, perhaps explaining some of the variability in rain-shadow strength observed among Cascade storms.

scholarly journals WaveRange: wavelet-based data compression for three-dimensional numerical simulations on regular grids

2022 ◽  
Author(s):  
Dmitry Kolomenskiy ◽  
Ryo Onishi ◽  
Hitoshi Uehara
Keyword(s):  
Numerical Simulations ◽  
Wavelet Decomposition ◽  
Three Dimensional ◽  
Global Scale ◽  
Software Framework ◽  
Simulation Data ◽  
Numerical Tests ◽  
Point Data ◽  
Dimensional Simulation ◽  
The Impact

Abstract A wavelet-based method for compression of three-dimensional simulation data is presented and its software framework is described. It uses wavelet decomposition and subsequent range coding with quantization suitable for floating-point data. The effectiveness of this method is demonstrated by applying it to example numerical tests, ranging from idealized configurations to realistic global-scale simulations. The novelty of this study is in its focus on assessing the impact of compression on post-processing and restart of numerical simulations. Graphical abstract

scholarly journals Modeling the Effect of External Computers and Removable Devices on a Computer Network with Heterogeneous Immunity

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Walaa S. Bahashwan ◽  
Salma M. Al-Tuwairqi
Keyword(s):  
Sensitivity Analysis ◽  
Theoretical Analysis ◽  
Numerical Simulations ◽  
Computer Network ◽  
Asymptotically Stable ◽  
Virus Spread ◽  
Globally Asymptotically Stable ◽  
Virus Prevalence ◽  
The Impact ◽  
Insight Into

This paper intends to investigate the impact of external computers and removable devices on virus spread in a network with heterogeneous immunity. For that purpose, a new dynamical model is presented and discussed. Theoretical analysis reveals the existence of a unique viral equilibrium that is locally and globally asymptotically stable with no criteria. This result implies that efforts to eliminate viruses are not possible. Therefore, sensitivity analysis is performed to have more insight into parameters’ impact on virus prevalence. As a result, strategies are suggested to contain virus spread to an acceptable level. Finally, to rationalize the analytical results, we execute some numerical simulations.

scholarly journals The Impact of Capillary Trapping of Air on Satiated Hydraulic Conductivity of Sands Interpreted by X-ray Microtomography

Water ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 445 ◽  
Author(s):  
Tomas Princ ◽  
Helena Maria Reis Fideles ◽  
Johannes Koestel ◽  
Michal Snehota
Keyword(s):  
Hydraulic Conductivity ◽  
Air Bubbles ◽  
Air Entrapment ◽  
X Ray ◽  
Capillary Trapping ◽  
Air Content ◽  
X Ray Computed ◽  
Entrapped Air ◽  
The Impact ◽  
The Relationship

The relationship between entrapped air content and the corresponding hydraulic conductivity was investigated experimentally for two coarse sands. Two packed samples of 5 cm height were prepared for each sand. Air entrapment was created by repeated infiltration and drainage cycles. The value of K was determined using repetitive falling-head infiltration experiments, which were evaluated using Darcy’s law. The entrapped air content was determined gravimetrically after each infiltration run. The amount and distribution of air bubbles were quantified by micro-computed X-ray tomography (CT) for selected runs. The obtained relationship between entrapped air content and satiated hydraulic conductivity agreed well with Faybishenko’s (1995) formula. CT imaging revealed that entrapped air contents and bubbles sizes were increasing with the height of the sample. It was found that the size of the air bubbles and clusters increased with each experimental cycle. The relationship between initial and residual gas saturation was successfully fitted with a linear model. The combination of X-ray computed tomography and infiltration experiments has a large potential to explore the effects of entrapped air on water flow.

Air Cavities in a Vibrated Bed of Visco-Elastic Glass Balls

2008 ◽  
Vol 130 (6) ◽  
Author(s):  
Piroz Zamankhan
Keyword(s):  
Particle Size ◽  
Granular Materials ◽  
Large Scale ◽  
Bubble Formation ◽  
Three Dimensional ◽  
Critical Value ◽  
Wave Fronts ◽  
Turbulent Fluctuations ◽  
Air Cavities ◽  
Insight Into

Large scale, three dimensional computer simulations of a dense aggregative bed were performed to provide insight into the physics behind bubble formation in vertically vibrated granular materials in a shaker. As the shaker acceleration exceeds a critical value, turbulent fluctuations proportional to the particle size were produced to promote fractures at the interface between the gas and particles suspended in the gas near the bottom of the shaker. As the wave fronts pass, the solid fractures took the form of sharply defined regions of very low solids fraction (air cavities) that rose through the bed with a speed that depends on their size. The nucleation of bubbles is found to be of the heterogeneous type.

An Assessment of the Potential of Tidal Power From Minas Passage, Bay of Fundy, Using Three-Dimensional Models

2011 ◽  
Author(s):  
Richard Karsten
Keyword(s):  
Numerical Simulations ◽  
3D Structure ◽  
Three Dimensional ◽  
Tidal Currents ◽  
Total Power ◽  
Bay Of Fundy ◽  
Three Dimensional Model ◽  
Cross Sectional ◽  
Flow Through ◽  
The Impact

Large tidal currents exist in Minas Passage, which connects Minas Basin to the Bay of Fundy off the northwestern coast of Nova Scotia. The strong currents through this deep, narrow channel make it a promising location for the generation of electrical power using instream turbines. These strong currents are clearly illustrated in the results of a high-resolution, three-dimensional model of the flow through Minas Passage presented here. The simulations also clearly indicate the asymmetry of the flood and ebb tides and the 3D structure of the flow. A previous study has indicated that as much as 7000 MW could be extracted from the tidal currents through Minas Passage. However, this estimate was based on a complete fence of turbines across the passage, in essence a tidal barrage. In this paper, the power potential of partial turbine fences is examined. In order to estimate the power potential of turbine arrays, the theory of partial turbine fences is adapted to the particular dynamics of Minas Passage. The theory estimates the potential power of the fence and the change in flow that would result. The results are presented in terms of the portion of the cross-sectional area that the turbines occupy and the drag coefficient of the turbines. When the turbine fence occupies a large portion of the passage, the potential power of the fence rises significantly, to a value much larger than estimates based on the kinetic energy flux. The increase in power comes from the increased tidal head that a large turbine fence creates and the resulting increase in the turbine drag. We also present the efficiency of the turbine fence — given as the ratio of the power associated with the turbine drag over the total power extracted from the flow — and the impact of the turbines on the tidal flow. The results of the theory are compared to numerical simulations of the flow through the passage with turbines represented as regions of increased drag. The numerical simulations give power values that are three to six time as high as the theory suggests is possible. This discrepancy is examined by plotting the changes in tidal currents caused by the turbine fence.

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