scholarly journals Interface topology and evolution of particle patterns on deformable drops in turbulence

2022 ◽  
Vol 933 ◽  
Author(s):  
Arash Hajisharifi ◽  
Cristian Marchioli ◽  
Alfredo Soldati
Keyword(s):  
Particle Surface ◽  
Surface Velocity ◽  
Excluded Volume ◽  
Particle Collisions ◽  
Lagrangian Particle ◽  
Surface Distribution ◽  
Trapping Regions ◽  
Drop Interface ◽  
Neutrally Buoyant

The capture of neutrally buoyant, sub-Kolmogorov particles at the interface of deformable drops in turbulent flow and the subsequent evolution of particle surface distribution are investigated. Direct numerical simulation of turbulence, phase-field modelling of the drop interface dynamics and Lagrangian particle tracking are used. Particle distribution is obtained considering excluded-volume interactions, i.e. by enforcing particle collisions. Particles are initially dispersed in the carrier flow and are driven in time towards the surface of the drops by jet-like turbulent fluid motions. Once captured by the interfacial forces, particles disperse on the surface. Excluded-volume interactions bring particles into long-term trapping regions where the average surface velocity divergence sampled by the particles is zero. These regions correlate well with portions of the interface characterized by higher-than-mean curvature, indicating that modifications of the surface tension induced by the presence of very small particles will be stronger in the highly convex regions of the interface.

Phosphorus removal by apatite in horizontal flow constructed wetlands for small communities: pilot and full-scale evidence

2011 ◽  
Vol 63 (8) ◽  
pp. 1629-1637 ◽  
Author(s):  
N. Harouiya ◽  
S. Martin Rue ◽  
S. Prost-Boucle ◽  
A. Liénar ◽  
D. Esser ◽  
...  
Keyword(s):  
Constructed Wetlands ◽  
Particle Surface ◽  
Full Scale ◽  
Retention Capacity ◽  
Small Communities ◽  
Lab Experiments ◽  
Apatite Mineral ◽  
Kinetics Of ◽  
P Removal

Phosphorus (P) removals in constructed wetlands (CWs) have received particular attention in recent decades by using specific materials which promote adsorption/precipitation mechanisms. Recent studies have shown interest in using apatite materials to promote P precipitation onto the particle surface. As previous trials were mainly done by lab experiments, this present study aims to evaluate the real potential of apatites to remove P from wastewater in pilot units and a full-scale plant over a 2 year period. P retention kinetics of two qualities of apatites are presented and discussed. In this work apatite appears to have high retention capacity (>80% of P removal) and is still an interesting way for P removal in CWs for limiting the risk of eutrophication downstream of small communities. Nevertheless, the apatite quality appears to be of great importance for a reliable and long term P removal. The use of materials with low content of apatite mineral (40–50%) seems to be not economically relevant.

scholarly journals Are longitudinal ice-surface structures on the Antarctic Ice Sheet indicators of long-term ice-flow configuration?

2014 ◽  
Vol 2 (2) ◽  
pp. 911-933 ◽  
Author(s):  
N. F. Glasser ◽  
S. J. A. Jennings ◽  
M. J. Hambrey ◽  
B. Hubbard
Keyword(s):  
Flow Line ◽  
Ice Sheet ◽  
Surface Structures ◽  
Surface Velocity ◽  
Ice Flow ◽  
Antarctic Ice Sheet ◽  
Ice Surface ◽  
Ice Stream ◽  
The Antarctic

Abstract. Continent-wide mapping of longitudinal ice-surface structures on the Antarctic Ice Sheet reveals that they originate in the interior of the ice sheet and are arranged in arborescent networks fed by multiple tributaries. Longitudinal ice-surface structures can be traced continuously down-ice for distances of up to 1200 km. They are co-located with fast-flowing glaciers and ice streams that are dominated by basal sliding rates above tens of m yr-1 and are strongly guided by subglacial topography. Longitudinal ice-surface structures dominate regions of converging flow, where ice flow is subject to non-coaxial strain and simple shear. Associating these structures with the AIS' surface velocity field reveals (i) ice residence times of ~ 2500 to 18 500 years, and (ii) undeformed flow-line sets for all major flow units analysed except the Kamb Ice Stream and the Institute and Möller Ice Stream areas. Although it is unclear how long it takes for these features to form and decay, we infer that the major ice-flow and ice-velocity configuration of the ice sheet may have remained largely unchanged for several thousand years, and possibly even since the end of the last glacial cycle. This conclusion has implications for our understanding of the long-term landscape evolution of Antarctica, including large-scale patterns of glacial erosion and deposition.

scholarly journals POTENTIALITY OF THE BUGOJNO COAL BASIN, BOSNIA AND HERZEGOVINA

2021 ◽  
Vol 1 (24) ◽  
Author(s):  
Dževad Forčaković ◽  
Rejhana Dervišević
Keyword(s):  
Raw Material ◽  
Northwestern Part ◽  
Material Base ◽  
Coal Basin ◽  
Surface Distribution ◽  
Research Results ◽  
Geological Characteristics ◽  
Quantitative Characteristics

This paper presents research results of the Bugojno coal basin, which contains very significant, but still insufficiently explored lignite reserves. Based on the determined borders of surface distribution and the research results in the northwestern part of the Bugojno coal basin, proved are four coal layers with reserves of over one billion tons of coal. Discussed are geological characteristics of coal layers, their qualitative-quantitative characteristics, spatial potential of deposit and classification of coal layers. Considering the raw material potential and the possibility of expanding the existing raw material base, the Bugojno coal basin has particular importance for the long-term development of lignite exploitation and its use for thermal energy purposes.

Spending Less Than 100$ on Real-Time Sewer Flow Measurements

2021 ◽  
Author(s):  
Robert Meier ◽  
Franz Tscheikner-Gratl ◽  
Christos Makropoulos
Keyword(s):  
Water Level ◽  
Industrial Revolution ◽  
New Technologies ◽  
Surface Velocity ◽  
Prediction Algorithm ◽  
Raspberry Pi ◽  
Laboratory Setting ◽  
Flow Sensors ◽  
Flow Measurements

<p>As more and more computational power becomes available at increasingly affordable prices, the last years have seen a veritable explosion in the number of sensors and interconnected devices. This evolution is well known and often referred to as the 4th industrial revolution, or the IoT. The water sector, albeit often conservative in adopting new technologies, will profit from this continued digitalisation in various ways.</p><p>In this work we focus on the vision of covering entire sewer systems by tightly knit sensor networks which can process the generated amount of data simultaneously. Given the large number of sensors required, the only possibility to implement such a network is keeping costs as low as possible for the individual devices or use already existing sensors in multiple ways (e.g., traffic cameras helping in flood detection).</p><p>Using hardware of the Raspberry Pi ecosystem, currently retailing at less than 100$, we collected continuous video footage of an artificial open channel in a laboratory setting and used a deep neural network to extract the water level and surface velocity. The measurement accuracy of the prediction algorithm was then compared to conventional flow sensors to assess the practicality of this approach. Preliminary results in a laboratory setting indicate a sufficient prediction accuracy of the water level for engineering uses but further work is needed to verify this in a long-term field study.</p><p>After this initial stage, deploying the sensor in a real-world setting as part of the B-WaterSmart project is planned. Apart from verifying the results under real conditions, we will then be able to assess the long-term behaviour of this approach. This includes an evaluation of the maintenance effort. As the sensor is not in direct contact with the sewage, the typical need for frequent cleaning should be greatly reduced, which in turn is expected to further lower the costs.</p><p>We argue that if such a cheap sensor can ultimately be established as a viable alternative to more conventional flow sensors, the vision of sewer networks covered entirely by sensors, could become more attainable in practice.</p>

scholarly journals Ice-shelf Response to Ice-stream Discharge Fluctuations: I. Unconfined Ice Tongues

1988 ◽  
Vol 34 (116) ◽  
pp. 121-127 ◽  
Author(s):  
Douglas R. MacAyeal ◽  
Victor Barcilon
Keyword(s):  
Ice Shelf ◽  
Lagrangian Particle ◽  
Sea Level Fluctuations ◽  
Stream Discharge ◽  
Discharge Fluctuations ◽  
Ice Stream ◽  
Grounding Line ◽  
Velocity Changes ◽  
Particle Paths

AbstractIce-stream discharge fluctuations constitute an independent means of forcing unsteady ice-shelf behavior, and their effect must be distinguished from those of oceanic and atmospheric climate to understand ice-shelf change. In addition, ice-stream-generated thickness anomalies may constitute a primary trigger of ice-rise formation in the absence of major sea-level fluctuations. Such triggering may maintain the current ice-rise population that, in turn, contributes to long-term ice-sheet stability. Here, we show that ice-stream-generated fluctuations of an ideal, two-dimensional ice shelf propagate along two characteristic trajectories. One trajectory permits instantaneous transmission of grounding-line velocity changes to all points down-stream. The other trajectory represents slow transmission of grounding-line thickness changes along Lagrangian particle paths.

Seasonal to multi-annual speedup and slowdown of Greenland outlet glaciers inferred from time-dependent remote sensing observations

2020 ◽  
Author(s):  
Lizz Ultee ◽  
Bryan Riel ◽  
Brent Minchew
Keyword(s):  
Time Series ◽  
Flow Velocity ◽  
Ice Sheet ◽  
Surface Air Temperature ◽  
Greenland Ice Sheet ◽  
Time Dependent ◽  
Surface Velocity ◽  
Short Term ◽  
Ice Flow

<p>The rate of ice flux from the Greenland Ice Sheet to the ocean depends on the ice flow velocity through outlet glaciers. Ice flow velocity, in turn, evolves in response to multiple geographic and environmental forcings at different timescales. For example, velocity may vary daily in response to ocean tides, seasonally in response to surface air temperature, and multi-annually in response to long-term trends in climate. The satellite observations processed as part of the NASA MEaSUREs Greenland Ice Sheet Velocity Map allow us to analyse variations in ice surface velocity at multiple timescales. Here, we decompose short-term and long-term signals in time-dependent velocity fields for Greenland outlet glaciers based on the methods of Riel et al. (2018). Patterns found in short-term signals can constrain basal sliding relations and ice rheology, while the longer-term signals hint at decadal in/stability of outlet glaciers. We present example velocity time series for outlets including Sermeq Kujalleq (Jakobshavn Isbrae) and Helheim Glacier, and we highlight features indicative of dynamic drawdown or advective restabilization. Finally, we comment on the capabilities of a time series analysis software under development for glaciological applications.</p>

scholarly journals Ice-shelf Response to Ice-stream Discharge Fluctuations: I. Unconfined Ice Tongues

1988 ◽  
Vol 34 (116) ◽  
pp. 121-127 ◽  
Author(s):  
Douglas R. MacAyeal ◽  
Victor Barcilon
Keyword(s):  
Ice Shelf ◽  
Lagrangian Particle ◽  
Sea Level Fluctuations ◽  
Stream Discharge ◽  
Discharge Fluctuations ◽  
Ice Stream ◽  
Grounding Line ◽  
Velocity Changes ◽  
Particle Paths

AbstractIce-stream discharge fluctuations constitute an independent means of forcing unsteady ice-shelf behavior, and their effect must be distinguished from those of oceanic and atmospheric climate to understand ice-shelf change. In addition, ice-stream-generated thickness anomalies may constitute a primary trigger of ice-rise formation in the absence of major sea-level fluctuations. Such triggering may maintain the current ice-rise population that, in turn, contributes to long-term ice-sheet stability. Here, we show that ice-stream-generated fluctuations of an ideal, two-dimensional ice shelf propagate along two characteristic trajectories. One trajectory permits instantaneous transmission of grounding-line velocity changes to all points down-stream. The other trajectory represents slow transmission of grounding-line thickness changes along Lagrangian particle paths.

scholarly journals Lifting of Tribocharged Grains by Martian Winds

2021 ◽  
Vol 2 (6) ◽  
pp. 238
Author(s):  
Maximilian Kruss ◽  
Tim Salzmann ◽  
Eric Parteli ◽  
Felix Jungmann ◽  
Jens Teiser ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Electric Fields ◽  
Wind Shear ◽  
Particle Surface ◽  
Shear Velocity ◽  
Sand Transport ◽  
Particle Collisions ◽  
Surface Charges ◽  
Martian Soil ◽  
Open Question

Abstract It is a long-standing open question whether electrification of wind-blown sand due to tribocharging—the generation of electric charges on the surface of sand grains by particle–particle collisions—could affect rates of sand transport occurrence on Mars substantially. While previous wind tunnel experiments and numerical simulations addressed how particle trajectories may be affected by external electric fields, the effect of sand electrification remains uncertain. Here we show, by means of wind tunnel simulations under air pressure of 20 mbar, that the presence of electric charges on the particle surface can reduce the minimal threshold wind shear velocity for the initiation of sand transport, u *ft, significantly. In our experiments, we considered different samples, a model system of glass beads as well as a Martian soil analog, and different scenarios of triboelectrification. Furthermore, we present a model to explain the values of u *ft obtained in the wind tunnel that is based on inhomogeneously distributed surface charges. Our results imply that particle transport that subsides, once the wind shear velocity has fallen below the threshold for sustained transport, can more easily be restarted on Mars than previously thought.

scholarly journals Modelling Droplet Deformation for Sneezing Events using the Eulerian-Lagrangian Particle Surface Approach

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Filippo Gerbino ◽  
Konstantina Vogiatzaki ◽  
Robert Morgan ◽  
Penelope Atkins ◽  
Giovanni Tretola
Keyword(s):  
Particle Surface ◽  
Lagrangian Particle ◽  
Droplet Deformation ◽  
Surface Approach

scholarly journals Effect of Long-term Low Concentrations of TiO2 Nanoparticles on Dewaterability of Activated Sludge and the Relevant Mechanism: The Role of Nanoparticle Aging

2021 ◽  
Author(s):  
Chengyu Jiang ◽  
Qingjin Chen
Keyword(s):  
Activated Sludge ◽  
Batch Reactor ◽  
Sewage Treatment ◽  
Particle Surface ◽  
Scientific Management ◽  
Sludge Dewatering ◽  
Freshwater Environment ◽  
Low Concentrations ◽  
Concentration Levels

Abstract Nanoparticles can undergo aging phenomena that change their physical and chemical properties in sewage treatment systems. However, the effect of aged nanoparticles under long-term low concentrations on the dewatering performance of activated sludge in sewage treatment systems has not been reported yet. Here, we compared the chronic effects of pristine and aged TiO2 nanoparticles on sludge dewatering index including specific resistance to filtration (SRF) and bound water (BW) in the sequencing batch reactor (SBR) with the µg/L concentration levels and the relevant mechanisms were analyzed. The results show that the aging experiment in sludge supernatant could change the photosensitivity and water stability of nanoparticles, which was mainly due to the changes in the zeta potential and energy band of the particle, and ultimately attributed to the combined effect of particle surface inclusions such as organic matter and inorganic salt. At 10µg/L, nanoparticles could reduce the dewaterability of sludge, but at 100µg/L, nanoparticles could improve the dewaterability of sludge, because 10µg/L promoted the secretion of extracellular polymeric substance (EPS), regulated the structure of sludge flora and increased the abundance of secreting quorum sensing-acyl-homoserine lactones (QS-AHL) and EPS genera, while the corresponding exposure results of 100µg/L were the opposite, due to the damage and necrosis exposure effects of 100µg/L under long-term light, which reduced EPS production and increased sludge density. Interestingly, aging could alleviate the effects of two exposure concentrations on sludge dewatering, mainly being attributed to the decrease of the photoactivity of nanoparticles. The results of this study show that environmental aging could slow down, but cannot reverse the results of exposure to specific concentrations of nanoparticles. However, the ecological effects of photosensitive nanoparticles with two environmentally-relevant concentration levels of ug/L were significantly different, which should be refined and confirmed again in freshwater environment to provide a basis for subsequent scientific management and control of photosensitive nanoparticles.

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