scholarly journals Radial spreading of turbulent bubble plumes

2020 ◽  
Vol 378 (2179) ◽  
pp. 20190513
Author(s):  
Arna Sigurðardóttir ◽  
Jonathan Barnard ◽  
Danielle Bullamore ◽  
Amy McCormick ◽  
Julyan Cartwright ◽  
...  
Keyword(s):  
Linear Density ◽  
Laboratory Experiments ◽  
Spreading Rate ◽  
The Arctic ◽  
Theme Issue ◽  
Bubble Plumes ◽  
Radial Spreading ◽  
Spreading Rates ◽  
Study Laboratory ◽  
Volumetric Flowrate

Weak bubble plumes carry liquid from the environment upwards and release it at multiple intermediate levels in the form of radial intrusive currents. In this study, laboratory experiments are performed to explore the spreading of turbulent axisymmetric bubble plumes in a liquid with linear density stratification. The thickness, volumetric flowrate and spreading rates of multiple radial intrusions of plume fluid were measured by tracking the movement of dye injected at the source of bubbles. The experimental results are compared with scaling predictions. Our findings suggest that the presence of multiple intrusions reduces their spreading rate, compared to that of a single intrusion. This work is of relevance to the spreading of methane plumes issuing from the seabed in the Arctic Ocean, above methane-hydrate deposits. The slower, multiple spreading favours the presence of methane-rich seawater close to the plume, which may reduce the dissolution of methane in the bubbles, and thus promote the direct transport of methane to the atmosphere. This article is part of the theme issue ‘Stokes at 200 (part 2)’.

Mechanisms responsible for the niche shift of brook charr, Salvelinus fontinalis Mitchill, when living sympatrically with creek chub, Semotilus atromaculatus Mitchill

1984 ◽  
Vol 62 (8) ◽  
pp. 1548-1555 ◽  
Author(s):  
Pierre Magnan ◽  
Gérard J. FitzGerald
Keyword(s):  
Laboratory Experiments ◽  
Salvelinus Fontinalis ◽  
Niche Shift ◽  
Intraspecific Aggression ◽  
Brook Charr ◽  
Semotilus Atromaculatus ◽  
High Level ◽  
Gill Raker ◽  
Creek Chub ◽  
Study Laboratory

When brook charr, Salvelinus fontinalis Mitchill, are in allopatry in oligotrophic Québec lakes, they feed largely on macrobenthic invertebrates. However, when brook charr cooccur with creek chub, Semotilus atromaculatus Mitchill, they feed largely on zooplankton. In the present study, laboratory experiments showed that creek chub were more effective than brook charr in searching for hidden, patchily distributed prey. The searching efficiency of an individual chub feeding in a group was improved through social facilitation. In contrast, the high level of intraspecific aggression observed in brook charr prevents the formation of such feeding groups. In the laboratory, brook charr were able to displace creek chub from the food source because of interspecific aggression. Data are presented showing that chub are morphologically better adapted than charr to feed on benthos (subterminal orientation of the mouth and protrusible premaxillae), while the charr are better adapted than chub to feed on zooplankton (gill raker structure). Differences in feeding behaviour, morphology, and relative abundance between these species appear to be important in the observed niche shift of brook charr in nature.

Salinity tolerance of larval and juvenile broad whitefish (Coregonus nasus)

1989 ◽  
Vol 67 (10) ◽  
pp. 2392-2397 ◽  
Author(s):  
B. G. E. de March
Keyword(s):  
Salinity Tolerance ◽  
Species Distribution ◽  
Laboratory Experiments ◽  
Larval Fish ◽  
The Arctic ◽  
Distribution Data ◽  
Migratory Fish ◽  
Limited Information ◽  
Time To Death ◽  
Arctic Coast

In the absence of distribution data for juvenile broad whitefish, Coregonus nasus, laboratory experiments were designed to elucidate the salinity ranges that the species will tolerate. Larval fish (12–18 mm) died within 120 h at salinities of 12.5‰ and higher at both 5 and 10 °C, though more slowly at 5 °C. Salinities of 12.5 and 15‰, but no higher, were tolerated for 120 h at 15 °C. Larvae fed readily at 15 °C but not at 5 or 10 °C. Slightly larger and more-developed larvae (15–19 mm) were tolerant of 12.5‰ but died within 120 h at 15‰ at the same three temperatures. These fish fed more readily than the younger ones. Larger fish (33–68 mm) were generally tolerant of 15–20‰ but not of higher salinities in 120-h tolerance tests. Larger field-collected fish (27–200 mm) reacted similarly but were more tolerant of salinities between 20 and 27‰ in 96-h tests. Analysis of both experiments with larger fish suggests that time to death was inversely related to size as well as to salinity. Coregonus nasus does not seem to be more tolerant of saline conditions than other freshwater or migratory fish species. Experimental results combined with limited information about the species' distribution suggest that man-made constructions on the arctic coast might seriously affect dispersal or annual migrations.

scholarly journals The Collimated Propagation Causes of Astrophysical and Laboratory Jets

2021 ◽  
Vol 65 (6) ◽  
pp. 477-487
Author(s):  
I. Yu. Kalashnikov ◽  
A. V. Dodin ◽  
I. V. Il’ichev ◽  
V. I. Krauz ◽  
V. M. Chechetkin
Keyword(s):  
Laboratory Experiments ◽  
Scaling Laws ◽  
Drift Chamber ◽  
Young Stars ◽  
Point Of View ◽  
Kurchatov Institute ◽  
Environmental Resistance ◽  
Scaling Parameters ◽  
Study Laboratory ◽  
Z Pinch

Abstract The use of Z-pinch facilities makes it possible to carry out well-controlled and diagnosable laboratory experiments to study laboratory jets with scaling parameters close to those of the jets from young stars. This makes it possible to observe processes that are inaccessible to astronomical observations. Such experiments are carried out at the PF-3 facility (“plasma focus,” Kurchatov Institute), in which the emitted plasma emission propagates along the drift chamber through the environment at a distance of one meter. The paper presents the results of experiments with helium, in which a successive release of two ejections was observed. An analysis of these results suggests that after the passage of the first supersonic ejection, a region with a low concentration is formed behind it, the so-called vacuum trace, due to which the subsequent ejection practically does not experience environmental resistance and propagates being collimated. The numerical modeling of the propagation of two ejections presented in the paper confirms this point of view. Using scaling laws and appropriate numerical simulations of astrophysical ejections, it is shown that this effect can also be significant for the jets of young stars.

scholarly journals Spatial Growth of Perturbations in a Turbulent Baroclinic Jet

2011 ◽  
Vol 68 (11) ◽  
pp. 2731-2741
Author(s):  
Rahul B. Mahajan ◽  
Gregory J. Hakim
Keyword(s):  
Prediction Models ◽  
Weather Prediction ◽  
Storm Track ◽  
Spreading Rate ◽  
Forecast Errors ◽  
Far Field ◽  
Quasigeostrophic Model ◽  
Spreading Rates ◽  
Analysis Errors ◽  
Numerical Weather Prediction Models

Abstract The spatial spreading of infinitesimal disturbances superposed on a turbulent baroclinic jet is explored. This configuration is representative of analysis errors in an idealized midlatitude storm track and the insight gained may be helpful to understand the spreading of forecast errors in numerical weather prediction models. This problem is explored through numerical experiments of a turbulent baroclinic jet that is perturbed with spatially localized disturbances. Solutions from a quasigeostrophic model for the disturbance fields are compared with those for a passive tracer to determine whether disturbances propagate faster than the basic-state flow. Results show that the disturbance spreading rate is sensitive to the structure of the initial disturbance. Disturbances that are localized in potential vorticity (PV) have far-field winds that allow the disturbance to travel downstream faster than disturbances that are initially localized in geopotential, which have no far-field wind. Near the jet, the spread of the disturbance field is observed to exceed the tracer field for PV-localized disturbances, but not for the geopotential-localized disturbances. Spreading rates faster than the flow for geopotential-localized disturbances are found to occur only for disturbances located off the jet axis. These results are compared with those for zonal and time-independent jets to qualitatively assess the effects of transience and nonlinearity. This comparison suggests that the average properties of localized perturbations to the turbulent jet can be decomposed into a superposition of dynamics associated with a time-independent parallel flow plus a “diffusion” process.

Effects of Organic Acids on Wettability of Sn-0.3Ag0.7Cu Lead-Free Solder

2014 ◽  
Vol 543-547 ◽  
pp. 3843-3847
Author(s):  
Ming Tang ◽  
Gui Sheng Gan ◽  
Hu Luo ◽  
Shu De Gan ◽  
Qing Meng Wang ◽  
...  
Keyword(s):  
Organic Acid ◽  
Adipic Acid ◽  
Spreading Rate ◽  
Lead Free ◽  
Mass Ratio ◽  
Strong Activity ◽  
Average Spreading ◽  
Free Solder ◽  
Spreading Rates ◽  
Lead Free Solders

In the assembly of electronic products, developing good organic acid fluxes plays an important role in improving the solderability of lead-free solders. In this paper, a variety of fluxes containing 5% (mass fraction) organic acid activators were prepared. Effects of different activators on the spreading rates of Sn-0.3Ag0.7Cu solder were studied. The results show that: activity of monobasic acids are weak except for benzoic acid; dibasic acids and polybasic acids have relatively strong activity but serious corrosion and slightly less activity persistence. Compounding palmitic acid and adipic acid in the mass ratio of 1:2 as the activator, the average spreading rate of Sn-0.3Ag0.7Cu solder is 71.11% in maximum. Compounding succinic acid and adipic acid in the mass ratio of 3:7 as the activator, the average spreading rate is up to 72.49% in maximum. And solder spots are in-erratic, bright and plump, meeting the quality requirements of electronic micro-connection.

Experimental and Numerical Investigations of the 3-D Turbulent Flow Characteristics Around Submerged Permeable Breakwaters

2017 ◽  
Author(s):  
Caleb Stanley ◽  
Georgios Etsias ◽  
Steven Dabelow ◽  
Dimitrios Dermisis ◽  
Ning Zhang
Keyword(s):  
Turbulent Flow ◽  
Laboratory Experiments ◽  
Flow Characteristics ◽  
Mean Flow ◽  
Turbulent Structures ◽  
3 Dimensional ◽  
The Mean ◽  
Design Simplicity ◽  
Study Laboratory ◽  
Geometric Designs

Submerged breakwaters are favored for their design simplicity in projects intended to dissipate wave energy and reduce erosion on coastlines. Despite their popularity, the effects that submerged breakwaters exhibit on the surrounding hydrodynamics are not clearly understood, mainly due to the flow complexity generated from 3-dimensional turbulent structures in the vicinity of the breakwaters that affect the mean flow characteristics and the transport of sediment. The objective of this study was to evaluate the effects that various geometric designs of submerged permeable breakwaters have on the turbulent flow characteristics. To meet the objective of this study, laboratory experiments were performed in a water-recirculating flume, in which the 3-dimensional velocity field was recorded in the vicinity of scaled breakwater models. Breakwaters that were tested include non-permeable, three-hole, and ten-hole models. The experimental data obtained was compared to results obtained from numerical simulations. Results demonstrated that permeable breakwaters exhibit more vertical turbulent strength than their non-permeable counterparts. It was also discovered that three-hole breakwater models produce higher turbulent fluctuations than that of the ten-hole breakwaters. The results from this study will be used eventually to enhance the performance of restoration projects in coastal areas in Louisiana.

Local, Near-Field Mixing Augmentation Using Square Coaxial Jets

2004 ◽  
Author(s):  
Samuel Bonnafous ◽  
Victor Piffaut ◽  
Wai-Ho Choy ◽  
Dimitris E. Nikitopoulos
Keyword(s):  
Near Field ◽  
Internal Flow ◽  
Spreading Rate ◽  
Central Plane ◽  
Mean Velocity ◽  
Mixing Rates ◽  
Spreading Rates ◽  
Diagonal Plane ◽  
Axis Switching ◽  
First Time

Results from un-forced experiments in flows ensuing from circular and equivalent square coaxial nozzles with parallel sides are presented in this paper. The nozzles are contoured and are designed so that the hydraulic diameters of the internal flow passages are identical for both geometries. The flow experiments were conducted at a co-flow-jet Reynolds number of Re = 16,000 and inner-to-outer jet nominal velocity ratios of λ = 0, 0.5, 1.5. Axis switching, a phenomenon readily observed in single non-axisymmetric nozzles, is shown for the first time to occur in the square coaxial nozzles as well. Comparisons of the mixing regions of the flows from both geometries are made to examine mixing advantages when using square nozzle configurations. Comparisons of stream wise mean velocity fields measured on a center plane parallel to the square nozzle sides, on a diagonal plane of the square nozzle and the center plane of the corresponding circular nozzle, are presented and discussed. Axis switching is shown to be evident in the near-field shear regions for all velocity ratios, resulting in considerable mixing advantages. The spreading rates (and therefore mixing rates) of the outer mixing region of the square nozzles clearly exceed the spreading rate observed in the circular case on the central plane. Axis switching and improved mixing is also observed in the inner mixing region of the square nozzle. This work is relevant to coaxial nozzles for gas turbine combustor applications, although the study has been carried out in a scaled up geometry with respect to this application.

scholarly journals EXPERIMENTAL STUDY ON THE EFFECTS OF THE OFFSHORE NOURISHMENT USING THE COASER SANDS WITH THE CROSS-SHORE SEASONAL CHANGE

2012 ◽  
Vol 1 (33) ◽  
pp. 38
Author(s):  
Yoko Shibutani ◽  
Yuhei Matsubara ◽  
Masamitsu Kuroiwa ◽  
Noriko Yao
Keyword(s):  
Experimental Study ◽  
Seasonal Change ◽  
Laboratory Experiments ◽  
Sandy Beach ◽  
Beach Nourishment ◽  
The World ◽  
The Cross ◽  
Sand Nourishment ◽  
Study Laboratory

In recent decades, beach erosions have become severe at sandy beach in the world. The coarser sand nourishment has been noticed in Japan because of the stabilization of the beach coast. However the performance is not clear. Therefore in this study, laboratory experiments were conducted for the beach nourishment using the coarser sand. Through of this experiment, the effect of the coarser sand nourishment was investigated.

scholarly journals Effect of L-shaped slots on scour around a bridge abutment

2021 ◽  
Author(s):  
Neveen Y. Saad ◽  
Ehab M. Fattouh ◽  
M. Mokhtar
Keyword(s):  
Laboratory Experiments ◽  
Vertical Wall ◽  
Clear Water ◽  
Flow Conditions ◽  
Bridge Abutment ◽  
Scour Hole ◽  
Bed Materials ◽  
Bridge Failure ◽  
Study Laboratory ◽  
Area And Volume

Abstract Local scour is the most significant cause of bridge failure. Providing a short abutment with a straight slot has proved to be an effective method for reducing scour at this abutment. In this study, laboratory experiments have been conducted to investigate the effectiveness of using L-shaped slots in comparison to the commonly used straight slot, on the scour reduction at short vertical-wall abutment under clear-water flow conditions and uniform bed materials. The slots were just above the bed and their diameters equal to half the abutment's length. The results illustrated that it is essential to have a straight slot in any combination of slots, as any configuration without one is inefficient. Also, a combination of a straight slot with one side slot in the middle of the abutment's width gives better performance than an individual straight slot, as it reduces the depth, area, and volume of the scour hole by about 32.6, 26.8, and 43.6% respectively, in comparison to 23.2, 20.7, and 35.3% for the straight slot alone.

scholarly journals Shallow free-surface Stokes flow around a corner

2020 ◽  
Vol 378 (2174) ◽  
pp. 20190515 ◽  
Author(s):  
Edward M. Hinton ◽  
Andrew J. Hogg ◽  
Herbert E. Huppert
Keyword(s):  
Free Surface ◽  
Stokes Flow ◽  
Channel Wall ◽  
Laboratory Experiments ◽  
Lateral Spreading ◽  
Simple Expression ◽  
Lava Flows ◽  
Theme Issue ◽  
Inclined Plane ◽  
Downstream Distance

The steady lateral spreading of a free-surface viscous flow down an inclined plane around a vertex from which the channel width increases linearly with downstream distance is investigated analytically, numerically and experimentally. From the vertex the channel wall opens by an angle α to the downslope direction and the viscous fluid spreads laterally along it before detaching. The motion is modelled using lubrication theory and the distance at which the flow detaches is computed as a function of α using analytical and numerical methods. Far downslope after detachment, it is shown that the motion is accurately modelled in terms of a similarity solution. Moreover, the detachment point is well approximated by a simple expression for a broad range of opening angles. The results are corroborated through a series of laboratory experiments and the implication for the design of barriers to divert lava flows are discussed. This article is part of the theme issue ‘Stokes at 200 (Part 1)’.

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