Selective withdrawal and spin-up of a rotating stratified fluid

1989 ◽  
Vol 199 ◽  
pp. 377-401 ◽  
Author(s):  
S. G. Monismith ◽  
T. Maxworthy
Keyword(s):  
Experimental Study ◽  
Velocity Profile ◽  
Side Wall ◽  
Relative Vorticity ◽  
Vertical Profiles ◽  
Selective Withdrawal ◽  
Vertical Diffusion ◽  
Layer Flow ◽  
Rotating Stratified Fluid ◽  
Over Time

We present an experimental study demonstrating that rotation has a pronounced effect on currents induced by selective withdrawal of fluid from a density-stratified reservoir. Our observations show that initiating outflow from the reservoir generates Kelvin shear waves. These waves propagate cyclonically around the perimeter of the reservoir, establishing an anticyclonic withdrawal-layer flow. This flow accelerates owing to the production of relative vorticity by compression of ‘planetary’ vorticity. The withdrawal-layer thickness as shown by vertical profiles of the horizontal velocity grows with time. Separation of the side-wall boundary layers in the corners of the tank causes the spun-up flow to eventually break up into a series of counterrotating gyres. We also present a model that describes many features of the spin-up process observed before onset of separation and subsequent gyre formation. The model shows that vertical diffusion of vorticity plays an important role in the spin up process, leading us to conclude that apparent thickening of the withdrawal layer over time, as seen in changes in the velocity profile, is associated with the vertical diffusion of the spun-up vorticity.

An Experimental Study on the Transport of Sediment in Sewer Pipes with a Permanent Deposit

1992 ◽  
Vol 25 (8) ◽  
pp. 115-122 ◽  
Author(s):  
G. S. Perrusquía
Keyword(s):  
Experimental Study ◽  
Critical Shear Stress ◽  
Side Wall ◽  
Bedload Transport ◽  
Flow Conditions ◽  
Sewer Pipes ◽  
Sediment Bed ◽  
Concrete Pipe ◽  
Geometric Factors ◽  
Particle Parameters

An experimental study of the transport of sediment in a part-full pipe was carried out in a concrete pipe. The experiments were confined to bedload transport. The purpose of this study was to analyze the flow conditions that characterize the stream traction in pipe channels and their relationship to flow resistance and sediment transport rate. Three procedures used in this kind of experimental study were tested and found valid: 1) the vertical velocity distribution near the sediment bed can be described by the velocity-defect law, 2) the side wall elimination procedure can be used to compute the hydraulic radius of the sediment bed, and 3) the critical shear stress of the sediment particles can be obtained by using Shields' diagram. A relationship to estimate bedload transport, based on dimensional analysis, was proposed. This was expressed in terms of both flow and particle parameters as well as geometric factors. Further experimental work is recommended before this relationship can be fully incorporated in a simulation model for the analysis of storm sewers.

scholarly journals Partnership among hospitals to reduce healthcare associated infections: a quasi-experimental study in Brazilian ICUs

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Ladjane Santos Wolmer de Melo ◽  
Maria Verônica Monteiro de Abreu ◽  
Bernuarda Roberta de Oliveira Santos ◽  
Maria das Graças Washington Casimiro Carr ◽  
Maria Fernanda Aparecida Moura de Souza ◽  
...  
Keyword(s):  
Experimental Study ◽  
Length Of Stay ◽  
Public Hospitals ◽  
Incidence Density ◽  
Healthcare Associated Infections ◽  
Collaborative Project ◽  
Quasi Experimental ◽  
Tract Infections ◽  
Healthcare Associated ◽  
Over Time

Abstract Background Healthcare-associated infections (HAIs) are relevant in developing countries where frequencies can be at least 3 times higher than in developed countries. The purpose of this research was to describe the intervention implemented in intensive care units (ICUs) to reduce HAIs through collaborative project and analyze the variation over 18 months in the incidence density (ID) of the three main HAIs: ventilator associated pneumonia (VAP), central line-associated bloodstream infections (CLABSIs) and catheter-related urinary tract infections (CAUTIs) and also the length of stay and mortality in these ICUs. Methods A quasi-experimental study in five public adult clinical-surgical ICUs, to reduce HAIs, through interventions using the BTS-IHI “Improvement Model”, during 18 months. In the project, promoted by the Ministry of Health, Brazilian philanthropic hospitals certified for excellence (HE), those mostly private, certified as excellence and exempt from security contributions, regularly trained and monitored public hospitals in diagnostics, data collection and in developing cycles to improve quality and to prevent HAIs (bundles). In the analysis regarding the length of stay, mortality, the IDs of VAP, CLABSIs and CAUTIs over time, a Generalized Estimating Equation (GEE) model was applied for continuous variables, using the constant correlation (exchangeable) between assessments over time. The model estimated the average difference (β coefficient of the model) of the measures analyzed during two periods: a period in the year 2017 (prior to implementing the project) and in the years 2018 and 2019 (during the project). Result A mean monthly reduction of 0.427 in VAP ID (p = 0.002) with 33.8% decrease at the end of the period and 0.351 in CAUTI ID (p = 0.009) with 45% final decrease. The mean monthly reduction of 0.252 for CLABSIs was not significant (p = 0.068). Length of stay and mortality rates had no significant variation. Conclusions Given the success in reducing VAP and CAUTIs in a few months of interventions, the achievement of the collaborative project is evident. This partnership among public hospitals/HE may be applied to other ICUs including countries with fewer resources.

An Experimental Study of Cache Recovery By Hoarding Willow Tits After Different Retention Intervals

Behaviour ◽  
1997 ◽  
Vol 134 (11-12) ◽  
pp. 881-890 ◽  
Author(s):  
Camilla Kunz ◽  
Anders Brodin
Keyword(s):  
Experimental Study ◽  
Parus Montanus ◽  
Individual Preferences ◽  
Cache Recovery ◽  
Retention Intervals ◽  
Over Time ◽  
Better Than

AbstractWe allowed seven willow tits, Parus montanus, to store and retrieve with retention intervals of 1, 7, 21 and 56 days, in four experimental rooms. Retrieval success decreased over time, indicating a decaying memory for cache locations. Compared to what could be expected by chance, retrieval success was better after all retention intervals. Our results suggest that - after the longer retention intervals - this might depend on preferences for certain types of caching locations rather than memory. If both general and individual preferences are controlled for, birds retrieved significantly better than expected one and seven days after storing, but not later than that.

An Experimental Study of Nonequilibrium Carbon Dioxide/Oil Interactions

SPE Journal ◽  
2018 ◽  
Vol 23 (05) ◽  
pp. 1768-1783 ◽  
Author(s):  
Mahmood Reza Yassin ◽  
Ali Habibi ◽  
Ashkan Zolfaghari ◽  
Sara Eghbali ◽  
Hassan Dehghanpour
Keyword(s):  
Carbon Dioxide ◽  
Experimental Study ◽  
Natural Convection ◽  
Visual Cell ◽  
Bulk Oil ◽  
High Pressure High Temperature ◽  
Light Oil ◽  
Condensing Flows ◽  
Carbon Dioxide Co2 ◽  
Over Time

Summary In this study, we use a custom-designed visual cell to investigate nonequilibrium carbon dioxide (CO2)/oil interactions under high-pressure/high-temperature conditions. We visualize the CO2/oil interface and measure the visual-cell pressure over time. We perform five sets of visualization tests. The first three tests aim at investigating interactions of gaseous (g), liquid (l), and supercritical (sc) CO2 with a Montney (MTN) oil sample. In the fourth test, to visualize the interactions in the bulk oil phase, we replace the opaque MTN oil with a translucent Duvernay (DUV) light oil (LO). Finally, we conduct an N2(sc)/oil test to compare the results with those of CO2(sc)/oil test. We also compare the results of nonequilibrium CO2/oil interactions with those obtained from conventional pressure/volume/temperature (PVT) tests. Results of the first three tests show that oil immediately expands upon injection of CO2 into the visual cell. CO2(sc) leads to the maximum oil expansion followed by CO2(l) and CO2(g). Furthermore, the rate of oil expansion in the CO2(sc)/oil test is higher than that in CO2(l)/oil and CO2(g)/oil tests. We also observe extracting and condensing flows at the CO2(l)/oil and CO2(sc)/oil interfaces. Moreover, we observe density-driven fingers inside the LO phase because of the local increase in the density of LO. The results of PVT tests show that the density of the CO2/oil mixture is higher than that of the CO2-free oil, explaining the density-driven natural convection during CO2(sc) injection into the visual cell. We do not observe either extracting/condensing flows or density-driven mixing for the N2(sc)/oil test, explaining the low expansion of oil in this test. The results suggest that the combination of density-driven natural convection and extracting/condensing flows enhances CO2(sc) dissolution into the oil phase, leading to fast oil expansion after CO2(sc) injection into the visual cell.

Really Rewarding Rewards: Strategic Licensing in Long-Term Healthy Food Consumption

2021 ◽  
Author(s):  
Rishika Rishika ◽  
Sven Feurer ◽  
Kelly L Haws
Keyword(s):  
Decision Making ◽  
Experimental Study ◽  
Consumption Patterns ◽  
Driving Mechanism ◽  
Policy Makers ◽  
Calorie Consumption ◽  
Food Purchases ◽  
Related Aspect ◽  
Over Time

Abstract Licensing is a well-documented form of justifying individual indulgent choices, but less is known about how licensing affects food decision-making patterns over time. Accordingly, we examine whether consumers incorporate licensing strategically and deliberately in their long-term consumption patterns and identify reward programs as a context in which strategic licensing is likely to occur. We propose that members with lower-calorie consumption patterns strategically indulge more on reward purchase occasions, and that forethought is required for such an effect to occur. A longitudinal study analyzing 272,677 real food purchases made by 7,828 consumers over a 14-month period provides striking evidence of our key proposition. An exploration of the inter-purchase time-related aspect of purchase acceleration suggests that forethought on behalf of consumers is necessary for strategic licensing to occur. A subsequent experimental study (N = 605) comprising five consecutive choice occasions provides additional evidence of forethought by demonstrating that strategic licensing occurs only when expected (but not windfall reward) occasions are involved, and by showing that anticipated negative affect for not indulging is the driving mechanism. We conclude with a discussion of the implications of our results for consumers, managers, and public policy makers.

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