Experiments on filtration in plankton nets

1967 ◽  
Vol 18 (1) ◽  
pp. 89 ◽  
Author(s):  
DJ Tranter ◽  
AC Heron
Keyword(s):  
Water Column ◽  
Flow Patterns ◽  
Filtration Efficiency ◽  
Wind Tunnels ◽  
Gradual Decline ◽  
Test Tank ◽  
Suitable Site ◽  
Made In

Experiments were carried out in wind tunnels, in a test tank, and at sea, to investigate the interaction between the water column and a towed plankton net. Flow patterns about stationary nets held in a stream of air were observed and photographed. The velocity and turbulence of the stream near the net, and the drag upon the net, were measured. Experimental tows were made in the laboratory and in the field to test the effect of various factors on "filtration efficiency". This interaction between the discharge and the flow around the net leads to enhanced filtration. The effect is accentuated by a flared mouth which increases the velocity differential. The effect is reduced by encasing the net, which separates the interacting streams and probably causes the stream from the net surface to lose momentum. Filtration efficiency is independent of towing velocity, except for a gradual decline at velocities less than 1-2 kt. Filtration efficiency is also independent of filtering area in nets of usual length, but declines sharply in nets shorter than twice their mouth diameter. There is a zone of turbulence and reduced velocity in the centre of a net with bridles. At approximately one-quarter of a radius from the ring, the stream is flowing at mean mouth velocity. This seems to be the most suitable site for a flowmeter.

Trophic group and the end-Cretaceous extinction: did deposit feeders have it made in the shade?

Paleobiology ◽  
1996 ◽  
Vol 22 (1) ◽  
pp. 104-112 ◽  
Author(s):  
Jeffrey S. Levinton
Keyword(s):  
Water Column ◽  
Deep Sea ◽  
Trophic Group ◽  
Food Shortage ◽  
Suspension Feeders ◽  
Deposit Feeders ◽  
Relative Ability ◽  
Organic Particles ◽  
Cretaceous Period ◽  
Made In

It has been suggested that a sudden event at the end of the Cretaceous period caused a major extinction that was felt disproportionately by creatures in the water column. It also has been argued that benthic deposit feeders, being relatively independent of abundance of organic particles in the water column, should have survived the crisis more readily than suspension feeders, which depended more upon feeding upon phytoplankton. I argue that the hypothesis of relative immunity of deposit feeders is insufficient, because deposit feeders by and large depend upon a supply of organic matter from the water column and would have succumbed to food shortage nearly as rapidly as suspension feeders, possibly within a maximum of three to six months. This near simultaneity of extinction would have been especially true of continental shelf environments. Even in some parts of the deep sea, it is likely that a dependence upon the water column above might have caused deep-sea deposit feeders to succumb rapidly. Therefore, deposit feeders would not necessarily have outsurvived suspension feeders during a crisis of depleted water-column phytoplankton, increased shading by inert particles, or poisoning of the water column and killing of phytoplankton. The relatively lower rate of extinction of nuculoid bivalves may relate instead to their presence in deeper-water refuge habitats, their apparent relative ability to diversify in higher latitudes, or their resistance to factors other than food shortage.

scholarly journals Optical Fibre Aerodynamic Probes for Total Pressure and Total Temperature Measurement in Turbomachinery

1999 ◽  
Author(s):  
J. S. Barton ◽  
J. M. Kilpatrick ◽  
W. N. MacPherson ◽  
J. D. C. Jones ◽  
K. S. Chana ◽  
...  
Keyword(s):  
Optical Fibre ◽  
Total Pressure ◽  
Pressure Sensors ◽  
Wind Tunnels ◽  
Temperature Dependent ◽  
Flow Measurements ◽  
Optical Fibre Sensors ◽  
Total Temperature ◽  
Harmonic Components ◽  
Made In

Optical fibre sensors offer the prospect of miniature aerodynamic probes for highly localised flow measurements in aerospace wind tunnels and turbomachines. We discuss the design and construction of optical fibre sensors for temperature and pressure. The temperature sensors consist of multilayer coatings deposited on the fibre end face from which the reflected intensity is temperature-dependent. Two sensors were incorporated in a dual heated probe to measure total temperature. The pressure sensors are miniature diaphragms in which pressure-induced deflection is measured interferometrically in reflection. We present results from initial trials made in unsteady flow in a single stage research turbine, in which total temperature data with harmonic components up to 30 kHz and total pressure signals up to 230 kHz were recorded.

THE FATE OF SALMONELLA TYPHIMURIUM IN THE MANUFACTURE AND RIPENING OF LOW-ACID CHEDDAR CHEESE1

1970 ◽  
Vol 33 (7) ◽  
pp. 280-284 ◽  
Author(s):  
H. S. Park ◽  
E. H. Marth ◽  
J. M. Goepfert ◽  
N. F. Olson
Keyword(s):  
Salmonella Typhimurium ◽  
Starter Culture ◽  
Most Probable Number ◽  
Initial Increase ◽  
High Moisture ◽  
Gradual Decline ◽  
Probable Number ◽  
Streptococcus Lactis ◽  
Extended Survival ◽  
Made In

Cheddar cheese was made by the stirred-curd procedure from pasteurized milk inoculated with Salmonellea typhimurium and with a slow acid-producing strain of Streptococcus lactis. The Most Probable Number technique was used to enumerate salmonellae in milk and in cheese during its manufacture and ripening. Salmonellae grew rapidly during manufacture and limited additional growth occurred in cheese during the first week of ripening at 13 C after which there was a gradual decline in population. Salmonellae survived during ripening for up to approximately 7 months at 13 C and 10 months at 7 C. Cheese made in 2 of 5 trials exhibited a limited increase in number of salmonellae during the first 2 weeks at 7 C followed by a decline in population of these bacteria. Other cheeses held at 7 C exhibited a reduction in number of viable salmonellae without the initial increase. Growth of salmonellae during the early stages of ripening and subsequent extended survival of these organisms may, in part, be attributable to high moisture (average 43.2%) and high pH (5.75 after overnight pressing) of the cheese which resulted from use of a slow acid-producing starter culture.

Dissolved gases in perennially ice-covered lakes of the McMurdo Dry Valleys, Antarctica

1998 ◽  
Vol 10 (2) ◽  
pp. 124-133 ◽  
Author(s):  
D.T. Andersen ◽  
C.P. Mckay ◽  
R.A. Wharton
Keyword(s):  
Water Column ◽  
Turbulent Mixing ◽  
Bubble Formation ◽  
Gas Content ◽  
Main Process ◽  
Water Interface ◽  
Dry Valleys ◽  
The Mean ◽  
Ice Water ◽  
Made In

Measurements of dissolved N2, O2, Ar, CO2, and CH4 were made in perennially ice-covered Lake Hoare. Results confirm previous reports that O2 concentrations in the upper water column exceed atmospheric equilibrium and that N2 and Ar are supersaturated throughout the water column. The mean supersaturation of N2 was found to be 2.0 (±0.37) and Ar was 3.8 (±1.1). The ratios of N2/Ar (20.3 ±3.8), and O2/Ar (22.5 ±4.0) at the ice-water interface are consistent with those previously measured, suggesting that bubble formation is the main process for removing gas from the lake. However, the saturations of N2 and Ar greatly exceed those previously predicted for degassing by bubble formation only at the ice-water interface. The data support the hypothesis that removal of gas by bubbles occurs in the water column to a depth of 11 m in Lake Hoare. CO2 concentration increases from near zero at the ice-water interface to 80–100 times saturation at and below the chemocline at c. 28 m. There is considerable variability in the gas concentrations throughout the water column; samples separated in depth by one metre may vary by more than 50% in gas content. It is likely that this phenomenon results from the lack of turbulent mixing in the water column. Methane (c. 2 μg 1−1) was detected below the chemocline and immediately above the sediment/water interface at a depth of 30 m. Samples from lakes Vanda, Joyce, and Miers, also show supersaturations of O2, N2, and Ar at levels similar to levels found in Lake Hoare.

Customized Profiles — The Beginning of an Era: A Short History of Blade Design

2004 ◽  
Author(s):  
Hanns-Juergen Lichtfuss
Keyword(s):  
Numerical Methods ◽  
Laminar Flow ◽  
Wind Tunnels ◽  
Blade Design ◽  
Design Strategies ◽  
Short History ◽  
Compressor Blades ◽  
History Of ◽  
Electronic Computers ◽  
Made In

The paper presents the evolutionary progress made in the design process of turbo machines from using standardized profiles — for turbine and compressor blades — towards individual profile designs. The emerging new power of numerical methods on continuously faster running electronic computers has made this progress possible. In addition there were regularly experimental verifications in cascade wind tunnels and turbo machinery test beds as well as applications of new design strategies. These strategies, i.e. naturally laminar flow in turbines and supercritical flow in compressors, also made use of reinvented inverse methods, as one tool to optimise problematic areas.

Survey of Portable Oil Detection Methods

2014 ◽  
Vol 2014 (1) ◽  
pp. 299894 ◽  
Author(s):  
Mike Goldthorp* ◽  
Patrick Lambert ◽  
Carl Brown
Keyword(s):  
Water Column ◽  
Detection Methods ◽  
Relative Cost ◽  
Oil In Water ◽  
Primary Focus ◽  
A Site ◽  
Multiple Samples ◽  
Spilled Oil ◽  
Made In

When oil is spilled into the marine environment, it may be found on the water's surface, in the water column, in the sediment, or on the shoreline. When delineating the extent of contamination, it is important to be able to differentiate the spilled oil from other components that may appear to be oil. There are established methods for detecting oil-in-water, such as fluorometry, that allow in situ measurements to be made. In this study, we investigate both established methods and potential technological advancements that could provide a means for a site investigator to gather meaningful on-site information regarding the presence of oil. The primary focus will be usefulness to a shoreline application, but application to other types of samples is addressed. The degree to which an oil could be identified using these portable methods, such as the ability to differentiate petrogenic from biogenic oils, is also discussed. Method comparisons are discussed, with relevance to portability, selectivity, relative cost, and ability to process multiple samples.

scholarly journals Stabilizing Hydrographic Profiles with Minimal Change to the Water Masses

2017 ◽  
Vol 34 (9) ◽  
pp. 1935-1945 ◽  
Author(s):  
Paul M. Barker ◽  
Trevor J. McDougall
Keyword(s):  
Water Column ◽  
Water Mass ◽  
Minimal Change ◽  
Water Masses ◽  
Oceanographic Data ◽  
Made In

AbstractBoth observed and averaged oceanographic data often contain regions with density inversions. This paper presents two methods of stabilizing a water column. The first method is intended for use with observed data; it minimally adjusts Absolute Salinity while leaving the values of in situ temperature unchanged. The second method adjusts the values of both Absolute Salinity and Conservative Temperature, and these adjustments are made in such a way as to cause the least possible damage to the water-mass structure of the vertical cast.

Epilimnetic and Metalimnetic Primary Production in an Indiana Hardwater Lake

1983 ◽  
Vol 40 (6) ◽  
pp. 792-798 ◽  
Author(s):  
Allan Konopka
Keyword(s):  
Numerical Model ◽  
Solar Radiation ◽  
Vertical Distribution ◽  
Primary Production ◽  
Water Column ◽  
Primary Productivity ◽  
Water Transparency ◽  
Incident Solar Radiation ◽  
The Vertical Distribution ◽  
Made In

Primary productivity in an Indiana lake, which contained a metalimnetic layer of cyanobacteria, was calculated for the summers of 1979–81 by using a numerical model. Production estimates of 183 and 187 g C∙m−2 were obtained for 1979 and 1980; the estimate for 1981 was 50% higher. These values were two- to four-fold higher than estimates made in 1963 and 1964. Production in the metalimnion accounted for 29, 44, and 34% of the total during the three summers. Changes in the vertical distribution of biomass in the water column appeared to have had a greater effect upon metalimnetic production than differences in water transparency or incident solar radiation. The average values measured for the latter two variables were reasonably similar during the 3 yr, whereas the depth at which the metalimnetic layer of cyanobacteria stratified decreased from 9 m in 1979 to 5 m in 1981.

The necessity for boundary corrections in a standard practice for the open-jet wind tunnel testing of automobiles

2017 ◽  
Vol 231 (9) ◽  
pp. 1245-1273 ◽  
Author(s):  
Kevin R Cooper ◽  
Edzard Mercker ◽  
Jürg Müller
Keyword(s):  
Wind Tunnel ◽  
Drag Coefficient ◽  
Wind Tunnels ◽  
Wind Tunnel Testing ◽  
High Quality ◽  
Wind Tunnel Measurement ◽  
Wind Tunnel Measurements ◽  
Selected Subset ◽  
Open Road ◽  
Made In

This paper is intended to provide a summary of the necessary adjustments required for road-representative open-jet wind tunnel measurements on automobiles. The open-jet wind tunnel provides accurate measurements, but they are made in a finite-sized jet that differs from the unconfined open-road conditions. Furthermore, measurements on a given automobile made in different open-jet wind tunnels disagree with each other, and with measurements in closed-wall wind tunnels that were corrected for the influences of their solid boundaries. There appears to be reticence at some company levels to making ‘corrections’ to open-jet measurements. Perhaps non-specialist managers think that the need for a ‘correction’ means an erroneous measurement. It does not! Any high-quality wind tunnel measurement is accurate, but it needs to be ‘calibrated’ to on-road conditions through an appropriate set of procedures. Closed-wall wind tunnels measure higher drag coefficients, in comparison with those in an unconstrained on-road flow. Open-jet wind tunnels frequently measure a lower value. The closed-wall adjustments lower the drag coefficient to the unconstrained value. Open-jet adjustments should also adjust the drag coefficient to the same unconstrained value. This paper explores the range of effects from the finite jet and elucidates the effectiveness of a two-measurement correction procedure. It is shown that not every data point must be measured twice, only a small selected subset. Since approximately 20% of tunnel occupancy is in the fan-on condition, then the additional cost of correct accurate on-road-equivalent data is low.

Atomic recombination in a hypersonic wind-tunnel nozzle

1959 ◽  
Vol 6 (1) ◽  
pp. 1-32 ◽  
Author(s):  
K. N. C. Bray
Keyword(s):  
Shock Wave ◽  
Rate Constant ◽  
Chemical Equilibrium ◽  
Wind Tunnels ◽  
Hypersonic Wind Tunnel ◽  
Constant Area ◽  
Wide Range ◽  
Method Of Solution ◽  
Range Of Values ◽  
Made In

The flow of an ideal dissociating gas through a nearly conical nozzle is considered. The equations of one-dimensional motion are solved numerically assuming a simple rate equation together with a number of different values for the rate constant. These calculations suggest that deviations from chemical equilibrium will occur in the nozzle if the rate constant lies within a very wide range of values, and that, once such a deviation has begun, the gas will very rapidly ’freeze’. The dissociation fraction will then remain almost constant if the flow is expanded further, or even if it passes through a constant area section. An approximate method of solution, making use of this property of sudden ’freezing’ of the flow, has been developed and applied to the problem of estimating the deviations from equilibrium under a wide range of conditions. If all the assumptions made in this paper are accepted, then lack of chemical equilibrium may be expected in the working sections of hypersonic wind tunnels and shock tubes. The shape of an optimum nozzle is derived in order to minimize this departure from equilibrium.It is shown that, while the test section conditions are greatly affected by ’freezing’, the flow behind a normal shock wave is only changed slightly. The heat transfer rate and drag of a blunt body are estimated to be reduced by only about 25% even if complete freezing occurs. However, the shock wave shape is shown to be rather more sensitive to departures from equilibrium.

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