scholarly journals A Laboratory Study of Iceberg Side Melting in Vertically Sheared Flows

2018 ◽  
Vol 48 (6) ◽  
pp. 1367-1373 ◽  
Author(s):  
A. FitzMaurice ◽  
C. Cenedese ◽  
F. Straneo
Keyword(s):  
Velocity Profile ◽  
Laboratory Study ◽  
Flow Speed ◽  
Vertical Shear ◽  
Nonlinear Dependence ◽  
Laboratory Setting ◽  
Sheared Flow ◽  
Ice Surface ◽  
Flow Splitting ◽  
Observational Record

AbstractAn earlier study indicates that the side melting of icebergs subject to vertically homogeneous horizontal velocities is controlled by two distinct regimes, which depend on the melt plume behavior and produce a nonlinear dependence of side melt rate on velocity. Here, we extend this study to consider ice blocks melting in a two-layer vertically sheared flow in a laboratory setting. It is found that the use of the vertically averaged flow speed in current melt parameterizations gives an underestimate of the submarine side melt rate, in part because of the nonlinearity of the dependence of the side melt rate on flow speed but also because vertical shear in the horizontal velocity profile fundamentally changes the flow splitting around the ice block and consequently the velocity felt by the ice surface. An observational record of 90 icebergs in a Greenland fjord suggests that this effect could produce an average underestimate of iceberg side melt rates of 21%.

Polygraph Lie Detection on Real Events in a Laboratory Setting

1993 ◽  
Vol 76 (3) ◽  
pp. 1051-1058 ◽  
Author(s):  
M. T. Bradley ◽  
M. C. Cullen
Keyword(s):  
Laboratory Study ◽  
Real Life ◽  
Lie Detection ◽  
Laboratory Setting ◽  
Control Question ◽  
Polygraph Testing ◽  
Emotional Events

This laboratory study dealt with real-life intense emotional events. Subjects generated embarrassing stories from their experience, then submitted to polygraph testing and, by lying, denied their stories and, by telling the truth, denied a randomly assigned story. Money was given as an incentive to be judged innocent on each story. An interrogator, blind to the stories, used Control Question Tests and found subjects more deceptive when lying than when truthful. Stories interacted with order such that lying on the second story was more easily detected than lying on the first. Embarrassing stories provide an alternative to the use of mock crimes to study lie detection in the laboratory.

Vortex-Induced Vibration and Drag Coefficients of Long Cables Subjected to Sheared Flows

1986 ◽  
Vol 108 (1) ◽  
pp. 77-83 ◽  
Author(s):  
Y.-H. Kim ◽  
J. K. Vandiver ◽  
R. Holler
Keyword(s):  
Field Experiments ◽  
Broad Band ◽  
Single Mode ◽  
Response Spectra ◽  
Flow Speed ◽  
Current Profile ◽  
Vortex Induced Vibration ◽  
Sheared Flow ◽  
Typical Experiment ◽  
Lock In

The vortex-induced vibration response of long cables subjected to vertically sheared flow was investigated in two field experiments. In a typical experiment, a weight was hung over the side of the research vessel by a cable that was instrumented with accelerometers. A typical experiment measured the acceleration response of the cable, the current profile, the tension, and angle of inclination at the top of the cable. Total drag force was computed from the tension and angle measurements. Two braided Kevlar cables were tested at various lengths from 100 to 9,050 ft. As a result of these experiments, several important conclusions can be drawn: (i) the wave propagation along the length of the cable was damped, and therefore, under most conditions the cable behaved like an infinite string; (ii) response spectra were quite broad-band, with center frequencies determined by the flow speed in the region of the accelerometer; (iii) single mode lock-in was not observed for long cables in the sheared current profile; (iv) the average drag coefficient of long cables subjected to sheared flow was considerably lower than observed on short cables in uniform flows; (v) the r.m.s. response was higher in regions of higher current speed. A new dimensionless parameter is proposed that incorporates the properties of the cable as well as the sheared flow. This parameter is useful in establishing the likelihood that lock-in may occur, as well as in estimating the number of modes likely to respond.

Life of a Six-Hour Hurricane

2009 ◽  
Vol 137 (1) ◽  
pp. 51-67 ◽  
Author(s):  
Kay L. Shelton ◽  
John Molinari
Keyword(s):  
Deep Convection ◽  
Potential Temperature ◽  
Vertical Wind Shear ◽  
Lower Troposphere ◽  
Vertical Shear ◽  
Vortex Center ◽  
Dry Air ◽  
Sheared Flow ◽  
The Core ◽  
Equivalent Potential

Abstract Hurricane Claudette developed from a weak vortex in 6 h as deep convection shifted from downshear into the vortex center, despite ambient vertical wind shear exceeding 10 m s−1. Six hours later it weakened to a tropical storm, and 12 h after the hurricane stage a circulation center could not be found at 850 hPa by aircraft reconnaissance. At hurricane strength the vortex contained classic structure seen in intensifying hurricanes, with the exception of 7°–12°C dewpoint depressions in the lower troposphere upshear of the center. These extended from the 100-km radius to immediately adjacent to the eyewall, where equivalent potential temperature gradients reached 6 K km−1. The dry air was not present prior to intensification, suggesting that it was associated with vertical shear–induced subsidence upshear of the developing storm. It is argued that weakening of the vortex was driven by cooling associated with the mixing of dry air into the core, and subsequent evaporation and cold downdrafts. Evidence suggests that this mixing might have been enhanced by eyewall instabilities after the period of rapid deepening. The existence of a fragile, small, but genuinely hurricane-strength vortex at the surface for 6 h presents difficult problems for forecasters. Such a “temporary hurricane” in strongly sheared flow might require a different warning protocol than longer-lasting hurricane vortices in weaker shear.

scholarly journals Detailed dynamic, geometric and supraglacial moraine data for Glaciar Pio XI, the only surge-type glacier of the Southern Patagonia Icefield

2016 ◽  
Vol 57 (73) ◽  
pp. 119-130 ◽  
Author(s):  
Ryan Wilson ◽  
Daniela Carrión ◽  
Andrés Rivera
Keyword(s):  
General Trend ◽  
Maximum Velocity ◽  
Flow Speed ◽  
Flow Path ◽  
Primary Flow ◽  
Ice Flow ◽  
Synoptic Analysis ◽  
Ice Surface ◽  
Southern Patagonia ◽  
Geospatial Datasets

ABSTRACTIn contrast to the general trend for glaciers of the Southern Patagonia Icefield, Glaciar Pio XI has experienced a large cumulative frontal advance since 1945. In an effort to better understand this advancing behaviour, this paper presents a synoptic analysis of frontal fluctuations (1998–2014), ice velocities (1986–2014), ice-surface elevations (1975–2007) and supraglacial moraines (1945–2014) derived from geospatial datasets. These analyses reveal changes in the ice flow of Glaciar Pio XI's freshwater calving northern terminus and tidewater calving southern terminus over recent decades. Between 1986 and 2000, ice flow speed generally accelerated reaching peaks of >15 m d−1 at the frontal edge of the southern terminus. Following this period, flow speed decreased, reducing to <1 m d−1 for the central part of the southern terminus in 2014, despite advancing to a neoglacial maximum. From 2000 to 2014 the reduction in speed was accompanied by a shift in maximum velocity away from the southern terminus, towards the central glacier trunk. As a result, the northern terminus, which accelerated during this period, represented the new primary flow path in 2014. Notably, the moraine maps presented highlight surges occurring around 1981 and again between 1997 and 2000, marked by arcuate moraine features on the southern terminus.

Estimation of surface flow speed and ice surface temperature from optical satellite imagery at Viedma glacier, Argentina

2018 ◽  
Vol 169 ◽  
pp. 202-213 ◽  
Author(s):  
A. Lo Vecchio ◽  
M.G. Lenzano ◽  
M. Durand ◽  
E. Lannutti ◽  
R. Bruce ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Satellite Imagery ◽  
Flow Speed ◽  
Surface Flow ◽  
Ice Surface ◽  
Ice Surface Temperature

scholarly journals Strain in the ice sheet deduced from the crystal-orientation fabrics from bare icefields adjacent to the Sør-Rondane Mountains, Dronning Maud Land, East Antarctica

1994 ◽  
Vol 40 (134) ◽  
pp. 135-139 ◽  
Author(s):  
S. Fujita ◽  
S. Mae
Keyword(s):  
Shear Strain ◽  
Crystal Orientation ◽  
Horizontal Plane ◽  
Flow Line ◽  
Ice Sheet ◽  
Vertical Shear ◽  
Surface Cracks ◽  
Ice Flow ◽  
Ice Surface ◽  
Dronning Maud Land

AbstractStructural analyses of ice collected from the bare ice surface in the region of the Sør-Rondane Mountains were carried out. Crystal-orientation fabrics and the disposition of surface cracks were investigated to determine the stress/strain configuration in the ice sheet near the mountains. Single-maximum fabric patterns with the axis of the maximum roughly perpendicular to the flow line on the horizontal plane were observed. It was deduced from the observations that the ice exhibits a fabric pattern indicating that the ice sheet is subjected to vertical shear strain between the ice flow and the nunataks.

An experimental investigation of pulsating turbulent water flow in a tube

1971 ◽  
Vol 46 (1) ◽  
pp. 43-64 ◽  
Author(s):  
J. H. Gerrard
Keyword(s):  
Reynolds Number ◽  
Velocity Profile ◽  
Water Flow ◽  
Cylindrical Tube ◽  
Flow Speed ◽  
Mean Flow ◽  
Mean Velocity ◽  
Central Plateau ◽  
Transition Range ◽  
The Mean

Experiments were made on a pulsating water flow at a mean flow Reynolds number of 3770 in a cylindrical tube of diameter 3·81 cm. Pulsations were produced by a piston oscillating in simple harmonic motion with a period of 12 s. Turbulence was made visible by means of a sheet of dye produced by electrolysis from a fine wire stretched across a diameter. The sheet of dye is contorted by the turbulent eddies, and ciné-photography was used to find the velocity of convection which was shown to be the flow speed except in certain circumstances which are discussed. By subtracting the mean flow velocity profile the profile of the component of the motion oscillating at the imposed frequency was determined.The Reynolds number of these experiments lies in the turbulent transition range, so that large effects of laminarization are observed. In the turbulent phase, the velocity profile was found to possess a central plateau as does the laminar oscillating profile. The level and radial extent of this were little different from the laminar ones. Near to the wall, the turbulent oscillating profile is well represented by the mean velocity power law relationship, u/U ∝ (y/a)1/n. In the laminarized phase, the turbulent intensity is considerably reduced at this Reynolds number. The velocity profile for the whole flow (mean plus oscillating) relaxes towards the laminar profile. Laminarization contributes appreciably to the oscillating component.Extrapolation of the results to higher Reynolds numbers and different frequencies of oscillation is suggested.

Hydraulic control of homogeneous shear flows

2003 ◽  
Vol 475 ◽  
pp. 163-172 ◽  
Author(s):  
CHRIS GARRETT ◽  
FRANK GERDES
Keyword(s):  
Shear Flow ◽  
Velocity Profile ◽  
Water Waves ◽  
Flow Speed ◽  
Hydraulic Control ◽  
Mean Flow ◽  
Shallow Water Waves ◽  
Homogeneous Fluid ◽  
Apparent Paradox ◽  
The Mean

If a shear flow of a homogeneous fluid preserves the shape of its velocity profile, a standard formula for the condition for hydraulic control suggests that this is achieved when the depth-averaged flow speed is less than (gh)1/2. On the other hand, shallow-water waves have a speed relative to the mean flow of more than (gh)1/2, suggesting that information could propagate upstream. This apparent paradox is resolved by showing that the internal stress required to maintain a constant velocity profile depends on flow derivatives along the channel, thus altering the wave speed without introducing damping. By contrast, an inviscid shear flow does not maintain the same profile shape, but it can be shown that long waves are stationary at a position of hydraulic control.

Influence of a Varying Vertical Velocity Profile on Turbine Efficiency for a Vertical Axis Marine Current Turbine

2009 ◽  
Author(s):  
Anders Goude ◽  
Emilia Lalander ◽  
Mats Leijon
Keyword(s):  
Velocity Profile ◽  
Vertical Velocity ◽  
Energy Resource ◽  
Vertical Axis ◽  
Vertical Shear ◽  
Power Coefficient ◽  
Turbine Efficiency ◽  
Marine Current ◽  
Vertical Velocity Profile ◽  
The Difference

Water currents in e.g. unregulated rivers and tides are a considerable renewable energy resource. The technology needed to harness the energy in these streams has not yet matured, but research and development are ongoing. In the present paper the power coefficient of marine current turbines using vertical axis turbines is considered. When the width and height of the turbine are kept constant, the Cp-λ curve will depend mainly on the solidity. However, since all natural channels have vertical velocity variations due to friction against the sea floor, this will also affect the efficiency. The double multiple streamtube model was used to study the power coefficient as a function of solidity and vertical shear profile. Three turbine cases were studied: one turbine vertically aligned, and two horizontally aligned turbines rotating with opposite direction. The results show that the difference depends both on how much the velocity varies over the velocity profile, and on the shape of the velocity profile, where a linear profile causes a lower Cp compared to a logarithmic profile. The difference was especially prominent at low tip speed ratios for the horizontally aligned turbines with different rotational direction.

Questing behavior of adult Amblyomma americanum (L.) in a laboratory setting

2021 ◽  
Author(s):  
Miranda Huang ◽  
Abby Jones ◽  
Afsoon Sabet ◽  
Jillian Masters ◽  
Natalie Dearing ◽  
...  
Keyword(s):  
Vector Control ◽  
Laboratory Study ◽  
Time Of Day ◽  
Amblyomma Americanum ◽  
Strong Preference ◽  
Head Orientation ◽  
Laboratory Setting ◽  
Stem Type

Tick-borne diseases are on the rise globally; however, information is lacking about tick questing behavior. In this laboratory study, we explored tick preferences for stem type (plastic grass, wooden, and metal), questing height, and head orientation. Using 60 Amblyomma americanum adults over three 72-hour replicates, we determined that 21.7% of ticks quested at any given time and that ticks exhibited a strong preference to quest with their heads oriented downwards, irrespective of stem type. Individual ticks tended to quest on only one stem in this study, and a maximum of three. Nonetheless, ticks appeared to prefer questing on wooden and plastic grass stems over metal stems. We did not find an effect of time of day on tick questing rates. Increased understanding of tick questing behavior can improve vector control efforts.  

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