scholarly journals High-resolution variations in size, number and arrangement of air bubbles in the EPICA DML (Antarctica) ice core

2013 ◽  
Vol 59 (217) ◽  
pp. 972-980 ◽  
Author(s):  
Verena Bendel ◽  
Kai J. Ueltzhöffer ◽  
Johannes Freitag ◽  
Sepp Kipfstuhl ◽  
Werner F. Kuhs ◽  
...  
Keyword(s):  
Bubble Size ◽  
Large Scale ◽  
Ice Core ◽  
Small Scale ◽  
Air Bubbles ◽  
Number Density ◽  
Glacial Ice ◽  
Size Number ◽  
Bubble Number ◽  
Bubble Number Density

AbstractWe investigated the large-scale (10–1000 m) and small-scale (mm–cm) variations in size, number and arrangement of air bubbles in the EPICA Dronning Maud Land (EDML) (Antarctica) ice core, down to the end of the bubble/hydrate transition (BHT) zone. On the large scale, the bubble number density shows a general correlation with the palaeo-temperature proxy, δ18O, and the dust concentration, which means that in Holocene ice there are fewer bubbles than in glacial ice. Small-scale variations in bubble number and size were identified and compared. Above the BHT zone there exists a strong anticorrelation between bubble number density and mean bubble size. In glacial ice, layers of high number density and small bubble size are linked with layers with high impurity content, identified as cloudy bands. Therefore, we regard impurities as a controlling factor for the formation and distribution of bubbles in glacial ice. The anticorrelation inverts in the middle of the BHT zone. In the lower part of the BHT zone, bubble-free layers exist that are also associated with cloudy bands. The high contrast in bubble number density in glacial ice, induced by the impurities, indicates a much more pronounced layering in glacial firn than in modern firn.

scholarly journals Late-Holocene climate evolution at the WAIS Divide site, West Antarctica: bubble number-density estimates

2011 ◽  
Vol 57 (204) ◽  
pp. 629-638 ◽  
Author(s):  
J.M. Fegyveresi ◽  
R.B. Alley ◽  
M.K. Spencer ◽  
J.J. Fitzpatrick ◽  
E.J. Steig ◽  
...  
Keyword(s):  
Late Holocene ◽  
Accumulation Rate ◽  
Ice Core ◽  
Temperature History ◽  
Flow Density ◽  
Number Density ◽  
West Antarctica ◽  
Surface Cooling ◽  
Bubble Number ◽  
Bubble Number Density

AbstractA surface cooling of ∼1.7°C occurred over the ∼two millennia prior to ∼1700 CE at the West Antarctic ice sheet (WAIS) Divide site, based on trends in observed bubble number-density of samples from the WDC06A ice core, and on an independently constructed accumulation-rate history using annual-layer dating corrected for density variations and thinning from ice flow. Density increase and grain growth in polar firn are both controlled by temperature and accumulation rate, and the integrated effects are recorded in the number-density of bubbles as the firn changes to ice. Number-density is conserved in bubbly ice following pore close-off, allowing reconstruction of either paleotemperature or paleo-accumulation rate if the other is known. A quantitative late-Holocene paleoclimate reconstruction is presented for West Antarctica using data obtained from the WAIS Divide WDC06A ice core and a steady-state bubble number-density model. The resultant temperature history agrees closely with independent reconstructions based on stable-isotopic ratios of ice. The ∼1.7°C cooling trend observed is consistent with a decrease in Antarctic summer duration from changing orbital obliquity, although it remains possible that elevation change at the site contributed part of the signal. Accumulation rate and temperature dropped together, broadly consistent with control by saturation vapor pressure.

Measurement and interpretation of bubble number-density evolution through the upper 1200 meters of the SPC14 South Pole Ice Core

2021 ◽  
Author(s):  
John Fegyveresi ◽  
Richard Alley ◽  
Joan Fitzpatrick ◽  
Donald Voigt ◽  
Zoe Courville ◽  
...  
Keyword(s):  
Ice Core ◽  
South Pole ◽  
Number Density ◽  
Density Evolution ◽  
Bubble Number ◽  
Bubble Number Density

scholarly journals Developing a bubble number-density paleoclimatic indicator for glacier ice

2006 ◽  
Vol 52 (178) ◽  
pp. 358-364 ◽  
Author(s):  
M.K. Spencer ◽  
R.B. Alley ◽  
J.J. Fitzpatrick
Keyword(s):  
Accumulation Rate ◽  
Ice Core ◽  
Published Data ◽  
Mean Annual Temperature ◽  
Number Density ◽  
Grain Number ◽  
Glacier Ice ◽  
A New Technique ◽  
Bubble Number ◽  
Bubble Number Density

AbstractPast accumulation rate can be estimated from the measured number-density of bubbles in an ice core and the reconstructed paleotemperature, using a new technique. Density increase and grain growth in polar firn are both controlled by temperature and accumulation rate, and the integrated effects are recorded in the number-density of bubbles as the firn changes to ice. An empirical model of these processes, optimized to fit published data on recently formed bubbles, reconstructs accumulation rates using recent temperatures with an uncertainty of 41% (P < 0.05). For modern sites considered here, no statistically significant trend exists between mean annual temperature and the ratio of bubble number-density to grain number-density at the time of pore close-off; optimum modeled accumulation-rate estimates require an eventual ~2.02 ± 0.08 (P < 0.05) bubbles per close-off grain. Bubble number-density in the GRIP (Greenland) ice core is qualitatively consistent with independent estimates for a combined temperature decrease and accumulation-rate increase there during the last 5 kyr.

scholarly journals Development of Bubble Size Correlation for Adiabatic Forced Convective Bubbly Flow in Low Pressure Condition Using CFD Code

2020 ◽  
Vol 10 (16) ◽  
pp. 5443
Author(s):  
Jinyeong Bak ◽  
Huiyung Kim ◽  
Jae Jun Jeong ◽  
Dongjin Euh ◽  
Byongjo Yun
Keyword(s):  
Bubble Size ◽  
Bubbly Flow ◽  
Flow Analysis ◽  
Low Pressure ◽  
Good Prediction ◽  
Two Phase ◽  
Local Bubble ◽  
Computational Fluid Dynamics Cfd ◽  
Bubble Number ◽  
Bubble Number Density

In a multidimensional two-phase flow analysis, bubble size significantly affects interfacial transfer terms such as mass, momentum, and energy. With regard to bubbly flow, the application of a simple correlation-type bubble size model presents certain advantages, including short calculation times and ease of usage. In this study, we propose a semi-theoretical correlation developed from a steady state bubble number density transport equation for predicting the distribution of local bubble size using a computational fluid dynamics (CFD) code. The coefficients of the new correlation were determined using the local bubble parameters obtained on the basis of three existing vertical air-water experiments. Finally, these were implemented in commercial CFD code and evaluated against experimental data, which showed that the proposed correlation exhibits good prediction capability for forced convective air-water bubbly flows under low pressure conditions.

Velocity Profile Measurements of Two-Phase Flow in Rectangular Channel Using Ultrasonic Time-Domain Correlation Method

2007 ◽  
Author(s):  
Takuya Hayashida ◽  
Hideki Murakawa ◽  
Hiroshige Kikura ◽  
Masanori Aritomi ◽  
Michitsugu Mori
Keyword(s):  
Flow Measurement ◽  
Two Phase Flow ◽  
Rectangular Channel ◽  
Correlation Method ◽  
Phase Flow ◽  
Number Density ◽  
Two Phase ◽  
Bubble Number ◽  
Bubble Number Density ◽  
Time Domain Correlation

Velocity measurement using ultrasound has attracted much attention in engineering fields and medical science field. Especially, Ultrasonic velocity profile monitor (UVP) has been in the spotlight in engineering fields, because of its many diagnostic advantages. The major advantage is that UVP can obtain instantaneous velocity distributions on beam line by measuring Doppler shift frequencies of echo signals. And UVP is applicable to existing pipes, because it is non-contact measurement technique. In recent years, various studies about UVP have been done, and UVP has already been put to practical use in engineering plants. The authors especially focused on two-phase flow measurement using ultrasound. Previously, we developed a way to measure bubbly flow using UVP. By this method, we are able to separate liquid information from bubbles information to some degrees. However, when the bubble number density is low, a problem occurs. Because the effect of liquid information is strong under that condition. From this fact, we applied the ultrasound time domain correlation method (UTDC) to two-phase flow measurement. This method is our original technique to measure the velocity distribution. It is based on the cross-correlation between two consecutive echoes of ultrasonic pulses. With this method, we can separate liquid information from bubble information even when the bubble number density is low, because reflected signals depend on the size of reflectors and frequency of ultrasound. In this study, the authors applied the UTDC to two-phase flow measurements in rectangular channel using a multi-wave ultrasonic transducer (TDX). The multi-wave TDX has two kinds of basic frequencies. One is 2MHz for the velocity of rising bubbles and the other is 8MHz for the liquid velocity. So it enables us to measure the velocity of the liquid and that of bubbles at the same point and time. The 2MHz ultrasonic element of TDX has 10mm diameter and the 8MHz ultrasonic element has 3mm diameter.

scholarly journals Voronoi volume function: a new probe of cosmology and galaxy evolution

2020 ◽  
Vol 495 (3) ◽  
pp. 3233-3251 ◽  
Author(s):  
Aseem Paranjape ◽  
Shadab Alam
Keyword(s):  
Dark Matter ◽  
Galaxy Evolution ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Voronoi Tessellation ◽  
Small Scale ◽  
Summary Statistics ◽  
Number Density ◽  
Volume Function ◽  
Space Effects

ABSTRACT We study the Voronoi volume function (VVF) – the distribution of cell volumes (or inverse local number density) in the Voronoi tessellation of any set of cosmological tracers (galaxies/haloes). We show that the shape of the VVF of biased tracers responds sensitively to physical properties such as halo mass, large-scale environment, substructure, and redshift-space effects, making this a hitherto unexplored probe of both primordial cosmology and galaxy evolution. Using convenient summary statistics – the width, median, and a low percentile of the VVF as functions of average tracer number density – we explore these effects for tracer populations in a suite of N-body simulations of a range of dark matter models. Our summary statistics sensitively probe primordial features such as small-scale oscillations in the initial matter power spectrum (as arise in models involving collisional effects in the dark sector), while being largely insensitive to a truncation of initial power (as in warm dark matter models). For vanilla cold dark matter (CDM) cosmologies, the summary statistics display strong evolution and redshift-space effects, and are also sensitive to cosmological parameter values for realistic tracer samples. Comparing the VVF of galaxies in the Galaxies & Mass Assembly (GAMA) survey with that of abundance-matched CDM (sub)haloes tentatively reveals environmental effects in GAMA beyond halo mass (modulo unmodelled satellite properties). Our exploratory analysis thus paves the way for using the VVF as a new probe of galaxy evolution physics as well as the nature of dark matter and dark energy.

Progress in Modeling Injector Cavitating Flows With a Multi-Fluid Method

2006 ◽  
Author(s):  
De Ming Wang ◽  
David Greif
Keyword(s):  
Bubble Dynamics ◽  
Measurement Data ◽  
Interfacial Area ◽  
Number Density ◽  
Cavitating Flows ◽  
Set Up ◽  
Single Bubble Dynamics ◽  
Bubble Number ◽  
Bubble Number Density ◽  
Constricted Channel

A finite volume, pressure based semi-implicit algorithm is developed for solving a multi-fluid system of any number of phases with strong coupling between the phases in mass, momentum and energy transfer. The mass transfer from liquid to vapor due to cavitation is modeled based on a single bubble dynamics (Rayleigh-Plesset equation). In order to model the vapor phase of variable size distribution, or polydispersion, the transport equations of bubble number density and interfacial area are derived from taking the moments of the PDF equation in phase space. The modeling of the result equations are effected through consideration of breakup and coalescence. The k-zeta-f turbulence model is adopted which is found to be particularly effective for predicting near wall effects on the turbulence level. Validation efforts are presented in which comparison with available measurement data are made for a number of cases including constricted channel flow with sharp inlet (I-channel), with smooth inlet (Y-channel), a flash-boiling cavitation set-up, and an actual injector set-up.

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