A laboratory study of frazil evolution in a counter-rotating flume

2004 ◽  
Vol 31 (6) ◽  
pp. 899-914 ◽  
Author(s):  
Shi Qiang Ye ◽  
Jay Doering ◽  
Hung Tao Shen
Keyword(s):  
Flow Velocity ◽  
Size Distribution ◽  
Air Temperature ◽  
Stable State ◽  
Water Velocity ◽  
Image Process ◽  
Frazil Ice ◽  
Process System ◽  
Rotating Flume ◽  
Log Normal

A series of experiments was carried out using a counter-rotating flume that is housed in a computer-controlled cold room. A digital image process system (DIPS) was used to observe frazil ice processes. In particular, the effects of air temperature and flow velocity on the supercooling and frazil ice processes were examined. The super cooling process was found to be strongly related to air temperature and water depth, but only weakly related to water velocity. The water velocity has a strong influence on frazil evolution, frazil size, and number of the particles, however. The measured frazil size distribution by volume was found to be reasonably well approximated by a log-normal distribution. Frazil growth continues in number and size during supercooling and appears to reach a stable state at the end of the principal period of supercooling. All characteristic parameters of the supercooling processes and frazil size distribution were found to be related to the Reynolds number, an index of the intensity of flow turbulence. This information can be used in the development of models of frazil ice dynamics.Key words: supercooling, frazil ice, distribution, flow velocity, air temperature, turbulence.

Simulation of the supercooling process and frazil evolution in turbulent flows

2004 ◽  
Vol 31 (6) ◽  
pp. 915-926 ◽  
Author(s):  
Shi Qiang Ye ◽  
Jay Doering
Keyword(s):  
Turbulent Flows ◽  
Heat Balance ◽  
Laboratory Experiments ◽  
Distribution Model ◽  
Secondary Nucleation ◽  
Frazil Ice ◽  
Rotating Flume ◽  
Flow Turbulence ◽  
Log Normal ◽  
Log Normal Distribution

A model to simulate the supercooling process and frazil ice evolution in a counter-rotating flume is developed based on a series of laboratory experiments. The characteristics of the supercooling process were found to be related to air temperature and flow turbulence. Frazil ice growth was observed to follow a log-normal distribution model. The model avoids the need to simulate seeding, secondary nucleation, flocculation–breakup, and gravitational removal. Only the overall heat balance is considered during the entire process. The simulations show good agreements with experimental time–temperature curves and frazil evolution.Key words: supercooling, frazil ice, size distribution, concentration, turbulence, simulation.

scholarly journals Evolution of Surge-Type Glaciers in the Yangtze River Headwater Using Multi-Source Remote Sensing Data

2019 ◽  
Vol 11 (24) ◽  
pp. 2991 ◽  
Author(s):  
Jin Yan ◽  
Mingyang Lv ◽  
Zhixing Ruan ◽  
Shiyong Yan ◽  
Guang Liu
Keyword(s):  
Remote Sensing ◽  
Flow Velocity ◽  
Yangtze River ◽  
Stable State ◽  
Remote Sensing Data ◽  
Radar Data ◽  
Series Data ◽  
The Yangtze River ◽  
Glacier Surges ◽  
Short Time

A surge-type glacier is a special and dangerous type of glacier, which can advance quickly in a short-time with cycles. Glaciers in the Yangtze River headwater are generally acknowledged to be in a stable state. However, not all of those glaciers are stable. In this paper, five glaciers from the Yangtze River headwater glacier were selected as the experimental subjects, and multi-source remote sensing images were used to study and analyze the surge behavior over the past 30 years. Based on the Landsat series data, ERS-2, and ENVISAT radar data, this paper extracts the glacier centerline information, glacial area information, and glacial flow velocity during different time periods from 1988 to 2018, which are used to monitor the active periods of glacier surges. We found three surge-type glaciers in the study area. The glacial characteristics of the three glaciers showed some drastic changes, they can advance quickly nearly 800 m in active periods, their area change can reach 2.0 × 106 m2, and their flow velocity can suddenly increase by dozens of times. Surging periods and the initiated time of the three glaciers are different, which are locked in 1997, 2003, and 1997–1998. All those surges ended within one to two years. We suggest that the surges in this paper are dominated by hydrological conditions.

scholarly journals The aerosol-climate model ECHAM5-HAM

2005 ◽  
Vol 5 (4) ◽  
pp. 1125-1156 ◽  
Author(s):  
P. Stier ◽  
J. Feichter ◽  
S. Kinne ◽  
S. Kloster ◽  
E. Vignati ◽  
...  
Keyword(s):  
Size Distribution ◽  
Climate Model ◽  
Normal Modes ◽  
Anthropogenic Activity ◽  
Climate Modelling ◽  
Extensive Evaluation ◽  
Wide Range ◽  
Log Normal ◽  
Year 2000

Abstract. The aerosol-climate modelling system ECHAM5-HAM is introduced. It is based on a flexible microphysical approach and, as the number of externally imposed parameters is minimised, allows the application in a wide range of climate regimes. ECHAM5-HAM predicts the evolution of an ensemble of microphysically interacting internally- and externally-mixed aerosol populations as well as their size-distribution and composition. The size-distribution is represented by a superposition of log-normal modes. In the current setup, the major global aerosol compounds sulfate (SU), black carbon (BC), particulate organic matter (POM), sea salt (SS), and mineral dust (DU) are included. The simulated global annual mean aerosol burdens (lifetimes) for the year 2000 are for SU: 0.80 Tg(S) (3.9 days), for BC: 0.11 Tg (5.4 days), for POM: 0.99 Tg (5.4 days), for SS: 10.5 Tg (0.8 days), and for DU: 8.28 Tg (4.6 days). An extensive evaluation with in-situ and remote sensing measurements underscores that the model results are generally in good agreement with observations of the global aerosol system. The simulated global annual mean aerosol optical depth (AOD) is with 0.14 in excellent agreement with an estimate derived from AERONET measurements (0.14) and a composite derived from MODIS-MISR satellite retrievals (0.16). Regionally, the deviations are not negligible. However, the main patterns of AOD attributable to anthropogenic activity are reproduced.

Evaluation of Models for Droplet Shear Effect of Centrifugal Pump

2018 ◽  
Author(s):  
Ramin Dabirian ◽  
Shihao Cui ◽  
Ilias Gavrielatos ◽  
Ram Mohan ◽  
Ovadia Shoham
Keyword(s):  
Experimental Data ◽  
Size Distribution ◽  
Centrifugal Pump ◽  
Droplet Size ◽  
Separation Efficiency ◽  
Droplet Diameter ◽  
Droplet Size Distribution ◽  
Production Equipment ◽  
Transportation Equipment ◽  
Log Normal

During the process of petroleum production and transportation, equipment such as pumps and chokes will cause shear effects which break the dispersed droplets into smaller size. The smaller droplets will influence the separator process significantly and the droplet size distribution has become a critical criterion for separator design. In order to have a better understanding of the separation efficiency, estimation of the dispersed-phase droplet size distribution is very important. The objective of this paper is to qualitatively and quantitatively investigate the effect of shear imparted on oil-water flow by centrifugal pump. This paper presents available published models for the calculation of droplet size distribution caused by different production equipment. Also detailed experimental data for droplet size distribution downstream of a centrifugal pump are presented. Rosin-Rammler and Log-Normal Distributions utilizing dmax Pereyra (2011) model as well as dmin Kouba (2003) model are used in order to evaluate the best fit distribution function to simulate the cumulative droplet size distribution. The results confirm that applying dmax Pereyra (2011) model leads to Rosin-Rammler distribution is much closer to the experimental data for low shear conditions, while the Log-Normal distribution shows better performance for higher shear rates. Furthermore, the predictions of Modified Kouba (2003) dmin model show good results for predicting the droplet distribution in centrifugal pump, and even better predictions under various ranges of experiments are achieved with manipulating cumulative percentage at minimum droplet diameter F(Dmin).

Estimation and fingerprinting of the size distribution of non-interacting spherical particles from small-angle scattering data

2021 ◽  
Vol 54 (5) ◽  
Author(s):  
Debasis Sen ◽  
Ashwani Kumar ◽  
Avik Das ◽  
Jitendra Bahadur
Keyword(s):  
Size Distribution ◽  
Small Angle ◽  
Colloidal Particles ◽  
Nonlinear Least Squares ◽  
Small Angle Scattering ◽  
Spherical Particles ◽  
Scattering Data ◽  
Fitting Procedure ◽  
Angle Scattering ◽  
Log Normal

A new method to estimate the size distribution of non-interacting colloidal particles from small-angle scattering data is presented. The method demonstrates that the distribution can be efficiently retrieved through features of the scattering data when plotted in the Porod representation, thus avoiding the standard fitting procedure of nonlinear least squares. The present approach is elaborated using log-normal and Weibull distributions. The method can differentiate whether the distribution actually follows the functionality of either of these two distributions, unlike the standard fitting procedure which requires a prior assumption of the functionality of the distribution. After validation with various simulated scattering profiles, the formalism is used to estimate the size distribution from experimental small-angle X-ray scattering data from two different dilute dispersions of silica. At present the method is limited to monomodal distributions of dilute spherical particles only.

scholarly journals Laboratory study of the properties of frazil ice particles and flocs in water of different salinities

2019 ◽  
Vol 13 (10) ◽  
pp. 2751-2769 ◽  
Author(s):  
Christopher C. Schneck ◽  
Tadros R. Ghobrial ◽  
Mark R. Loewen
Keyword(s):  
Growth Rate ◽  
High Resolution ◽  
Saline Water ◽  
Camera System ◽  
Average Growth ◽  
Frazil Ice ◽  
Ice Particles ◽  
Thermodynamic Conditions ◽  
Mean Size ◽  
Log Normal

Abstract. Measurements of the size and shape of frazil ice particles and flocs in saline water and of frazil ice flocs in freshwater are limited. This study consisted of a series of laboratory experiments producing frazil ice at salinities of 0 ‰, 15 ‰, 25 ‰ and 35 ‰ to address this lack of data. The experiments were conducted in a large tank in a cold room with bottom-mounted propellers to create turbulence. A high-resolution camera system was used to capture images of frazil ice particles and flocs passing through cross-polarizing lenses. The high-resolution images of the frazil ice were processed using a computer algorithm to differentiate particles from flocs and determine key properties including size, concentration and volume. The size and volume distributions of particles and flocs at all four salinities were found to fit log-normal distributions closely. The concentration, mean size, and standard deviation of flocs and particles were assessed at different times during the supercooling process to determine how these properties evolve with time. Comparisons were made to determine the effect of salinity on the properties of frazil ice particles and flocs. The overall mean size of frazil ice particles in saline water and freshwater was found to range between 0.52 and 0.45 mm, with particles sizes in freshwater ∼13 % larger than in saline water. However, qualitative observations showed that frazil ice particles in saline water tend to be more irregularly shaped. The overall mean size of flocs in freshwater was 2.57 mm compared to a mean size of 1.47 mm for flocs in saline water. The average growth rate of frazil particles was found to be 0.174, 0.070, 0.033, and 0.024 mm min−1 and the average floc growth rate was 0.408, 0.118, 0.089, and 0.072 mm min−1 for the 0 ‰, 15 ‰, 25 ‰, and 35 ‰, respectively. Estimates for the porosity of frazil ice flocs were made by equating the estimated volume of ice produced based on thermodynamic conditions to the estimated volume of ice determined from the digital images. The estimated porosities of frazil ice flocs were determined to be 0.86, 0.82, 0.8 and 0.75 for 0 ‰, 15 ‰, 25 ‰ and 35 ‰ saline water, respectively.

Poly-dispersed modeling of bubbly flow using the log-normal size distribution

2019 ◽  
Vol 201 ◽  
pp. 237-246 ◽  
Author(s):  
E.M.A. Frederix ◽  
T.L.W. Cox ◽  
J.G.M. Kuerten ◽  
E.M.J. Komen
Keyword(s):  
Size Distribution ◽  
Bubbly Flow ◽  
Log Normal
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