Field measurements and physical models

2012 ◽  
pp. 352-381
Keyword(s):  
Field Measurements ◽  
Physical Models

scholarly journals Mechanisms of Pond Expansion in a Rapidly Submerging Marsh

2021 ◽  
Vol 8 ◽  
Author(s):  
Joshua Himmelstein ◽  
Orencio Duran Vinent ◽  
Stijn Temmerman ◽  
Matthew L. Kirwan
Keyword(s):  
Growth Rates ◽  
Large Scale ◽  
Time Window ◽  
Critical Time ◽  
Field Measurements ◽  
Physical Models ◽  
Primary Driver ◽  
Pond Size ◽  
Power Law Equation ◽  
Historical Photographs

The development and expansion of ponds within otherwise vegetated coastal marshes is a primary driver of marsh loss throughout the world. Previous studies propose that large ponds expand through a wind wave-driven positive feedback, where pond edge erosion rates increase with pond size, whereas biochemical processes control the formation and expansion of smaller ponds. However, it remains unclear which mechanisms dominate at a given scale, and thus how, and how fast, ponds increase their size. Here, we use historical photographs and field measurements in a rapidly submerging microtidal marsh to quantify pond development and identify the processes involved. We find that as small ponds emerge on the marsh platform, they quickly coalesce and merge, increasing the number of larger ponds. Pond expansion rates are maximized for intermediate size ponds and decrease for larger ponds, where the contribution of wave-driven erosion is negligible. Vegetation biomass, soil shear strength, and porewater biogeochemical indices of marsh health are higher in marshes adjacent to stable ponds than in those adjacent to unstable ponds, suggesting that pond growth rates are negatively related to the health of the surrounding marsh. We find that the model of Vinent et al. (2021) correctly predicts measured pond growth rates and size distribution, which suggest the different mechanisms driving pond growth are a result of marsh drowning due to sea level rise (SLR) and can be estimated by simplified physical models. Finally, we show that all relevant processes increasing pond size can be summarized by an empirical power-law equation for pond growth which predicts the temporal change of the maximum pond size as a lower bound for the total pond area in the system. This gives a timescale for the growth of ponds by merging and thus the critical time window for interventions to prevent the irreversible pond expansion associated with large scale pond merging.

scholarly journals Reproducing Field Measurements Using Scaled-Down Hydraulic Model Studies in a Laboratory

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Seung Oh Lee ◽  
Seung Ho Hong
Keyword(s):  
Three Dimensional ◽  
Flow Characteristics ◽  
Field Measurements ◽  
Physical Models ◽  
Laboratory Model ◽  
Scour Depth ◽  
Model Studies ◽  
Sediment Size ◽  
Laboratory Results ◽  
Scale Ratio

Little efforts have been made to the value of laboratory model study in closing the gap between results from idealized laboratory experiments and those from field data. Thus, at first, three bridge sites were selected and equipped with fathometers to find the bed elevation change in the vicinity of bridge pier over time. After and during the flooding, the stream flow variables and their bathymetry were measured using current viable technologies at the field. Then, to develop and suggest a laboratory modeling techniques, full three-dimensional physical models including measured river bathymetry and bridge geometry were designed and fabricated in a laboratory based on the scale ratio except for the sediment size, and the laboratory results were compared with the field measurements. Size of uniform sediment was carefully selected and used in the laboratory to explore the scale effect caused by sediment size scaling. The comparisons between laboratory results and field measurements show that the physical models successfully reproduced the flow characteristics and the scour depth around bridge foundations. With respect to the location of the maximum scour depth, they are not consistent with the results as in the previous research. Instead of occurring at the nose of each pier, the maximum scour depths are located further downstream of each pier column in several experimental runs because of the combination of complex pier bent geometry and river bathymetry, and the resulting unique flow motions around the pier bent.

Recent Radiative and Collisional Atomic Data of Astrophysical Interest

1988 ◽  
Vol 102 ◽  
pp. 129-132
Author(s):  
K.L. Baluja ◽  
K. Butler ◽  
J. Le Bourlot ◽  
C.J. Zeippen
Keyword(s):  
Mass Production ◽  
Bound States ◽  
Physical Models ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
Atomic Data ◽  
Isoelectronic Sequence ◽  
Astrophysical Interest ◽  
Radiative Transitions ◽  
Forbidden Transitions

SummaryUsing sophisticated computer programs and elaborate physical models, accurate radiative and collisional atomic data of astrophysical interest have been or are being calculated. The cases treated include radiative transitions between bound states in the 2p4and 2s2p5configurations of many ions in the oxygen isoelectronic sequence, the photoionisation of the ground state of neutral iron, the electron impact excitation of the fine-structure forbidden transitions within the 3p3ground configuration of CℓIII, Ar IV and K V, and the mass-production of radiative data for ions in the oxygen and fluorine isoelectronic sequences, as part of the international Opacity Project.

Cryo-TEM of amphiphilic polymer and amphiphile/polymer solutions

1993 ◽  
Vol 51 ◽  
pp. 876-877
Author(s):  
Yeshayahu Talmon
Keyword(s):  
Microstructural Characterization ◽  
Building Blocks ◽  
Quantitative Information ◽  
Physical Models ◽  
Specimen Preparation ◽  
Time Resolved ◽  
Temperature Changes ◽  
Temperature And Humidity ◽  
Microstructured Fluids ◽  
Air Streams

To achieve complete microstructural characterization of self-aggregating systems, one needs direct images in addition to quantitative information from non-imaging, e.g., scattering or Theological measurements, techniques. Cryo-TEM enables us to image fluid microstructures at better than one nanometer resolution, with minimal specimen preparation artifacts. Direct images are used to determine the “building blocks” of the fluid microstructure; these are used to build reliable physical models with which quantitative information from techniques such as small-angle x-ray or neutron scattering can be analyzed.To prepare vitrified specimens of microstructured fluids, we have developed the Controlled Environment Vitrification System (CEVS), that enables us to prepare samples under controlled temperature and humidity conditions, thus minimizing microstructural rearrangement due to volatile evaporation or temperature changes. The CEVS may be used to trigger on-the-grid processes to induce formation of new phases, or to study intermediate, transient structures during change of phase (“time-resolved cryo-TEM”). Recently we have developed a new CEVS, where temperature and humidity are controlled by continuous flow of a mixture of humidified and dry air streams.

THE MECHANISM OF RAISING AND QUANTIFICATION OF SPECIFIC HEAT FLUX AT BOILING OF NANOFLUIDS IN FREE CONVECTION CONDITIONS

2017 ◽  
pp. 25-34
Author(s):  
V.N. Moraru
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Capacity ◽  
Specific Heat ◽  
Chemical Properties ◽  
Heating Surface ◽  
Physical Models ◽  
Superheated Liquid ◽  
Two Phase ◽  
Boiling Process

The results of our work and a number of foreign studies indicate that the sharp increase in the heat transfer parameters (specific heat flux q and heat transfer coefficient _) at the boiling of nanofluids as compared to the base liquid (water) is due not only and not so much to the increase of the thermal conductivity of the nanofluids, but an intensification of the boiling process caused by a change in the state of the heating surface, its topological and chemical properties (porosity, roughness, wettability). The latter leads to a change in the internal characteristics of the boiling process and the average temperature of the superheated liquid layer. This circumstance makes it possible, on the basis of physical models of the liquids boiling and taking into account the parameters of the surface state (temperature, pressure) and properties of the coolant (the density and heat capacity of the liquid, the specific heat of vaporization and the heat capacity of the vapor), and also the internal characteristics of the boiling of liquids, to calculate the value of specific heat flux q. In this paper, the difference in the mechanisms of heat transfer during the boiling of single-phase (water) and two-phase nanofluids has been studied and a quantitative estimate of the q values for the boiling of the nanofluid is carried out based on the internal characteristics of the boiling process. The satisfactory agreement of the calculated values with the experimental data is a confirmation that the key factor in the growth of the heat transfer intensity at the boiling of nanofluids is indeed a change in the nature and microrelief of the heating surface. Bibl. 20, Fig. 9, Tab. 2.

79. Comparison of Benzene-Specific Field Measurements at Oil Refineries

1999 ◽  
Author(s):  
W.R. Haag ◽  
P. Owens ◽  
D. Mayszak ◽  
J. Katona ◽  
B. Mangilin ◽  
...  
Keyword(s):  
Field Measurements ◽  
Oil Refineries ◽  
Specific Field

An evaluation of a strategic de-stocking regime for dairying to improve nitrogen efficiency and reduce nitrate leaching from dairy farms in nitrate-sensitive areas

2000 ◽  
pp. 105-110
Author(s):  
Cecile De Klein ◽  
Jim Paton ◽  
Stewart Ledgard
Keyword(s):  
New Zealand ◽  
Nitrate Leaching ◽  
Management Practice ◽  
Field Measurements ◽  
Dairy Farms ◽  
Nitrogen Efficiency ◽  
Management Tool ◽  
Pasture Production ◽  
Leaching Losses ◽  
Sensitive Areas

Strategic de-stocking in winter is a common management practice on dairy farms in Southland, New Zealand, to protect the soil against pugging damage. This paper examines whether this practice can also be used to reduce nitrate leaching losses. Model analyses and field measurements were used to estimate nitrate leaching losses and pasture production under two strategic de-stocking regimes: 3 months off-farm or 5 months on a feed pad with effluent collected and applied back to the land. The model analyses, based on the results of a long-term farmlet study under conventional grazing and on information for an average New Zealand farm, suggested that the 3- or 5-month de-stocking could reduce nitrate leaching losses by about 20% or 35-50%, respectively compared to a conventional grazing system. Field measurements on the Taieri Plain in Otago support these findings, although the results to date are confounded by drought conditions during the 1998 and 1999 seasons. The average nitrate concentration of the drainage water of a 5-month strategic de-stocking treatment was about 60% lower than under conventional grazing. Pasture production of the 5-month strategic de-stocking regime with effluent return was estimated based on data for apparent N efficiency of excreta patches versus uniformlyspread farm dairy effluent N. The results suggested that a strategic de-stocking regime could increase pasture production by about 2 to 8%. A cost/ benefit analysis of the 5-month de-stocking system using a feed pad, comparing additional capital and operational costs with additional income from a 5% increase in DM production, show a positive return on capital for an average New Zealand dairy farm. This suggests that a strategic destocking system has good potential as a management tool to reduce nitrate leaching losses in nitrate sensitive areas whilst being economically viable, particularly on farms where an effluent application system or a feed pad are already in place. Keywords: dairying, feed pads, nitrate leaching, nitrogen efficiency, productivity, strategic de-stocking

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