Modelling of water jet impact on molten metal

Splashes of high-temperature melt spreading over a water pool bottom can be a reason for the formation of a zone where melt, water and steam are mixed, providing conditions for powerful steam explosions. The paper considers the formation of melt splashes arising from the impact of a water jet on the surface of the melt. Numerical simulations are performed in 3D formulation, using the VOF method and an improved phase change model. The evolution of melt surface following the water jet impact is demonstrated, including the formation of a cavern, a primary melt splash known as the crown, as well as a secondary splash following the collapse of the cavern, known as the cumulative jet. Parametric study for the melt splash height dependence on the water jet geometry and velocity is carried out. The results of numerical analysis are discussed from the point of view of the similarity with respect to the momentum and kinetic energy of water jet. The significance of the results for the steam explosion problem is discussed.

Evaluation of melt-water premixture formation due to Rayleigh-Taylor instabilities

A linear analysis of the stability of the three-layer stratified hydrodynamic system “water (top) – steam – melt (bottom)” has been performed. Kinematic and dynamic conditions on the “water – steam” and “steam – melt” interfaces are formulated, and on their basis a dispersion equation is obtained that relates the circular frequency of perturbations to the wavenumber. Analysis of this equation made it possible to determine the region of instability of this system and to find the wavenumber of the most fastly growing harmonics. The results obtained were used to estimate the size of bubbles formed at the interface between steam and water due to the development of the Rayleigh-Taylor instability. The obtained theoretical results are consistent with experimental observations in such systems. The heights of the melt splashes into water due to the collapse of the formed steam bubble were estimated. The obtained estimations demonstrate possibilities of the formation of melt-water mixture region during the spreading of the melt under a water layer, in which a strong steam explosion can occur.

ESTIMATING CONTRIBUTION OF WATER FLOW COMPONENTS TO KAMENG RIVER BASIN USING HYDROLOGICAL MODELLING

The Himalayas, also known as third pole of the Earth feed some of the major rivers of the world viz. Ganga, Indus, Brahmaputra etc. The accurate assessment of water resources in eastern Himalayas is very important for respective policy makers. The detailed assessment of water resources and hydrological cycle component are very critical for attaining United Nations sustainable development goals (SDGs) such as affordable and clean energy, clean water and sanitation and building resilient infrastructure This study focuses on Kameng river basin, estimating the melt water & its contribution to the total discharge of the river. A 3-layer VIC model coupled with energy balance algorithm is used to estimate the patterns of melt and discharge profile in the region. Net contribution of melt water to the river were estimated to be about 18% during peak melt season in upper catchments. With advancement in technology, acquiring meteorological data via remote sensing has become more accurate & of high resolution. This data is one of the major inputs of the model. With accurate forecasting of these parameters, multipurpose hydropower projects in these regions can plan well in advance thus playing a major role in Integrated Water Resource Management. In current study the coefficient of determination & Nash-Sutcliffe efficiency were calculated to be 0.82 & 0.71 respectively. With increasing population in the region, any substantial change in the streamflow will have consequences unknown as of now, thus making this study a necessity & need of hour.

Peculiarities and ecological consequences of climate warming in the Northern Caspian semi-desert

Data on the weather conditions and monitoring of vegetation ecosystems in the Northern Caspian semi-desert for the 70-year period were analyzed. A gradual increase in the average air temperature per hydrological year by 2.73ºC (0.039ºC/year) has been revealed. Before and after the 2000s its increase was caused by warming of the cold and warm period of the year, respectively. An increase of the annual atmospheric precipitation in the spring-summer period was detected, mainly in 1978–1995 due to April-June precipitation. The humidification coefficient dynamics allows distinguishing three periods. The first period (1951–1977) is characterized by insignificant fluctuations around the average value (0.30); the second period (1978–1994) is characterized by good moisture, and the third period (1995–2020), on the contrary, – by severe aridity. These climate changes have led to significant transformation of the snow cover formation mechanisms, the surface runoff of spring melt water, and the ground water level. Despite such fluctuations of natural conditions, the annual productivity of virgin vegetation remains in dynamic equilibrium, changing over time in a wave-like manner, with no introduction of heterogeneous species. The protective afforestation has no chance for sustainable development due to warming of the winter months by 2000, which led to the absence of additional moistening of forest crops for a long period due to the deficiency of snow accumulation and surface inflow of spring melt water. The shrinkage of forest stands was intensified by recurrent annual summer atmospheric droughts. The production of agricultural crops was discontinued since the mid-1990s due to their annual failure, as well as the aridity of the growing seasons. The climate warming of the last two decades has brought the landscape of the flat semi-desert territory of the Northern Caspian region ever closer to its original state without agricultural fields and forest plantations. The population of the region is forced to return to extensive cattle breeding, which has existed here since ancient times.

Purification of urbanized melt water with plant sorbents

The article deals with the problem of purification of melt water generated by the urbanized territories. It is proposed to use wood residue from sawing of plantings to obtain relatively inexpensive sorption material for the contamination extraction from surface wastewater. The aim of this work is to study the sorption properties of the material obtained by sawing of plantings. Experimental modeling of sorption of dissolved petroleum products and copper ions from an aqueous solution of milled branches of black poplar is carried out under static conditions. The sorption process is studied in accordance with a three-factor design experiment. Laboratory modeling determines the optimum parameters of water purification and the degree of mutual influence of contaminants on the sorption process. Natural material obtained from the poplar components shows the sorption properties in relation to oil products and copper ions in the water environment. The filters made of milled branches and used in local treatment plants will allow solving the problems of municipal services, namely utilization of wood residue from sawing of plantings and effective melt water purification due to the low-cost filtering materials.

Spring freshet on East European plain: changes in drivers and conditions during last three decades

<p>Over the past 20 years, the climate on the East European plain tends to be significantly warmer and drier. Winters became shorter and spring freshet’s conditions have been changed significantly. Maximum snow depth was the most important factor of spring freshet formation 30 years ago, but nowadays it has no significance at all and main factor today is melt water losses on infiltration and evaporation.</p><p>We registered a decrease in the period of stable snow accumulation (on average by 20% in the southern and southwestern parts of the East European Plain) because of the increase in winter temperatures. More often during first part of winter snow cover disappeared totally. The number of thaws and their duration at the end of the winter also increase and this leads to earlier and more prolonged melting of the snow pack. In these conditions, an extremely low spring freshet is formed. Our studies show that with the condition of an equal maximum snow depth the slow snowmelt forms the spring freshet up to 4 times less in volume than the fast melting.</p><p>Soil moisture also plays an important role in the melt water losses. The most part of the East European Plain is characterized by a decrease in soil moisture in late autumn, which indicates increased losses during snow melting period.</p><p>Still, the most significant changes in the structure of the factors of spring freshet formation are common to the southern and southwestern parts of the East European Plain. In the northern part, conservative factors still dominate, although this area is characterized by the significant increase in winter temperatures.</p><p>The study was supported by Russian Science Foundation Proj. №19-77-10032</p>

Evidences of melt water control on crevasse propagation using dense array seismic observations

<p>Crevasses are inherent features of glaciers and Ice Sheets. They exert a primary control on glacier dynamics, such as, for example, along shear margins through reducing the overall glacier ice viscosity, or at glacier and Ice Sheet fronts through controlling the onset of serac falls and of ice sheet instabilities (calving, ice shelf disintegration). However, our understanding of crevasse formation and propagation, and in particular the effect of melt water, remains limited due to lacking observations. Here we provide novel observational insights into englacial fracturing, the depth of crevasses and their depth propagation rates using dense seismic array monitoring on an Alpine glacier. We systematically detect and locate englacial seismic events through applying matched-field-processing on a particularly dense seismic array of 98 sensors deployed on the Glacier d’Argentière during 1-month in spring 2018. We observe rupture fronts along crevasses, which propagate from the glacier center to the glacier side at typical velocities of few hundreds of meters per day, i.e. at velocities that are much lower than those of seismic waves but much higher than those of glacier flow. We argue based on a dedicated spatial and temporal analysis that crevasse rupture propagation is set by the migration of water along the crevasse tip. We also observe that crevasses are associated with a wide range of depths, varying from the near surface to the glacier base, which at the present site is located about a hundred meters below the surface. This observation is particularly interesting, since it provides evidences that (i) crevasses are water filled and (ii) crevasses play a role in the supply of water to the bed. These findings are further supported by the observation that surface melt modulates the seismic activity of crevasses including those reaching the bed. Finally, by evaluating coherent structures in the crevasse population, we are able to infer their depth propagation rate, which we find is constant through the ice column, as expected if the surrounding ice stress field is counterbalanced by the water pressure in the crevasse. These observationally-derived findings provide useful grounds to test and improve theories of crevasse dynamics and their control in the overall transfer of water from the surface to the bed.</p>

Quantifying the impact of submesoscale dynamics on the evolution of Arctic freshwater fronts

<p>The dramatic decrease in Arctic sea ice has resulted in a corresponding increase in the seasonal freshwater flux due to melt water in the Canada Basin. This source of freshwater can be quite patchy as sea ice breaks aparts and melts, resulting in freshwater fronts that are strained and stirred by the mesoscale eddy field. We would like to understand the relevant processes that determine the evolution of these freshwater fronts and how heat and salt are exchanged between the fresh melt water and the background water masses. In particular we investigate the importance of submesoscale processes for the lateral and vertical exchange of heat and salt, using high resolution observations of a freshwater front in the Arctic to initialise idealised simulations of frontal evolution. We isolate the effect of submesoscale dynamics by comparing high resolution submesoscale-resolving simulations with lower resolution simulations permitting only larger-scale eddies. Comparisons with observed temperature wavenumber spectra will be presented to investigate whether the simulated dynamics are representative of observations. Heat and salt budgets are presented for the simulations and the impact of submesoscale dynamics on the balance between across-front ageostrophic and geostrophic transports will be discussed. We will also discuss the implications of these results on the seasonal redistribution of heat over the upper ocean, specifically do submesoscale dynamics lead to an increase in the vertical transport of heat across the base of the summer mixed layer, therefore increasing the heat content within the winter mixed layer and delaying the formation of sea ice in the fall?</p>