Mathematical modelling of the selective deep water intake process in a non-prismatic continuously stratified reservoir

Разработана математическая модель селективного водозаборного процесса в узко-глубоком непризматическом водоеме при наличии в нем прямой непрерывной плотностной стратификации. Модель представляет контактную краевую задачу потенциального движения воды в указанном водоеме. Движение воды обусловлено забором воды через два окна, устроенных одно над другим на напорной грани водоема. Учтена непризматическая конфигурация водоема в плане и по вертикали. Непризматические конфигурации описаны экспоненциальными функциями. В результате аналитического решения поставленной контактной краевой задачи получена совокупность расчетных формул, которая с привлечением конечноразностного метода Рунге-Кутты и компьютерных вычислительных систем позволила построить линии тока, приходящие к верхней кромке нижнего водозаборного окна. Вычислительные эксперименты показали, что по мере увеличения скорости потока воды через верхнее окно указанные линии тока опускаются вниз. При этом становится возможным управлять водозаборным процессом через нижнее окно с тем расчетом, чтобы в нижнее окно вода поступала из нижних холодных слоев водоема, что часто бывает необходимо для нужд теплоотвода от тепловыделяющих устройств предприятий, в том числе тепловых и атомных электростанций. Purpose. Mathematical simulation of the selective water intake process in a non-prismatic reservoir in the presence of continuous density stratification. Methodology. Water intake is carried out through two windows arranged one above the other on the pressure face of the reservoir. The non-prismatic configuration of the reservoir both in vertical and horizontal planes is taken into account. The contact initial-boundary value problem of the theory for surface and internal gravitational waves in an ideal incompressible fluid is used. Findings. As a result of the analytical solution of the mathematical model, a set of calculation formulas was obtained, which allows calculating the current lines coming to the upper edge of the lower water intake window. Originality/value. Authors obtain a set of formulas for the components of the water velocity vector. Using the set, a nonlinear boundary value problem is posed and solved for calculation of the current line coming to the upper edge of the lower water intake window by the finite-difference Runge-Kutta method. Based on the results of computational experiments, authors proved that the longitudinal and vertical non-prismatic configuration of a stratified reservoir significantly affects the process of selective water intake. It is proved that as the rate of water intake through the upper window increases, the thickness of the active layer from which water is taken through the lower window decreases to a certain minimum value. This hydrodynamic effect allows taking water from the deep cold layers of the reservoir

Establishing the conditions for the formation of a near-wall layer of solid granular fill of a rotating drum

This paper reports the assessment of the influence of dynamic motion parameters on the formation and disappearance at the cylindrical surface of the chamber of the rotating drum of the near-wall layer of non-loose granular fill. Based on the results of experimental visualization of the flow, the effect of solidity on the behavior of granular fill was revealed. The hydrodynamic effect of fill quasi-liquefaction under the action of solidity has been established, which involves the occurrence of a connecting interaction between adjacent layers and the surface of the chamber. Conversion of shear circulation flow to homogeneous dense clustered stream with slipping and rolling without relative movement of particles was detected. The hydrodynamic characteristics of circulation flow transition to the near-wall layer mode during rotation acceleration have been defined. Such a transition is implemented by smoothly increasing the thickness of the layer when the rest of the fill is circulated at the bottom of the chamber. The effect of the rheological hysteresis of the movement of the rotating chamber fill, caused by quasi-liquefaction of non-loose granular environment, has been established. The effect implies exceeding the speed limit ωfl in the formation of a near-wall layer, at rotation acceleration, above the boundary ωdl of the layer disappearance when the rotation slows down. The manifestation of hysteresis mainly increases with an increase in Reynolds number. The intensity of increased hysteresis manifestation increases with a decrease in the degree of filling the chamber. The value of the Froud number for the ωfl and ωdl boundaries increases with the increase in Re. It has been established that at the relative particle size of the dispersed fill ψdc≈(0.065–1.04)·10‑3 and Re=30–500, Fr=1–2.9, for the ωfl boundary, and Fr=0.5–1.4, for the ωdl boundary. The Fr value for the ωfl limit was found to exceed this value for the ωdl boundary by 1.6–2.1 times. The established effects make it possible to substantiate the rational parameters for the grinding process in drum-roll mills

Experimental Studies Of Wear and Tear of Asphalt Concrete Surfacing Under the Action of Water Pressure in the Micropores

Постановка задачи. Целью исследования является выявление влияния увлажненного покрытия на его износ. Рассматривается механизм воздействия транспортной нагрузки в присутствии влаги и экспериментальные методы измерения ее воздействия на износ верхнего слоя асфальтобетона. Результаты. Определен вклад наличия влаги в верхнем слоя дорожного покрытия на его износ в виде образования колеи, исследовано гидродинамическое воздействие воды в микропорах покрытия. Получены экспериментальные данные величин давления воды в порах асфальтобетонного покрытия в увлажненном состоянии под действием колес движущегося транспортного потока. Это позволило определить максимальные величины барического воздействия, глубину проникновения фронта давления жидкости и влияние его на разрушение покрытия. Выводы. Анализ полученных данных показал не только наличие хрупкого разрушения, но и наличие ударного воздействия движущейся в порах асфальтобетона влаги, превышающего его структурную прочность. С использованием экспериментальных данных получены регрессионные зависимости величины износа от стандартных параметров потока. Для эксплуатируемых покрытий регрессионная зависимость позволяет прогнозировать величину износа на весь жизненный цикл дороги. Statement of the problem. The purpose of the study is to identify the effect of a wetted surfacing on its wear and tear. The mechanism of the effect of transport load in the presence of moisture and experimental methods of measuring its effect on the wear of the upper layer of asphalt concrete are discussed. Results. The contribution of the presence of moisture in the upper layer of the road surface to its wear and tear in the form of rutting is identified, and the hydrodynamic effect of water in the micropores of the surface is examined. Experimental data on the values of water pressure in the pores of an asphalt concrete pavement in a wet state under the action of the wheels of a moving traffic stream have been obtained. This made it possible to identify the maximum values of the pressure effect, the depth of penetration of the liquid pressure front and its influence on the destruction of a surfacing. Conclusions. Analysis of the obtained data showed not only the presence of brittle fracture, but also an impact effect of moisture moving in the pores of asphalt concrete exceeding its structural strength. Using the experimental data, regression dependences of the wear and tear value on the standard flow parameters were obtained. For the pavements in use, the regression dependence makes it possible to predict the amount of wear and tear for the entire life cycle of the road.

Thermal Analysis and Parametric Investigation of PCM-Air Cooled Lithium Ion Battery Pack

A parametric analysis has been conducted for Phase Change Material-Air cooled battery pack. The system is composed of 26650 lithium-ion LiFePO4 batteries enclosed by PCM. 1-D thermal model for the PCM domain is developed using the Enthalpy method. The finite volume method is employed to solve the energy equation for both cell and PCM domain. The developed computational algorithm has been validated as a result of the simulations for the same conditions with the literature. The discharge process of the batteries has been investigated for 2C, 3C, and 5C rates. Thermal analyses have been performed for passive (natural convection) and active cooling (forced convection). It is aimed to keep the temperature of the battery cell under critical levels. A parametric investigation for crucial parameters like; PCM layer thickness, the thermal conductivity of the PCM, the arrangement of the batteries has been performed. Simulations have been conducted for the constant air velocity and the pumping power. Thanks to the constant pumping power analysis, thermally best-performing configuration has been sought by eliminating the hydrodynamic effect.

EXPERIMENTAL STUDIES OF WEARING AND TEARING OF ASPHALT CONCRETE SURFACING UNDER THE ACTION OF WATER PRESSURE IN MICROPORES

Statement of the problem. The goal of this study is to identify the effect of wet surfacing on its wear and tear. The mechanism of influence of transport loading in the presence of moisture and experimental methods of measurement of its influence on wear and tear of the top layer of asphalt concrete are discussed. Results. The contribution of the presence of moisture in the upper layer of the pavement to its wear and tear in the form of track formation was identified, and the hydrodynamic effect of water in the micropores of the pavement was investigated. Experimental data on the values of water pressure in the pores of the asphalt-concrete pavement in the moistened state under the action of the wheels of the moving traffic flow were obtained. Therefore it became possible to identify the maximum values of the pressure effect, the depth of penetration of the fluid pressure front and its effect on the destruction of the surfacing.Conclusions. The analysis of the data showed not only the presence of brittle fracture, but also the impact of moisture moving in the pores of asphalt concrete, exceeding its structural strength. Using experimental data, regression dependences of the wear and tear value on the standard flow parameters were obtained. For the operated surfacings regression dependence enables one to predict the size of wear and tear for the whole life cycle of the road.

Viewpoint: Reply to Comment on 'Using NMR to Test Molecular Mobility During a Chemical Reaction'

Reports of boosted diffusion during chemical and enzymatic reactions have inspired a loyal community of scientists who find them so counter-intuitive that they must be artifact. This second Comment on the subject by these authors is about technicalities of how to analyze data we deposited online regarding J. Phys. Chem. Lett. (2021) 12, 2370 and Science (2020) 369, 537. Now that their own data is also online, one apparent discrepancy can be resolved: we demonstrate that the authors’ data agrees with ours because their first Comment on this subject reported only truncated short-time excerpts of the longer time series they deposited online (zenodo.org/record/4628353). This second Comment adds 5 additional objections, 4 of which are too technical to change the qualitative conclusion. The 5th objection errs because it omits to recognize intermediate states of the click reaction during which one reactant complexes with the catalyst to form an object of larger size. Elsewhere we analyzed in great detail the respective influences of boosted diffusion and this hydrodynamic effect (doi.org/10.26434/chemrxiv.14740563.v1). The factual evidence and reasoning in this Reply strongly support this laboratory’s earlier conclusions regarding boosted diffusion during common chemical reactions.

Viewpoint: Reply to Comment on 'Using NMR to Test Molecular Mobility During a Chemical Reaction'

Reports of boosted diffusion during chemical and enzymatic reactions have inspired a loyal community of scientists who find them so counter-intuitive that they must be artifact. This second Comment on the subject by these authors is about technicalities of how to analyze data we deposited online regarding J. Phys. Chem. Lett. (2021) 12, 2370 and Science (2020) 369, 537. Now that their own data is also online, one apparent discrepancy can be resolved: we demonstrate that the authors’ data agrees with ours because their first Comment on this subject reported only truncated short-time excerpts of the longer time series they deposited online (zenodo.org/record/4628353). This second Comment adds 5 additional objections, 4 of which are too technical to change the qualitative conclusion. The 5th objection errs because it omits to recognize intermediate states of the click reaction during which one reactant complexes with the catalyst to form an object of larger size. Elsewhere we analyzed in great detail the respective influences of boosted diffusion and this hydrodynamic effect (doi.org/10.26434/chemrxiv.14740563.v1). The factual evidence and reasoning in this Reply strongly support this laboratory’s earlier conclusions regarding boosted diffusion during common chemical reactions.

Experimental Studies on Dry Gas Seals With Time-Resolved Film Thickness Measurements

Dry gas lubricated non-contacting mechanical seals (DGS) are acknowledged as the sophisticated shaft end sealing solution which is most commonly found in turbo-compressors. Especially under demanding conditions where high speed is combined with high pressure, DGS becomes the preferred choice over other sealing alternatives. A reliable operation of DGS, due to the non-contact running between its rotating and stationary rings, is secured by the gas film in the region of a few microns in thickness. This paper presents the measurement method of obtaining the thickness of the running gap in two radial positions, namely the inner and outer diameter of the sealing gap, by integrating the proximity sensors in the stationary ring. The experimental investigations concerning film thicknesses, pressure distributions in the gas film and axial vibrations are carried out in an industry DGS up to 50 bar and 10,000 rpm, whereby a good insight into the dynamic behaviour of the sealing gap is provided. The results demonstrate the practicability of obtaining the gas film parameters in a grooved gas seal, bridging the gap between theory and practice. In combination with the experimental work presented in this paper, the numerical model for simulating the seal performance programmed in MATLAB is compared and validated. The comparisons for various operating conditions and groove profiles are discussed with the focus lying on the hydrodynamic effect in the gas film.

Seismic Response Characteristics of RCC Dams Considering Fluid-Structure Interaction of Dam-Reservoir System

In analysis of different types of dams, i.e. arch, gravity, rockfill and Roller Compacted Concrete (RCC) dams, the effect of hydrodynamic water pressure as an effective factor must seriously be taken into consideration. In present study, the hydrodynamic effect is precisely deliberated in RCC dams and compared to hydrostatic pressure effect. For this purpose, Kinta RCC dam in Malaysia is selected and 2D finite element (FE) model of the dam is performed. The Lagrangian approach is used to solve the dam-reservoir interaction, fluid–structure interaction (FSI), and in order to evaluate the crack pattern, Concrete Damaged Plasticity (CDP) model is implemented. Comparisons show that hydrodynamic pressure significantly changes the dam behaviour under seismic excitations. Moreover, the hydrodynamic effect modifies the deformation shape of the dam during the ground motions, however, it increases the magnitudes of the developed stresses causing more extensive tension crack damages mostly in the heel and upstream zones of the dam.