Undisturbed Level Research Articles

LONG-WAVE MODELS FOR A COUNTERCURRENT FLOW OF LIQUID FILM AND TURBULENT GAS FLOW

The paper considers the countercurrent flow of a vertically falling liquid film and a turbulent gas. In the case of small Reynolds numbers and when certain conditions for the characteristics of such a flow are met, the problem is reduced to one model equation for the film thickness. For long-wave weakly nonlinear disturbances, various nonlinear integrodifferential equations are obtained from this equation for the deviation of film thickness from the undisturbed level. Their specific type depends on the values of the magnitude of one parameter. This parameter is the ratio of the friction force from the side of the gas acting on the unperturbed film flow to the force of gravity. It is shown that, in addition to the countercurrent flow, such models also appear in a number of other gas-film flows. Both their radical differences and some common features are discussed. Several universal solutions of these model equations are presented.

控水与补水条件下连续热浪对闽楠光合特性和生长速率的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 控水与补水条件下连续热浪对闽楠光合特性和生长速率的影响 DOI: 10.5846/stxb202201190183 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目(32171749,31800512);国家重点研发计划子课题项目(2016YFD0600603-2);福建省种业创新与产业化工程项目(ZYCX-LY-202102) Influences of multiple successive heat waves combined with water control and supplement on photosynthetic characteristics and growth rate of Phoebe bournei seedlings Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:全球变暖背景下,亚热带地区极端气候热浪事件发生频率持续增加。高频热浪及其伴随的高温和干旱复合胁迫将严重影响植物的光合特性,抑制植物的生长,甚至造成死亡。然而,目前亚热带树木光合特性及生长对高频热浪及复合胁迫的响应仍不明确。以亚热带阔叶树种闽楠苗木为研究对象进行了热浪模拟实验,关注了补水和控水处理不同水分环境下连续热浪对闽楠光合特性及生长速率的影响。结果表明,补水处理下闽楠净光合速率(Pn)在单次热浪影响下显著下降了34%,同时水分利用效率显著(WUE)下降,但蒸腾速率(Tr)、气孔导度(Gs)和叶片水汽压亏缺(Leafvpd)显著上升(P<0.05)。表明水分充沛的高温环境中闽楠可通过增加蒸腾耗水加速水分蒸散来调节叶片的温度,增强植株光合特性对热浪的抗性。而控水处理下单次热浪处理组Tr和Gs未显著上升,以及Tr与Leafvpd在干湿环境下线性拟合的不同斜率,说明水分胁迫会降低叶片降温的效率,加剧热浪对闽楠光合特性的影响。水分和高温的复合胁迫还延长了闽楠光合特性在热浪后的恢复过程,高温胁迫下闽楠Pn在15 d后恢复至未干扰水平,但复合胁迫组未能恢复。此外,连续发生的热浪存在累加效应,表现为降低闽楠对热浪的抗性,其中闽楠Tr、Gs和WUE在连续热浪处理组变化显著(P<0.05)。但连续发生的热浪事件不会显著影响闽楠光合特性在热浪后的恢复过程,且会增加闽楠的高度,补水处理下连续热浪处理组闽楠苗高相对生长率显著高于其它处理组,但地径相对增长率未见显著差异。该研究结果表明,热浪阶段的水分供给可以增强亚热带树种闽楠的热浪抗性,并加速恢复,但控水处理的干环境下闽楠热浪抗性下降,若该环境下连续热浪事件发生可能增加闽楠苗木死亡的概率。因此,植物对气候变化响应的研究应该增强对复合胁迫或极端气候模式变化的关注。 Abstract:Under the background of global warming, the frequency of extreme climatic heat wave events continues to increase in subtropical region. The high frequency heat wave events severely reduced plants photosynthetic properties, especially when the combined thermal and drought stresses occurred, it will inhibit plant growth, and further lead to plant mortality. However, the response of subtropical tree species photosynthetic characteristics and growth to high-frequency heat waves and their complex stresses is still unclear. In this study, we created a heat wave simulation experiment on subtropical tree species, Phoebe bournei, focusing on the influences of heat waves on the photosynthetic characteristics and growth rates with or without water supplement during heat waves. The results showed that the single heat wave event in wet environment with water supply can resulted in 34% decrease in net photosynthetic rate (Pn) and also decrease in water use efficiency (WUE), but transpiration rate (Tr), stomatal conductance (Gs) and leaf vapor pressure deficit (Leafvpd) showed significant increase (P<0.05). This indicates that the Phoebe bournei in sufficient water environment can regulate leaf temperature via accelerating the water evapotranspiration consumption under high temperature stress, which could enhance the resistance of plant photosynthetic characteristics to heat waves. However, there was no significant increase in Tr and Gs in the single heat wave treatment group in drought habitat without water supplement, as well as the different slopes of the linear fit between Tr and Leafvpd in dry and wet environments. It suggests that without water supply, heat waves can cause drought stress, reduce the efficiency of leaf cooling, and exacerbate the effect of heat wave on photosynthetic characteristics of Phoebe bournei. The combined drought and high temperature stress also prolonged the recovery process of Phoebe bournei photosynthetic characteristics after heat wave, while Pn recovered to the undisturbed level at 15 days later after heat wave influences, but failed to recover in the combined stress group. In addition, there was a cumulative effect when successive heat wave occurred, which showed a reduction of Phoebe bournei resistance to heat waves, evidenced by the significant variation (P<0.05) of Tr, Gs and WUE during multiple successive heat wave events. But the multiple successive heat wave events did not significantly influence the recovery process of photosynthetic characteristics after heat wave, even caused an increasing of plant height. Under the wet environment with water supply, the Phoebe bournei seeding height relative growth rate of cumulative effect of continuous heat wave was significantly higher than other treatments, but no significant difference was observed in the relative growth rate of ground diameter. Our results indicate that the subtropical tree species, Phoebe bournei, has a strong heat wave resistance in wet environment, but such resistance will largely reduce in dry environment, and the successive heat wave events may also increase the probability of seedling mortality in dry environment. Therefore, studies of plant response to climate change should pay more attention on compound environment stresses or changes in extreme climate patterns. 参考文献 相似文献 引证文献

Experimental study on local scour around a forced vibrating pipeline in unidirectional flows

The interaction between a forced vibrating pipeline and an erodible seabed in unidirectional flows is experimentally investigated. The experiments were conducted under clear-water scour conditions with a water depth of 0.3m and averaged approach velocity of 0.261 m/s. The pipeline model with a diameter ( D ) of 3.5 cm, was subjected to a vertical sinusoidal motion of varying amplitudes ( A 0 = 2∼6 cm) and frequencies ( f 0 = 0.1–0.6Hz). The initial gap ( G 0 ) between the lower pipe surface and the undisturbed flatbed level was fixed at 1 D . The results show that the maximum scour depth increases significantly with both vibration amplitude and frequency, with the former having a more dominant influence. However, frequency tends to exacerbate the scour hole development more in the early scour stage. Distinct scour mechanisms are observed based on the different combinations of vibration amplitude and frequency. In the high A 0 conditions ( A 0 > G 0 ), the combined effect of pounding (when the pipe hits the seabed) and piston actions (rising and falling of the pipe) during the pipe descending period dominates the earlier stages of scouring, and the pick-up of sediment particles during its rising period controls the subsequent scour process. In the low A 0 conditions ( A 0 < G 0 ) when pounding does not occur, vortex shedding during the pipe-falling stage controls the development of scour hole when the frequency is low. When the frequency is high, however, the flow field associated with the pipe-rising period dominates the scour development. Different empirical formulas for the prediction of the maximum scour depth and width are proposed and compared in the present study. • 2 and 3 scour stages with different scour mechanisms are identified for the low and high amplitude conditions, respectively. • The pounding effect, which is related to pipeline-scour subjected to forced vibration, is discussed. • Vibration amplitude has a dominant influence on the maximum scour depth while frequency influences the early scour stages.

HF01-15 FIRST SEX - THE NATUFIAN STATUE

You have accessJournal of UrologyCME1 May 2022HF01-15 FIRST SEX - THE NATUFIAN STATUE Nikil Sairam, and Michael Moran Nikil SairamNikil Sairam More articles by this author , and Michael MoranMichael Moran More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002541.15AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: The hunter-gatherer’s who eked out a tenuous survival strategy during the last phases of the Bolling-Allerod Epipaleolithic period certainly procreated. These pre-literate peoples are the first to demonstrate sexual practices in artwork millennia prior to written language. The British movie of 1966 starring Raquel Welch as Loana, One Million Years BC failed to capture the sexuality of the caveman and cavewoman as well as this actual sculpted piece. METHODS: Much of the published writings on or about the Natufian cultures were gathered and utilized to better understand the sexual practices of these peoples. Dorothy Garrod (1892-1968) famed daughter and only surviving child of Archibald Garrod was the discoverer of the Natufian culture and peoples in 1928. Her mentor, Abbé Henri Breuil discovered a rare calcite statue, known as the “Ain Sakhri’ figurine that dates roughly to 9,000 BCE and identified by him to be Garrod’s Natufian culture. RESULTS: The figurine has undergone extensive investigations and was created upon a calcite cobble. It was sculptured to show a couple in coitus as well as being a phallic illustration. The artist utilized a pointed, probable stone chisel to remove pieces and make the delicate, copulating figures. The two entwined figures are locked in a forever intimate coital scene, presumably a female and a male, arms and legs wrapped around one another in a sitting position. CONCLUSIONS: The origin of human sexuality is linked to the development of mankind itself, well documented by modern genetic paleoanthropological investigations into mitochondrial Eve and Y-chromosome Adam. The hominin lineage has recently experienced a modern Renaissance with rapid expansion in our knowledge about the evolution within Africa, correctly hypothesized by Charles Darwin. …”the statuette…had never been above ground, where it would have faded and worn away; on the contrary it bore ash marks, evidence of an existing undisturbed level, but no of clay as it would have been the case if in a cave.” Eminent social anthropologists believe that sex cannot be understood except through its social and political setting may apply to primitive civilizations that have been studied in the modern era, but these rules have difficult applications to the paleolithic era. So little is known about the ancient Natufian culture that is pre-pottery, pre-literate, pre-metallurgy but obviously not pre-sexual or erotic. Source of Funding: None © 2022 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 207Issue Supplement 5May 2022Page: e217 Advertisement Copyright & Permissions© 2022 by American Urological Association Education and Research, Inc.MetricsAuthor Information Nikil Sairam More articles by this author Michael Moran More articles by this author Expand All Advertisement PDF DownloadLoading ...

Influence of low-frequency variability on groundwater level trends

Estimating groundwater level evolution is a major issue in the context of climate change. Groundwater is a key resource and can even account in some countries for more than half of the water supply. Groundwater trend estimates are often used for describing this evolution. However, the estimated trend obviously strongly depends on available time series length, which may be caused by the existence of long-term variability of groundwater resources. In this paper, using a groundwater level database in Metropolitan France as an example, we address this issue by exploring how much trend estimates are sensitive to low-frequency variability of groundwater levels. Database consists of relatively undisturbed groundwater level time series regarding anthropogenic influence (water abstraction by either continuous or periodic pumping). Frequent changes in trend direction and magnitude are detected according to time series length, which can eventually lead to contradictory interpretations of the groundwater resource evolution, as presented in first part of this article. To assess whether low-frequency variability – known to originate from climate variability – can induce such modifications of trends, we explored in a second step the multi-time scale variability of groundwater levels using a methodology based on discrete wavelet transform. Most of the time series displaying changing trends depending on time series length corresponded to aquifers with high-amplitude low-frequency variability of groundwater levels. Two predominant low-frequency components were detected: multi-annual (∼7 years) and decadal (∼17 years). We finally examined how much those two low-frequency components may affect trend estimates on the longer time period available. For this purpose, we individually removed each of both components from the original times series by discrete wavelet filtering and re-estimated trends in the filtered groundwater level time series. The results showed that the groundwater level trends were highly sensitive to the presence of any of these low-frequency components, which may then strongly influence the estimated trends either by exaggerating or mitigating them. These results emphasize that i) attributing the estimated trends only to climate change would be hazardous given the large influence of low-frequency variability on groundwater level trends, ii) estimation of trends in hydrological projections resulting from General Circulation Models (GCM) outputs in which low-frequency variability is not well represented would be subject to strong uncertainty, iii) a potential change in the amplitude of internal climate variability – e.g. increasing or decreasing low-frequency variability – in the next decades may lead to substantial changes in groundwater level trends.

Transverse flow-induced vibrations of a sphere in the proximity of a free surface: A numerical study

In this paper, we present a numerical study on the transverse flow-induced vibration (FIV) of an elastically mounted sphere in the vicinity of a free surface at subcritical Reynolds numbers. We assess the interaction dynamics and the vibration characteristics of fully submerged and piercing spheres that are free to vibrate in the transverse direction. We employ the recently developed three-dimensional two-phase flow–structure interaction solver to investigate fully and partially submerged configurations of an elastically mounted sphere. To begin, we examine the vortex-induced vibration (VIV) phenomenon and the vortex-shedding modes of a fully-submerged sphere vibrating freely in all three spatial directions. We systematically verify and analyze the mode transitions and the motion trajectories in the three degrees-of-freedom (3-DOF) for the Reynolds number up to 30000. We next simulate the transversely vibrating (1-DOF) full-submerged sphere over a wide range of reduced velocities 3≤U∗≤20, whereby the reduced velocity is adjusted by changing the freestream Reynolds number. The VIV response amplitude and the topology of the wake structure are compared with the measurements for the mode I and mode II response branches. We further look into the effect of the free surface on the FIV response of a transversely vibrating sphere in the proximity of a free surface. The response dynamics of the sphere is studied for three representative values of normalized immersion ratio (h∗=h∕D, where h is the distance from the top of the sphere to undisturbed free-surface level and D is the sphere diameter), at h∗=1 (fully submerged sphere with no free-surface effect), h∗=0 (where the top of the sphere touches the free surface) and h∗=−0.25 (where the sphere pierces the free surface). At the lock-in range, we observe that the amplitude response of the sphere at h∗=0 is decreased significantly compared to the case at h∗=1. It is found that the vorticity flux is diffused due to the free-surface boundary and the free surface acts as a sink of energy that leads to a reduction in the transverse force and amplitude response. When the sphere pierces the free surface at h∗=−0.25, the amplitude response at the lock-in state is found to be greater than all the submerged cases studied with the maximum peak-to-peak amplitude of ∼2D. We find that the interaction of the piercing sphere with the air–water interface causes a relatively large surface deformation and has a significant impact on the synchronization of the vortex shedding and the vibration frequency. The streamwise vorticity contours and pressure distribution are employed to understand the VIV characteristics and wake dynamics. Increased streamwise vorticity gives rise to a relatively larger transverse force to the piercing sphere at h∗=−0.25, resulting in greater positive energy transfer per cycle to sustain the large-amplitude vibration. Lastly, we study the sensitivity of large-amplitude vibration on the mass ratio, m∗, and, Froude number, Fr, at the lock-in state.

Influence of water area depth on wind waves

A semi-empirical technique for calculating the parameters of wind waves at variable sea depths along the wind acceleration has been developed and presented. This technique allows you to determine the average values of wind wave heights, their length and period depending on the wind velocity, taking into account and without taking into account the heaping of water by wind. Within the framework of the described method, the calculations of wind wave parameters suitable for isobaths d = 20 m were performed for a specific study area of the Bistre (Novostambulske) branch of the Danube estuary, for the north-eastern and eastern wind directions. Numerical simulations were performed for the Black Sea in the location of the protection dam of the Maritime approach channel of the Danube-Black Sea deep-sea navigation. Numerical calculations of wind wave transformation in the water area near the protection dam for the most dangerous wind directions in stormy conditions were performed. For mathematical simulation, the maximum values of wind velocity and wave height were used, which were observed during the whole period of research of the Black Sea water area in the region of the dam. Within the framework of refraction theory, wave transformation calculations have been performed for the most wave-hazardous wind acceleration directions, namely, the north-eastern and eastern wind directions. It is shown that taking into account the heaping of water by wind leads to an increase in the parameters of gravitational waves. The results of numerical simulations have shown that with the increase of wind acceleration exceeding the limit values, the parameters of the waves reach constant values. These values depend on the bathymetry of the seabed, wind velocity and direction. It was found that the increase in the deviation of the free surface of the sea from the undisturbed level significantly depends on the heaping of water by wind. It was found that the relative increase in the wave parameters is observed higher in the east wind direction than in the northeast wind direction in the study area of the Black Sea.

Modeling wave modes for a countercurrent flow of film and turbulent gas

In this paper, wave modes are modeled for a countercurrent flow of vertically falling liquid film and turbulent gas. In the case of small Reynolds numbers for long wave perturbations, the problem is reduced to a nonlinear integro-differential equation for the film thickness deviation from the undisturbed level. Solutions of this model equation are studied. Several typical scenarios for the evolution of periodic perturbations are presented

Evaluation of hydrogeological impact of tunnel engineering in a karst aquifer by coupled discrete-continuum numerical simulations

Anthropogenic disturbance of karst groundwater systems by large-scale underground engineering activities is an important topic but is difficult to address due to the compound influence of the heterogeneity and construction progression. In this study, we adopt the coupled discrete-continuum modeling approach where both the tunnels and karst conduits are treated as discrete channels. Based on extensive site characterization, groundwater observations, and tunnel discharge data, we establish a three-dimensional coupled model for a karst aquifer where deeply-buried, long tunnels are being constructed. We perform high-resolution simulations to quantitatively evaluate the spatial and temporal characteristics of the tunnel construction impact on a karst groundwater system. The simulation results satisfactorily reproduce the tunnel discharge time-series. We show that the excavation and lining schedule is an important factor to consider when evaluating the hydrogeological impact. During tunnel construction, the groundwater drainage through the tunnels (5.3 × 107 m3) accounts for a significant part of the total groundwater discharge (~11%) in the studied area. The continuous water influx to the tunnels results in widespread drawdown with an area of impact (with drawdown >5 m) covering 64.0% of the entire study area after four years of construction. The total discharge through karst conduits decreases by about 30% in response to the tunnel construction. Our simulation results predict that after completion of lining the groundwater system will slowly approach a groundwater level 5–10 m below the undisturbed level. This work demonstrates the use of coupled discrete-continuum models to study regional groundwater flow in karst aquifers affected by tunnel engineering activities and also provides a guidance for the impact assessment of other underground engineering projects in mining and transportation industries. The simulation methodology may be exploited for optimization of the construction plans to minimize hydrogeological impact and to ensure construction safety.

Simulating waves on a horizontal liquid film entrained by a gas flow

Nonlinear waves on a horizontal liquid film surface are considered. The effect of adjacent gas flow is taken into account through the data on shear stress at the film-gas interface obtained by the Boussinesq model of turbulence. A model nonlinear equation for the film thickness deviation from the undisturbed level is used to simulate nonlinear wave modes. Weakly nonlinear steady-state travelling solutions of this equation with wave numbers located in the vicinity of neutral wave numbers are constructed analytically. The evolution of periodic perturbations with wave numbers lying in the depth of the linear instability region is also considered numerically. Several typical scenarios of their evolution have been identified.

Pattern of forest recovery and carbon stock following shifting cultivation in Manipur, North-East India.

Shifting cultivation has resulted in large-scale deforestation and forest degradation in the tropics; however the abandoned fallows are known to have high potential for carbon capture. The paper is an attempt to determine the forest recovery patterns following shifting cultivation by evaluating the tree species composition, diversity and abundance with respect to topographical factors in Manipur, India. We also used ordination analysis to understand the change in species composition with regard to environmental variables. The living woody biomass carbon of each fallow was quantified, and the factors affecting the recovery of carbon stock along an increasing fallow gradient was assessed. Our results showed that the species richness and basal area recovered relatively with time since abandonment, and the north-facing lower elevation fallow sites displayed higher species richness and stem density than those in higher elevations. Environmental variables had no impact on the regeneration of Elaeocarpus floribundus Blume and Castanopsis hystrix Hook. f. & Thomson ex A. DC. which suggests that they may be capable of effective restoration of degraded forest areas. As these species appear naturally in the forests, it would facilitate quicker rehabilitation and reinstate the soil nutrients making the soil reusable in a short term. We also found that fallow age plays a vital role in recovering above-ground biomass carbon from living woody species followed by the aspect of the site. The total living woody biomass carbon ranged from 0.98 Mg ha-1 in 5 years fallow to 142.58 Mg ha-1 in 20 years fallow. The above-ground biomass carbon recovery of the oldest fallow was 39% to 40% of the reference undisturbed forest and the estimated time for the shifting cultivation fallows to reach that of the undisturbed forest level was approximately 39 years to 41 years.

Stress distribution in column-plate foundations of Monument of Christ The King erected in Świebodzin

The paper presents results of numerical simulations of the stress distribution and deformations within of foundations of huge monument of Christ The King erected in Świebodzin (Poland) in 2010. It is 3 meters taller than the better known statue of Christ the Redeemer in Rio de Janeiro, standing at 30.1 meters tall without its pedestal. Foundations were built as a system of reinforced concrete columns and slabs which can be classified as a spatial column-slab system. Actual mechanical parameters of the substrate and of the artificial mound made of field stones, sand, gravel and clay were adopted in calculations. The numerical simulations of structural members of foundation and determination of the stress distribution are presented in the article. Monument itself was not included into the model. Instead of it the rigid cantilever was introduced to which resultant forces were applied. Three different stages were distinguished: the initial state after foundation and mound accomplishment, the initial state plus the dead load and the initial state plus the dead load and the wind load. It was assumed that the wind load was taken into account in a quasi-static formulation by applying the equivalent horizontal force and the torque. Stresses and displacements for these three stages were determined by Finite Element Method using Simulia ABAQUS system. It was disclosed what was a contribution of particular parts of foundations in sustaining loads in considered load cases. The state of exertion of structural members of foundations and the soil itself was assessed. It was showed that the column-slab foundations and soils of the mound play important role in taking loads of the statue, spreading them and safe transferring to the undisturbed level of natural soils. According to the numerical simulations results the columns of foundation take as much as 64% of the vertical load (in the most unfavourable load conditions). At the same time soils of the mound take through the side surface of piles about 20 % of the vertical load.

Evaluation of automated groundwater level measurements for transmissivity and storativity calculation

Abstract In this paper, we discuss the accuracy of aquifer transmissivity (T) and storativity (S) values, obtained through the processing of hourly and 5-min groundwater level data, regularly and accurately recorded by automated stations. In particular, we discuss the role of the selection of (a) the initial undisturbed hydraulic head level, which might be influenced by prior pumping cycles, and (b) the exact time of start or shutdown of the pump, which might not be exactly recorded. Furthermore, the accuracy of T and S values based on sparse measurements is also examined. The Cooper–Jacob method and the recovery test method have been applied to obtain both T and S, and T values, respectively. Groundwater level measurements at Moudania aquifer, Chalkidiki, Greece, are used as an illustrative example. Our main conclusions are (a) assuming that pumping starts earlier than it actually does, leads to the underestimation of T and the overestimation of S, (b) transmissivity might be overestimated if the residual drawdown, due to previous pumping cycles, is substantial, (c) in recovery tests, the deviation of the straight line that fits the experimental points from the point (1,0) is an indication of residual drawdown, and (d) sparse measurements can offer reasonable estimates.

Extreme Field-Aligned Currents during Magnetic Storms of the 24th Solar Cycle: March 2015 and September 2017

Characteristics of field-aligned currents (FACs) obtained from the observations of SWARM satellites during two strong magnetic storms in March 16–19, 2015 and September 6–9, 2017 are presented. The storms were accompanied by high-intensity substorms. Satellites crossed the dusk, noon, pre- and after midnight MLT sectors. It was shown that variations in FAC density and the latitudinal position of the equatorial FAC boundaries are controlled by both the development of the storm and, to a considerable degree, substorm activity. The average densities of downward and upward FACs reach 3–4 μA/m2 at a substorm’s peak, while the undisturbed level is about 0.2 μA/m2. The minimum latitude of equatorial FAC boundaries is limited to 50° MLat. Large-scale FACs consist of small-scale filamentary structures with high current density, which are always present in SWARM observations. Small-scale peak currents with a density of 50–100 µA/m2 appear during periods of a general increase in density during activation of substorms. Local increases in concentration and temperature of electrons show that the current structure can be associated with a mesoscale discrete auroral arc.

Studying the topological structure of steady-state travelling solutions for the model of film flow of a viscous fluid entrained by a gas flow

The article studies nonlinear waves on a liquid film, flowing under the action of gravity in a known stress field at the interface. In the case of small flow rates for the long-wave modes, the problem is reduced to solving a nonlinear equation for the film thickness deviation from the undisturbed level. The paper presents the results of calculations for this model equation of families of steady-state travelling periodic solutions. For these families, the limiting solutions, solitary waves, have been found. It is also investigated how the topological reorganization of such families occurs with a smooth change in the degree of influence of the gas flow. It is shown that although the eigenform of specific solitons changes smoothly, for certain values of the problem parameter for a particular family an abrupt change in the shape of its limiting soliton occurs.

A small-mode model for spatial regimes on a freely falling liquid film

Spatial wave modes of a viscous liquid film freely flowing down a vertical wall are considered. In the case of small Reynolds numbers the problem is reduced to considering solutions of a nonlinear equation for the film thickness deviation from the undisturbed level. It was used to obtain a model system of equations, describing spatially periodic solutions with wave numbers lying in the vicinity of special resonance points and symmetric in the transverse coordinate. Several solutions for this system are provided.

A global vertical datum defined by the conventional geoid potential and the Earth ellipsoid parameters

The geoid, according to the classical Gauss–Listing definition, is, among infinite equipotential surfaces of the Earth’s gravity field, the equipotential surface that in a least squares sense best fits the undisturbed mean sea level. This equipotential surface, except for its zero-degree harmonic, can be characterized using the Earth’s global gravity models (GGM). Although, nowadays, satellite altimetry technique provides the absolute geoid height over oceans that can be used to calibrate the unknown zero-degree harmonic of the gravimetric geoid models, this technique cannot be utilized to estimate the geometric parameters of the mean Earth ellipsoid (MEE). The main objective of this study is to perform a joint estimation of W0, which defines the zero datum of vertical coordinates, and the MEE parameters relying on a new approach and on the newest gravity field, mean sea surface and mean dynamic topography models. As our approach utilizes both satellite altimetry observations and a GGM model, we consider different aspects of the input data to evaluate the sensitivity of our estimations to the input data. Unlike previous studies, our results show that it is not sufficient to use only the satellite-component of a quasi-stationary GGM to estimate W0. In addition, our results confirm a high sensitivity of the applied approach to the altimetry-based geoid heights, i.e., mean sea surface and mean dynamic topography models. Moreover, as W0 should be considered a quasi-stationary parameter, we quantify the effect of time-dependent Earth’s gravity field changes as well as the time-dependent sea level changes on the estimation of W0. Our computations resulted in the geoid potential W0 = 62636848.102 ± 0.004 m2 s−2 and the semi-major and minor axes of the MEE, a = 6378137.678 ± 0.0003 m and b = 6356752.964 ± 0.0005 m, which are 0.678 and 0.650 m larger than those axes of GRS80 reference ellipsoid, respectively. Moreover, a new estimation for the geocentric gravitational constant was obtained as GM = (398600460.55 ± 0.03) × 106 m3 s−2.

A simple SPH model of a free surface water wave pump: waves above a submerged plate

ABSTRACTIn this work, the SPH method is used in 2D to evaluate the pump characteristics of free surface water waves above a submerged plate. The configuration considered here consists of an infinite wave train reaching a rectangular plate of length and thickness submerged under the undisturbed water level. The numerical method is validated against experimental results with good agreement. The mean Eulerian mass flux is evaluated in the simulation and outlines the importance of the wave mass transport in the circulation around the submerged plate. It is observed an increase of the mass flux in the surface layer (wave mass transport) as predicted by the water waves linear theory. The incident wave frequency and height are varied and the flow rate is evaluated and compared to the linear model. To study the pump response, a gate valve is placed at the center position under the submerged plate. The fully open gate configuration corresponds to the experimental case. Pump curves are provided. The maximum dynamic pressure efficiency is evaluated to be for the present configuration.

On the geoid and orthometric height vs. quasigeoid and normal height

Abstract The geoid, but not the quasigeoid, is an equipotential surface in the Earth’s gravity field that can serve both as a geodetic datum and a reference surface in geophysics. It is also a natural zero-level surface, as it agrees with the undisturbed mean sea level. Orthometric heights are physical heights above the geoid,while normal heights are geometric heights (of the telluroid) above the reference ellipsoid. Normal heights and the quasigeoid can be determined without any information on the Earth’s topographic density distribution, which is not the case for orthometric heights and geoid. We show from various derivations that the difference between the geoid and the quasigeoid heights, being of the order of 5 m, can be expressed by the simple Bouguer gravity anomaly as the only term that includes the topographic density distribution. This implies that recent formulas, including the refined Bouguer anomaly and a difference between topographic gravity potentials, do not necessarily improve the result. Intuitively one may assume that the quasigeoid, closely related with the Earth’s surface, is rougher than the geoid. For numerical studies the topography is usually divided into blocks of mean elevations, excluding the problem with a non-star shaped Earth. In this case the smoothness of both types of geoid models are affected by the slope of the terrain,which shows that even at high resolutions with ultra-small blocks the geoid model is likely as rough as the quasigeoid model. In case of the real Earth there are areas where the quasigeoid, but not the geoid, is ambiguous, and this problem increases with the numerical resolution of the requested solution. These ambiguities affect also normal and orthometric heights. However, this problem can be solved by using the mean quasigeoid model defined by using average topographic heights at any requested resolution. An exact solution of the ambiguity for the normal height/quasigeoid can be provided by GNSS-levelling.

Formation of red arc in the polarization jet band

Complex optical and ionospheric measurements in the region of the formation of red arcs accompanying the polarization jet development are analyzed. Optical measurements were done at subauroral station Maimaga, and ionospheric measurements were fulfilled at subauroral stations Yakutsk and Zhigansk. Spatial location and intensity of red-arcs were detected by the meridional scanning photometer. The temperature of the neutral atmosphere was recorded by Fabry-Perot interferometer. It is shown that the temperature of the neutral atmosphere increases in the red arc region and changes in accordance with variations in the emission. On 02 December 1989 the neutral temperature increased by 500 K in the red arc relative to the undisturbed level determined for quiet days during the month. This evidences on the strong heating process in the red arc region. According to ionospheric and satellite data on 18 February 1999 the red arc was observed simultaneously with polarization jet development – fast westward plasma drift in the poleward electric field. The magnitude of this electric field was 50–80 mV/m. Due to frictional interaction of ions and neutrals, ions were heated up to 5000–6000 K and neutrals gain energy of some hundreds degrees.