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This study employs an incompressible homogeneous flow framework with a transport-equation-based cavitation model and shear stress transport turbulence model to successfully reproduce the unsteady cavitating flow around a three-dimensional hydrofoil. Cavity growth, development, and break-off during the periodic shedding process are adequately reproduced and match experimental observations. The predicted shedding frequency is very close to the experimental value of 23 ms. By monitoring the motions of the seeding trackers, growth-up of attached cavity and dynamic evolution of U-type cavity are clearly displayed, which indicating the trackers could serve as an effective tool to visualize the cavitating field. Repelling Lagrangian coherent structure (RLCS) is so complex that abundant flow patterns are highlighted, reflecting the intricacy of cavity development. The formation of cloud cavities is clearly characterized by the attracting Lagrangian coherent structure (ALCS), where bumbling wave wrapping the whole shedding cavities indicates the rotating transform of cavities, and stretching of the wave eyes shows the distortion of vortices. Generation of the re-entrant jet is considered to be not only associated with the adverse pressure gradient due to the positive attack angle but also the contribution of cloud cavitating flow, based on the observation of a buffer zone between the attached and cloud cavities.

The physical mechanism leading to flame local extinction remains a key issue to be further understood. An analysis of large eddy simulation (LES) data with presumed probability density function (PDF) based closure (Chen et al., 2020, Combust. Flame, vol. 212, pp. 415) indicated the presence of localised breaks of the flame front along the stoichiometric line. These observations and their relation to local quenching of burning fluid particles, together with the possible physical mechanisms and conditions allowing their appearance in LES with a simple flamelet model, are investigated in this work using a combined Lagrangian-Eulerian analysis. The Sidney/Sandia piloted jet flames with compositionally inhomogeneous inlet and increasing bulk speeds, amounting to respectively 70 and 90% of the experimental blow-off velocity, are used for this analysis. Passive flow tracers are first seeded in the inlet streams and tracked for their lifetime. The critical scenario observed in the Lagrangian analysis, i.e., burning particles crossing extinction holes on the stoichiometric iso-surface, is then investigated using the Eulerian control-volume approach. For the 70% blow-off case the observed flame front breaks/extinction holes are due to cold and inhomogeneous reactants that are cast onto the stoichiometric iso-surface by large vortices initiated in the jet/pilot shear layer. In this case an extinction hole forms only when the strain effect is accompanied by strong subgrid mixing. This mechanism is captured by the unstrained flamelets model due to the ability of the LES to resolve large-scale strain and considers the SGS mixture fraction variance weakening effect on the reaction rate through the flamelet manifold. Only at 90% blow-off speed the expected limitation of the underlying combustion model assumption become apparent, where the amount of local extinctions predicted by the LES is underestimated compared to the experiment. In this case flame front breaks are still observed in the LES and are caused by a stronger vortex/strain interaction yet without the aid of mixture fraction variance. The reasons for these different behaviours and their implications from a physical and modelling point of view are discussed in this study.

In Rayleigh‐Bénard convection, turbulent superstructures are large‐scale patterns of circulation rolls created by hot ascending and cold descending thermal plumes. The evolution of these large‐scale patterns happens on very large time scales τ. Spectral clustering applied to Lagrangian particle trajectories on time intervals smaller than τ can be used to create clusters displaying a structure similar to the patterns detected in the Eulerian frame of reference. However, this technique is unfeasible for the analysis of the evolution of turbulent superstructures due to turbulent dispersion. Therefore, we test the application of concepts of evolutionary spectral clustering on Lagrangian particle trajectories to analyze the long‐term dynamics of turbulent superstructures in the Lagrangian frame of reference.

The Bayueshan (BYS) tunnels are adjacent tunnels which comprise key engineering structures important for Yurong highway from Chongqing to Sichuan, China. The tunnels were established crossing over the old goafs of a coal mine. The tunnels have been damaged three times between 2014 and 2016. To evaluate the reasons for the damage, fast Lagrangian analysis of continua in three dimensions ( FLAC 3 D ) was used to simulate the underground coal-mine excavation yearly from 2012 to 2015. The simulation results show that the subsidence of the ground surface increased annually. The maximum subsidence of the left tunnel was 505 mm and that of the right tunnel was 512 mm. The excavation led to increase in the tunnels’ stress concentration. The simulations further show that uneven horizontal displacement and subsidence were the major factors in inducing tunnel construction defects. Poor geological conditions, water, and vehicle dynamic loads were also important factors that induced damage. Several engineering suggestions for ways to maintain the tunnels are given in this paper, and the research provides a reference for safety evaluation for tunnels crossing over an old goaf.

It is important to guarantee the safety of adjacent underground structures during the foundation pit blasting excavation of modern city construction. The blasting excavation construction of a large, deep foundation pit near an existing metro station of Guangzhou Metro Line 3 is used as the example in this study. Based on blasting vibration field test results, the influence of blasting dynamic load on the lining of an adjacent metro tunnel is numerically analyzed in simulation using Fast Lagrangian Analysis of Continua 3D (FLAC3D), and the relationships between the blasting vibration velocity and stress and the displacement of the metro tunnel lining are obtained. The results show that the stress of lining structure is within the allowable range under the experimental blasting conditions, the lining displacement increases linearly with the applied dynamic vibration velocity, and the vertical displacement of the lining is more obviously affected than the horizontal displacement by the dynamic load. This study can be used as a basis for the control of blasting vibration in a complex urban environment. Its practical application shows that the proposed blasting plan and parameters are reasonable and effective.

Warm conveyor belts (WCBs) are important airstreams in extratropical cyclones, often leading to the formation of intense precipitation and the amplification of upper-level ridges. This study presents a case study that involves aircraft, lidar and radar observations in a WCB ascending from western Europe towards the Baltic Sea during the Hydrological Cycle in the Mediterranean Experiment (HyMeX) and T-NAWDEX-Falcon in October 2012, a preparatory campaign for the THORPEX North Atlantic Waveguide and Downstream Impact Experiment (TNAWDEX). Trajectories were used to link different observations along the WCB, that is, to establish so-called Lagrangian matches between observations. To this aim, an ensemble of wind fields from the global analyses produced by the European Centre for Medium-RangeWeather Forecasts (ECMWF) Ensemble of Data Assimilations (EDA) system were used, which allowed for a probabilistic quantification of the WCB occurrence and the Lagrangian matches. Despite severe air traffic limitations for performing research flights over Europe, the German Aerospace Center (DLR) Falcon successfully sampled WCB air masses during different phases of the WCB ascent. The WCB trajectories revealed measurements in two distinct WCB branches: one branch ascended from the eastern North Atlantic over southwestern France, while the other had its inflow in the western Mediterranean. Both branches passed across the Alps, and for both branches Lagrangian matches coincidentally occurred between lidar water vapour measurements in the inflow of the WCB south of the Alps, radar measurements during the ascent at the Alps and in situ aircraft measurements by Falcon in the WCB outflow north of the Alps. An airborne release experiment with an inert tracer could confirm the long pathway of the WCB from the inflow in the Mediterranean boundary layer to the outflow in the upper troposphere near the Baltic Sea several hours later. The comparison of observations and ensemble analyses reveals a moist bias in the analyses in parts of the WCB inflow but a good agreement of cloud water species in the WCB during ascent. In between these two observations, a precipitation radar measured strongly precipitating WCB air located directly above the melting layer while ascending at the southern slopes of the Alps. The trajectories illustrate the complexity of a continental and orographically influenced WCB, which leads to (i) WCB moisture sources from both the Atlantic and Mediterranean, (ii) different pathways of WCB ascent affected by orography, and (iii) locally steep WCB ascent with high radar reflectivity values that might result in enhanced precipitation where the WCB flows over the Alps. The linkage of observational data by ensemble-based WCB trajectory calculations, the confirmation of the WCB transport by an inert tracer and the model evaluation using the multi-platform observations are the central elements of this study and reveal important aspects of orographically modified WCBs.

The Lagrangian analysis of particulate matter, biota and drifters, which are dispersed by turbulent fluid currents, is a cornerstone of oceanographic studies, covering diverse study objectives. The results of Lagrangian simulations and observations is predominantly visualised by means of easy-access plotting interfaces and simple presentation techniques. We analysed over 50 publications from the years 2010–2020 with respect to their visual design to deduce common visualisation practices in the domain. Individual figures are analysed towards adherence to visualisation best-practices, algebraic visualisation guidelines and the IPCC visual style guide. In this article, we present the resulting best-practices and common pitfalls in the design of Lagrangian ocean visualisations. Based on this visual study, we highlight that raising awareness of established visual guidelines may have a higher impact on improving the visual quality of publications in oceanography than the vigorous development of more general-purpose visualisation tools.

The present paper examines the northern stratosphere during April 2020, when the polar vortex split into two cyclonic vortices. We examine this split at middle as well as lower stratospheric levels...

Understanding moisture transport is crucial for understanding continental precipitation and extreme precipitation events, which are expected to become substantially more frequent under global warming conditions. In this work, the influence of major global moisture sources on extreme continental precipitation during the peak precipitation month is estimated and compared with climatological patterns. The results show a general change in the pattern of contribution of the primary source of precipitation (the source with the highest contribution) during extreme precipitation events. Most primary sources show a general reduction in their area of influence and a notable reduction in their contribution to the total precipitation. Agencia Estatal de Investigación | Ref. RTI2018‐095772‐B‐I0O Xunta de Galicia | Ref. ED481B 2018/062 Xunta de Galicia | Ref. ED431C 2017/64 Fundação para a Ciência e a Tecnologia

Excavating a tunnel in a deep and saturated ground affects the short- and long-term hydro-mechanical (H-M) response in the ground surrounding the opening. However, the interactions between transient pore pressure behavior and the corresponding deformation and stresses in the ground ahead of and behind the tunnel face are still not well understood. This paper investigates the transient H-M response of excavating a tunnel in a deep and saturated ground using a two-dimensional axisymmetric coupled model in the computer code Fast Lagrangian Analysis of Continua (FLAC). The tunnel was advanced in a stepwise excavation procedure consisting of undrained excavation and drained consolidation until the final tunnel face was reached. The final excavated face was then left to consolidate toward the steady-state condition. The main results of the paper are as follows: (1) when simulating a tunnel excavation in deep saturated ground using the convergence-confinement method, the unloading factors should be nonlinear and should consists of the mechanical unloading factor in the form of excavation force and the hydraulic unloading factor in the form of excavation pore pressure. These two unloading factors are necessary because the induced H-M response near the tunnel face is a rather transient response instead of an initial or final response. Moreover, it is observed that the pore pressure dissipation is not linear either with time or with distance to the tunnel face, (2) a relationship between the unloading factors and the distance to the tunnel face should then be established. This relationship is vital because it will provide the timing for tunnel support installation, and (3) the extrusion and the convergence of the advance core could be related through the proposed equations capturing the linear relationships between the face extrusion and its convergence as well as between the core extrusion and its pre-convergence. Through these relationships, the tunnel engineer may be able to estimate the magnitude of the deformation ahead of the face, which will subsequently allow control of the deformation behind the face.

In this paper, a seismic analysis of the Menta dam is briefly described. The Menta dam is a bituminous-faced rockfill dam located in Southern Italy, lying in the heart of Aspromonte Massif at an elevation of about 1400 m a.s.l. The embankment is about 90 m high at its deepest point, and the reservoir impounds 1.8 × 107 m3 of water. This dam was designed in the late seventies and built between 1987 and 2000. In the seismic analysis, the dam material has been modelled with an elasto-plastic constitutive law which is characterized by a Young’s modulus dependent on the stress level and on the distortional strain and by a curvilinear yielding surface. Both the calibration of the model and the dynamic analysis has been carried out by means of the FDM code FLAC (Fast Lagrangian Analysis of Continua [1]) version 8.1 which adopts an explicit time-integration scheme.

In loose or highly weathered rock slopes, the circular shear failure mechanism occurs in large scale. Most rock slope stability investigations ignore the influence of geometric parameters, i.e., failure surface entry point distance (le). This study presents failure surface determination based on constant element stress-based method. The failure surfaces and their sliding mechanism are analyzed first by using FLAC3D (Fast Lagrangian Analysis of Continua in three-dimension). A real case of instability corresponds to a loose rock is presented and its stability is determined by numerical analysis. To investigate the effectiveness of present method the influence of shear strength (c, φ) and geometric parameters (α, β) on the safety factor (FS) is also analyzed by using Geo5, FLAC3D and ABAQUS computer codes. Then, Geo5 and Statistical Package for the Social Sciences (SPSS) softwares were used to determine the effect of dimensionless parameter lambda (λ) on the failure surface entry point distance (le) and length of failure arc (L). The results show that shear failure may occur in non-homogeneous slope. Shear failure has exit and entry points situated either on the surface or near the toe of slope. The length of failure arc (L) is affected by the le and λ. Moreover, it can be acknowledged that the relation of both L and le with shear strength parameters (c, φ) is logarithmic, respectively. So, based on the rock strength parameters, L and le are predictable by using the equations derived from non-linear regression.

The characteristics of the movement of dynamic strata in combined open-pit and underground mining based on similar material simulation experiments were studied in this study. To get more accurate test parameters, a similar material, based on a sheet of brittle material, was developed. We then used the Anjialing coal mine as our case study sample. The characteristics for movement of dynamic strata and development of bed-separated fissure in working faces including 24,207, 24,208, and 29,210 were investigated by experimental simulation and numerical simulation, which was based on a similar simulation test system and Fast Lagrangian Analysis of Continua 3D (FLAC3D) statistical analysis software. Results from the experimental simulation demonstrated that the movement of dynamic strata during the mining process could be expressed as follows: underground mining → submerged rock → “arch-shaped” rock → “pit-type” subsidence region → perforation of slope fractures. When the working face 29,210 was advanced to the mining stop line, the overlying rock strata generally slid towards the slope with less separation cracking in the vertical direction. With the continuous advancement of working face 29,210 , the slope stress increased significantly and formed a slip surface or potential slip surface in the sloping rock. Moreover, the numerical analysis, similar material simulation experiment, and actual mining results were all similar, indicating that a similar material simulation experiment based on a sheet of brittle material well reflected the characteristics for the movement of dynamic strata in combined open-pit and underground mining.

The surface subsidence caused by coal mining is a large area, and computer simulation is a fast and intuitive method, which can help us understand the macroscopic subsidence law. The mined-out area left over by coal mining is not disposed of appropriately for a long time. Thus, it can easily cause ground subsidence, collapse, or spot cracking, especially when mining multiple coal seams, which seriously restricts the construction and safety of the near-surface rock and soil layers. Based on the engineering background of five-layer coal mining in the Beibu Coal Mine of Laiwu City, a “Fast Lagrangian Analysis of Continua in 3D” numerical calculation model was established. The model was used to analyze the surface deformation indexes of four groups with different mining sequences in multiple coal seams, revealing the sequence effects of mining time on the surface deformation law in the goaf collapse areas, hence obtaining optimal mining sequences. The results showed that the four groups of mining sequences (including vertical settlement and horizontal deformation) have stable surface deformation centers, but the deformation ranges and amounts are quite different. The settlement deformation is the main difference. Mining sequence I has the largest deformation of 62.7 cm, followed by mining sequence III. Mining sequences II and IV are basically the same, at only 22% of the value of mining sequence 1. A multi-index analysis of the surface deformation curve including the inflection point, stagnation point, and slope showed that the larger the surface deformation, the more evident the change of the curve (concave or convex) and slope, the more uneven the foundation stress, the more severe the damage to the surface structures, and the less suitable the surface construction. Finally, upon analyzing the indicators of surface stability and adaptability, mining sequence IV was indicated as the optimal scheme. It is suggested that an optimal mining sequence should be appropriately selected before the mining of multiple coal seams. The research results can provide effective guidance for addressing surface deformations under similar geological conditions, and can provide scientific evaluations for the safety and stability of surface buildings and structures, leading to considerable economic and social benefits.

The distribution of a plastic zone ahead of a gateroad plays a significant role in maintaining the long-term stability of mining spaces. For a long time, the principal stress field such as the values, the direction, etc. have been observed to have impacts on plastic zone development, but has not been looked into deeply and systematically. To this end, the influence of principal stress field including the maximum principal stress (P1), the angle between the P1 direction and the Z-axis (&alpha, ), the minimum principal stress (P3), and the ratio of maximum principal stress to minimum principal stress (P1/P3) on the expansion of the plastic zone ahead of the gateroad is investigated by the (Fast Lagrangian Analysis of Continua) FLAC3D models. The results show that: (1) The plastic zone volume increases first and then decreases with the increase of &alpha, and the direction of butterfly-shaped plastic zone ahead of gateroad is rotating with the evolution of &alpha, (2) The plastic zone volume ahead of excavation face increases gradually with the increase of P1/P3. Mutagenicity of butterfly-shaped plastic zone occurs ahead of the gateroad under a certain value of P1/P3. (3) With the increase of P1 and decrease of P3, the plastic zone volume is of exponential growth. The plastic zone volume approaches infinity when the critical value of maximum principal stress ([P1]) and the minimum principal stress ([P1]) is obtained. (4) The study of the effect of principal stress field on the expansion of plastic zone ahead of the gateroad is helpful for revealing the mechanisms of coal and gas outbursts. The critical stress state of butterfly-shaped plastic zone mutagenicity ahead of the gateroad can be used as an important indicator for assessing the risk of coal and gas outburst. The research can also guide the prevention of coal and gas outburst ahead of the gateroad.

In order to solve the problem of serious deformation and damage of surrounding rock under the complex stress environment of gob and residual coal pillar of overlying coal seam in China Coal Tashan Coal Mine, FLAC3D (Fast Lagrangian Analysis of Continua) numerical simulation is used to study the different excavation schemes of the return air chute in the near distance coal seam mining of Tashan Coal Mine, and finally determine to leave small coal pillar for excavation. Moreover, the correctness of the scheme is verified by monitoring the displacement changes of the roof and floor and the two sides of the roadway in the later stage. The results show that the failure depth of the roof of the 6-m or 8-m small coal pillar scheme is smaller than that of other schemes, and the roof is easier to maintain, which can effectively control the deformation and failure of the surrounding rock of the roadway. Considering the actual production problems such as air leakage in working face, an 8-m small coal pillar can be selected. The method of theoretical analysis, numerical simulation, and field measurement is feasible, which provides a reference for the engineering practice of roadway layout in close seam mining.

Uniaxial compressive strength (UCS) and peak strain (PS) are essential indices for studying the mechanical properties of coal and rock masses, and they are closely related to mechanical parameters such as the elastic modulus (E), Poisson’s ratio (υ), cohesion (C) and internal friction angle (Φ) of coal and rock masses. This study took the No. 2-1 coal seam of Zhaogu No. 2 Mine, in Henan Province, China, as the research object. An RMT-150B servo testing machine was used to test all mechanical parameters, including the E, υ, C and Φ of coal and rock masses. Based on the principle of orthogonal testing, Three Dimensions Fast Lagrangian Analysis of Continua (FLAC3D) was used to select E, υ, C, Φ, tensile strength (Rm) and dilation angle (Ψ) as initial participation factors. Using these six parameters and a five-level combination scheme (L25 (56)), the influence of coal mechanical parameters on UCS and PS was investigated, using the software SPSS for stepwise regression analysis, and a uniaxial pressure-resistant regression prediction equation was established. The research showed that, under uniaxial compression conditions, the main parameters controlling UCS of coal masses are C and Φ; conversely, the main parameters controlling PS are E and C. UCS and PS exhibit significant linear relationships with these main controlling parameters. Here, a stepwise regression prediction equation was established through reliability verification analysis using the main controlling parameters. This prediction method produces very small errors and a good degree of fit, thus allowing the rapid prediction of UCS. The precision of the stepwise regression model depends on the number of test samples, which can be increased in the later stages of a design project to further improve the precision of the projection model.

Accurate measurement of high-speed flows in the presence of elevated levels of shear and turbulence is a challenging yet necessary endeavor to understand ubiquitous flows that are of great engineering importance. While Eulerian methods, such as Particle Image Velocimetry, represent the traditional approach, Lagrangian alternatives, such as Particle Tracking Velocimetry, have witnessed a resurgence recently due to improved technology and interest in Lagrangian analysis methods. In this research, a recently developed implementation of a volumetric Lagrangian technique for tracking particles in densely seeded flows, namely, Multi-Pulse Shake-The-Box (MP-STB) with the specific implementation referred to as Four-Pulse Shake-The-Box is described and its performance in high-speed jet flows is evaluated. The MP-STB technique is based on recent developments in the Shake-The-Box method by Novara et al. (Experiment in Fluids 60(3):44, 2019) and uses low-speed cameras combined with a double-exposed image acquisition strategy and multi-pulse tracking. Its use of four laser pulses in quick succession with an uneven pulse timing scheme allows for high-accuracy estimates of velocity and acceleration, and repeated ensembles of short-duration, time-resolved measurements in realistic high-speed flows. Experiments with circular jets operating at exit Mach numbers of 0.31 and 0.59 in two different configurations, namely, free jets and jets impinging on a ground plate located 4.75 jet diameters away from the nozzle, were performed to evaluate MP-STB. Scattered four-particle tracks from MP-STB were mapped onto a regular Eulerian grid through the Fine Scale Reconstruction implementation of the VIC# data assimilation method by Jeon et al. (2018). Unique information, including acceleration fields, is presented for these well-known canonical flows. Comparisons with traditional Eulerian measurements from Tomographic PIV, Stereoscopic PIV, and planar PIV are provided to validate the accuracy and comparative cost of volumetric MP-STB measurements combined with the VIC# data assimilation technique.

The article presents the results of geodetic measurements and numerical modeling of mining area deformations in the partial exploitation area of the 712/1-2 seam at the Marcel Coal Mine. An important element in this exploitation is the limitation of the length of longwalls with cavings to 130 m and 150 m, leaving an unextracted 70 m wide coal solid belt between them. Leaving the belts aimed to reduce deformations of the mining terrain, with relatively limited deposit losses. The numerical modeling of mining terrain deformations was performed using the Fast Lagrangian Analysis of Continua (FLAC) software package based on the finite difference method. The results of the geodetic measurements and computer simulations presented in the article confirm the assumption adopted during the planning stage of this exploitation about the possible significant reduction of mining terrain deformations caused by leaving the unextracted belts of coal solid between successive longwall panels.

Various studies of retaining walls with relief shelves tend to rely on the proposition of reducing soil pressures behind the wall, according to the location and the width of relief shelf. The previous numerical studies did not predict the optimum reduction rate of earth pressure and the shape of failure mechanism. The finite-difference code fast Lagrangian analysis of continua is used to evaluate the active earth pressure behind a retaining wall with one relief shelf placed at different levels with a variable width. The soil behind the wall is modelled by an elastoplastic constitutive model with a Mohr–Coulomb yield criterion. The effects of soil non-associativity as well as the interface of soil–wall and relief shelf–soil are investigated. The reduction of earth pressure is estimated by the rate R, defined as the ratio of the reduced active thrust to the total active thrust of a wall without a relief shelf. The rate R is evaluated numerically and by using Klein’s solution. The obtained results enable determination of the appropriate position and width of the relief shelf to evaluate the optimum values of R.

Secondary ice production via rime-splintering is considered to be an important process for rapid glaciation and high ice crystal numbers observed in mixed-phase convective clouds. An open question is how rime-splintering is triggered in the relatively short time between cloud formation and observations of high ice crystal numbers. We use idealised simulations of a deep convective cloud system to investigate the thermodynamic and cloud microphysical evolution of air parcels, in which the model predicts secondary ice formation. The Lagrangian analysis suggests that the &ldquo, in-situ&rdquo, formation of rimers either by growth of primary ice or rain freezing does not play a major role in triggering secondary ice formation. Instead, rimers are predominantly imported into air parcels through sedimentation form higher altitudes. While ice nucleating particles (INPs) initiating heterogeneous freezing of cloud droplets at temperatures warmer than &minus, 10 ∘ C have no discernible impact of the occurrence of secondary ice formation, in a scenario with rain freezing secondary ice production is initiated slightly earlier in the cloud evolution and at slightly different places, although with no major impact on the abundance or spatial distribution of secondary ice in the cloud as a whole. These results suggest that for interpreting and analysing observational data and model experiments regarding cloud glaciation and ice formation it is vital to consider the complex vertical coupling of cloud microphysical processes in deep convective clouds via three-dimensional transport and sedimentation.

WOS:000510365700001; International audience; Coastal waters are subject to great environmental and anthropogenic pressures. The diffusion and the transport of these waters are a key element for environmental, ecological and economic management. There are numerous indicators of hydrological characteristics based on theories of transport time scale. However, these indicators strongly depend on the geographical shape of the studied area and tend to give information after long integration time periods, generally on the order of weeks. Here, to qualify a coastal area's dispersion more precisely, we combined two Lagrangian approaches and estimated a local diffusivity. This paper presents the numerical implementation and the results obtained over a tidally flushed, semi-enclosed water body located at mid-latitude. This new coefficient was estimated using the hydrodynamic model MARS 3D with a barycentric repositioning technique over a tidal period to ensure its reliability. We highlight the existing relationships between local diffusivity and both horizontal and vertical processes. Methodological aspects were analysed based on a reference case (number and distribution of particles, resolution, integration time period). The consistency and sensitivity of the coefficient were studied with different forcing conditions (hydrodynamical and meteorological regimes). In conclusion, our local diffusivity provides a new perspective for understanding the land-sea interface and coastal dispersion and holds potential for future studies of coastal marine ecosystems.

The origin of the atmospheric freshwater fluxes into the Bay of Bengal (BoB) are traced with Lagrangian water trajectories for both present and possible future climates. The water is traced backward from the precipitation at the sea surface to the evaporation regions. In the present-day simulation, the source is mostly from the Western Indian Ocean and near the Western Australian Coast. In the future climate scenario, simulated by EC-Earth, the origin of the moisture will not be the same as the present climate. In addition to it, the Bay of Bengal sourced water is also traced from the evaporation region to the precipitation locations. Most of the BoB originated moisture is precipitating within the neighbouring areas of the drainage basin and some part is transported into the Pacific Ocean. The Lagrangian model TRACMASS is currently running and a detailed analysis and results will be presented in the conference.

This study presents a Lagrangian analysis of upper-tropospheric anticyclones that are connected to surface heat waves in different European regions for the period 1979 to 2016. In order to elucidate the formation of these anticyclones and the role of diabatic processes, we trace air parcels backwards from the upper-tropospheric anticyclones and quantify the diabatic heating in these air parcels. Around 25 %–45 % of the air parcels are diabatically heated during the last 3 d prior to their arrival in the upper-tropospheric anticyclones, and this amount increases to 35 %–50 % for the last 7 d. The influence of diabatic heating is larger for heat-wave-related anticyclones in northern Europe and western Russia and smaller in southern Europe. Interestingly, the diabatic heating occurs in two geographically separated air streams; 3 d prior to arrival, one heating branch (remote branch) is located above the western North Atlantic, and the other heating branch (nearby branch) is located over northwestern Africa and Europe to the southwest of the target upper-tropospheric anticyclone. The diabatic heating in the remote branch is related to warm conveyor belts in North Atlantic cyclones upstream of the evolving upper-level ridge. In contrast, the nearby branch is diabatically heated by convection, as indicated by elevated mixed-layer convective available potential energy along the western side of the matured upper-level ridge. Most European regions are influenced by both branches, whereas western Russia is predominantly affected by the nearby branch. The remote branch predominantly affects the formation of the upper-tropospheric anticyclone, and therefore of the heat wave, whereas the nearby branch is more active during its maintenance. For long-lasting heat waves, the remote branch regenerates. The results from this study show that the dynamical processes leading to heat waves may be sensitive to small-scale microphysical and convective processes, whose accurate representation in models is thus supposed to be crucial for heat wave predictions on weather and climate timescales., Weather and Climate Dynamics, 1 (1), ISSN:2698-4016, ISSN:2698-4008

The Atlantic-to-Pacific atmospheric freshwater transport was calculated using Lagrangian water mass trajectories. These were decomposed into eastward and westward moving classes, carrying water ove ...

During the failure process, granite always exhibits strain-softening behavior and confining pressure-dependent effect. Based on triaxial cyclic loading and unloading compression tests, the evolutions of cohesive strength, internal friction angle, and elastic modulus with axial plastic strain and confining pressure were obtained. The results show that both the cohesive strength and the internal friction angle first increase and then decrease with an increase in the axial plastic strain. Meanwhile, the elastic modulus increases with an increase in the confining pressure and decreases with an increase in the axial plastic strain. Considering the evolutions of the cohesive strength, the internal friction angle and the elastic modulus, an improved strain-softening constitutive model was proposed. The proposed model was further embedded in the Fast Lagrangian Analysis of Continua (FLAC) procedure, based on which the conventional triaxial cyclic loading and unloading tests were simulated. The simulated results have shown a good agreement to the experimental results.

In oligotrophic gyres of the tropical ocean, islands can enhance phytoplankton biomass and create hotspots of productivity and biodiversity. This “Island Mass Effect” (IME) is typically identified by increased chlorophyll concentrations next to an island. Here we use a simple plankton model in a Lagrangian framework to represent an unexplained open ocean bloom, demonstrating how islands could have triggered it remotely. This new type of IME, termed “delayed IME”, occurs when nitrate is limiting, N:P ratios are low, and excess phosphate and iron remain in water masses after an initial bloom associated to a “classical” IME. Nitrogen fixers then slowly utilize leftover phosphate and iron while water masses get advected away, resulting in a bloom decoupled in time (several weeks) and space (hundreds of km) from island‐driven nutrient supply. This study suggests that the fertilizing effect of islands on phytoplankton may have been largely underestimated. Plain language summary In the poor and nutrient‐depleted waters of the tropical Pacific, islands act as sources of nutrients fertilizing nearby waters. These nutrients are consumed by microscopic photosynthesizing algae, the phytoplankton. The resulting phytoplankton enrichments (blooms) in turn support productive ecosystems. This phenomenon, termed the “island mass effect”, has been known for sixty years and is classically defined by increased chlorophyll (representing phytoplankton biomass) next to an island. Blooms also occur in the open ocean and are usually attributed to vertical processes such as mixing or uplifting that locally supply nutrients from subsurface reservoirs. In this paper, we demonstrate that a different type of island mass effect exists, where the phytoplankton response is delayed because they grow very slowly. These blooms are supported by the nitrogen fixer Trichodesmium. Since phytoplankton get carried away from islands by oceanic currents while they grow, this can lead to a bloom located hundreds of km away with no apparent connection to the islands. Nutrient inputs by islands followed by advection can thus trigger remote blooms in the open ocean. Our study suggests that the fertilizing effect of islands may currently be largely underestimated, particularly in the warm waters of the tropical Pacific where Trichodesmimum is common.

In most chemical reactors the homogeneous distribution of reactants is a desired prerequisite for guaranteed product quality and purity. However, oftentimes, especially in new reactor concepts this condition may not be met due to evolving or existing structures in the transport patterns. In this article the usage of Lagrangian analysis techniques in order to analyze chemical and biochemical reactors regarding the behavior of Lagrangian tracers is explored. A Lagrangian analysis on two different datasets is performed trying to show the large versatility of the concepts. The Lagrangian analysis techniques allow new insights into the reactor dynamics and could be a valuable tool to identify and characterize areas of different mixing performance The authors gratefully acknowledge the financial support provided by the German Research Foundation within the Priority Program ‘‘Reactive Bubbly Flows'', SPP 1740 (SCHL 617/12‐2 SCHL 617/13‐2) and by the Federal State of Hamburg, Ministry of Science, Research and Equalities of Hamburg, within the framework of the joint research project “New reactor technologies for chemical and biochemical synthesis processes” (Ref.‐No. LFF‐FV 43) SI

Influence of frontal dynamics on phytoplankton distribution and composition was studied combining in situ observations and Lagrangian computations from altimetry satellite derived currents. Four transects during the SHEBEX cruise (May 2015) over the Western Mediterranean were examined identifying a region with high spatial variability in the dynamical and biogeochemical properties. The dynamical situation unraveled from the Lagrangian analysis is dominated by filaments originated by an anticyclonic–cyclonic eddy interaction that organize the transport, modifying the biogeochemical properties of the water column and shaping the satellite derived surface Chlorophyll a (chla) distribution. The properties of the water column have been analyzed in relation to the dynamical properties of the filaments showing that local variation of the mixed layer and nutricline depths are correlated with the spatial variability of finite size Lyapunov exponents. Furthermore, the composition of phytoplankton community was studied regarding the path-accumulated properties of the flow during the formation of the filaments. In this regard new metrics accounting the Lagrangian evolution of the turbulent and topological properties of the flow along fluid parcel trajectories have been developed. Here we provide observational evidence that fluid parcels associated with high Lagrangian turbulent kinetic energy and Lagrangian positive vorticity host higher presence of larger pennate diatoms (i.e. Pseudo-nitzschia spp). Our findings indicate that the combination of these diagnostics provides an improved description of the turbulent dynamics showing that the Lagrangian properties of the flow have important biological consequences for phytoplankton to high ecological levels., I. Hernandez-Carrasco acknowledges the Vicenç Mut contract funded by the Government of the Balearic Islands, Spain and the European Social Fund (ESF) Operational Programme and the financial support from the Fundacion Universidad Empresa de las Islas Baleares, Spain through project ALERTA (REF-190121). We thank the officers and crew of the R/V SOCIB for logistical support, and technology development facility (ETD) from SOCIB for assistance in the field and A. Massanet for assistance with sampling and in the laboratory. Authors acknowledge the financial support from the Spanish Government MICINN/FEDER through projects MUSA (CTM2015-66225-C2-2-P) and MOCCA (RTI2018-093941-B-C31).

This chapter presents the results of the laboratory model tests and the numerical studies conducted on small diameter PVC pipes, buried in geocell reinforced sand beds. The aim of the study was to evaluate the suitability of the geocell reinforcement in protecting the underground utilities and buried pipelines. In addition to geocells, the efficacy of only geogrid and geocell with additional basal geogrid cases was also studied. A PVC (Poly Vinyl Chloride) pipe with external diameter 75 mm and thickness 1.4 mm was used in the experiments. The vehicle tire contact pressure was simulated by applying the pressure on the top of the bed with the help of a steel plate. Results suggest that the use of geocells with additional basal geogrid considerably reduces the deformation of the pipe as compared to other types of reinforcements. Further, the depth of placement of pipe was also varied between 1B and 2B (B is the width of loading plate) below the plate in the presence of geocell with additional basal geogrid. More than 50% reduction in the pressure and more than 40% reduction in the strain values were observed in the presence of reinforcements at different depths as compared to the unreinforced beds. Conversely, the performance of the subgrade soil was also found to be marginally influenced by the position of the pipe, even in the presence of the relatively stiff reinforcement system. Further, experimental results were validated with three-dimensional numerical studies using FLAC3D (Fast Lagrangian Analysis of Continua in 3D). A good agreement in the measured pipe stain values was observed between the experimental and numerical studies. Numerical studies revealed that the geocells distribute the stresses in the lateral direction and thus reduce the pressure on the pipe. In addition, the results of the 1-g model tests were scaled up to the prototype case of the shallow buried pipeline below the pavement using the appropriate scaling laws.

We provide an analysis and statement of the source term in the classical Kaluza field equations, by considering the 5-dimensional (5D) energy-momentum tensor corresponding to the 5D geodesic hypothesis that is typically presumed in the Kaluza theory. By providing the 5D matter Lagrangian, this work completes a Lagrangian analysis of the classical Kaluza theory that began by establishing the proper form of the unique Kaluza field Lagrangian. This work considers the transformation properties necessitated by general covariance of the Kaluza source terms, to establish the correct form for the source terms in the field equations, and to establish the 5D matter Lagrangian that corresponds to the 5D geodesic hypothesis. In addition to the effects of a scalar field expected from other scalar-tensor or scalar-electromagnetic theories, a peculiar Kaluza coupling coefficient arises for charged matter which acts to vary the source strengths in ways unknown to conventional physics. We briefly evaluate the implied modifications to source terms in the field equations. We find an ADM-like neutralization of gravity at high specific charge states and a saturation in field strength at high specific charge-to-mass ratios.

In this work, a unified representation of all the time-varying dynamics is accomplished with a Lagrangian framework for analyzing Fisher-Rao regularized dynamical optimal mass transport (OMT) derived flows. While formally equivalent to the Eulerian based Schrödinger bridge OMT regularization scheme, the Fisher-Rao approach allows a simple and interpretable methodology for studying the flows of interest in the present work. The advantage of the proposed Lagrangian technique is that the time-varying particle trajectories and attributes are displayed in a single visualization. This provides a natural capability to identify and distinguish flows under different conditions. The Lagrangian analysis applied to the glymphatic system (brain waste removal pathway associated with Alzheimer's Disease) successfully captures known flows and distinguishes between flow patterns under two different anesthetics, providing deeper insights into altered states of waste drainage.

This paper presents the results from three-dimensional analysis of offshore driven pipe piles using FLAC3D (Fast Lagrangian Analysis of Continua in three Dimensions) program. The numerical model was developed with solid elements for both the pile and the surrounding soil. Interfaces are created both on the inside and outside surfaces of the pipe pile along the length as well as at the bottom of the annular area of the pile. The pile driving was simulated by giving hammer impact force of one blow which was measured during offshore pile installation. Parametric studies were performed with different soil properties until the signals from the numerical analyses matched with the measured force–velocity data of the pile installed in offshore South East Asia region. The results include the soil plug behaviour under continuous driving and with a delay time of 12 h.

Made available in DSpace on 2020-12-12T02:24:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01 Changes in the characteristics of austral winter (June–July–August) synoptic activity in three domains (Africa, Australia and South America) of the extratropical Southern Hemisphere projected with the Regional Climate Model version 4 (RegCM4) are presented. The model is nested in three global climate models (GCMs) from the Coupled Model Intercomparison Project phase 5 (CMIP5) under the Representative Concentration Pathway 8.5. The model grid spacing is 25 km and the simulations cover the period 1970–2100. Synoptic activity is analyzed using both Eulerian and Lagrangian approaches. The Eulerian analysis shows an increase of the synoptic activity south of 40° S in the RegCM4 and GCMs ensembles for the future (2080–2099) compared to the present (1995–2014), but this signal does not necessarily indicate an increase in the cyclone frequency since it includes cyclonic and anticyclonic features. The Lagrangian analysis, however, indicates a decrease in the frequency of cyclones, with a positive tendency towards stronger systems, although the latter is not statistically significant at 95% confidence level. Lifetime, traveled distance and mean speed of the cyclones do not present statistically significant changes in the future climate. On the other hand, a significant increase in both intensity and extension of areas affected by precipitation associated with cyclones is found. As a consequence, there is a statistically significant trend of individual cyclones to produce more rainfall in the future. Federal University of Itajubá UNIFEI Earth System Physics ESP The Abdus Salam International Centre for Theoretical Physiscs Istituto Nazionale di Oceanografia e Geofisica Sperimentale OGS Departamento de Ciências Atmosféricas Universidade de São Paulo USP Department of Physical Oceanography Ensenada Center for Scientific Research and Higher Education CICESE Universidade Estadual Paulista UNESP Centro de Meteorologia de Bauru IPMet Universidade Estadual Paulista UNESP

Atmospheric blocks strongly influence surface weather, including extremes such as heat waves and cold spells. Recently, diabatic heating and associated upper‐tropospheric potential vorticity (PV) modification have been identified as important modulators of atmospheric blocking dynamics. Also, robust links between atmospheric blocks and proximate heavy precipitation events have been established. This leads to the question of the extent to which diabatic heating associated with heavy precipitation events influences Northern Hemisphere blocking. This study uses 5 years of 3‐day back trajectories started from objectively identified blocks in the ERA‐Interim dataset to investigate this relationship. A substantial fraction of air parcels in blocks pass through heavy precipitation areas. The exact fraction depends on the choice of heavy precipitation threshold. Roughly 19% of all the trajectories in a block pass a heavy precipitation area (>95th percentile) area while being saturated. Of the air parcels in a block that are heated at least 5 K, 60% pass a heavy precipitation area while saturated. This fraction varies with the season and geographical area. The overall fraction is lowest in summer and highest in winter, higher over oceans than over land, and higher over the Pacific than over the Atlantic. In summer, heating is relevant over the continents and heating over North America influences blocks over the eastern Atlantic. For summer blocks in the North Atlantic and over Scandinavia, heating happens partly over the European continent.

The structure of highway tunnels with large span and small spacing has the characteristics of flat, long span, and thin arch. The load distribution and supporting mechanical characteristics of the surrounding rock are complex. The stability of the structure is affected by many processes during construction. The strength of the supporting structure is variable and prone to the instability of the surrounding rock and the cracking and destruction of the tunnel supporting structure. The comparison and verification of field monitoring data and numerical simulation analysis were carried out to analyze the construction mechanical mechanism of the large span and small spacing highway tunnels based on the construction of the Fo Yangling Tunnel in Binlai Highway, which belongs to the reconstruction and extension highway project of Zibo to Laiwu and on the Fast Lagrangian Analysis of Continua in 3 Dimensions numerical simulation software to rule out the stress and strain of the tunnel and the surrounding rock. The numerical simulation results are in good agreement with the field monitoring data. The results show that: (1) The construction of the subsequent digging tunnel significantly affects the prior digging tunnel. (2) Stress concentration tends to occur in the haunch and the foot of the tunnels and the middle surrounding rock. (3) Reasonable grouting on the surrounding rock can effectively reduce surface settlement and reduce the influence of the excavation of subsequent digging tunnel on the prior digging tunnel. (4) During construction, reasonable selection of grouting reinforcement area should be combined with the actual situation to avoid material waste. The analysis results can provide a scientific basis for the design and construction of highway tunnels with large span and small spacing.

We identify Lagrangian coherent vortices in a global mesoscale eddy-permitting ocean model using the rotation-based method of Haller et al. (2016). We present an analysis of the acute sensitivity of the identification results to varying the method’s free parameters, and develop physically justified parameter choices that allow for systematic vortex identification. In contrast to prior vortex studies, we probe the broad spectrum of coherency in the ocean by determining free parameter choices that partition the spectrum into distinct coherency classes allowing for the identification of strictly coherent, moderately coherent, and leaky vortices. Our tuning methodology is grounded in a combination of sensitivity analysis, convergence tests, and consideration of the ocean model’s physics. To aid in this process, we introduce the Coherency Index a novel Lagrangian diagnostic for mathematically quantifying the degree of material coherency of a Lagrangian vortex. We aim for this manuscript and the accompanying open-access code to serve as a manual and toolset for the oceanographer interested in harnessing a rigorous Lagrangian method to uncover coherent structures in ocean models and observations.

The flow dynamics of a sweeping jet generated by a fluidic oscillator is experimentally investigated by time-resolved particle image velocimetry (TR-PIV). Lagrangian transformation is applied to the measured flow fields to better determine the characteristics of the jet flow outside the oscillator. Upon increasing the Reynolds number from Re = 2.5 × 103 to 11.7 × 103, which respectively corresponds to the occurrences of straight and deflected jet columns, the spreading angle of the external jet increases and reaches its saturation value. The overall performance of the flow fields is first examined in Eulerian space. At the higher Reynolds number, the momentum is more directed at the maximum deflected positions of the jet. A clear weak flow is then induced at the middle of the far field region from the jet nozzle. The induced jet column is also bent significantly into a curved shape. To examine the variations of the jet flows with different column shapes, Lagrangian transformation is applied to the measured flow fields by attaching a rotating reference frame on the jet column. It is found that the large bending angle of the jet column at the higher Reynolds number induces higher fluctuations and more uneven oscillation patterns in the jet flow. In the far field region at the higher Reynolds number, the time-averaged jet velocity decreases faster, with higher turbulence intensities than those at the lower Reynolds number. The phase-dependent jet flow fields confirm that the peak velocity and the jet width also have higher fluctuations at the higher Reynolds number. In addition, the jet bending angle in the far field region shows more uneven oscillation patterns compared with those in the near field region. These highly fluctuating and uneven flow behaviors contribute to the uneven distribution of the jet momentum at the higher Reynolds number in Eulerian space. Finally, different fluctuating behaviors of the jet flow due to the different jet shapes are also revealed by Lagrangian dynamic mode decomposition (DMD).

A Lagrangian analysis is applied to identify the main moisture source areas associated with atmospheric rivers (ARs) making landfall along the west coast of South Africa during the extended austral winter months from 1980 to 2014. The results show that areas that provide the anomalous uptake of moisture can be categorized into four regions: (1) the South Atlantic Ocean between 10°S and 30°S, (2) a clear local maximum in the eastern South Atlantic, (3) a continental source of anomalous uptake to the north of the Western Cape, and (4) over South America at a distance of more than 7000 km from the target region. It emerges that the South American moisture source can be linked to a particular phase of the South American low-level jet, known as a no Chaco jet event (NCJE), which transports moisture to the western and central South Atlantic basin. Concisely, we provide strong evidence that the two margins of the South Atlantic Ocean appear connected by two meteorological structures, with the NCJE playing a key role of transporting moisture from South America to the western and central South Atlantic basin, feeding the AR that transports some of the moisture to the west coast of South Africa.

A vortex pair + single vortex (P+S) wake behind a transversely oscillating cylinder is investigated from the Lagrangian point of view. The Lagrangian coherent structures (LCSs) of the flow are computed to analyze formation of vortices in the wake. An asymmetric vortex street is obtained by using a dynamic mesh method. The corresponding vorticity field is found to agree well with real experiments. The LCSs are approximated by ridges of the finite-time Lyapunov exponents computed from transient velocity fields. The formation process is investigated using the vorticity field and the LCSs. It is found that details of the wake pattern are sensitive to initial oscillation conditions, and that the cylinder motion causes an early roll-up of boundary layers to form new vortex structures in the wake. Lagrangian description of the flow with the help of the LCSs provides further details about formation of vortices in the cylinder flow and helps to get a new insight into the flow structure in the wake region.

The purpose of this study was to introduce a novel technology named segmental adjustment of hydraulic support setting load (SAHSSL) for pre-splitting and weakening the coal wall of a fully mechanized working face in hard and thick coal seams (HTCSs). The efficiency of SAHSSL was explored in the relatively stable and significant movement stages. A numerical simulation method using fast Lagrangian analysis of continua in three dimensions was used to evaluate the instability characteristics of the coal wall under different support setting loads (SSLs) ranging from 2000 to 8000 kN. The numerical results were verified by industrial testing of coal wall weakening in HTCSs. The results revealed that with the implementation of SAHSSL, the average coal-cutting time of the shearer reduced by about 21.7% (or 1.8 h), and the increasing resistance state was 64.8% of the 115 working cycles in the working specialty measurement of the support. Reasonable SSLs in the relatively stable stage of the periodic weighting length were obtained between 4000 kN and 6000 kN. The ground pressure was found to be the primary factor influencing the hard coal wall weakening for thick coal seam mining. The findings of this study clearly indicate that the proposed SAHSSL technology greatly enhanced the coal-cutting efficiency and weakened the coal wall effectively, and it could be adjusted under an effective roof control principle to meet the segmental requirements of coal wall weakening for thick coal seam mining.

The deep patch repair technique has been widely used in the western U.S.A. to address subsidence and shallow slope failures mainly within poorly performing side-cast embankments and natural slopes consisting of weak soils overlying stronger soils. This project was a multi-phase effort to examine, refine, update, and verify the design procedure associated with this repair method. An experimental design was developed to examine the performance of various deep patch repair configurations and to validate the design technique developed using FLAC (Fast Lagrangian Analysis of Continua) modeling results during Phase I. A series of unreinforced and reinforced slope configurations were tested using a large centrifuge to study their behavior and document their performance. Fourteen centrifuge models (seven unreinforced and seven deep patch reinforced) were run to verify the design chart for a 39-degree slope angle and having one-foot thick deep patch layer spacing (one of four design charts developed during Phase I). Performance of the deep patch models was evaluated based on a serviceability criterion limiting movement in the road bench atop the reinforced zone. Models reinforced with deep patches helped stabilize slope failures by acting as a cantilever and redirecting the failure path to the face of the slope beneath the slope crest, thereby reducing distresses near the top surface of the deep patch. Overall, results from this analysis indicated that the design tool created during Phase I sufficiently predicts the depth of the deep patch necessary to achieve good performance.

Lagrangian calculations based on satellite altimetry data (1993–2015) statistically demonstrated the existence of stable transport pathways of subtropical waters to the southern coasts of Russian Primorye through the subarctic front of the Sea of Japan. This transport is mainly provided by a peculiar mesoscale circulation north of the front as eddy streets, which facilitate the formation of Lagrangian intrusions of warm water penetrating further northward. The transport of warm waters in recent decades could be one of the factors responsible for the prolonged warm autumns observed in Primorye since the 1990s and explains the penetration of thermophilic fishes and other tropical and subtropical marine organisms and animals to the Primorye coasts.

Incidental catch of nontarget species (bycatch) is a major barrier to ecological and economic sustainability in marine capture fisheries. Key to mitigating bycatch is an understanding of the habitat requirements of target and nontarget species and the influence of heterogeneity and variability in the dynamic marine environment. While patterns of overlap among marine capture fisheries and habitats of a taxonomically diverse range of marine vertebrates have been reported, a mechanistic understanding of the real-time physical drivers of bycatch events is lacking. Moving from describing patterns toward understanding processes, we apply a Lagrangian analysis to a high-resolution ocean model output to elucidate the fundamental mechanisms that drive fisheries interactions. We find that the likelihood of marine megafauna bycatch is intensified in attracting Lagrangian coherent structures associated with submesoscale and mesoscale filaments, fronts, and eddies. These results highlight how the real-time tracking of dynamic structures in the oceans can support fisheries sustainability and advance ecosystem-based management.

During the process of archaeological excavation in the regions of Southeast China, collapse of test square usually occurs due to poor site-specific conditions. In this paper, the fast Lagrangian analysis of continua in three dimensions (FLAC3D) is employed to reveal the behaviors of test square. Taking the archaeological works in Liangzhu prehistoric earthen sites as the research background, the paper first introduces the geological setting, excavation procedure and monitoring scheme of the studied test square. Then, the deformation of four sides of the test square is modeled using FLAC3D. By comparison, it shows that the numerical results are consistent with the results from field monitoring. The result suggests that the numerical simulation can be effectively applied to representing the actual behaviors of the test square, which is helpful for determination of excavation scheme and stability evaluation of the test square during archaeological excavation. Keywords: Prehistoric earthen site, Archaeological excavation, Test square behaviors, Field monitoring, Numerical simulations

An advancing tunnel in deep saturated ground induces coupled interactions between transient fluid flow and deformation that affect the hydro-mechanical (H-M) response of the ground surrounding the excavation. The use of the convergence-confinement method (CCM) to simplify this three-dimensional (3-D) coupled problem into a 2-D plane strain model must then account for this transient coupling effect. Similarly, the induced radial displacement of the tunnel, commonly represented as the longitudinal displacement profile (LDP), will also be influenced by this time-dependent coupled interaction. This study investigates the effect of the transient H-M interaction on the practical implementation of the CCM and the LDP of an advancing tunnel in deep saturated ground. The tunnel is represented by a 2-D axisymmetric coupled H-M model that is built into the computer program Fast Lagrangian Analysis of Continua (FLAC) and is subjected to an isotropic in situ stress field. First, the study analyzes the induced pore pressure and deformation behavior during the excavation and standstill periods. Second, to account for the transient coupling effect, this study proposes: (1) nonlinear unloading factors for estimating excavation-induced pore pressure changes in CCM and (2) new LDP equations for predicting transient radial displacements along the axis of the tunnel. The resulting relationships from the two propositions are normalized, and thus, they should be applicable to other tunnel depths as well.

The Fertile Crescent (FC) region comprises the east coast of the Mediterranean Sea and the northern part of the Arabian Peninsula. The FC suffered two severe drought episodes separated by a 7-year period, in 1998–2000 and 2007–2009, which are considered the most severe episodes to hit the region in the last 50 years. A Lagrangian model (FLEXPART) and ERA-Interim data (with a 1° × 1° lat-long resolution) were used to identify for the first time the climatological sources of moisture for the FC and their characteristics. Variability and the source-receptor relationships, concerning their contribution to the precipitation, and the implications regarding the transport of moisture changes over the FC, during the wet season (October-May) from 1980 to 2014 were analysed. The main climatological moisture sources during this period were determined to be the FC itself, the eastern Mediterranean Sea, the Red Sea, the Persian Gulf, the Arabian Sea, the Caspian and Black Seas, and the central and western parts of the Mediterranean Sea. The analysis showed higher anomalous conditions in the moisture transport from some moisture sources during the two outstanding drought episodes. The key feature of the wet seasons during these episodes was a deficit in the moisture losses over the studied area related to the FC itself, the Red and Arabian Seas sources, followed and to a lesser extent by the eastern Mediterranean Sea over the northern part of the FC region. Nevertheless, the moisture supply deficit from the sources was much greater during the 2007–2009 drought event. The SPEI index at large scales (24 months) showed that the 2007–2009 episode was part of longer-term drought conditions that had been developing over the previous months, reinforcing the drought severity given recycling processes attributed to the FC. During the two extreme drought episodes, the mountainous terrain over the northern and eastern FC suffered the highest precipitation deficits, and these areas are, precisely, the most influenced by two of the major moisture sources, namely, the FC and eastern Mediterranean Sea. The decreased moisture contribution from these main sources led to more intense droughts over the region. As a result, both regions should be considered as hotspots to signal severe or extreme droughts in the region.