Intermediate Flow Research Articles

Multiscale Elastohydrodynamic Wedge-Platform Thrust Bearing with Ultra Low Clearance

The effect of the surface elastic deformation is investigated by the multiscale approach in the hydrodynamic wedge-platform thrust bearing with the ultra low clearance on the 1nm scale, by incorporating both the non-continuum pure adsorbed layer flow and the multiscale “sandwich” film flow. The pure adsorbed layer flow in ultra small surface separations is described by the non-continuum nanoscale flow equation; The “sandwich” film flow is described by the multiscale flow equations respectively for the adsorbed layer flow and the intermediate continuum fluid flow. The numerical calculation results show that in the studied bearing, the effect of the surface elastic deformation is normally significant, it pronouncedly reduces the maximum film pressure, greatly changes both the film pressure profile and the surface separation profile, and considerably increases the minimum surface separation, which occurs on the exit of the bearing. The effect of the surface elastic deformation is shown to be obviously dependent on the fluid-bearing surface interaction.

Transient physics in the compression and mixing dynamics of two nanochannel-confined polymer chains.

We use molecular dynamics (MD) simulation and nanofluidic experiments to probe the non-equilibrium transient physics of two nanochannel-confined polymers driven against a permeable barrier in a flow field. For chains with a persistence length P smaller than the channel diameter D, both simulation and experiment with dsDNA reveal nonuniform mixing of the two chains, with one chain dominating locally in what we term "aggregates." Aggregates undergo stochastic dynamics, persisting for a limited time, then disappearing and reforming. Whereas aggregate-prone mixing occurs immediately at sufficiently high flow speeds, chains stay segregated at intermediate flow for some time, often attempting to mix multiple times, before suddenly successfully mixing. Observation of successful mixing nucleation events in nanofluidic experiments reveal that they arise through a peculiar "back-propagation" mechanism whereby the upstream chain, closest to the barrier, penetrates and passes through the downstream chain (farthest from the barrier) moving against the flow direction. Simulations suggest that the observed back-propagation nucleation mechanism is favored at intermediate flow speeds and arises from a special configuration where the upstream chain exhibits one or more folds facing the downstream chain, while the downstream chain has an unfolded chain end facing upstream.

Pemanfaatan Batu Sungai Mappak Kabupaten Tana Toraja Dalam Campuran Laston Lapisan Antara

This research aims to find out how the aggregate characteristics of the Mappak River in Tana Toraja Regency can be used as a pavement material for asphalt mixtures. The method used is the conventional marshall method to obtain the properties of the mixture and marshall immersion to obtain residual marshall stability from the optimum asphalt content mixture. The results of the study indicated that the aggregate characteristics of the Mappak River stone in Tana Toraja Regency with an aggregate wear value of 21.6% met the specifications as a road pavement layer material for Mixed Laston Intermediate Layers with Optimum Asphalt Content of 6.20%, with the mixed properties of Laston Intermediate Layers, namely Density, Stability, flow, VIM, VMA, VFB and Marshall Quentient have met the Specifications of Bina Marga 2018. Through Marshall Immersion testing the Laston Intermediate Layers mixture with Optimum Asphalt Content of 6.20% obtained Remaining Marshall Stability of 95.07%, which means that it meets the Specifications Bina Marga 2018, namely at least 90%..

Exploring Neighbor Correspondence Matching for Multiple-hypotheses Video Frame Synthesis

Video frame synthesis, which consists of interpolation and extrapolation , is an essential video processing technique that can be applied to various scenarios. However, most existing methods cannot handle small objects or large motion well, especially in high-resolution videos such as 4K videos. To eliminate such limitations, we introduce a neighbor correspondence matching (NCM) algorithm for flow-based frame synthesis. Since the current frame is not available in video frame synthesis, NCM is performed in a current-frame-agnostic fashion to establish multi-scale correspondences in the spatial-temporal neighborhoods of each pixel. Based on the powerful motion representation capability of NCM, we propose a heterogeneous coarse-to-fine scheme for intermediate flow estimation. The coarse-scale and fine-scale modules are trained progressively, making NCM computationally efficient and robust to large motions. We further explore the mechanism of NCM and find that neighbor correspondence is powerful, since it provides multiple-hypotheses motion information for synthesis. Based on this analysis, we introduce a multiple-hypotheses estimation process for video frame extrapolation, resulting in a more robust framework, NCM-MH. Experimental results show that NCM and NCM-MH achieve 31.63 and 28.08 dB for interpolation and extrapolation on the most challenging X4K1000FPS benchmark, outperforming all the other state-of-the-art methods that use two reference frames as input.

Genetic diversity and population structure of a rare and endangered freshwater macrophyte <i>Potamogeton rutilus</i> Wolfg.

Comprehending genetic variation and population structure is paramount for devising optimal management strategies and conservation efforts. In this study, we employed amplified fragment length polymorphism (AFLP) analysis to assess the distribution of genetic variation within and among populations of the rare macrophyte <i>Potamogeton rutilus</i> Wolfg. This species has experienced habitat alterations leading to its disappearance from numerous previously known European locations. Our analysis encompassed eight populations collected from Poland, Lithuania, and Estonia, situated within the central region of <i>P. rutilus</i> distribution. The results of our study indicate that the analyzed populations are characterized by relatively low levels of genetic diversity (the mean of Nei’s gene diversity was 0.031±0.003 and the Shannon’s information index 0.049± 0.004), and intermediate gene flow (Nm = 0.289). Analysis of molecular variance (AMOVA) revealed higher levels of variation among populations (63%) than within populations (37%); PhiPT = 0.634, <i>p</i> < 0.001, which might be attributed to the founder effect, frequent vegetative propagation, and limited seedling recruitment. The results of STRUCTURE, PCoA and NeighbourNet analyses suggest that the genetic structure of the studied populations falls into three main clusters not fully corresponding to geographical regions. The Mantel test did not show a significant correlation between genetic distance and geographical distance among populations. The most geographically isolated population sampled in Poland (ROT) is genetically close to the Estonian population VAL and VIT, although it is located far closer to the stations in Lithuania. Implications of acquired data for the genetic management of the species are discussed.

A machine learning based acceleration of segregated pressure correction algorithms for incompressible fluid flow

Segregated pressure correction algorithms are widely used in the simulation of steady-state incompressible fluid flow. However, these traditional solution algorithms usually require high computational resources for design optimization problems. To resolve this issue, we propose an advanced tree-based Machine Learning (ML) model named Extremely Randomized Trees (ERT) for speeding up the convergence of segregated pressure correction algorithms. Then, its prediction performance is compared with the widely used Decision Tree (DT) and Random Forest (RF) with its prediction results finally incorporated into simulation process as an intermediate flow field. The ML model is designed to predict the primary flow properties including turbulent kinetic energy, turbulent dissipation rate, turbulent viscosity, pressure and velocity, whose modeling capability is assessed by the interpolation generalization and extrapolation generalization. Our assessments are on the basis of flow past a surface-mounted obstacle with apparent flow separation and considerable mesh anisotropy to represent a practical CFD application. For the generalization investigation with either varying inlet velocity conditions or aspect ratios of the obstacle, the pressure correction algorithms hybridized with the ML model both achieve high-resolution steady-state results with a significant reduction in iteration steps and computational cost comparing with those without ML acceleration, which is due to that the selected ML model gives more satisfactory initial conditions for the traditional pressure correction algorithms. The results provide a reference for the rapid exploration of parameter spaces in design optimization problems.

Astronomically‐Paced Changes in Paleoproductivity, Winnowing, and Mineral Flux Over Broken Ridge (Indian Ocean) Since the Early Miocene

AbstractA significant shift in Earth's climate characterizes the Neogene, transitioning from a single‐ice‐sheet planet to the current bipolar configuration. This climate evolution is closely linked to changing ocean currents, but globally‐distributed continuous high‐resolution sedimentary records are needed to fully capture this interaction. The Ocean Drilling Program (ODP) Site 752, located on Broken Ridge in the Indian Ocean, provides such a Miocene‐to‐recent archive. We use X‐ray fluorescence (XRF) core scanning to build an eccentricity‐tuned age‐depth model and reconstruct paleoceanographic changes since 23 Ma. We find two intervals of enhanced productivity, during the early and middle Miocene (18.5–13.7 Ma) and late Pliocene/early Pleistocene (3–1 Ma). We also report a mixed eccentricity‐obliquity imprint in the XRF‐derived paleoproductivity proxy. In terms of grain size, three coarsening steps occur between 19.2–16 Ma, 10.8–8 Ma, and since 2.6 Ma. The steps respectively indicate stronger current winnowing in response to vigorous Antarctic Intermediate Water flow over Broken Ridge in the early Miocene, the first transient onset of Tasman Leakage in the Late Miocene, and the intensification of global oceanic circulation at the Plio‐Pleistocene transition. High‐resolution iron and manganese series provide a detailed Neogene dust record. This study utilized a single hole from an ODP legacy‐site. Nevertheless, we managed to provide novel perspectives on past Indian Ocean responses to astronomical forcing. We conclude that Neogene sediments from Broken Ridge harbor the potential for even more comprehensive reconstructions. Realizing this potential necessitates re‐drilling of these sedimentary archives utilizing modern drilling strategies.

Heat transfer area optimization of intermediate heat-exchange cycle system for aero engines

The present study constructs an intermediate heat-exchange cycle system for aero engines. To explore the impact of circulation parameters on the cycle, a mathematical model has been developed. Based on the mathematical model, a novel and convenient approach to determining intermediate working fluid (IWF) mass flow rate and temperature, achieving the minimum total system heat transfer area, has been proposed. A two-stage heat exchanger combined intermediate heat-exchange cycle system with Chinese aviation kerosene RP-3, high-pressure water, and air as working fluids is taken as an example to verify the analytical results through numerical calculations. The deviation between the analytical and numerical results is relatively small, below 0.03%. For the situation of a given higher intermediate temperature, a wide range of IWF mass flow rates can be selected as the design point without significantly affecting the total heat transfer area. For the situation where both intermediate temperature and IWF mass flow rate are variable, an optimal area exists where the total heat transfer area is very low and does not differ much with each point. Overall, the present findings can serve as reasonably accurate preliminary guidelines for designing and optimizing the intermediate heat-exchange cycle system.

Groundwater Circulation Mechanism of the Upstream Area of Beiniuchuan River Using Isotope–Hydrochemical Tracer

In order to achieve the rational development and utilization of underground water resources in the Dongsheng mining area under coal mining conditions, we selected the upstream area of Beiniuchuan River as a typical region. Through field investigations, sampling tests, and the application of hydrochemical and isotope techniques, we traced the groundwater circulation mechanism in the Dongsheng mining area. The results indicate that the majority of the Quaternary alluvial and Salawusu Formation groundwater is of the HCO3-Ca type, with a TDS content below 300 mg/L. However, in some areas, the hydrochemical type becomes complex due to anthropogenic contamination. The shallow-buried Yan’an Formation groundwater is either of the HCO3-Ca·Mg type or the HCO3·SO4-Ca·Mg type, with TDS content ranging from 200 to 750 mg/L. The Yan’an Formation at depths greater than 40 m exhibits complex water chemistry, with a TDS content higher than 500 mg/L, and it belongs to the Cl-Na type, with TDS around 700 mg/L. The hydrogen and oxygen isotope results indicate that the local groundwater is primarily recharged via atmospheric precipitation. The 3H and 14C results show that the Quaternary alluvial and shallow-buried Yan’an Formation groundwater has a fast turnover rate, while the deep-buried Yan’an Formation and Yan’chang Formation groundwater have a slower turnover rate. The regional groundwater circulation can be generalized into three flow systems: shallow, intermediate, and deep. Under the influence of coal mining activities, the water circulation conditions in the study area have undergone significant changes. The sealing integrity of the Yan’an Formation has been compromised, and precipitation and shallow groundwater have enhanced the vertical infiltration capacity of the formation, increasing the proportion of groundwater participating in the intermediate flow system. As a result, the river runoff mainly dependent on the discharge from the shallow flow system has drastically decreased.

Effects of nozzle orifice shape on jet breakup and splashing during liquid jet impact onto a horizontal plate

In some accident situations in nuclear power plants, liquid coolant is discharged from a non-circular rupture hole. Thus, to improve the understanding on the effects of nozzle orifice shape on the jet behavior, experiments were carried out on the liquid jet ejected from oval nozzles. In the experiments, water was used as the test liquid, the area-equivalent nozzle diameter was within 1.8-2.9 mm, the aspect ratio of the nozzle hole was within 2.6-4.8, and the jet velocity was varied within 0.25-11.3 m/s. At low and high liquid flow rates, the liquid jet behaved similarly to the circular jet; the jet breakup lengths and the size of the droplets formed after the jet breakup were expressed by similar dimensionless correlations as those for the circular jet. At the intermediate liquid flow rate, a bamboo leaf-like structure formed on the liquid jet dominated the jet breakup. The jet breakup length was therefore correlated using a theory for the surface tension-induced shape oscillation of elliptical fluid. These correlations enabled to estimate the liquid jet state at any distance from the nozzle. It was also confirmed that if the state of the liquid jet at the impact point is known, the splash rate and the size of the splashed droplets can be predicted satisfactorily using the available correlations based on the experimental data for the circular jet. Therefore, the present work extended the available knowledge on the liquid jet discharged from a circular nozzle to enable the prediction of the behavior of the liquid jet and the characteristics of the secondary droplets produced during liquid jet impact onto a solid surface for the oval nozzles.

Non-continuum effects on the sound of a heated line source: from a monopole to non-isotropic radiation

We study the effect of continuum breakdown on the two-dimensional thermoacoustic radiation of a thin plate set in a perfect monatomic gas. The plate is heated harmonically in time and the acoustic field is investigated in the entire range of gas rarefaction rates. Analytical approximations are obtained in the limits of high (free-molecular) and low (continuum limit) gas rarefaction, accompanied by direct simulation Monte Carlo calculations at intermediate flow conditions. While the source acoustic field is of a monopole type in the continuum regime, it turns non-isotropic at non-continuum conditions, exhibiting dipole directivity and exponential decay rate in the collisionless limit. The combined effects of source heating frequency and gas Knudsen number on the far-field acoustic radiation are illustrated and rationalized.

Stream hydrology and a pulse subsidy shape patterns of fish foraging.

Pulsed subsidy events create ephemeral fluxes of hyper-abundant resources that can shape annual patterns of consumption and growth for recipient consumers. However, environmental conditions strongly affect local resource availability for much of the year, and can heavily impact consumer foraging and growth patterns prior to pulsed subsidy events. Thus, a consumer's capacity to exploit pulse subsidy resources may be influenced by antecedent environmental conditions, but this has rarely been shown in nature and is unknown in aquatic ecosystems. Here, we sought to understand the importance of hydrologic variation and a salmon pulse subsidy on the foraging and growth patterns of two stream salmonids in a coastal southeast Alaska drainage. To do this, we sampled fish stomach contents at a high temporal frequency (daily-weekly measurements) and analyzed fish consumption rates in relation to streamflow and pulse subsidy resource availability. We then explored the influence of interannual hydrologic variation on access to pulse subsidy resources (i.e. whether fish exceeded an egg consumption gape limit) in a bioenergetic simulation. Prior to Pink Salmon spawning, Dolly Varden and Coho Salmon displayed distinct and nonlinear flow-foraging relationships, where forage for both species consisted primarily of macroinvertebrates. During this time period, consumption maxima coincided with baseflow and the highest observed flow conditions, and consumption minima were observed at severe low-water and intermediate flow values. After salmon spawning began, forage was not significantly related to flow and consisted primarily of salmon eggs. Further, consumption rates increased overall, and foraging patterns did not appear to be affected by flow in either species. Bioenergetic simulations revealed that patterns of interannual hydrologic variation may shift Coho Salmon growth trajectories among years. Together, our results suggest that access to marine pulse subsidy resources may depend on whether antecedent hydrologic conditions are suitable for juvenile salmonids to grow large enough to consume salmon eggs by the onset of spawning.

A Composite Framework Model for Transient Pressure Dynamics in Tight Gas Reservoirs Incorporating Stress Sensitivity

Natural gas is an eco-friendly energy source with low carbon emissions, making it attractive globally. Understanding gas reservoirs is crucial for sustainable extraction and optimizing potential. However, the complicated fluid flow and production dynamics within intricate gas reservoirs, particularly those characterized by abnormally high pressures and tight porous media, remain partially understood and demand further investigation. In a tight porous medium subjected to high pressure, the assumption of constant permeability is no longer valid. Consequently, a novel composite seepage model has been developed in this study, which considers the responsiveness of permeability to stress. Perturbation theory is employed to address the inherent non-linearity demonstrated by the permeability modulus. The solution of dimensionless pressure responses under constant production conditions is accomplished in the Laplace domain by implementing integral transformation methods. Overall, a comprehensive model is provided to understand the production behaviors of tight gas reservoirs. Moreover, in order to comprehend the transient flow characteristics of tight gas reservoirs, log–log plots are generated through the Stehfest numerical inversion approach, with the flow regimes categorized based on the normalized time phases of the pressure curves. Parametric investigations reveal that stress sensitivity detrimentally affects permeability, resulting in more pronounced pressure declines during the intermediate and late flow phases. The transient seepage model elaborated in this study is able to consider the pertinent formation and well parameters. These interpreted parameters bear significance in designing hydraulic fracturing operations, assessing the potential of tight gas reservoirs, and ultimately enhancing gas production. The presented model not only enhances our understanding of the behavior of horizontal wells in stress-sensitive tight gas reservoirs but also makes a valuable contribution to the broader discussion on transient flow phenomena in petroleum engineering.

Performance evaluation of innovative sensible energy storage material integration as an obstacle in solar collectors for drying applications

This research paper presents an innovative approach to enhance the performance of solar collectors in drying processes by integrating a sensible energy storage material within the airflow passage as an obstacle. The study involves a real-time comparative analysis of different collector configurations, under identical meteorological conditions, including flat collector, finned collector and rock integrated collector. The experimental results demonstrate that at high flow rate the collector equipped with fins achieves higher outlet temperatures, with a maximum of 59.8 °C, compared to 58.2 °C for the collector without fins. Additionally, for low and intermediate flow rates, the collector utilizing rocks as the energy storage material exhibits a maximum outlet temperature of 70.2 °C, while the collector with fins reaches 76.8 °C. Notably, the collector with rocks demonstrates a temperature gain of 13.6 °C during the night period. The drying efficiency of both solar dryers is evaluated, and they achieve a final moisture content of 6 % from an initial moisture content of 88 % (kg water/kg wet basis) in 1452 and 1722 min in solar dryer with fins and rocks, respectively. The drying rate is observed to be higher in the solar dryer with fins compared to the one with rocks. Midilli-Kucuk model provided the best agreements between experimental and predicted moisture ratios. Furthermore, the average effective moisture diffusivity is found to be higher in the solar dryer with fins (6.39485E-10 m2/s) compared to the one with rocks (1.33512E-10 m2/s).

Modeling of Water Transport through Plasmodesmata in Plant Cell

The water transport property in the plasmodesmata in a plant cell is calculated from the multiscale flow equation by incorporating both the adsorbed boundary layer flow and the intermediate continuum water flow. The plasmodesmata has the desmotubule which is the cylindrical nanotube with the diameter ranging between 20nm and 40nm and the length from 12000nm to 26000nm. In the absence of the wall slippage, there is the large flow resistance in this nanochannel preventing the water from flowing through; for the easy transport of water through this nanochannel,the wall slippage must occur and it results in the water flow rate through the channel several orders higher than the classical continuum flow theory calculation, depending on the power loss on the transportation. The pressure drop and the critical power loss on a single desmotubule for initiating the wall slippage are calculated as functions of the diameter and the length of the desmotubule.

Implementation of Hydrological Model for the Malino Catchment Area in South Sulawesi Province, Indonesia

In South Sulawesi, the development of irrigation may be hindered by the continuing limitations and inadequacies of hydrological data. It is well known that the rainfall monitoring station is more extensive than the river flow monitoring station. Therefore, the Malino Catchment Area was selected to illustrate the theory of four tank components. The 1st tank (tank A) has two horizontal outlets (Qa1 and Qa2) and one vertical outlet (Ia); the 2nd tank (tank B) has one horizontal outlet (Qb) and one vertical outlet (Ib); the 3rd tank (tank C) has the same conceptual structure as tanks A and B; and the 4th tank (tank D) has only one horizontal outlet (Qd). To ensure that the tank model represents vertical and horizontal flows in a watershed region, the flows (Qa1, Qa2, Qb, Qc, and Qd) are predicted to accumulate in one flow, more or less, and must equal the measured discharge (Qo) at the specified time. Rainfall and evapotranspiration data are required to calculate this model. The 264.55 km2 (25902 ha) research area has an elevation range of 400–2400 masl. The findings for land use are dominated by plantations (41.01%), forests (40.79%), rice fields (15.44%), and residential areas (0.96%). In the calibration of the tank model, R2 is evaluated at 0.560% (good) and Nash–Sutcliffe efficiency is evaluated at 0.526% (good) to ensure that the model can represent the distribution of water flow components. Additionally, the measurements for the total water flow (Qtotal) were 13702 m3/y with a total rainfall of 3996 mm/y. Furthermore, surface flow accounts for 77.26% of the total runoff water, while intermediate flow accounts for 20.25%.

Automated solid phase DNA extraction on a lab-on-a-disc with two-degrees of freedom instrumentation

BackgroundLab-on-a-disc (LoaD) technology has emerged as a transformative approach for point-of-care diagnostics and high-throughput testing. The promise of integrating multiple laboratory functions onto a single integrated platform has significant implications for healthcare, especially in resource-limited settings. However, one of the primary challenges faced in the design and manufacture of LoaD devices is the integration of effective valving mechanisms. These valves are essential for fluid control and routing, but their intricacy often leads to complexities in design and increased vulnerability to failure. This emphasizes the need for improved designs and manufacturing processes without complex, integrated valving mechanisms. (96) ResultsWe describe a fully automated biological workflow and reagent actuation on a LoaD device without an integrated valving system. The Two Degrees-of-Freedom (2DoF) custom centrifuge alters the centre of rotation, facilitating fluid flow direction changes on the microfluidic platform through a custom programmed interface. A novel 360-degree fluid manipulation approach via secondary planetary gear motion enabled sequential assay reagent actuation without embedded valve triggering, with the addition of infinite incubation times and efficient use of platform realty. The simplified LoaD platform uses clever design, with intermediate flow chambers to avoid cross contamination between reagent steps. Notably, the optimized LoaD platform demonstrated a two-fold DNA yield at higher HEK-293 cell concentrations compared to commercially available spin-column kits. This significantly simplified LoaD platform successfully automated a common, complex workflow without inhibiting DNA purification. (129) SignificanceThis system exhibits the clever coupling of both 2DoF and centrifugal microfluidics to create an autonomous testing package capable of eradicating the need for complex valving systems to automate biological workflows on LoaDs. This automated system has outperformed commercially available DNA extraction kits for higher cell counts. The platform's elimination of valve requirements ensures unlimited sample incubation times and enhances reliability, making it a straightforward option for automated biological workflows, particularly in diagnostics. (73)

Contourite stratigraphic models linked to the light intermediate versus dense deep Mediterranean water flow regime variations (Alboran Sea, SW Mediterranean)

Several water masses are involved in the circulation of oceans, their bottom layers impacting on sedimentation through contourites. The majority of palaeoceanographic studies on regional contourites are performed for one water mass despite that their joint study would offer relevant clues to understand past ocean and climate interaction. This works presents for the first time a an analysis about the impact of the Light Intermediate Mediterranean (LMW) and Dense Deep Mediterranean (DMW) bottom currents on the sedimentation in the Alboran Sea (SW Mediterranean) and its paleoceanographic significance in response to climatic oscillations from the last glacial period to the Holocene. To do this, an integration of chronostratigraphical, sedimentological, and compositional data is carried out from contourites formed by those water masses. That integration enable us to define three distinct contourite stratigraphic models. (I) The contourite terrace model, characterized by coarse-grained contourites, which is an archive of the interplay between the high-energy Atlantic Water-LMW interface and glacioeustasy from the Younger Dryas (YD) to the Holocene. (II) The contourite drift models, which are archives of rapid ocean-climate coupled fluctuations since 29.5 kyr. They comprise coarse-grained contourites formed by a relatively fast LMW and fine-grained contourites formed by a relatively weak DMW, except for the Heinrich Stadials HS3 to HS1 and YD when coarse-grained contourites were deposited. (III) The contourite/turbidite mixed model represents another archive of DMW and glacioeustasy interplay from the end of the late Pleistocene to Holocene.That contourite stratigraphy allows us to infer for the first time the relative variability of the LMW versus DMW flow regimes, which records differences and similarities. The similarities indicate that the LMW and DMW fluctuations occur in parallel at millennial and centennial time scales. The differences refer to the overall higher velocity of LMW versus DMW; the magnitude changes in velocities that are lower for LMW and higher for DMW; the recognition of three short ventilation events (a, b, c) during HS1 and HS2 for only DMW; and the distinct LMW and DMW responses to the onset of glacial conditions and return to interglacial conditions during the HSs, YD and Holocene cold periods.The proposed contourite stratigraphic models can be applied for other areas in the Mediterranean margins to identify and correlate the LMW and DMW palaeoceanographic events throughout this sea. The findings suggest that the different water masses that make up the water column must be seriously considered to fully understand palaeoceanographic and palaeoclimatic studies based on contourites. This is because their distinct impact on sedimentation may provide new insights into their different palaeoceanographic responses to rapid climatic oscillations and their triggering mechanisms.

A Critical Evaluation of Streamflow Estimation of an Ungauged Watershed using a Gauged Watershed of Same River Basin – Case of Nilwala River Basin

Transferring hydrological model parameters of a nearby gauged watershed to an ungauged watershed is being widely practiced to predict streamflow in the ungauged watershed. However, proper conclusions on transferring data from the main to sub-watershed and vice versa need to be established, then only watershed managers can plan where to locate or ensure optimum use of resources when establishing gauging stations. Therefore, the present study aimed to evaluate the performance of spatial transferability by using the Tank Model, which was initially calibrated to daily streamflow from water year 2008/09 to 2017/18 observed at two gauged watersheds in Nilwala River Basin, and then transferred from main to sub-watershed and vice versa. The efficiency of predictions under two parameter transferability scenarios was highly acceptable where the Mean Ratio of Absolute Error (MRAE) values were 0.35-0.39 and, the accuracy of annual water balance was 91.8%-93.3%. Most importantly, the best results were in the intermediate flow regime with an accuracy of 61%-70%. The monthly-scaled streamflow indicated an accuracy of 83%-92%. The present study demonstrated the liability of the Tank Model for successful estimation of daily streamflow with an average accuracy of 63% under spatial parameter transferability thereby with only a single wellmanaged streamflow gauging station, Tank Model can be applied for sustainable water resources management in similar ungauged watersheds of the basin.

Laboratory observations of solute transport in groundwater basins

This paper introduces a method of groundwater pollution source identification obtained from laboratory by a physical instrument of Flow System Sand-Box Model. A Unit basin of a simple flow system and a Tóthian basin of a hierarchically nested flow structure are introduced as case studies. We add step-input solutes at recharge zones, separately or simultaneously, to obtain the breakthrough curves (BTCs) at each discharge zone. For the Unit basin, its BTC shows a gradual upward trend with a decreasing slope but with two more pronounced steps, which differs a lot from previous results of analytical and numerical solutions. These steps are caused by the settings of the current physical instrument as no solutes are input at the upper two discharge ports. For the Tóthian basin, internal steps may exist due to the late-time arrival of intermediate and regional groundwater flow systems. Although the Unit basin and Tóthian basin can both have internal steps in the BTCs, they are due to different reasons. By jointly solving solute mass balance equations with water mass balance equations, the circulation rate for each flow system is calculated, which quantitatively explains the phenomena encountered in the experiment and highlights the important contributions of intermediate and regional flow systems to the entire groundwater circulation. We indirectly obtain the pulse-input BTCs by deriving the step-input BTCs respective to time, which is also the residence time distribution (RTD) of the groundwater basin, that the groundwater pollution sources can be identified. The pulse-input BTC is characterized by peaks and sloping tails. The peaks correspond to the intermediate and regional groundwater flow systems. The sloping tails indicate the rate at which solutes are flushed out or contaminants fade away. By inputting tap water into the groundwater basin to purify the contaminations, we conduct self-purification experiments. The shapes of the solute-input curves and the self-purification curves are systematically symmetrical. As the self-purification experiment has less external interference, it is possible to use the self-purification curves to characterize and identify the groundwater flow system. This study proposes a physical method for identifying sources of groundwater contamination, and achieves a comprehensive understanding of the law of solute transport in groundwater basins, which could guide the prevention of non-point contamination at the basin scale.