Flow Path Direction Research Articles

Interaction of focused recharge and deep groundwater discharge near a wetland: A study in the Ordos Basin, China

Groundwater mounds and depressions induced by rainfall and evapotranspiration near wetlands/lakes have been widely observed, but their effects on groundwater flow field are poorly known. Here, a sandy hillslope near a wetland in the Ordos Plateau, China, which has a semi-arid climate, is selected for investigation. After identifying temporary groundwater mounds/depressions based on three water level observation wells, a HYDRUS-2D model is setup to obtain the highly transient daily flow field. The variable thickness of unsaturated zone near the wetland, which controls soil water content and unsaturated hydraulic conductivity, is found to be responsible for groundwater mounds resulting from focused recharge and groundwater depressions resulting from nonuniform evapotranspiration. On nonrainy days, evapotranspiration in the lowland is supported by flowpaths from regional groundwater discharge, and in the slope is supported by a flow cell from the upland to the upper part of the slope, which causes water table recession in the upland. On rainy days, focused recharge in the lowland leads to two temporary local flow cells, which break the regional groundwater discharge flowpaths into two temporary flow cells. The two temporary flow cells toward the upland contribute to water table rises in the uplandMoreover, we find focused recharge in rainy days does not change the overall direction of flowpaths controlled by regional groundwater discharge and strong evapotranspiration, but only increase the tortuosity of flowpaths. By coupling daily atmospheric conditions and regional groundwater discharge, this study has implications for groundwater recharge estimation and future groundwater modelling in arid regions.

Subsurface Contaminant Transport Analysis for Flowpath Direction in Katni Watershed, Madhya Pradesh, India Using GIS and Groundwater Modeling Approach

The current study aims to identify the pathways of pollutants and travel time of contamination using Remote Sensing and GIS approach. In sight of this, to evaluate hazard, groundwater contaminant transport is analyzed by using the ground water model in Katni River watershed. Darcy flow and velocity have been used for contaminant transport analysis, which is one of the components of Arc GIS in Groundwater module extension. Modeling tools such as Kriging, Darcy Flow/Velocity and Linear Directional Mean were used to identify the groundwater path lines and travel time. The analysis was done by taking into account of vulnerable areas, the location of contaminant sources and infected wells and their well field. The hydro-geological properties of underlying rocks along with surface and groundwater elevation are also considered by simulations, found that flow lines intersect with the Katni River in numerous places and flow lines converge towards wells in the study area, implying contaminated water is carried to these areas from all directions. Consequentially, the quality of the surface and groundwater is determining the quality of water in the wells Keywords: Contaminant Transport Analysis, Pathways and Travel Time, Groundwater Flow Model, Darcy Flow, GIS, Kriging

Research on the Mechanism of Thermoacoustic Phenomena

Thermoacoustic self-excited vibration is a phenomenon in which the air in a tube becomes unstable by a temperature gradient and begins to vibrate at the resonance frequency and grows to a certain steady amplitude. Regarding the mechanism of thermoacoustic phenomenon, there is no literature that clearly describes the cause of self-excited. In this study, we created the simulation model using cellular automaton method for the thermoacoustic device using the one-dimensional acoustic tube. We also modeled the heat source with a temperature gradient. At that time, the fact that the excitation amount has a phase difference with respect to the particle velocity at the vibration point is derived from the one-dimensional heat conduction in the cross-sectional direction of the air vibrating in the pipe having a temperature gradient in the flow path direction and the vibration amount is derived. We confirmed the validity of our idea in the experiment.

Experimental research on the performance of a rotating detonation combustor with a turbine guide vane

Rotating detonation engines (RDEs) have received significant attention from industry and academia alike, owing to their numerous advantages, such as pressure gain combustion, high operation frequency, and near-constant thrust output. Furthermore, there is considerable interest in combining RDEs with gas-turbine engines to further improve their overall system performance. This study examines the propagation characteristics of continuous rotating detonation waves (CRDWs) with a turbine guide vane (TGV). We develop an experimental model of a hydrogen–air rotating detonation combustor integrated with a TGV section and record the high-frequency pressure oscillations and static pressure upstream and downstream of the TGV section. The experimental results indicate that: the interactions between CRDW and the turbine blade cause the reflected shock propagating backwards to the combustor. Both pressure oscillation amplitude and static pressure decline at downstream of TGV. Notably, the pressure oscillation attenuation by the TGV is influenced by the direction of CRDW propagation. When the CRDW propagation direction and the flow path direction of the guide vane are opposite to each other, the pressure oscillation attenuation increases. The findings obtained herein provide benchmark data that help improve the fundamental understanding of CRDW and TGV interaction, and can be used to develop detonation-based propulsion technology.

流路に直交方向の加振を利用した油圧微粒子励振型制御弁の試作と評価

流路に直交方向の加振を利用した油圧微粒子励振型制御弁の試作と評価

Fabrication and Evaluation of Hydraulic Particle Excitation Valve Vibrated Perpendicularly to Direction of Flow Path

Fabrication and Evaluation of Hydraulic Particle Excitation Valve Vibrated Perpendicularly to Direction of Flow Path

Uncertainty in the modelling of spatial and temporal patterns of shallow groundwater flow paths: The role of geological and hydrological site information

Understanding the hydrological and hydrogeochemical responses of hillslopes and other small scale groundwater systems requires mapping the velocity and direction of groundwater flow relative to the controlling subsurface material features. Since point observations of subsurface materials and groundwater head are often the basis for modelling these complex, dynamic, three-dimensional systems, considerable uncertainties are inevitable, but are rarely assessed. This study explored whether piezometric head data measured at high spatial and temporal resolution over six years at a hillslope research site provided sufficient information to determine the flow paths that transfer nitrate leached from the soil zone through the shallow saturated zone into a nearby wetland and stream. Transient groundwater flow paths were modelled using MODFLOW and MODPATH, with spatial patterns of hydraulic conductivity in the three material layers at the site being estimated by regularised pilot point calibration using PEST, constrained by slug test estimates of saturated hydraulic conductivity at several locations. Subsequent Null Space Monte Carlo uncertainty analysis showed that this data was not sufficient to definitively determine the spatial pattern of hydraulic conductivity at the site, although modelled water table dynamics matched the measured heads with acceptable accuracy in space and time. Particle tracking analysis predicted that the saturated flow direction was similar throughout the year as the water table rose and fell, but was not aligned with either the ground surface or subsurface material contours; indeed the subsurface material layers, having relatively similar hydraulic properties, appeared to have little effect on saturated water flow at the site. Flow path uncertainty analysis showed that, while accurate flow path direction or velocity could not be determined on the basis of the available head and slug test data alone, the origin of well water samples relative to the material layers and site contour could still be broadly deduced. This study highlights both the challenge of collecting suitably informative field data with which to characterise subsurface hydrology, and the power of modern calibration and uncertainty modelling techniques to assess flow path uncertainty in hillslopes and other small scale systems.

Definición de zonas de recarga y descarga de agua subterránea a partir de indicadores superficiales: centro-sur de la Mesa Central, México

The aim of this paper is the delimitation of groundwater recharge and discharge zones in the centre-south portion of the Mesa Central. This was achieved using groundwater flow systems theory, which has proved to be a valuable tool since it considers a systemic perspective of the environment, integrating several natural elements. There are various physical, chemical and biological processes generated in the subsoil within which groundwater is incorporated. This involvement is caused by the natural gravitational movement of groundwater which is manifested on the surface by contrasting evidences in the recharge and discharge zones. Therefore, the objective of this paper includes the demonstration of the usefulness of the analysis of those indicators to locate priority areas and also provides an approximation of groundwater functioning. The definition of recharge and discharge zones included the analysis of maps describing soil type, vegetation, topographic elevation, groundwater flowpath direction, springs, and presence of natural water bodies. Such analysis was carried out through the overlaying tool of ArcMap™ software. The results suggest that the highlands of Fría, San Miguelito and Santa Bárbara as recharge zones. Natural discharge zones were originally present in the plain of the Aguascalientes tectonic depression, and some flat and topographic low zones in the vicinity of Altos de Jalisco, Santa María del Río and Ojuelos.

Distribution of Pressure Fluctuations in a Prototype Pump Turbine at Pump Mode

Pressure fluctuations are very important characteristics in pump turbine's operation. Many researches have focused on the characteristics (amplitude and frequencies) of pressure fluctuations at specific locations, but little researches mentioned the distribution of pressure fluctuations in a pump turbine. In this paper, 3D numerical simulations using SSTk − ω turbulence model were carried out to predict the pressure fluctuations distribution in a prototype pump turbine at pump mode. Three operating points with different mass flow rates and different guide vanes’ openings were simulated. The numerical results show how pressure fluctuations at blade passing frequency (BPF) and its harmonics vary along the whole flow path direction, as well as along the circumferential direction. BPF is the first dominant frequency in vaneless space. Pressure fluctuation component at this frequency rapidly decays towards upstream (to draft tube) and downstream (to spiral casing). In contrast, pressure fluctuations component at 3BPF spreads to upstream and downstream with almost constant amplitude. Amplitude and frequencies of pressure fluctuations also vary along different circumferential locations in vaneless space. When the mass flow and guide vanes’ opening are different, the distribution of pressure fluctuations along the two directions is different basically.

Assessing landscape structure and pattern fragmentation in semiarid ecosystems using patch-size distributions

Spatial vegetation patterns are recognized as sources of valuable information that can be used to infer the state and functionality of semiarid ecosystems, particularly in the context of both climate and land use change. Recent studies have suggested that the patch-size distribution of vegetation in drylands can be described using power-law metrics, and that these scale-free distributions deviate from power-law linearity with characteristic scale lengths under the effects of increasing aridity or human disturbance, providing an early sign of desertification. These findings have been questioned by several modeling approaches, which have identified the presence of characteristic scale lengths on the patch-size distribution of semiarid periodic landscapes. We analyze the relationship between fragmentation of vegetation patterns and their patch-size distributions in semiarid landscapes showing different degree of periodicity (i.e., banding). Our assessment is based on the study of vegetation patterns derived from remote sensing in a series of semiarid Australian Mulga shrublands subjected to different disturbance levels. We use the patch-size probability density and cumulative probability distribution functions from both nondirectional and downslope analyses of the vegetation patterns. Our results indicate that the shape of the patch-size distribution of vegetation changes with the methodology of analysis applied and specific landscape traits, breaking the universal applicability of the power-law metrics. Characteristic scale lengths are detected in (quasi) periodic banded ecosystems when the methodology of analysis accounts for critical landscape anisotropies, using downslope transects in the direction of flow paths. In addition, a common signal of fragmentation is observed: the largest vegetation patches become increasingly less abundant under the effects of disturbance. This effect also explains deviations from power-law behavior in disturbed vegetation which originally showed scale-free patterns. Overall, our results emphasize the complexity of structure assessment in dryland ecosystems, while recognizing the usefulness of the patch-size distribution of vegetation for monitoring semiarid ecosystems, especially through the cumulative probability distributions, which showed high sensitivity to fragmentation of the vegetation patterns. We suggest that preserving large vegetation patches is a critical task for the maintenance of the ecosystem structure and functionality.

Development of GIS-based models to predict plant community structure in relation to western juniper establishment

During the past 130 years, western juniper ( Juniperus occidentalis Hook.) has rapidly expanded into sagebrush communities impacting plant structure and function. Predictions of intercanopy shrub density and cover with woodland development can provide insight into site condition and ecological resiliency in western juniper encroached areas. The purpose of this study is to model shrub density and cover in relation to juniper competition across a heterogeneous landscape in a southeast Oregon watershed. Independent variables included in model development were derived from high-resolution color imagery, a 10 m digital elevation model, and field-based vegetation and soil moisture measurements. Juniper cover and three intercanopy classes, representing different levels of juniper competition, were delineated from 1:5000 scale color (RGB) imagery. A competition index was produced from the classified image representing a gradient of potential competition with juniper. An integrated moisture index was generated representing variability in soil moisture due to hillslope solar radiation, curvature of the landscape and flow path direction and flow accumulation (flow path density). Plant density, plant cover, and percent soil moisture (gravimetric) were measured from 10 m × 10 m plots located throughout the watershed study area. Multiple stepwise regression produced the best-fit model for predicting plant density or cover for mountain big sagebrush ( Artemesia tridentata ssp. vaseyana Beetle), bluebunch wheatgrass ( Pseudoroegneria spicata (Pursh)), and all shrub species combined. The prediction of total shrub density was significantly greater than expected by chance ( p < 0.001), with a 0.865 coefficient of determination. Total shrub cover also had a high correlation between observed values and environmental gradients ( R 2 = 0.773). These data can be used by land managers to assess the change in plant structure with increasing juniper canopy cover, a measure important for monitoring impacts from juniper woodland establishment.

Water quality changes in hyporheic flow paths between a large gravel bed river and off-channel alcoves in Oregon, USA

Changes in water quality that occur as water flows along hyporheic flow paths may have important effects on surface water quality and aquatic habitat, yet very few studies have examined these hyporheic processes along large gravel bed rivers. To determine water quality changes associated with hyporheic flow along the Willamette River, Oregon, we studied hyporheic flow at six-bar deposit sites positioned between the main river channel and connected lentic alcoves. We installed piezometers and wells at each site and measured water levels and water quality in river, hyporheic and alcove water. Piezometric surfaces along with substrate characteristics were used to determine hyporheic flow path direction and hyporheic flow rate. At all sites, hyporheic flow moved from the river through bar deposits into alcove surface water. Stable isotope analysis showed little influence of upwelling groundwater. At a majority of sites, hyporheic dissolved oxygen and ammonium decreased relative to river water, and hyporheic specific conductance, nitrate and soluble reactive phosphorous increased relative to river water. At three sites, hyporheic temperature decreased 3–7°C relative to river water; there was less temperature change at the other three sites. At the two sites with the highest hyporheic flow rates, hyporheic cooling was propagated into the alcove surface water. Hyporheic changes had the greatest effect on alcove water quality at sites with highly permeable substrates and high-hyporheic flow rates. The best approach to enhancing hyporheic flows and associated water quality functions is through restoring fluviogeomorphic channel processes that create and maintain high-permeability gravel deposits conducive to hyporheic flow. Copyright © 2006 John Wiley & Sons, Ltd.

A Genetic Algorithm for the Design of a Single-Row Layout in Automated Manufacturing Systems

In this paper the machine layout problem with a linear single-row flow path in automated manufacturing systems is investigated. Traditional machine layout approaches can produce an inappropriate layout design because they often do not consider flow path characteristics, such as flow path configuration and feasible flow path direction. This paper investigates the effects of such flow path characteristics on machine layouts. There are six flow-line analysis methods reported in the literature. Of these, the two best methods (FLA-5 for bidirectional flow lines and FLA-6 for unidirectional flow lines) are considered here. Two heuristic search algorithms, one combining FLA-5 and a genetic algorithm and other combining FLA-6 and a genetic algorithm, are proposed. A wide variety of data sets are used to test the proposed algorithms.

Control of crater morphology on flow path direction of Soufrière‐type pyroclastic flows

We present a model of fountain collapse for small‐scale (Soufrière‐type) explosive eruptions that relates the asymmetry of a volcanic crater (e.g., the presence of crater notches) with the emplacement direction of pyroclastic flows. Analysis of two‐dimensional simulations of compressible fluids emanating from asymmetric nozzles shows that under sonic to supersonic conditions, the streamline of a jet can become tilted. The inclination of the streamline increases with greater slant angle of the nozzle and with increasing exit pressure. Using the two‐dimensional simulations as analogues to volcanic eruptions, we propose that pyroclastic ejecta within the inner core of an erupting jet column can become asymmetrically focused before collapsing at fountain heights of a few hundred meters above the crater exit. The ensuing pyroclastic flows associated with fountain collapse thus become directional in character with flow orientation controlled by crater geometry and eruption exit pressure. The model applies to volcanoes with vertical conduits and crater to vent geometries that act as effective sonic to supersonic jet nozzles. We propose that the 1984 eruption of Mayon volcano fits this model. In the second phase of this eruption a prominent crater notch imparted a southeastward tilt to the basal gas thrust region of the eruption column. In turn, this led to the discharge of pyroclastic flows onto the southeast flank of the volcano.

Machine layout with a linear single-row flow path in an automated manufacturing system

This paper investigates the machine layout problem with a linear single-row flow path within an automated manufacturing system. Traditional machine layout approaches can produce inappropriate layout designs because they often do not consider flow path characteristics, such as flow path configuration and feasible flow path direction. This paper investigates the effects of such flow path characteristics on machine layouts. A two-phase layout procedure that combines flow line analysis with simulated annealing is proposed. The procedure can be employed using a variety of evaluation criteria (minimize total flow distance, maximize number of in-sequence movements, and so on). Different layout procedures can be obtained by varying the flow line analysis method and temperature reduction strategy employed for simulated annealing. Experiments are performed to test the performance of different layout procedures for different combinations of flow path characteristics and quantities of machines. The experimental results provide vital information on selecting appropriate flow line analysis methods and temperature reduction strategies for different layout problems. Furthermore, the results will help designers determine appropriate evaluation criteria for different layout problems.

The Effects of Vertical Error in Digital Elevation Models on the Determination of Flow-path Direction

This study examines the effects of vertical error in digital elevation models (DEMs) on the determination of flow-path direction. Flow-path data are widely used in hydrologic modeling applications, but the sensitivity of flow-path algorithms to error in DEMs has not been addressed in a systematic fashion. This study employs a simulation-based approach in which numerous realizations of an error-free DEM are produced that conform to different assumptions about the statistical and spatial properties of error. Results suggest that extreme caution should be used when employing flow-path data derived from DEMs, especially if there is reason to suspect that vertical error is large or positively correlated with terrain slope. Flow-path data are least reliable in areas of low slope where even small amounts of error can induce significant changes in flow-path direction. In some cases, the level of reliability is only marginally better than the level that would be obtained if flow paths were assigned on a random basis.

Regional groundwater flow in sedimentary basins in the U.K.

Summary The U.K. contains seven groundwater provinces. Regional groundwater flow systems occur in these provinces above an essentially impermeable basement of varying age. The pattern of flow in the U.K. is strongly influenced by the distribution of the Permo-Triassic sandstones. Intermediate flow systems are encouraged by the scarp and vale topography that has developed as a consequence of the alternating sequence of aquifers and aquicludes in the Mesozoic. Regional changes in groundwater chemistry reveal the direction of flow paths, and isotopic ratios and inert gas contents give an indication of the residence time of water in the flow systems. The composition of the groundwater in deep systems has been modified by shale-membrane filtration. Density settling may be a feature in thick relatively homogeneous aquifers.