Conduit Flow Research Articles

Nitrate sources and biogeochemical processes in karst underground rivers impacted by different anthropogenic input characteristics

Nitrate is one of the most common pollution sources in groundwater, particularly in highly vulnerable karst aquifers. The potential for nitrification and denitrification within karst aquifers varies in different settings depending on the extent of anthropogenic inputs, so that accurate identification of nitrate sources can be difficult. Geochemical data and dual nitrate isotopes were measured in this study, incorporating a Bayesian isotopic mixing model, and used to identify nitrate sources, nitrification and denitrification, and quantitatively determine nitrate sources under different extents of anthropogenic inputs in three karst catchments within Chongqing Municipality, SW China: Laolongdong (an urbanized area), Qingmuguan (a suburban village), and Shuifang Spring (a protected natural area). At the Laolongdong catchment, the groundwater was in a reducing condition and enriched in δ15NNO3 (averaging 18.9 ± 6.9‰) and δ18ONO3 (averaging 8.5 ± 4.6‰). Manure and sewage waste were the main contributing nitrate sources. A slope of 1.8: 1 of the dual isotopes suggested a denitrification process occurring in anaerobic conduit flow. Within the Qingmuguan catchment, groundwater had average δ15NNO3 and δ18ONO3 values of 9.7 ± 3.5‰, and 1.9 ± 3.4‰, respectively. The data showed evidence for nitrification, and the contribution of soil organic nitrogen was 52.1%, followed by a contribution of 44.8% from manure and wastewater. At the Shuifang Spring catchment, the mean δ15NNO3 and δ18ONO3 values in groundwater were 8.8 ± 2.9‰, 2.3 ± 4.6‰, respectively. Nitrification was the dominant process and most of the nitrate was derived from soil organic nitrogen. This study suggests that karst underground rivers overlain by urban land use undergo denitrification, while the suburban and relatively pristine karst aquifers are dominated by nitrification, allowing development of a conceptual model for nitrate sources and transformations in karst aquifers from the categories of land use (i.e., urban, suburban, and pristine areas). Main findingAnthropogenic activities can change biogeochemical nitrogen dynamics of vulnerable karst aquifers, such that the groundwater overlain by an urban settlement has undergone denitrification, while suburban and pristine areas have been dominated by nitrification.

Discontinuous finite volume element method for Darcy flows in fractured porous media

This paper presents a numerical simulation of the single phase Darcy flow model in two-dimensional fractured porous media. Under some physically consistent coupling conditions, the model can be described as a reduced problem by coupling the bulk problem in porous matrix and the fracture problem in fractures. Flows are governed by the primal form of the Darcy’s equations for both the bulk and fractures. The coupled discontinuous finite volume element methods and conforming finite element method are adopted to solve the bulk problem and fracture problem, respectively. We theoretically analyze the well-posedness of the discrete problem, and derive optimal error estimates in standard L2 error and broken H1 error. Numerical experiments include not only the fractures with high permeability as the prior flow conduit, but also the fractures with low permeability as the flow barrier, which demonstrate the accuracy, flexibility and robustness of our discrete formulation for complicated networks of fractures in porous media domain.

Determination of recharge, storage and flow characteristics of a karst aquifer using multi-method approaches (Kocaeli, Turkey)

Recharge, storage and flow characteristics of a karst aquifer were identified by correlating the results acquired from hydrogeological and speleological studies, stream/spring hydrographs, dye tracer tests, and hydrogeochemical analyses. Drinking water needs of the city of Kocaeli (Turkey) are partly supplied by karst springs (discharge 20–843 L/s) and the karst aquifer provides baseflow to streams that flow into Yuvacik Reservoir. A multi-variate dataset for characterization of the hydrological behavior of the karst aquifer was created. Stream hydrographs indicated that the aquifer comprises interconnected multipartite reservoirs, exhibiting groundwater residence times of 11–125 days. Recession coefficients of these reservoirs, obtained from master baseflow-recession curves, were 0.008–0.092 day−1. Dye tracer tests showed that groundwater velocities between recharge and discharge points were 483–1,328 m/day. Conduit flow characteristics were generally dominant in the upper reservoirs of the karst aquifer, characterized with high recession coefficients (0.017–0.092 day−1). Deeper reservoirs had a small baseflow recession coefficient (0.008 day−1). Autogenic point infiltration mechanisms were important in the recharge of many karst springs that discharged at high elevations (603–830 m amsl). However, autogenic diffusive infiltration regions (e.g. karst plateaus at high elevations) contributed to the recharge. Dye tracer tests and cave mapping revealed that depression points, allowing fast recharge, require special attention for protection and sustainable management of the karst aquifer. The results obtained from multiple methods and their correlation help to characterize the complex hydrodynamics of karst systems, and they can guide local authorities when assigning protection zones to locally important karst aquifers.

Analytical Methodology for the Discharge-Stage Relation of Flexible Shape Palmer-Bowlus Flumes

AbstractThe flexible shape Palmer-Bowlus flume is a simple device for flow measurement in free-surface flow circular channels and conduits. In this study, the discharge-stage relation for Palmer-Bo...

Ferroelectric Domain Wall Memristor.

A domain wall‐enabled memristor is created, in thin film lithium niobate capacitors, which shows up to twelve orders of magnitude variation in resistance. Such dramatic changes are caused by the injection of strongly inclined conducting ferroelectric domain walls, which provide conduits for current flow between electrodes. Varying the magnitude of the applied electric‐field pulse, used to induce switching, alters the extent to which polarization reversal occurs; this systematically changes the density of the injected conducting domain walls in the ferroelectric layer and hence the resistivity of the capacitor structure as a whole. Hundreds of distinct conductance states can be produced, with current maxima achieved around the coercive voltage, where domain wall density is greatest, and minima associated with the almost fully switched ferroelectric (few domain walls). Significantly, this “domain wall memristor” demonstrates a plasticity effect: when a succession of voltage pulses of constant magnitude is applied, the resistance changes. Resistance plasticity opens the way for the domain wall memristor to be considered for artificial synapse applications in neuromorphic circuits.

A three-scale index for flow in karst conduits in carbonate rocks

A three-scale model for flow in karst conduit networks in fractured carbonates is rigorously constructed based on a reiterated homogenization procedure. The first upscaling, performed from the high-fidelity flow model, is based on sequential partially and fully topological model reduction procedures considering two discrete networks of solution-enlarged fractures and conduits. The subsequent macroscopization procedure projects the reduced model into the cells of a coarse computational grid, where homogenized equivalent properties are numerically constructed. Such a two-level upscaling gives rise to a macroscopic flow model characterized by mass-transfer functions between the geological structures. A notable consequence of the approach proposed herein is the appearance of a new karst index concept, whose underlying physics relies on the generalization of the traditional Peaceman’s theory of well index. Such a concept rules the mass exchange between conduits and matrix and can be extended to the general scenario of coupled flow in multi-branch karst conduit systems, displaying general non-circular cross sections and surrounding damage zones. The downscaling representation for the karst index can be further explored to improve accuracy of the exchange coefficient between the geological objects. Numerical experiments are carried-out showing the magnitude of the index for certain conduit and fracture arrangements, along with illustrating the impact upon flow patterns.

Numerical Analysis of Water and Air in Venturi Tube to Produce Micro-Bubbles

Two-phase flow regimes are affected by conduit position, alignment, geometry, flow direction, physical characteristics, and flow rate of each phase as well as the heat flux toward the boundaries. Due to the importance of two-phase flow, numerous regimes have been identified. The first step in studying micro-bubble formation inside a venturi tube is to recognize the type of flow regimes. In this study, which is devoted to the study of micro-bubble formation, a numerical investigation by OpenFOAM software and a VOF model was conducted. Results suggest that flow regime inside the venturi tube is roughly similar to flow regimes inside the horizontal tubes. For having bubble flow and consequently forming micro-bubble, flow rate of gas phase should be very smaller than liquid phase flow rate while the air inlet diameter should be chosen much smaller than water input diameter. Numerical simulations indicate that the best results are achieved for the water velocity of about 1-2m/s.

Determinants of Reactive Hyperemia Measured by Near‐Infrared Diffuse Correlation Spectroscopy

Recent work has shown that measures of reactive hyperemia (RH) are temporally dissociated when assessed by Doppler ultrasound (i.e. upstream conduit blood flow) and near‐infrared diffuse correlation spectroscopy (NIR‐DCS; a direct measure of microvascular perfusion). To probe the physiological mechanisms underlying these discordant responses, we used Doppler ultrasound (Vivid‐i, GE) and NIR‐DCS (MetaOx, ISS Inc.) to measure RH in 13 healthy young adults (7F, 22.9 ± 3.3 yrs) under varying physiological conditions. First, with the arm at heart level (N), we manipulated the duration of limb ischemia (3 vs 6 min) to assess the impact of the ischemic stimulus. Second, we reduced/increased forearm perfusion pressure (FPP) by positioning the experimental arm above (60°) or below (30°) the heart, and measured RH following 3 min of occlusion. The 6min‐N trial was always conducted first, followed by the three 3‐min trials in randomized order. FPP was measured using finger photoplethysmography, corrected for the hydrostatic distance. For the 6min‐ and 3min‐N trials, resting BA blood flow was not different between conditions; however, baseline NIR‐DCS blood flow index (BFI) was lower during the 6min‐N trial than the 3min‐N trial (0.70 ± 0.40 vs 0.94 ± 0.41 cm2·10−8 AU, p < 0.01). As expected, the magnitude of peak BA blood flow during RH increased with increasing ischemia duration (341.9 ± 94.5 vs 284.9 ± 80.1 mL/min, 6min‐ vs 3min‐N, p = 0.03), as was peak NIR‐DCS derived BFI (3.11 ± 1.3 vs 2.54 ± 0.75 cm2·10−8 AU, p = 0.03). For the arm Above/Below trials, FPP was significantly lower in the Above position compared to Below (76.0 ± 5.4 vs 107.9 ± 5.9 mmHg, p < 0.01). Prior to cuff inflation, raising the arm above the heart also reduced BFI relative to the Below position (0.70 ± 0.26 vs 0.99 ± 0.51 cm2·10−8 AU, p = 0.03), whereas BA blood flow was similar between arm positions (23.4 ± 13.8 vs 32.1 ± 11.2 mL/min, p = 0.12). Following cuff deflation, peak BA blood flow (379.5 ± 143.5 vs 227.0 ± 63.9 mL/min, p < 0.01) and peak BFI (2.98 ± 1.00 vs 1.76 ± 0.59 cm2·10−8 AU, p <0.01) were higher with the arm Below the level of the heart compared to Above. The difference in peak BA blood flow was abolished however, when expressed as a % change from baseline (1198.8 ± 320.7 vs 1260.2 ± 817.8 %, Below vs Above, p = 0.79), whereas the difference in peak BFI was not (360.8 ± 170 vs 259.4 ± 64.8 %, p = 0.03). Remarkably, the RH BFI slope was nearly 3‐fold higher in the Below position compared to Above (0.14 ± 0.08 vs 0.05 ± 0.02, p < 0.01), but much smaller when manipulating the duration of ischemia (0.12 ± 0.04 vs 0.09 ± 0.04 cm2·10−8·s−1 AU, 3min‐ vs 6min‐N, p = 0.02), though this latter observation may have been due to an order effect. In toto, these results support previous findings that RH is dependent on the ischemic stimulus, regardless of the assessment technique, as the peak rates of BA blood flow and BFI were greater in the 6min‐N trial compared to the 3min‐N trial. Alternatively, the rate of microvascular reperfusion (i.e. BFI slope) is less affected by the ischemic stimulus to vasodilate and is instead primarily affected by changes in perfusion pressure, suggesting this measure may offer greater insight into the physiological mechanisms underlying microvascular function and reactive hyperemia.

Karakter dan Potensi Risiko Kerusakan Ekosistem Karst Cekungan Air Tanah Watuputih Kabupaten Rembang, Provinsi Jawa Tengah

The research area is a burgeoning karst area which is part of the Kendeng Kars area in Rembang Regency, where the karstification process continues and has a complex subsurface system. In addition to the karst area of the Watuputih Groundwater Basin (CAT) written in Presidential Decree Number 26 of 2011 point 124 is included in the CAT B classification, which is located across the regency between Rembang and Blora Regencies. The morphological changes caused by human beings and the sharing of mining activities and plans for the construction of a cement factory by PT SI and its subsidiaries such as PT SG are also investors such as PT SIR, PT RSI, PT GMM, PT BA, PT RBP, PT SAF, PT ICCI which have reached an area 493 hectares in Tegaldowo, Gunem District. These activities will directly or indirectly damage the ecosystem of caves, underground rivers and parental springs that are scattered in the Watuputih CAT area. The Bengawan Solo River, the Lusi River and the Tuyuhan River are large rivers that tipped in the Watuputih CAT area. There are 74 caves, 29 springs, 44 ponors in the Tegaldowo and Timbrangan areas, 10 caves and 3 springs in the Perhutani area. Morphological changes due to mining can affect the pattern of water distribution, where caves, springs and ponors have a very important role in controlling water supply, the degradation of the amount of water stored in the Watuputih CAT results in changes in the composition of the base flow (diffuse flow) compared to the total flow. Limestone mining will reduce the absorption function and the amount of diffuse water storage, on the contrary will increase conduit flow when it rains. If an area has criteria as karst and CAT areas then it must be a major concern in the sustainability of its ecosystem. Provide protection and stop all activities that can damage geological protected areas that have karst landscapes and water recharge, especially from small scale or massive mining activities. Provides an understanding of karst areas in the perspective of disaster risk reduction. It needs to be developed and informed to various parties across sectors and across administrations so that appropriate policies can be made as an ecological function. Keywords: Watuputih Groundwater Basin, Water Distribution, Ecosystems, Ecological Function, Protection

Characterizing flow release from the aquifer of Guntur Spring in Gunungsewu Karst Area, Indonesia

Karst aquifers have three flow components, namely conduit, fissure, and diffuse. This research was designed to characterize the flow release from the karst aquifer of Guntur Spring. It is part of the hydrogeological system Panggang Block, part of Gunungsewu Karst Area, Gunungkidul, the Special Region of Yogyakarta. The water level and discharge data from May 2018 to May 2019 were processed to create flow hydrographs. Two different methods were applied to measure discharge variation in one year, namely sudden injection in dry seasons and velocity area in rainy seasons. While baseflow separation analysis was employed to calculate the percentage of baseflow, recession constants computation was used to derive the three flow components of the karst aquifer. The recession constants, Kb (diffuse flow), Ki (fissure flow), and Kc (conduit flow), were calculated from nine selected flood events. From the hydrograph analysis, this research found that the average discharges in rainy and dry seasons were 56.7 l/s and 13.25 l/s, respectively. These relatively small flows are mainly because Guntur Spring is an epikarst spring with layers of limestone or thin aquifer. The recession constants were Kb=0.998, Ki=0.933, and Kc=0.500, meaning that Guntur Spring has three flow components, including diffuse, fissure, and conduit. Although the baseflow separation analysis found that the diffuse flow prevailed (93.07%), the influence of conduit and fissure flows was apparent, especially during rainy seasons. The Guntur Spring hydrograph analysis revealed that the average time to baseflow (Tb) and time to peak (Tp) was rather prolonged. Supporting this finding was the mean value of Kc that categorized the recession as medium and signified that the conduit fractures developing in Guntur Spring were not extensive. As a conclusion, diffuse flow mainly characterizes the discharge of Guntur Spring with some indications of growing fissures and conduits.

Baseflow separation of some springs in the Jonggrangan karst area, Java, Indonesia

Karst aquifer flow can be divided into diffuse, fissure, and conduit. Diffuse (base) flow plays a role in maintaining the continuity of karst springs. This research was conducted in the Kiskendo underground river, Mudal spring, and Anjani underground river, which is located in the Jonggrangan karst area, to determine variations in the base flow proportion in the three locations. Water level and discharge data are collected for a year (March 2018-March 2019). The water level and discharge data pairs are then used to create a rating curve to obtain flow hydrographs during the study period. Several flood events are then chosen to calculate the baseflow recession constant. Separation of base flow is automatically carried out to determine the percentage of base flow during the study period. The results showed that all three locations had fluctuating hydrographs that followed the seasons, with many peaks of flood hydrographs occurred following rainfall events. This condition shows that all three locations have developed aquifers. Although this is the case, flows in the three locations tend to be dominated by base flow both during the dry and rainy seasons, which indicates the capacity of aquifers to store groundwater is still good. Besides, the results of the base flow separation show that the percentage increases during the dry season and decreases during the rainy season. The decrease in the percentage of base flow during the rainy season is due to the contribution of direct flow (fissure and conduit) to the karstic aquifer.

A comprehensive approach to karst identification and groutability evaluation – A case study of the Dehou reservoir, SW China

Yunnan Province in SW China has one of the most developed karst terrains in China and has been historically affected by sinkholes and other instability phenomena caused by unpredictable cavity formation and well-developed underground hydraulic conduits. During construction of a karst seepage control reservoir project (grouting of a 4.6-km long anti-seepage curtain) in Yunnan province, some typical detection methods (electromagnetic and water injection tests) failed to map the complex geo-structural karst zones clearly, resulting in considerable grout loss and excessive leakage during the grouting phase of this project. To deal with this limitation, a comprehensive approach, including a new drilling process monitoring system, borehole electrical resistivity tomography, borehole sonic logging, and water injection tests, is employed to identify the general characterization, geometry, and spatial distribution of karst zones along the anti-seepage curtain. Additionally, a deep belief network (DBN) model replaced the empirical relationships typically used to predict the grouting quantity for groutability evaluation in karstified areas. The DBN algorithm is trained by data collected using this comprehensive approach (rate of penetration, rock permeability, resistivity, and P-wave velocities) and two previous grouting quantities as input data. The lessons learned in this case study permit us to define an effective comprehensive approach for delineating the general characterization of karst zones between two boreholes and locations of potential conduits for grout flow through the borehole. The proposed DBN model can predict the grouting quantity for karst regions, and the accuracy of prediction is greatly affected by previous grouting quantity rather than the collected parameters.

Can we infer the age of karst conduit from the profile of potentiometric surface?

The Floridan aquifer consists of a high presence of karst features that make the landscape prone to sinkholes. Karst conduits can conduct high amounts of water and affect processes such as groundwater transport. A karst conduit evolution model based on dissolution chemistry is applied to the Silver Springs springshed in Ocala, Florida. The model is able to reproduce the observed potentiometric head profiles more accurately than the one-dimensional groundwater flow model for confined aquifer with leaky conditions. In addition, based on the initial fracture geometry and dissolution chemistry, the model predicts the age of the conduits from the analyzed head profiles to be approximately 9–60 Myrs old. The understanding of the karst conduit geometric evolution and mapping can improve conduit age prediction as well as better characterize conduit flow patterns and subsequent groundwater processes.

Filling the Void: The Effect of Stream Bank Soil Pipes on Transient Hyporheic Exchange During a Peak Flow Event

AbstractThe hyporheic zone is the ecotone between stream and river channel flow and groundwater that can process nutrients and improve water quality. Transient hyporheic zones occur in the riparian zone (bank storage or “lung model” exchange) during channel stage fluctuations. Recent studies show that soil pipes are widespread in stream banks and beneath floodplains, creating highly preferential flow between channel and riparian groundwater such that the traditional Darcy model of flow does not apply. We used MODFLOW with the conduit flow package to model a series of stream bank soil pipes and examined soil pipe density (number per m), length, diameter, height above baseflow water surface, connectivity, and matrix hydraulic conductivity on transient particle flow paths and total hyporheic exchange volume (i.e., bank storage) over the course of a peak flow (e.g., storm) event. We found that adding five soil pipes per meter more than doubled hyporheic volume. Soil pipe length was the most important control; adding one 1.5‐m‐long soil pipe caused a 73.4% increase in hyporheic volume. The effect of increasing soil pipe diameter on hyporheic volume leveled off at ~1 cm, as flow limitation switched from pipe flow to pipe‐matrix exchange. To validate our approach, we used the model to successfully reproduce trends from field studies. Our results highlight the need to consider soil pipes when modeling, monitoring, or managing bank storage, floodplain connectivity, or hyporheic exchange.

Characteristics of bleaching around major structures in a reservoir-cap rock system, SE Utah, USA

Bleached rocks are commonly formed from CO2-saturated water leakage to the surface. This provides an opportunity to understand the controlling factors of fluid flow in the subsurface. This study examined the relationships between bleaching patterns and geologic features or elements. We analyzed bleaching characteristics of multiple-layered sedimentary rocks around two major faults (Moab and Salt Wash faults) and fold axes (Green river anticline system) based on field observations and quantitative measurements (scanline survey and permeability) in the exhumed reservoir-cap rock systems in SE Utah, USA. The results showed that strongly bleached layers of sedimentary rock have a higher density of deformation bands compared with unbleached layers. This is consistent with the general property of deformation bands that frequently develop in layers with higher porosity and permeability. Although almost all fault zones act as conduits for fluid flow, some fault zones filled with clay-rich gouges could impede fluid flow. In addition, the internal sealing characteristics of the layer boundaries such as bedding planes could be important factors as they can act either as a pathway or a barrier for lateral fluid flow depending on the existence of filling materials such as calcite or kerogen. Our research may be useful for assessing fluid leakage in oil reservoirs or CO2 sequestration sites located in a reservoir-cap rock system of sedimentary basins.

Hydrogeologic Characterization and Mining Impact Analysis of a Low-Yield, Fractured Granite

A hydrogeologic characterization and impact analysis was performed for a proposed quarry at the Hitch Rack Ranch located in the Little Turkey Creek watershed southwest of Colorado Springs, Colorado. Continuous multiple channel tubing, nested piezometers, stream flow measurements, and mapping of known seeps were used to define the three-dimensional potentiometric distribution and areas of groundwater recharge and discharge. Water balance considerations, mass balance calculations, and potentiometric response to earth tides and barometric fluctuations confirmed that the granite fracture system in the ridge area of the proposed quarry has an extremely low bulk hydraulic conductivity resulting in minimal groundwater discharge to sustain the baseflow of Little Turkey Creek. The Little Turkey Creek valley forms the major conduit for groundwater flow exiting from the upper part of watershed underlain by granite. This conclusion has significant implications with respect to mine planning to minimize projected impacts to the hydrologic system and preserve this recharge component to downgradient Denver Basin sedimentary deposits.

Solitary waves in power-law deformable conduits with laminar or turbulent fluid flow

Fluid flow through pipe-like conduits embedded in viscously deformable material occurs in many natural systems, including magma transport in the Earth’s mantle and channelized water flow beneath glaciers. Here, we present and explore a model of fluid flow in viscously deformable conduits that unifies previously published models of magmatic and glacial systems. Previous results for magmatic systems have demonstrated the existence of solitary wave solutions for the case of laminar flow in Newtonian conduits. Here we extend these models to allow turbulent fluid flow in power-law materials consistent with models used in subglacial hydrology. The generalized model encompasses both laminar and turbulent fluid flow, and the solid matrix may deform according to any power-law rheology. A quasilinear approximation of the governing equations is introduced, along with an initial condition that develops into a perfect step shock. This initial condition is used in numerical solution of the full nonlinear system where a dispersive wave train forms at shock time. We show that solitary wave solutions exist for all parameters. Rheology-dependent flattening of the wave peaks is investigated. In the limit of a perfectly plastic matrix, the solitary waves approach square waves asymptotically. Motivated by subglacial hydrology models, we study the effect of discharge-dependent melting on evolution of the solitary waves. We find that melting focuses at the wave peaks, causing the waves to grow and accelerate over time.

Master Recession Curve (MRC) analysis to characterize karst aquifers of several springs in the north side of the Karangbolong (Gombong) karst area

Karst aquifers have triple porosity (diffuse, fissure, and conduit) which makes their characterization difficult, and often requires a combination of particular methods and investigation over a long period. The purpose of this study is to analyse the components of the flood hydrograph and create a master recession curve (MRC) in karst aquifers that recharge several springs on the north side of the Karangbolong Karst Area (Gombong). The springs studied include Kalisirah, Jumbleng, and Kalikarak springs. The data used are time-series discharges recorded every 15 minutes from November 2018 to March 2020. Furthermore, the reconstruction of the flow regime for MRC is carried out with the help of RC 4.0 software, which is at the same time able to define the level of karst aquifer development. The results showed that Kalisirah and Kalikarak Springs have a complex discharge regime with a degree of karstification in class 8, while Jumbleng Springs in class 5. Analysis of the components of the flood hydrograph reinforces the results of the calculation of the karstification degree. The time to the peak (Tlag) of the Kalisirah and Kalikarak Springs is relatively fast (1.94 and 1.44 hours), which indicates that conduit flow has developed, while Jumbleng spring has a longer Tlagof 2.69 hours. Calculation of time to base flow (Tb) both manually (by flood events analysis) and automatically (by MRC) shows that Kalikarak Springs has the longest time with an average of about 31 hours which reflects that karst aquifers which contribute to it are still quite good in storing groundwater, while Jumbleng spring has the fastest Tbvalue with an average of 17.25 hours which reflects the shortest release of water storage compared to the other two springs.

Chezy’s resistance coefficient in a horseshoe-shaped tunnel

The calculation of Chezy’s resistance coefficient (CRC) is typically not provided a priori in a design problem, and its value is often selected subjectively from the literature in most open channels and conduits for the uniform flow. The evaluation of this coefficient is crucial to channel design and for computing its normal depth. The primary purpose of this research study is to revisit the mathematical formulation for the resistance coefficient. A general explicit relation of the resistance coefficient in turbulent flow is set with different geometric profiles of conduits and channels, mainly the horseshoe-shaped tunnel using the rough model method (RMM). CRC is firmly based on the internal walls' absolute roughness of the channel, the liquid kinematic viscosity, the longitudinal slope, the discharge and the filling rate. Additionally, a simplified method is proposed to determine CRC with a restricted number of variables such as the kinematic viscosity, the absolute roughness, the slope of the conduit, and the discharge. Based on studying the variation of CRC as a function of the filling rate, another explicit expression is provided to compute this coefficient efficiently when its maximum value is reached. To demonstrate how Chezy’s resistance coefficient can be calculated in a horseshoe-shaped tunnel, some examples of calculations are proposed.

Surgeries of the lacrimal drainage system – A review

Nasolacrimal system serves as a conduit for tear flow from eye to the nasal cavity. Periodic blinking initiates a pump mechanism, helping in the even distribution of tears over the ocular surface, which then flows into the lacrimal sac and finally to the nasal cavity via the nasolacrimal duct (NLD). Obstruction in this system leads to inadequate tear drainage, which clinically presents as epiphora. Lacrimal outflow system disorders are very annoying to the patients, and sometimes vision threatening. Surgery is a definitive solution for most outflow obstructions, and patients should be counseled accordingly. Chronic use of topical medications for NLD problems is neither cost-effective nor efficacious, but only prolongs agony. This article aims to provide a comprehensive insight into the commonly performed lacrimal drainage surgeries. Literature search using PubMed, Cochrane, and Google Scholar with a combination of various words appropriate to this article was done and relevant articles were reviewed.