Initial Water Depth Research Articles

Influence of initial water depth of extended stepped tray on the productivity while working beyond sunshine hours

Increasing fresh water productivity with minimal environmental impact still remains an ardours milestone for researchers. Solar energy desalination is a widely accepted technology due to renewable energy availability in abundance and hassle free operation. Research studies were focussed on improving the distillate output modifying the operating and controllable parameters of passive stepped stills. In this paper the water depth in the trays is varied to ascertain its prominence on the productivity of the stepped still with extended trays. The effect of initial depth of water on nocturnal yield has been studied using the extended trays. The stepped still was operated beyond the sunshine hours into the night until the productivity ceases. Results indicate that, when nocturnal yield is accounted in the daily yield, the productivity improved as the depth of water increased. The stepped still with extended tray width of 120 mm produced a maximum daily yield of 5540 ml/m2/day.

A modelling approach to explore the optimum bubble size for micro-nanobubble aeration

Bubble aeration has been widely applied in water/wastewater treatment, however its low gas utilization rate results in high energy consumption. Application of micro-nanobubbles (MNB) has emerged as a process with the potential to significantly increase gas utilisation due to their high relative surface area and high gas-liquid mass transfer efficiency. In this study, we demonstrate through calibrated models that MNB of an optimum bubble size can shrink and burst at or below the water surface enabling (1) all encapsulated gas to thoroughly dissolve in water, and (2) the bursting of nanobubbles to potentially generate free radicals. Through the understanding of MNB dimensional characteristics and bubble behaviour in water, a dynamic model that integrated force balance (i.e. buoyancy force, gravity, drag force, Basset force and virtual mass force), and mass transfer was developed to describe the rising velocity and radius variation of MNB along its upward trajectory. Unlike for conventional millimetre-sized bubbles, intensive gas dissolution of MNBs led to radius reduction for small bubbles, while a large initial radius triggers bubble swelling. The initial water depth was also crucial, where greater depth could drive the potential for bubble shrinkage so that they were more liable to contract. For example, the optimum bubble size of air (42–194 μm) and oxygen (127–470 μm) MNB that could achieve complete gas transfer (100% gas utilisation) for a range of specific water depths (0.5–10 m) were calculated. The modelling results for microbubbles (10–530 μm) were well validated by the experimental data (R2>0.85). However, the validation of the modelling results for nanobubble (<1 μm) aeration requires further study due to a lack of available empirical data. In this study, the proposed model and analysis provided new insights into understanding bubble dynamics in water and offered fundamental guidance for practitioners looking to upgrade bubble aeration system.

Impact pressure of dam-break waves on a vertical wall with various downstream conditions by an explicit mesh-free method

This study employs an explicit mesh-free numerical scheme to simulate dam-break waves impacting on a rigid vertical wall. In the method, the pressure Poisson equation is solved explicitly by an established equation between the pressure and the known parameters. The numerical scheme is validated by simulating a dam-break wave impacting a solid wall and the simulated impact pressure at the monitoring points has a good agreement with the experimental measurements. After model validation, the numerical method is applied to simulate a dam-break wave impacting a solid wall after propagating various downstream wet beds with different water depths. The impact pressure on the wall is monitored and the pressure history during the dam-break wave propagation is analyzed and discussed. The impact pressure for different dam-break waves caused by different upstream water depths is then investigated. The impact pressure at the monitoring points is illustrated to show the pressure variations. In the simulations, the pressure field is observed to be smooth by using the explicit numerical scheme. It is also found that the downstream wet bed condition and the upstream initial water depth to trigger the dam-break wave play important roles in the maximum impact pressure on the rigid wall.

Numerical Study of Partial Dam–Break Flow with Arbitrary Dam Gate Location Using VOF Method

This paper aims to evaluate the crucial influence of the width of dam gate and its position, as well as initial water depth, on the evolution of rarefaction waves on reservoirs, and of shock waves over dry flood plain areas. The large eddy simulation (LES) model and volume of fluid (VOF) method are used to simulate three objectives. Firstly, validation of the presented numerical model, and of mesh sensitivity analysis, are conducted by means of a physical test case, taken from the literature, showing very good accuracy with a small value of RMSE among all hydraulic features in the case of fine mesh. In this direction, the 3D result is also compared with the published 2D one, to prove the necessity of using a 3D model in performing dam–break flow in an early stage. The second aim is to look for insight into the following 3D hydraulic characteristics of dam–break flow: water depth, velocity hydrograph and streamline, vorticity, the q–criterion incorporated with variety of breach size, initial water stage and the reservoir outlet’s location. The influence of the dam gate’s place on peak discharge is pointed out by means of a 3D model, while the existing analytical solution is not specified. With the same conditions of initial water depth, breach width and geometry, an analytical solution gives the same peak discharge, while a 3D numerical one indicates that a symmetrical dam gate provides a greater value than does the asymmetrical case, and also a value greater than that of an analytical result.

On the Inference of Tsunami Uncertainties From Landslide Run‐Out Observations

AbstractProbabilistic tsunami hazard analysis (PTHA) due to submarine landslides is much less developed than PTHA for earthquake sources. This is partly because of less constrained data available for quantifying source probability, and partly because of the lack of knowledge related to the tsunami generation process due to landslide dynamics. This study provides a basis for estimating the uncertainty related to landslide dynamics for PTHA from submarine landslides based on a new landslide database in the Gulf of Cadiz. The establishment of this new database is described herein. We use submarine landslide run‐out statistics from this database to calibrate landslide parameters and related uncertainties employing the cohesive landslide model BingClaw. In turn, coupling the landslide motion to tsunami genesis is performed in order to characterize the inferred tsunami uncertainties. Important parameters that can explain the large tsunami uncertainties are the initial water depth of the landslide, the slope, the landslide volume, and the initial yield strength of the landslide material. Kinematic properties such as the initial landslide acceleration or the Froude number are found to strongly correlate with the tsunami‐genesis. In this study, we show how matching numerical landslide models with observed run‐out from past events in the field can give information about the uncertainty in their tsunami‐genic strength. This can in turn be applied in future PTHA for spanning uncertainty ranges due to the landslide dynamics on tsunami‐genesis, constrained by landslide run‐out data.

Godunov-type solutions for free surface transient flow in pipeline incorporating unsteady friction

AbstractA finite-volume second-order Godunov-type scheme (GTS) combining the unsteady friction model (UFM) is introduced to simulate free surface flow in pipelines. The exact solution to the Riemann problem calculates the mass and momentum fluxes while considering the Brunone unsteady friction factor. One simple boundary treatment with double virtual cells is proposed to ensure the whole computation domain with second-order accuracy. Results of various transient free-surface flows achieved by the proposed models are compared with exact solution, experimental data, the four-point implicit Preissmann scheme solution, as well as predictions by the classic Method of Characteristics (MOC). Results show that the proposed second-order GTS UFMs are accurate, efficient, and stable even for Courant numbers less than one and sparse grid. The four-point implicit Preissmann scheme may produce severe numerical attenuation in the case of large time steps and unsuitable weighting factors, while the MOC scheme may produce severe numerical attenuation in the case of a low Courant number and could not maintain mass conservation. The numerical simulations considering the unsteady friction factor are closer to the measured water depth variations. The effect of unsteady friction becomes more important as the initial water depth difference increases significantly.

Deep ocean bubble transport model coupled with multiple hydrate behavior characteristics

AbstractSubmarine gas seepage is a widely observed process. In this study, a unified mechanistic model of bubble transport both inside and outside the gas hydrate stability zone (GHSZ) was developed. Multiple hydrate‐related behaviors were considered, including hydrate nucleation, hydrate film lateral spread, hydrate shell dynamic growth, hydrate dissolution and decomposition, and collapse and fracture deformation of hydrate‐coated bubbles. Using the proposed model, a series of simulation studies about bubble dissolution and rising fate were conducted. The results indicate that the formation of solid hydrates in the deep‐sea environment can provide a fairly effective barrier for the dissolution and shrinkage of bubbles, and the deeper the initial release water depth, the smaller the critical size of the bubble required for arriving at the water surface. Furthermore, the majority of gases released from the seafloor would be absorbed by the shallow oceanic layer, but larger bubbles could still pass through the water column to the atmosphere.

Experimental investigation on the wave-attenuating performance and shape optimization of water ballast type floating breakwater

Floating breakwaters (FB) play an important role in protecting the safety of marine structures, and Box-type FB is widely used due to its simple shape, among which, the ballast water type FB has good wave-attenuating performance. However, the research on the influence of the connection mode and the inner ballast water on the wave-attenuating performance is still insufficient. In this paper, firstly, two different connection modes (catenary type and tensely type) of water ballast Box-type FB is experimentally investigated, the results show that when compared with tensely type, the mooring force of catenary type is significantly reduced while maintaining similar wave-attenuating performance, indicating its suitability for engineering. Secondly, to further improve the wave-attenuating performance of catenary type, the shape of Box-type FB is optimized and a new type of I-shaped FB is proposed. After that, the wave-attenuating performance, motion response, inner ballast water movement, and maximum mooring force of catenary water ballast I-shaped FB are experimentally compared with that of catenary water ballast Box-type FB, and the better performance of the I-shaped FB is verified. Furthermore, the influences of initial ballast water depth and wing length are experimentally investigated. The results indicate that within the scope of this study, the catenary water ballast I-shaped FB present a superior wave-attenuating performance and simultaneously exhibit the smallest mooring force, when the lower edge of the upper wing is initially flush with the water surface and also the wing length equals 1.5 times of the wing thickness. This paper could provide references for the optimization of catenary water ballast floating breakwater.

Experimental and numerical study on the evolution of wave front profile of dam-break waves

This paper focuses on the evolution of wave front profile of dam-break waves. Firstly, dam-break waves with various initial upstream and downstream water depths are conducted experimentally and systematically. Secondly, the obvious influence of bottom resistance on wave front profile for dry-bed, also the accuracy of exiting analytical solution on the conserved wave height behind the wave front for wet-bed, are elaborately explicated and are carefully verified with experimental results. In addition, the evolution processes of wave front profile with initial downstream water depth and incoming wave height are revealed in detail. The relationship between the maximum incoming wave height and the conserved wave height behind the wave front, as well as the evolution of maximum wave front slope with the conserved wave height and the initial downstream water depth, are obtained experimentally. Also the corresponding envelopes are achieved. Furthermore, the discussions between dry-bed and wet-beds are highlighted, as well as the scale effect. Finally, the interaction mechanism between upstream incoming wave and initial downstream water is revealed. This study presents a deeper insight into the evolution of dam-break wave front profile, and provides a method for rapid calculation of maximum wave height and maximum wave front slope.

Physical and Numerical Investigations on Wave Run-Up and Dissipation under Breakwater with Fence Revetment

Revetment elements and protective facilities on a breakwater can effectively weaken the impact of waves. In order to resist storm surges, there is a plan to build a breakwater on the northern shore of Meizhou Bay in Putian City, China. To better design it, considering different environmental conditions, physical and numerical experiments were carried out to accurately study the effects of the breakwater and its auxiliary structures on wave propagation. In the experiments, the influence of the wave type, initial water depth, and the structure of the fence plate are considered. The wave run-up and dissipation, the wave overtopping volume, and the structure stability are analyzed. The results indicate that the breakwater can effectively resist the wave impact, reduce the wave run-up and overtopping, and protect the rear buildings. In addition, under the same still water depth and significant wave height, the amount of overtopped water under regular waves is larger than that under irregular waves. With the increase of the still water depth and significant wave height, the overtopped water increases, which means that when the storm surge occurs, damage on the breakwater under the high tide level is greater than that under the low tide level. Besides, the fence plate can effectively dissipate energy and reduce the overtopping volume by generating eddy current in the cavity. Considering the stability and the energy dissipation capacity of the fence plate, it is suggested that a gap ratio of 50% is reasonable.

Coupled SPH–FEM Modeling of Tsunami-Borne Large Debris Flow and Impact on Coastal Structures

Field surveys in recent tsunami events document the catastrophic effects of large waterborne debris on coastal infrastructure. Despite the availability of experimental studies, numerical studies investigating these effects are very limited due to the need to simulate different domains (fluid, solid), complex turbulent flows and multi-physics interactions. This study presents a coupled SPH–FEM modeling approach that simulates the fluid with particles, and the flume, the debris and the structure with mesh-based finite elements. The interaction between the fluid and solid bodies is captured via node-to-solid contacts, while the interaction of the debris with the flume and the structure is defined via a two-way segment-based contact. The modeling approach is validated using available large-scale experiments in the literature, in which a restrained shipping container is transported by a tsunami bore inland until it impacts a vertical column. Comparison of the experimental data with the two-dimensional numerical simulations reveals that the SPH–FEM models can predict (i) the non-linear transformation of the tsunami wave as it propagates towards the coast, (ii) the debris–fluid interaction and (iii) the impact on a coastal structure, with reasonable accuracy. Following the validation of the models, a limited investigation was conducted, which demonstrated the generation of significant debris pitching that led to a non-normal impact on the column with a reduced contact area and impact force. While the exact level of debris pitching is highly dependent on the tsunami characteristics and the initial water depth, it could potentially result in a non-linear force–velocity trend that has not been considered to date, highlighting the need for further investigation preferably with three-dimensional models.

Climate Uncertainty and Optimal Groundwater Augmentation

AbstractTwo approaches to augment irrigation water supply are managed aquifer recharge (MAR) and on‐farm reservoirs with tail‐water recovery (OFS‐TWR). We explore the joint use of MAR and OFS‐TWR to sustain groundwater and agricultural income with climate variability by farmer risk preference. We find that MAR use declines slightly with greater risk aversion and declines rapidly with MAR cost. The use of OFS‐TWR increases with risk aversion. The use of MAR increases income by a larger percentage for risk‐neutral than very risk‐averse producers. Across risk aversion degree, the use of MAR leads to a percentage increase in income that is double the percentage increase in the standard deviation of income (i.e., income risk). At a low cost of MAR, there is little difference in MAR use between a very risk‐averse and a risk‐neutral producer across scenarios of crop profit margin and the initial depth to water. Large differences in OFS‐TWR use between a very risk‐averse and a risk‐neutral producer occur when there are relatively high crop profit margin, low initial water depth, or a low discount rate.

ENVIRONMENTAL AND HYDRAULIC MONITORING USING CATIONIC DYES TO INVESTIGATE THE BARRIERS EFFECT ON KAOLIN DEPOSITION

Dyes are used in hydraulic fields such as hydraulic tracking to show the flow path, monitor flow lines within a ground dam, or track the spread of contaminated water within horizontal pipes and environmental fields as environmental indicators in titrations, such as titration of precipitate composition. Some environmental experiments dispense with the dye's use because it interferes with other compounds, such as interfering with the turbidity readings even if non-reactive dyes, but the present study transformed this problem into a positive phenomenon to benefits from the dye in both fields. The research methodology includes a laboratory analysis using different parameters such as discharge of suspension, the volume of dye, and the percentage of initial water depth at maximum water depth also theoretical analysis of the previous research methodology. The experimental results show that cationic dyes' absorption (methylene blue dye, MB and crystal violet, CV) is directly proportional to the percentage of kaolin deposition in the sedimentation tank areas. Finally, MB and CV dyes are used in both fields in one trial (such as tracking flow movement, monitoring the vortices formed using baffles, and inter between the amount of kaolin precipitated in each zone the sedimentation). However, MB is the best compare to CV.

Exploring Substrate Water Capture in Common Greenhouse Substrates through Preconditioning and Irrigation Pulsing Techniques

Particles in a substrate create a network of pore pathways for water to move through, with size and shape determining the efficacy of these channels. Reduced particle size diversity can lead to increased leachate, poor substrate hydration, and an inefficient irrigation practice. This research examined the hydration characteristics of three greenhouse substrate components at three preconditioned initial moisture contents using subirrigation under five different irrigation durations and three water depths (2 mm, 20 mm, and 35 mm). Sphagnum peatmoss, coconut coir, and aged pine bark were tested at 67%, 50%, and 33% initial moisture (by weight). The objectives were to determine the impact of varying irrigation event durations (5, 10, 20, 30, 60 min) over a 60-min period, and the further influence of water depth and initial moisture, on the water capture abilities of peat, coir, and pine bark. The number of irrigation events depended on the irrigation event time of that experimental unit divided by the total time of 60 min, varying from 12, 6, 3, 2, and 1 event. Hydration efficiency was influenced by initial moisture content (IMC), water depth, pulsing duration, and inherent substrate characteristics (hydrophobicity/hydrophilicity). Initial MC had the largest impact on peat, regardless of water level or irrigation duration. Lower IMCs increased the hydrophobic response of peat, further reducing the amount of water the substrate was able to absorb. Pine bark had a 5–10% decrease in initial hydration between 67%, 50%, and 33% IMC, while coir’s hydrophilic nature reduced any IMC affects. At 50% IMC or less, coir had the highest volumetric water content (VWC) across all substrates, pulsing durations, and water depths. Water depth was found to increase initial hydration and final hydration 6–8% across all substrates. These three materials had altered and varied water capture responses depending on the combination of treatments employed. This work demonstrated the effects of intensity and exposure on substrates and the need for more integrated research for improving water use efficiency on container crops.

Simulation of Hurricane Harvey flood event through coupled hydrologic‐hydraulic models: Challenges and next steps

AbstractUsing the 2017 Hurricane Harvey flood event as a test case, this study set up a series of sensitivity analyses to highlight three challenges associated with large‐scale flood inundation modeling, including (a) model parameterization, (b) errors in digital elevation models, and (c) effects of reservoir retention. Driven by radar‐based hourly rainfall data, a series of hydrologic‐hydraulic models including the VIC hydrologic model, RAPID routing model, and Flood2D‐GPU hydrodynamic model are set up over Harris County, Texas, to simulate flood inundation and hazards. The results demonstrate the importance of hydrologic parameters in improving flood modeling. For a large flood event such as Hurricane Harvey, the effect of the initial water depths is insignificant. The Manning's n values may increase the peak water depth by ~1%, the flood extents by 65km2, and the high danger zone by ~6%. On the contrary, the bathymetry correction factors may reduce the flood extent by ~1.4% and the high‐danger zone by ~4%. Reducing the reservoir storage capacity to 1% may increase the flood extent by ~4% and the high‐danger zone by ~17%. This study may provide supporting information to guide and prioritize the development of future high‐performance computing hydrodynamic large‐scale flood simulations.

Numerical investigation of the impact of a dam-break induced flood on a structure

The flood caused by a dam-break event generally contains a large amount of energy, and it can be destructive to the downstream buildings and structures. In the present study, the evolution of a dam-break flood and its impact pressure on a structure are considered by performing a numerical simulation. A laboratory experiment is first performed to validate the numerical model. Subsequently, simulations are performed to investigate the impact pressure of the dam-break flood on a solitary structure in the downstream region. The flow regime near the structure, temporal variations and distributions of the impact pressure on the structure, and effects of the initial reservoir water depth on the peak pressures are discussed. It is observed that the profiles of the water surface at the cross-section upstream and downstream of the structure are completely different. In addition, the surface velocity distributions are significantly different. The structure suffers a large instantaneous impact pressure when the flood water first contacts the structure, and the value of this pressure can reach 1.5–3.0 times that of the maximum pressure after the first impact. The instantaneous impact pressure is proportional to the initial reservoir water depth. The distribution of the peak pressure acting on the wall on the upstream side of the structure is nonlinear in both the horizontal and vertical directions.

On water waves generated by gravity driven granular collapse

Tsunami-like waves can arise from large-scale geological events such as the collapse of a mountain flank or a volcano into a lake or an ocean. We here mimic this situation at the laboratory scale. The landslide is modeled by the sudden release of a rectangular granular column, which impacts a still water layer and generates a wave. Through experiments varying both the column dimensions and the initial water depth, three regimes of nonlinear waves of different shapes are reported. The amplitude and width of the generated waves are governed by a local Froude number based on the velocity of the granular front at the water surface.

HYDRUS-2D simulations of nitrate nitrogen and potassium transport characteristics under fertilizer solution infiltration of furrow irrigation

Abstract Understanding the characteristics of soil solute transport is fundamental to the design and management of furrow irrigation systems. This study determined the soil hydraulic and solute transport parameters by inverse solution with HYDRUS-2D and then verified them. The experimental data were obtained from the infiltration of clay loam and sandy loam of different potassium nitrate (KNO3) concentrations under furrow irrigation. Then, the initial soil water content (θ0), KNO3 concentration, and water depth (h0) affecting the transport characteristics of nitrate nitrogen (NO3−-N) and potassium (K+) were analyzed. The results indicated that the soil hydraulic and solute transport parameters determined from the inversion solution with HYDRUS-2D were reliable. The soil saturated water content, saturated hydraulic conductivity, and empirical parameter n in the van Genuchten–Mualem model increase with the increase of KNO3 concentrations, whereas the empirical parameter a shows a decreasing tendency. The distribution range of NO3−-N increased with the increases of θ0 and the KNO3 concentration, which had barely any effect on the range of K+ distribution. The horizontal distribution range of NO3−-N and K+ increased with the increase of h0, but it had no obvious influence on the vertical range.

An Experimental Study of a Bottom-Hinged Wave Energy Converter with a Reflection Wall in Regular Waves—Focusing on Behavioral Characteristics

The hybrid system of wave energy converters (WECs) using coastal structures is an attractive issue in terms of a decrease in construction costs and an improvement of the ability to capture wave energy. Most studies on the utilization of reflected waves from structures, which is one of the hybrid systems, are limited to mathematical analysis based on linear theories. Therefore, this paper presents fundamental experimental results in the presence of a reflection wall simplified as a coastal structure behind a bottom-hinged flap-type WEC under unidirectional regular waves. The behavioral characteristics and the power generation efficiency ke of the flap were investigated, focusing on wave steepness, initial water depth, and distance from the reflection wall. The results show that the condition of the initial water depth being smaller than the flap height is more effective in terms of avoiding unstable rotating of the flap. The maximum ke appeared slightly far from the node position of the standing waves because the flap shape and the power take-off (PTO) damping induce the phase difference between the reciprocating behavior of the flap and the period of the standing wave. The results imply that the optimum position of a WEC is dependent on WEC shape, PTO damping, and installation water depth.

Productivity, exergy, exergoeconomic, and enviroeconomic assessment of hybrid solar distiller using direct salty water heating.

In this work, experimental work is presented on the performance of a hybrid solar distiller comprising solar still (SS) combined with parabolic trough solar collector (PTSC) using direct heating of salty water by the collector. In this technique, the salty water supplied to the SS is heated by passing it directly through the parabolic receiver without using heat transfer mediums that reduce the system efficiency. The study is carried out at different salty water depths inside the SS basin under hot climate conditions of Upper Egypt. The system performance is compared with a previous system using oil as a heat transfer medium between PTSC and still (indirect heating). The advantages of this technique are its ability to reduce initial salty water depth in the basin and avoid using the pumping system and heat exchanger compared to the direct heating. The performance of the proposed system is evaluated based on productivity, energy payback time (EPBT), exergy, enviroeconomic, and exergoeconomic methodologies. Findings illustrate that the present system rises the energy efficiency by about 12%, 27.5%, and 46% and the system exergy efficiency by about 14%, 30%, and 49% at salty water depth 15 mm, 10 mm, and 5 mm in the basin compared with the indirect heating system. Moreover, using this technique of salty water heating reduces the production cost of freshwater by about 71% compared with the direct heating system. The exergoeconomic and enviroeconomic parameters of the direct heating mechanism are more effective compared with those of the indirect heating mechanism.