Hydraulic Considerations Research Articles

Future Scenarios of Design Rainfall Due to Upcoming Climate Changes in NSW, Australia

The occurrence of rainfall is significantly affected by climate change around the world. While in some places this is likely to result in increases in rainfall, both winter and summer rainfall in most parts of New South Wales (NSW), Australia are projected to decrease considerably due to climate change. This has the potential to impact on a range of hydraulic and hydrologic design considerations for water engineers, such as the design and construction of stormwater management systems. These systems are currently planned based on past extreme rain event data, and changes in extreme rainfall amounts due to climate change could lead to systems being seriously undersized (if extreme precipitation events become more common and/or higher in magnitude) or oversized (if extreme rainfall events become less frequent or decrease in magnitude). Both outcomes would have potentially serious consequences. Consequently, safe, efficient, and cost-effective urban drainage system design requires the consideration of impacts arising from climate change on the approximation of design rainfall. This study examines the impacts of climate change on the probability of occurrence of daily extreme rainfall in New South Wales (NSW), Australia. The analysis was performed for 29 selected meteorological stations located across NSW. Future design rainfall in this research was determined from the projected rainfall for different time periods (2020 to 2039, 2040 to 2059, 2060 to 2079, and 2080 to 2099). The results of this study show that design rainfall for the standard return periods was, in most cases, lower than that derived employing the design rainfall obtained from the Australian Bureau of Meteorology (BoM). While most of the analysed meteorological stations showed significantly different outcomes using the climate change scenario data, this varied considerably between stations and different time periods. This suggests that more work needs to be performed at the local scale to incorporate climate change predicted rainfall data into future stormwater system designs to ensure the best outcomes.

Analytical Solution for Optimum Design of Nozzle Discharge Lines Based on Hydraulic Considerations

This study focuses on finding the best design of nozzles used in the water discharge pipelines delivering free jets based on hydraulic considerations. An analytical solution is carried out to determine the best design for these nozzles. The solution depends on the derivative method applied to the energy head concerning the nozzle diameter to maximize the power of the jet. The equation derived for computing the best pipe-nozzle diameter ratio D/d in discharge lines applies over practical ranges of relative distance L/D (50-500) and relative roughness e/D (0.01-0.05). An illustrative example is solved and gives D/d = 1.8858 (closely equal to 1.9), the deviation is 0.77%, which is firmly accepted. The equation holds good for D/d from 1.4 to 3.584 and could be applied to compute D/d ratios without the need for a computer program. In the derived equation, D/d is a function of relative distance L/D, and friction factor F with negligible computational errors. The derived equation when compared with the conventional one, shows an increase in the computed power of the jet ranging from 12.5 to 19.23%. The evaluation study reflects the rigidity of the derived equations and their reliability in computing the best pipe-nozzle diameter ratios in discharge lines delivering free jets with reasonable powers, while the conventional formula is approximate. However, many engineering applications of water jet nozzles are used in; impulsive turbines, power-delivering free jets, water filters, flotation tanks, sedimentation tanks, water storage tanks, trickling filters, and other water and wastewater systems.

Experimental and numerical investigation on the hydraulic design criteria for a step-pool nature-like fishway

Hydraulic considerations specific for the design of step-pool nature-like fishways (NLFs) are limited to the body dimensions of the target species. Additional hydraulic criteria for flow depth, maximum values for each of pool depth, velocity, and turbulent kinetic energy in terms of the weir opening width and discharge can help design an optimum step-pool NLF. The present study developed design charts and rating curves based on numerical modeling using the computational fluid dynamics software FLOW-3D® HYDRO. Instantaneous velocity measurements on a 1:4 scaled physical model of a step-pool nature-like fishway designed as per the available design guidelines have been used to validate the numerical model. The hydrodynamics of the fishway with respect to the weir opening ratio b r (0.10, 0.25, 0.45, 0.65, and 1.00) and discharge Q (0.1–1.5 m3/s) was analyzed through numerical simulations on a prototype scale. The simulation results showed that the maximum flow velocity and the averaged velocity over the crest at b r = 0.10 and 0.25 are considerably lower than at b r > 0.25. The maximum turbulent kinetic energy and energy dissipation factors for the tested range of discharges were within recommended limits for b r = 0.10 and 0.25. The present study outcome in terms of the design charts and rating curves that illustrate the relationship between different variables can be used for an optimum design and ease in field implementation. In addition, the bed structure of the step-pool NLF presented in this study can be used to recreate full-scale or pilot models.

Multi-Criteria Assessment of Bridge Sites for Conducting PSTD/ISTD: Case Histories

The Federal Highway Administration (FHWA) has recently developed the Portable Scour Testing Device (PSTD) to improve scour analysis around bridge piers in cohesive soils as part of the NextScour project. The PSTD is a compact field erosion testing device that, apart from a drill rig and larger water pump, has a lot of similarity with the In-situ Scour Testing Device (ISTD) in mechanism and data acquisition. The purpose of this paper is to provide recommendations on the suitability of using PSTD and ISTD at sites that have cohesive subsurface soils. An overview of the capabilities and limitations of the PSTD/ISTD in relation to hydraulic considerations, soil types, depth coverages, and erodibility potential is given. A multi-criteria assessment methodology to evaluate site suitability for conducting PSTD/ISTD is presented. The assessment methodology was utilized to detect suitable sites among 30 Illinois bridge sites using soil layer information, boring locations, groundwater level readings, in-situ testing results, geospatial analysis, site accessibility, and aerial photos.

An Extra Tree Regression Model for Discharge Coefficient Prediction: Novel, Practical Applications in the Hydraulic Sector and Future Research Directions

Despite modern advances used to estimate the discharge coefficient ( C d ), it is still a major challenge for hydraulic engineers to accurately determine C d for side weirs. In this study, extra tree regression (ETR) was used to predict the C d of rectangular sharp-crested side weirs depending on hydraulic and geometrical parameters. The prediction capacity of the ETR model was validated with two predictive models, namely, extreme learning machine (ELM) and random forest (RF). The quantitative assessment revealed that the ETR model achieved the highest accuracy in the predictions compared to other applied models, and also, it exhibited excellent agreement between measured and predicted C d (correlation coefficient is 0.9603). Moreover, the ETR achieved 6.73% and 22.96% higher prediction accuracy in terms of root mean square error in comparison to ELM and RF, respectively. Furthermore, the performed sensitivity analysis shows that the geometrical parameter such as b/B has the most influence on C d . Overall, the proposed model (ETR) is found to be a suitable, practical, and qualified computer-aid technology for C d modeling that may contribute to enhance the basic knowledge of hydraulic considerations.

Hydraulic Fracturing Design Considerations and Optimal Usage of Water Resources for Middle Eastern Tight Gas Reservoirs.

Over the past few decades, hydraulic fracturing, a well-stimulation technique commonly used for extracting hydrocarbons within unconventional reservoirs, has played a significant role in transforming the energy industry. Multiple studies and field trials have proven that an effective, efficient, and economical approach is critical for such operations. However, even after numerous fracturing jobs conducted across the globe, they are still related with high risk. Moreover, the exploitation of such reservoirs is water- and resource-intensive as compared to conventional reservoirs. This is crucial, especially in offshore operations and arid regions. A comprehensive investigation through a traditional fracture design process was conducted for a candidate Middle Eastern reservoir. Through the construction of strategically constrained cases in the presence of complex natural fracture sets, this novel investigation allowed the model to successfully isolate and characterize the key fracture design parameters that influenced fracture geometry for the candidate field and in turn the requirements with respect to water usage and resource consumption. The results indicate that for the given field conditions, fluid and proppant optimization is critical to achieving maximum recovery. The influence of natural fracture is highly critical and greatly influences the overall productivity. Simulations further indicate water requirements for the candidate field ranging from 3.5 to 5.8 million gallons of water per operation, which is significant in water-scarce regions. The findings of this study and the proposed workflow can assist to better understand the distinct contributions of key fracture design and operational parameters that are critical under the current volatile market conditions.

Coupled whole-tree optimality and xylem hydraulics explain dynamic biomass partitioning.

Trees partition biomass in response to resource limitation and physiological activity. It is presumed that these strategies evolved to optimize some measure of fitness. If the optimization criterion can be specified, then allometry can be modeled from first principles without prescribed parameterization. We present the Tree Hydraulics and Optimal Resource Partitioning (THORP) model, which optimizes allometry by estimating allocation fractions to organs as proportional to their ratio of marginal gain to marginal cost, where gain is net canopy photosynthesis rate, and costs are senescence rates. Root total biomass and profile shape are predicted simultaneously by a unified optimization. Optimal partitioning is solved by a numerically efficient analytical solution. THORP's predictions agree with reported tree biomass partitioning in response to size, water limitations, elevated CO2 and pruning. Roots were sensitive to soil moisture profiles and grew down to the groundwater table when present. Groundwater buffered against water stress regardless of meteorology, stabilizing allometry and root profiles as deep asc.30m. Much of plant allometry can be explained by hydraulic considerations. However, nutrient limitations cannot be fully ignored. Rooting mass and profiles were synchronized with hydrological conditions and groundwater even at considerable depths, illustrating that the below ground shapes whole-tree allometry.

Urbanization and stream ecosystems: the role of flow hydraulics towards an improved understanding in addressing urban stream degradation

Catchment urbanization is widely recognised as a primary driver of stream degradation by increasing stormwater runoff, which causes major changes to key ecosystem processes. Reinstating the “natural” hydrogeomorphic conditions is central in designing successful, self-sustaining restoration actions; however, addressing urban stream degradation by re-establishing the hydrogeomorphic conditions remains a challenge, and comparatively limited measurable progress has been observed, particularly in achieving ecological objectives. This review articulates that stream restoration goals might be better achieved when management measures take a broader approach that considers anticipated hydraulic condition effects that liaise relationships between flow and ecology. The study argues that fluvial systems are characterised by complex and dynamic ecosystem processes primarily governed by the hydraulic conditions (e.g., velocity, depth, shear stress); thus, as the practice of addressing urban stream restoration becomes increasingly common, it is critical to explore and understand the anticipated response of the hydraulic conditions. It describes how hydraulic regime consideration provides further opportunity for a holistic approach to urban stream management given their capacity to account for multiple ecological and geomorphic objectives. This review suggests that developing suitable flow–biota–ecosystem processes nexus is critical to addressing urban stream degradation, and hydraulic consideration in restoration actions provides an important step towards that. It discusses opportunities to evolve management actions to achieve restoration goals by highlighting how the management of the two key levers (addressing altered flow regime and morphology) to improve the hydraulic conditions can help to address the urban stream disturbance.

The SUBGLACIOR drilling probe: hydraulic considerations

AbstractUsing significant technological breakthroughs and unconventional approaches, the goal of the in situ probing of glacier ice for a better understanding of the orbital response of climate (SUBGLACIOR) project is to advance ice core research by inventing, constructing and testing an in situ probe to evaluate if a target site is suitable for recovering ice as old as 1.5 million years. Embedding a laser spectrometer, the probe is intended to make its own way down into the ice and to measure, in real time and down to the bedrock, the depth profiles of the ice δD water isotopes as well as the trapped CH4 gas concentration and dust concentration. The probe descent is achieved through electromechanical drilling combined with continuous meltwater sample production using a central melting finger in the drill head. A key aspect of the project lies in the design and implementation of an efficient method to continuously transfer to the surface the ice chips being produced by the drill head and from the refreezed water expulsed downstream from the melting finger, into the borehole. This paper presents a detailed calculation and analysis of the flow rates and pressure conditions required to overcome friction losses of the drilling fluid and to effectively transport ice chips to the surface.

A Novel Two-Stage Design Framework for Two-Dimensional Spatial Packing of Interconnected Components

AbstractPacking and routing separately are each challenging NP-hard problems. Therefore, solving the coupled packing and routing problem simultaneously will require disruptive methods to better address pressing-related challenges, such as system volume reduction, interconnect length reduction, ensuring non-intersection, and physics (thermal, hydraulic, or electromagnetic) considerations. Here we present a novel two-stage sequential design framework to perform simultaneous physics-based packing and routing optimization. Stage 1 generates interference-free initial layouts that are fed to stage 2 as starting points to perform continuous physics-based optimization. Three distinct strategies for stage 1 have been introduced recently, (1) the force-directed layout method (FDLM), (2) an extension of the shortest path algorithms (SPAs), and (3) a unique geometric topology (UGT) generation algorithm. In stage 2, a gradient-based topology optimization method is used to simultaneously optimize both component locations and interconnect routing paths. In addition to geometric considerations, this method supports optimization based on system behavior by including physics-based objectives and constraints. The proposed framework is demonstrated using three case studies. First, the layout generation methods developed for stage 1 are compared with respect to system performance metrics obtained from stage 2. Second, a multi-objective optimization problem using the epsilon-constraint method is solved to obtain Pareto optimal solutions. Third, an extension to multi-loop systems is demonstrated. In summary, the design automation framework integrates several elements together as a step toward a more comprehensive solution of 3D packing and routing problems with both geometric and physics considerations.

Compound Inundation Impacts of Coastal Climate Change: Sea-Level Rise, Groundwater Rise, and Coastal Precipitation

The importance of considering the compound effects of multiple hazards has increased in recent years due to their catastrophic impacts on human lives and property. Compound effects correspond to events with multiple concurrent or consecutive drivers, e.g., heavy storms, coastal flooding, high tides, and sea level rise (SLR). There is a recent evidence on inundation caused by SLR-driven groundwater rise, and there is a distinct knowledge gap in understanding the compound inundation effects of this phenomenon considering the important hydrologic and hydraulic considerations under compound events. To fill this knowledge gap, we developed a novel analytical framework to understand the movements of the surface flow under typical precipitation events considering their interaction with uprising groundwater and SLR in a coastal watershed located in Oakland Flatlands, CA, USA, home to several disadvantaged communities. This modelling approach simulates the dynamics of compound flooding in two dimensions of the earth surface in a fine resolution, which is critical for devising proper flood management strategies. The reason to focus on disadvantaged coastal communities is that such communities typically encounter disproportionate environmental injustices due to the lack of sufficient drainage capacity in their infrastructure. Our results show that by considering the compound effect of SLR, groundwater inundation and precipitation flooding, the drainage capacity of infrastructure will be substantially exceeded, such that over 700 acres of the built infrastructure could be flooded. This is a considerable increase compared to scenarios that do not consider compound effect, or scenarios that consider inappropriate combinations of driving factors. In sum, our results highlight the significance of considering compound effects in the coastal inundation analyses, with a particular emphasis on the role of groundwater rise.

Hydraulic fracturing design considerations, water management challenges and insights for Middle Eastern shale gas reservoirs

Water is one of the most important commodities in the world and plays an essential role in the hydrocarbon industry. With increased agricultural production, rapid industrialization, population growth and climate change, the world is facing an extreme water crisis in many regions. Coupled with a surge in energy demand and consumption, this has greatly influenced the hydrocarbon industry. With increasing stress on water resources, it is essential to examine how water is managed within the hydrocarbon industry and devise ways to utilize water more efficiently, especially within water scarce regions such as the Middle East.Augmented by the recent activities in the oil and gas industry, it can be seen that an economical and efficient hydraulic fracturing job has become crucial for the successful development of unconventional reservoirs. However, exploitation of unconventional reservoirs is heavily water-intensive as compared to conventional reservoirs. In this study, a comprehensive investigation that deals with quantification of changes with respect to the variation in prime contributors within a traditional fracture design process is presented.To understand the significance of key design parameters, factors that affect productivity within typical Middle Eastern shale gas reservoirs were analyzed through simple constrained cases. Investigations reveal that parameters such as fracture aperture, natural fracture distribution, fracturing fluid viscosity and Young’s modulus are crucial to the overall production and water requirement. Furthermore, an outline for resource management within a traditional fracture design process is presented along with potential challenges for the region. Enhancing existing methodologies and incorporating key parameters highlighted within this study can contribute to the overall value chain. In addition to ultimately assisting in the verification of modern best practices, this investigative approach will create a paradigm for future studies for the region to assist in a simplistic prediction of fracture propagation and associated response to augment water usage.

Flood risk assessment and management in urban areas: a case study in Bechar City, South Western Algeria

Flood has always been considered as one of the natural catastrophes that accompanies with huge losses and damages, which affect the lives of human beings. The present paper presents a flood risk assessment approach for Bechar city, an urban area in Southwest of Algeria using hydrologic engineering centres-river analysis system (HEC-RAS). In order to achieve better floodplain management in the study area, a suite of solutions were developed, taking into account hydraulic, infrastructure, environmental, geomorphic, economic and social considerations. Some of the key solutions identified included: 1) redevelopment of the Bechar Wadi over the entire urbanised area, on a width of the bed of the Wadi whose sizing will be ensured by a detailed study; 2) evacuation of excess flow through a bypass channel to Tigheline Wadi; 3) establishment of a dam in downstream of El Abiad Wadi. The results of this study will be of great help to the decision makers in the field of floodplain management, especially the involved government's department, to make a proper plan for future development.

Evaluating the hydraulic capacity of existing drain systems and the management challenges of stormwater in Addis Ababa, Ethiopia

Study regionAddis Ababa, Ethiopia. Study focusAddis Ababa is undergoing rapid urbanization with unprecedented high rate of road and building constructions, resulting in a sudden upsurge of sealed surfaces and generation of significant amounts of stormwater. The present study therefore aims to investigate the hydraulic capacity of existing drains and stormwater management challenges using detailed field surveys, and stakeholders' interview. 469 road segments (74 km) and 202 drain segments (42.76 km) in two representative case sites confined in 564.54 ha boundary areas were physically surveyed. New hydrological insights for the regionResults showed that 14% of the drains in new city parts and 28% in old city parts were in conditions inadequate for removal of stormwater, resulting in flash flooding and infrastructure degradation in the associated watersheds. Further, although more than 72% of the surveyed drains were oversized, stormwater overtopping reoccur as a season-to-season problem, ascribed to illegal dumping of waste into drains, reducing their hydraulic capacity. The challenges of stormwater management were related to lack of city-wide drainage master plan, absence of hydrologic data considerations during designing drains, and weak enforcement on solid and liquid waste dumping into drains. The present study recommends that building practices that minimize surface sealing and critical hydrologic and hydraulic considerations during designing drains, and educating the local community and stakeholders regarding waste management.

Hydraulic consideration to improve the tractive force of sewage in sewer pipes using a storage tank

Hydraulic consideration to improve the tractive force of sewage in sewer pipes using a storage tank

Thermal hydraulic considerations of nuclear reactor systems: Past, present and future challenges

Thermal hydraulic analysis of nuclear reactor core and its associated systems can be performed using analysis system, subchannel or computational fluid dynamics (CFD) codes to estimate the different thermal hydraulic safety margins. The safety margins and operating power limits under different conditions of the primary as well as secondary cooling system such as the system pressure, coolant inlet temperature, coolant flow rate, and thermal power and its distributions are considered as key parameters for thermal hydraulic analysis. Considering the complexity of rod bundle geometry, boiling heat transfer and different turbulent scales bring about the many challenges in performing the thermal hydraulic analysis to ensure the safe design and operation of nuclear reactor systems under normal and abnormal conditions. A comprehensive review is presented of past, present and future challenges in state-of-the-art thermal hydraulic analysis c overing various aspects of experimental, analytical and computational approaches.

Flood risk assessment and management in urban areas: a case study in Bechar City, Southwestern Algeria

Flood has always been considered as one of the natural catastrophes that accompanies with huge losses and damages, which affect the lives of human beings. The present paper presents a flood risk assessment approach for Bechar city, an urban area in Southwest of Algeria using hydrologic engineering centres-river analysis system (HEC-RAS). In order to achieve better floodplain management in the study area, a suite of solutions were developed, taking into account hydraulic, infrastructure, environmental, geomorphic, economic and social considerations. Some of the key solutions identified included: 1) redevelopment of the Bechar Wadi over the entire urbanised area, on a width of the bed of the Wadi whose sizing will be ensured by a detailed study; 2) evacuation of excess flow through a bypass channel to Tigheline Wadi; 3) establishment of a dam in downstream of El Abiad Wadi. The results of this study will be of great help to the decision makers in the field of floodplain management, especially the involved government's department, to make a proper plan for future development.

Structural reliability of elevated water reservoirs under wind loading

In the field of civil engineering, concrete water storage tanks are considered as hydraulic structures occupying a special place among other structures. The location of these tanks is based on hydraulic considerations related to the desired service pressure for subscribers whose solution is obtained by a compromise with the topographical constraints. In southern Algeria and the highlands; in order to ensure adequate pressure in the drinking water supply networks, the tanks are then elevated to high heights, which puts them under significant stress during windstorms and sandstorms conditions that are frequent in the South Algerian. As the severe weather conditions due to high winds are common, the elevated water storage tanks are designed to withstand to winds speeds included between 25 and 31 m/s according to the Algerian Wind Code. Given the uncertain and randomness of this phenomenon, the classical deterministic calculations of the engineer become limited since they do not integrate the notion of failure probability of the structure. In this study, a probabilistic approach based on Monte Carlo simulations is used to analyze the reliability of elevated water tanks submitted to hazard storm of wind loading. The limit state functions are related to the ultimate and serviceability limit states of the concrete elevated tank under wind analysis. This reliability approach, takes into account mainly two parameters which are the wind speed and the concrete compressive strength considered as random variable. Fragility curves depending on wind zones are obtained, where they demonstrate the dominant failure modes that can cause the structural failure.

Hydraulic fracturing considerations: Insights from analogue models, and its viability in Colombia

Fracking is being considered around the world as a potential method in the hydrocarbons extraction given the increase of production in USA and Canada during the last years with its implementation. The most criticized feature of the technique of fracking is the contamination of underground waters by fluids connected through the generated and/or pre-existing fractures. This work evaluates the viability of fracking in Colombian territory based in the study of the analogue models, considering the elastic properties of the reservoir rocks using gelatin, sand and clay that apply scaled pressure (lithostatic pressure to scale). The gelatin is used to simulate the reservoir zone, the clay will simulate one sail and the sand will simulate reservoir rocks of underground water. As a result seven different models were generated. There were simulated as 1) the anisotropy presence, 2) the rock sail presence, and 3) the injection groove of fluids in the pipeline. The completed models show that the required distance between the unconventional reservoir and underground waters to avoid contamination by fluids is ~200 m, also between the hydraulic fracturing point and the faults that connect with the shallows area is ~350 m, and it is suggested to study in detail the permeability of both: nearby faults and the rock sail. Two Colombian basins (Magdalena Midland Valley and Llanos) were taken as the main base to analyze the assessment of fracking according to the previously mentioned results, concluding that it is viable particularly in areas like Llanos Basin and with some precautions in similar zones to Magdalena Midland Valley Basin.

Observation-based CHF model development: Dry spot – Dry patch models

Abstract Recently advanced visualization techniques such as total reflection and IR methods have been applied to observe thermally and hydraulically the CHF mechanism at the surface as well as macroscopic bubble dynamics simultaneously. Based on observation Ha and No (1998a,b, 2000), and Choi et al. (2016) developed a Dry spot model and a Dry patch model, which is an extension version of the dry spot model. Experimental observations clearly showed that the production of unquenchable dry patches mainly contributes to the initiation of CHF. Based on the above observatory conclusions and extensive literature survey, we discussed the physical basis of the Dry Spot/Dry Patch model. In the dry spot model, we assume that the dry spot can become unquenchable one when it is surrounded by 5 neighboring dry spots based on the geometrical consideration, which was confirmed by validation process. In the dry patch model, both criteria from the hydraulic and thermal considerations were proposed to estimate the critical size of unquenchable dry patch at CHF. The wall dry area fraction can be calculated by applying a probabilistic concept for the creation of the unquenchable dry patch. We showed that the Dry Spot/Dry Patch model can be extended into CHF predictions in both pool boiling and forced convective boiling. For transition boiling, we proposed models to represent two suppression mechanisms deactivating potential nucleation sites: nucleation site deactivation and non-availability mechanism. For the physical model of the nucleation site deactivation mechanism we introduced the spatial randomness concept. For the non-availability mechanism we proposed the multi-stage calculation method which considers the sequential bubble activation and their interaction. Then, we showed that the dry spot model modified with the current transition model well predicted the whole boiling curve including CHF, nucleate boiling, transition boiling, and film boiling.