High Water Flow Velocity Research Articles

Chemical improvement of soluble rocks: Foundation of Mosul Dam as case study

The dissolution of soluble rocks (gypsum/anhydrite) beneath the Mosul Dam by water seepage has been observed upon the initial impoundment; consequently, several sinkholes have been manifested in the vicinity of the dam site. Traditional grouting has been envisaged as a potential remedy; however this measure has not eradicated the problem. The main purpose of this study is to overcome the solubility of the gypsum/anhydrite rocks using chemical grouts. Rock samples were acquired from the Fatha Formation outcrop and problematic layers of brecciated gypsum situated at varying depths beneath the Mosul Dam. Two commercially available liquid polymers, polyurethane (PU) and a mixture of acrylic and cement (ARC) were used to investigate their sealing performance in halting of the solubility of the rocks (gypsum/anhydrite). To simulate the dissolution phenomenon under the influence of artificial hydraulic pressure of the dam and the water flow in its abutments, two distinct laboratory models were devised. The outcomes from the experimental study on both untreated and treated samples revealed that the acrylic-cement composite (ARC) and polyurethane (PU) are influential polymers in halting the solubility of the gypsum rock samples under both factors of water pressure and high-velocity water flow.

Swimming Performance Assessments of Fish Species of Greatest Conservation Need to Inform Future Stream Crossing Designs in Texas

Conventional structures associated with stream crossings such as bridges and culverts can lead to zones of high-velocity water flow that impede fish passage. Such obstacles are likely to harm native fish populations by impacting migrations critical to their life history strategies, causing habitat fragmentation and extirpation, thereby limiting population growth and distribution. Due to the high rates of human population growth and development occurring in Texas, this is an issue of particular concern for fish designated as species of greatest conservation need (SGCN). This project focused on four SGCN fishes native to the Edwards Plateau Ecoregion, namely the Guadalupe Bass, Guadalupe Roundnose Minnow, Guadalupe Darter, and Plateau Shiner, at both adult (all species) and juvenile (Guadalupe Bass only) life stages. Our primary aim was to aid in the design of future culverts associated with stream crossings (or the modification of existing culverts) so that the water velocities through these structures do not exceed the swimming capacities of our target SGCN fishes. To this end, we assessed their maximum sustained swimming speeds (Ucrit) under a typical range of Edwards Plateau stream temperatures (15, 22.5, and 30 °C) to be used in site-specific calculations of the maximum allowable culvert water velocities (Vf). A secondary objective was to collect physiological endpoints of relevance to the overall swimming performance including the maximum burst swimming speeds (Umax), metabolic rate measurements (i.e., standard metabolic rate (SMR), maximum metabolic rate (MMR), and aerobic scope (AS)), cost of transport (COT), and optimal swimming speed (Uopt). Temperature-related effects were observed that can be used to inform site-specific culvert designs. In general, the highest Ucrit values for the tested species were near, or possibly between, 22.5 and 30 °C, while Umax stayed relatively consistent among treatments.

HORA 3D: Personalized Flood Risk Visualization as an Interactive Web Service

AbstractWe propose an interactive web‐based application to inform the general public about personal flood risks. Flooding is the natural hazard affecting most people worldwide. Protection against flooding is not limited to mitigation measures, but also includes communicating its risks to affected individuals to raise awareness and preparedness for its adverse effects. Until now, this is mostly done with static and indiscriminate 2D maps of the water depth. These flood hazard maps can be difficult to interpret and the user has to derive a personal flood risk based on prior knowledge. In addition to the hazard, the flood risk has to consider the exposure of the own house and premises to high water depths and flow velocities as well as the vulnerability of particular parts. Our application is centered around an interactive personalized visualization to raise awareness of these risk factors for an object of interest. We carefully extract and show only the relevant information from large precomputed flood simulation and geospatial data to keep the visualization simple and comprehensible. To achieve this goal, we extend various existing approaches and combine them with new real‐time visualization and interaction techniques in 3D. A new view‐dependent focus+context design guides user attention and supports an intuitive interpretation of the visualization to perform predefined exploration tasks. HORA 3D enables users to individually inform themselves about their flood risks. We evaluated the user experience through a broad online survey with 87 participants of different levels of expertise, who rated the helpfulness of the application with 4.7 out of 5 on average.

Prevention of Water Seepage Impact on the Soluble Rocks Using Colloidal Silica

Water seepage flow can dissolve soluble minerals that exist in rock formations. With the development of the excavated area due to dissolution, the water seepage velocity (discharge) into the dissolved rock will also increase. Therefore, water seepage and dissolution propagation are two interrelated processes. Mosul Dam foundation has experienced these processes since its construction, resulting in karstification in the reservoir and foundation of the dam. The present seepage-dissolution measure to minimize this phenomenon relies on traditional cementitious grouts. However, this measure has not been able to address the issue effectively. Currently, there are a few studies on the chemical remediation of soluble rocks under the influence of high-velocity water flow and water pressure. Therefore, the first part of the current study focuses on the impact of high-velocity water flow and water pressure on the dissolution acceleration of gypsum/anhydrite rocks. In the second part, the waterproof capacity of silica colloidal and its impact on the solubility reduction of the rocks is evaluated. Two distinct laboratory models were designed to simulate rock dissolution in the dam abutments and under the dam. Two sets of experiments were conducted on untreated and silica-treated samples. The experiments were executed on the samples extracted from Fatha Formation outcrop and problematic layers of brecciated gypsum situated at varying depths of the Mosul Dam foundation. The obtained findings reveal that the colloidal silica grout markedly prevents the water seepage impact on the soluble rock and that it can be very useful as an alternative to cement-based grouts.

Nonlinear Differential Equations of Flow Motion Considering Resistance Forces

For a stationary potential 2D planar open high-velocity water flow of the ideal liquid, we propose a closed system of nonlinear equations considering the resistance forces to the flow from the channel bottom. Tangential stresses on jet interfaces are ignored. The resistance force components are expressed in terms of velocity components. In this case, the flow equations can be solved through the method of characteristics, and the surface forces are reduced to equivalent volumetric forces. The system of non-linear equations is solved in the velocity hodograph plane; further, the transition to the physical plane takes place. Since the value of the hydrodynamic pressure decreases downstream of the flow, the friction forces to the flow in the first approximation can be considered by using the integral laws of resistance. At that, the form of the equations of motion in the plane of the velocity hodograph does not change. This fact is proved in the article. An example of calculating the water flow is provided. The kinecity, ordinates, and velocities of the flow along its extreme line are calculated without considering resistance forces. Validation of the model in the real flow is performed. Acceptable accuracy relative to experimental data is obtained.

Supercritical Froude Number Flow through Ducts with Statistically Roughened Walls

High-speed fluid flows over roughened surfaces occur in many engineering applications; one important application involves high velocity water flows in pipelines with roughened interior walls where the wall roughness affects head loss estimates necessary for engineering design purposes. The present analysis provides an analytical solution of the fluid physics underlying the induced static pressure profile resulting from high Froude number supercritical velocity through duct with random wall roughness. The analytic solution of the hyperbolic governing small perturbation velocity potential equation subject to high Froude number flows brings forward characteristic wave solutions that determine the static pressure profile in a duct with random height wall roughness. While current engineering practice utilizes semi-empirical engineering equations employing test data to determine the friction factor, velocity and static pressure profiles and head loss for different roughness types in different sized ducts as a function of Reynolds number (as summarized in a later section of the paper), the present analysis provides a new analytical method to determine the fluid physics involved in the static pressure change induced by wall random roughness in ducts subject to high Froude number supercritical flows.

Erosion-Corrosion Behavior and Mechanism of TiAlN Coating Under Different Flow Conditions in Simulated Seawater

Erosion-corrosion behavior of high-speed steel (HSS) and titanium aluminum nitride (TiAlN) coating were investigated under different flow conditions in simulated seawater. On the front side (facing toward the direction of water flow), there was a negligible failure of the TiAlN coating, but clear marks of erosion-corrosion on the HSS. Notwithstanding, unexpected failure features were identified on the back side (back against the direction of water flow) on both specimens because the high-velocity water flow was localized at the edge and the center was high in turbulence. For the HSS, there was dominant corrosion in the center and dominant erosion at the edge. For the TiAlN/HSS coating, the dense and layered structure retards the propagation of surface cracks as the major failure into the bulk and instead promotes layer-by-layer spallation. Additionally, visible “flow marks” were observed on both specimens and can be explained by the flow-accelerated-corrosion.

Soil assessment and mitigation of flash flood erosion using Ipomoe Carnea in Gombe town, Gombe state, Nigeria

In many parts of the world floods occur more often and increase in size. In the tropics, it is partly or wholly caused by climatological factors, in-situ soil types (as soils with low infiltration rate are vulnerable to flooding); inadequate drainage network, topography and human factors. Gombe town is situated within an elevation of 628 m and 361 m above sea level (a.s.l). Topography is mainly mountainous, undulating and hilly with open plains and mean slope gradient of 5°, considered to be a high gradient for unprotected soils. This causes high surface runoff leading to excessive flooding and formation of gullies, cutting deep trenches that result in the destruction of residential houses and environmental disasters throughout Gombe town. The research work assessed gully erosion from high vulnerable sections in Gombe town affected by high fluvial floods. Field measurement was done using 50 m tape, GPS, satellite images and laboratory analysis. Laboratory analysis of soil particles sizes showed that mean particle sizes were 74.9 %, 14.1 % and 11.0 % for sand, silt and clay respectivly; the textural class for the entire study site was sandy clay. Porosity from the entire study area contains low volume of voids relative to the volume of solids. Bulk density was slightly high compared to the standards values. The soil chemical properties of the soil pH for the entire site mean (ESM) was 6.42. This indicates that the soils are slightly acidic which affect microbial activities on organic matter that enhance the binding of soils to resists erosivity of fluvial floods. People resorts to using vegetative cover of Ipomoe Carnea plant as mitigation measures to protect their vulnerable houses and farms from gully erosions because the stems interweaves and forms a thick cover that diffuses the high velocity water flow into laminar flow. The weaved stems traps, blocks and prevents the flood transported materials(soil, humus, gravels) in between the stems thereby prevents and slows soil erosion to the nearest minimum.

Development of an inline bidirectional micro crossflow turbine for hydropower harvesting from water supply pipelines

Reliable and continuous power supply to the data monitoring and transmitting devices of the water intelligent network (WIN) system of urban water supply pipelines is still a challenge due to the restricted underground space and complex water environment. In this study, a novel inline bidirectional vertical crossflow turbine (IBVCT) integrated with bell-mouth guide blocks was developed to generate hydropower by converting the excess potential energy of the water flow onsite for power supply to the WIN system in Hong Kong. Specifically, the configurations and geometries of the proposed IBVCT were designed for large-size pipelines, and four schemes of water blocks in IBVCT were investigated based on the computational fluid dynamics method to determine the optimal configuration. A hydraulic test rig in the laboratory and a field test system integrated with an electricity storage module were developed. The IBVCT, after numerical optimizations, was fabricated and tested to validate its overall performance of power generation, water head loss, and long-term operating stability. The results showed that the designed centrosymmetric bell-mouth guide blocks significantly contribute to the efficient conversion of water flow energy into mechanical energy by the turbine. The IBVCT prototype had the best efficiency of 2.6 % at the water flow velocity of 1.3 m/s, which was capable of providing stable and sufficient electric power with a daily electricity generation capacity of 470 Wh. Additionally, the water head loss was effectively restricted within 6.1 m at the high water flow velocity of 3 m/s. These technology metrics of the IBVCT exhibited superior overall performance and met the power requirements of the WIN system used in the main urban water pipelines.

The operational concept of Mini LNG Carrier: Preventing sedimentation on the seabed

Utilization Mini LNG Carrier is an alternative solution to support the supply chain for the distribution of liquefied natural gas (LNG) to gas power plants, especially in Eastern Indonesia. Mini LNG carriers must have adequate seakeeping and manoeuvrability in carrying out their missions. The biggest challenge faced when manoeuvring in shallow water where the rotation of the propeller can produce high-velocity water flows that cause sedimentation on the seabed. The distance between the tip of the propeller to the seabed greatly determines the level of ease of erosion and sedimentation that can occur. This study aims to provide an alternative ships’ operational concept by mapping the suitability between the depth of the water and the rpm of the propeller that does not cause sedimentation on the seabed. This concept determines the velocity of the water flow at which sedimentation begins to occur as the propeller rpm threshold. The final result is a depth division map where the propeller can be used at maximum rpm, the propeller is used with a limited rpm and the depth at which the propeller is not recommended to be used.

Non-Newtonian shear viscosity of confined water in forsterite nanoslits: insights from molecular dynamics simulations

ABSTRACT The confined water flow through forsterite nanoslits is vital to the security of CO2 geological sequestration in deep saline aquifers. Molecular dynamics simulations for confined water in the forsterite nanoslits are performed in this work. We investigate the effects of nanoslit height, hydraulic pressure drop, temperature and hydrostatic pressure on the water flow characteristics. Firstly, equilibrium molecular dynamics simulations are conducted to select a minimum nanoslit height for the subsequent non-equilibrium molecular dynamics (NEMD) simulations, to weaken the ultra-dominant nano-confinement effect on water flow. NEMD simulations reveal that the velocity profiles transfer from parabolic to plug-like shape with the increase in hydraulic pressure drop. The distance-dependent shear viscosity is determined by analyzing velocity profiles. The results indicate that the confined water gradually deviates from the Newtonian to non-Newtonian fluid, resulting from the more condensed water molecule layers introduced by the large hydraulic pressure drop. Additionally, we demonstrate that the water flow is enhanced with the temperature increasing. The enhancement in water flow is attributed to the shear viscosity reduction, resulting from the looser hydrogen-bonding network. Comparatively, the impact of variations in the hydrostatic pressure on the velocity profiles and shear viscosity is insignificant. This work provides atomistic insights into the non-Newtonian transport behaviour of high velocity water flow under nano-confinement or extreme environmental conditions.

Nanoscale insights into the anti-erosion performance of concrete: A molecular dynamics study

The erosion effect of high-velocity water flow would lead to the failure of concrete in hydraulic structures. This study aims to characterize the anti-erosion ability of concrete at the nanoscale and study the reinforced mechanisms of SCMs, epoxy, and GO for the erosion resistance of concrete. A series of erosion models of concrete including C-S-H, C-A-S-H, C-S-H/Epoxy, and C-S-H/GO models were constructed. The results show that under the erosion effect of high-velocity water flow, some Caw atoms and water molecules would escape from the C-S-H substrate which is consistent with experimental results. Besides the structure of C-S-H affects its anti-erosion capability: The C-S-H model with a high Ca/Si ratio has a poor anti-erosion performance. The erosion resistance of C-S-H is enhanced by SCMs, epoxy, and GO as the addition of SCMs could increase the stability of C-S-H structure while the application of epoxy and GO can reduce the erosion damage of C-S-H caused by high-velocity water flow. These findings in the present investigation provide bottom-up insights on the anti-erosion performance of concrete at the nanoscale and enhanced mechanism of SCMs, epoxy, and GO, which play an important role in the designing and the development of anti-erosion concrete materials.

Numerical study of the boiling heat transfer characteristics of bluff body quenching in cylindrical tube

The present study numerically investigates the characteristics of the forced immersion quenching widely used in material manufacturing processes. The numerical simulation considers the boiling heat transfer occurring at the surface of the hot cylindrical specimen heated at 870 °C during the quenching process with a 20 °C water jet. It also examines the influence of water jet velocity on the forced-immersion quenching process. Once the water flow initially impinges on the top side of the hot steel specimen, a large amount of vapor gets generated but disappears from all sides within a few seconds. The amount of vapor decreases with increased water jet velocity due to the high convective heat transfer, leading to vapor condensation. Moreover, a larger recirculation region appears at the sidewall with high water flow velocity because water vapor formed near the wall escapes. Therefore, the cooling performance of the specimen can primarily be attributed to the boiling and convective heat transfer that occurs within a few seconds. The heat flux and heat transfer coefficient increase with the inlet velocity. Moreover, the cooling rate and uniformity are enhanced owing to the increased boiling and convective heat transfer.

Numerical simulation to evaluate the effect of the stepped chute on abrasion erosion of a stilling basin type III

Hundreds of concrete cubic meters may be ruined due to the abrasion erosion in several strategic hydraulic structures. Such unfavorable action can cause serious dangers, impose high maintenance costs, and reduce these structures’ life span. The high-velocity water flow, which carries large amounts of sediments, is the main cause of this phenomenon. This study was directed to evaluate the possibility of minimizing the abrasion action by changing the hydraulic structure design criteria; a numerical simulation was conducted depending on the FLOW3D program. It aimed to evaluate the effect of using a stepped spillway chute on the applied water pressure and the flow velocity along the type III stilling basin. The numerical simulation results showed that using a stepped chute instead of the traditional smooth chute provided a better water pressure distribution and reduced the maximum applied pressure by approximately 28.8 to 68.2%. Moreover, it also reduced the flow velocity along the stilling basin. Thus, the stepped chute use can be considered a possible solution to reduce abrasion erosion hazards in hydraulic structures.

Gas-liquid two-phase flow patterns in the wake of a submerged nozzle under co-flow condition

The present study aims to reveal gas-liquid flow patterns as gas is injected into co-flowing water. An experimental work was conducted in a loop in which pure water was circulated. The gas-injection nozzle was submerged in the flowing water. Effects of the water flow velocity and gas flow rate were jointly considered. Two-phase flow patterns were visualized using the high-speed photography and then analyzed statistically. The evolution of the cavity-water interface and collapse of cavity were explained. The results show that a sequential arrangement of a long attached cavity and dispersed bubbles in the streamwise direction constitutes a unique flow pattern. The cavity length is dependent of the contest between the gas velocity and water flow velocity. A single-valley distribution of pinch-off frequency as the gas/water velocity ratio varies is insensitive to the water flow velocity. At high water flow velocities, collapse of cavity follows the pattern of wake vortices. Distinct coalescence is evidenced at high gas/water velocity ratio as a large gas pocket is separated from the attached cavity. It is ascribed to the retarded motion of the gas pocket and high inertia of the subsequently detached small bubble.

The Inclusion of Acidic and Stormwater Flows in Concrete Sewer Corrosion Mitigation Studies

Concrete sewer pipes can be deteriorated by sulfuric acid (H2SO4), which is created by the oxidation of hydrogen sulfide in the presence of certain bacteria inside the sewers. This process is called biocorrosion. In this paper, H2SO4 (i.e., chemical, non-biogenic) was used to study acid attack on concrete samples. The authors conducted experiments under different acid flows and concentrations, to account for the conditions prevailing in sewage networks exposed to flowing acidic waters. The effect of intermittent stormwater on the removal of protective layers was studied in addition to constant flow runs. Specimens’ erosion depth was measured with a Vernier micrometer. In addition, unconfined compression at an axial strain rate of 0.0016 mm/mm/min was used for the estimation of unconfined compressive strength and elastic modulus. Moreover, the formation of gypsum as a protective layer and its role in biocorrosion was discussed. From this study, it was concluded that although the utilization of constant flowrates of acidic waters represents an important indication of corrosion mechanism, intermittent sewage and water flows should be taken into account, corresponding to real conditions in sewage networks, and resulting into accelerated concrete corrosion. Stormwater in combined sewers could remove the protective gypsum layer, thus accelerating chemical corrosion; however, in the presence of biogenic H2SO4, the removal of gypsum by excess flows due to stormwater could have a positive effect on corrosion mitigation. Finally, for combined sewers, selected coatings should withstand the effect of stormwater and high-velocity water flow tests should be included in future studies.

Effects of Adapted N-Fertilisation Strategies on Nitrate Leaching and Yield Performance of Arable Crops in North-Western Germany

Groundwater pollution with nitrate is a big challenge for drinking water abstraction in regions with intensive agricultural land-use, specifically with high livestock densities on sandy soils in humid climates. Karst aquifers with high water flow velocities are extremely vulnerable to this problem. To cope with this situation, a field trial with an installation of ceramic suction cups under a randomised block design with a typical north-German cropping sequence of silage maize–winter wheat–winter barley was established in a karst water protection zone. Over three years, reduced nitrogen (N) application rates and N type (mineral or combined organic + mineral fertilisation) were tested for their effects on crop yields and leachate water quality below the root zone. Results showed no significant reductions in crop yields with 10/20% reduced N rates for cereals/maize and only slight reductions in cereal protein content. Nitrate concentration from adapted N rates was significantly lower in treatments with an application of organic fertilisers (−7.74 mg NO3-N l−1) with greatest potential after cultivation of maize; in only mineral fertilised plots the effect was smaller (−3.80 mg NO3-N l−1). Cumulative leaching losses were positively correlated with post-harvest soil mineral nitrogen content but even in unfertilised control plots losses >50 kg N ha−1 were observed in some crop-years. Reduced N rates led to decreased leaching losses of 14% (6.3 kg N ha−1 a−1) with mineral and 29% (20.1 kg N ha−1 a−1) with organic + mineral fertilisation on average overall cops and years. The presented study revealed the general potential of adapted fertilisation strategies with moderately reduced N applications (−10/−20%) to increase leachate water quality without affecting significantly crop yields. However, regionally typical after-effects from yearlong high N surpluses in livestock intensive farming systems are a limiting factor.

Model Study to Determine the Manning’s Coefficient for Gabion Lining against Canal Erosion

Canal erosion often happens in unlined canals due to high velocity water flows. Because of this natural phenomenon, numerous problems occur in canal systems and finally change the topography of the canals in the long-term. Canal lining is the method adopted worldwide, to prevent canal erosion using different lining materials available such as concrete, rock masonry, brick or clay, with the modern practice being gabion nets filled with rubble. Considering several factors such as, economy, stability, material availability and manpower requirement, gabion lining is a suitable canal lining method compared to other prevention methods used at present. To make the gabion lining method very effective, economical and feasible in canal lining applications, the surface roughness or the Manning’s coefficient (n) value of gabion linings needs to be experimentally determined first, as this value is unknown at present and will be useful for the scientists and engineers in design stages later on. A 300 mm x 300 mm rectangular field channel was selected as the prototype to model it dimensionally in a laboratory hydraulic flume. The Manning’s formula, which applies to uniform flow conditions in open channel flow, was used to determine “n” experimentally. Present experimental observations indicate a value range of 0.05044 m-1/3s to 0.0552 m-1/3s as Manning’s coefficient for the test model study and that of 0.0597 m-1/3s to 0.0654 m-1/3s for the prototype.

High water flow velocity reduces beta diversity and leads to a distinct composition of Oligochaeta in Neotropical lotic ecosystems

Water flow velocity is a strong environmental filter structuring benthic communities in lotic ecosystems. While many studies have determined its effect on the distribution and diversity patterns of insects, the role of water flow velocity on other groups of aquatic invertebrates (i.e., Oligochaeta) has remained unexplored. We sampled five lotic ecosystems to investigate the influence of water flow velocity on the species composition of Oligochaeta assemblages in a Neotropical floodplain. Our first hypothesis was that higher water flow velocity decreases Oligochaeta assemblages variability. Consequently, we expected a lower beta diversity among the mid-channels of the ecosystems (i.e., sites with higher water velocity) relative to channel margins (i.e., sites with lower water velocity). Our second hypothesis was that water flow velocity determines species composition of Oligochaeta. Consequently, we expected a different species composition between the mid-channel and the channel margins of lotic ecosystems. We found 19 Oligochaeta species across the five lotic ecosystems. We corroborated both hypotheses because we found lower Oligochaeta beta diversity among the mid-channels of the lotic ecosystems as well as a different species composition. Haplotaxis aedeochaeta and Narapa bonettoi were the taxa strongly associated with the mid-channel, because they are adapted to live among the sand grains in the bottom of the rivers with high depth and water velocity. Overall, water flow velocity should be considered as a strong driver of Oligochaeta species composition.

Detachment of dilatant soil due to high hydraulic shear stresses explained

When soil surfaces are exposed to high shear stresses induced by high-velocity water flows, they erode. Erosion consists of the detachment, entrainment and transport of soil particles. When exposed to high shear stresses the process of soil detachment is no longer given by the pick-up of individual particles but by the continuous shear failure of layers of soil. The understanding of how soil properties influence the detachment rate of soil is lacking. This paper presents how the bed shear stress, initial and critical porosity, hydraulic conductivity, and density influence the detachment rate of dilatant soils which are subjected to high-velocity flows. Based on the constitutive mass and momentum balance equations it is hypothesized that the exchange of mass and momentum during soil detachment corresponds with that situation for which the dilatancy induced shear resistance of the soil is maximum. The hypothesis is validated against high-velocity erosion experiments on sand.