Sediment Erosion Research Articles

Analysis of Sediment Erosion in Pelton Nozzles and Needles Affected by Particle Size

The sediment erosion of Pelton turbine components is a major challenge in the operation and development of high-head water resources, especially in mountainous areas with high sediment yield. In this paper, a study using numerical simulation was conducted with different sediment particle sizes in the fine sand range. And the erosion mechanism of the Pelton turbine injector was analyzed. The Eulerian Lagrange method was adopted to simulate the gas–liquid–solid flow. The Mansouri’s model was applied to estimate the injector erosion. The predicted erosion results were in accord with field erosion photographs. In particular, the asymmetrical erosion distribution on the needle surface was physically reproduced. With the sediment particle size increasing from 0.05 mm, the needle erosion rate decreased, while the nozzle casing erosion rate increased dramatically. In order to clarify this tendency, the characteristics of the three-phase flow were analyzed. Interestingly, the results show that with the rise in particle size, the separation of particles and water streamlines became more serious in the contraction section of the nozzle mouth. Consequently, it caused the enhancement of erosion of the nozzle surfaces and weakened the erosion of the needle surfaces. Significant engineering insights may be provided for weakening Pelton injector erosion with needle guides in the current study.

Numerical study on sediment erosion characteristics of Francis turbine runner

Sediment erosion is a prevalent and significant challenge to hydro turbines in mountainous rivers. In order to gain an insight into the erosion characteristics of Francis turbines, this study considers the influence of actual sediment gradation and emphasizes the erosion mechanism from the perspective of flow structure. Numerical results reveal a significant correlation between erosion distributions and the location of inter-blade vortices, which is dependent on operating conditions. Specifically, at small or optimal openings, inter-blade vortices predominantly form on the suction side of blades, which coincidentally experiences the most severe sediment erosion. Conversely, at a large guide vane opening, sediment erosion and vortices are primarily distributed at outlet of pressure side, aligning closely with actual site observations at a hydropower station. With increase of operating heads, the average erosion rate of suction side decreases at all guide vane openings, while that of pressure side elevates significantly. In addition, the effect of particle size on sediment erosion was discussed and the maximum erosion rate is demonstrated to be proportional to sediment diameter. These findings would provide important engineering insights for operation optimization to reduce sediment erosion.

Impact of initial slide on downslope seafloor with a weak layer

Submarine landslides are a major offshore geohazard posing increasing threat to offshore and coastal developments. A submarine landslide may usually involve multistage failure triggered by the first failure. During submarine landslide evolution, the emergent sliding mass may act as an impact load on the downslope seafloor potentially leading to surficial erosion of sediments or deeper ploughing failure with the presence of a weak layer. The study presents a comprehensive analysis of seafloor instability and post-failure behaviors subjected to the first slide mass impact, using a large deformation finite element (LDFE) method. Different failure patterns are investigated and the corresponding critical impact loads for triggering the seafloor instability are analyzed. The parameters controlling the strain softening behaviors of soils and the undrained shear strength in the weak layer have significant effects on the critical condition for the seafloor failure. The dynamic inertia of the slide mass, however, has little effect on the results. An empirical equation for assessing the seafloor instability subjected to the first slide impact, with respect to the impact load from the initial slide and the gravity stress relative to the shear strength in the weak layer, is proposed based on a parametric study.

Impact of large wood on sediment (dis)connectivity in a meandering river

Large wood (LW) can exert strong influence on sediment storage patterns in fluvial systems. However its specific impact on sediment routing is largely dependent on the stability of individual LW pieces or LW jams. We used sediment (dis)connectivity principles to quantify the impact of LW on sediment erosion and storage along a meandering river reach. Decadal spatiotemporal changes of LW and fluvial landforms are appraised along a 3.65 km long reach of the Odra River (Czechia). Detailed orthophotos at two-year intervals from 2012 to 2022 are analysed alongside field inventories. During this study period, there was a single flood event with a 5–10-year recurrence interval, and three smaller flow events with a recurrence interval of up to 2 years. We assessed the sediment deposition, bank protection, and erosion effects of LW, finding that the impact of LW on decelerating sediment fluxes was more pronounced. Specifically, LW-related deposition varied between 13.6 m2 and 36.7 m2 per 100 m of channel length during the individual two-year periods. In contrast, we detected only 0.5 m2 to 7.8 m2 per 100 m of channel length of newly eroded material during the same periods. Additionally, 6.3 % to 7.8 % of the lengths of the outer meander bends were protected by persistent LW elements against erosion during these two-year periods. Finally, we developed a three-stage conceptual model depicting the impact of LW on sediment (dis)connectivity in a meandering river at different relative timescales. Our model accounts for the dependence of interactions between LW and fluvial sediments based on the LW stability and frequency-magnitude of the hydrogeomorphic processes. In general, our observations suggest that the presence of stable LW in meandering rivers primarily leads to the deceleration of the lateral and longitudinal dimensions of sediment (dis)connectivity.

Synergetic evolution mechanism of coastal resources utilization and coastline change of muddy coast in Jiangsu

Coastal areas possess unique geographical advantages and abundant resources, making them economic development hubs for coastal cities worldwide. However, the overexploitation of coastal resources significantly impedes the sustainable development of these areas. To address this issue, it is crucial to gain a comprehensive understanding of resource utilization patterns over time. Previous studies on resource utilization in the coastal areas of Jiangsu, China, have primarily relied on historical narratives with limited quantitative assessments. In this study, we utilize the Resource Utilization Comprehensive Index (RUCI) to evaluate the status of resource utilization in Jiangsu's coastal areas for the last 1300 years. Based on the characteristics of coastline changes from the Tang Dynasty to 1929 analyzed through the Digital Shoreline Analysis System (DSAS) in ArcGIS, we use entropy weight method (EWM), gray relation analysis (GRA) and Pearson correlation coefficient to determine the RUCI of coastal areas in Jiangsu and analyze its correlation with each evaluation index and influencing factor. The results show that (1) over the past 1300 years, the coastline of Jiangsu primarily underwent a sedimentation process characterized by three stages: slow sedimentation, rapid sedimentation, and north erosion followed by south sedimentation, (2) the comprehensive utilization of resources along the Jiangsu coast was gradually developed from the Tang Dynasty to the Republic of China, with the best utilization achieved during the Qing Dynasty, and (3) the changes in the coastline exhibited a substantial influence on the comprehensive utilization of resources and there was a high correlation between the two. Based on these findings, we propose several policy development suggestions. This study provides a scientific basis for understanding the synergetic evolution mechanism of coastal resources utilization and coastline change in Jiangsu under global change.

On certain issues related to the place of lithodynamic processes in the general classification of geologic hazards and phenomena

The article addresses issues related to the study of lithodynamic processes on the shelf as dangerous phenomena. On the example of the coastal zones of South Sakhalin where hazardous exogenous processes on the shelf are state-monitored, it is shown that an annual redistribution of bottom sediment accumulation and erosion zones occurs within the identified key areas. Other examples from the practice of similar works in the Gulf of Finland of the Baltic Sea indicate that lithodynamic processes in the coastal zone lead to a significant disturbance of the coast, which poses a specific danger to the population. It is concluded that lithodynamic processes should be studied via standard lithological and geophysical methods used in marine geological work.

Human interventions alter morphodynamics of meandering channels: Insights from decadal to pre-industrial observations in the Yangtze River

Human activities, such as reservoir construction and bank revetment, significantly alter downstream flow and sediment regimes and river channel changes, impacting river ecosystem services. However, our understanding of how intense human activities affect morphodynamics of meandering channels in big river systems remains incomplete due to the lack of high-resolution in-situ data. Here, we use comprehensive data encompassing hydrology and sediment, historical channel maps, and high-resolution river bathymetry to investigate the evolution of meandering bends in the Middle Yangtze River (MYR) across three distinct phases: the natural period (1490–1975), the bank revetment period (1975–2002), and the post-dam period (2003–2018). The study revealed that, in the absence of human intervention, the meandering channels of the MYR naturally experienced inner bank deposition and outer bank erosion, largely governed by curvature-induced secondary flow patterns in flow and sediment transport mode. In 1975–2002, outer-bank revetments reduced erodibility, stabilizing outer banks, while inner banks continued to experience lateral and vertical deposition, causing a narrower and deeper channel hydraulic geometry. Conversely, meandering bends had exhibited an unusual pattern of ‘outer bank deposition and inner bank erosion’ in 2003–2018. Channel morphological changes characterized by channel incision and widening were driven by changes from erodible bank boundaries to solidified bank boundaries, substantial reduction in suspended sediment concentration, and an altered and extended effective flow range (10,000–25,000 m3/s). Our findings highlight that human interventions such as damming and bank revetments can alter the conventional erosion–deposition morphodynamics of meandering bends in large river systems, carrying vital implications for sustainable river management in the Anthropocene.

HVOF-sprayed surface coating with various compositions of Co-NiCrAlY-Al2O3 to minimize sediment erosion in hydraulic turbines

The components of hydropower plants are susceptible to sediment erosion caused by hard particles in the water. These hard particles cause substantial material loss and a reduction in the performance of the hydraulic turbines. The present study deals with the mitigation of sediment erosion in hydraulic turbines by developing a protective coating (CoNiCrAlY-Al2O3 metal-ceramic composite) using a high-velocity oxygen-fuel (HVOF) coating technique. Hardness measurement, surface wettability analysis, and surface roughness measurement were conducted to characterize the coatings, whereas scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS) were performed for metallurgical characterization. The slurry/sediment erosion behavior of bare and coated substrate was investigated using a slurry erosion tester. Experiments were performed for five coating compositions at different impact angles (30° ≤ ϴ ≤ 90°) and velocities (6 ≤ v ≤ 12 m/s). The maximum improvement in erosion performance (reduction in erosion rate compared to bare substrate ≈ 28.12 % at 30°, 9.29 % at 45°, and 11.69 % at 90° impact angle) was obtained for the coating having 12 wt% alumina doped into Co-NiCrAlY. The coating's performance was improved due to increased hardness, high shielding effect, and reduction in impact energy on Al2O3 by using CoNiCrAlY-Al2O3 deposition. The empirical correlation between erosion rate and velocity for both bare and coated substrates has also been proposed.

Mangroves as Coastal Protection for Restoring Low-Energy Waterfront Property

Mangroves offer vital ecological advantages including air and water filtration, coastal and estuarine habitat provision, sediment stabilization, and wave energy dissipation. Their intricate root systems play a key role in safeguarding shorelines from tsunamis and erosive storms by dissipating wave energy. Moreover, mangroves shield against boat wakes and wind-waves, thus naturally bolstering shoreline defense. Wave dissipation is a function of forest width, tree diameter, and forest density. Restoration efforts of juvenile mangroves in Florida’s Indian River Lagoon (IRL) aim to reduce wave energy in areas vulnerable to erosion. Physical model testing of wave dissipation through mangroves is limited due to the complexity in representing the mangrove structure, where prop roots are non-uniform in both diameter and location. Previous studies have quantified wave-dissipating effects through the use of scaled and parameterized mangrove structures. This study measures the dissipation effects of live mangroves in a wave flume, forced by conditions representative of the IRL. These measurements are used to validate a parameterized dowel model. Error between wave attenuation factors for the live mangrove and dowel system was on average 2.5%. Validation of the modularized dowel system allowed for further parameterized testing to understand forest structure effects, such as sediment stabilization and wave attenuation. Maximum wave attenuation achieved in this study was 27–35% corresponding to a 40–60% reduction in wave energy depending on the configuration of the system. The wave reduction resulted in a 50–70% decrease in sediment erosion from the berm. The dowel tests indicate a target minimum thickness for mangrove root systems of 0.6 m for shoreline stabilization and restoration in the IRL.

Sediment production process and hydraulic characteristics of ephemeral gully erosion in granite hilly area

Ephemeral gully (EG) erosion represents the early stage of large-scale gully (locally named as “Benggang”) development on Ultisols in the granite hilly area. However, the EG erosion process and the mechanism underlying sediment production have not been fully elucidated. In this study, a series of field scouring experiments were conducted under different flow discharge levels (10, 15, 20, 25, and 30 L·min−1), and the primary EGs in three typical soil layers with different weathering degrees (red soil layer (RL), transition layer (TL), and sandy layer (SL)) was dynamically monitored. The results indicated that the ratio of width to depth of the EGs rapidly decreased as the flow discharge increased. At 30 L·min−1, the average sediment yield and transport rate (Sr) of the SL were 4.85 and 5.39 times, greater than those of the RL, respectively. The sediment particles were concentrated within the 1–2 mm particle size range, accounting for over 35 %. In addition, the mean weight diameter of the sediment particles in the RL was the largest. The sediment distribution characteristics did not respond to flow changes but were affected by EG morphological changes. With increasing flow discharge, the flow shear stress and stream power increased. Further analysis revealed that the coupling effect of flow hydraulic characteristics and EG morphological evolution drove the EG erosion sediment production process, and the Sr of the SL was highly sensitive to flow discharge changes. The soil disintegration rate was an internal factor that directly affected soil loss in the EGs, with a path coefficient of 0.71. The bulk density, organic matter content, and sand content were all indirect influencing factors. The RL exhibited greater anti-erodibility than the other layers and could serve as an effective protective layerfor granite hilly areas. These findings provide a theoretical basis for improving soil loss management systems.

Fluid-evolving landform interaction by a surface-tracking method

This paper introduces a continuous finite element model to simulate fluid flow-bedform interaction problems. The approach utilizes a non-oscillatory finite element algorithm to compute the fluid dynamics by solving the complete Navier–Stokes equations. Additionally, it addresses the evolution of the fluid–bedform interface as a consequence of spatially non-balanced sediment fluxes through the solution of a conservation equation for the erodible layer thickness. A sign preservation algorithm is particularly relevant for landform tracking because a positive definite thickness of the erodible sediment layer is essential to model the interaction between evolving cohesionless sediment layers and rigid beds. The fluid/terrain interface is explicitly captured through a surface tracking methodology. First, new nodes fitting the interface are incorporated into the finite element mesh; then, elements beneath this interface are deactivated, while intersected elements are restructured to get a mesh composed exclusively of tetrahedral elements. Numerical experiments demonstrate capabilities of the method by exploring relevant problems related with civil engineering, such as the evolution of trenches and the scour of a submerged pile.

Hydro‐Sedimentary Processes of a Plunging Hyperpycnal River Plume Revealed by Synchronized Remote Imagery and Gridded Current Measurements

AbstractThe present knowledge of plunging hyperpycnal river plumes is mainly based on two‐dimensional (confined) laboratory experiments. Several hypotheses on three‐dimensional (unconfined) flow processes have been made, but not tested in situ. In this field study, the dominant three‐dimensional hydro‐sedimentary processes related to unconfined plunging were elucidated by synchronizing autonomous time‐lapse camera images with boat‐towed acoustic Doppler current profiler measurements. It was found that the flow field complies with two‐dimensional conceptualizations along the plume centerline. Perpendicular to the centerline, the plume slumped laterally due to its density excess and simultaneously converged laterally due to its vertical divergence. This combination led to a narrowing of the plume near the surface, resulting in a sediment‐rich triangle‐shaped pattern on the surface near the inflow, and a rather stable width near the bed. The formation of secondary flow cells transporting riverine water and suspended particulate matter (SPM) away from the plume near the bed, up toward the surface and back toward the plume near the surface, was revealed. An increase of the average SPM concentration and the SPM flux in the main flow direction indicates net sediment erosion under the investigated conditions of high discharge and sediment load. This suggests transient storage of sediment during conditions of lower discharge and sediment load, and high morphological activity in the plunging area. These findings allowed extending a classical conceptual plunging model to laterally unconfined sediment‐laden plunging inflows for conditions of well‐mixed ambient water in the plunging region and inflow densimetric Froude numbers exceeding 1, common in nature.

A Review of the Sediment Production and Transport Processes of Forest Road Erosion

Forest roads are a common land use feature with a significant impact on sediment yield and the water sediment transport processes within a watershed, seriously disrupting the safety and stability of the watershed. Previous studies have focused on the sediment production processes within the road prism. However, there has been limited attention given to the transport processes of road-eroded sediment at various scales, which is crucial for understanding the off-site effects of road erosion. This paper reviews research conducted on forest road erosion over the past two decades. It summarizes the mechanisms of sediment production from road erosion and provides a detailed analysis of the transport mechanisms of eroded sediments from roads to streams at the watershed scale. The paper also examines the ecological and hydrological effects, research methods, and control measures related to sediment transport caused by forest road erosion. It identifies current research limitations and outlines future research directions. The findings of this review highlight several key points: (1) Most research on forest road erosion tends to be specific and unilateral, often neglecting the broader interaction between roads and the watershed in terms of water–sediment dynamics. (2) Various research methods are employed in the study of forest road erosion, including field monitoring, artificial simulation experiments, and road erosion prediction models. Each method has its advantages and disadvantages, but the integration of emerging technologies like laser scanning and fingerprint recognition remains underutilized, hindering the simultaneous achievement of convenience and accuracy. (3) The transport processes of forest road-eroded sediment, particularly on road–stream slopes, are influenced by numerous factors, including terrain, soil, and vegetation. These processes exhibit significant spatial and temporal variability, and the precise quantification of sediment transport efficiency to the stream remains challenging due to a lack of long-term and stable investigation and monitoring methods. The establishment and operation of runoff plots and sedimentation basins may help offer a solution to this challenge. (4) Both biological and engineering measures have proven effective in reducing and limiting sediment erosion and transport. However, the costs and economic benefits associated with these regulation measures require further investigation. This review provides a comprehensive summary of relevant research on sediment erosion and transport processes on unpaved forest roads, enhancing our understanding of sediment yield in watersheds and offering valuable insights for reducing sediment production and transport to streams.

Mechanism of the influence of sand on the energy dissipation inside the hydraulic turbine under sediment erosion condition

Sediment erosion can lead to a general decrease in hydraulic performance of hydraulic turbines and an increase in energy dissipation. In this paper, aiming the characteristics of SE at the clearance the erosion model was modified. The purpose is to study the influence of sediment erosion on the energy dissipation inside the hydraulic turbine. Research shows that the blade is most severely worn near the lower ring of the runner, which can lead to structural loss and hydraulic model changes. The impact of particle size on clearance erosion is much greater than that in a large space flow channel. The particle size affects the impact angle and impact velocity of particles, and is more pronounced at the clearance. The larger the particle size, the greater the acceleration of the jet within the guide vane clearance, exacerbating the SE and leakage of the guide vane clearance. The jet from the guide vane clearance propagates into the runner blade channel, exacerbating energy dissipation. SE can cause the local structure undergoes changes, leading to an increase in local jet flow and deterioration of flow patterns, increasing local energy dissipation. Among various components, the runner is most severely worn, and energy dissipation dominates.

Rock and ice avalanche-generated catastrophic debris flow at Chamoli, 7 February 2021: New insights from the geomorphic perspective

Within mountainous landscapes neighboring glaciers, slope instabilities and consequent catastrophic mass flows are vital processes on Earth's surface, which have been of increasing interest for decades. These events commonly exhibit large volume, high velocity, and high mobility. Recently, a catastrophic debris flow occurred in India on 7 February 2021, which unfortunately claimed 70 lives and left 134 people missing. The failed mass comprises 80 % rock debris and 20 % glacier ice. Our remote sedimentological investigation of remnant deposition shows clear evidence of wet granular flow in upper Ronti Gad valley, which doesn't support the previous interpretation of immediate melting of the failed 20 % ice mass during the falling and impacting process. We further utilized the superelevation phenomenon to back-calculate the velocity downstream of the impact zone, and estimated the peak discharge, which is verified by field-documented data. Our results revealed an initial waning trend of rock and ice mass flow. As it entered the narrow valley of the lower Ronti Gad River, the extensive material erosion resulted in three-fold flow enlargement, which gave rise to a maximal peak discharge of up to 48–54 × 104 m3/s. The transition from granular flow to debris flow occurred in the 2-km-long channel downstream of the Ronti Gad-Rishigangga confluence. The sediment deposition of 4.8 × 104 m3 and the incorporation of stream water in this zone have dominated the rheologic transition. We inferred that the intense erosion of erodible sediment due to topographic constraint plays an essential role in maintaining the mobility of the flow. Therefore, the effect of glacier ice meltwater on high mobility may be overestimated. As long as the granular flow can access the stream water in major rivers, flow transformation can easily happen because of sufficient water supply in the channel. The valley morphology in the proglacial region is commonly featured by the shift from an upstream U-shaped valley carved by glacier erosion into a downstream fluvial-erosion-dominated V-shaped valley. This geomorphic setting of glaciated tributary favors the long-distance run-out of rock and ice avalanche.

Non-negligible contribution from coastal erosion to sedimentation around the archipelago: A case study of Miaodao Archipelago

The Miaodao Archipelago, located in the southern Bohai Strait, serves as a major route for the exchange of energy and materials between the Yellow and Bohai seas and is distinguished by a complicated hydrodynamic environment and provenance. Based on the grain size and elemental data of 107 surface sediment samples from the archipelago waters, and 58 coastal erosional sediment and bedrock samples, this study investigated the factors influencing the geochemical elemental distribution, discusses the provenance of the surface sediments and relative contributions, as well as proposes a sediment source–sink model for the region. The distribution of major and trace elements in the surface sediments, typically characterized by “high in the north, low in the south” patterning (except for SiO2, Ba, and Sr), with their contents primarily controlled by the input of terrestrial materials. The surface sediments in the study area are separated into the geochemical subdivisions of north and south. The main provenances of the study area include the Yellow River, the nearshore Miaodao Archipelago, and the north side of nearshore Penglai, whose sediments were transported under the combined action of the Shandong Peninsula's tidal current, waves, and longshore current. Deposition occurred under the capturing action of the archipelago. The relative contributions of the three provenance areas were 74.7%, 15.5%, and 9.8%, respectively; the relative contribution of coastal erosion reaches 1/3 of the river. Studies have demonstrated that the contribution of coastal erosion provenances to sea surface sediments is non-negligible, and in fact, it may even be quite important; thus, in the context of decreasing riverine inputs to the sea and enhanced coastal erosion processes, the contribution of coastal erosion requires special attention.

Investigation on sediment erosion in bucket region of Pelton turbine considering cavitation

In the context of constructing high-head hydro-power stations, the Pelton turbine assumes a critical role as the primary energy converter. This study employs the Eulerian–Lagrangian method to simulate the multi-phase flow occurring within the Pelton turbine bucket. Furthermore, it introduces a novel aspect by investigating and comparing the effects of cavitation on erosion within the bucket region under varying conditions of sediment-water, involving different particle sizes and concentrations. The research findings unveiled several key insights. Primarily, cavitation predominantly influences the flow characteristics of particles at the air–liquid interface, while particles with larger sizes tend to concentrate in the center of the jet. Consequently, cavitation's impact on erosion is more pronounced in the case of smaller-sized particles. Moreover, the study revealed that cavitation can either exacerbate erosion under high particle concentration conditions or mitigate it when particle concentration is low. Furthermore, the investigation highlighted variations in the degree of erosion and the affected area of the bucket based on different position angles. Particularly, at a position angle of 65°, the presence of water vapor induced by cavitation alters particle trajectories, thereby modifying the overall erosion pattern of the bucket. These findings collectively contribute to a deeper understanding of the complex interplay between cavitation and erosion within the Pelton turbine bucket.

Numerical assessment of erosion wear in Pelton turbine injectors

The Pelton turbine is the main type of turbine used to develop hydropower resources in high-head sections and is more sensitive to sediment erosion. To analyse the causes of asymmetric erosion distribution on the injector surface, a solid-liquid-gas three-phase numerical study of Pelton turbine injectors is carried out. The results indicate that as the sediment diameter increases, the differences in particle discharge distribution among the jets of each branch also increase, and the asymmetric erosion distribution on the injector surface becomes stronger. The particle trajectory is influenced by the vortex structure, and fine particles mainly cause banded erosion, while coarse particles cause sheet erosion. At constant inflow conditions, the particle residence time is related to erosion morphology, and the particle velocity and the number of impacts affect the erosion rate on the injector surface. It is recommended to avoid long-term operation of the turbine under conditions of excessively small or large sediment diameters and to pay attention to the sediment erosion degree of the middle branch needle and the end branch nozzle of the water supply mechanism. The research findings of this paper can provide references for further optimization of the design, operation, and maintenance of the Pelton turbine.

Effect of multiple factors on sediment erosion characteristics of hydro turbine materials

Hydraulic turbines on sediment-laden rivers suffer from cavitation-silt erosion. This study conducted cavitation-silt erosion tests on three materials (06Cr16Ni5Mo, Q355B, 06Cr20Ni11) with different sediment concentrations and impact velocities using a rotating disk facility, and used a scanning electron microscope (SEM) to observe the cavitation-silt erosion characteristics of the materials. The results show that the cumulative weight loss of all materials continuously increases with the sediment concentration and impact velocity rises. The weight loss of 06Cr16Ni5Mo is the lowest, and 06Cr20Ni11 is the highest. As the impact velocity rises, the cumulative weight loss increases exponentially. As the sediment concentration rises, there are obvious scour marks and fatigue spalling on the material surface. As the impact velocity rises, the size and depth of micro-cutting marks and cavitation pits increases. Due to the lower surface hardness of 06Cr20Ni11, the deep platelet pits appear on the material surface.

Petrography study of the recent sediments in Hareer’s region at Basrah Governorate - Southern Iraq

Two sites of Hareer’s region is located in the southern part of Iraq, specifically in the northern Basrah Governorate. The sites are at a depth of 5 meters. The results of heavy mineral analysis showed that there are fifteen types include; Opaque grain (Iron Oxide), Chlorite, Muscovite mica, Biotite, Orthopyroxene, Clinopyroxene, Amphibole (Hornblende and Actinolite), Epidote, Garnet, Kyanite, Staurolite, Zircon, and Tourmaline. On the other hand the light minerals and the results of the mineral analyses revealed that they were primarily composed of rock fragments, with a variety of quartz minerals, feldspar minerals, evaporate minerals, clay-coated grains, and trace amounts of unidentified minerals. The abundance and diversity of heavy minerals indicate the diversity of the sources of the parent rocks, such as igneous, metamorphic and sedimentary rocks. The large amount of opaque and small amount of other minerals in the study area samples is due to the oxidation process where many of the ferromagnesian minerals such as pyroxenes, and hornblende decompose to form iron oxides (e.g. hematite, limonite). Light minerals were visible as irregular, sharp, or occasionally semi-sharp crystalline forms, which suggests that the sources were close by and that the light minerals originated from the sedimentary basin or within it through the processes of deposit erosion and re-deposition. The study area, which is a part of the Undissected Arc, is primarily distinguished by a high content of quartz (mono- and polycrystalline quartz, including chert), and feldspar, which can occur in fluvial environments.