Erosion Depth Research Articles

The principle, application, and prospect of using the uranium comminution age to indicate the catchment erosion depth

The principle, application, and prospect of using the uranium comminution age to indicate the catchment erosion depth

Integration of CFD simulated abrasive waterjet flow dynamics with the material removal model for kerf geometry prediction in overlapped erosion on Ti-6Al-4V alloy

Complex surfaces in difficult-to-machine materials can be milled by maneuvering the abrasive waterjet (AWJ) according to the local part geometry by suitably overlapping the kerf cross-sectional profiles (CPs). The CP of a kerf milled in a single pass (i.e., trench) and overlapped pass (i.e., cavity) erosion by the AWJ are the building blocks that need to be known apriori for developing a jet path strategy to achieve a complex surface. This demands an efficient model for the kerf CP prediction. The present work proposes a novel framework for overlapped kerf CP prediction, wherein the jet characteristics of the AWJ exiting the focusing tube are evaluated from the two-phase flow computational fluid dynamics simulation coupled with the material removal model developed based on energy conservation principles. Towards incorporating the non-linearities observed in the kerf formation from the overlapped experimental trials into the model for CP prediction enhancement, the following are considered: (i) a hypothesis: ‘secondary erosion by the jet on the previously eroded kerf increases material removal’, (ii) the varying jet-material property of the ductile material (Ti-6Al-4V alloy), and (iii) local particle impact angles. Furthermore, the variation in the above mentioned non-linearities is incorporated into the model under the change in the AWJ conditions. From the results, it is observed that the proposed models predicted (i) the trench CP with a mean absolute error (MAE) of 27 μm, and the maximum erosion depth (hmax) with an error < 2%, and (ii) cavity at different overlaps (7% – 82%) and jet traverse rate (3000 mm/min – 5000 mm/min) with a MAE of 47 μm, and the hmax with an error < 6%. The predicted geometry of the CP correlates well with the experimental ones, with an average R2 of 0.98 and 0.95 in single- and overlapped- pass erosions.

Erosion-inhibiting potential of the stannous fluoride-enriched CPP-ACP complex in vitro

Currently available anti-erosive agents only provide partial protection, emphasizing the need to enhance their performance. By characterizing erosive enamel wear at the nanoscale, the aim of this in vitro study was to assess the anti-erosive effects of SnF2 and CPP-ACP both individually and synergistically. Erosion depths were assessed longitudinally on 40 polished human enamel specimens after 1, 5, and 10 erosion cycles. Each cycle comprised one-min erosion in citric acid (pH 3.0) and one-min treatment in whole saliva (control group) or a slurry of one of the three anti-erosive pastes (10% CPP-ACP; 0.45% SnF2 (1100 ppm F); or SnF2/CPP-ACP (10% CPP-ACP + 0.45% SnF2)) (n = 10 per group). Scratch depths were assessed longitudinally in separate experiments using a similar protocol after 1, 5, and 10 cycles. Compared with the control groups, all slurries reduced erosion depths after 1 cycle (p ≤ 0.004) and scratch depths after 5 cycles (p ≤ 0.012). The order of anti-erosive potential was SnF2/CPP-ACP > SnF2 > CPP-ACP > control for erosion depth analysis, and SnF2/CPP-ACP > (SnF2 = CPP-ACP) > control for scratch depth analysis. These data provide ‘proof of concept’ evidence that SnF2/CPP-ACP has superior anti-erosive potential compared to SnF2 or CPP-ACP alone.

On erosion transition from the incubation stage to the accumulation stage in liquid impingement erosion

The evolution of surface profiles during erosion caused by the continuous impact of a liquid jet was studied using a water-jet apparatus. In this study, we focused on the erosion transition from the incubation stage to the accumulation stage during liquid impingement erosion, which is important for water-jet cleaning and aging management for nuclear power plants. By computing the local erosion rate distribution and surface roughness parameters, the formations of isolated pits and asperities were investigated. The structure of erosion caused by liquid impingement was extracted by using a dynamic mode decomposition technique. The surface profile changes were primarily caused by the formation of isolated pits and asperities during the incubation stage. The roughness parameters remained unchanged during the incubation stage, with barely measurable erosion depth, whereas the skewness of the surface profile began to increase during this stage. The initial erosion with a small-scale roughness gradually evolved into a large-scale crater. Dynamic mode decomposition analysis showed the presence of a short-wavelength (mode A) surface depression during the incubation stage, followed by a long-wavelength (mode B) erosion crater caused by the merging of mode A surface depressions during the accumulation stage.

The effect of groins characteristic on sandy beach stability

Groins are one of the most important facilities used to protect coastal regions. In this research, groins made from a concrete cube were tested experimentally. This research investigates the impact of groin length (Lg) of 105, 135, and 165 cm and groin angle with the normal axis of the shoreline (θ) of 0°, 10°, 20°, and 30° under different dimensionless wave numbers (khg), from 0.34 to 1.26, with the beach slope of 8:1. The units used to indicate erosion and deposition are dimensionless erosion depth (Smax/h), dimensionless deposition height (Dmax/h), and dimensionless erosion hole length (lsmax/h). The sandy bed changes and wave reflection from the groin were monitored. The results showed that the angle of 30° had more impact on beach stability than that of 0°, and more sediments were eroded by short groins than by long ones. The reflection of waves from groins was also studied as a function of the reflection coefficient (kr). As concluded, short groins reflect higher waves than long ones.

Numerical simulation and analysis of contact erosion by high-current and low-voltage air arc considering the movement of arc

When a low-voltage circuit breaker (LVCB) breaks a high current, the contact erosion caused by the arc greatly reduces the LVCB’s breaking performance and service lifetime. Therefore, this paper uses AgW alloy contacts as a research object, which are commonly used for breaking high currents, and establishes a contact erosion model for an LVCB with a breaking current of 14 kA. The model considers the energy balance of a contact surface and uses a solidification and melting model and a dynamic mesh model to deal with the phase transition problem of the contact material and introduces the arc movement into this model. Using this model, the contact melting and evaporation width, erosion depth, erosion rate, and erosion mass are calculated when Ag and AgW30 and AgW70 alloys are used as contact materials. The influence of W-content on the erosion characteristics of a contact is analyzed. The results show that, although the introduction of element W significantly reduces the erosion mass, it advances the time when the melting point and boiling point are reached. The position, width, and depth of the melting pool and melting layer thickness change with the movement of the arc. In the process of contact erosion considering the movement of the arc, the introduction of W element will increase the width of the molten pool and the solidification time of the molten material. Especially when the mass percentage of element W in the contact material reached 70%, the solidification time of the molten material greatly increased, which weakened the welding resistance of the contact.

Modeling Sediment Resuspension and Transport Processes Induced by Propeller Wash from Ship Traffic

Resuspension and redistribution of sediments induced by propeller wash may significantly influence aquatic ecosystems at contaminated sediment sites. This study describes a numerical modeling method developed to predict the sediment resuspension and subsequent transport processes resulting from ship traffic, with a fully coupled simulation of hydrodynamics, sediment transport, and propeller wash. By including propeller momentum effects in the flow field computation, the advection and dispersion of resuspended sediments are better represented than in previously available methods. To achieve this improvement, a computational algorithm was first developed to calculate the propeller wash effects from one or more ships (e.g., erosion rate and momentum flux); these results were then dynamically linked to a hydrodynamic and sediment transport computation using Environmental Fluid Dynamics Code Plus (EFDC+). This modeling framework was evaluated using a field experiment conducted by the US Navy. The model was calibrated with flow velocities and sediment erosion depths, and then validated with resuspended sediment concentrations in the water column. The model results reproduced the horizontal and vertical distributions of resuspended sediments better when the propeller-induced momentum was incorporated into the flow field computation. The sensitivity test indicated that the increased flow energy from propeller momentum resulted in significant dispersion of resuspended sediments in both longitudinal and lateral directions. The maximum scour was dependent on the propeller revolution speed, the ship engine power, and the distance between the propellers and the sediment bed.

An experimental study on the erosion of sandstone by self-excited oscillation cavitation waterjet in submerged environment

Self-excited oscillation cavitation waterjet (SOCW) has good prospects for application in deep sea mineral extraction of its cavitation characteristics. This study conducted the erosion experiments of three types of sandstone, red sandstone, white sandstone, and black sandstone by SOCW under a submerged environment. The erosion characteristics of three types of sandstones under the impact of SOCW at various erosion times, standoff distance, and pressure were compared. It was found that, a) Red sandstone with larger porosity is more likely to produce a large damage area and has the best rock breaking effect. Taking the standard working condition of this experiment as an example (t = 50s, Pj = 16 MPa, S/De = 4), the erosion depth of red sandstone can reach 1.9 times that of white sandstone and 5.5 times that of black sandstone; the erosion area can reach 19.6 times that of white sandstone and 6.2 times that of black sandstone; the erosion quality can reach 5.2 times that of white sandstone and 7.4 times that of black sandstone. b) With the increase of erosion time and erosion pressure, the erosion index of sandstone shows an increasing trend. However, in this study, there is an optimal standoff distance S/De = 4 to maximize the erosion depth of the sandstone. Again, there is an optimal standoff distance to maximize the erosion hole area, S/De = 10 for the red sandstone and white sandstone, and S/De = 6 for the black sandstone. c) The special phenomenon of the pressure difference formed after the collapse of the SOCW bubble in the submerged environment, which acts on the moisture content fine pore space inside the sandstone, the fine pore zone, was observed by scanning electron microscope (SEM). The microscopic characterization of the water wedge effect was observed by computed tomography (CT), and the trend of crack development is shown by the binarization processed images of the sandstone internal damage section. This result can be a theoretical basis to guide the working parameters of nozzles in deep sea mining, especially for the selection of standoff distance.

Experimental Investigation on the Granite Erosion Characteristics of a Variable Cross-Section Squeezed Pulsed Water Jet

The exploitation of deep resources and energy needs to break hard rock. Aiming at the problem of deep hard rock fragmentation, this paper proposes a variable cross-section squeezing pulsed water jet technology (SPWJ). SPWJ was generated under pump pressures of 5.2, 6.8, 8.5, 10, 11.9, and 13.8 MPa to carry out erosion experiments. Features such as rock spalling area, erosion depth, volume loss, and decomposition per unit inlet pressure are used to characterize the erosion performance of SPWJ. The results show that SPWJ can effectively crush granite under low input pressure. Granite crushing modes caused by SPWJ are mainly divided into three types: I: drilling type, II: erosion type, and III: cracking type. Compared with continuous water jet (CWJ), SPWJ has better overall erosion ability than CWJ when the erosion pressure is higher than 60 MPa, the dimensionless target distance is greater than 200, and the erosion time is less than 90 s. In addition, the erosion ability of SPWJ is better than that of CWJ under the condition of unit input pressure. The research results provide a reference for further optimizing the performance of SPWJ crushed granite in the future.

Unveiling the mechanics of lunar regolith erosion through analysis of CE-4 and CE-5 landing images and fluid simulation

During landing, the plume from the lander erodes the regolith on the lunar surface, thus destroying the nature of this surface. Landing also provides an opportunity to extract the mechanical properties of the lunar regolith in situ and to study wind erosion on airless bodies such as the Moon. Our goal in this study is to quantify the interparticle force of the lunar regolith, the erosion depth, and other parameters and to test the reliability of the plume erosion model. The erosion depth provides the necessary reference information for the precise interpretation of scientific results obtained from returned samples. We measure the total mass of the lunar regolith mobilized by the plume during the Moon landing. This information is also helpful for future lunar missions. With high-quality data from the Chang’E-5 (CE-5) and Chang’E-4 (CE-4) missions, we measure the erosion depth and the total mass and combine the results with computational fluid dynamics (CFD) to extract the interparticle force. We then test the plume erosion model according to the results from image measurement and CFD and propose a new formula with which to calculate the threshold friction velocity at which plume erosion is initiated. This calculation shows that the interparticle force for a 4-μm-diameter particle is 3.38–16.1 nN. The results also show that the CE-5 landing plume stripped away a 1.2-cm-deep layer of regolith, creating a ≈10-m-diameter crater on the lunar surface, and dispersed ≈441 kg of lunar regolith. Any analysis of a CE-5 drilling sample that is sensitive to the regolith depth must consider this 1.2-cm-thick eroded layer. When a plume erodes the lunar surface, the minimum shear stress required is much less than that predicted by the erosion model, which can no longer be used to predict whether erosion will occur.

Experimental investigation on sand bed scour by an oblique planar water jet at varying impinging angles

This study aims to investigate the effects of impinging angle of a planar water jet on the scour hole profiles and flow structure in the scour hole. Based on image recording and Particle Image Velocimetry (PIV) technology, the scour of the oblique planar impinging jet on erodible sand bed is investigated at different impinging angles over the range of 20° ≤ θ ≤ 80°. Time evolution of the scour hole profile was recorded using a video camera, and the flow fields in the scour hole at equilibrium state were measured using PIV. The results show that the normalized maximum dynamic erosion depth εm∞/h is a function of erosion parameter E = F0/h/B. The offset of impinging point on the sand bed from the geometric center is found to decrease with the increase in impinging angle. In addition, the jet width is larger at θ = 30° and 80° than that at θ = 50° for the same value of streamline-wise distance l/B. The present study could give some reference for engineering applications.

Research on Abrasive Water Jet Polishing of Silicon Carbide Based on Fluid Self-Excited Oscillation Pulse Characteristics

A self-excited oscillating pulsed abrasive water jet polishing method is proposed to solve the problems of low removal efficiency in traditional abrasive water jet polishing and the influence of an external flow field on the material surface removal rate. The self-excited oscillating chamber of the nozzle was used to generate pulsed water jets to reduce the impact of the jet stagnation zone on material surface removal and increase the jet speed to improve processing efficiency. ANSYS Fluent was employed to simulate the processing flow field characteristics for different lengths of oscillation cavities. The simulation results indicate that the velocity of the jet shaft reached a maximum of 178.26 m/s when the length of the oscillation cavity was 4 mm. The erosion rate of the material is linear with the processing angle. A nozzle with a length of 4 mm of the self-excited oscillating cavity was fabricated for SiC surface polishing experiments. The results were compared with those of ordinary abrasive water jet polishing. The experimental results showed that the self-excited oscillation pulse fluid enhanced the erosion ability of the abrasive water jet on the SiC surface and significantly improved the material-removal depth of the abrasive water jet polishing SiC. The maximum surface erosion depth can be increased by 26 μm.

The effect of Ni201 transition layer on the corrosion, wear and synergetic cavitation erosion-corrosion behavior of CMT-Monel K500 coating

The Monel K500 modified coating with Ni201 as the transition layer was prepared on the 304 stainless steel substrate by cold metal transfer (CMT) technology. Different from the Monel K500 coatings with direct deposition, the Ni201 transition layer can effectively block the diffusion of Fe and other elements in the substrate and avoid the deterioration of corrosion resistance of Monel K500 coating caused by galvanic corrosion in artificial seawater, which showed the highest polarization resistance and the strongest passivation tendency. In addition, the diffusion of Ni atoms in the transition layer compensated and stabilized the alloy element composition of the Monel K500 coating, making it have a finer microstructure and show higher microhardness and wear resistance. After 10 h- cavitation erosion (CE), the Monel K500 coating with transition layer showed the lowest mean depth erosion rates (MDER) of 2.2 ± 0.09 μm/h as it maintains the highest self-healing ability and integrity of passive film during the long-term synergistic effect of cavitation erosion and corrosion (SCEC). The introduce of the Ni201 transition layer can effectively improve the corrosion-cavitation and wear properties of CMT-Monel K500 surface modified coating, and then effectively prolong the service life of seawater overflow components such as butterfly valves, pump bodies, hydraulic turbines and heat exchangers, which has great application potential in the field of tribo-corrosion in ocean engineering.

Effect of Rifling Height on Convective Heat Transfer Flux and Erosion for Cannon Barrel

The effect of rifling height on erosion for cannon barrel was studied in this paper. An erosion velocity kernel function which is an Arrhenius type function revealing thermal and chemical effects is proposed. The erosion function is employed in numerical simulations to obtain the erosion depth after several rounds for two kinds of gun barrels at commencement of full rifling. By comparing final erosion depths obtained by numerical simulations and firing tests, it can be concluded that heat transfer flux between propellant gas and barrel with different rifles are absolutely different. Then the effect of rifle height on convective heat transfer flux is discussed in this paper.

Annual and decadal net morphological displacement of a small gravel‐bed channel

AbstractThe sediment supplied to a stream channel impacts the morphological trends experienced by that channel, and the long‐term trends are important to understand for many riverine applications. We introduce the term ‘net morphological displacement’ (NMD) to denote the net channel change revealed by the morphological method over multiple sediment transport events to make the concept more explicit for river management and use it to determine equilibrium or disequilibrium states. This study explores the morphological response of East Creek, a small threshold gravel‐bed channel in the Coast Mountains of British Columbia, Canada, to variations in flow and sediment supply at multiple spatial and temporal scales over 15 years. High‐resolution topographic data (HRTD) of the bed were combined with cross‐sectional surveys of the banks to determine the sediment supply that the channel responded to annually. The level of detection used to remove noise associated with HRTD was calibrated using an independent tracer stone dataset. The net effects from multiple floods caused distributions of bed elevation change to generally follow the log‐normal distribution, and mean depths of erosion and deposition were predominantly similar between morphological units. At the reach scale, the various reaches of East Creek responded differently to the same hydrological events due to the impacts from the varying supply conditions on the NMD. Shorter measurement periods would have resulted in inconclusive information that does not show the long‐term morphological trends of the channel. Determination of these trends can take years or decades, depending on the time and space scales of change, but there is generally a lack of long‐term channel monitoring programmes, notably after river restoration. More long‐term channel monitoring programmes are required to assess restoration projects and ensure their long‐term sustainability.

Sediment resuspension enhances nutrient exchange in intertidal mudflats

Intertidal coastal sediments are important centers for nutrient transformation, regeneration, and storage. Sediment resuspension, due to wave action or tidal currents, can induce nutrient release to the water column and fuel primary production. Storms and extreme weather events are expected to increase due to climate change in coastal areas, but little is known about their effect on nutrient release from coastal sediments. We have conducted in-situ sediment resuspension experiments, in which erosion was simulated by a stepwise increase in current velocities, while measuring nutrient uptake or release in field flumes positioned on intertidal areas of a tidal bay (Eastern Scheldt) and an estuary (Western Scheldt). In both systems, the water column concentration of ammonium (NH4+) and nitrite (NO2−) increased predictably with greater erosion as estimated from pore water dilution and erosion depth. In contrast, the phosphate (PO43−) dynamics were different between systems, and those of nitrate (NO3−) were small and variable. Notably, sediment resuspension caused a decrease in the overlying water PO43− concentration in the tidal bay, while an increase was observed in the estuarine sediments. Our observations showed that the concentration of PO43− in the water column was more intensely affected by resuspension than that of NH4+ and NO2−. The present study highlights the differential effect of sediment resuspension on nutrient exchange in two contrasting tidal coastal environments.

Experimental research on the erosion characteristics of organ-pipe cavitating jet for hydrate-bearing sediments

Cavitating jet is regarded as a promising breaking rate improvement technology in both the marine natural gas hydrate (NGH) fluidization exploitation method and the integrated radial jet drilling and completion method. Experimental studies on the influences of standoff distance, erosion time, inlet flow rate and hydrate saturation on hydrate-bearing sediments (HBS) breakage by organ-pipe cavitating jet (OPCJ) were conducted. The methane HBS synthesized in laboratory were employed as the experimental samples. The breaking effect were evaluated by four quantifiable indicators: erosion pit volume and maximum depth, and jet specific energy and specific cutting energy. Results show that under the same inlet flow rate, the standoff distance and erosion time have significant influences on the erosion pit shape. For the erosion pit volume and depth, the optimal standoff distances are respectively 4 mm and 5 mm (the diameter of nozzle is 1 mm), in which condition the OPCJ efficiencies of erosion and penetration on HBS are greatly improved. The ultimate erosion depth is 215 mm at an inlet flow rate of 0.085 L/s. The critical breaking velocities of OPCJ and conical jet (CJ) on HBS with hydrate saturation of 50% are respectively estimated to be 17.8 m/s and 24.2 m/s. Increasing hydrate saturation significantly decreases the erosion efficiency of OPCJ on HBS. The inlet flow rate is the most significant factor for the erosion pit volume and depth. This study provides a reference on the potential field applications for the NGH fluidization exploitation method and the integrated radial jet drilling and completion method.

Оценка критических границ компоновочных схем космических аппаратов по уровню теплового и эрозионного воздействий плазменных струй электроракетных двигателей

The paper proposes an engineering method to account for thermal and erosive effects of the electric rocket engine plasma jet on the spacecraft structural elements with the electric rocket engines installed on a spacecraft. The method is based on introducing the rejection boundaries that define the region of space, where installation of the spacecraft structural elements is unacceptable from the point of view of certain impact type. The rejection boundary is a surface, where the impact indicators are equal to the allowable value, inside the boundaries they exceed the allowable values (critical impact area), and outside the boundaries they stay below the allowable values (admissible impact area). If the spacecraft elements appear in the critical impact area, position of the electric rocket engines on the spacecraft should be corrected. Equilibrium surface temperature is the thermal effect indicator, which should not exceed the given allowable value; an erosion depth is the erosive effect indicator. Allowable level of erosive action depends on material and characteristics of the sprayed structural element. The considered indicators were determined by the ion current density at the given point in space for the worst case without accounting for the jet ions angle of incidence on the surface. Rejection boundaries were found for the plasma jet thermal and erosive effects of the SPT-100 stationary engine on various materials. It is shown that, incontrast to the traditionally used limitation on the jet divergence angle, the rejection boundary method makes it possible to significantly improve the accuracy of estimates and reduce the probability of errors in the layout of a modern spacecraft

Optimized design of the ion optics based on the over-perveance characteristics of the beam current

To illustrate the erosion mechanism of the edge aperture by high-energy ions, a three-dimension simulation model was established, and a particle-in-cell method was applied in tracking the hitting processes as well as a Monte Carlo collision method was used to deal with the particles’ collision. Numerical results showed that the potentials interacted among the sheaths of adjacent holes and the beam ions were over-focused in the accelerator gap, causing some ions to be intercepted on the downstream wall of the decelerator grid. This was a typical under-perveance characteristic of the beam current, operating at significantly less than the optimal perveance and corresponding to lower beam currents than optimal combination, which pushed the sheath to the left farther into the plasma. The farther the grid was, the more serious erosion patterns developed. In addition, the charge exchange ions were attracted and bombarded on the decelerator and the accelerator grids, respectively. The ion optics of the 30 cm ion thruster was optimized from four-zone to three-zone, where the plasma density upstream of the screen grid was increased by 1.5% and the perveance characteristics of the beam ions were improved such that many ions struck the edge hole. The background pressure was reduced from 3.0 × 10−3 to 8.0 × 10−4 Pa to decrease the erosion depths of the grids caused by the charge exchange ions, about 9.09% and two orders of magnitude, respectively, for the accelerator and decelerator grids.

Chloride Ion Corrosion Resistance of Innovative Self-Healing SMA Fiber-Reinforced Engineering Cementitious Composites under Dry-Wet Cycles for Ocean Structures

To evaluate the chloride ion corrosion resistance of proposed innovative self-healing concrete based on shape memory alloys (SMA) and engineering cementitious composites (ECC), a total of 2 kinds of 22 specimens were prepared. Chloride ion corrosion tests of self-healing SMA-ECC concrete under dry-wet cycles were carried out. It was found that the chloride ion erosion depths of SMA-ECC were significantly smaller than that of MC, and the growth rate of erosion depth of SMA-ECC was obviously smaller than that of MC after 15 dry-wet (dry and wet) corrosion cycles. The chloride ion content of SMA-ECC vanished at the erosion depth more than 10 mm, which was consistent with the test result of AgNO3 solution color-rendering test. Test results indicate that, compared to marine concrete (MC), SMA-ECC has a better chloride ion corrosion resistance behavior. Moreover, the chloride ion concentration of SMA-ECC at a chloride ion erosion depth of less than 10 mm decreased more significantly than that of MC, indicating that almost all chloride salt solution reacted in the outer layer of SMA-ECC, which is consistent with the conclusions of 4.1 and 4.2. Finally, based on the erosion distribution of chloride ions and Fick’s second law, a calculation model describing the relationship between the apparent chloride ion diffusion coefficient and the boundary condition of the chloride ion content was proposed.