Shear Stress Values Research Articles

Study of the Viscoelastic and Rheological Properties of Rubber-Bitumen Binders Obtained from Rubber Waste.

According to scientific research from different countries, crumb rubber obtained from end-of-life tires (ELT) during processing can improve the properties of the asphalt mixture, thereby extending the service life of the road surface. This paper presents the modification of bitumen with industrial rubber waste. The modification of bitumen for roads is considered one of the most suitable and popular approaches. This research paper describes the details of using different types of crumb rubber as bitumen modifiers. The modified bitumen's main physical and mechanical characteristics were determined after conventional tests: penetration and ductility, softening point, and Fraas brittleness point. In order to obtain a rubber-asphalt concrete mixture with improved performance characteristics, the viscoelastic and rheological properties of rubber-bitumen binders and their comparison with polymer-bitumen binders were also studied. The research results show that with increasing temperature, the values of viscosity, shear stress and complex shear modulus of all studied bitumen systems decrease, the values of the phase shift angle increase, and the size of the rubber particles has a greater influence on the properties of bitumen systems.

Frictional weakening leads to unconventional singularities during dynamic rupture propagation

Earthquakes i.e. frictional ruptures, are commonly described by singular solutions of shear crack motions. These solutions assume a square root singularity order around the rupture tip and a constant shear stress value behind it, implying scale-independent edge-localized energy. However, recent observations of large-scale thermal weakening accompanied by decreasing shear stress potentially affecting the singularity order can challenge this assumption. In this study, we replicate earthquakes in a laboratory setting by conducting stick-slip experiments on PMMA samples under normal stress ranging from 1 to 4 MPa. Strain gauges rosettes, located near the frictional interface, are used to analyze each rupture event, enabling the investigation of shear stress evolution, slip velocity, and material displacement as a function of distance from the rupture tip. Our analysis of the rupture dynamics provides compelling experimental evidence of frictional rupture driven by enhanced thermal weakening. The observed rupture fronts exhibit unconventional singularity orders and display slip-dependent breakdown work (on-fault dissipated energy). Moreover, these findings elucidate the challenges associated with a priori estimating the energy budget controlling the velocity and final extent of a seismic rupture, when thermal weakening is activated during seismic slip.

Experimental Analysis of Mechanical Behavior of Timber-Concrete Composite Beams with Different Connecting Systems

Timber-concrete composite structures are innovative structural systems which have become the subject of extensive research and practical usage, primarily due to their attractive mechanical properties. This article deals with the experimental procedure and the analysis of the mechanical behavior of two different series of timber-concrete composite beams with the same span and geometry of cross-sections. In the first BF-series, the screws were used as a connecting system between the timber and concrete parts, whereas in the BN-series the combination of notches and screws, as a more complex system, was used for the same purpose. Both series were exposed to loading up to a failure by means of the standard four-point bending test. The mechanical behavior of the BF and BN-series beams was analyzed by a comparative analysis referring to: the correlation of the failure loading and the deflection, mechanisms of failure, the strain development across the height of mid-span’s and support’s cross-sections, the horizontal displacement in the timber-concrete interlayer at the support zones, the value of shear stresses and the calculated values of the effective bending stiffness of the beams. The differences in bearing capacity between both series of beams were negligible (about 5%), the effective bending stiffness of BF beams is lower for 32.86% compared to the BN-series and the average value of deflections in BF-series beams is twice as high than in the BN-series. The BN-series beams showed better mechanical behavior in aspects of development of shear stresses in support zones, exhibiting lower shear stress values with an average of 40%.

Visualization of the Two-Phase Flow Behavior Involved in Enhanced Dense Phase Carbon Dioxide Pasteurization by Means of High-Speed Imaging

This research explores the two-phase flow behavior involved in enhanced dense phase carbon dioxide inactivation of E. coli DH5α, which has been shown to possess a high microbial reduction efficiency of up to 3.7 ± 0.4 log. We present an experiment in which the liquid sample was pressurized with liquid carbon dioxide to 8.2 MPa and, after saturation, was forced to flow through a mini tube. An experimental setup was developed to visualize the flow patterns (plug, slug and churn flows) occurring in the mini tube by means of high-speed imaging. The values of the wall shear stress were estimated within the mini tube with the help of the gas slug velocities (8–9 m/s) and were compared with threshold shear stress values reported for the disruption of fresh E. coli cells. The results suggest that the preliminary pressurization phase may cause a substantial destabilization of the cell wall of E. coli DH5α.

INVESTIGATION OF MODIFICATION OF PETROLEUM BITUMEN BY RUBBER WASTE

According to scientific research in different countries, rubber granules obtained from rubber waste during recycling can improve the properties of the asphalt mixture, thereby extending the service life of the road surface. This paper presents the modification of bitumen with industrial rubber waste. Modification of bitumen for roads is considered one of the most suitable and popular approaches. This research paper describes the details of using different types of rubber granules as bitumen modifiers. The main physical and mechanical characteristics of the modified bitumen were determined after conventional tests, penetration and ductility, softening point, Fraas brittleness point. In order to obtain a rubber-asphalt concrete mixture with improved performance characteristics, the viscoelastic and rheological properties of rubber-bitumen binders and their comparison with polymerbitumen binders were also studied. The research results show that with increasing temperature, the values of viscosity, shear stress and complex shear modulus of all studied bitumen systems decrease, and the values of the phase shift angle increase, and that the size of the rubber particles has a greater influence on the properties of bitumen systems.

Characteristics and Correlations of Wall Shear Stress and Flow Turbulence in the Carotid Bifurcation Evaluated Using an Ultrasound Vector Flow Imaging

Introduction: The aim of the study was to evaluate characteristics and provide the normal values of wall shear stress (WSS) and flow turbulence (Tur), and the relationship between them in the carotid bifurcation based on an ultrasound vector flow imaging (V Flow) in healthy adults. Methods: Max and mean WSS and Tur values at three segments (initial segments of internal and external carotid arteries [IICA and IECA]; distal segment of common carotid artery [DCCA]), both in anterior and posterior walls, were successfully obtained in 56 healthy adults, using ultrasound V Flow function. Relationship between mean WSS and Tur was further explored. Results: The mean WSS value was 0.71 Pa, 0.86 Pa, and 0.96 Pa at IICA, IECA, and DCCA, respectively (IICA < IECA < DCCA, p < 0.05). The mean Tur value was 13.85%, 5.46%, and 4.17% at IICA, IECA, and DCCA, respectively (IICA > IECA > DCCA, p < 0.05). A cutoff value (WSS = 0.4 Pa) was selected and Tur values were significantly higher in group with WSS cutoff value <0.4 Pa than group with WSS cutoff value ≥0.4 Pa (p < 0.01). Conclusion: WSS and Tur are moderately negatively correlated, which can be used in the quantitative evaluation of carotid bifurcation and could be a potential dual-parameter tool in the clinical research for early detection of carotid atherosclerosis.

Local strength of bainitic and ferritic HSLA steel constituents understood using correlative electron microscopy and microcompression testing

HSLA steels with different polygonal ferrite and granular bainite contents resulting from two different cooling rates were investigated. Micropillar compression tests, electron channeling contrast imaging (ECCI) and electron backscatter diffraction (EBSD) experiments were performed to reveal microscopic strength differences and their origin. The obtained results indicate that a higher cooling rate caused a smaller granular bainite substructure size and a higher dislocation density for both ferrite and bainite. In addition, the critical resolved shear stress (CRSS) values for both phases were found to be higher for the faster cooling process. This is ascribed to the increased dislocation density for faster cooling rather than the grain size as will be discussed in the manuscript. Interestingly, the macroscopic yield strength can be closely estimated by the CRSS obtained from micropillar compression considering the corresponding phase fractions. The achieved results can be used in future as input variables for crystal plasticity models.

Transient 3D hydrodynamic model of a blast furnace main trough

A transient 3D CFD model is solved to investigate the features of the complex flow in a blast furnace trough. Hot metal, slag, and air are considered as different phases of the flow. The influence of various taphole stream conditions on the hydrodynamics in the trough is examined, such as different slag-hot metal ratios, taphole diameters, and stream velocities. The special case of a dry trough during its first tapping is also addressed. Attention is devoted to the characterization of the wall shear stress, closely related to mechanical erosion, and to the evolution of the interfaces separating the fluid phases. Intricate flow patterns, characterized by large recirculations and return currents of both slag and hot metal, are observed. The simultaneous tapping of slag and hot metal leads to distinct flow features, deviating from the initial stage, when only hot metal is drained, as well as lower shear stress values, up to 31% less with increasing slag content in the taphole stream. Slag and hot metal levels in the trough evolve rapidly to quasi-steady states. Although the influence of the taphole stream velocity and diameter have a modest impact on the free surface dynamics, variations in the taphole slag fraction lead to significant fluctuations in the depth of slag and hot metal pools in the trough. The height of the slag-iron free surface can increase by up to 40% relative to its initial level, while the variation in the slag pool depth approaches 30%. These changes in the interface positions carry potential implications for refractory wear, as they suggest a substantial shift of the slag-hot metal line during each tapping.

Evaluation of Shear Stress in Soils Stabilized with Biofuel Co-Products via Regression Analysis Methods

In recent years, the employment of artificial neural networks (ANNs) has risen in various engineering fields. ANNs have been applied to a range of geotechnical engineering problems and have shown promising outcomes. The aim of this article is to enhance the effectiveness of estimating unfamiliar intermediate values from existing shear stress data by employing ANNs. Artificial neural network modelling was undertaken through the Regression Learner program that is integrated with the Matlab 2023a software package. This program offers a user-friendly graphical interface for developing AI models absent of the need for any coding. The validation and training of the ANNs were executed by relying on shear box test data which had been conducted at the Geotechnical Laboratory situated at Iowa State University. The objective of these experiments was to explore the potential of biofuel co-products (BCPs) in soil stabilization. The data should be structured with input and output parameters in columns and samples in rows. The dataset comprises a 216 × 6 matrix. The data columns provide information on soil type (pure soil—unadulterated; and 12% BCP-adulterated soil), time (1, 7, and 28 days), normal stress (0.069-DS10, 0.138-DS20, and 0.207-DS30 MPa), moisture content (OMC−4%, OMC%, and OMC+4%), and corresponding shear stress (σ, MPa) values. The AI predictions for the test data output provide an outstanding R2 score of 0.94. This indicates that employing ANN to teach shear test data facilitates gaining a large quantity of data more efficiently, with fewer experiments and in less time. Such an approach seems encouraging for geotechnical engineering.

Paleo sea-level indicators and proxies from Greenland in the GAPSLIP database and comparison with modelled sea level from the PaleoMIST ice-sheet reconstruction

One of the most common ways to assess ice-sheet reconstructions of the past is to evaluate how they impact changes in sea level through glacial isostatic adjustment. PaleoMIST 1.0, a preliminary reconstruction of topography and ice sheets during the past 80 000 years, was created without a rigorous comparison with past sea-level indicators and proxies in Greenland. The basal shear stress values for the Greenland ice sheet were deduced from the present day ice-sheet configuration, which were used for the entire 80 000 years without modification. The margin chronology was based on previous reconstructions and interpolation between them. As a result, it was not known if the Greenland component was representative of its ice-sheet history. In this study, I compile sea–level proxy data into the Global Archive of Paleo Sea Level Indicators and Proxies (GAPSLIP) database and use them to evaluate the PaleoMIST 1.0 reconstruction. The Last Glacial Maximum (c.20 000 years before present) contribution to sea level in PaleoMIST 1.0 is about 3.5 m, intermediate of other reconstructions of the Greenland ice sheet. The results of the data-model comparison show that PaleoMIST requires a larger pre-Holocene ice volume than it currently has to match the sea-level highstands observed around Greenland, especially in southern Greenland. Some of this mismatch is likely because of the crude 2500 year time step used in the margin reconstruction and the limited Last Glacial Maximum extent. Much of the mismatch can also be mitigated if different Earth model structures, particularly a thinner lithosphere, are assumed. Additional ice in Greenland would contribute to increasing the 3–5 m mismatch between the modelled far-field sea level at the Last Glacial Maximum and proxies in PaleoMIST 1.0.

Comparative Study of Membrane Fouling with Aeration Shear Stress in Filtration of Different Substances.

The formation process of membrane fouling is complex and diverse, which is an important problem that needs to be overcome in membrane applications. In this paper, three foulant systems consisting of humic acid, humic acid plus Ca2+ and humic acid plus Ca2+ plus yeast were selected to compare membrane fouling processes with different aeration intensities. The aim was to establish the quantitative relationship between membrane fouling rate and shear stress, respectively, in a large-scale flat sheet MBR (FSMBR). The shear stress values at different aeration intensities were obtained using computational fluid dynamics (CFD). The membrane fouling rate during the filtration of different substances was measured by performing experiments. The comparison results showed that the membrane fouling rate varied greatly during the filtration of different substances. With the help of particle size distribution, the effect of different shear forces on floc size was further explored. Using the dual control of fouling rate and floc size, the recommended aeration intensity was 6~8 L/(m2·min).

A method for determining the rheological properties of viscoplastic fluids using a rectangular die

This study introduces a method for determining the rheological parameters of viscoplastic fluids with the use of rectangular dies. The relationship between the wall shear rate and the wall shear stress is investigated for the Casson, Herschel-Bulkley, and Robertson-Stiff rheological models, using two geometric constants for non-circular dies with a regular cross-section. Then, the rheological behavior and parameters of a collagen material were examined by an analytical method and by the proposed approximate method, using experimental data obtained by a slit viscometer and a rectangular die. The yield stress value of the collagen was determined employing the pressure relaxation method. The values were 2940 (±209) Pa from the slit viscometer and 3100 Pa (± 200) Pa from the rectangular die. The rheological parameters of collagen were then obtained using the analytical method and the proposed approximate methods for Casson, Herschel-Bulkley, and Robertson-Stiff rheological models. It was shown that the wall shear rate and the wall shear stress values of the analytical method and the proposed method are in good agreement. It was found that the Herschel-Bulkley and Robertson-Stiff models successfully fitted the wall shear rate-wall shear stress curves with a coefficient of determination equal to or greater than 0.97, and the evaluated consistency values were 165 (±71) Pa.sn for the Herschel-Bulkley model and 947 (±225) Pa.sn for the Robertson-Stiff model, and the flow index values were found to be 0.50 (±0.06) for the Herschel-Bulkley model and 0.32 (±0.03) for the Robertson-Stiff model. However, it was shown that the Casson model is not suitable for describing the rheological characteristic of collagen material. Experimentally obtained parameters for the Herschel-Bulkley model were validated with the use of simulations, and it was found that the numerically and experimentally evaluated results showed good agreement. The maximum deviation was found to be less than 12%.

Atherosclerosis risk assessment in human carotid artery with variation in sinus length: a numerical approach

The mortality rates due to cardiovascular diseases are on a rise globally. One of the major cardiovascular diseases is stroke which occurs due to atherosclerotic plaques build-up in the carotid artery. The common carotid artery (CCA) bifurcates into the internal carotid artery (ICA) and external carotid artery (ECA). Sinus present at ICA is an ellipsoidal-shaped dilated region acting as a pressure receptor and blood flow regulator. Dimensions of the sinus vary from person to person, affecting the hemodynamics of the carotid artery. The current numerical study manifests a 3D flow analysis by varying the sinus length to investigate its local and global effects on the hemodynamics of the carotid artery using various biomechanical risk analysis parameters of atherosclerosis. User-defined function (UDF) dictates the pulsatile flow velocity profile imposed at the inlet. Near the outer wall (OW) of the sinus, the blood flow velocities are lower and recirculation zones are more. Though the recirculation zones for shorter sinus will be close to the inner wall (IW), interestingly, with an increase in the sinus length, the recirculation zones shift toward the OW with higher strength. These significantly decrease the x-wall shear stress (x-WSS) and time-averaged wall shear stress (TAWSS) values on the OW of the longer sinus. The other risk analysis parameters, like oscillatory shear index (OSI) and relative residence time (RRT), support the described consequences. These results reveal that sinus of increased length is more prone to developing atherosclerotic plaque.

Utilization of an Artery-on-a-Chip to Unravel Novel Regulators and Therapeutic Targets in Vascular Diseases.

In this study, organ-on-chip technology is used to develop an in vitro model of medium-to-large size arteries, the artery-on-a-chip (AoC), with the objective to recapitulate the structure of the arterial wall and the relevant hemodynamic forces affecting luminal cells. AoCs exposed either to in vivo-like shear stress values or kept in static conditions are assessed to generate a panel of novel genes modulated by shear stress. Considering the crucial role played by shear stress alterations in carotid arteries affected by atherosclerosis (CAD) and abdominal aortic aneurysms (AAA) disease development/progression, a patient cohort of hemodynamically relevant specimens is utilized, consisting of diseased and non-diseased (internal control) vessel regions from the same patient. Genes activated by shear stress follow the same expression pattern in non-diseased segments of human vessels. Single cell RNA sequencing (scRNA-seq) enables to discriminate the unique cell subpopulations between non-diseased and diseased vessel portions, revealing an enrichment of flow activated genes in structural cells originating from non-diseased specimens. Furthermore, the AoC served as a platform for drug-testing. It reproduced the effects of a therapeutic agent (lenvatinib) previously used in preclinical AAA studies, therefore extending the understanding of its therapeutic effect through a multicellular structure.

Assessment of biomechanical behavior of immature non-vital incisors with various treatment modalities by means of three-dimensional quasi–static finite element analysis

The objectives of this study were to evaluate the stress distribution and risk of fracture of a non-vital immature maxillary central incisor subjected to various clinical procedures using finite element analysis (FEA). A three-dimensional model of an immature central incisor was developed, from which six main models were designed: untreated immature tooth (C), standard apical plug (AP), resin composite (RC), glass-fibre post (GFP), regeneration procedure (RET), and regeneration with induced root maturation (RRM). Mineral trioxide aggregate (MTA) or Biodentine® were used as an apical or coronal plug. All models simulated masticatory forces in a quasi–static approach with an oblique force of 240 Newton at a 120° to the longitudinal tooth axis. The maximum principal stress, maximum shear stress, risk of fracture, and the strengthening percentage were evaluated. The mean maximum principal stress values were highest in model C [90.3 MPa (SD = 4.4)] and lowest in the GFP models treated with either MTA and Biodentine®; 64.1 (SD = 1.7) and 64.0 (SD = 1.6) MPa, respectively. Regarding the shear stress values, the dentine tooth structure in model C [14.4 MPa (SD = 0.8)] and GFP models [15.4 MPa (SD = 1.1)] reported significantly higher maximum shear stress values compared to other tested models (p < 0.001), while no significant differences were reported between the other models (p > 0.05). No significant differences between MTA and Biodentine® regarding maximum principal stress and maximum shear stress values for each tested model (p > 0.05). A maximum strain value of 4.07E−03 and maximum displacement magnitude of 0.128 mm was recorded in model C. In terms of strengthening percentage, the GFP models were associated with the highest increase (22%). The use of a GFP improved the biomechanical performance and resulted in a lower risk of fracture of a non-vital immature maxillary central incisor in a FEA model.

Исследование реологических характеристик рыбного фарша из объектов аквакультуры

The paper dwells on the prospects of using the methods of extrusion processing of products based on minced fish. It is noted that one of the promising methods is the method of cold extrusion and co-extrusion. The research aims to identify theoretical and experimental patterns of changes in the rheological characteristics of minced aquaculture fish (carp and silver carp) and analyze them in relation to extrusion processes. The dependences of the rheological characteristics of minced fish samples on the influencing parameters in a wide temperature range from –5 to +25 °C have been studied. The values of the ultimate shear stress and the penetration depth of minced fish have been determined on a conical plastometer KP-3, viscosity – on a rotational viscometer Brookfield DV–II+Pro, and adhesive ability – on a laboratory unit for determining the stickiness of the material. Based on the data of minced fish chemical composition theoretical dependences of the effective viscosity on the shear rate gradient have been obtained. Similar dependences have been obtained experimentally in a wide temperature range. The analysis of these dependencies has shown their qualitative coincidence for the usual conditions for producing minced fish, but there are quantitative differences due to the technology for preparing minced aquaculture fish. The rheological characteristics of minced fish have been analyzed for the studied temperature range. It has been determined that the temperature range from –2.5 to 0 °C is the most appropriate for cold extrusion processes. In this area the value of the effective viscosity of minced fish and its adhesive ability are minimal, which is decisive for implementing extrusion processing. The good formability of the product has also been noted under these conditions. A further research direction is to identify the influence of technological additives on the formability of minced aquaculture fish, to reduce the smell of fish, and to eliminate undesirable oxidative processes. Developing new types of fish products with innovations in form, texture, colour and composition remains relevant. The prospects of the co-extrusion method which allows creating new innovative fish products with functional properties have been confirmed.

Numerical study on the role of ternary nanoparticles on heat transfer enhancement in MHD flow of cross-rheological-fluid

The heat transfer in the fluids over a disk occurs in several industrial applications. Thermal and cooling systems, spray coating, heat exchangers, and automobiles are sectors where heat transfer is encountered. In view of these applications, the present investigation is carried out. Therefore, the theoretical study related to heat transfer enhancement has significance. The governing laws are used to formulate the problems. For numerical formulations, the finite element method (FEM) is used. This method has proven to be a very good numerical scheme for complex models, along with complex mathematical corelations for involved thermo-physical properties. Accuracy and convergence are ensured, and mesh-free analysis is performed. The present results for their special case are compared with published data, and an excellent agreement is found between the present results and already published data. Hence, authenticity is ensured. The strongest effects of shear rate-dependent viscosity in the case of ternary nanofluids are seen. The highest wall heat flux is noticed in the case of a ternary nanofluid. The viscous dissipation results in a remarkable decrease in the wall heat flux. The highest viscous dissipation is noticed in the case of ternary nanofluids. The ternary nanofluid generates the most heat when it is subjected to thermal changes. However, the fluid with a single type of nanoparticles generates the least heat. The strongest effects of shear rate-dependent viscosity in the case of ternary nanofluids are seen. The viscous dissipation results in a remarkable decrease in the wall heat flux. Thus, the fluid should be less viscous and dissipative if the highest wall heat flux is required in any industrial application. The highest wall shear stress is noticed in the case of ternary nanofluids, whereas the smallest values of wall shear stress are noted in the case of monofluids. Therefore, sufficient strength of the wall over which ternary nanofluid flows should be ensured in order to avoid failure or breakage of the setup where ternary nanofluid is used.

Radiating and electromagnetic nanofluids flow over an exponentially accelerated Riga plate with heat sink

In current history, there has been a significant interest in contemporary nanostructures for nanoelectronic systems. These systems progressively employ dynamic media to boost efficiency. Inspired by its applications in engineering, The effect of radiation and heat sink on electromagnetic nanofluids flow past an exponentially accelerated Riga surface is studied analytically using the Laplace transform technique. The base fluid is water, and three selected nanoparticles are used: Copper, Titanium dioxide, and Aluminium oxide. The porous medium is taken into account, as well as the validity of the Boussinesq approximation. The influence of modified Hartmann number, heat absorption, Grashof number, and thermal radiation parameter on nanofluid velocity and temperature profiles is depicted graphically and discussed. The shear stress and Nusselt number are determined, and outcomes are presented via plots and a table. The exact solution shows that the modified Hartmann number, nanofluid volume fraction and heat sink tend to improve as the values of Shear stress (skin friction) for Cu – water nanofluid shows a comparative increase over Al2O3 and TiO2 nanofluids. Whereas the Radiation effect tends to decrease as the shear stress values for Cu–water nanofluids show a higher decline over Al2O3 and TiO2 nanofluids.

A promising protocol for the endothelialization of vascular grafts in an instrumented rotating bioreactor towards clinical application

Pre-endothelialization of a tissue-engineered vascular graft before implantation aims to prevent thrombosis and immunoreactions. This work demonstrates a standardized cultivation process to build a confluent monolayer with human aortal endothelial cells on xenogenous scaffolds. Pre-tested dynamic cultivation conditions in flow slides with pulsatile flow (1 Hz) representing arterial wall conditions were transferred to a newly designed multi-featured rotational bioreactor system. The medium was thickened with 1% methyl cellulose simulating a non-Newtonian fluid comparable to blood. Computational fluid dynamics was used to estimate the optimal volume flow and medium distribution inside the bioreactor chamber for defined wall-near shear stress levels. Flow measurements were performed during cultivation for constant monitoring of the process. Three decellularized porcine arteries were seeded and cultivated in the bioreactor over six days. 1% MC turned out to be the optimal percentage to achieve shear stress values ranging up to 10 dyn/cm2. Vascular endothelial cells formed a continuous monolayer with significant cell alignment in the direction of flow. The presented cultivation protocol in the bioreactor system thus displays a promising template for graft endothelialization and cultivation. Therefore, establishing a key step for future tissue-engineered vascular graft development with a view towards clinical application.

Field simulation experiment on the relationships between hydrodynamics and soil detachment rate in formed rills

The dynamics of rill erosion are crucial for accurate modelling of soil erosion and vary across rill development stages. Research has largely concentrated on the rill formation process, with limited insights into formed rills under field conditions. Given the importance of soil detachment rate in the intensity and dynamics of soil erosion, this study aims to investigate the correlations between the soil detachment rate and hydrodynamic parameters in formed rills through field experiments. Therefore, the objective of this study was to explore the relationships between hydrodynamic parameters and the soil detachment rate of formed rills through field scouring experiments. The experiments were conducted on formed rills with flow discharges of 6, 9, 12, 15, 18, and 21 L·min−1 in a field runoff plot (with length of 18, width of 1 m, and slope gradient of 17.5 %). The results showed that the soil detachment rate remained stable fluctuations over time under different flow discharges. The rill flow velocity varied from 0.191 to 0.301 m·s−1, and increased with the increase of flow discharge. Except for the low-flow discharge (6 and 9 L·min−1), the rill flows manifested as super-critical turbulent flow. The values of flow shear stress, stream power, unit stream power, and unit energy were within the scope of 8.776–12.517 Pa, 1.647–3.757 W·m−2, 0.033–0.052 m·s−1 and 0.007–0.013 m, respectively. The soil detachment rate was significantly negatively correlated with Darcy–Weisbach friction, whereas demonstrated a significant positive correlation with Reynolds number and stream power. The soil detachment rate of formed rills was accurately predicted by flow stream power using a linear function (R2 = 0.918). The results of this study provided insights into hydrodynamics and soil detachment rate of purple soil under natural rainfall conditions.