Search Results (43)

This study experimentally examines turbulent flow structures induced by the coupled interaction of transverse bank slope, rigid vegetation, and bed roughness heterogeneity in a compound channel. Three-dimensional velocity components were measured using Acoustic Doppler Velocimetry (ADV) in a 13 m long flume under three transverse bank slopes (0°, 10°, and 25°), both with and without submerged rigid vegetation. Quantitatively, the presence of vegetation on the sloped bank reduced local flow velocity by 40–50% due to drag caused by vegetation canopy, while the accelerating flow in the main channel reduced by 25–35%. The combined effect of a steep 25° slope and vegetation amplified the turbulent kinetic energy (TKE) by ~55% and maximum Reynolds shear stress (RSS) by 50–70% at the sand–gravel interface compared to bare-bed conditions, generating a rigorous lateral shear layer. These quantitative insights provide critical design guidance for river restoration, bank protection, and flood management. The identified interactions between bank slope and vegetation establish a predictive framework for mitigating localized scour and bank erosion while optimizing channel conveyance capacity in ecologically managed river systems. Full article

The present study investigates how bed roughness affects the velocity field in a laboratory water channel designed for testing hydrokinetic turbines. The main aim is to evaluate the impact of bed morphology on flow hydrodynamics and, consequently, on the turbines’ operating conditions. Experimental studies were carried out in two hydraulic regimes—smooth channel bed and bed with artificially created irregularities—at flow velocities of 0.3 and 0.4 m/s, with a depth of 180 mm. The results indicate that bed roughness significantly affects the velocity field, leading to increased turbulent fluctuations, the formation of vortex structures, and momentum redistribution. There is also localized velocity acceleration within the measurement region caused by local acceleration between the bed irregularities, which is influenced by the geometry of the water channel. A clear vertical velocity distribution is established, with larger fluctuations being registered in the surface layer, while near the channel bed, the flow is more stable. The results obtained emphasize the importance of bed roughness as a key factor in laboratory modeling and analysis of hydrokinetic turbine performance, with a direct impact on their efficiency and load. Full article

This paper presents a reproducible simulation benchmark for rough surface interferometric profilometry. The benchmark compares three complete reconstruction pipelines under matched detected count assumptions: classical four-step phase-shifting interferometry (PSI), direct coincidence proxy reconstruction, and hybrid coarse-to-fine reconstruction in which a coincidence-derived observable supplies the coarse fringe-order prior. Fifty-nine focus variation (FV) topographies exported as Mountains/DigitalSurf .sur files (Digital Surf, Besancon, France) provide a shared FV prior for simulated optical observations. The coincidence channel is a simulation proxy rather than a validated quantum hardware implementation. The main result is architectural role separation. On the measured surface benchmark, the hybrid branch gives the lowest median detrended height RMSE (314.0 nm) and wins on 32 of 59 surfaces. The same ordering is retained in a rate-based coincidence control, with median hybrid RMSE of 290.9 nm under ideal matched-count rates and 376.3 nm under detector non-idealities. Roughness endpoints define the boundary of this result: hybrid gives the lowest matched bandwidth $S_a$ and $S_q$ errors, whereas direct coincidence proxy reconstruction is selectively strongest for $S_z$ and remains process-dependent. Classical two-colour and classical frontier controls show that following the broad long-wavelength envelope is not sufficient evidence for overall architecture-level superiority within this simulation benchmark. The benchmark identifies coincidence-derived information as most useful when used as a coarse prior inside a hybrid estimator, while final fine texture remains anchored by short-wavelength PSI. Full article

In MOSFETs, mobility enhancement is a key factor for improving the electrical performance and enabling their use in new applications, such as low-power, digital, and medical applications. This mobility improvement can be technically achieved by using different techniques that exploit the complex behavior of mobility (Coulomb, phonon, and surface roughness mobilities). Previous reviews have primarily focused on two main technologies: the introduction of mechanical stress and crystallographic orientation. Therefore, this review summarizes all key techniques that can enhance mobility, and each of these techniques is linked to a physical origin. Mechanical stress notably affects phonon mobility, whereas silicon thickness and channel impurities mainly affect the Coulomb mobility. Moreover, the dielectric oxide type, heat treatments, surface cleaning, ionic implantation in the oxide, and oxynitrides affect surface roughness mobility. In addition, the crystallographic orientation affects Coulomb, phonon, and surface roughness mobilities. Furthermore, the study of the series resistance engineering also affects the performance. Therefore, the simultaneous use of multiple of these techniques leads to an enhancement of the effective mobility at low, medium, and high effective electric fields, and the combined effect results in a more significant mobility increase. Full article

Hydrodynamic models of river networks are commonly used for flood disaster simulation, and the accuracy of model parameter settings directly affects the reliability of simulation results. Among these, Manning’s roughness coefficient is the core parameter for calibrating one-dimensional(1D) hydrodynamic models, as it is the most sensitive and frequently adjusted parameter. Taking the Yunxi Area of Huai’an City as a case study, this paper proposes an integrated workflow using orthogonal experiments and successive approximation for calibrating Manning’s roughness coefficients in river networks. In this workflow, 13 river reaches (from six major rivers) serve as experimental factors. The Manning’s roughness coefficients for the main channel and floodplains are assigned different values as experimental levels. Model performance is evaluated using the Nash–Sutcliffe Efficiency (NSE) and Root Mean Square Error (RMSE). A multi-factor and multi-level orthogonal table L₂₇(3¹³) of main channel or floodplains roughness is alternately selected to design 27 sets of experiments. Through HEC-RAS simulation and orthogonal analysis, the roughness coefficients of the main channel and floodplains are alternately screened and successively approximated to the target values. Finally, the roughness coefficients of the main channel and floodplains for each river reach meeting the accuracy requirements are obtained, with corresponding values of NSE = 0.93 and RMSE = 0.04 m. The results show that orthogonal experimental design significantly reduces the number of simulation tests and effectively saves computational time and costs, while the successive approximation strategy addresses the complexity of solving problems with multiple decision variables. Additionally, the experimental factors consider variations in cross-section types and hydraulic conditions along the river by setting roughness coefficients in segments. The orthogonal experimental design ensures the relevance, simultaneity, and systematic nature of parameter adjustments across all river reaches, significantly enhancing the rationality and reliability of the model parameter calibration. Full article

Floods are among the most frequent and destructive natural hazards worldwide, with increasingly severe socioeconomic consequences due to rapid urbanization, land use changes, and climate variability. While the combination of Geographic Information Systems (GIS) with models such as HEC-RAS has been extensively explored for flood risk management, many existing studies remain limited to one-dimensional (1D) models or use coarse-resolution terrain data, often underestimating flood risk and failing to produce critical multivariate flood characteristics in densely built urban areas. This study applies a two-dimensional (2D) hydraulic modeling framework in HEC-RAS combined with GIS-based spatial analysis, using a high-resolution (1 × 1 m) LiDAR-derived Digital Terrain Model (DTM) and a hybrid mesh refined between 2 × 2 m and 8 × 8 m, with the main contributions represented by the specific application context and methodological choices. A key methodological aspect is the direct integration of synthetic hydrographs with defined exceedance probabilities (10%, 1%, and 0.1%) into the 2D model, thereby reducing the need for extensive hydrological simulations and defining a data-driven approach for resource-constrained environments. The primary novelty is the application of this high-resolution urban modeling framework to a Romanian urban–peri-urban setting, where detailed hydrological observations are scarce. Unlike previous studies in Romania, this approach applies detailed channel and floodplain discretization at high spatial resolution, explicitly incorporating anthropogenic features like buildings and detailed land use roughness for the accurate representation of local hydraulic dynamics. The resulting outputs (inundation extents, depths, and velocities) support risk assessment and spatial planning in the Ungheni locality (Iași County, Romania), providing a practical, transferable workflow adapted to data-scarce regions. Scenario results quantify vulnerability: for the 0.1% exceedance probability scenario (with a calibration accuracy of ±15–30 min deviation for peak flow timing), the flood risk may affect 882 buildings, 42 land parcels, and 13.5 km of infrastructure. This framework contributes to evidence-based decision-making for climate adaptation and disaster risk reduction strategies, improving urban resilience. Full article

Aluminum alloy surface microstructures possess functional characteristics such as hydrophilicity/hydrophobicity and anti-icing and have important applications in fields such as aerospace and power systems. In order to improve the filling quality of the microstructure and verify the anti-icing property of the microstructure, this work develops a scheme for achieving large-area hot embossing of anti-icing functional microstructures based on a multi-arc ion-plating mold. Compared with conventional steel, the hardness of the PVD-coated steel increases by 44.7%, the friction coefficient decreases by 66.2%, and the wear resistance is significantly enhanced. The PVD-coated punch-assisted embossing could significantly improve filling properties. While the embossing temperature is 300 °C, the PVD-coated punch-assisted embossing can ensure the complete filling of the micro-array channels. In contrast, under-filling defects occur in conventional hot embossing. Then, a large-area micro-channel specimen of 100 cm² was precisely formed without warping, and the average surface roughness Ra was better than 0.8 µm. The maximum freezing fraction of the micro-array channel was reduced by about 53.2% compared with the planar, and the complete freezing time was delayed by 193.3%. The main reason is that the air layer trapped by the hydrophobic structures hinders heat loss at the solid–liquid interface. Full article

Utilizing a coupled Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) approach, this study constructs a comprehensive three-dimensional numerical model to simulate particle migration dynamics within rough artificial fractures subjected to the high-energy impact of water inrush. The model explicitly incorporates key governing factors, including intricate fracture wall geometry characterized by the joint roughness coefficient (JRC) and aperture variation, hydraulic pressure gradients representative of inrush events, and polydisperse sand particle sizes. Sophisticated simulations track the complete mobilization, subsequent acceleration, and sustained transport of sand particles driven by the powerful high-pressure flow. The results demonstrate that particle migration trajectories undergo a distinct three-phase kinetic evolution: initial acceleration, intermediate coordination, and final attenuation. This evolution is critically governed by the complex interplay of hydrodynamic shear stress exerted by the fluid flow, frictional resistance at the fracture walls, and dynamic interactions (collisions, contacts) between individual particles. Sensitivity analyses reveal that parameters like fracture roughness exert significant nonlinear control on transport efficiency, with an identified optimal JRC range (14–16) promoting the most effective particle transit. Hydraulic pressure and mean aperture size also exhibit strong, nonlinear regulatory influences. Particle transport manifests through characteristic collective migration patterns, including “overall bulk progression”, processes of “fragmentation followed by reaggregation”, and distinctive “center-stretch-edge-retention” formation. Simultaneously, specific behaviors for individual particles are categorized as navigating the “main shear channel”, experiencing “boundary-disturbance drift”, or becoming trapped as “wall-adhered obstructed” particles. Crucially, a robust multivariate regression model is formulated, integrating these key parameter effects, to quantitatively predict the critical migration time required for 80% of the total particle mass to transit the fracture. This investigation provides fundamental mechanistic insights into the particle–fluid dynamics underpinning hazardous water–sand inrush phenomena, offering valuable theoretical underpinnings for risk assessment and mitigation strategies in deep underground engineering operations. Full article

In recent years, the application of microfluidic devices has increased, and three-dimensional (3D) printers for fabricating microdevices could be considered a suitable technique but, in some cases, may confront some issues. The main issues include channel roughness values, print orientation due to the 3D printer’s setup, filament materials, nozzle specifications, and condition. This study aims to analyze the capillary-driven flow in microdevices produced by 3D printers. Therefore, four 3D printer-based microchannels were investigated, and the capillary-driven flow of five liquids with different viscosities and contact angles was evaluated experimentally. The experimental results were compared with theoretical calculations using the Lucas−Washburn equation, and the impact of the width, length, and closed and open microchannel on flow behaviors was explored. The experimental results showed that the peak velocity for open and closed microchannels decreases with the length. Moreover, there were differences in flow behavior between open and closed microchannels. For the former, the maximum average velocity appeared in the microchannel with a width of 400 μm, while for the latter, it was for a width of 1000 μm. In addition, the flow velocity decreased when the viscosity increased, regardless of microchannel width. The decrease was more pronounced for the lower-viscosity liquids (ethanol and water) and smaller for the higher-viscosity ones (coffee and olive oil). Finally, the advantages and challenges of 3D printer-based microdevices are presented. Full article

Accurate river hydraulic characterization is fundamental to assess flood risk, parametrize flood forecasting models, and develop river maintenance workflows. River hydraulic roughness and riverbed/floodplain geometry are the main factors controlling inundation extent and water levels. However, gauging stations providing hydrometric observations are declining worldwide, and they provide point measurements only. To describe hydraulic processes, spatially distributed data are required. In situ surveys are costly and time-consuming, and they are sometimes limited by local accessibility conditions. Satellite earth observation (EO) techniques can be used to measure spatially distributed hydrometric variables, reducing the time and cost of traditional surveys. Satellite EO provides high temporal and spatial frequency, but it can only measure large rivers (wider than ca. 50 m) and only provides water surface elevation (WSE), water surface slope (WSS), and surface water width data. UAS hydrometry can provide WSE, WSS, water surface velocity and riverbed geometry at a high spatial resolution, making it suitable for rivers of all sizes. The use of UAS hydrometry can enhance river management, with cost-effective surveys offering large coverage and high-resolution data, which are fundamental in flood risk assessment, especially in areas that difficult to access. In this study, we proposed a combination of UAS hydrometry techniques to fully characterize the hydraulic parameters of a river. The land elevation adjacent to the river channel was measured with LiDAR, the riverbed elevation was measured with a sonar payload, and the WSE was measured with a UAS radar altimetry payload. The survey provided 57 river cross-sections with riverbed elevation, and 8 km of WSE and land elevation and took around 2 days of survey work in the field. Simulated WSE values were compared to radar altimetry observations to fit hydraulic roughness, which cannot be directly observed. The riverbed elevation cross-sections have an average error of 32 cm relative to RTK GNSS ground-truth measurements. This error was a consequence of the dense vegetation on land that prevents the LiDAR signal from reaching the ground and underwater vegetation, which has an impact on the quality of the sonar measurements and could be mitigated by performing surveys during winter, when submerged vegetation is less prevalent. Despite the error of the riverbed elevation cross-sections, the hydraulic model gave good estimates of the WSE, with an RMSE below 3 cm. The estimated roughness is also in good agreement with the values measured at a gauging station, with a Gauckler–Manning–Strickler coefficient of M = 16–17 m^1/3/s. Hydraulic modeling results demonstrate that both bathymetry and roughness measurements are necessary to obtain a unique and robust hydraulic characterization of the river. Full article

Hydraulic jump is a phenomenon that occurs in open channels with a sudden and rapid transition of the flow regime from supercritical to subcritical. One of the common approaches in controlling the energy dissipation of hydraulic jumps aims to expand the section of the stilling basin with the development of T-jumps. However, T-jumps without additional baffle and terminal elements are unacceptable for thorough energy dissipation. Therefore, this study investigates the main characteristics of T-jumps in an abruptly expanding channel and in the presence of bed water jets and sinusoidal roughness elements. Such complex configurations are hardly found in the literature. Inflow Froude numbers from 6.2 to 10.85, five relative jet flow rates from 0.10 to 0.27, and three rough beds with roughness wave slopes from 0.33 to 0.60 were selected. Experimental results revealed that increasing the bed corrugation would decrease the length of the jump, the length of the roller, and the sequent depth ratio. The same results were found in presence of bed water jets and sinusoidal roughness elements, but the T-jump would appear to be better stabilized. In fact, it was also observed that increasing the relative flow rate of the jet had a significant effect in controlling the T-jump and reducing its relative length. The simultaneous presence of bed water jets and sinusoidal roughness elements decreased the relative length of the T-jump by about 81% and the tailwater depth by about 42% in comparison with the classic hydraulic jumps on smooth beds. Full article

Compared to text and images, video can show information more vividly and intuitively via a moving picture; therefore, video is widely used in all walks of life. However, videos uploaded or stored in various video applications have not been treated with any protection, and these videos contain a lot of sensitive information that is more likely to be compromised. To solve this problem, video encryption schemes have been proposed. However, the main concern with existing video encryption schemes is that the private information in the encrypted video should be effectively protected, and, thus, the pixel distribution of the original video can be greatly damaged in the process of encryption, resulting in no or poor visual usability of the encrypted video. To this end, a novel color-video encryption scheme is proposed, which can effectively protect video privacy information while retaining certain visual information, thus enhancing the usability of encrypted videos. Firstly, the R, G, and B channels of the original color video are viewed as a whole for splitting. The dimensions of the blocks are three-dimensional, and permutation encryption is performed in three-dimensional blocks, which eliminates the redundancy of information between the video frame channels. Secondly, after permutation encryption, the channels of the video frame are separated, and then each channel is divided into blocks. The shape of the blocks is a square, and substitution encryption and permutation encryption operations are performed in turn. The whole encryption process is combined with the 2D-LSM chaotic system to improve the security of the scheme, as well as to reduce the time. Extensive experiments have been carried out, and the results show that the proposed scheme allows the encrypted video to retain rough visual information and, at the same time, effectively protects privacy, achieving the goal of encrypted video security and usability. Full article

When there is vegetation on the beach or main channel bed, it will have a significant impact on the river channel. This study was based on physical model experiments to investigate the flow conditions of the Jinhu section of the Huaihe River estuary, revealing the influence of reed vegetation on water flow resistance. A new comprehensive roughness formula was proposed, and the predictive effectiveness of the formula was verified. The theoretical results indicate that under the condition of vegetation not being submerged, the comprehensive roughness is directly proportional to the square root of vegetation density in areas with vegetation coverage, the square root of water surface vegetation coverage, and the 2/3 power of the hydraulic radius. The bottom slope does not affect it. Under the condition of vegetation inundation, the comprehensive roughness is smaller than that under the condition of no inundation. The experimental prediction results of the influence of reeds on roughness indicate that the measured roughness values and theoretical roughness calculation values are in good agreement. Under the same operating conditions, the roughness gradually decreases with an increase in flow rate. Under the full-reed working condition, the calculated roughness value and the measured roughness value have the same trend of change, both decreasing with the increase in flow rate. The experimental prediction results of the influence of reeds on the relationship between water level and flow rate show that the roughness value of 0 increases with the increase in reed grass surface coverage rate K_i, and an increase in K_i can lead to an increase in comprehensive roughness. Full article

Fractal geometry is a geometry that focuses on irregular geometric forms and can quantitatively describe rough and uneven surfaces and interfaces. As the main material for making natural fiber geotextile, rice straw fiber can reduce the direct impact of rainfall on soil and reduce the intensity of hydraulic erosion. This study investigates whether the use of rice straw fiber as an additive to reinforce arid soil can inhibit moisture evaporation and prevent cracking. Samples with different fiber contents added (0%, 1%, 2%, and 4%) are placed in an environmental chamber to simulate the effects of an arid climatic condition and control the temperature and humidity levels. The cracking process of the samples is recorded by using a digital camera, and the parameters of the evaporation and cracking processes are quantitatively examined through digital image processing. The results show that all of the samples with fiber have a higher residual water content and can retain 31.4%, 58.5%, and 101.9% more water than without the fibers, respectively. Furthermore, both the primary and secondary cracks as well as crack networks are inhibited in samples with a higher fiber content, that is, 2% or 4% fiber contents. The samples reinforced with fiber also have a smaller crack ratio. Compared with the samples without straw fiber, the final crack ratio of the samples with 1%, 2%, and 4% fiber is reduced by 8.05%, 24.09%, and 35.01% respectively. Finally, the final fractal dimensions of the cracks in samples with fiber contents are also reduced by 0.54%, 5.50%, and 6.40% for the samples with 1%, 2%, and 4% fiber, respectively. The addition of natural fiber as an additive to reduce evaporative cracking in soil can: (1) reduce the soil porosity; (2) enhance the binding force between the soil particles; and (3) block the hydrophobic channels. Therefore, the addition of rice straw fiber to soil can effectively reduce soil evaporation and inhibit soil cracking. Full article

The article presents the results of numerical studies of heat transfer and pressure drops in a channel with transverse micro-fins. The main aim of the study was to prepare the thermal and flow characteristics of such a channel for a variable longitudinal spacing of micro-fins. For the tested pipe with an internal diameter of D = 12 mm, the absolute height of the micro-fins was e = 0.243 mm, which is 2% of its diameter. The tests were carried out for turbulent flow in the range of Reynolds numbers of 5000–250,000 with the variable spacing of micro-ribs in the range of L = 0.28–13.52 mm, which corresponds to their dimensionless longitudinal distance, L/D = 0.023–1.126. For the studied geometries, the characteristics of the friction factor, ft(Re), and the Nusselt number, Nu(Re), are shown in the graphs. The highest values of Nu were observed for a spacing of L/D = 0.092 in the range of Re = 5000–60,000, while the lowest were observed for a geometry of L/D = 0.035 for Re = 60,000–250,000. The friction factors, however, were the highest for the two geometries L/D = 0.161 and L/D = 0.229 over the entire range of the tested Re numbers. A large discrepancy was observed between the friction factors calculated from the Colebrook–White equation (for irregular relative roughness depicted in the Moody diagram) and those obtained from simulations (for pipes with the same roughness height but regular geometry created by micro-fins). An analysis of the heat transfer efficiency of the tested geometries was also presented, taking into account the criterion of equal pumping power, i.e., the PEC (performance evaluation criteria) coefficient. The highest values of the PEC coefficient, up to 1.25–1.28, were obtained for micro-fin spacings of L/D = 0.069 and L/D = 0.092 in the Re number range of 20.000–30.000. Full article