Physical Roughness Research Articles

Optimized Drop-Casted Polyaniline Thin Films for High-Sensitivity Electrochemical and Optical pH Sensors

Conducting polymers used in chemical sensors are attractive because of their ability to confer reversible properties controlled by the doping/de-doping process. Polyaniline (PANI) is one of the most prominent materials used due to its ease of synthesis, tailored properties, and higher stability. Here, PANI thin films deposited by the drop-casting method on fluorine-doped tin oxide (FTO) substrates were used in electrochemical and optical sensors for pH measurement. The response of the devices was correlated with the deposition parameters; namely, the volume of deposition solution dropped on the substrate and the concentration of the solution, which was determined by the weight ratio of polymer to solvent. The characterisation of the samples aimed to determine the structure–property relationship of the films and showed that the chemical properties, oxidation states, and protonation level are similar for all samples, as concluded from the cyclic voltammetry and UV–VIS spectroscopic analysis. The sensing performance of the PANI film is correlated with its relative physical properties, thickness, and surface roughness. The highest electrochemical sensitivity obtained was 127.3 ± 6.2 mV/pH, twice the Nernst limit—the highest pH sensitivity reported to our knowledge—from the thicker and rougher sample. The highest optical sensitivity, 0.45 ± 0.05 1/pH, was obtained from a less rough sample, which is desirable as it reduces light scattering and sample oxidation. The results presented demonstrate the importance of understanding the structure–property relationship of materials for optimised sensors and their potential applications where high-sensitivity pH measurement is required.

A light scattering model for large particles with surface roughness

A physical-optics hybrid method designed for the computation of single-scattering properties of particles with complex shapes, including surface roughness, is presented. The method applies geometric optics using a novel ray backtracing algorithm to compute the scattered field on the particle surface. A surface integral equation based on the equivalence theorem is used to compute the scattered far-field, which yields the full Mueller matrix and integrated single-scattering parameters. The accuracy is tested against the discrete dipole approximation for fixed orientation smooth and roughened compact hexagonal columns for 3 values of refractive index. The method is found to compute asymmetry parameter, and scattering and extinction efficiencies with mean errors of −1.0%, −1.4%, −1.2%, respectively, in a computation time reduced by 3 orders of magnitude. The work represents a key step forwards for modelling particles with physical surface roughness within the framework of physical-optics and provides a versatile tool for the fast and quantitative study of light scattering from non-spherical particles with size much larger than the wavelength.

Effect of pedestrian trampling on aeolian sand dynamics on beach surfaces: An experimental study

Wind tunnel experiments and measurements with the Portable In-Situ Wind Erosion Laboratory (PI-SWERL) were conducted to investigate the effect footprints on a sandy beach have on aerodynamic roughness, physical roughness, and the wind erosion threshold. Footprints parallel and footprints perpendicular to the wind were tested, for bare feet and walking shoes, for a lighter (63 kg) and a heavier (75 kg) person. The data were compared to a flat undisturbed surface, which served as control. Results show that footprints have a significant effect on aerodynamic roughness and on the wind erosion threshold. Aerodynamic roughness is higher, and the wind erosion threshold lower, for footprints parallel to the wind compared to footprints perpendicular to the wind, for footprints produced with bare feet compared to footprints produced by walking shoes, and for footprints made by a heavier person compared to footprints made by a lighter person. The differences with an undisturbed flat surface, for which aerodynamic roughness is small and the wind erosion threshold high, were found to be substantial. Of the measured physical roughness parameters of the footprints, surface area of the imprint showed the highest correlation with aerodynamic roughness. The effect of the volume and the average depth of the imprint on aerodynamic roughness was much smaller or even not statistically significant. The PI-SWERL measurements also suggested that on dry sandy surfaces foot imprints may rapidly disintegrate, even when the wind is only slightly above the erosion threshold. This study shows that when wind erosion models are used to describe and predict the initial phase of wind erosion on sandy beaches, the process of trampling with footprints should at least be considered.

In situ hydrodynamic observations on three reef flats in the Nansha Islands, South China Sea

Waves and currents are responsible for sediment movement around and off coral reefs, affecting reef growth at both geological and modern timescales. Given the wide distribution and limited hydrodynamic information of reefs in the South China Sea, we carried out observations on tidal-cycle hydrodynamics in the Nansha Islands with tripod stationary instruments on the seafloor in order to fill the gap in our understanding of these processes. It was found that the magnitudes of near-bed orbital velocity were comparable with that of the mean tidal current, despite generally calm wave conditions. Waves dominated the combined wave-current skin-friction shear velocities acting on reef sediment, which were significantly higher than those generated by currents alone. Due to the large physical roughness of reef, drag coefficient and hydrodynamic roughness length estimated from logarithmic velocity profiles were two orders of magnitude higher than that in macro-tidal-estuary or inner shelf areas covered with siliceous muds or sands. The combined sinusoidal wave and asymmetric tidal current, along with the physical reef roughness, shaped velocity profile structures in the bottom boundary layer, which exhibited a logarithmic profile during the flood tide and a potential flow during the ebb. In absence of wave breaking, strong turbulence dissipation was observed across the rough reef, promoting strong mixing of water, which is crucial for delivering nutrients for coral growth. These findings imply the need to consider the unique characteristics of rough reef structure and combined effects of waves and currents to model the hydrodynamics in reef environment correctly. This understanding is critical for predicting energy and material transport in reef environments, which is essential for maintaining healthy coral ecosystems, and opens new paths for managing and preserving coral reefs in the face of environmental change.

Quantifying seabed geodiversity of the Archipelago Sea, Baltic Sea, Finland

This study investigated the geodiversity of the Archipelago Sea in the northern Baltic Sea, focusing on geological features and their spatial distribution. By adapting methods used in previous Baltic Sea studies, we conducted spatial analyses of geological data sets including bedrock type, seabed substrates and seabed structures. Bedrock and substrate data were freely available, while seabed structures were modelled from bathymetry data. Geodiversity was quantified using a geodiversity index, which considers the variety of physical elements, roughness and area of the unit. The analyses revealed a diverse seabed environment in the Archipelago Sea with varying geodiversity throughout the study area. Significant features contributing to geodiversity included bedrock fracture and fault zones and large end-moraine formations. Similar patterns have been observed in terrestrial areas of Finland. The analyses also detected relations between archipelago zonation and geodiversity with areas of open sea more homogeneous than the middle and inner archipelago. This study formally recognises the complexity of the seabed in the Archipelago Sea and highlights the importance of understanding the geological processes shaping the region. The results can inform maritime spatial planning and sustainable resource management.

Superhydrophobic and anticorrosion Ni-B/WC@MoS2 composite coatings deposited via jet electrodeposition assisted with ultrasonics

BackgroundElectrodeposited surface coatings are used as an important protective measure for metal surfaces such as bearings. Enhancing the corrosion resistance of the coating is the key to practical application. MethodsNi-B/WC@MoS2 composite coatings deposited on 45-steels were prepared by ultrasound-assisted jet electrodeposition combined with hydrothermal modification of nanoparticles. The impact of ultrasonic power on the composite coatings’ physical phase structure, micro-morphology, surface roughness, surface hydrophobicity and corrosion mechanism were evaluated. Significant FindingsUltrasound-assisted power helped to enhance the deposition of WC@MoS2 powder for the composite coatings. The coating surface prepared with the assistance of 270 W ultrasound showed a dense "cauliflower" shape with a superhydrophobic surface contact angle of 153.7° The composite coating assisted by 270 W ultrasonic power was found to have the largest corrosion potential (-218 mV) and the smallest corrosion current (6.8E-07 A/cm2) after the electrochemical corrosion test. The polarization resistance of the coating was 35,568 Ω·cm2, and the measured corrosion rate was 8.0E-3 mm/a. It was three orders of magnitude lower than that of the composite coating without ultrasonic power assistance. The Ni-B/WC@MoS2 coatings obtained with jet electrodeposition assisted by 270 W ultrasonic wave showed good corrosion resistance.

Internet of Things and hybrid models-based interpretation systems for surface roughness estimation

Abstract Face milling is performed on aluminum alloy A96061-T6 at diverse cutting parameters proposed by the design of experiments. Surface roughness is predicted by examining the effects of cutting parameters (CP), vibrations (Vib), and sound characteristics (SC). Sound characteristics based on surface roughness estimation determine the rarity of the work. In this study, a unique ANN-TLBO hybrid model (Artificial Neural Networks: Teaching Learning Based Algorithm) is created to predict the surface roughness from CP, Vib, and SC. To ascertain their correctness and efficacy in evaluating surface roughness, the performance of these models is evaluated. First off, the CP hybrid model demonstrated an amazing accuracy of 95.1%, demonstrating its capacity to offer trustworthy forecasts of surface roughness values. The Vib hybrid model, in addition, demonstrated a respectable accuracy of 85.4%. Although it was not as accurate as the CP model, it nevertheless showed promise in forecasting surface roughness. The SC-based hybrid model outperformed the other two models in terms of accuracy with a remarkable accuracy of 96.2%, making it the most trustworthy and efficient technique for assessing surface roughness in this investigation. An analysis of error percentages revealed the exceptional performance of SC-based Model-3, exhibiting an average error percentage of 3.77%. This outperformed Vib Model-2 (14.52%) and CP-based Model-1 (4.75%). The SC model is the best option, and given its outstanding accuracy, it may end up becoming the go-to technique for industrial applications needing accurate surface roughness measurement. The SC model’s exceptional performance highlights the importance of optimization strategies in improving the prediction capacities of ANN-based models, leading to significant advancements in the field of surface roughness assessment and related fields. An IoT platform is developed to link the model’s output with other systems. The system created eliminates the need for manual, physical surface roughness measurement and allows for the display of surface roughness data on the cloud and other platforms.

Uncovering the Effect of Physical Conditions and Surface Roughness on the Maximum Spreading Factor of Impinging Droplets Using a Supervised Artificial Neural Network Model

Uncovering the Effect of Physical Conditions and Surface Roughness on the Maximum Spreading Factor of Impinging Droplets Using a Supervised Artificial Neural Network Model

Stigma manifestations in cardiomyopathy care impact outcomes for black patients: a qualitative study

IntroductionInequities in clinical care may contribute to racial disparities observed in studies of heart disease morbidity and cardiogenetic testing outcomes. There is a lack of research aimed at understanding the complexity of those inequities, but stigma likely contributes. This qualitative exploratory study helps close that gap in the literature by describing intersectional stigma manifestations perceived by the Black cardiomyopathy patient population at one academic medical center.MethodsQualitative interviews were conducted with 14 Black cardiomyopathy patients. Interviews aimed to elicit patients’ experiences with discrimination related to diagnosis, symptoms, genetic testing, knowledge of genetic results, genetic counseling, providers’ actions, and providers’ communication. The interview guide was informed by The Health Stigma and Discrimination Framework. Data were also collected about participant demographics, type of cardiomyopathy, age of diagnosis, documentation of relevant family history, and completion of genetic counseling and/or genetic testing.ResultsMore than half of participants reported intersectional stigma manifestations related to their race, age, and/or weight while receiving care from cardiologists, nurse practitioners, genetic counselors, or clinical support staff. Stigma manifestations included physical roughness during patient care, withholding diagnostically-relevant information from the patient, impersonal care, coercion, and use of offensive stereotyped language by providers. These stigma manifestations impacted access to care, uptake of genetic testing, timeline to diagnosis, patient emotion, patient-provider trust, and adherence to medical recommendations.ConclusionsThis study provides nuanced qualitative descriptions of stigma manifestations that affect patient and clinical outcomes in cardiology care and genetic services in one medical center in the Southeastern United States. The results of this study suggest that provider bias and stigma manifestations have an adverse effect on cardiogenetic and clinical outcomes among Black cardiomyopathy patients. Clinical interventions are suggested to assist health professionals in providing culturally-competent and respectful care. These results help inform patient-provider communication, clinical policies, and evidence-based practice in cardiology care and genetics. Continued study of this topic across more institutions and with a larger sample size is needed to confirm the generalizability of the conclusions.

Superhydrophobic Coating Solutions for Deicing Control in Aircraft

The risk of accidents caused by ice adhesion on critical aircraft surfaces is a significant concern. To combat this, active ice protection systems (AIPS) are installed on aircraft, which, while effective, also increase fuel consumption and add complexity to the aircraft systems. Replacing AIPS with Passive Ice Protection Systems (PIPS) or reducing the energy consumption of AIPS could significantly decrease aircraft fuel consumption. Superhydrophobic (SH) coatings have been developed to reduce water adherence to surfaces and have the potential to reduce ice adhesion, commonly referred to as icephobic coatings. The question remains whether such coatings could reduce the cost associated with AIPS and provide durability and performance through suitable tests. In this paper, we then review current knowledge of superhydrophobic and icephobic coatings as potential passive solutions to be utilized alternatively in combination with active systems. We can identify physical parameters, coating composition, structure, roughness, and morphology, durability as properties not to be neglected in the design and development of reliable protection systems in aircraft maintenance.

An Intelligent Robotic System Capable of Sensing and Describing Objects Based on Bimodal, Self‐Powered Flexible Sensors

AbstractThis study presents an intelligent soft robotic system capable of perceiving, describing, and sorting objects based on their physical properties. This work introduces a bimodal self‐powered flexible sensor (BSFS) based on the triboelectric nanogenerator and giant magnetoelastic effect. The BSFS features a simplified structure comprising a magnetoelastic conductive film and a packaged liquid metal coil. The BSFS can precisely detect and distinguish touchless and tactile models, with a response time of 10 ms. By seamlessly integrating the BSFSs into the soft fingers, this study realizes an anthropomorphic soft robotic hand with remarkable multimodal perception capabilities. The touchless signals provide valuable insights into object shape and material composition, while the tactile signals offer precise information regarding surface roughness. Utilizing a convolutional neural network (CNN), this study integrates all sensing information, resulting in an intelligent soft robotic system that accurately describes objects based on their physical properties, including materials, surface roughness, and shapes, with an accuracy rate of up to 97%. This study may lay a robotic foundation for the hardware of the general artificial intelligence with capacities to interpret and interact with the physical world, which also serves as an interface between artificial intelligence and soft robots.

Active Cellulose Acetate/Chitosan Composite Films Prepared Using Solution Blow Spinning: Structure and Electrokinetic Properties.

Cellulose acetate (CA), a very promising derivative of cellulose, has come into the focus of research due to its highly desired good film-forming ability for food packaging applications. Frequently, this derivative is used in combination with other compounds (polymers, nanoparticles) in order to obtain active materials. Here, we report the preparation of thin films made of cellulose acetate loaded with chitosan (CS) using the solution blow spinning (SBS) method. Films are prepared by SBS processing of the polymers mixture solution, considering the following variables: (i) the concentration of cellulose acetate and chitosan in the solution and (ii) the solvent system consisting of acetic or formic acid. The prepared materials are characterized in terms of physical properties, roughness (optical profilometer), porosity, wettability (contact angle measurements), chemical structure (Fourier transform infrared spectrometry), and electrokinetic properties (zeta potential). SBS enables the preparation of CA/CS films with high water vapor permeability, high porosity, and also higher water contact angle compared with pure CA films. The electrokinetic properties of composites are influenced by the inclusion of chitosan, which causes a shift of the isoelectric point (IEP) towards higher pH values, but the magnitude of the shift is not in correlation with chitosan concentration. Adsorption kinetic studies using bovine serum albumin (BSA) as a model protein reveal that chitosan modified cellulose acetate films manifest low affinity towards proteins that suggests prevention of biofilm formation on its surface.

Multidimensional analysis for the correlation of physico-chemical attributes to osteoblastogenesis in TiNbZrSnTa alloys

Data-enabled approaches that complement experimental testing offer new capabilities to investigate the interplay between chemical, physical and mechanical attributes of alloys and elucidate their effect on biological behaviours. Reported here, instead of physical causation, statistical correlations were used to study the factors responsible for the adhesion, proliferation and maturation of pre-osteoblasts MC3T3-E1 cultured on Titanium alloys. Eight alloys with varying wt% of Niobium, Zirconium, Tin and Tantalum (Ti— (2–22 wt%)Nb— (5–20 wt%)Zr— (0–18 wt%)Sn— (0–14 wt%)Ta) were designed to achieve exemplars of allotropes (incl., metastable-β, β + α′, α″). Following confirmation of their compositions (ICP, EDX) and their crystal structure (XRD, SEM), their compressive bulk properties were measured and their surface features characterised (XPS, SFE). Because these alloys are intended for the manufacture of implantable orthopaedic devices, the correlation focuses on the effect of surface properties on cellular behaviour. Physico-chemical attributes were paired to biological performance, and these highlight the positive interdependencies between oxide composition and proliferation (esp. Ti4+), and maturation (esp. Zr4+). The correlation reveals the negative effect of oxide thickness, esp. TiOx and TaOx on osteoblastogenesis. This study also shows that the characterisation of the chemical state and elemental electronic structure of the alloys' surface is more predictive than physical properties, namely SFE and roughness.

Fluid–structure interaction of a sphere rolling along an inclined plane

A comprehensive investigation, using experimental, computational and analytic methods, is reported on the motion of, and the forces on, spheres of different density ratios rolling freely down an incline in a fluid under gravity. The Reynolds number, based on sphere diameter and terminal velocity, ranged up to 1000 for the experiments, and up to 250 for the computer simulations. A modified Reynolds number, incorporating the density ratio, gravitational acceleration and angle of incline, was found to govern the saturated state of the flow. Transition from steady to unsteady flow was sensitive to mass ratio, with lighter spheres undergoing earlier transition. Indeed, positively buoyant spheres develop cross-slope oscillations prior to the onset of shedding. Also of interest, the transition to chaotic wake flow occurs at Reynolds numbers lower than for a sphere forced to roll at a constant speed. In addition to the average sphere motion, flow-induced vibrations were predicted and measured, with quasi-periodic lateral oscillations found to increase as the flow became more unstable, and to decrease with increased density ratio. The study confirms the time-averaged results of a previous experimental study, although closer inspection shows sensitivity to the relative surface roughness of the sphere and plane in experiments; this sensitivity is masked in typical log–log plots of drag against Reynolds number. Physical surface roughness appears to play a role analogous to the necessary imposed gap between the sphere and plane in computations, removing the singularity in drag that would prevent rolling for an incompressible fluid and perfectly smooth surfaces.

Polypropylene film surface modification for improving its hydrophilicity for innovative applications

Organic polymeric materials, especially polyolefins, contain mainly C and H atoms and thus present serious surface problems due to low surface energy and reactive inertness. Using method developed in this work it is possible to convert the H atoms of the polypropylene (PP) film surface into polar groups by treatment with a mixture of chromic, sulphuric, and phosphoric acids in a short time at elevated temperature. Hydroxyl and carboxyl groups on the surface of materials not only determine their chemical and physical properties, but also provide reactive centers for various applications. Optical microscopy (OM) and atomic force microscopy (AFM) analyses have shown that induced surface modification of the PP film causes mainly physical changes, creating microcraters and surface roughness and hence increasing surface tension, while X-ray diffraction (XRD) analysis has confirmed the absence of phase changes. The attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy analysis has confirmed the grafting of polar groups, such as hydroxyl, carboxyl, and carbonyl onto the surface of the PP. This indicates that used mixture destroyed or at least broke down to some extent the covalent bonds of the main carbon skeletons, which were present on PP substrate surfaces and improved surface wettability and zeta potential. The simultaneous thermal analysis (thermogravimetry (TG) and differential scanning calorimetry (DSC)) results have shown that the presence of polar groups in the PP-[O] film samples affects the melting and decomposition temperatures; they are higher than those of PP film. The change in the enthalpy of melting indicated a change in the surface energy. The band gap (Eg) determined from diffuse reflectance spectra in the UV-visible region by the Kubelka-Munk method has decreased for modified PP films, and they have become more suitable for optoelectronics.

Effect of biofilms on the clogging mechanisms of suspended particles in porous media during artificial recharge

Artificial recharge of groundwater is an effective technology for solving the shortage of water resources. The clogging of porous media is a bottleneck that limits the application of this technology. In this study, percolation experiments in sand columns were conducted to investigate the influence of different types of biofilms on the deposition of suspended particles and clogging evolution during artificial recharge. A unique aspect of this study is the consideration of biofilms coated on porous media when the clogging mechanisms of suspended particles in porous media are explored. At the end of the recharge process, the relative hydraulic conductivity (K’) of the porous media in descending order was Pseudomonas aeruginosa experimental group (PA) > Bacillus subtilis experimental group (BS) > mixed microbial consortium experimental group (MC) > suspended particle only group (SP). The suspended particles in SP- moved more deeply into the sand column than those in BS, PA, and MC. Electron microscopy, high-throughput sequencing, and confocal laser scanning microscopy were used to identify the mechanisms governing clogging evolution under the influence of biofilm existence. The presence of a biofilm not only alters the surface charge and physical roughness of the porous media, but also affects the electrostatic interaction between the porous media and suspended particles. Biofilms combine tightly with suspended particles by binding and adhesion, which can form tight biofilm-particle aggregations. Compared with deposition of particle-only in SP, the biofilm-particle aggregations on the surface of the porous media are more firm. The biofilm coated on the surface of porous media occupied the pore vacancy and narrowed the void space compared with that in clean sand, which induced physical straining. As the thickness of biofilm coated on the sand surface increased, the more suspended particles were deposited on the sand surface in PA. These findings provide insights into clogging under the influence of biofilms and have implications for future field-based artificial recharge.

Crossmodal Texture Perception Is Illumination-Dependent.

Visually perceived roughness of 3D textures varies with illumination direction. Surfaces appear rougher when the illumination angle is lowered resulting in a lack of roughness constancy. Here we aimed to investigate whether the visual system also relies on illumination-dependent features when judging roughness in a crossmodal matching task or whether it can access illumination-invariant surface features that can also be evaluated by the tactile system. Participants ( N = 32) explored an abrasive paper of medium physical roughness either tactually, or visually under two different illumination conditions (top vs oblique angle). Subsequently, they had to judge if a comparison stimulus (varying in physical roughness) matched the previously explored standard. Matching was either performed using the same modality as during exploration (intramodal) or using a different modality (crossmodal). In the intramodal conditions, participants performed equally well independent of the modality or illumination employed. In the crossmodal conditions, participants selected rougher tactile matches after exploring the standard visually under oblique illumination than under top illumination. Conversely, after tactile exploration, they selected smoother visual matches under oblique than under top illumination. These findings confirm that visual roughness perception depends on illumination direction and show, for the first time, that this failure of roughness constancy also transfers to judgements made crossmodally.

Importance of leaf surface and formulation properties in predicting wetting outcomes.

Leaf wettability is a major hurdle for the retention of agrichemical sprays that is combated, in part, by using adjuvant modified formulations. Scientists must understand the properties of the leaf surface and the formulation that govern wetting to intelligently select or formulate products to target specific pests. A comprehensive database comprising 11 synthetic surfaces and 54 leaf surfaces (species, adaxial and abaxial sides, cultivars, and plant age) using 35 formulations (neat solutions and adjuvants solutions at different concentrations) was compiled. Surface properties of the physical roughness and chemical polarity, as quantified by the wetting tension dielectric method, and formulation properties of surface tension and polarity, as quantified by dielectric constant, were found to govern wetting. A comprehensive wetting model was developed that employed these variables and was capable of accurately predicting the wetting outcome (R2 =0.86) on all the leaf and synthetic surfaces investigated. This model adequately predicts adjuvant formulation wetting despite exact formulation polarity being unknown. Wetting can be modelled for a wide range of surfaces and solutions. The comprehensive wetting model developed shows potential to better predict the wetting outcome of adjuvant formulations should a method to quantify the formulation dielectric constant be developed. This research provides a significant advancement in the understanding of the properties governing wetting, which may aid the selection and development of adjuvants to target specific surfaces. © 2022 Society of Chemical Industry.

Quantum efficiency, photoemission energy spectra, and mean transverse energy of ultrananocrystalline diamond photocathode

The quantum efficiency and mean transverse energy of electrons emitted from a cathode determine the quality of beams generated from photoinjectors. The nitrogen-incorporated ultrananocrystalline diamond, (N)UNCD, is a new class of robust semiconductor photocathodes, which has been considered in photoinjectors for high peak current extraction. In this work, we measure the spectral response in quantum efficiency, photoemission energy spectra, and mean transverse energy of the (N)UNCD photocathode using a photoemission electron microscope. The observed quantum efficiency was comparable to that of copper photocathodes. Photoemission spectra showed the evidence of scattering of electrons before emission. This relaxation of electrons due to scattering is also observed in the spectral response of the mean transverse energy. The mean transverse energy is limited to ∼70 meV at the threshold. We attribute this to the physical and chemical roughness of the (N)UNCD photocathode and, hence, smoother films will be required to further reduce the mean transverse energy obtained from the (N)UNCD photocathode.

Computational fluid dynamics simulation of rough bed open channels using openFOAM

With increased flood risk due to climate change, population expansion and urbanisation; robust waterway design and management are critical. One common type of waterway used to gather and transport ground water is the open channel. Most simulations do not account for the physical roughness of the bed, instead using a roughness coefficient. This means that only the turbulent energy content can be modelled whilst physical turbulent eddies and vortices cannot. Furthermore, many past studies assume the free surface is a rigid lid. This could affect the way that turbulent structures near the free surface behave. Computational Fluid Dynamics simulation of an open channel with a rough bed and rigid lid are conducted using OpenFOAM. Results show good correlation with experimental tests. It can be visually observed that turbulent structures generated from the rough bed do interact with the free surface and thus a rigid lid is perhaps not a great approximation. This is supported by an apparent decrease in the Reynolds shear stress from the free surface and 30% of the flow depth immediately beneath.