Ground Effect Research Articles

A rail corrugation index to characterize noise impacts and grinding effectiveness on rail transit systems

Despite general agreement that rail corrugation generates unwanted noise, there is a need to quantify the relationship between rail corrugation and noise and to leverage this relationship within preventive rail grinding programs. This paper develops a novel rail corrugation index (RCI) and demonstrates the suitability of that index to characterize the relationship between corrugation and noise, to assess grind effectiveness, and to predict noise as a function of rail corrugation. Using a time-series data set collected at a North American rail transit property, the proposed RCI illustrated corrugation growth as a function of accumulated tonnage and an expected reduction of corrugation after grinding. The RCI also correlated well with corresponding wayside noise observations. The evident response behavior and the relationship between rail corrugation and wayside noise gave rise to the assessment of grind effectiveness using the RCI. Further, a modelling effort demonstrated that noise can be predicted using the RCI calculated from only one rail (left or right) on a tangent section. This result suggests that there may also be an opportunity to predict corrugation using noise data, thus limiting the need for track downtime required to measure corrugation.

Performance Evaluation of a Height Adjustable Mini Combine Harvester

Mini combine harvesters have been very popular among paddy farmers. The compact size of the machine, in addition to the axial flow threshing mechanism and the effect of low ground pressure on paddy soil, makes it a potential alternative for efficient paddy harvesting of a height-adjustable mini combine harvester used for harvesting paddy fields. This type of harvester was tested in typical paddy field conditions planted with MR297 variety at MARDI Seberang Perai. The performance tests included measuring theoretical and effective field capacity, field efficiency, soil bearing capacity before and after machine disturbance and machine slippage. The fuel consumption was also recorded. The combined harvesting losses were also measured during the experiment. Results showed that in wet and muddy conditions, the mini combine harvester obtained a theoretical field capacity (TFC) of 1.28 ha/hr, effective field capacity (EFC) of 0.94 ha/hr and a field efficiency (FE) of 73.4%. The average fuel consumption of the mini combine harvester was 25 L /ha. The wheel slippage in wet paddy fields was 2.18% and on farm roads was 1.55%. The mini combine harvester also contributed to producing less ground effects, combined with the use of low ground contact pressure tracks, that caused minimal soil disturbance that would affect the soil hardpan layer. This mini combine harvester produced an average harvesting loss of 2.3% with an average harvesting impurity of 10.65%. The mini combine harvester had enough power to move in typical paddy field conditions, with no soft soil problems. The mini combine harvester was able to turn 360 degrees within a small area, which made it suitable for harvesting in paddy fields. Thus, this mini combine harvester has the potential to be used for paddy harvesting with the ability to not only produce minimal harvesting loss, but also produce less ground contact pressure which can help to manage the soil hardpan layer from being easily damaged.

Physics-informed Neural Network for Quadrotor Dynamical Modeling

The explosive growth of civil applications of Unmanned Aerial Vehicles (UAVs) calls for control algorithms that enable safe and trustworthy operations, especially in complex environments to facilitate real-world deployment. Although Model-Based Control (MBC) has found great applicability in the last decades, it relies heavily on the accuracy of the underlying mathematical models. Thanks to their powerful approximation capability, data-driven approaches such as Artificial Neural Networks (ANNs) have raised a great interest in UAV dynamical modeling in recent years. Despite the promising results achieved in learning either full or partial dynamics such as aerodynamic effects, prior studies merely pay little to no attention to the black-box nature of ANNs, yielding poorly interpretable learning processes and implying a lack of generalization capability due to undesirably learned spurious relationships among features and labels. While nowadays practitioners and society are far from being concerned just with performance, such risk evidently reduces the overall trustworthiness of the control system with ANNs as control-oriented models. With the goal of both accurate and interpretable neural modeling of nonlinear dynamics, we propose a novel modeling approach that utilizes Physics-Informed Neural Networks (PINN), designed to seamlessly embed physical laws into Deep Neural Networks (DNN). To further enhance model interpretability, we adopt the Covariance Confidence Ellipse (CCE) as post-hoc visualization to help understand the model behavior. We also set up a visual and physical simulator based on AirSim with custom implementation on quadrotor ground effect, which is made publicly available to facilitate further experiments for the community. An extensive simulation campaign validates our approach on data sets including aerodynamics and periodic wind, highlighting advantages regarding the accuracy and physical consistency, pointing to further insight on the development of learning-based control-oriented models for quadrotors, and facilitating flight controller design with performance guarantees.

A Numerical Comparative Study of the Selected Cambered and Reflexed Airfoils in Ground Effect

A Numerical Comparative Study of the Selected Cambered and Reflexed Airfoils in Ground Effect

Effect of surface grinding on the microstructure and corrosion of Al-Mg-Si-Cu alloys

Surface treatment has shown strong effects on the corrosion resistance of Al-Mg-Si-Cu alloys. To elucidate the surface grinding effects, a set of the peak-aged Al-Mg-Si-Cu samples are ground using SiC papers with different grits, and the ground surface microstructure and corrosion performance are investigated. The results show that grinding generates a deformed near-surface layer. The deformed layer is characterized by nanocrystalline and the alloying element Cu segregates at nano-grained boundaries. The Cu segregation bands increase the available cathode area and the potential difference between the grain boundary and grain interior, which enhances the microgalvanic corrosion effect between the phase α-AlFeSi (Mn, Cu) and the adjacent matrix. As the SiC paper grit number decreased from 1200 to 80, the Cu segregation bands of the deformed layers increases from 600 to 1600 nm, the corresponding corrosion current density increases from 1.0 ± 0.1 to 22.8 ± 0.7 μA.cm−2, and the corrosion potential decreases from −742 ± 13.1 to −791 ± 15.0 mV (versus SCE).

Winds and eddy dynamics in the urban canopy layer over a city: A parameterization based on the mixing-layer analogy

Urban atmospheric flows are vital to the global ecology. This study characterizes urban canopy layer (UCL) dynamics and parameterizes the flows in the atmospheric surface layer (ASL) over heterogeneous urban surfaces. Large-eddy simulations (LESs) are used to transiently calculate the winds over a real, dense city. A linear function of eddy diffusivity of momentum KM is applied to the lower UCL. Analogous to its mixing-layer counterpart, the strong UCL top shear manifests an inflected mean wind speed profile which aligns well with the exponential law. The solutions to the mixing length lm and the turbulent momentum flux are analytically derived by consolidating the mixing-layer type shear and the form drag from the explicitly resolved roughness elements. The behavior of lm in the lower UCL, especially its peaked level, is captured well. Based on the balance between shear and form drag, an aerodynamic effective roof level Hae is designated where the ground effect is alleviated under shear dominance. Results reveal that a rougher urban surface generates eddies with a larger shear length scale, thus enhancing momentum transport. In-canopy turbulence mixing, which slows down wind decay, is also enhanced, resulting in stronger street-level breezes. The newly developed ASL flow model will be beneficial to urban planning by offering reliable predictions, effectuating the management of urban sustainability.

Dynamic lift characteristics of a water borne WIGcraft

A water borne WIGcraft in principle, generates much higher lift than that of an equivalent free-flight airplane, air borne WIGcraft and planing boats due to the complementary ground effect aerodynamic, hydrodynamic and hydrostatic lift generated by the wings and submerged portion of the hull surfaces. However, the coupling of the ground effect aerodynamics and hydrodynamics of the vehicle, compounded by hull-generated water-spray impinging on its wings present challenges when predicting dynamic forces on the vehicle. Capturing the complex air-water flow about the wings, and its effects on the dynamic lift on the vehicle require advanced and computationally expensive high fidelity nonlinear numerical solution. This paper proposes a semi-empirical model as a simplified alternative to estimate the dynamic lift on the vehicle. The model was developed based on the theories of ground effect aerodynamics and planing watercraft hydrodynamics, as well as physical observations from fully constrained experiments of a multihull watercraft model with and without wings. The various elemental components of the water borne WIGcraft dynamic lift including ground-effect and hull-generated water-spray induced lift on the wings were estimated. To ensure simplicity and consistency in coupling the aerodynamic and hydrodynamic lift coefficients, an equivalent hydrodynamic lift coefficient was proposed for the aerodynamic lift coefficient of the wings of the vehicle. The results of the proposed semi-empirical model and that of the fully constrained model experiments are in satisfactory agreement. The results of the total dynamic lift of the water borne WIGcraft suggest that for a water-borne WIGcraft operating at large draughts with water-spray impinging on its wings, the effect of the wings’ proximity to the free surface water is secondary. The contribution of the hull generated water spray to the total dynamic lift force is significant.

Parasitic Resilience: The Next Phase of Public Health Preparedness Must Address Power Imbalances Between Communities.

Community resilience, a system's ability to maintain its essential functions despite disturbance, is a cornerstone of public health preparedness. However, as currently practiced, community resilience generally focuses on defined neighborhood characteristics to describe factors such as vulnerability or social capital. This ignores the way that residents of some neighborhoods (as "essential workers") were required during the COVID-19 pandemic to sacrifice their wellbeing for the sake of others staying at home in more affluent neighborhoods. Using the global care chain theory, we analyze the way that the resilience of affluent neighborhoods depends on siphoning off the labor of other, less affluent neighborhoods, creating what we call the parasitic nature of resilience. We argue that understanding this neighborhood interdependence-and accounting for its parasitic nature-should be prioritized by public health authorities to prevent unintentional harm in future pandemics. Otherwise, any public health emergency response that relies on this labor (as did the COVID-19 pandemic response) depends on exploitative practices that produce the very disparities the response is trying to address. We explore the theoretical grounding and practical effects of this idea to provide the preparedness enterprise with an initial set of theoretical tools to move from a model of community resilience to one of community renewal. The community renewal model is based on an underlying ethics of care, in which systems are redesigned to become more prosocial during a public health response. We believe this model can more successfully address the tragic inequities in labor and health outcomes that we see during public health emergencies.

Study on Shock-Absorbing Effect of a Double-Story Isolation Structure Considering Soil–Structure Interaction

The double-story isolation structure is a novel development based on the mid-story isolation structure. To accurately reflect the seismic response of the double-story isolation structure, this study considers a dynamic elastoplastic analysis model that incorporates soil–structure interaction (SSI). Comparative models of a base-fixed structure and a mid-story isolation structure are also established. The results indicate that the double-story isolation structure has a longer structural period compared to the mid-story isolation structure. Furthermore, the structural period increases as the soil softens and the structure becomes more flexible. When considering SSI on hard soil versus not considering SSI, the double-story isolation structure exhibits smaller base shear, story force, inter-story displacement, maximum acceleration of the top floor, and displacement of the upper isolation layer, indicating the significant shock-absorbing effect of the double-story isolation structure. However, when SSI is considered on soft soil, the shock-absorbing effect of the isolation structure diminishes, and the effectiveness of the double-story isolation structure may not necessarily surpass that of the mid-story isolation structure. In all three soil conditions, the compressive stresses of the isolation bearings in the upper isolation layer of the double-story isolation structure were lower than those in the isolation bearings of the base isolation layer. Additionally, the double-story isolation structure demonstrates reduced compressive stress in the isolation bearings, fewer plastic hinges in the frame, and less stress damage compared to the mid-story isolation structure. Consequently, the risk of overturning damage in the double-story isolation structure is significantly reduced compared to the mid-story isolation structure. The effect of soft ground on structures can be highly detrimental, which should be paid more attention to during the design process. This study offers valuable insights for future research on double-story isolation systems and serves as a reference for the development of high-performance building structures in the future.

The surface grinding-induced oxide scale exfoliation of an austenitic alloy in supercritical CO2

This work studied the effect of surface grinding on the corrosion behaviour of an austenitic stainless steel (SS) in the supercritical CO2. The results show that the polished surface had a typical oxide structure including an outer and an inner oxide layer while the ground surface had a much thinner oxide scale with Cr2O3, SiO2, and Mn2O3 after 3000 h exposure. The C-enrichment lamellar was observed in the oxide scale which was attributed to the exfoliation of the oxide scale and further penetrated into the matrix as Cr-rich carbides in the specimen with a ground surface.

Reinforcement learning for shared autonomy drone landings

Novice pilots find it difficult to operate and land unmanned aerial vehicles (UAVs), due to the complex UAV dynamics, challenges in depth perception, lack of expertise with the control interface and additional disturbances from the ground effect. Therefore we propose a shared autonomy approach to assist pilots in safely landing a UAV under conditions where depth perception is difficult and safe landing zones are limited. Our approach is comprised of two modules: a perception module that encodes information onto a compressed latent representation using two RGB-D cameras and a policy module that is trained with the reinforcement learning algorithm TD3 to discern the pilot’s intent and to provide control inputs that augment the user’s input to safely land the UAV. The policy module is trained in simulation using a population of simulated users. Simulated users are sampled from a parametric model with four parameters, which model a pilot’s tendency to conform to the assistant, proficiency, aggressiveness and speed. We conduct a user study (n=28) where human participants were tasked with landing a physical UAV on one of several platforms under challenging viewing conditions. The assistant, trained with only simulated user data, improved task success rate from 51.4 to 98.2% despite being unaware of the human participants’ goal or the structure of the environment a priori. With the proposed assistant, regardless of prior piloting experience, participants performed with a proficiency greater than the most experienced unassisted participants.

Prediction of aerodynamic characteristics of high-lift Common Research Model in ground effect

Abstract Reynolds Averaged Navier-Stokes (RANS) simulations are performed to investigate the aerodynamic characteristics of the NASA Common Research Model (CRM) in its high-lift (HL) configuration in close proximity to the ground. The RANS simulations are conducted at a moderate Reynolds number of $Re = 5.49 \times {10^6}$ and $M = 0.2$ with the use of the Spalart-Allmaras (SA) turbulence model. out of ground effect (OGE) simulation results are validated against available wind tunnel data before proceeding to in ground effect (IGE) simulations. The obtained computational results in the immediate vicinity of the ground with asymmetric aircraft attitudes demonstrate significant changes in the longitudinal and lateral-directional aerodynamic characteristics, which should be taken into account in flight dynamics analysis of aircraft during take-off and landing in crosswind conditions.

Enhancement of cation exchange and glucose binding capacity, flavonoids release and antioxidant capacity of Tartary buckwheat powder with ultrafine grinding

The objective of this paper was to study the effects of ultrafine grinding on the cation exchange capacity, glucose binding capacity and in vitro digestion characteristics of Tartary buckwheat powder. The results showed that the cation exchange ability and glucose binding strength of Tartary buckwheat powder, Tartary buckwheat bran powder and Tartary buckwheat core powder increased significantly with the increase of crushing frequency (20, 40 and 60 Hz), and the Tartary buckwheat bran powder was the highest. The results of in vitro digestion showed that ultrafine grinding improved the flavonoid release and antioxidant activity of Tartary buckwheat bran powder in the in vitro digestion process. The correlation analysis indicated that the amount of flavonoids released in digestive fluid was significantly related to antioxidant activity. This study may provide a theoretical basis for improving the physicochemical properties and functions of Tartary buckwheat by ultrafine grinding technology.

Influence of Rate Effects, Temperature, and Moisture Content on the Geomechanical Behavior of Marine Clays

Abstract The study of the geomechanical behavior of marine clays is a basic requirement for project optimization of the oil and natural gas industry. As part of a large-scale project, this study explored the effects of moisture content, temperature, and rate effects using laboratory vane shear tests. A series of results has helped in the identification of the effects of ground freezing on the undrained shear strength. For temperatures below freezing (−2.0 °C) the undrained shear strength increases with increasing water content and decreases with increasing shear rates for applied angular velocities in the range of 0.0025– 0.015 rpm. Apparently, with the freezing of pore fluids, the shear strength is partially governed by the strength of the ice-soil particle bonds. The increase in shear rate appears to facilitate the breakage of the ice bonds and afterwards the ice crystals reducing the viscous effects on the mobilized shear strength. Conversely, samples tested at temperatures above freezing show an increase in undrained shear strength with the increase in the imposed angular velocity and decreases with increasing soil moisture. Based on these studies, it is concluded that rate effects should be coupled to the influence of temperature and moisture content in the design of offshore structures.

Modeling of the Aqueous Solubility of N-butyl-N-methyl-1-phenylpyrrolo[1,2-a] pyrazine-3-carboxamide: From Micronization to Creation of Amorphous-Crystalline Composites with a Polymer.

N-butyl-N-methyl-1-phenylpyrrole[1,2-a] pyrazine-3-carboxamide (GML-3) is a potential candidate for combination drug therapy due to its anxiolytic and antidepressant activity. The anxiolytic activity of GML-3 is comparable to diazepam. The antidepressant activity of GML-3 is comparable to amitriptyline. GML-3 is an 18 kDa mitochondrial translocator protein (TSPO) ligand and is devoid of most of the side effects of diazepam, which makes the research on the creation of drugs based on it promising. However, its low water solubility and tendency to agglomerate prevented its release. This research aimed to study the effect of dry grinding, the rapid expansion of a supercritical solution (RESS), and the eutectic mixture (composite) of GML-3 with polyvinylpyrrolidone (PVP) on the particle size, dissolution rate, and lattice retention of GML-3. The use of supercritical CO2 in the RESS method was promising in terms of particle size reduction, resulting in a reduction in the particle size of GML-3 to 20-40 nm with a 430-fold increase in dissolution rate. However, in addition to particle size reduction after RESS, GML-3 began to show signs of a polymorphism phenomenon, which was also studied in this article. It was found that coarse grinding reduced particle size by a factor of 2 but did not significantly affect solubility or crystal structure. Co-milling with the polymer made it possible to level the effect of the appearance of a residual electrostatic charge on the particles, as in the case of grinding, and the increased solubility in the resulting mechanical mixtures of GML-3 with the polymer may also indicate the dissolving properties of polymers (an increase in 400-800 times). The best result in terms of GML-3 solubility was demonstrated by the resulting GML-3:PVP composite at a ratio of 1:4, which made it possible to achieve a solubility of about 80% active pharmaceutical ingredient (API) within an hour with an increase in the dissolution rate by 1600 times. Thus, the creation of composites is the most effective method for improving the solubility of GML-3, superior to micronization.

Effect of Induction Heating on Surface Properties of Hot-Pressed Ceramics Based on Nanopowders Si3N4 and TiN

The effect of induction heating on the surface properties of hot-pressed ceramics based on plasma chemical nanopowders Si3N4 and TiN (additives: Al2O3, AlN, and Y2O3) has been studied. The research demonstrates the formation of a modified layer on the surface of the hot-pressed material. The study examines the porosity, hardness, fracture toughness, brittleness, distribution of elements, and wear of hot-pressed ceramics on the surface before and after additional grinding. Removal of the surface porous layer results in increased density and hardness, leading to a higher number of acoustic emission signals during scratching with a Vickers indenter. A different response to scratching indicates a transgranular or intergranular fracture of the structure. The presence of porosity and carbon contamination on the surface layer of materials negatively impacts the properties of TiN-reinforced ceramics based on Si3N4-Al2O3-AlN (SIALON). However, the addition of Y2O3 effectively prevents carbon penetration and reduces the effect of grinding. Additionally, the dark-colored tone observed on the outer volume of the samples suggests a non-thermal microwave effect of the induction furnace.

Grinding effect of thermoplastic mold steel using green manufacturing concepts combined with various conventional wheels

Grinding effect of thermoplastic mold steel using green manufacturing concepts combined with various conventional wheels

Ground granulated iron silicate slag as supplementary cementitious material: Effect of prolonged grinding and granulation temperature

The metallurgical and cement industries contribute significantly to anthropogenic carbon dioxide emissions. Utilizing oxidic by-products from the metallurgical industry as supplementary cementitious materials (SCMs) can improve resource efficiency and reduce emissions from cement production. Iron silicate copper slags have been studied as SCMs, but mainly in systems where Portland cement is used as an activator. There is limited research on the inherent reactivity of the slag under changing processing conditions. The present study offers insight into the effect of granulation temperature and grinding on the inherent reactivity of an industrially produced iron silicate copper slag. The results showed that granulation temperature had an insignificant effect on reactivity, while grinding generated substantial improvements. The latter effect was concluded to stem from the increased specific surface area, increased number of sites for nucleation and growth of hydrates, and changes in the inherent reactivity owing to structural changes induced by the grinding.

Locomotion performance of an axisymmetric ‘flapping fin’

Inspired by the jet-propulsion mechanism of aquatic creatures such as sea salps, a novel locomotion system based on an axisymmetric body design is proposed. This system consists of an empty tube with two ends open. When the diameters of the front and back openings are changed periodically, the forward-backward symmetry is broken so that the system starts swimming. Viewed within a cross section, this system resembles a two-dimensional flapping fin with its leading edge located at the front opening and the trailing edge at the back opening. The feasibility of this system has been proven via numerical simulations using a fluid-structure interaction model based on the immersed-boundary framework. According to the results, at relatively low Reynolds number (O(102)), this simple locomotion method can easily achieve a mean swimming speed of 2 to 3 body lengths per deformation period. Further simulations illustrate the following characteristics: (1) within the chamber, the hydrodynamic interactions among different parts of the body leads to a performance-enhancing mechanism similar to the ground effect; (2) reducing the diameter of the body can strengthen this effect so that both the swimming speed and the energy efficiency are improved; (3) for better performance the amplitude of diameter oscillation at the trailing edge should be larger or at least equal to the one at the leading edge.

Optimisation of rail profile and grinding pattern in the curve section of a subway

During routine rail maintenance, rail grinding of sharp curves is challenging. In particular, setting up the grinding pattern is essential. A rail-grinding pattern optimisation method is proposed based on the mathematical relationship between the grinding pattern parameters and geometric parameters of the rail grinding profile. In this method, the design variables and constraints are reasonably selected, and a multi-objective optimisation function considering the wheel-rail contact stress, wheel-rail lateral force, and rail grinding amount is established. The optimisation model is solved using a chaotic microvariation adaptive genetic algorithm. The optimisation method is applied to the repairable grinding of a worn rail in a metro curve section. The results demonstrate that using this method can realise an ideal grinding pattern with the expected grinding effect in addition to high accuracy and high optimisation speed. The wheel-rail contact characteristics, wear characteristics, and train dynamic performance are significantly improved after rail grinding; this is significant for conducting grinding operations and improving the train’s curve-passing ability. Therefore, this study provides theoretical guidance for formulating rail-grinding patterns.