Ground Effect Research Articles

Physics-informed scaling laws for theperformance of pitching foils inschooling configurations.

This study introduces novel physics-based scaling laws to estimate the propulsive performance of synchronously pitching foils in various schooling configurations. These relations are derived from quasi-steady lift-based and added mass forces. Hydrodynamic interactions among the schooling foils are considered through vortex-induced velocities imposed on them, constituting the ground effect. Generalized scaling equations are formulated for cycle-averaged coefficients of thrust and power. These equations encompass both the pure-pitching and induced velocity terms, capturing their combined effects. The equations are compared to computational results obtained from two-foil systems, exhibiting foil arrangements over a wide range of parameter space, including Strouhal number (0.15 ≤ St ≤ 0.4), pitching amplitude ([Formula: see text]) and phase difference ([Formula: see text]) at Re = 1000-10 000. The individual contributions of pure-pitching and induced velocity terms to propulsive performance elucidate that solely relying on the pure-pitching terms leads to inadequate estimation, emphasizing the significance of the induced velocity terms. The validity of the approach is further assessed by testing it with three-foil and five-foil configurations, which displays a collapse of estimated and measured results. This indicates that the scaling laws are applicable to multi-foil arrangements.

Characteristics and optimization of multi-body separation in supersonic ground effects

The electromagnetic launch of aerospace vehicles is an option for reusable earth/orbit space transportation in the future. In contrast to open space, complex ground effects emerge in supersonic near-ground multi-body separations. Here, the separation processes between a supersonic aerospace vehicle (traveling at Mach 1.5) and an electromagnetic sled were studied with a focus on the characteristics of the flow evolution and aerodynamic interference. The results show that the evolution of the supersonic near-ground separation can be divided into three substages: choked flows in the narrow gap, multi-body shock interactions and independent ground effect interference. The aerodynamic loads of the vehicle strongly correspond to the separation stages. The high-pressure region at the leading edge of the electromagnetic sled continuously sweeps the vehicle abdomen and causes significant fluctuations in the aerodynamic lift and moment, which play a dominant role in the separation trajectory. The altitude of the vehicle that flies away from the electromagnetic sled is relatively stable when the preset attack angle is 0° Following this separation, the vehicle has a pitch angle of -0.25° and tends toward a negative angle of attack. A vertical distance of 4.2 m is insufficient for optimal separation. Thus, the separation characteristics were optimized by combining the preset rudder deflection angle of 0° and inclined track with a slope angle of 1.5° Following this separation, the pitch angle of the vehicle is 3.4°, and the vertical distance increases to 14.8 m, which significantly improves the separation safety.

Effect of Grinding and Polishing Protocols on Surface Roughness, Flexural Strength, and Phase Transformation of High-Translucent 5 mol% Yttria-Partially Stabilized Zirconia

Abstract Objectives This study evaluated surface roughness, biaxial flexural strength, and phase transformation of 5Y-PSZ after grinding and polishing with different protocols. Material and Methods Two commercial 5Y-PSZ, Lava Esthetic (L) and Cercon xt (C), were used and divided into 3 groups: LC and CC represented unpolished control groups; LE and CE were polished with protocol I (EVE DIASYNT® PLUS HP following with EVE DIACERA RA); and LJ and CJ were polished with protocol II (Superfine diamond bur following with Jota ZIR Gloss polishing kit). Surface roughness was evaluated after polishing step-by-step with a contact-type profilometer. After high-gross polishing, the specimens were subjected to biaxial flexural strength test, crystallographic microstructure analysis using an X-ray diffractometer (XRD), and surface micro-topography using scanning electron microscopy (SEM). Statistical Analysis Surface roughness differences after each step and biaxial flexural strength between groups were evaluated with one-way ANOVA, followed by Bonferroni post-hoc analysis. Changes in surface roughness across four different time points within groups were assessed using one-way repeated measures ANOVA, followed by Bonferroni post-hoc analysis. Results After high-gross polishing, both polishing protocols showed significantly lower surface roughness than the grinding group (p < 0.05). The LE and CE groups exhibited the highest surface roughness values, which were significant differences from the LJ and CJ groups (p < 0.05). The LE group showed significantly lower biaxial flexural strength compared to the LC group (p < 0.05). However, there was no statistically significant difference in the CE and CJ groups compared to the control group (p > 0.05). Furthermore, all polishing protocols did not change the phase transformation of zirconia. Conclusion Polishing protocol II provided a smoother surface than the protocol I after high-gross polishing, while the biaxial flexural strength of materials remained unaffected.

Lift–Drag Performance of a New Unmanned Aerial Vehicle in Different Media and Ground Effect

Water–air trans-media unmanned vehicle is a kind of aircraft, which can freely fly in the air, sail in the water and pass through free surface. For trans-media aircrafts, the development process from air–surface to air–underwater and from submarine-launched drive to autonomous drive is investigated. By analyzing the characteristic of manta ray, flying fish and existing aircraft, this paper proposes a new water–air trans-media unmanned vehicle with flat dish-airfoil-shaped main body and telescopic NACA-type wing. Then the numerical method to calculate the lift and drag forces is established and validated by the results of classic NACA cases. On this basis, the flow field around the new vehicle is numerically simulated, and its lift–drag performances in different media (air and water) and ground effect are analyzed, comparing it with a model inspired by the Blackwing Unmanned Aerial Vehicle (UAV). The findings illustrate the superior performance of the new vehicle in terms of lift and drag forces, offering an innovative design framework for water–air trans-media UAV applications.

Aircraft Wake Evolution Prediction Based on Parallel Hybrid Neural Network Model

To overcome the time-consuming drawbacks of Computational Fluid Dynamics (CFD) numerical simulations, this paper proposes a hybrid model named PA-TLA (parallel architecture combining a TCN, LSTM, and an attention mechanism) based on the concept of intelligent aerodynamics and a parallel architecture. This model utilizes CFD data to drive efficient predictions of aircraft wake evolution at different initial altitudes during the approach phase. Initially, CFD simulations of continuous initial altitudes during the approach phase are used to generate aircraft wake evolution data, which are then validated against real-world LIDAR data to verify their reliability. The PA-TLA model is designed based on a parallel architecture, combining Long Short-Term Memory (LSTM) networks, Temporal Convolutional Networks (TCNs), and a tensor concatenation module based on the attention mechanism, which ensures computational efficiency while fully leveraging the advantages of each component in a parallel processing framework. The study results show that the PA-TLA model outperforms both the LSTM and TCN models in predicting the three characteristic parameters of aircraft wake: vorticity, circulation, and Q-criterion. Compared to the serially structured TCN-LSTM, PA-TLA achieves an average reduction in mean squared error (MSE) of 6.80%, in mean absolute error (MAE) of 7.70%, and in root mean square error (RMSE) of 4.47%, with an average increase in the coefficient of determination (R2) of 0.36% and a 35% improvement in prediction efficiency. Lastly, this study combines numerical simulations and the PA-TLA deep learning architecture to analyze the near-ground wake vortex evolution. The results indicate that the ground effect increases air resistance and turbulence as vortices approach the ground, thereby slowing the decay rate of the wake vortex strength at lower altitudes. The ground effect also accelerates the dissipation and movement of vortex centers, causing more pronounced changes in vortex spacing at lower altitudes. Additionally, the vortex center height at lower altitudes initially decreases and then increases, unlike the continuous decrease observed at higher altitudes.

Unique Operating Conditions Analysis of Turboshaft Engines Based on Nonlinear Integrated Model

The unique mission of the helicopter compared to the fixed-wing aircraft introduces challenges to the aerodynamic stability of the turboshaft engine. Thus, the assessment of the availability of stability margin for special operating conditions in the envelope of this equipment is required to guarantee flight safety. In this paper, a rapid nonlinear complete engine method is developed to investigate the effect of helicopter ground-effect operation and high-altitude hovering on aerodynamic stability by considering factors including inlet distortion and component matching. Research indicated that the most dangerous point of stability margin in a unique section of the flight envelope is high altitude hovering, with about a 16.7% reduction in available stability margin compared to standard ground test conditions. This paper also investigates the effects of typical helicopter ground effects on a turboshaft engine and shows that the stability margin will be reduced by a maximum of 1.43% in hovering if the influence of ground effects in the flight envelope is not considered in the design.

Effects of different tooth grinding procedures on the occurrence of tooth injuries, skin lesions, performance and behaviour of suckling piglets

BackgroundImmediately after birth, newborn piglets fight to establish a teat order. During this process, lesions appear on the piglets’ faces and on the sows’ teats, which is why tooth resection is carried out on many farms in Germany even though it is known that this procedure is frequently resulting in pulp openings. The opening of a pulp cave is suspected to cause painful tooth alterations and may be an entrance for infectious agents. The purpose of this study was to analyse the effect of tooth resection on skin lesions, development of bodyweight and behaviour in suckling piglets. Four days prepartum, 110 sows in farrow-to-finish production were assigned to one of three treatments. Litters had their teeth left intact (control group, CG), ground with a tea-cup roller head (Tea-cup head grinder group, TCG, Wilofa Diamant, D-56,133 Fachbach, Germany) or ground with a diamond rolling head (rolling head grinder group, RG, IBS/E Company Proxxon GmbH, 54,343 Föhren, Germany). The number of pulp openings in the RG and TCG was examined using a random sample. Piglet body weight and skin lesion scores were recorded within the first 24 h after birth and during each week of the suckling period. Each sow’s udder was examined before farrowing, in the second week of lactation and at weaning. The behaviour of the litters from nine sows was video-recorded throughout the suckling period. The aim of this study was to investigate the effects of tooth grinding by a tea-cup head (compared to grinding by a diamond roller head and no grinding [control group]) on the behaviour and average daily gain of piglets as well as on skin lesions on sow udder.ResultsThe number of dental injuries was significantly greater in the RG than in the TCG (p < 0.01). Head lesions on piglets were significantly more common in the CG than in the RG (p = 0. 02). Compared to CG piglets, TCG piglets had a significantly greater weight at the end of the suckling period (p = 0.02). No significant difference between treatments was found in the sows’ udder (parenchyma, skin, or teat) or in the behaviour of the litters.ConclusionAs tooth grinding is frequently inducing pulp openings, the necessity of the procedure should be carefully and critically scrutinised. In case tooth resection seems inevitable until the underlying management problems have been solved, the Tea-cup grinding head should be used due to significantly fewer pulp openings.

Detecting differences in starch digestibility using in vitro methods among corn hybrids harvested at silage maturities

The objectives were to 1) determine whether genetic differences can be detected for carbohydrate fermentability among corn hybrids at silage maturities when the effects of drying and grinding are eliminated and 2) determine if in vitro starch digestibility (IVSD), a routine laboratory method used by commercial laboratories for hybrid evaluation, can detect differences when DM is controlled. Samples of whole corn plants from 3 hybrids (Brevant): B99B79SX (BMR, n = 7), B96T79SX, standard (STAN, n = 6), and B95U78SXE, floury-BMR (FL, n = 7), that had similar range of DM were selected. Sets of 8 ears were harvested concurrently and kernels removed from the ears by hand. Samples of undried kernels were quartered (QKERN) and in vitro gas production (IVGP) was measured for 120 h. More gas was produced by QKERN of FL than of STAN and BMR from 9 to 18 h (P < 0.05), and QKERN of FL produced more gas than BMR through 21 h (P < 0.05). The QKERN of FL had a shorter lag than STAN or BMR (P < 0.001) and a faster rate of gas production than BMR (P < 0.01), establishing that genetic differences are present at silage maturities. To determine whether the routine laboratory method can detect these differences, kernels (GKERN) and whole corn plants (GWP) were dried and ground to pass a 4-mm screen to measure IVSD after 3, 8, and 24 h. Particle size of GKERN was determined by dry sieving using a set of 13 sieves. For both GKERN and GWP, IVSD was lowest for BMR and highest for FL after 8 h. The IVSD8h of GKERN decreased as particle size increased at a similar rate for the 3 hybrids but the intercepts were different, with BMR being lowest and FL highest. Similarly, the IVSD8h of both GKERN and GWP decreased with increasing whole plant DM at a similar rate for the 3 hybrids and the magnitude of difference for IVSD8h was larger for the range in DM than the range in intercepts for the hybrids (0.123 vs 0.071 and 0.117 vs. 0.100, for GKERN and GWP, respectively). Plant maturity, or DM, has a larger effect on IVSD than hybrid type, and should therefore be controlled when evaluating genetic differences.

Aerodynamic and aeroacoustic characteristics of rocket sled under strong ground effect

Rocket sled test avoids boundary effects in wind tunnel test and inconvenience of flight test, which is one of the feasible options for future single-stage-to-orbit. To analyze potential safety issues during payload separation and optimize the arrangement of testing sensors, different structural layouts and operating speeds of the rocket sled are conducted based on computational fluid dynamics and computational aeroacoustics. The hypersonic winged standard model is utilized as the load for these simulations. The analysis encompasses the evolution of shock waves, the forces exerted on the payload and noise propagation. Variations in flow field and aeroacoustic characteristics of rocket sled are analysed, revealing underlying physical mechanisms. It is observed that placing the payload in front of the thruster can reduce the head pressure, excessive wingspan may have an impact on the structural safety of the wingtip, and the regions of high sound pressure levels mainly exists in the middle and rear sections of the rocket sled. Moreover, as the Mach number increases, the characteristic frequency initially rises and then declines. These researches can serve as a valuable reference for the development of ground test systems and single-stage-to-orbit.

Sensors Layout Optimization Design of Rocket Sled Test System.

The rocket sled, as a ground dynamic test system, combines the characteristics of the wind tunnel test and the flight test. However, some practical factors, such as shock wave interference, ground effect, and high-intensity aerodynamic noise will cause serious interference and even failure of the uniformly distributed sensors during horizontal sliding in a wide speed range. The AGARD HB-2 standard model is employed as the payload to simulate the aerodynamic and aeroacoustic characteristics during the variable acceleration period, aiming to optimize the test sensors layout. It is observed that in the high Mach number flow fields, strong coupling behaviors among complex waves will occur. The peak of wake vortex strength will appear at 1.5 s and gradually diminish over time. In addition, when the vortex between the load and the booster is monitored, its position shifts forward in the subsonic stage, then gradually moves backward and expands in the supersonic stage. Acoustic directivity is pronounced at subsonic and transonic speeds, pointing towards 75° and 135° relative to the sliding speed, respectively. These results can provide technical support for sensor layout and high-precision testing in rocket sled tests.

Effects of superfine grinding Tremella fuciformis stem on the texture and quality of dough for steamed bun

Tremella fuciformis (TF) stem accounts for about 10% of the whole mushroom, and most of them are dumped without utilization. To effectively utilize the waste, the effects of fine grinding and superfine grinding technology on the processing characteristics and physicochemical properties of Tremella fuciformis stem powder (TFSP) were investigated, and the effects of TFSP on the quality of steamed bun were analyzed. The findings indicate that the specific surface area of superfine Tremella fuciformis stem powder (STFSP) is 1.6 times larger than that of fine Tremella fuciformis stem powder (FTFSP). Despite this, the infrared spectra of STFSP and FTFSP are similar. The water solubility index and oil holding capacities of STFSP saw an increase of 18.81%, whereas its water holding capacity decreased by 11.34%. Superfine grinding not only enhanced the processing characteristics but also stabilized the powder form. Moreover, steamed buns incorporating 4% STFSP were judged to have the optimal taste. Superfine grinding significantly influences the physicochemical properties of TFSP, resulting in enhanced quality of steamed buns.

The future and technique challenges of high-speed ground effect vehicle enrolled in maritime transportation

This paper presents a high-speed ground effect vehicle (HS-GEV) used specifically for maritime transportation. Given the limitations of current vessels, including various types of watercraft and high-speed boats, in fulfilling of needs in different maritime transportation scenarios, the HS-GEV emerges as a promising solution to address unmet requirements. To efficiently accomplish maritime transportation missions with quickness and safety, several critical features are emphasized, including short take-off on water, flight maneuverability and flight stability. The key techniques required to achieve these features, as well as recent progress highlights, are introduced. Following and promoting these crucial techniques is also suggested as a future step to improve HS-GEV performance. With its predominant features, the HS-GEV holds immense application value in enhancing a high-speed maritime transportation system that aligns with the evolving needs of the real world.

Dynamic response of a wind turbine wake subjected to surge and heave step motions under different inflow conditions

The development of floating offshore wind turbines poses new challenges since the floating platform introduces complex dynamics in the wind turbine wake. These wake dynamics are intricately tied to the advection velocity, referring to the velocity of the downstream propagation of the air flow, and used in the context of wind farm modelling. The present article investigates the far-wake dynamic response of a wind turbine model subjected to heave (up-down translation) and surge (fore-aft translation) step motions under two distinct inflow conditions. Wind tunnel experiments were conducted with hot-wires in a realistic turbulent inflow and a low shear and no ground effect inflow, achieved by varying the hub height of the wind turbine model in the atmospheric boundary layer developed in the test section. The results show that the dynamic response of the wake under the low shear and no ground effect inflow conditions aligns with a second-order system with the presence of undershoots and overshoots. In contrast, under realistic conditions, it appears like a first-order system with undershoots and overshoots less evident in most cases. Despite these variations the determined advection velocity remains roughly the same and consistent with the literature for both heave and surge step motions, regardless of the inflow conditions.

A fuel-efficient pathfinding algorithm for next-generation WIG crafts

ABSTRACT Wing-In-Ground (WIG) crafts have the advantage of being fuel-efficient by utilising the ground effect. Next-generation WIG crafts can choose flight paths that navigate over obstacles while flying at specific altitudes. However, current route computation algorithms for ships fail to account for paths that allow ships to navigate over obstacles. Leveraging fundamental path-finding approaches such as A* and Jump Point Search (JPS), our algorithms are designed to forecast routes that significantly improve operational efficiency. Validation was performed using real topographic data from Indonesia, focusing on fuel consumption metrics to evaluate the algorithms’ effectiveness. The results evaluate the superiority of our methods in optimising route selection for WIG crafts, marking a advancement in autonomous marine navigation technology.

The way to maintain the stability of race cars at high speed

Nowadays, cars are used quite often and require good stability and handling while driving to keep passengers safe. At the same time, the race car also must have better stability and handling at high speeds than family cars so that they can ensure that the driver can handle the track and get the best performance in extreme conditions. Therefore, the shape of the vehicle and the design of the different components play a key role in ensuring its stability at high speeds. From an aerodynamic point of view, the streamlined body design, the application of spoilers, the design of the tail and the ground effect are all factors that are crucial to the stability of the car. This paper will look at how the race car remains stable at high speeds from an aerodynamic perspective, and how its shape and different components of the car affect its stability and handling. From our research, we find that all of them have crucial effects and exist different forces on the car body

The Effects of Drying and Grinding on the Extraction Efficiency of Polyphenols from Grape Skin: Process Optimization

The Effects of Drying and Grinding on the Extraction Efficiency of Polyphenols from Grape Skin: Process Optimization

Segregation in binary and polydisperse stirred media mills and its role on grinding effectiveness

Most industrial vertical stirred mills contain a non-uniform set of grinding media sizes. However, this fact is often ignored in simulations, which mostly use monodispersed media. The paper explores the fundamental dynamics of vertical mills when using multiple sizes of grinding media, by using DEM simulation. Our results suggest that by including both large and small media, one may be able to optimise its performance in several manners. The energy going into the contacts can be increased by including a second size, leading to more effective grinding. Including smaller media can also reduce the power draw of the mill, increasing the efficiency and sustainability of the mill. Finally, the natural segregation between different sizes creates different types of collision which grind different particle sizes more effectively. Segregation leads to smaller media at the bottom, so continuous processes can be optimised for fine grinding by feeding from the top, where the larger media are. This further enables control of the resulting product specifications.

Preparation of microfibrillated cellulose by in situ and one step method using calcium hydroxide as swelling and grinding agent

Abstract Calcium hydroxide was used as a swelling agent and grinding aid to grind together with cellulose raw materials to prepare microfibrillated cellulose (MFC). Carbon dioxide was introduced to obtain MFC coated with calcium carbonate (CMFC). The effect of calcium hydroxide dosage on the fibrillation process of cellulose materials and the characteristics of MFCs and CMFCs were studied. Results show that when the dosage of calcium hydroxide was 5 % (based on cellulose materials), calcium hydroxide could be completely dissolved in water and had a swelling effect on cellulose materials. When the dosage reached 10 %, undissolved calcium hydroxide particles could serve as grinding media to assist in the fibrillation of cellulose materials. When the dosage exceeded 50 %, the auxiliary grinding effect of calcium hydroxide was more obvious. After accelerated carbonation, the generated calcium carbonate nanoparticles were coated on the surface of MFC, which increased its viscosity and decreased water retention value. The presence of calcium carbonate also facilitated the concentration, redispersion, and drying of MFC. The pretreatment, mechanical fibrillation, and accelerated carbonation were carried out in the same equipment without the need for heating or washing. Therefore, this study provides a in situ and one step method for the preparation of MFC.

Applied Research Note: Effects of grinding and pelleting Kernza grain on subsequent particle size, flowability, and pellet durability index

Applied Research Note: Effects of grinding and pelleting Kernza grain on subsequent particle size, flowability, and pellet durability index

Mechanistic study of the effects of ultrafine grinding on the surface properties of anthracite coal particles and interface regulation on froth flotation under multifactorial influences

Anthracite, a valuable and scarce coal, typically requires systematic liberation for deep deashing, wherein the particle size reduces to the micron level upon ultrafine grinding. Changes in the physicochemical properties of anthracite particles induced by ultrafine grinding significantly impact subsequent flotation. Accordingly, in this study, a scanning electron microscopy (SEM)-energy-dispersive X-ray spectroscopy (EDS) system, an Opton IPCAS maceral analyzer, a high-sensitivity microelectromechanical balancer, and an X-ray photoelectron spectrometer (XPS) were employed to investigate the changes in the physicochemical properties of the anthracite particle surface during ultrafine grinding. The flotation efficiency of ultrafine anthracite coal is determined by various factors such as the extent of sample liberation, surface wettability, and the state of inorganic mineral coatings. During the initial phase of ultrafine grinding, the comminution efficiency of the sample is high, leading to a progressive increase in the hydrophobicity. However, suboptimal flotation performance results from inadequate liberation. When the sample is liberated to an ultrafine scale, a higher degree of liberation is achieved. The particle surfaces become increasingly covered with inorganic minerals, accompanied by intensified oxidation, leading to a gradually reduced particle hydrophobicity that impaired the flotation performance. This study advances our knowledge on the mechanism by which ultrafine grinding alters the physicochemical properties of anthracite coal particles and affects the flotation processes. The theoretical framework of this study provides crucial insights for interface regulation in the preparation of ultra-low ash anthracite coal and ultrafine coal flotation.