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We consider a cylinder immersed in viscous fluid moving near a flat substrate covered by an incompressible viscoelastic fluid layer, and study the effect of the fluid viscoelasticity on the lift force exerted on the cylinder. The lift force is zero when the viscoelastic layer is not deformed, but becomes non-zero when it is deformed. We calculate the lift force by considering both the tangential stress and the normal stress applied at the surface of the viscoelastic layer. Our analysis indicates that as the layer changes from the elastic limit to the viscous limit, the lift force decreases with the decrease of the Deborah number (De). For small De, the effect of the layer elasticity is taken over by the surface tension and the lift force can become negative. We also show that the tangential stress and the interface slip velocity (the surface velocity relative to the substrate), which have been ignored in the previous analysis, give important contributions to the lift force. Especially for thin elastic layers, they give dominant contributions to the lift force. [ABSTRACT FROM AUTHOR]

As train speeds increase, the aerodynamic effects generated during the passage of high-speed trains in tunnels become more pronounced. This article investigates the influence of line spacing on the aerodynamic forces during the passage of high-speed trains in tunnels at different speeds. The research methodology is based on the three-dimensional transient compressible Reynolds-averaged Navier-Stokes (RANS) equations and the k-ω Shear Stress Transport (SST) turbulence model, using overset grid technology to simulate the train passing process in the tunnel. The results show that the aerodynamic drag, lateral force, and lift experienced by the train increase as the line spacing decreases and as the speed increases. line spacing has the greatest impact on aerodynamic lift, followed by lateral force, with drag having the smallest impact. Compared to line spacing, speed has a much larger effect on aerodynamic forces. The aerodynamic forces experienced by the train during tunnel passage are proportional to the square of the train's speed and have an exponential relationship with the line spacing during train passage. [ABSTRACT FROM AUTHOR]

Satellites in very low Earth orbits can leverage the aerodynamics forces for control purposes. Three-axis attitude control can be achieved by adjusting the orientation of aerodynamic surfaces, benefiting from both drag and lift forces. However, complete control over the orbital motion of a satellite is unattainable using aerodynamic forces alone, as positive thrust cannot be generated. Nonetheless, this limitation does not apply when focusing on the control of a satellite formation. By properly modulating the orientation of panels, positive and negative relative forces can be generated. This paper shows that even in a formation of simple microsatellites, it is possible to achieve formation and attitude simultaneous control by using no other actuators than the aerodynamics surfaces. • Very Low Earth orbits are appealing but the large atmospheric density can be a problem. • The atmospheric forces can be used for control purposes. • Formation control and attitude control can be individually realized by using aerodynamic forces. • A GNC architecture is implemented to realized both goals with the same aerodynamic actuators. • Performance in keeping or acquiring a desired state (attitude and relative position) is promising. [ABSTRACT FROM AUTHOR]

The vortex-induced vibration (VIV) problem has been of critical concern for the wind-resistance of long-span bridges. Usually there are four types of approach for VIV studies: wind tunnel tests, field monitoring, computational fluid dynamics and mathematical models. However, traditional approaches have shown some limitations, such as high cost and low efficiency. In order to improve the efficiency and accuracy of VIV studies, this article has taken the VIV problem of a split three-box girder in a cable-stayed and cooperative suspension system bridge as an instance, and conducted a series of VIV wind tunnel tests. An approach based on machine learning is described that is able to serve as a complement to the wind tunnel tests. The proposed approach involves two steps: firstly, based on the dataset produced by wind tunnel tests, a clustering algorithm is introduced to separate the VIV signals automatically from other vibrations. Then, an artificial neural network is utilized to recognize the VIV response and aerodynamic force in the lock-in region directly. It is shown that the clustering algorithm can be a good tool for the recognition of VIV signals. Moreover, the proposed artificial neural network models show good ability for recognizing VIV amplitude and aerodynamic lift force. [ABSTRACT FROM AUTHOR]

When a flying vehicle approaches a water or land surface, it induces changes in the fluid flow field pattern known as the "ground effect." This research analyzes the ground effect phenomenon, exploring its impact on aerodynamic coefficients and flow patterns around the NACA0012 airfoil in an incompressible subsonic regime under static and dynamic conditions with pitch movements. Numerical simulations and experimental testing in an incompressible subsonic wind tunnel were deployed. The flow field solution is derived from the Navier-Stokes equations, incorporating the Transition SST turbulence model. Initially, the impact of the ground effect phenomenon was investigated at varying distances from the surface in the static state. Subsequently, the airfoil underwent a sinusoidal pitching oscillation at each distance with a specified frequency and amplitude. This allowed for examining its aerodynamic characteristics over time. The static analysis results reveal alterations in the curve's behavior and pressure distribution on the airfoil surface at close distances to the surface. This is attributed to the ground effect phenomenon, which reduces lift force to a certain height and then increases. Dynamic analysis further demonstrates changes in lift coefficient oscillation amplitude. It also exhibits a minimum and maximum lift point phase difference as the airfoil approaches the surface. [ABSTRACT FROM AUTHOR]

The bogie is a critical component of high-velocity trains. As train velocity rises, the operational quality is increasingly influenced by aerodynamic forces. The aerodynamic characteristics of bogies significantly impact the safety of train operations. This article examines a real high-velocity train model, constructing a 3-group train model, and developing a mathematical model of high-velocity train operation on open lines. Using three-dimensional steady-state Navier–Stokes equations, the flow field characteristics, pressure spread, aerodynamic forces, and torque characteristics on the bogie and body of high-velocity locomotives operating at velocities of 200 km/h, 250 km/h, 300 km/h, and 350 km/h are calculated, with measurement spots set to study the trend of pressure variation with train velocity. The research findings indicate that pressure at the same location on the body surface rises with vehicle velocity, with a quadratic link between the two. The uneven pressure spread between two bogies of the same vehicle and between two axles of the same bogie indicates that aerodynamic forces can cause axle load transfer in high-velocity trains. The highest values of aerodynamic resistance and lift happen at the front bogie, and the resistance and lift of both a single carriage and the entire vehicle increase with velocity, following a quadratic relationship. The highest nodding torque of the train body occurs on one vehicle, while the highest nodding torque of the bogie occurs on the 6th bogie, with both torques increasing with velocity, also in a quadratic relationship. [ABSTRACT FROM AUTHOR]

In order to study the influence of the lifting force arrangement on the mechanical performance of the long-span steel-concrete composite girder which using the lifting-composing construction method, based on the Qinhe grand bridge along the Taihang expressway, the effects of different first and secondary lifting force, the number and distance of lifting points on the stress, deformation, stability, and bridge deck compressive stress reserve of the steel-concrete composite girder were studied by using the Midas-Civil finite element software and a control variable method. The sensitivity of different factors on the steel-concrete composite girder was analyzed through variable normalization, moreover, the optimal scheme was selected, and the implementation effect was monitored on site. The results show that the stress of upper flange of the steel girder, bridge deck, and bridge deflection are most sensitive to the secondary lifting force, with sensitivities of 0.61, 1.95, and 0.16, respectively. The stress of lower flange of the steel girder is most sensitive to the number of lifting points, with a sensitivity of 0.20. The theoretical optimal pre-bending of Qinhe grand bridge is 78%, the final scheme arranges 5 groups of lifting points with distance of 11 m, and the first and the secondary lifting forces are 1 500 kN and 6 500 kN, respectively. The on-site monitoring results show that the construction effect of the scheme is consistent with the theoretical analysis results, and the on-site lifting force is reasonably arranged. The on-site monitoring results show that the implementation effect of the scheme is consistent with the theoretical analysis, and the lifting force is reasonably arranged. The research results can provide reference for similar projects. [ABSTRACT FROM AUTHOR]

Self‐supporting concrete shell structures are highly efficient in distributing loads, which can result in very reduced thicknesses (ultra‐thin), giving them remarkable slenderness. Due to their geometric complexity, it is difficult to predict how they interact with wind action. The main aim of the present study is to assess the mean surface pressure coefficient distribution in a shell with a triangular plan shape and three supports for different angles of wind incidence. To determine the distribution of surface pressure coefficients and lift and drag force coefficients, an experimental study was carried out in a wind tunnel, and a numerical simulation study was performed through computational fluid dynamics. The experimental and numerical results were analyzed and compared, and making it possible to identify the most critical surface zones and wind incidences when the shell is under the wind action. [ABSTRACT FROM AUTHOR]

ABSTRACT Although the presence of early helping behavior has been firmly established, it is unclear to what extent children are willing to adopt costs to help others, as well as how this willingness changes as children get older. Canadian 21‐ to 36‐month‐olds (N = 48) participated in four helping tasks varying in the type and degree of effort required to help (lifting force, cognitive load, the number of steps in a task, and pushing force). When costs were lower, toddlers were not only more likely to help but also provided help more readily and helped in ways that prioritized others’ needs. Importantly, we found that age and how costly helping was to individual children each uniquely predicted high‐cost helping, but not low‐cost helping. Overall, we demonstrate that toddlers’ helping is sensitive to a variety of effortful costs, while simultaneously demonstrating that maturation and individual costs appear to uniquely influence high‐cost helping. [ABSTRACT FROM AUTHOR]

Direct numerical simulations are performed to investigate the characteristics of a turbulent core–annular flow with water-lubricated high viscosity oil in a horizontal pipe. Six different superficial velocity ratios ($\,j_w/j_o = 0.057\unicode{x2013}0.41$) are examined by changing the water superficial velocity $j_w$ for a fixed oil superficial velocity $j_o$. The pressure drops in the pipe and the shapes of the phase interface agree well with those from previous experiments. The oil core flow is almost a plug flow, and the gaps between the phase interface and pipe wall are narrow and wide near the upper and lower surfaces of the pipe, respectively, due to the buoyancy. Within a narrow gap, water is confined mostly in a valley region of the wavy phase interface and hardly goes through its crest. On the other hand, water near the phase interface at a wide gap convects downstream almost at the core speed and the flow near the wall is similar to that of single-phase wall-bounded turbulent flow. The annular flow is characterized by three different regimes depending on the clearance Reynolds number ($Re_c$) based on the core velocity and local gap size: laminar Couette flow driven by the core for $Re_c \le 600$ , transitional flow for $600 and turbulent flow for $Re_c \ge 2500$. The minimum pressure drop occurs at $j_w/j_o = 0.11$ in the early transition regime. For all $j_w/j_o$ considered, the negative lift force acting on the core comes from the pressure force which balances the buoyancy. [ABSTRACT FROM AUTHOR]

The transient processes of laminar separation bubble (LSB) formation and bursting on a rectangular NACA 0018 wing are studied experimentally. A two-dimensional airfoil model is used as a baseline for the assessment of finite wing effects. The models are subjected to ramp changes in free-stream velocity causing the flow to switch between a state where an LSB forms and a state without reattachment. Lift force and particle image velocimetry measurements are used to relate the flow development to the aerodynamic loading. The lift coefficient of the airfoil exhibits substantial hysteresis, and the duration of the lift transients range from $10$ to $22$ convective time scales for bubble formation and $22$ to $30$ convective time scales for bursting. In contrast, the transient lift coefficients of the wing change gradually, with less hysteresis. The wing tip causes greater three-dimensionality in the separation bubble, whose thickness increases near the midspan where bursting is initiated. During bubble formation, the region of separated flow contracts towards the midspan. The gradual change in lift of the wing is linked to slower spanwise expansion and contraction of the separated flow region relative to the airfoil. On both models, the wavenumbers and amplitudes of disturbances in the separated shear layer rapidly change when reattachment initiates or ceases. Applying the bursting criterion of Gaster (Tech. Rep. Reports and Memoranda 3595. Aeronautical Research Council, London, 1967) to the bubble on the wing shows that bursting of the bubble at a single spanwise location is insufficient to cause complete spanwise failure of reattachment, and that the relationship between bursting parameters depends on spanwise position. [ABSTRACT FROM AUTHOR]

Birds employ rapid pitch-up motions close to the ground for different purposes: perching birds use this motion to decelerate and come to a complete stop while hunting birds, such as bald eagles, employ it to catch prey and swiftly fly away. Motivated by these observations, our study investigates how natural flyers accomplish diverse flying objectives by rapidly pitching their wings while decelerating near ground. We conducted experimental and analytical investigations focusing on rapidly pitching plates during deceleration in close proximity to the ground to explore the impact of ground proximity on the unsteady dynamics. Initially, we executed synchronous pitch-up motion, where both pitching and deceleration have the same motion duration, at different ground heights. Experimental results demonstrate that as the pitching wing approaches the ground, the instantaneous lift increases by approximately $38\,\%$ compared with a far-from-ground case, while the initial peak drag force remains relatively unchanged. Our analytical model conforms to this trend, predicting an increase in lift force as the wing approaches the ground, indicating enhanced added mass and circulatory lift force due to the ground effect. Next, we examined asynchronous pitch-up motion cases, where rapid pitching motions were initiated at different stages of deceleration. The results reveal that initiating the wing pitch early in the deceleration leads to the formation of larger counter-rotating vortices at the early stage of the manoeuvre. These vortices generate stronger dipole jets that orient backward in the later stages of the manoeuvre after impinging with the ground surface, which hunting birds utilize to accelerate after catching prey. Conversely, when the wing pitch is delayed, smaller vortices form, but their growth is postponed until late in the manoeuvre. This delayed vortex growth produces lift and drag force at the end phase of the manoeuvre that facilitates a smooth landing or perching. Thus, through strategic tuning of a rapid pitch-up motion with deceleration, natural flyers, such as birds, achieve diverse flying objectives. [ABSTRACT FROM AUTHOR]

During the retrieval process of the deep-sea mining vehicle (DSMV), the stability of the retrieval system is strongly influenced by the interaction between the vehicle body and the surrounding seawater due to the vehicle's complex shape and wave motion. Naturally, the negative side effects of significant changes in the vehicle's attitude and the water exit position can only increase retrieval's challenge. To investigate the characteristic of the flow field of the DSMV, this study employs the computational fluid dynamics method based on the Reynolds-averaged Navier–Stokes equations integrating the volume-of-fluid multiphase flow model with a fifth-order Stokes-wave model to explore the attitude and displacement changes of the vehicle during the water exit process in the ocean wave environment. The results indicate that the wave phase and lifting force are the major effect factors in the DSMV's water exit process. An appropriate lifting force under a specific wave phase can effectively reduce attitude changes and positional drift of the DSMV during water exit, thereby enhancing recovery efficiency and stability. [ABSTRACT FROM AUTHOR]

Previous studies of two-dimensional (2D) aerodynamic admittance function (AAF) identification methods have basically ignored the effects of different turbulence components, which may lead to unpredictable errors for practical engineering applications. This paper presents pressure measurement experiments on thin sections with a geometric ratio of 1:50 in various turbulent fields. Based on the three-dimensional (3D) two-wavenumber theoretical analytical framework, the two-wavenumber coherence function is obtained by fitting the measured spanwise root-coherence function at the effective spacing with an empirical model. A new method is proposed, assuming that the ratio relationship between the lift AAFs due to longitudinal and vertical turbulence components of the measured model section satisfies its corresponding theoretical solution ratio relationship. The 2D lift AAFs of the airfoil section induced by different turbulence components are identified following the proposed identification framework. Consistent with the previous research, force correlation is significantly larger than turbulence correlation, and the traditional 3D one-wavenumber AAFs obtained are different in different turbulent fields. The separated 2D lift AAFs demonstrate that the contributions of u- and w- turbulence to the buffeting lift force are significantly different, and are more precise, according to the ratio between the Horlock function and Sears function. Then, the method is successfully extended to estimate the AAFs with respect to the u- and w-turbulence components of a streamlined box girder section, further validating the applicability of the identification method to the streamlined box girder. Furthermore, comparing the separated 2D lift AAFs under different turbulence fields reveals their independence from turbulence characteristics. [ABSTRACT FROM AUTHOR]

To investigate the hydrodynamic performance and motion characteristics of the ultra-high-speed aerodynamically alleviated marine vehicle (AAMV) with multi-steps, a towing tank test scheme was designed and carried out at the China Special Vehicle Research Institute. The study analyzed the effects of canard angle, flap angle, longitudinal center of gravity, and displacement tonnage on the motion stability of multi-stepped AAMV at different speeds. The results indicate that the canard generates an overturning moment that reduces the resistance but brings forward the speed at which porpoising behavior occurs. Additionally, the backward shift of the longitudinal center of gravity causes motion oscillation during the high-speed planing phase, which negatively affects longitudinal stability. On the other hand, the flaps provide aerodynamic lift and restoring moments, improving the lift-drag ratio and enhancing longitudinal stability. Furthermore, while increased mass may result in higher total resistance, it can actually improve resistance performance per unit mass and improve the lift-drag ratio at cruising speed. The computational fluid dynamics (CFD) method was used to analyze the destabilization mechanism of AAMV under extreme conditions in the test. Numerical results indicate that the longitudinal stability of AAMV is directly affected by the relative positions of the center of gravity and the center of pressure. These results demonstrate the changing rules of resistance performance and longitudinal stability of AAMV under different design parameters, thus providing a powerful tool for optimizing AAMV. [ABSTRACT FROM AUTHOR]

Double-row hydraulic collectors are extensively utilized for deep-sea polymetallic nodule harvesting. Understanding the movement behavior of particles within the flow field is crucial for evaluating the efficiency collection system and guiding the design of deep-sea hydraulic collectors. This study first investigates the settling characteristics of particles in various deep-sea environments to assess the effects of high-pressure and low-temperature conditions on particle motion. Subsequently, the motion and force characteristics of particles under different double-row jet parameters were measured and analyzed in the laboratory using high-speed imaging. The results indicate that ambient pressure has a negligible effect on particle motion when the ambient temperature is considered. Particle is mainly lifted in an irregular spiral path by the turbulence of the upper fountain. The lifting height or force of a particle in the vertical direction is positively correlated with the frequency of horizontal fluctuations and inversely related to the average amplitude of these fluctuations. Finally, a neural network was constructed to predict the particle motion characteristics, demonstrating strong generalization and providing a reference for further use of artificial intelligence in extracting physical information of particles from the jet field. This study offers potential benefits for optimizing the design of the double-row jet collectors. [ABSTRACT FROM AUTHOR]

This study is focused toward the analysis of fluid dynamics associated with the clap-and-fling motion of insect wings. In this regard, a numerical framework based on a moving non-uniform grid block and the multi-relaxation time lattice Boltzmann method is utilized. This study investigates the impact of key kinematic parameters such as angle of attack α 0 ( 20 ° – 50 °), percentage overlap between pitching and sweeping ξ (0 % – 100 %), and the Reynolds number Re (20 – 200), on the aerodynamic lift, drag, and power requirements. A data-driven reduced order model is proposed that accurately predicts the instantaneous lift [ C L (t) ] and drag [ C D (t) ] that enabled a parametric analysis of their cycle-averaged or mean values. Based on this analysis, ξ is identified as the most influential parameter for enhancing lift, while Re is most effective in reducing power and drag. The leading and trailing edge vortices during the pitch and sweep phases play a crucial role in directly affecting C L (t). These effects are highlighted for various parameters through the examination of vortex patterns and pressure contours. Wing–wake interaction is found to augment cycle-averaged lift as ξ increases but is detrimental at high values of α 0 . Additionally, a set of Pareto-optimal solutions representing the ideal kinematics that maximize lift for a given input power is presented, offering valuable insight for the design and advancement of future flapping wing aerial vehicles. [ABSTRACT FROM AUTHOR]

In this study, computational fluid dynamic (CFD) simulation of a vertical axis wind turbine (VAWT) geometry based on the Unsteady Reynolds–Averaged Navier–Stokes equations was investigated. In addition, the relationship between the geometric parameters of the VAWT and the two response variables, that is, moment and lift force, was determined using response surface methodology (RSM). Then, the Non‐Dominated Sorting Genetic Algorithm (NSGA‐II) was used to solve the multi‐objective optimization problem. The results obtained from the RSM showed that the lift force of the turbine is more sensitive to the change in the blade chord length, and the output moment of the turbine is more sensitive to the change in the rotor radius. Using the NSGA‐II multi‐objective optimization algorithm and the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method, it was determined that among the optimal values of the independent variable, the most optimal response occurs in blade chord length = 0.18 m, rotor radius = 0.4 m, blade pitch angle = −3.27° and number of blades = 4. In these optimal values of the independent variables, the values of the dependent variables, which included the turbine's moment and the blades' lift force, were obtained as 9.58 N m and 57.89 N, respectively. [ABSTRACT FROM AUTHOR]

This study investigates the effects of positive horizontal acceleration of the freestream velocity on a pitch‐oscillating VR‐12 airfoil using computational fluid dynamics. The shear stress transport k–ω model, coupled with a low‐Reynolds number correction, was employed for Re <105 during dynamic stall. The flow equations were solved in two‐dimensional, incompressible form using the finite volume method. The study examined various parameters, including positive acceleration values of the inflow and the angle of attack of the airfoil, to determine their impact on lift and drag coefficients, as well as the Cl/Cd ratio. Additionally, the maximum lift coefficient was analyzed under different inflow and airfoil motion conditions. The results indicate that aerodynamic force coefficients and the Cl/Cd ratio are influenced by both the attack angle and the acceleration of the inflow. Furthermore, inflow acceleration affects the onset of dynamic stall conditions. Generally, inflow acceleration modifies the lift coefficient of the airfoil during the upstroke, while having minimal effect on the drag coefficient, except near dynamic stall points. The findings also suggest that, for a specific airfoil, the sequence of factors with the greatest influence on lift force generation before static stall occurs is as follows: asymmetric airfoil oscillation, symmetrical airfoil oscillation, accelerated inflow, constant velocity inflow, and static airfoil. [ABSTRACT FROM AUTHOR]

Offshore floating photovoltaic (FPV) systems are subjected to significant aerodynamic forces, especially during extreme wind conditions. Accurate estimation of these forces is crucial for the proper design of mooring lines and connection systems. In this study, detailed CFD simulations were performed for various PV panel configurations, and using these CFD simulation correlations were developed to estimate lift and drag forces as a function of the number of panels. These correlations provide valuable tools for designing large-scale FPV systems with multiple PV modules. Additionally, this study investigates the potential of using breakwaters to reduce aerodynamic forces on FPV systems. Breakwaters, typically used to mitigate wave impacts, can also serve as wind barriers, significantly reducing wind forces before they reach the FPV array. Aerodynamic simulations with and without a breakwater were conducted using CFD to assess this effect. The results show a substantial reduction in lift and drag coefficients, especially for angles of attack up to 10 degrees, demonstrating the effectiveness of the breakwater in protecting the FPV system. However, beyond this threshold, the effectiveness of the breakwater of 2 m reduces. These findings highlight the importance of strategic breakwater placement and heights and their role in enhancing FPV system resilience. The insights gained from this study are critical for optimizing breakwater design and placement, ensuring the structural integrity and performance of FPV systems in varying environmental conditions. The data generated will also contribute to future design improvements for floating PV systems. [ABSTRACT FROM AUTHOR]

The colonization of the pelagic realm by the vertebrates represents one of the major transitions in the evolutionary success of the group and in the establishment of modern complex marine ecosystem. It has been traditionally related with the Devonian rise of jawed vertebrates, but new evidences indicate that first active swimmers, invading the water column, occurred within earlier armoured jawless fishes ("ostracoderms"). These "primitive" fishes lacked conventional fish control surfaces and the precise mechanism used to generate lift and stabilizing forces still remains unclear. We show that, because of their shape, the rigid cephalic shield of Pteraspidiformes, a group of Silurian-Devonian "ostracoderms", generate significant forces for hydrodynamic lift. Particle Image Velocimetry and force measurements in a water channel shows that the flow over real-sized Pteraspidiformes models is similar to that over delta wings, dominated by the formation of leading-edge vortices resulting in enhanced vortex lift forces and delayed stall angles of attack. Additionally, experiments simulating ground effect show that Pteraspidiformes present better hydrodynamic performance under fully pelagic conditions than in a benthic scenario. This suggests that, lacking movable appendages other than the caudal fin, leading-edge vortices were exploited by earliest vertebrates to colonize the water column more than 400 Mya. Digital particle image velocimetry and force measurements in a water channel provide evidence that leading-edge vortices could be exploited by earliest vertebrates to colonize the water column more than 400 Mya. [ABSTRACT FROM AUTHOR]

Stick–slip is a standard friction-induced self-excited vibration that usually occurs in the boundary or mixed lubrication regimes. Broadening of the hydrodynamic lubrication regime is conducive to suppressing stick–slip motion. In this paper, the load carrying capacity of a magnetic fluid (MF) film in the presence of a magnetic field is derived based on the modified Reynolds equation. An additional lifting force produced by MF under the magnet was applied between the tribopairs to achieve the full fluid lubrication. Thus, the stick–slip is expected to be inhibited in a lower speed scope. The effect of magnet thickness on the lifting force is investigated experimentally and theoretically. Special attention is given to the influence of the lifting force on the friction and the critical transition speed of the hydrodynamic lubrication regime. Results demonstrate that the lifting force increases with the increment of the magnet thickness. The presence of the additional lifting force expands the hydrodynamic lubrication and makes the critical transition speed move left, as shown by the friction transitions on the Stribeck curve. Therefore, stick–slip motion can be suppressed at a lower sliding speed. Such beneficial effects are more pronounced in thicker magnets. It can be confirmed that, so long as the lifting force is higher than the normal load, the friction will invariably operate in the full film lubrication and the stick-slip motion may be eliminated theoretically. [ABSTRACT FROM AUTHOR]

In this paper, a forced vibration caused by drag and lift forces with time‐varying mass is studied. The construction of the model is conducted by adding impact force to the previous model. The periodicity of the solution is yet known. Hence, the model is seen as a perturbation problem. Since the unperturbed problem has a periodic solution, we applied the averaging method to determine the sufficient condition such that the limit cycle exists. [ABSTRACT FROM AUTHOR]

Turbulent flow physics regulates the aerodynamic properties of lifting surfaces, the thermodynamic efficiency of vapor power systems, and exchanges of natural and anthropogenic quantities between the atmosphere and ocean, to name just a few applications of contemporary importance. The space-time dynamics of turbulent flows are described via numerical integration of the non-linear Navier–Stokes equation—a procedure known as computational fluid dynamics (CFD). At the dawn of scientific computing in the late 1950s, it would be many decades before terms such as "carbon footprint" or "sustainability" entered the lexicon, and longer still before these themes attained national priority throughout advanced economies. The environmental cost associated with CFD is seldom considered. Yet, large-scale scientific computing relies on intensive cooling realized via external power generation that is primarily accomplished through the combustion of fossil fuels, which leads to carbon emissions. This paper introduces a framework designed to calculate the carbon footprint of CFD and its contribution to carbon emission reduction strategies. We will distinguish between "hero" and "routine" calculations, noting that the carbon footprint of hero calculations—which demand significant computing resources at top-tier data centers—is largely determined by the energy source mix utilized. We will also review CFD of flows where turbulence effects are modeled, thus reducing the degrees of freedom. Estimates of the carbon footprint are presented for such fully and partially resolved simulations as functions of turbulence activity and calculation year, demonstrating a reduction in carbon emissions by two to five orders of magnitude at practical conditions. Besides generating a carbon footprint, the community's effort to avoid redundant calculations via turbulence databases merits particular attention, with estimates indicating that a single database could potentially reduce CO2 emissions by approximately O(1) × 106 metric tons. [ABSTRACT FROM AUTHOR]

This study assesses flow-induced vibrations of clamped flexible plates with the objective of improving their energy harvesting performance. Toward this, a rectangular bluff body is placed between the two clamped flexible plates to harness the vortices generated behind the bluff body. The strain energy of the plate is used as a measure of energy harvesting performance. Computational studies are performed for different parameters of interest, such as dimensions and material properties of the plate and dimensions and locations of the bluff body. The effects of these stated parameters on flow-induced vibration response and vortical structures are investigated, and the optimal values for the location and geometry of the bluff body, as well as the aspect ratio and Young's modulus of the plate for energy harvesting performance, are determined. The results show that vortex shedding from the bluff body strongly influences the dynamic behavior and energy output of the flexible structures inside the wake region of the bluff body at different locations. Additionally, the aspect ratio and its effect on vorticity and energy harvesting are discussed in detail, along with the average displacement and average lift force experienced by the plates. The outcomes of this work offer significant insights into optimizing the design of clamped flexible plates for optimal energy generation by cleverly exploiting the vortex shedding behind fixed bluff bodies. [ABSTRACT FROM AUTHOR]

Marine midges, tiny insects with a body size of 2 mm and a weight of 0.07 dyn, provide valuable insights into advanced locomotion techniques. Found in shallow reefs at Wanlitong, Kenting National Park, Taiwan, these midges can continuously traverse seawater surfaces for over 90 min at speeds around 340 body-lengths per second. Their flight relies on two primary mechanisms: wing sculling to utilize surface tension for thrust and wing retraction to generate aerodynamic lift. This study addresses the gap in understanding how marine midges generate the lift and thrust needed for prolonged flight. We investigated their unique locomotion by conducting experiments to measure their weight, speed, and wing frequency. These measurements informed 3D computational fluid dynamics (CFD) simulations to analyze the aerodynamic forces involved. The results highlight the critical role of the ground effect, where maintaining minimal gaps of 0.08 mm between the midge trunk and 0.055 mm at the wing tips is essential for lift. Additionally, a high wing-beat frequency exceeding 300 Hz is crucial for generating sufficient lift during wing retraction. Our findings emphasize that ground effect, forward speed (>60 cm/s), and wing-beat frequency are key factors enabling marine midges to sustain flight above the sea surface. This unique adaptation for water surface locomotion not only showcases the midge's remarkable flight capabilities but also offers valuable insights for the design of micro-air vehicles (MAVs). [ABSTRACT FROM AUTHOR]

The main structure of the transmission tower consists of the tower body and the cross arm, which serve as vertical support and transverse extension, respectively. Compared with the tower body, due to the difference between the transverse and longitudinal projected areas of the cross-arm, the wind load distribution of the cross-arm is more complicated and requires more in-depth research. In this paper, wind tunnel force tests under skew wind were carried out on the 1:20 scaled rigid models of the tubular and the tubular-angle combined cross-arms. The tests consider four solidity ratios (0.2, 0.3, 0.4, and 0.5) under three wind speeds and 19 yaw angles. The aerodynamic force coefficients Ci, the skewed wind load factor Kθ, the transversal and longitudinal wind load distribution factor nX and nY, and the angle α between the transversal aerodynamic force coefficient (CX) and the resultant wind force coefficient (CR) were obtained and analyzed. It was found that the wind load coefficients decrease with increasing solidity ratio. The tested drag coefficient of the tubular cross-arm is larger than the combined cross-arm under the same solidity ratio. The nX of the tubular and combined cross-arm reaches the maximum range of 0.33–0.47 and 0.22–0.23 at 30° <θ < 45° and 30° < θ < 35°, respectively. The nY curves were ordered from large to small as follows: EN 50341-1, the tested tubular cross-arm, the tested combined cross-arm, and JEC-127-1979. At 55° < θ < 65°, the difference of α and θ for the tested tubular and combined cross-arm reaches the maximum of 10°–18° and 29°–32°, respectively, indicating that the lift force cannot be ignored and the assumption α = θ is not applicable. Reasonable nonlinear fitting functions are proposed to accurately calculate the wind load of the two types of cross-arms. [ABSTRACT FROM AUTHOR]

To explore the gas–liquid interaction processes in a spiral-vane-type multiphase pump, the influence of the operating parameters on the interaction forces between the two flow phases was studied. The results show that the gas–liquid interaction forces in the impeller domain of the spiral-vane-type pump are significantly stronger than those in the diffuser domain. Specifically, the drag is four orders of magnitude greater than the lift and the virtual-mass force, and the turbulent dispersion force is the smallest. The inlet gas volume fraction (IGVF) of the multiphase pump was found to have little effect on the drag near the hub, and the effect is greater near the shroud. Increasing the IGVF was found to increase the proportions of lift and virtual-mass force in the multiphase pump to varying degrees, while the turbulent dispersion force remained almost unaffected. The influence of the rotational speed on the gas–liquid interphase forces in the multiphase pump mainly occurs in the impeller domain, and the specific performance of each force varies greatly with the axial position. [ABSTRACT FROM AUTHOR]

The cross-flow vortex-induced vibration (VIV) response of an elastically mounted idealized undulatory seal whisker (USW) shape is investigated in a wide range of reduced velocity at angles of attack (AOAs) from 0° to 90° and a low Reynolds number of 300. The mass ratio is set to 1.0 to represent the real seal whisker. Dynamic mode decomposition is used to investigate the vortex shedding mode in various cases. In agreement with past studies, the VIV response of the USW is highly AOA-dependent because of the change in the underlying vortex dynamics. At zero AOA, the undulatory shape leads to a hairpin vortex mode that results in extremely low lift force oscillation with a lowered frequency. The frequency remains unaffected by VIV throughout the tested range of reduced velocity. As the AOA deviates from zero, alternating shedding of spanwise vortices becomes dominant. A mixed vortex shedding mode is observed at AOA = 15° in the transition. As the AOA deviated from zero, the VIV amplitude increases rapidly by two orders, reaching the maximum of about 3 times diameter at 90°. An infinite lock-in branch is present for AOA from 60° to 90°, where the VIV amplitude remains high regardless of the increase in reduced velocity. [ABSTRACT FROM AUTHOR]

In mineral processing, column flotation is being used extensively for fine particle beneficiation. Although a few attempts were made to develop computational fluid dynamics (CFD) models for column flotation in the past, validation against comprehensive experimental data is yet to be demonstrated. This work employs an Eulerian-Eulerian model coupled with the standard k-ε turbulence model for modeling the hydrodynamics in the column flotation. The two-phase simulations were performed on both laboratory and industrial-scale column flotations. The two-fluid model was further modified with the appropriate interphase forces (Ishii-Zuber drag force and Tomiyama lift force) and population balance method (PBM) to accurately simulate and predict the bubble dynamics. The axial and radial gas holdup variations along with the axial liquid velocity are predicted at different air and liquid superficial velocities. The numerical predictions were then validated against the Electrical Resistance Tomography (ERT) data in a 4-inch laboratory column flotation and conductivity probe data in an industrial column flotation. The modified two-fluid model was able to predict accurate hydrodynamics close to ERT data. The gas holdup was found to increase with the superficial air velocity, liquid height, and liquid velocity. The gas holdup found uniformly dispersed radially at low superficial air velocities and heterogenous dispersed bubble flow at higher superficial velocities. A parabolic profile of liquid flow observed at higher superficial air velocities. [ABSTRACT FROM AUTHOR]

Understanding the effect of airfoil geometry on the criticality of leading-edge suction is key to modeling the leading-edge vortex (LEV) dynamics of unsteady airfoils in a simple and robust manner. The current work aimed at investigating the dependency of the leading-edge suction parameter (LESP), a nondimensional measure of the leading-edge suction, at its critical value, which is indicative of leading-edge vortex initiation, on airfoil camber. Computational data for six NACA XX12 series airfoils with varying camber magnitude and maximum camber location at Reynolds numbers 30,000 and 3 million were analyzed. Observations indicate that increasing the airfoil camber leads to delayed LEV initiation and suction breakdown due to higher leading-edge flow curvature. The rate of increase of critical LESP with camber was seen to be independent of Reynolds number. Aftward movement of the maximum camber location was seen to have a reducing effect on the airfoil's forces and LEV dynamics. Lift and drag forces were observed to be dependent on camber magnitude and location prior to LEV formation but independent during the LEV-dominated part of the motion. The findings from the current work provide insights into reducing the dependency of the LESP on airfoil geometry. [ABSTRACT FROM AUTHOR]

This study analyzes the influence of nine distinct texture geometries on a convergent oil film gap using a simulation model. The geometrical dimensions of the textures are characterized by the texture area density, S t e x. , A and the ratio of the textured-to-untextured area ( A t e x. / A 0) . The results show that different texture geometries optimize the tribological performance depending on the value of S t e x. , A . Rectangular textures with variable widths (85% of the texture length a t e x. ) significantly enhance lifting and the drag force across a broad range of S t e x. , A . Furthermore, rectangular textures with a constant width (85% of the global width b 0 ) show the best improvement within this study. The investigation also reveals that a small texture pitch angle, α t e x , further enhances tribological performance. [ABSTRACT FROM AUTHOR]

This article discusses the issue of flow-related thrombosis in prosthetic heart valves (PHVs) and presents the "StreamlineValve Project," which aims to address this problem. Valvular heart disease affects millions of people worldwide, and while PHVs have improved survival rates, they still encounter flow-related thrombosis. The project plans to use passive flow control strategies inspired by nature to modulate the flow field and reduce factors contributing to coagulation on PHVs. The goal is to create a flow-controlled PHV that acts as a self-cleaning valve, improving durability and patient safety. [Extracted from the article]

At present, the International Maritime Organization (IMO) has issued interim guidelines for the direct stability assessment of surf-riding and broaching for the second-generation intact stability criteria. Accurately and efficiently predicting surf-riding and broaching remains a key problem to be solved for the direct stability assessment of surf-riding and broaching. Therefore, a six-degree-of-freedom(6DOF) coupled mathematical model is established in this paper. Firstly, the four-degree-of-freedom(4DOF) coupled equations of surge–sway–roll–yaw motions are built based on the traditional MMG maneuvering mathematical model by considering Froude–Krylov forces, diffraction forces and restoring forces, and the heave and pitch are approximately calculated by iteratively solving improved static equilibrium equations in real-time, effectively solving the divergence problem in direct time-domain seakeeping calculations of high-speed ships in stern-quartering waves. Secondly, the hydrodynamic lift forces due to the coexistence of wave particle velocity and ship forward velocity are taken into account in the propeller-thrust and rudder-force models. In addition, the real-time emersion of twin rudders in waves is considered in the rudder-force models. At the same time, the free-running model experiments with a ONR tumblehome vessel are carried out in stern-quartering waves, and the pure loss of stability and broaching motions are observed. Finally, comparative validations between the calculations and the experiments of surf-riding and broaching in stern-quartering waves are carried out, and the effects of the ship speed, the instantaneous wetted surface of the hull, rudder exposure, heave and pitch motions on predicting surf-riding and broaching motions are investigated. The computation results show that the established 6DOF mathematical model has enough accuracy to be used for the direct stability assessment of the surf-riding and broaching failure modes. [ABSTRACT FROM AUTHOR]

A numerical investigation was conducted in this study utilizing Force Element Analysis to explore the vortex-induced vibration (VIV) mechanism of side-by-side dual cylinders under the conditions of Reynolds number Re = 100, mass ratio m* = 10, and spacing ratios L/D ranging from 3 to 6. The hydrodynamic forces by force element formulas were incorporated into the vibration response calculations of elastically supported rigid cylinders using a User-Defined Function (UDF) and the fourth-order Runge–Kutta method. A comprehensive analysis was performed to elucidate the combined effects of the spacing ratio L/D and reduced velocity Ur on the vibration responses, quantifying the hydrodynamic forces involved in the mutual interaction during VIV for side-by-side dual cylinders. The influence mechanisms of inter-cylinder interaction and their effects on the resultant hydrodynamic phenomena were discussed. It was revealed that for side-by-side arranged dual cylinders outside the "lock-in region", the lift and drag forces are predominantly supplied by the volume vorticity forces in conjunction with surface vortices (including frictional) forces. However, within the "lock-in region", the surface acceleration lift forces provide greater force contributions, and the volume vorticity lift force contributes significantly to negative values. Notably, alterations to the spacing ratio do not change the proportion of force element components. The amplitudes of the cylinders' mutual interaction forces are identical in magnitude but opposite in phase. Additionally, the "slapping" phenomenon near the "lock-in region" leads to "bounded" trajectories of cylinders. [ABSTRACT FROM AUTHOR]

Anaerobic membrane bioreactors (AnMBRs) have emerged as an effective technology for treating domestic and industrial wastewater. However, AnMBRs typically exhibit low membrane fluxes (<10 L/m2.h), which limits their wide application. Despite the use of various techniques to control membrane fouling, the relationships among these techniques and the challenges associated with their application remain unclear. Current literature categorizes membrane fouling control approaches into four classes, namely a reduction in the concentration of soluble microbial products (SMP), an increase in shear, an increase in particle size, and membrane optimization. Biological techniques are effective in reducing the concentration of SMP but limit the flexibility of reactor operation. The remaining three methods are non-biological techniques. Shear-induced lift force, permeation drag force, and the xDLVO theory on microparticles can be used to elucidate the mechanisms of these non-biological techniques, except for dynamic membranes. This indicates that other proposed additional forces may be disregarded. Non-biological techniques are associated with high energy costs and membrane damage. Hydrophilic membranes are effective but super-hydrophilic membranes have not been used in AnMBRs. Different materials rather than the membrane should be applied to create an electronic field for membrane fouling control. The application of dynamic membrane should not result in biofouling of a downstream water treatment process. Among current techniques, dosing flocculant is the most promising method for controlling membrane fouling, but developing an auto-flocculant dosing strategy is vital. Overall, this article provides an overview of current membrane fouling strategies and reveals their inherent relationships and challenges for their applications. [ABSTRACT FROM AUTHOR]

To improve the aerodynamic efficiency of the aircraft, the article focuses on optimizing the L/D ratio through postponement of flow separation. Elevating the L/D ratio leads to diminished drag and delays stall occurrence at high angles of attack (α). The wing geometry adopts NACA 6-digit airfoils, specifically NACA 63418 and NACA 63415. Various aerodynamic devices are explored for their ability to defer flow separation, with passive aerodynamic devices being the prevalent choice. The primary goal of the research is to integrate rotational thin wire elements into the aerodynamic components of the wing, aiming to diminish drag, amplify lift, and enhance overall aerodynamic performance. The analysis spans a range of α, from 0° to 20°. The study encompasses two scenarios: one without the incorporation of aerodynamic devices and the other with their implementation. Comparative analyses of increases in CL and reductions in CD, with notable improvements observed at a 15o angle of attack, 28.47% increase in CL and 15.07% decrease in CD. Furthermore, the improved performance in the CL/CD, which increases substantially in stall conditions, thereby demonstrating the potential of these aerodynamic modifications to enhance overall aircraft performance. [ABSTRACT FROM AUTHOR]

Dynamic stall is a serious phenomenon that restricts aeronautical vehicles' maneuverability. It happens on the blades as their angle of attack increase, especially on the blade of wind turbines. In this paper, two airfoils are investigated in actual conditions. To alleviate dynamic stall the geometries of the airfoils are modified by drooping and rounded leading-edge tip method and also combination of both. To study the effect of the modifications, the unsteady flow fields around the pitching airfoils, numerically simulated using URANS. Results illustrates, in addition to alleviate dynamic stall, the methods enhance aerodynamic characteristics by reducing drag force and preventing sudden jump of lift force, especially at the maximum angle of attack. Finally, a detailed investigation is conducted on the flow behavior around the airfoil to discover the supporting physics behind the improvements made by the present methods. Which revealed that these two passive methods, aim to prevent the formation of leading-edge vortex on the airfoil which finally delays the dynamic stall. [ABSTRACT FROM AUTHOR]

This study aimed to analyze the aerodynamic characteristics of Chinese Nordic combined athletes during the ski jump take-off process, comparing them with elite athletes from the 2009 Nordic World Ski Championships using computational fluid dynamics (CFD) methods. Methods: Using 3D model analysis and continuous relative phase analysis, CFD methods were utilized to assess the mechanical characteristics of athletes during the take-off phase. Results: The analysis revealed that Chinese athletes displayed a lower dominance of the knee joint during the take-off phase, leading to increased air drag. Conclusion: Reduced knee joint dominance and an excessive ankle angle at the initiation of the ski jump take-off contribute to higher air drag. The lean angle of the body and the ankle angle post-take-off significantly affect the resultant lift and drag forces. [ABSTRACT FROM AUTHOR]

Small finite-size particles suspended in fluid flow through an enclosed curved duct can focus to points or periodic orbits in the two-dimensional duct cross-section. This particle focusing is due to a balance between inertial lift forces arising from axial flow and drag forces arising from cross-sectional vortices. The inertial particle focusing phenomenon has been exploited in various industrial and medical applications to passively separate particles by size using purely hydrodynamic effects. A fixed size particle in a circular duct with a uniform rectangular cross-section can have a variety of particle attractors, such as stable nodes/spirals or limit cycles, depending on the radius of curvature of the duct. Bifurcations occur at different radii of curvature, such as pitchfork, saddle-node and saddle-node infinite period (SNIPER), which result in variations in the location, number and nature of these particle attractors. By using a quasi-steady approximation, we extend the theoretical model of Harding et al. (J. Fluid Mech. , vol. 875, 2019, pp. 1–43) developed for the particle dynamics in circular ducts to spiral duct geometries with slowly varying curvature, and numerically explore the particle dynamics within. Bifurcations of particle attractors with respect to radius of curvature can be traversed within spiral ducts and give rise to a rich nonlinear particle dynamics and various types of tipping phenomena, such as bifurcation-induced tipping (B-tipping), rate-induced tipping (R-tipping) and a combination of both, which we explore in detail. We discuss implications of these unsteady dynamical behaviours for particle separation and propose novel mechanisms to separate particles by size in a non-equilibrium manner. [ABSTRACT FROM AUTHOR]

To achieve a better aerodynamic performance of wind turbines, the selection of a proper airfoil plays a crucial role. Generally, aviation airfoils (such as the NACA series) were widely used in the design of wind turbine blades due to their aerodynamic characteristics. However, several studies have shown that there are a number of defects in the application of aviation airfoils for blade design, such as poor stall characteristics or incompatible performance at different Reynolds numbers. The aerodynamic performance and lift force of newly developed airfoils inspired by cetaceans, birds, and insects were numerically investigated by CFD in the range of Reynolds number of 1.2 × 105 to 1.7 × 105 and a range of angles of attack (from 0° to 25°). ANSYS Fluent and the Shear Stress Transport (SST) k-ω turbulence models were selected to analyse the pressure and velocity distributions around the airfoils. In addition, the aerodynamic efficiency was calculated for all different cases. For verification and comparison, DU 06-W-200 airfoil was also simulated under the same operating conditions. Results revealed that several of these new bio-inspired designs can increase the aerodynamic performance of the DU 06-W-200 airfoil by up to 24.7%, with the bird-inspired airfoils presenting the best performance among all designs, and the best options for the design of vertical axis wind turbine (VAWT) blades. [ABSTRACT FROM AUTHOR]

This study presents a computational analysis of fluid flow characteristics around two staggered arranged square cylinders using the Lattice Boltzmann Method (LBM). With Reynolds number (Re) fixed at 200, numerical simulations explore the influence of varying gap ratios (G) ranging from 0 to 10 times the cylinder size. Emphasis is placed on understanding the impact of cylinders spacing on flow structure mechanisms and induced forces. Investigation of fluid flow parameters includes vorticity behavior, pressure streamlines, and variations in drag and lift coefficients alongside the Strouhal number under different values of G. From the results, four distinct flow patterns emerge: single bluff body flow, flip flopping flow, modulated synchronized flow, and synchronized flow, each exhibiting unique characteristics. This study reveals the strong dependence of fluid forces on G, with low spacing values leading to complex vortex structures and fluctuating forces influenced by jet flow effects. At higher spacing values, proximity effects between cylinders diminish, resulting in a smoother periodic flow. The Strouhal number, average drag force and the rms values of drag and lift force coefficients vary abruptly at narrow gaps and become smooth at higher gap ratios. Unlike the tandem and side-by-side arrangements the staggered cylinders arrangement is found to have significant impact on the pressure variations around both cylinders. Overall, this research could contribute to a comprehensive understanding of staggered cylinder arrangements and their implications for engineering applications. [ABSTRACT FROM AUTHOR]

This paper investigates the two-phase flow hydrodynamics of a column flotation operated from a homogeneous to a heterogeneous flow regimes using experimental and computational fluid dynamics (CFD) techniques. Experiments were conducted in a lab scale column flotation of 0.1 m internal diameter and 2.5 m length at various superficial gas velocities using a dual plane electrical resistance tomography (ERT). The mean gas holdup increased from 2 to 18% with the increase in superficial gas velocity from 0.6 to 7.2 cm/s. The gas holdup-based bubble swarm velocity method identified four distinct flow regimes, i.e. homogeneous bubbling regime, narrow discrete bubbling regime, a sustained helical flow regime and churn turbulent flow regime in the column. Further, transient simulations were conducted using a two-fluid model coupled with a population balance model to assess the flow behavior inside the column. Virtual mass, lift and drag forces were incorporated into the model to account for the interphase forces. Numerical simulations predicted mean gas holdup was matching with the experimental data at low gas velocities (<2.4 cm/s), and a marginal deviation was noted at higher gas velocities (>2.4 cm/s). The predicted radial gas holdup profiles were found to change from flatter to parabolic with the increase in gas velocities, i.e. similar to the experiments. The effect of particle size on the rate constant and recovery was estimated with Luttrell and Yoon’s performance model using the particle floatability input data and the two-phase experimental data. The developed CFD model can be useful to optimize the operating and design parameters for efficient operation of the column flotation process. [ABSTRACT FROM AUTHOR]

This investigation studied numerically the aerodynamical effects of different modifications in a model of a common sedan. Four car modifications as spoiler, wing profile spoiler, standard diffuser and curved diffuser and their combinations were reported. Using a three-dimensional sedan model created with Computer-Aided Design software, the modifications are applied and assessed their influence on aerodynamics at speeds ranging from 60 to 120 km/h. The spoiler, wing spoiler, standard diffuser and curved diffuser reducing the lift forces experienced by the vehicle. Three cases, spoiler, wing spoiler, and curved diffuser increase the drag forces Combining a curved diffuser and a spoiler significantly decreases lift forces by an average of 77.8%, albeit with a 15.3% increase in drag forces, by 120 km/h The synergy of a curved diffuser and a wing spoiler achieves a substantial 63.3% reduction of net vertical forces, with only a 7.9% increase in drag forces, by 120 km/h, offering improved control with lesser energy consumption in comparison to other combinations. Results show that modifications, greatly influence airflow interaction, with effects varying by speed. Importantly, the impact of using two modifications is not a simple sum of their individual effects; and it must be assessed thoughtfully alongside airflow alterations. [ABSTRACT FROM AUTHOR]

Electromagnetic levitation (EML) is a promising technique allowing to melt various materials, including refractive metals, while avoiding physical contact between the molten material and components of the melting system, thus avoiding contamination of the molten material. EML coils act both as a container and a heating source for a conductive sample placed within it. EML systems are difficult to optimize for specific tasks and computational simulations are often used to aid the process. Development of simulations of EML processes is an ongoing field of research. Obtaining precise experimental measurement data of EML processes is important for development and verification of computational simulations. This study aims to provide experimental data of simultaneous measurements for magnetic field, Joule heating and lift force in different conical EML coils with a counterturn. [ABSTRACT FROM AUTHOR]

Coach car is a commonly used mode of transportation, due to its large passenger capacity, in case of accidents, it will cause enormous human casualties and economic losses. To improve the braking performance of coach car, an aerodynamic plate is installed on the top of coach car to assist braking. Based on RANS (Reynolds average Navier-Stokes) equations and SST (Shear-Stress Transport) k-ω turbulence model, the aerodynamic performance of coach car with different aerodynamic parameters is analyzed by computational fluid dynamics method. The numerical algorithm and setting are verified by wind tunnel tests. In this paper, the influence of four parameters, including car speed, plate configuration of maximum opening angle, installation position, and plate height, on the aerodynamic drag and lift coefficient of coach car is discussed by using control variable method and orthogonal test method. The conclusions of the two methods are consistent, that is, the optimal combination of plate configuration is that installation position, maximum opening angle, and height are 10 m, 80°, and 1 m, respectively. According to the results of range and variance analysis, the order of influence of aerodynamic parameters on the aerodynamic drag and lift coefficient is installation position, maximum opening angle, height, and car speed. [ABSTRACT FROM AUTHOR]

To explore the effect of the gas-solid coupling of a counterweight-car instantaneous intersection (CCII) on horizontal vibration in the real service environment of a super high-speed elevator, a three-dimensional gas-solid coupling numerical model for the CCII of super high-speed elevator was constructed. By using the dynamic layering grid technology, the transient law of "shear" aerodynamic load of the CCII of super high-speed elevator was analyzed by numerical simulation. And the effect of "shear" transient aerodynamic load on the horizontal vibration response of the car under the different opposite intersection speeds (v = 7 m/s, 10 m/s, 13 m/s, 16 m/s, 19 m/s, 22 m/s) was studied. Taking the 7 m/s speed condition as the real elevator object, the effectiveness of the three-dimensional calculation model of instantaneous intersection gas-solid coupling horizontal vibration was verified by experiments. The results showed that a huge transient "shear" lateral aerodynamic lift was generated in the process of the CCII, and the transient lateral aerodynamic lift difference was positively correlated with the running speed by cubic polynomial. In addition, with the significant increase of running speed, the typical digital characteristics of the car's horizontal vibration acceleration and the relative increase of the vibration dose (VDV) for the gas-solid coupling of the CCII were 38.242%-234.129% and 23.567%-227.193%, respectively and the low-frequency maximum vibration amplitude increases significantly. This paper provides an effective analysis method for the gas-solid coupling horizontal vibration of super high-speed elevator counterweight-car instantaneous intersection, and provides a theoretical basis for the design of an accurate active vibration reduction control strategy for a super high-speed elevator. [ABSTRACT FROM AUTHOR]