Search

A pressure correction method is proposed considering the influence of a dual factor. The applicability of a pressure correction method coupled with a drag model is discussed along with the accuracy of the simulation results obtained by such a pressure correction method. It is found that the present pressure correction method combined with the DBS (dual bubble size) drag model can accurately reflect the changing trend of gas holdup distribution with pressure. It is also established that results from this model applied to a bubble column match well with the experimental data. Finally, when compared with other pressure correction models, the proposed model shows better robustness in three‐dimensional simulations and can predict radial gas holdup distributions with better accuracy. [ABSTRACT FROM AUTHOR]

Seaweeds are widely assumed to be phenotypically plastic across hydrodynamic gradients, yet while many marine macroalgae exhibit intraspecific phenotypic variation that correlates with flow, researchers often fail to test whether such variation is due to plasticity or another mechanism, such as local adaptation. In this minireview, we considered mechanisms for sensing flow in seaweeds that could facilitate adaptive phenotypic plasticity across hydrodynamic gradients. We then reviewed the literature from 1900 to 2024 to see how often phenotypic variation and plasticity across hydrodynamic gradients had been observed and demonstrated in different groups of seaweeds. In the last 124 years, phenotypic variation and plasticity in response to flow have been well documented in brown algae but scarcely documented in red and green algae. This could suggest that brown algae are better able to sense and respond to flow than red and green algae, perhaps due to the intercalary meristem of many brown algae, including most kelps. However, this skewed distribution could also be the result of publication bias, as most studies involving flow have been conducted on brown algae. Only 30% of 141 papers specifically investigated if observations of phenotypic variation along hydrodynamic gradients were due to plasticity. To date, phenotypic plasticity in response to flow has been demonstrated in 20 brown algal species, five red algal species, and two green algal species. Thus, the assumption that phenotypic plasticity to flow is common across seaweeds is not particularly well supported by the literature. Mechanisms underlying plasticity to flow are poorly understood and remain a critical avenue for future research. [ABSTRACT FROM AUTHOR]

Ocean currents are a crucial means of dispersing natural and human-made materials on the ocean surface. Macroalgae are among the most conspicuous natural dispersers, often called the 'tumbleweeds of the ocean.' Despite numerous studies on the subject, the relative influence of wind and surface currents on the trajectory of macroalgal dispersal remains uncertain. Previous studies have focused on kelp rafts of varying sizes, making it challenging to determine the impact of wind versus currents. These studies have also disregarded the macroalgae's drag characteristics and surface area, which have been shown to impact the trajectory and accumulation of floating flotsam. This numerical study aims to shed light on the relative influence of wind and currents and the role of drag in determining the course and accumulation of macroalgae. By comparing simulations of virtual kelp 'particles' that incorporate drag and those without, this study focused on solitary kelp plants and considered the impact of morphological characteristics, flow-field combinations, and the presence of Stokes drift. Our results show that virtual kelp particles generally followed ocean currents, but the inclusion of drag caused deviations from purely Lagrangian particles' trajectories and sheds light on the complex interplay of factors affecting macroalgal dispersal in the ocean. [ABSTRACT FROM AUTHOR]

This article offers an autoethnographic account of the creation of my drag persona, Mary Magdelish. I argue that Magdelish is a rhetorically embodied text created by the intertwining queer and religious strains of my life in response to a traumatic moment in the Catholic Church. This article explores how embodiment, performance, and haunting come together through the art of drag to revise and reclaim the experience of coming out to my parish pastor. Framing haunting as a strategy of refusal, this article positions Magdelish as a rhetorical response to haunting that becomes its own haunting. As ghosts unbury violences of the past, Magdelish makes present the history of religious violence against queer communities. Simultaneously, she demonstrates a synergy between religious and queer performances that forces viewers to confront their own conceptions of religiosity and queerness. Ultimately, I argue that Magdelish's performance creates a counternarrative in the Church that disrupts majoritarian stories surrounding queerness and Catholicism. [ABSTRACT FROM AUTHOR]

Founder of the collectives Casa Drag Latina and House of Gad, Gad Yola is an Afro-Peruvian multidisciplinary artivist based in the city of Madrid. As part of a trans-Atlantic Latinx queer media history, Gad Yola's career allows us to inquire about what can be described as transvestite, antiracist, and transfeminist drag "positioning" against injustices happening on both sides of the Atlantic. Be this their rejection of state violence in Peru, their support for the massive regularization of migrants in Spain, their critique of the racist gaze, or their celebration of brown bodies, Gad Yola's interventions significantly contribute to the cultural articulation of antiracism in Spain. The following interview will consider the digital and feminist interrelation by focusing on Gad Yola's identification with antiracism, transfeminism, and their references, as well as on the use of social networks as identity and community resources. [ABSTRACT FROM AUTHOR]

With the increasing popularity of vertical axis turbines (VATs), researchers are now focusing on their performance improvement. Instead of adopting conventional means of performance improvements such as augmentation techniques and exhaustive parametric design optimization, the bio-inspired turbine designs have become a center of attraction, especially during the last decade. This review article attempts to compile the bio-inspired designs belonging to the VATs. Bio-inspired designs implemented in Savonius, Darrieus, Nautilus, and Seed-inspired turbines are elaborated besides giving a detailed explanation of the corresponding bio-organism and natural phenomenon. How the working principles of bio-organisms emulated in the form of fluid dynamic design are explained thoroughly in this paper. The bio-inspired designs for VATs are then classified pragmatically for the future designs. Research gaps are highlighted for the aspiring researchers, and this is followed by the important strategies and allied challenges. [ABSTRACT FROM AUTHOR]

Riparian forests contribute to the resilience and biocomplexity of floodplains but may be catastrophically impacted by large floods. Forest disturbances will expose floodplains to stripping and pulses of large wood recruitment to the floodplain and channel. The widespread uprooting of trees follows hydrodynamic loading from floodwaters and the associated moments of these forces about the tree bases. A tree will uproot when the drag moment exceeds the anchorage resistance capacity. Alternatively, trunks will rupture when the tensile stresses caused by bending exceed the tensile strength of the outer trunk fibres. The likelihood and pattern of trees dislodging during floods on a subtropical river was investigated by developing a tree stability model. The modeling framework included development of a drag moment model and testing several potential formulations for anchorage resistance. Model parameters were calibrated to data collected in experiments and from observations in aerial photographs before and after a large flood in 2011. The prediction accuracy for the adopted tree stability model was 78%. Results from design flood simulations suggest that less than a third of the forest will dislodge even during the largest floods conceivable. This remarkable stability moderates the quantity of large wood recruited from riparian forests during extreme floods, which can impact infrastructure such as bridges and culverts downstream. Low rates of wood recruitment from dislodged floodplain trees in extreme floods suggests bank erosion is the dominant source of wood recruitment in these catchments. [ABSTRACT FROM AUTHOR]

This study investigated the relationships between load-velocity profiling and 50 m breaststroke performance. Twenty-seven male swimmers qualified for the national championship participated and performed a 50 m breaststroke trial with a multicamera system. The total race time (t50 m), forward velocity during surface swimming (v50 m), stroke length, and stroke frequency were obtained from the automatic post-processing of the system. Afterwards, the participants performed semi-tethered swimming with three external loads using a robotic resistance device. The average velocity from three stroke cycles was plotted as a function of the corresponding load. The theoretical maximum velocity (v0) and load (L0), L0 normalized to body mass, steepness of the regression line (slope), and active drag (AD) were calculated. The main findings were moderate to large correlations of two 50 m race variables (t50 m and v50 m) with v0, L0, and AD (t50 m range: r = -.444 to r = -.619, p =.020 to p =.001), (v50 m range: r =.451 to r =.568, p =.018 to p =.002). This shows the importance of applying maximum propulsive force to achieve high swimming performance and that load-velocity profiling is an indicator of 50 m breaststroke performance. Load-velocity measurements over time can also monitor velocity, strength, and drag-minimizing abilities, explaining performance changes and training effects. [ABSTRACT FROM AUTHOR]

Background: Drafting is a common technique to reduce the drag experienced by elite runners on races, leading to faster finish times. The tactic has been successfully used in previous marathon world records. In the 2023 Chicago Marathon, Kenyan runner Kelvin Kiptum broke the marathon record after a 2:00:35 finish. This feat is impressive considering the lack of use of drafting, despite the availability of two pacers for the majority of the race. Methods: In this study, the drag faced by Kiptum and his pacers during the race is calculated by means of computational fluid dynamics (CFD). The performance of each runner is evaluated from an energetic standpoint, and the analysis is extended to include more efficient drafting formations. Results: Running in proper formations results in drag reductions in excess of 70% for the main runner. Our results indicate that, by properly using the advantages of drafting, Kiptum could have finished the race at a staggering 1:57:34, a full three minutes better than his own record and 215 s better than the previous world record. Conclusion: Proper use of drafting does indeed improve the energetic performance of a runner, allowing for lower race times and potentially helping elite runners in breaking the 2-h barrier for a marathon. [ABSTRACT FROM AUTHOR]

Drawing on the seminal work of feminist and queer theorist Judith Butler, this article compares the practice of gender impersonation in the South Indian dance form of Kuchipudi with American drag performance. While impersonation in Kuchipudi and American drag performance arise from radically distinct gendered, cultural, and religious contexts, the juxtaposition of these two seemingly disparate spheres generates a useful framework for comparison that illuminates new ways of interpreting gender and caste in contemporary South India. Focusing on the Kuchipudi dancer Vedantam Satyanarayana Sarma and the drag ball performer Venus Xtravaganza, this article analyzes the gender and caste norms of Kuchipudi dance in Telugu-speaking South India while outlining the limitations of Butler's theory of gender performativity. [ABSTRACT FROM AUTHOR]

This study addresses interceptor devices to improve the hydrodynamic characteristic of autonomous unmanned surface vehicle (USV). The bulb and rectangular interceptors had molded on a planning hull. This research aims to mitigate drag impact on rectangular interceptors at high speeds. According to this study, a bulb interceptor had a better impact than a rectangular interceptor. This research is based on the finite volume method (FVM) with dynamic fluid-body interaction (DFBI), which captured the ship's dynamic trim and sinkage. The simulation used an overset mesh technique with two domains as a donor-acceptor cell. Furthermore, numerical calculations using the Reynolds-Averaged Navier-Stokes equation and the k-turbulence model predict the turbulent flow. Grid independence studies and international towing tank conference (ITTC) recommendations have been applied to ensure simulation accuracy. This study reported that the bulb interceptor had effectiveness between 9%-25% compared to the rectangular interceptor at high speed. This research showed that the bulb interceptor had better effectiveness than the rectangular interceptor. [ABSTRACT FROM AUTHOR]

In automotive aerodynamics, it is not common to focus on a specific vehicle due to restricted access to the Computer Aided Design (CAD) geometries, their short life span, and limited validation data. For this reason, researchers prefer generic bodies that look like automobiles such as Ahmed body in their investigations. However, the absence of moving ground and rotating wheels makes these generic bodies unrealistic for aerodynamic studies. In this context, including wheels in Computational Fluid Dynamic (CFD) simulations, varying ground, and wheel boundary conditions, and comparing their qualitative and quantitative ow parameters with the original Ahmed body experiment is the main objective of this paper. Results have shown that changing stationary ground and wheel boundaries into moving and rotating boundaries do have minor effects on wake characteristics and drag coefficients. However, just the presence of wheels on the model increases force coefficients significantly (increment in drag and lift coefficients by 27.32% and 188.5 counts, respectively.) even though these boundaries are stationary. As a result, the absence of moving ground and rotating wheels can be tolerated to some extent (especially for experimental studies in which inclusion of moving and rotating boundaries may have difficulties). However, a study cannot be evaluated exactly with a model without wheels. [ABSTRACT FROM AUTHOR]

Extended-reach drilling represents an advanced way of drilling and accessing reservoirs that were previously economically not feasible to drain, impossible to reach or in an environmentally sensitive area. One of the main issues that appears while drilling such wells is caused by the high values of friction factor which cause high values of torque and drag. One of the suggested solutions is to use a protective sliding ring made from materials such as POM, Teflon and PA6 in combination with lubricants added to a polymer mud system. First, measurements were conducted on a lubricity tester to choose the best material and, after finishing, a mechanical wear test was conducted on a specially designed device to measure mechanical wear. Results showed that Teflon showed lower values of friction factor in comparison to steel and the mechanical wear was minimal. The lowest value of friction force was recorded for blocks made from Teflon in tested mud systems. It is also noticeable that, in polymer mud with weighting additives and lubricant, the value of the friction force is higher than in polymer mud with lubricant only. [ABSTRACT FROM AUTHOR]

This study explores the impact of feathers on the hydrodynamic drag experienced by diving birds, which is critical to their foraging efficiency and survival. Employing a novel experimental approach, we analyzed the kinematics of both feathered and nonfeathered projectiles during their transition from air to water using high‐speed imaging and an onboard accelerometer. The drag coefficients were determined through two methods: a direct calculation from the acceleration data and a theoretical approach fitted to the observed velocity profiles. Our results indicate that feathers significantly increase the drag force during water entry, with feathered projectiles exhibiting approximately double the drag coefficient of their smooth counterparts. These findings provide new insights into the role of avian feather morphology in diving mechanics and have potential implications for the design of bioinspired aquatic vehicles in engineering. The study also discusses the biological implications of increased drag due to feathers and suggests that factors such as body shape might play a more critical role in the diving capabilities of birds than previously understood. [ABSTRACT FROM AUTHOR]

Interatomic forces significantly influence the flow behavior and dispersion stability of the suspensions in new thermal applications. Using a molecular dynamics technique, the current work focuses on the interatomic forces are estimated. The present analysis accounts for significant contributing factors such as drag force, Brownian force, thermophoresis force, and DLVO potential force of attraction or repulsion by using several nanoparticle dispersions, including SiO2, CNT, and GO in distilled water as the base fluid. Among all the particles considered for the study, Carbon Nanotube (CNT) showed the highest time of stability in the base fluid. That means CNT will take more time to settle down than GO (graphene oxide) and SiO2 due to its lowest density. The drag forces are high for GO (graphene oxide) mixed fluid due to its inherent properties. Another important finding is, below 0.05% volume fraction, the drag forces are insignificant for all the considered samples of analysis. The Brownian force is analyzed for various time intervals, which reports that for the initial periods of collision (Δt = 0.01) the molecular agitation is greater. However, increasing the Δt suppresses these forces. From the results, it is clear that the magnitude of Brownian force is dominant with CNT nanofluid, whereas it is the least intensity for SiO2 nano fluid. The magnitude of thermophoresis forces is less than that of drag forces, and it is observed to reach its maximum intensity at T/x = 100, indicating that temperature gradient has a dominant influence on nanoparticle movements. DLVO force of nano particle mixed water is also estimated with respect to volume fraction. Increasing the volume fraction increases the intensity of these forces. These forces are maximum for GO nano fluid. [ABSTRACT FROM AUTHOR]

In the modern aviation environment, research on unmanned aerial vehicles is attractive in many aspects. Integrating efficient propellers into the unmanned aerial vehicle structure helps to enhance the performance factors such as endurance, range, distance to take-off and payload carrying capacity. This paper numerically investigates the configured propeller blades to enhance aerodynamic efficiency and performance parameters. The design parameters such as diameter, pitch, number of blades, and blade shape were configured with highly efficient propellers. The E62 airfoil opted to configure bi-blade, tri-blade, and modified nozzle-shaped ducted propellers and subjected to a computational fluid dynamic process for the varying rotational velocity. The thrust component, lift, drag and aerodynamic efficiency of the propeller blades were studied for the different operating speeds. The performance of E62 airfoil-based propeller was more efficient whereas the ducted blade profile generates the maximum thrust of 7.07N at the maximum angular velocity. [ABSTRACT FROM AUTHOR]

Copyright of Revista Ciencia y Poder Aéreo is the property of Escuela de Postgrados de la Fuerza Aerea Colombiana and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The performance of an uncrewed aerial system (UAS) operating nominally in an indoor/outdoor environment depends upon the available power, and how well the system reacts to disturbances and nonlinear dynamic effects. This paper focuses on development of approaches to compensate for nonlinear dynamic effects due to aerodynamics, gyroscopic coupling, and rotor induced rolling effects in deriving aggressive multi-copter trajectories. A thrust constrained multi-copter is adopted for verifying the compensation, that is achieved through an optimal trajectory synthesis formulation. It is shown that the compensation approach yields precise and aggressive trajectory tracking for the multi-copter flight in and out of indoor environments, such as windows and other constrained openings. [ABSTRACT FROM AUTHOR]

Floats are the primary buoyancy component of plastic fish cages in offshore aquaculture. They can increase fish cage stress and deformation under the action of sea currents, and the rise of the float's surface liquid level can cause waves on the fish cage walkway. Although plastic fish cages are a recent development in aquaculture, little research has been conducted on the arrangement of floats. Therefore, studying the resistance performance of floats is significant for safe offshore aquaculture production. This article first studies the resistance of single and double floats through on-site measurement methods. Then, based on viscous flow theory, numerical simulations are carried out to simulate the resistance and waveforms of single and double floats under different flow velocities. The simulation results are compared with the on-site measurement results to verify the accuracy of the numerical simulation. Using the same numerical simulation method as above, numerical simulations are carried out for square and diamond two typical float arrangement forms, to analyze liquid level and resistance under different flow velocities. The results show that the numerical model agrees with the on-site measurement results, with an error of 9. 5%. Three aspects are used to analyze the advantages and disadvantages of square and diamond arrangements. (1) Liquid level rise: When the flow velocity is the same, the total liquid level rise of the diamond-shaped floats arrangement is less than that of the square arrangement. (2) Flow field distribution in the middle of two floats: The flow field between the two floats of square arrangement is more chaotic than that of diamond arrangement. (3) Average resistance: When the flow velocity is greater than 1. 5 m/ s, the resistance of diamond arrangement is 29% less than that of square arrangement. The results of the on-site measurement of the small boat towing test are compared with the results of the numerical simulation output. The resistance and waveforms agree with the test results, proving that the numerical simulation method used in this article is accurate and reliable and can provide technical support for subsequent numerical studies of floats. Analyzing the liquid level situation and liquid level cloud images of the two arrangements shows that the diamond arrangement has more stable liquid level changes and better air gap performance than the square arrangement, so it is more suitable for complex offshore environments. The diamond arrangement can provide a better working environment for offshore aquaculture. By sorting out and analyzing the results of numerical simulation, it is found that the average resistance of square arrangement and diamond arrangement is less than that of individual floats. Further comparing average resistance shows that diamond arrangement has less average resistance than square arrangement, so it is more suitable for complex offshore conditions. Floats are the primary buoyancy components of plastic fishing rafts used in offshore aquaculture. Under the influence of sea currents, the resistance generated by floats can result in increased force and deformation of the fishing raft. Additionally, the elevation of the liquid level on the float's surface can induce waves on the raft platform. Therefore, studying the resistance performance of floats is crucial for ensuring the safety of offshore aquaculture production. The resistance performance of both single and double floats was investigated through practical measurements at sea. Numerical simulations based on viscous flow theory were employed to analyze the resistance and waveform of single and double floats at various flow rates. The accuracy of the numerical simulations was validated by comparing the results with actual sea measurements. Furthermore, numerical simulations were conducted to assess the placement of two typical floats in square and diamond configurations. Liquid surface heights and resistance at different flow rates were analyzed. The findings indicate that numerical simulations align well with actual sea measurements, with an error rate of less than 9. 5%. The diamond-shaped float configuration corresponds to an elevation in the liquid surface, creating a more stable flow field between the two floats. This results in a smaller average resistance, with values below 29% in flow velocities exceeding 1. 5 m/ s. Consequently, it is recommended that this placement configuration be adopted for production operations. [ABSTRACT FROM AUTHOR]

In light of recent protests at Drag Queen Story Hour events, this essay offers a critical examination of the role of gender performance in secondary schools and English lessons through a personal exploration of how I perform gender as a queer English teacher. I show that schools perpetuate a model of gender that is binary and heterosexist; that teachers and students perform gender in complex ways; that reading in English requires queer performances of gender; and that the professional is always personal when it comes to teacher development. [ABSTRACT FROM AUTHOR]

This article investigates the artist Sin Wai Kin's (單慧乾) speculative approach to drag through the prism of 'transgendering-assemblages'. Influenced by the assemblage theory of Manuel DeLanda and Jasbir Puar, I propose that transgendering-assemblages actualize the properties of transness (Marquis Bey) through particular trans techniques (Grace E. Lavery). I introduce Sin's more-than-human trans techniques, from make-up to costume, and approach to nonbinary storytelling to investigate identity assemblages more broadly. With explicit attention to their engagement with Chinese opera and Taoism, the speculative boyband in Sin's Turner Prize nominated work It's Always You (2021) prompts my proposal for 'boybanding' as a technique for investigating identity assemblages. The final section is focused on the genderings of East Asian masculinities in Sin's work to argue how all gender-assemblages are also 'racializing assemblages' (Alexander G. Weheliye). I conclude with a provocation on what assemblage as a nonbinary concept (defined by what it does rather than what it is) can offer studies of gender. [ABSTRACT FROM AUTHOR]

Laminar flow over a modified backward-facing step (BFS) was studied experimentally and computationally, with the results compared to a flight test on a Piper Cherokee wing. The BFS was modified with a serrated spanwise variation while maintaining a constant step height, and this modification is termed a serrated BFS (sBFS). A scaling law was proposed and then used to develop the experimental operation conditions. The experiments showed evidence that the transition to turbulence was delayed over the forward part of the serration (termed the valley). The boundary layer growth and characterization were used to validate the computational model, which was then used to examine details not available from the experiment, including the wall shear stress distribution and streamlines as they go over the sBFS. The wall shear stress showed the formation of low-shear diamonds downstream of the sBFS valley that were associated with laminar flow, which confirmed previous assumptions about the low-shear diamonds observed in the flight tests. The length of the low-shear diamonds was scaled with the sBFS geometry. Finally, the streamlines showed that the near-wall flow forward of the sBFS is pumped towards the sBFS peak, where it rapidly transitions to turbulence at that location. [ABSTRACT FROM AUTHOR]

AbstractToday, the United States faces a relentless offensive of lies and falsehoods, as we grapple with the fallout from election denialism and conservative forces work tirelessly to advance anti-LGBTQ laws that directly challenge the validity of LGBTQ identities. Although it may be appealing to dismiss these shocking lies and falsehoods as legal fictions, they are nothing of the sort. They are not legal fictions in the traditional sense because they are not offered as patently false statements. More importantly, such characterization disregards the uniquely constitutive power of the law. This article builds on my earlier observations regarding a similar misuse of the term “legal fiction” in the context of chattel slavery and the doctrine of discovery. By revisiting the controversy in a contemporary frame, it offers an opportunity to study, in real-time, the attempted construction of legal regimes that rest on errors, lies, and the relentless demonization of the Other. It concludes that just as there was nothing fictive about repressive legal systems that spanned centuries and brutalized millions, there is nothing fictive about our current democratic crisis. To the contrary, it is imperative that we remain clear-eyed about the nature and power of the falsehoods that undergird both the Big Lie and the new anti-LGBTQ laws in order to develop effective strategies to refute them. We dismiss them as legal fictions at our peril. [ABSTRACT FROM AUTHOR]

Accurate range prediction requires good knowledge of the prevailing wind conditions and how they affect the energy consumption of the ego vehicle. A few different simplified vehicle air drag models that explicitly include the effect from crosswinds are presented and compared through some objective criteria. The models are developed from the normal air drag equation where the effect from wind is implicit and therefore often forgotten or neglected. The purpose is to find a low-complexity model complementing CFD models and wind tunnel tests, that can be used for range estimation and predictive energy management algorithms. To simplify online estimation, a requirement is that the air drag models only contain a few tuning parameters. The models are validated against CFD calculations for a few vehicle combinations and the best models show good accuracy for air attack angles up to at least 60 degrees. It is shown that the parameters of the simplified models can loosely be connected to some basic geometrical attributes of a vehicle combination so it should be possible to give at least a rough estimate of the parameters of a simplified model based on these geometrical attributes. This is useful for making a first estimate of the aerodynamic properties of a vehicle combination after major changes in the exterior, e.g. when adding a trailer. It also highlights that the size and the shape of the vehicle side may be mainly responsible for the high longitudinal air drag sensitivity to crosswinds for large vehicle combinations. [ABSTRACT FROM AUTHOR]

Controlled de-orbiting is crucial for a low earth orbiting (LEO) satellite or capsule intending to land in a desired location and to prevent damage to people and property on the ground caused by debris. Drag modulation is one possible mechanism to control de-orbiting, exploiting atmospheric drag variation to reduce the necessary orbital energy from the initial conditions to the re-entry interface. In this context, this paper proposes a novel targeted de-orbiting Artificial Neural Network (ANN) and drag-based guidance algorithm for a LEO artificial satellite. It relies on the combination of empirical and analytical relations with Deep Neural Networks (DNNs) to estimate the main parameters of the optimal control law in real time. The training set is composed of several optimal control solutions generated with a previously developed optimal control algorithm, exploiting the formulation in equinoctial modified orbital parameters to manage the large time scale of the problem and the computational cost. An innovative procedure for the training set generation led to the achievement of general results with a limited number of samples. The successful outcome of the guidance algorithm on over 1000 cases demonstrates its robustness and generalization of results. To conclude, a Linear Quadratic Regulator (LQR) feedback control is applied to one case to deal with a more realistic and uncertain density model. • Analytical optimal guidance for a satellite de-orbiting from Low Earth Orbit. • A novel approach based on Deep Neural Networks. • Prediction of the key parameters of the optimal control law in real time. • A Monte Carlo analysis showed the algorithm's robustness and generalization. • Successful feedback control thanks to a Linear Quadratic Regulator (LQR). [ABSTRACT FROM AUTHOR]

Plume rising from wildfire due to the buoyancy generated by the heat released from the fire is a crucial phenomenon to model for a correct description of smoke dispersion within the atmosphere. During the rise, the plume experiences the drag of external air which limits the rising itself. In this work, we investigate the dependence of the hybrid Eulerian-Lagrangian plume rise scheme embedded in the Lagrangian stochastic particle model SPRAY-WEB on the drag coefficient and on the horizontal resolution of the plume rise grid. We test four different drag coefficient models depending on the Reynolds number of the cells as well as a constant drag coefficient. As for the horizontal resolution, we use three different horizontal cell sizes: 200 m, 400 m, and 600 m, namely roughly a quarter, a half, and three-quarters of the source size. We compare the simulation results with the observations taken during a field experiment performed in Idaho organized by the US Environmental Protection Agency, where they collected lidar data and aircraft CO concentration measurements. We found that the drag coefficient influences mainly the plume near the source, where the drag role is more important due to the higher vertical velocities. It has also turned out that the best cell-to-source size ratio for our purpose is one to two. [ABSTRACT FROM AUTHOR]

The floating structure of floating photovoltaic can be attached by aquatic organisms, resulting in changes in the draft depth of the floating body, which can affect the resistance characteristics of the floating body at different water velocities. The analysis for the characteristics of flow field is the key to revealing the change law of resistance under different conditions. The k-∈ turbulence model which has been verified by water channel experiment is used to research the influence of draft depths, velocities and number of floating bodies for the drag in the paper. The research results show that the draft depth has more influence on the drag of the single floating body than on the velocity of water flow. The main reason is that the separation of the boundary layer produces a larger separation bubble, which increases the pressure difference between the front and back surfaces of the floating body, leading to a larger entrainment range and reflux velocity in the wake. The high flow velocity will enlarge the influence of the draft depth on the drag. The shielding effect of the tandemfloating bodies is reflected in the non-uniform fluctuation of velocity and pressure along the flow direction, which affects the wake development of the tandemfloating bodies, resulting in the typical spatial characteristics of resistance at different positions. The increase of the number of tandem floating bodies will further expand the difference of flow field, which can affect the resistance distribution law. The research results can provide theoretical support for the stability design of floating photovoltaic. [ABSTRACT FROM AUTHOR]

The escalating global energy demands have prompted a significant shift towards harnessing wind power as a sustainable alternative to conventional energy resources. This study explores the performance variations of Vertical Axis Wind Turbines (VAWTs) with a specific focus on their application in marine vehicles. Various parameters, including blade design, were systematically varied to analyse their impact on turbine efficiency. Computer-Aided Design (CAD) models were generated using SOLIDEDGE V2019 and Computational Fluid Dynamics (CFD) simulations were conducted using ANSYS R21. The investigation identified several key factors influencing turbine performance, with aspect ratio, the number of blades and drag emerging as primary contributors. Notably, turbines with lower aspect ratios demonstrated enhanced power output, while those with higher aspect ratios exhibited the opposite trend. The number of blades, however, displayed a nuanced relationship with performance, as an increase did not uniformly guarantee improved efficiency. Blade profile was identified as a critical factor, influencing the overall impact of blade quantity on turbine performance. Furthermore, the study revealed that augmenting the number of blades led to an increase in overall drag, affecting performance adversely. Conversely, reducing the number of blades resulted in heightened power output fluctuations due to intermittent wind interaction. The findings underscore the intricate interplay between turbine design parameters and performance, emphasizing the need for a comprehensive understanding when tailoring VAWTs for marine applications. [ABSTRACT FROM AUTHOR]

This study aims to investigate the inrun position in ski-jumping, in search for factors increasing the inrun speed without compromising the take-off. The inrun position of eight World Cup (WC) and fifteen Continental Cup (COC) ski jumpers were investigated in a wind tunnel at NTNU. A preferred position, replicating a jumper's position in competition, was measured for each athlete. Improvements, based on common sense aerodynamics, with the aim to improve the aerodynamic drag were executed. The aerodynamically best of these was compared with the preferred position. A numerical model simulating the inrun speed in ski-jumping hills was used to evaluate the impact the results will have in different hill sizes, for comparisons of drag measurements and inrun speed in competitions. In the preferred position, COC had 15.5% higher drag area than the WC athletes. In their best tested position, a group difference of 10.8% was found. These differences correspond with speed differences between 0.4 and 1.3 kmh−1, or 1–3 gates (as found by the numerical model). Group difference in drag was explained by a larger trunk angle for COC. Both groups improved from their preferred to their best position, due to reductions in thigh and leg angle. [ABSTRACT FROM AUTHOR]

This article considers forms of drag in Belgrade that are critical of contemporary Serbian society and analyzes ways in which drag both participates in, and critically relates to, the postsocialist transitional socioeconomic environment, especially the creative industries. Becoming a part of the creative industries (re)produces drag, as well as lesbian, gay, bisexual, and transgender subjects as consumers, while the 'becoming apart' of drag offers possible sites of resistance to the dominant cultural, social and economic model. As some performances – by the Ephemeral Confessions collective, Dajana Ho and Dragoslavia – are critical of both current forms of capitalism and of cis-hetero-patriarchal regimes of gender and sexuality, as well as of the ethno-nationalist narrative that has shaped the region of former Yugoslavia, analysis of the Belgrade drag scene results in a conceptualization of a critical practice that is immanent to what is being critiqued – immanent resistance. [ABSTRACT FROM AUTHOR]

Convection‐generated gravity waves (CGWs) transport momentum and energy, and this momentum is a dominant driver of global features of Earth's atmosphere's general circulation (e.g., the quasi‐biennial oscillation, the pole‐to‐pole mesospheric circulation). As CGWs are not generally resolved by global weather and climate models, their effects on the circulation need to be parameterized. However, quality observations of GWs are spatiotemporally sparse, limiting understanding and preventing constraints on parameterizations. Convection‐permitting or ‐resolving simulations do generate CGWs, but validation is not possible as these simulations cannot reproduce the CGW‐forcing convection at correct times, locations, and intensities. Here, realistic convective diabatic heating, learned from full‐physics convection‐permitting Weather Research and Forecasting simulations, is predicted from weather radar observations using neural networks and a previously developed look‐up table. These heating rates are then used to force an idealized GW‐resolving dynamical model. Simulated CGWs forced in this way closely resembled those observed by the Atmospheric InfraRed Sounder in the upper stratosphere. CGW drag in these validated simulations extends 100s of kilometers away from the convective sources, highlighting errors in current gravity wave drag parameterizations due to the use of the ubiquitous single‐column approximation. Such validatable simulations have significant potential to be used to further basic understanding of CGWs, improve their parameterizations physically, and provide more restrictive constraints on tuning with confidence. Plain Language Summary: Thunderstorms generate waves in the atmosphere that can generate turbulence at commercial aircraft cruising altitudes and further aloft. At these higher altitudes, they eventually break, not only generating turbulence, but also exerting forces that affect the large‐scale flows in the middle atmosphere. While these waves have been known to be important since at least the 1980s, they are difficult to observe. They can be simulated, but weather models do not simulate thunderstorms in the correct locations at the right times, meaning the simulated waves cannot be directly compared against observations. Here, weather radar observations are used as input to a look‐up table and a neural network to force realistic thunderstorm motions and waves within a simplified weather model. This method was able to reproduce a satellite‐observed case with notable skill. In one of the first simulations of thunderstorm‐generated waves comparable to satellite observations, these waves travel 100s of kilometers away from the thunderstorms, conflicting with assumptions made in weather and climate models. Key Points: If realistic convective diabatic heating is supplied at the correct places and times, GW‐resolving models can reasonably reproduce Convection‐generated gravity waves (CGWs)While location and type of convective storm do influence latent heating, these difference are of second order importance for CGW forcingDrag due to convection‐generated GWs from a compact source region is spread over O(1,000) km due to lateral propagation [ABSTRACT FROM AUTHOR]

Introduction: The objective of this study is to develop and simulate a double slotted morphed flap with the intention of reducing drag and enhancing lift, thereby leading to a smaller flap size and reduced weight. Methods: A flap was meticulously designed to accommodate conditions at Mach 0.2 and Reynolds numbers of 4.7×106. To conduct the simulation, ANSYS FLUENT flow solver and POINTWISE grid generator were utilized. The morphing technique employed involved adjusting both flap mean camber and flap slots, ensuring minimal flow interferences. By discretizing the flap mean camber line, various flap geometries were achieved. Results and Discussions: The findings reveal a significant enhancement in the airfoil's aerodynamic efficiency attributed to the implementation of the new flap design. The study shows that utilizing double-slotted morphing in the NACA 4412 airfoil at a 30° flap deflection angle increased the lift coefficient by 82% compared to the un-morphed state. A comparison of lift coefficients between this research and the NACA 4412 split flap at a 60° deflection angle indicates that the doubleslotted morphing in the NACA 4412 airfoil at a smaller deflection angle of 30° results in a 14% higher maximum lift coefficient. [ABSTRACT FROM AUTHOR]

The present experimental work is focused on designing and standardizing a direct method of measuring the drag force on a tapered cylinder in a water tunnel. The model considered in the present study is a tapered cylinder of 70:1 taper ratio (with a mean diameter( D m ) of 8 mm) placed in a water tunnel test section. The drag force is measured directly, which is acquired by using a force transducer setup (strain-gauge-based), augmented with a lever arm to amplify or attenuate the force. Multiple calibrations of the load cells were done to ensure the repeatability of experiments. The taper cylinder model is suspended inside the water tunnel and the drag force is obtained for various Reynolds numbers (based on mean diameter). It was found that the drag coefficient was ≈ 10-20 % less than a circular cylinder. [ABSTRACT FROM AUTHOR]

The present study investigates unsteady wake dynamics in flow past an oscillating cylinder. A two-dimensional computational analysis is undertaken for flow past a sinusoidally oscillating cylinder. Operating parameters like Reynolds number, forcing frequency, amplitude, and wavelength are systematically varied, and their effect on wake dynamics is investigated. Lift and drag coefficients are plotted with cylinder position to characterize the flow. The flow field is analyzed using Proper Orthogonal Decomposition (POD). POD mode shapes and Power Spectral Density (PSD) plots characterize the flow response to cylinder oscillations. The effect of frequency ratio is examined in achieving synchronized vortex shedding. Previous studies focus on two extremes- the cylinder is either stationary or oscillating with perfect phase-locking. Flow past an oscillating cylinder where Karman and forcing frequencies compete for dominance is rarely reported. This paper considers such a scenario and demonstrates how POD can identify coherent structures, their significance, and associated frequencies. Further, non-symmetric vortex shedding, which is not a common observation, is captured and discussed. Large amplitude and large wavelength regimes are investigated, which remained unexplored in previous research. Coherent structures associated with those regimes are identified. [ABSTRACT FROM AUTHOR]

This essay proposes Animal Drag as an activist performance in which a human critically and consciously performs animality to de-centre the human. Dress and adornment are key to its dissidence. Animal Drag's potential is demonstrated through an analysis of Terry Notary's performance of a nonhuman primate within Ruben Östlund's 2017 film The Square. Drawing on posthuman studies, scholarship on subordinated groups and from the field of animal studies, the reading of this performance shows how Animal Drag inherently queers humanist and essentialist notions of classification, particularly the human / animal divide. Paying homage to drag, the essay demonstrates how the material and social semiotics of performance can render transparent the constructions of race, coloniality, ability, and gender, as much as species -- in other words, "doing human". Through theories of dress and prosthesis, highlighting how techne facilitates in-between and "becoming" states, and affect theory, this article argues that humans and nonhumans might share vulnerabilities via Animal Drag. Culture is understood through language and dress, which have been mobilised to construct Otherness. As such, this essay posits that Animal Drag should take place within capitalist Culture industries, as both weapons and targets, to undress powers present and performed. Animal Drag is offered as both practice and theory, content and form. [ABSTRACT FROM AUTHOR]

This article presents the Investigation on unsteady fluid flow around an oscillating sphere-A Numerical and Analytical approach. The analytical expressions for angular velocity and temperature of the fluid around an oscillating sphere have been obtained in form of Bessel functions with suitable assumed boundary conditions. The numerical results in terms of angular velocity, temperature and pressure distribution for various values of the material parameters have been obtained using R-K method of 6th order with shooting methods with the help of MATHEMATICA ND solver. The influence of thermo-viscous flow parameters on angular velocity, temperature, pressure and drag on the boundary have been presented in form of tables and graphs. It may be noticed that the thermo-viscous effects are more predominant in the flow region around the boundary of the oscillating sphere. The R-K method with shooting method is the most powerful and elegant method to solve the governing equations related to the fluid dynamics problems. This method gives the accurate and valid results of highly complex coupled governing equations. The analytical results obtained are validated with this method in the present problem. The results obtained by this method gives more accurate, stable and converging to the analytical results. The numerical solutions of governing equations of present work have been obtained are compared with the existing analytical results and are found to be in excellent agreement. The present theoretical work will be hope fully for the better understanding of researchers and scientists and also it is useful in chemical and nuclear industries.

This paper examines the queer rural spaces in Julie Murphy’s 2021 young adult novel Pumpkin. In particular, it explores the concepts of rural-urban binaries, rural out-migration, and drag culture as they are related to the LGBTQ+ community. The author argues that Pumpkin creates a portrait of modern rural communities that confutes previous assumptions that queer people don’t exist in rural spaces, and if they do, they must leave in order to find acceptance and community.

The text grounds its methodology in Discourse Analysis. To do so, it mobilizes signifiers with the aim of discursively analyzing the artistic performance of a drag queen. The thesis presented argues that dressing up is a discursive mechanism that creates a symbolic punctum that conceals the traumatic reality of growing up unable to associate with the feminine. It concludes that the drag’s position, as a tension between masculinist formation and its opposite, represents a liminal, dissenting space of hybridity and transfiguration of pain, repression, and loss. The contribution lies in the fact that it is through this artistic practice that the subject of discourse resists and authorizes oneself to act, to signify.

O texto sustenta sua metodologia na Análise de Discurso. Para tanto, mobiliza significantes no intuito de analisar discursivamente a performance artística de uma drag queen. A tese apresentada é a de que montar-se é um mecanismo discursivo que cria um punctum simbólico que encobre o real traumático de crescer impedido de associar-se ao feminino. Conclui que o lugar da drag, como tensão entre a formação masculinista e o seu avesso, representa um espaço limiar, dissidente, de mestiçagem e transfiguração da dor, repressão e perda. A contribuição refere ao fato de que é por meio desse fazer artístico que o sujeito do discurso resiste e se autoriza a agir, a significar.

Damage to the leading edge in the form of dents due to bird strikes causes a decrease in the airfoil performance. Therefore, the current study provides a numerical analysis of the aerodynamic characteristics of the original NACA 2412 airfoil and the dent airfoil with depth variation. Several airfoils were compared for their lift and drag coefficients at an angle of attack of 0◦ to 6◦. The free air flow velocity was kept constant at the Reynolds number of 3.1 × 106. Computational fluid dynamics (CFD) was used, employing the k-ω SST turbulence model to obtain accurate calculations on the airfoil surface. The simulation results revealed that the dented NACA 2412 airfoil lift coefficient (CL) decreased while the drag coefficient (CD) increased, where the value varied with changes in the angle of attack and depth of the dent.