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During atmospheric entry, super-/hypersonic vehicles cross distinct atmospheric layers characterized by large density variations and thus experience different flow regimes ranging from free molecular, transition, slip, to continuous regimes. Due to the distinct modeling strategy between these regimes and complex physical phenomena appearing near the vehicles (boundary-layer/shock interaction, base-flow recirculation, etc.), assessing their aerodynamic properties may be difficult. The present work focuses on supersonic flows around sharp-base geometries in both continuous and slip-flow regimes and aims at highlighting the influence of both rarefaction degree and base geometry on the vehicles' aerodynamic features. For this purpose, three axisymmetric cone-cylinder geometries with right-angled, rounded, or flared rear parts are considered. Flow visualization, pressure, and drag measurements are carried out at Mach number Ma=4 and Knudsen numbers ranging from Kn=4×10-4 to 1×10-2 in the supersonic rarefied MARHy wind tunnel. The experimental data are compared with numerical results of simulations performed with a continuous-flow Navier-Stokes (NS) solver and two rarefied flows codes: a discrete-ordinate Bhatnagar-Gross-Krook (K) solver and a direct simulation Monte Carlo (SPARTA) solver. While the NS solver overestimates frictional drag as Kn rises, the rarefied K and SPARTA results show satisfactory agreement with experimental data. The latter numerical results highlight the main effects of rarefaction: as Kn increases, shocks become more diffuse, skin friction strengthens (leading to a significant increase in drag coefficients), and the extent of the base-recirculation decreases. Regarding the aft-body geometry, its influence on the base recirculation vanishes with increasing Kn. [ABSTRACT FROM AUTHOR]

Heavy-duty vehicle (HDV) platooning, facilitated by vehicle-to-vehicle communication, plays a crucial role in transforming logistics and transportation. It reduces fuel consumption and emissions while enhancing road safety, supporting sustainable freight strategies and the integration of autonomous vehicles. This study employs a hybrid approach combining wind tunnel experiments and Computational Fluid Dynamics (CFD) simulations to analyze HDV platoon aerodynamics. The approach has two sequential phases: single-HDV simulation validation and multi-HDV platooning simulation. In the first phase, a single HDV CFD simulation is validated against NASA's benchmarks, with optimized mesh generation, proper models, and conditions, and errors minimized below 1%. In the second phase, the validated model is used for multi-HDV platooning simulations, maintaining consistent mesh structures, physical models, and boundary conditions. Various platoon configurations are explored to assess the effects of speed, inter-vehicle spacing, and platoon size and position on aerodynamic drag, with virtual wind tunnel simulations evaluating drag coefficients. Our findings reveal that inter-vehicle spacing critically influences drag. An optimal range of 0.25 to 0.5-times the HDV length is identified to achieve an effective balance between safety and fuel efficiency, reducing platoon aerodynamic drag by 13–44% compared to single HDVs. While platoon speed is generally limited to impacting drag, it becomes more pronounced when an HDV platoon has very small inter-vehicle spacings, or in platoons exceeding five HDVs. Moreover, as the platoon size increases, the overall aerodynamic drag coefficient diminishes, particularly benefiting the rear HDV in larger platoons with smaller inter-vehicle spacing. These insights offer a comprehensive understanding of HDV platoon aerodynamics, enabling logistics enterprises to optimize platoon configurations for fuel savings, improved traffic flow, larger platoon formation, and enhanced transportation safety. [ABSTRACT FROM AUTHOR]

Subtle differences in aerodynamic drag, ice friction and sprint start, all influenced by the skill and physique of athletes, determine the descent time and hence competitive success in the sport of Skeleton. A trajectory based simulation was created by parameterising the geometry of the Altenberg Ice Track in Saxony, Germany to find the physically realistic descent time that captures the physics of the aerodynamic drag, ice friction and sprint start. A sensitivity study was used to analyse the influence of each factor on the overall performance down a fixed mid-line trajectory. Comparisons are made to the actual descent times to confirm applicability for a set of male and female sliders. It was found that the combined mass of the athlete and sled should be maximised within the rules, the initial velocity from the push should be as fast as possible, the aerodynamic drag should be optimised for each athlete and the ice friction of the runners reduced to their lowest limit. If each variable is optimum, then the final race standings will depend solely on the skill of the athlete traversing the ice track by finding the 'best' trajectory. [ABSTRACT FROM AUTHOR]

The present paper evaluates the performance of grid topologies and RANS turbulence models in predicting the aerodynamic drag coefficient of a 155mm artillery projectile by conducting steady-state computational research. The research is performed for Mach numbers from 0.5 to 3.0, assuming axisymmetric flow. Four distinct combinations of grid topology and turbulence model are investigated, where the O- and C-grid topologies are each paired with both the realizable k-ε and the SST k-ω models. Compared to the experimental data across the Mach number range, the combination of O-grid with k-ε model showed the smallest mean deviation of 1.64%, while the combination of O-grid with k-ω exhibited the largest mean deviation of 5.54%. In terms of drag component results, both turbulence models and grid topologies performed equally in predicting pressure and friction drag, with differences less than 6% in all Mach number cases. However, significant discrepancies were obtained in base drag prediction, especially between the two turbulence models, with differences reaching around 60% in the transonic regime. This was identified as the main contributor to the discrepancies in aerodynamic drag coefficient results among the four combinations. Furthermore, the findings indicate that the turbulence model selection impacts the zero-yaw drag prediction more than the grid topology, especially in the transonic and low supersonic cases.

To analyze the fuel balance and optimize the fuel efficiency indicators of wheeled vehicles (WVs) using mathematical models, developers require a large number of design parameters as input data. Among them are losses in the transmission, aerodynamic drag of the WVs and tire rolling resistance. Many methods are developed to investigate these parameters, both under bench test and road test conditions. Many of them are based on the analysis of decelerations in the process of WVs coasting in two or even three weight conditions. Therefore, in order to save time and money for the preparation and performance of studies on the assessment of resistance forces, a methodology is proposed which is based on the analysis of the results of WVs tests by the coasting method only in one weight state, at full mass.

The preliminary intention of this study is to comprehensively understand converting a conventional vehicle into a fully electric vehicle. In today’s technologically forward world of travelling, it is crucial for commuters to travel effectively and help maintain a sustainable environment. To accomplish this, the rider should travel as quickly and effectively as feasible. This study provides information on battery-powered electric scooters, including information on the controller, battery, hub motor and other components. Details on converting a scooter with an Internal Combustion (IC) engine into an Electric vehicle (EV) are provided in this work. This uses electricity as their main energy source. It also draws attention to the scooter's modifications. The battery can be charged by being ejected by the main system. ARAI AIS 039 (Rev 1): Electric Power Train Vehicles– Measurement of Electrical Energy Consumption is the standard used for testing the vehicle. When compared to a traditional vehicle, the scooter's electrical power can provide a longer range, higher performance and no emissions. Major Findings: The experimental range of the vehicle under ARAI test conditions is found to be 15km. The experimental top speed of the vehicle under a total load of 150kg is 30kmph. [ABSTRACT FROM AUTHOR]

This paper analyzes the components of the aerodynamic drag of a small-caliber bullet using a numerical simulation method. The analyses are applied to the M855 bullet. The turbulence model k-ε is used. The mesh size of 2.16 million elements is applied. The simulation method has been verified by comparing the obtained results with experimental data. The wave drag accounts for the largest proportion (about 50%), the friction drag accounts for the smallest proportion (from 10% to 15%), the base drag accounts for a significant proportion (from 35% to 45%) of the total drag at Mach number from 1.47 to 2.62. Two modified M855 bullets have been studied. The obtained results showed that the variation of increasing the length of the bullet nose is the most reasonable to be adopted. The method presented in this paper can be used in the projectile design process to optimize its shape for reducing the aerodynamic drag. [ABSTRACT FROM AUTHOR]

A non-watertight Ahmed body is adopted to examine the influence of geometrical defects on the aerodynamic drag. The Ahmed body, a standard automotive test model, is widely used in wind tunnel experiments to study vehicle aerodynamics. However, in real-world applications, vehicles often exhibit deviations from the ideal geometry due to manufacturing tolerances, wear, and other factors. The aim of this study is to quantify the impact of such geometrical defects on the aerodynamic drag. The research employs the lattice Boltzmann method (LBM) software to analyze the flow field around the Ahmed body with and without the introduction of geometrical defects. These defects are modeled as small holes in the shape of the body. The simulations are performed under the varying location and size of the holes to explore the aerodynamics phenomena. The results indicate that the location and size of geometrical defects can significantly alter the aerodynamic drag of the Ahmed body. The holes located at the rear of the Ahmed body rarely effect the aerodynamic drag. The holes at the top or bottom are found to have the most pronounced effect. The study also reveals that the influence of defects varies with their size, with large areas leading to more substantial changes in the aerodynamic drag. The results demonstrate that non-watertight geometry with small defects can be used to produce a reasonable drag coefficient compared to the results of watertight geometry. [ABSTRACT FROM AUTHOR]

The aerodynamic drag of high-speed trains has a negative effect on their running stability and energy efficiency. Since the shape of the high-speed train head closely influences its surrounding airflow, optimizing the head shape is the primary way to reduce the aerodynamic drag. However, existing optimization methods have limitations in parametrically describing the train head with enough details and fewer parameters. In this paper, we propose a novel parametric modeling method based on the approximate analytical partial differential equation (PDE) for the aerodynamic shape optimization of high-speed train heads. With this method, the detailed shape of the train head is controlled by four design parameters. To enhance the optimization efficiency, a two-stage multilayer perceptron (MLP) surrogate model is proposed to predict the aerodynamic drag coefficients of the high-speed train, and a classic genetic algorithm (GA) is adopted to optimize the total drag coefficient and generate the train head shape with good aerodynamic performance. The effectiveness of the proposed method is demonstrated through several comparison experiments. [ABSTRACT FROM AUTHOR]

Drag and lift are two important parameters to evaluate a vehicle's aerodynamic performance. Aerodynamic resistance (drag force Fd) prevents the movement of the vehicle and has a value proportional to the square of the velocity. That is, when the speed increases twice, the aerodynamic drag will increase fourfold. This article presents a plan to design a sport utility vehicle model with improved aerodynamics by using Ansys Fluent software to analyze pressure distribution areas that affect aerodynamics and the body. Based on the results obtained, the areas of stress and maximum pressure concentration have been identified. From this, a plan to improve the vehicle’s exterior design has been proposed. After many iterations of the design and model optimization process, the aerodynamic drag coefficient CD was reduced by 3.06% compared to the original model. The revised design option is equipped with an airflow diffuser under the vehicle; the lifting resistance coefficient has been reduced from 0.0902 to 0.038, equivalent to 58.2%. The new proposed design of the model has reduced the vehicle's frontal drag by 2.04%. The research results have determined the aerodynamic coefficients CD and CL of the model car. Based on the results received, it is possible to compare them with the manufacturer's announced parameters and propose new design options that still ensure aesthetics.

The pantograph is a critical instrument that significantly affects the aerodynamics of high-speed trains, posing a considerable challenge to the energy conservation and environmental protection of trains. This study explores the feasibility and efficiency of a jet-flow control technique in optimising the aerodynamic characteristics of the pantograph. A numerical method was adopted to investigate the effects of various jet-flow parameters, such as the jet positions, velocities and jet-slot widths, on the flow changes around the pantograph and subsequent reduction in aerodynamic drag of the pantograph. The results show that the impact of the jet position is negligible when the jet velocity is lower than the train speed. The aerodynamic drag reduction rate decreased with increasing distance from the pantograph as the jet velocity increased. When the distance between the jet slot and pantograph is less than 0.6 times the height of the pantograph, the aerodynamic drag reduction rate continuously increased with the jet velocity. As the jet slot moved away from the pantograph, the aerodynamic drag reduction rate initially increased rapidly with the jet velocity and then gradually decreased when the velocity surpassed 1.2 times the train speed. In addition, the aerodynamic drag of the pantograph decreased as the width of the jet slot decreased. However, the energy of the whole train can be only saved when the jet velocity is below 0.6 times the train speed. Findings in this study verified the effectiveness of the jet-flow method in reducing the aerodynamic drag of pantographs and provide important engineering guidance for the energysaving of high-speed trains. [ABSTRACT FROM AUTHOR]

Parasitic SAR formation can be flown at low altitude using smaller satellites and adding potential to conventional SAR mission From the orbital point of view, the main issue is related to the differential aerodynamic drag, which rapidly disrupts the formation. In this ambit, this paper proposes a case study of an along-track distributed parasitic receiver flying in formation with PLATiNO-1. Formation maintenance is the core contribution, highlighting how the active control of both altitude and in-plane anomalies leads to an unfeasible ΔV. Then, the active control of the altitude around the nominal value, which naturally controls anomaly shift, is proposed, modeled, and applied to the presented case study. It is shown that the annual ΔV can be reduced to the m/s range. [ABSTRACT FROM AUTHOR]

The pantograph is a critical instrument that significantly affects the aerodynamics of high-speed trains, posing a considerable challenge to the energy conservation and environmental protection of trains. This study explores the feasibility and efficiency of a jet-flow control technique in optimising the aerodynamic characteristics of the pantograph. A numerical method was adopted to investigate the effects of various jet-flow parameters, such as the jet positions, velocities and jet-slot widths, on the flow changes around the pantograph and subsequent reduction in aerodynamic drag of the pantograph. The results show that the impact of the jet position is negligible when the jet velocity is lower than the train speed. The aerodynamic drag reduction rate decreased with increasing distance from the pantograph as the jet velocity increased. When the distance between the jet slot and pantograph is less than 0.6 times the height of the pantograph, the aerodynamic drag reduction rate continuously increased with the jet velocity. As the jet slot moved away from the pantograph, the aerodynamic drag reduction rate initially increased rapidly with the jet velocity and then gradually decreased when the velocity surpassed 1.2 times the train speed. In addition, the aerodynamic drag of the pantograph decreased as the width of the jet slot decreased. However, the energy of the whole train can be only saved when the jet velocity is below 0.6 times the train speed. Findings in this study verified the effectiveness of the jet-flow method in reducing the aerodynamic drag of pantographs and provide important engineering guidance for the energy-saving of high-speed trains.

The aerodynamic drag of a high-speed train has a significant impact on its energy consumption. At high speeds, the pantograph is one of the primary sources of aerodynamic drag for the train. To enhance train operation characteristics and reduce aerodynamic drag, two optimized pantograph models with bionic non-smooth grooves beneath carbon slide plates were designed based on bionic non-smooth theories, using shark skin as the bionic object. The Navier-Stokes equation and k-ϵ turbulence model were adopted to simulate the flow field structure of two pantograph optimized models. The results show the structure of pantograph head has a significant effect on its separation point of the boundary layer, the wake flow and the tail vortex area. Compared to the pantograph head with arc-shaped grooves, the pantograph head with V-shaped grooves exhibits a more significant backward movement of the boundary layer of separation point. This results in a more stable wake flow and a more pronounced reduction in the area of the tail vortex. Furthermore, incorporating V-shaped grooves beneath the carbon slide plate resulted in an average rate of drag reduction increase of 4.9% for the pantograph head and 4.7% for the pantograph compared to the original pantograph.

Reducing the aerodynamic drag and noise levels of high-speed pantographs is important for promoting environmentally friendly, energy efficient and rapid advances in train technology. Using computational fluid dynamics theory and the K-FWH acoustic equation, a numerical simulation is conducted to investigate the aerodynamic characteristics of high-speed pantographs. A component optimization method is proposed as a possible solution to the problem of aerodynamic drag and noise in high-speed pantographs. The results of the study indicate that the panhead, base and insulator are the main contributors to aerodynamic drag and noise in high-speed pantographs. Therefore, a gradual optimization process is implemented to improve the most significant components that cause aerodynamic drag and noise. By optimizing the cross-sectional shape of the strips and insulators, the drag and noise caused by airflow separation and vortex shedding can be reduced. The aerodynamic drag of insulator with circular cross section and strips with rectangular cross section is the largest. Ellipsifying insulators and optimizing the chamfer angle and height of the windward surface of the strips can improve the aerodynamic performance of the pantograph. In addition, the streamlined fairing attached to the base can eliminate the complex flow and shield the radiated noise. In contrast to the original pantograph design, the improved pantograph shows a 21.1% reduction in aerodynamic drag and a 1.65 dBA reduction in aerodynamic noise. [ABSTRACT FROM AUTHOR]

Investigations (mainly those performed by the authors) of air blowing through a perforated section on a body of revolution with a large aspect ratio in an axisymmetric incompressible flow are summarized. Result of numerical and experimental studies of the flow properties, efficiency of the turbulent boundary layer control and prospects of using it for a body of revolution at low subsonic velocities equivalent to the take-off and landing regimes for a modern subsonic cargo aircraft are analyzed. [ABSTRACT FROM AUTHOR]

Aerosols in advanced reactors are considered the primary carriers of radioactive nuclides, and the motion behavior of aerosol particles in the near-wall region of reactors is of significant importance for reactor safety analysis. For example, for a high-temperature gas-cooled reactor (HTGR), the graphite dust generated due to the operation of spherical fuel elements may move in the primary circuit under the drag action of the coolant, which will result in deposition, resuspension and then affects the reactor performance. The aerodynamic drag produced by the interaction between fluid and particles during the near-wall motion of aerosols was studied, and the computational fluid dynamics method for near-wall drag numerical calculation was employed in this paper. In order to construct the model for non-spherical particles, several spherical particles (3-5) were combined into non-spherical particles according to the rod-shaped dust particle samples obtained from samples in high-temperature gas-cooled reactor. Based on the geometric model of the particle, the Realizable k-ε turbulence model was used to simulate the Reynolds stress of the mainstream fluid, and the enhanced wall treatment model was used to calculate the turbulent viscosity in the near-wall and around particle region. The three-dimensional incompressible steady SIMPLE algorithm was employed for the computations. The results show that the drag force exerted by the airflow on the particles can be divided into two components, namely, the pressure difference drag force and the shear drag force. Compared to the drag force on the particle under uniform inflow in an infinite space, the near-wall particles withstand a greater aerodynamic drag (enhancement factor) due to non-uniform velocity distribution, offset pressure distribution, and asymmetrical flow vortices. As particles get closer to the wall, the effect of aerodynamic drag enhancement becomes more pronounced. Moreover, the enhancement effect of aerodynamic drag on the near-wall particles becomes more evident as the non-spherical particles elongate and the flow-facing area (angle of attack) increases. Finally, considering the shape of non-spherical rod-shaped particles and the drag enhancement due to near-wall shear flows, the least squares method was applied to fit the expression using an exponential format for the enhancement factor of near-wall aerodynamic drag for different particles. It shows that the difference of drag enhancement factors at the same δ (dimensionless particle-wall distance) among different particles in the near-wall region usually does not exceed 10%. Thus, in most cases, the enhancement factor of spherical particles can be used to estimate non-spherical particles, roughly. This study provides a basis for investigating particle motion characteristics in the near-wall region of advanced reactors.

A relatively high aerodynamic drag is an important factor that hinders the further acceleration of high-speed trains. Using the shear stress transport (SST) k-ω turbulence model, the effect of various vortex generator types on the aerodynamic characteristics of an ICE2 (Inter-city Electricity) train has been investigated. The results indicate that the vortex generators with wider triangle, trapezoid, and micro-ramp arranged on the surface of the tail car can significantly change the distribution of surface pressure and affect the vorticity intensity in the wake. This alteration effectively reduces the resistance of the tail car. Meanwhile, the micro-ramp vortex generator with its convergent structure at the rear exhibits enhanced flow-guiding capabilities, resulting in a 15.4% reduction in the drag of the tail car. [ABSTRACT FROM AUTHOR]

Heat transfer and aerodynamic drag of novel small-sized heat sinks with lamellar fins, designed for electronic cooling, were experimentally investigated under conditions of forced convection in the range of Reynolds numbers 1 250-10 500. It was found that a gradual reduction in the fin spacing from 6 mm to 3 mm with a 29° angle of taper between the outermost fins leads to an increase in the heat transfer intensity by 15-32% with a significant increase in aerodynamic drag compared to the surface with a constant fin spacing of 6 mm. Incomplete cross-section cutting of fins at the relative depth of 0.6 in addition to the gradual reduction in the fin spacing provides aerodynamic drag decrease by 5-20% and increase of heat transfer intensity by 18-20% in comparison with the similar heat sink without fins cutting. Proposed novel designs of heat sinks enabled us to decrease by 7°C-16°C the maximum overheating of the heat sink's base in the flow speed range from 2.5 m/s to 7.5 m/s at constant heat load. To ensure a constant value of maximum overheating of the heat sink base the inlet flow velocity for the surface with constant fin spacing should be 1.6-2 times higher than that for the heat sink with 29° taper angle between outermost fins and partially fins cutting. In this case, the aerodynamic drag for the latter will be higher only by 1.6-2.7 times, which is quite acceptable. [ABSTRACT FROM AUTHOR]

This paper presents a computational fluid dynamics (CFD) study investigating the aerodynamic effects of a retractable flap on a passenger vehicle. The predominant aim of the study is to evaluate the impact of the flap's deployment on the vehicle's aerodynamic performance, specifically focusing on improving the overall braking efficiency by increasing the aerodynamic drag. The CFD simulations were conducted using the ANSYS, by employing a validated turbulence model and a detailed vehicle geometry. The CFD results demonstrated that the deployment of the retractable flap resulted in noticeable changes in the vehicle's aerodynamics. The flap's presence altered the flow field around the vehicle, increasing the overall aerodynamic drag. Also, the flap's angle significantly affected the aerodynamic performance, with certain angles resulting in more favourable flow patterns and reduced drag coefficients. [ABSTRACT FROM AUTHOR]

Flow around a body moving at a high subsonic velocity in a tube filled with rarefied gas is studied. This aerodynamic problem is considered as applied to the task of designing a high-speed vacuum transport at finite Knudsen numbers. Parameters that are close to target characteristics of such systems are chosen, more precisely, speed of about 1000 km/h, significant transverse size of the body, and nitrogen–oxygen mixture (air) as the filling gas are chosen. The problem was solved in a three-dimensional statement. [ABSTRACT FROM AUTHOR]

THE RELEVANCE of the research topic is due to the existence of an environmental problem associated with harmful emissions into the atmosphere. The most highly efficient are electrostatic precipitators and fabric filters (~90-99.5% capture). Against the background of these devices, inertial one’s lag behind both in terms of their catching efficiency and the catching spectrum of the ash particle size distribution. The research carried out in the article is aimed at creating such an inertial apparatus that would have both minimal resistance and high efficiency. PURPOSE. Consider the possibility of reducing aerodynamic resistance by changing the design of the device, namely, by increasing the diameter of the inlet pipe in the inertial-vacuum ash collector. Consider a number of other ways to further reduce the aerodynamic drag of the apparatus. To identify the prospects and assessment of capital costs for the reconstruction of the ash collector. METHODS. When solving the problem, the method for calculating the dynamics of a dispersed flow in an inertial-vacuum ash collector, implemented by the MFD, was used. RESULTS. The article describes the relevance of the topic, considers the results of a numerical calculation. The calculation of the influence of boundary conditions, which include the flow rate at the inlet, thermal and hydraulic parameters of the flow of exhaust gases at the inlet to the ash catcher, in relation to the desired pressure drop across the apparatus, as well as the collection efficiency, was made. This article describes the process that results in a change in the hydraulic characteristics along the flow part of the IVAC. CONCLUSION. A change in the design of the apparatus leads to a decrease in the resistance of the IVAC, while these changes are extremely sensitive to the effect on the degree of purification. Calculations have shown that this method justifies itself in terms of reducing resistance. The pressure drops ranges from 279.8-1273 mm. water. pr. The convergence of the iterative calculation, taking into account the quality of the grid, provides flexibility, is achieved by fewer iterations, but the time spent on the calculation does not decrease.

The issues related to improving the efficiency of automatic ventilation control systems of mines that regulate the air supply to the mine in accordance with the need are considered. During the tests of such a system in the 3RU mine of OAO Belaruskali, the shortcomings of its existing, implementation, associated with the incorrect choice of the most difficult-to-ventilate direction, were revealed. The possibilities of implementing a control strategy, in which the system automatically determines the optimal configuration of the operating modes of fans and regulators, are demonstrated. As an alternative to the implemented algorithms, it is proposed to use a fuzzy control device to account for the nonlinearity of the dependence of the input and output parameters of ventilation equipment and to set the conditions for the optimal operating mode of the system in a declarative form. To assess the effectiveness of the proposed approach, the data of simulation modeling of the current ventilation mode and the transition from one ventilation mode to another are analyzed with comparison with the actual data of the system operation. The simulation results show that the use of an upgraded control scheme for the main ventilation fan based on fuzzy logic in the implementation of automatic ventilation control systems makes it possible to eliminate the possibility of a shortage of fresh air in the regulated directions of its movement, as well as excessive power consumption of the main ventilation fan.

Parasitic SAR formation can be flown at low altitude using smaller satellites and adding potential to conventional SAR mission From the orbital point of view, the main issue is related to the differential aerodynamic drag, which rapidly disrupts the formation. In this ambit, this paper proposes a case study of an along-track distributed parasitic receiver flying in formation with PLATiNO-1. Formation maintenance is the core contribution, highlighting how the active control of both altitude and in-plane anomalies leads to an unfeasible ΔV. Then, the active control of the altitude around the nominal value, which naturally controls anomaly shift, is proposed, modeled, and applied to the presented case study. It is shown that the annual ΔV can be reduced to the m/s range.

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The problem of relative drift elimination between the satellites in the swarm is considered in the paper. The proposed decentralized control takes into account a communication constraint such as limited size of communication area. Only the satellites within the communication area can be identified by relative motion determination system. The control aim is to eliminate the mean relative drift between all the satellites inside the communication area. The purpose of the work is to study the performance of the proposed decentralized control algorithm. It is shown that the system matrix of differential equations for the vector of relative drifts is related to the Laplacian matrix of the communication graph. In the case of the connected swarm, all but one eigenvalues of the system are negative, and the remaining one is equal to zero. It means that all the relative drifts converge to the same value under the proposed control. The speed of convergence is defined by the minimum absolute eigenvalue that depends on the graph topology. The initial drift and the convergence speed make it possible to estimate the communication distance that provides the connectivity of the graph. Considering normally distributed errors of the initial velocity after the launch, it is possible to estimate the distance between any two satellites after the convergence. It allows us to estimate the communication distance that ensures the relative drift elimination between all the satellites in the swarm. The obtained estimations are validated using Monte Carlo simulations. In numerical simulations the swarm of 3U CubeSats in low-Earth orbit is considered. The decentralized control is implemented by differential aerodynamic drag via the change of cross-sectional area using onboard reaction wheels. • Problem of relative drift elimination between satellites in the swarm is considered. • The proposed decentralized control takes into account a limited communication area. • Estimation of the communication area size that guarantees convergence is derived. • Analytical estimation of communication distance is obtained using graph theory. • Performance of swarm control by differential drag is studied numerically. [ABSTRACT FROM AUTHOR]

Aerodynamic collision avoidance manoeuvres provide an opportunity for satellites in Low Earth Orbits to reduce the risk during close encounters. With rising numbers of satellites and objects in orbit, satellites experience close encounters more frequently. Especially those satellites without thrusting capabilities face the problem of not being able to perform impulsive evasive manoeuvres. For satellites in Low Earth Orbits, though, perturbing forces due to aerodynamic drag may be used to influence their trajectories, thus offering a possibility to avoid collisions. This work introduces a tool for the analysis of aerodynamic collision avoidance manoeuvres for satellites in circular Low Earth Orbits. Current space-weather data are employed to estimate the density the satellite encounters. Achievable in-track separation distances following a variation of the ballistic coefficient through a change in attitude are then derived by evaluating an analytical equation from literature. Considering additional constraints for the attitude, e.g., charging phases, and uncertainties in the used parameters, the influence of a manoeuvre on the conjunction geometry and the collision probability is examined. The university satellite Flying Laptop of the University of Stuttgart is used as an exemplary satellite for analysis, which show the general effectiveness of evasive manoeuvres employing aerodynamic drag. First manoeuvring strategies can be deducted and the influence of parameter uncertainties is assessed. • Analysis of effects of collision avoidance manoeuvres using aerodynamic drag. • Consideration of additional constraints on the satellite attitude. • Consideration of uncertainties in respective parameters. • Applicable to every satellite able to change its ballistic coefficient. • Proved feasibility and further analyses for the university satellite Flying Laptop. [ABSTRACT FROM AUTHOR]

A full-scale square-back Ahmed body is analysed experimentally and numerically for a free-stream flow velocity of 45 m / s corresponding to a Reynolds number R e H = 7. 7 × 1 0 5 . Numerical simulations are performed for matching inflow conditions and different turbulence models. The main goal of this study is to examine the effectiveness of the Delayed Detached Eddy Simulations and the Reynolds Averaged Navier–Stokes k − ω SST turbulence model to capture the mean flow physics. Local and global aerodynamic parameters are compared with experimental results, including boundary-layer parameters evolving over the roof, the wake characteristics, the shear layer, and the mass entrained into the wake. A particularly good agreement is found between the experiment and the DDES. An in-depth analysis of the shear-layer growth, mass-entrainment and momentum budget analyses along the recirculation region interface, allow for identifying and quantifying the differences in predicting drag and the mechanisms at stake between the different approaches. The momentum budget, performed on the experimental data shows that pressure can be accurately obtained from experiments and closely follows that computed from high-fidelity numerical simulations. These results confirm the effectiveness of DDES in studying flows at high Reynolds numbers. The mass/momentum budget along the recirculation-region interface is also found as a possible mean to quantify road vehicle's aerodynamic performances, naturally extending to more complex geometries. [ABSTRACT FROM AUTHOR]

This paper expands upon the state of the art in nonlinear modeling of automotive air conditioning systems. Prior models considered only the effects of the refrigerant compressor and the condenser fan. There are two new aspects included here. First, we create a mathematical model for front-end underhood airflow, considering vehicle speed, condenser fan rotational speed, and active grille shutter position. In addition, we present a new model for the power consumption of the vehicle associated with aerodynamic drag caused by underhood flow, as well as a fan power model which accounts not only for changes in rotational speed but also changes in flow rate. The models developed in this paper are coded in MATLAB/Simulink and assessed for various vehicle driving conditions against a higher-fidelity vehicle energy management model, showing good agreement. By including the active grille shutters as a controllable actuator and the impact of underhood flow on vehicle drag and fan power consumption, control schemes can be developed to holistically target reduced energy consumption for the air conditioning system and, thus, improve the overall vehicle energy efficiency.

Increasing greenhouse gases & air pollution are a global threat. Global forums are aggressively emphasizing on reducing the dependence on non-renewable resources. Battery Electric vehicle are among the initial initiative to reduce dependency on fossil fuels, and this demands more research to understand the energy requirements of a vehicle under different driving conditions. The performance of an Electric Vehicle depends on varying drive conditions and the Power Electronic Controller is primarily responsible for its sustainable operation. In this paper, a novel mathematical model is proposed to analyze the performance of an electric vehicle under different driving conditions. The model is simulated at different driving speeds keeping other longitudinal, lateral, and vertical parameters fixed. Rolling resistance forces, aerodynamic drag force, gradient force, total driving force, driving torque, and power requirements at different speeds have been calculated under standard driving conditions. The rolling resistance increases by 2.16 times with a change in the vehicle speed from 40 kmph to 120 kmph. The aerodynamic drag force increases ten times with a 10-degree gradient. The battery operating temperature is critical in vehicular performance, a hybrid Pneumatic-Liquid Thermal Management System is proposed to maintain battery operating temperature. Performance of the proposed model is simulated and found to be in line with the existing standards. This study concludes that road conditions, tyre pressure, velocity of travel, wind velocity, and temperature significantly influence the performance of an electric vehicle.

Problem. The tendency to reduce Engine displacement, which has emerged in recent years in the global automotive industry, is due to the need to improve the environmental situation and energy efficiency of vehicles. Goal. The aim of the study is to increase the energy efficiency of vehicles by rationally reducing the maximum effective engine capacity. Methodology. In the paper authors used the method of partial accelerations implemented in a mobile registration and measurement complex, which allowed authors to obtain an improved formula for calculating aerodynamic drug. Experimental studies of car aerodynamics were also conducted. Results. In the study presents the results of the authors' research, which made it possible to prove the possibility of reducing the e internal combustion engine capacity while maintaining the specified maximum speed and the specified level of indicators of the car dynamic properties. Originality. The relationship between the use of maximum engine capacity and the relative change in the effective specific fuel consumption of a carburetor gasoline engine, with direct injection of gasoline and diesel were determined. Practical value. Calculations performed on the example of the ZAZ-1103 "Slavuta" car showed that a rational reduction in effective engine capacity allows to reduce fuel consumption by 9.5% for carburetor gasoline engine, and for an engine with direct injection of gasoline by 6.7 % and for diesel engines, by 20.3%.

The influence of different inter-carriage gap configurations, including end wall geometries (3 cases) and gap spacings (0, 5, 8, 10, 15, 20, and 30 mm), on the aerodynamic characteristics of a wind-tunnel train was investigated. The shear stress transport (SST) k - ω turbulence model was employed to determine the airflow features of the train at Re = 2.25 × 106. For validation, the numerical drag force and pressure distributions on the streamlined heads were compared with the experimental benchmark of wind tunnel experiment. The numerical data show that substantial variations in the flow fields, pressure distributions and aerodynamic forces are observed between the trains with and without gap spacings, no matter which configuration is employed. As the gap spacing increases, the airflow along train body rushes into the gap easily, causing the formation of vortices at the gap between the internal and external windshields. The decreasing restriction of flow in the gap also contributes to the pressure differences on the end walls. With the increase of gap spacings, the pressure on both of the first and second inter-carriage gaps is decreased, and it on the first one is a little higher than that on the second at each gap spacing. The end wall geometry affects the flow structures around the train, especially in the region below half-height of the train. This results in a difference in the boundary layer thicknesses and drag contribution in all cases. The discrepancy of end wall geometry causes a substantial variation in the aerodynamic drag between different cases. As gap spacing increases, the aerodynamic drag of the head car decreases, while those of the middle and rear cars increase significantly. When the three cases are compared, the discrepancy of the total aerodynamic drag of Case 1 is the smallest when compared to the base case with a minimum of 0.03% at 10 mm gap spacing and followed by 0.05% at 8 mm. Therefore, to determine the aerodynamic forces for high-speed trains with fully enclosed inter-carriage configuration in wind tunnel test, having a high comparative value as the actual trains, the end wall geometry in Case 1 is recommended with a gap spacing of 10 mm or 8 mm. [ABSTRACT FROM AUTHOR]

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The Hyperloop system is a new and innovative mode of transportation in which high-speed pods move through near-vacuum tubes. The multi-pod Hyperloop Systems are essential for increased transportation capacity. In this study, a multi-pod Hyperloop System was analyzed using numerical simulations at different values of the distance between the pods (i.e., 2 L–3.5 L). The pressure and velocity flow fields and the aerodynamic characteristics of the pods were analyzed for four different flow speeds, that is, 100, 200, 300, and 400 m/s, using unsteady compressible flow conditions. The simulation results indicated that the pressure waves generated across the pods play a significant role in the determination of the aerodynamic characteristics of the pods. Increasing the distance between the pods results in the delay of the pressure wave interaction. The aerodynamic drag increases on the first pod with the increase in the distance between the pods due to an increase in the pressure gradient. In contrast, the aerodynamic drag decreases across the second pod with the increase in the distance between them. So, the distance between the pods is a critical factor that should be considered when designing the Hyperloop System with more than one pod. [ABSTRACT FROM AUTHOR]

This research investigated an alternate method for establishing the complex coefficients used in an electric vehicle's mathematical energy consumption model. While other methods for creating electric vehicle energy models exist, it would be beneficial to have a rapid and inexpensive technique that remains accurate. Producing a mathematical energy model for such a vehicle has the challenge of determining its aerodynamic drag and rolling resistance coefficients. Currently and most often, expensive and tedious (time-consuming) methods are used to find these coefficients. Computational fluid dynamics (CFD), wind tunnel testing, and extensive mathematics make this objective challenging. For this work, a solar-powered electric vehicle provided the source data to derive its coefficients cost-effectively and efficiently. Data were collected during a road test of the solar electric vehicle from South Africa to Namibia stretching over 2000 km, in which all required energy variables were recorded. The collected data were used in an optimisation routine to establish the two coefficients by minimising the actual and modelled energy consumption error and controlling the driving speed. The outcome of the optimisation routine produced accurate coefficients with a final error value of less than 5% when applied to a validation data set not used during optimisation. With minor modifications, this method may be integrated into any electric vehicle computer system to autonomously identify its two hard-to-find coefficients while driving, which can be used to provide an accurate and realistic driving range estimation to the driver. [ABSTRACT FROM AUTHOR]

The emergence of Electric Vehicles (EVs) is a turning point in decarbonizing the road transport sector. In spite of the various apprehensions of the customers, such as range anxiety, long charging times, higher costs, and the lack of charging infrastructures, EVs have managed to considerably penetrate into the market. Appreciable subsidies in EV purchase and possibilities of renewable energy-based local charging equipment have encouraged more and more people to own EVs. Electrifying road transport also calls for scaling up of all stages of the supply chain as it involves a lot of raw materials and critical metals used for battery technology. One of the most important factors determining the range of an EV is the energy density of the battery, which has reached over 300 Wh/kg, from 100-150 Wh/kg a decade ago. This clearly means that the same vehicle can travel double the distance with the same mass. Understanding and modeling the energy consumption in an EV is quintessential in alleviating the fear of range anxiety. This paper presents a detailed mathematical equation-based energy consumption analysis of a particular EV model for Indian roads. Very few researchers have worked on drive cycles suitable for India. The novelty of the current work is that the energy consumption calculation can be worked out for any EV model or vehicle type through simple mathematical equations. [ABSTRACT FROM AUTHOR]

A simple model consisting of a mirror-housing and its cylindrical foot is applied to represent the automobile side-view mirror that causes unwanted aerodynamic noise and wind drag during high-speed driving. An additional slot is made on the solid foot to modify the flow around the mirror and thus reduce the side wall pressure fluctuation and aerodynamic drag. Flow fields and wall pressure fluctuations of these side-view mirror models have been investigated experimentally in a wind tunnel. The airflow rate through the slot varies with the changing of the slot area. Wall surface pressure sensors, particle image velocimetry (PIV), and six-component balance were applied to measure the acoustic and flow characteristics. The results demonstrated that, with the increase of slot airflow rate to 30%, the side wall pressure fluctuations were reduced by 5.1 dB and the drag coefficient decreased by 10.2%. The PIV measurements showed that the vortex cluster center behind the mirror was moved upward from the wall surface due to the slot airflow injection into the wake. The turbulent kinetic energy in the side-view mirror wake near the wall decreased with the increment of the airflow rate, reducing the side wall pressure fluctuations and thereby suppressing the noise generation.

The relevance of the study is caused by the need to develop resource-saving technologies for forced ventilation of dead-end drifts related to ensuring the safety of air ducts during blasting. The solution to the problem lies in the development of technical solutions that make it possible to remove the end of the air duct from the zone of damaging effects of flying fragments of rock, moving it away from the dead-end face to a safe distance without violating the safety rules. Purpose: to develop a resource-saving method of dead-end drift ventilation, which provides the increase of the ventilation range by means of the kinetic energy of the air jet flowing from the booster fan with a mixing chamber. Objects: dead-end drifts. Methods: analytical and numerical modeling of the processes of air ejection and propagation of a constrained overlaying air jet directed to a dead end; comparative analysis of experimental data and simulation results. Results. The analysis of experimental data on the ventilation of dead-end drift by the ejection method with the lag of the end of the pipeline from the dead-end face was carried out. It is noted that the experimental dependencies obtained by various researchers for determining the range of the ventilation jet do not allow us to make an unambiguous conclusion about the permissible lagging distance due to too large spread in the values ​​of the proportionality coefficient between it and the transverse dimension of the drifts. It was established that the reason for the scatter is the neglect of the dependence of the jet range on its initial velocity and flow rate, which is the less pronounced, the less constrained the jet is. The possibility of increasing the constraint and flow rate of the jet by ejection suction of the return air flow into the mixing chamber installed before the end of the pipeline is considered. The paper introduces the analytical model of the operation of an ejector installation with a permeable bulkhead, based on the results of which an increase in the jet flow rate due to recirculation was estimated. Despite the small value of the ejection coefficient, the numerical simulation of the process showed an unexpectedly strong increase in the ventilation range with an increase in the initial jet velocity in the real range, and the required pipeline lag result of 50 meters was achieved. It is shown that the proposed resource-saving method of forced ventilation of dead-end drifts requires a preliminary procedure for selecting and optimizing the geometric dimensions of the pipeline, mixing chamber and air flow, because in numerical simulation, both insufficient ventilation depth and loss of stability with the collapse of a single circulation vortex were observed during excessively intense air movement.

Platooning has emerged as a promising approach to enhancing the fuel efficiency of vehicles, but determining the inter-vehicular distance that achieves the minimum consumption remains a challenge. In this article, an algorithm is proposed that employs extremum seeking control integrated with the prescribed performance control technique to find the optimal inter-vehicular distance. The algorithm utilizes the predecessor-following architecture to track the desired distance while minimizing the estimated aerodynamic drag coefficient to seek the optimal value. To estimate the coefficient, an observer is designed. Simulation results are presented to demonstrate the effectiveness of the approach. The proposed algorithm exhibits a significant improvement over existing methods that do not incorporate prescribed performance. Consequently, our scheme provides a valuable contribution to the field of platooning and paves the way for future research directions. [ABSTRACT FROM AUTHOR]