Influence Of Aerodynamic Forces Research Articles

Моделювання процесу парашутування літака на злітно-посадкову смугу при його посадці

The landing of an aircraft is an unknown part of its flight, and at this stage, the highest number of accidents and even disasters are observed. It should be noted that the movement of the aircraft in its airspace, when it is under the influence of aerodynamic forces, gravity, and engine thrust, is quite accurately modeled by various authors and presented in printed sources. The peculiarities of the aircraft’s movement during air-to-ground landing, i.e., at the moment of parachuting directly onto the runway, are insufficiently studied. The influence of parachuting conditions on post-landing stability has barely been studied. The subject of study in this article is the modeling of the parachuting process under conditions of aircraft landing. The goal of this study is to develop and test mathematical and simulation models of the aircraft’s movement during its parachuting from the alignment zone to the runway and to ensure the stability of longitudinal movement at the moment of the first landing impact and subsequent movement. Tasks: analyze the characteristics of the landing distances of transport category aircraft; establish the features of the parasailing stage of the aircraft during landing; develop a parametric model of the aircraft in its parachute configuration; establish conditions for modeling shock-absorbing landing gear; and, based on general and simulation models, establish zones of longitudinal movement stability of the aircraft after the first landing. Based on the results of experimental studies, the proposed mathematical model of the aircraft in landing configuration and the simulation model of participation in the landing of shock-absorbing landing gear systems quite reliably (compared to experimental data) estimate the aircraft’s movement at the moment of its touchdown and subsequent roll. This means that mathematical modeling can avoid repeated bounces during landing, ensure stability of longitudinal aircraft movement, reduce the length of the unbraked roll, and decrease the required runway length during aircraft landing. Conclusions: By analyzing normalized landings, the six most characteristic stages in the landing distance of transport category aircraft have been identified. A method of mathematical modeling of aircraft movement during parachuting onto the runway, considering not only the glider’s characteristics but also the features of the landing gear shock-absorbing systems, allows evaluating the parameters of parachuting that ensure stability of longitudinal aircraft movement after the first impact on the landing gear. Using the example of the An-140 aircraft, it is demonstrated how the values of brake wheel stability parameters are ensured and how the parachuting speed affects the length of its landing distance.

Numerical Study on the Water Takeoff Performance of Unmanned Seaplane

The research on the water takeoff performance of unmanned seaplane is of great significance to its overall optimization design and taxiing stability control system. This paper proposes a new numerical method for solving the water takeoff performance of unmanned seaplane. The aerodynamics and hydrodynamics are solved separately by decoupling solution principle. The influence of aerodynamic force and moment, engine thrust and moment on hydrodynamic force and taxiing attitude is considered synthetically by the vertical approximate balance hypothesis and instantaneous pitch balance hypothesis. The discrete velocity piecewise solution is used to solve the takeoff process. The results show that the taxi resistance peak appeared in the range of 0.3~0.35 times of takeoff velocity, and the greater is the trim angle, the smaller are the hydrodynamic resistance and hydrodynamic moment when the unmanned seaplane taxiing at medium or high speed. What's more, compared with the fixed trim angle hypothesis, the combined trim angle method is more consistent with the actual takeoff process.

Nonlinear dynamic analysis of galloping of a single iced conductor with four degrees of freedom based on curved beam theory

Based on the nonlinear strain-displacement relationship of spatial curved beam theory, a finite element model for galloping analysis of iced transmission lines is established, which involves three translational degrees of freedom (DOF) and one rotational degree of freedom for each node. Considering the aerodynamic nonlinearity and the geometric nonlinearity of large amplitude motions of the iced transmission line, the nonlinear dynamic finite element equation is presented by using the virtual work principle. The equation is transformed into the sub-space according to the mode superposition method and a time integration algorithm is also performed in the sub-space. Then, the element independence and modal convergence are researched. Finally, the influence of aerodynamic forces on structural frequency is analyzed. The numerical results show that aerodynamic forces will greatly affect the torsional frequency of the transmission line, which accurately reflects the dynamic characteristics of transmission lines. Furthermore, the galloping calculation of the transmission line has reliable accuracy by using 4-DOF (per node) elements for the iced conductor. On the other hand, the model can predict the actual galloping response of the transmission line, which is convenient for the implementation of subsequent control design.

Analysis of contact force and uplift of pantograph–catenary system in overlap section based on numerical simulations and experimental tests

This paper examines the dynamic performance of the pantograph passing through an overlap section of the catenary system, using a China’s high speed railway with the 4-span overlap as an example. The pantograph and catenary system are simulated as a lumped mass model and finite element model, respectively. The model is verified according to EN50318:2018. The model is also assessed against an experimental study of the contact force and uplift of contact wire at 300 km/h. Then the contact force and uplift of contact wire at the speed of 150–350 km/h are calculated. The research shows that when the pantograph passes through the overlap, the maximum contact force increases beyond 14%, the standard deviation of the contact force increases by more than 26%, and the increase of the vertical displacement exceeds 38%, which becomes more apparent with the increase of speed. Under the influence of aerodynamic force, when the running speed increases from 150 to 350 km/h, the mean contact force in the knuckle-downstream and knuckle-upstream orientation increase by 59.49% and 97.85%, respectively. As a result, the contact force and vertical displacement increase greatly when passing through the overlap section, which could affect the current collection quality.

Analysis of collision dynamics of lifting the pantograph during vehicle operation

It is a practical engineering problem to lift the pantograph during train operation. In this paper, a pantograph-catenary (PAC) model is established, which can realize pantograph lifting during train operation. In this model, the contact model between contact piece and contact wire is established using the polygon contact model (PCM). The PAC collision test rig is established, and the simulation model at low speed is verified by comparing the contact force and vertical acceleration of contact piece obtained from simulation and test. The factors influencing the process of pantograph lifting are analyzed. The simulation results show that the position where the dropper and contact wire are connected is the most disadvantageous position for pantograph lifting. The maximum impact force increases with the increase of pantograph lifting speed, and the relationship between them is linear. In addition, if the influence of aerodynamic force is not considered, the running speed of vehicle will not affect the pantograph lifting process.

Rigid multibody dynamic modeling for a semi-submersible wind turbine

This paper presents a rigid multibody dynamic model for a Floating Offshore Wind Turbine, and its dynamic responses are simulated. This system consists of four important mechanical rigid parts, referred to as platform, tower, nacelle, and rotor. The platform is constrained by three cables connected to the seabed, known as the mooring system. Buoyancy and hydrodynamic forces are also applied to the platform. The semi-submersible platform is investigated as one of the latest proposed designs for the platform, which plays an important role in the stability and minimization of applied forces to the whole structure. Turbine’s rotor is modeled as a rigid disk rotating about its shaft axis and under the influence of aerodynamic force and torque. Therefore, the platform with six, and rotor with one Degree of Freedom in combination with the tower and nacelle, form a seven Degree of Freedom holonomic system. Euler–Lagrange equations are utilized to formulate the system’s equations of motion. In numerical simulation section, dynamic responses under four load cases are presented and validated against “Fatigue, Aerodynamics, Structures and Turbulence” module outputs under the same conditions. The effects of considering pontoons and cross braces on dynamic responses are also investigated. Moreover, the effect of the rotor’s gyroscopic moment is examined.

Clinical characterization of respiratory large droplet production during common airway procedures using high-speed imaging

During the COVID-19 pandemic, a significant number of healthcare workers have been infected with SARS-CoV-2. However, there remains little knowledge regarding large droplet dissemination during airway management procedures in real life settings. 12 different airway management procedures were investigated during routine clinical care. A high-speed video camera (1000 frames/second) was for imaging. Quantitative droplet characteristics as size, distance traveled, and velocity were computed. Droplets were detected in 8/12 procedures. The droplet trajectories could be divided into two distinctive patterns (type 1/2). Type 1 represented a ballistic trajectory with higher speed large droplets whereas type 2 represented a random trajectory of slower particles that persisted longer in air. The use of tracheal cannula filters reduced the amount of droplets. Respiratory droplet patterns generated during airway management procedures follow two distinctive trajectories based on the influence of aerodynamic forces. Speaking and coughing produce more droplets than non-invasive ventilation therapy confirming these behaviors as exposure risks. Even large droplets may exhibit patterns resembling the fluid dynamics smaller airborne aerosols that follow the airflow convectively and may place the healthcare provider at risk.

Control System Design and Evaluating Influence of Aerodynamic Force in Autonomous Flight System to Create Microgravity Space

Control System Design and Evaluating Influence of Aerodynamic Force in Autonomous Flight System to Create Microgravity Space

Numerical simulation of surface curvature effect on aerodynamic performance of different types of airfoils

The development of car modification using rear wings or spoilers, underlies the research on the aerodynamic performance of airfoil. The influence of aerodynamic forces will produce a down force to the bottom of the vehicle. The present paper investigate airfoil NACA 0012, NACA 4415, GOE 528 and GOE 652 to estimate the effectiveness of airfoil shape based on different angles of attack. The numerical simulation has been done using ANSYS Fluent to obtain drag coefficient, lift coefficient and lift-to-drag ratio of all cases. In addition, the drag and down forces have been calculated with respect to airfoil geometry features. The main objective in this paper is finding the effect of airfoil surface specification as a part of airfoil geometry features. The results observe that the highest lift coefficient value was achieved by GOE 652 which was equal to CL=1.9310 at 7 degree angle while the highest lift-to-drag ratio achieved by NACA 4415 which was equal to 100.8359. The highest down force was 1906.847 N at 15 degree by GOE 652 airfoil. The results show that the airfoil GOE 652 has the most effective surface area among the four airfoils.

Research on aerodynamic and flow field characteristics of high speed elevator with different shaft blockage ratio

With the increase of building height, more and more high-speed elevators are applied to high-rise buildings in order to improve the transportation efficiency of people in buildings. Compared with the medium and low speed elevators, the airflow in the shaft is more severe when the high-speed elevator car is running in the narrow and long shaft, and the influence of aerodynamic force and aerodynamic noise is more obvious. In order to explore the aerodynamic characteristics of the high-speed movement of the elevator car and the airflow law in the shaft, and further optimize the aerodynamic parameters of the high-speed elevator shaft system, a full-scale three-dimensional model of the shaft with different blocking ratio is established and numerically simulated. Through the analysis of the calculation results of different blockage ratio of the shaft model, it is found that the greater the blockage ratio is, the greater the resistance of the car operation is, and the airflow disturbance behind the car movement is more severe than that in the front. The calculation results provide a reference for further exploring the airflow flow law in the high-speed elevator shaft.

Comparative Evaluation of the Effect of Vehicle Parameters on Fuel Consumption under NEDC and WLTP

Higher speeds, faster acceleration and longer duration need a more realistic driving cycle. As a result, a new test procedure that reflects real-world driving conditions has been applied since 2017, and the previous development environment optimized for NEDC has also changed. In this study, several factors and technologies relating to fuel consumption, such as vehicle weight, tire rolling resistance, drag of aerodynamic, stop–start, and 48 V mild hybrid system, are evaluated as per the new worldwide harmonized light vehicles test procedure (WLTP) and compared with that of the previous European driving cycle (NEDC). The impact of the vehicle weight is increased in case of the WLTP due to faster acceleration compared to that under NEDC. The influence of aerodynamic force is very important as the average and maximum speed are increased. Meanwhile, the impact of idle stop–start technology is lower compared to that under NEDC due to the reduction in idle operation time. The 48-V mild hybrid system is still expected to play a role as a powerful fuel consumption reduction technology under new WLTP by applying energy regeneration, minor torque assist, and extended idle stop–start.

МАТЕМАТИЧЕСКОЕ ИССЛЕДОВАНИЕ СКОРОСТНОГО СКОЛЬЖЕНИЯ ФАЗ ПРИ ВЗАИМОДЕЙСТВИИ УДАРНОЙ ВОЛНЫ ПРЕДЕЛЬНО МАЛОЙ ИНТЕНСИВНОСТИ С ЭЛЕКТРИЧЕСКИ ЗАРЯЖЕННОЙ ГАЗОВЗВЕСЬЮ

The paper presents a mathematical model of an electrically charged suspension of particles, as well as numerical calculations related to the dynamics of the dispersed component of a mixture moving both under the influence of aerodynamic forces and under the influence of the Coulomb force. The author used a mathematical model of a nonequilibrium multiphase medium motion to describe the aerodynamics of suspensions. The mathematical model took into account the force interaction of the carrier and dispersed phases and interphase heat transfer, as well as the internal electric field generated by electrically charged solid particles. Using the software implementation of the mathematical model, a numerical study of the velocity slip of phases was carried out.

Study on Aerodynamic Characteristics of Super High Speed Elevator

With the increase of elevator running speed, the influence of aerodynamic force on elevator becomes more and more obvious, and the impact is also increasing gradually. In this paper, the Computational Fluid Dynamic numerical simulation method is used to simulate and analyse the aerodynamic characteristics of elevator car under the influence of different operating speed and distance from side of car to hoistway wall by establishing full-scale model of elevator and hoistway. The results show that when the car is in a symmetrical position, the aerodynamic characteristics on both sides always show obvious symmetry. With the decrease of distance from side of car to hoistway wall and the operating speed of the car, the flow field around the car changes intensified, and the aerodynamic forces on the side of the car will also increase significantly.

The Movement of a Mixture of Cotton with an Air Stream during Pneumatic Transport by Pipeline of Variable Cross Section

The article considers the movement of a mixture of air and raw cotton through a pipeline with a variable cross-section as a multi-speed heterogeneous medium. The regularities of the movement of components inside the pipeline, the equation of change in the porosity of cotton, air pressure and component velocities in time and along the transportation line are obtained. It was found that in the initial 20 - 25 m part of the pneumatic transport pipe there is a sharp decrease in pressure and air flow velocity, while the speed of cotton increases rapidly due to which there is a strong deformation of cotton stretching under the influence of aerodynamic force, which occurs due to the difference in the velocities of the components of the mixture, as a result of which the cotton loosens, and its porosity increases intensively.

English

English

Research on Influence of Aerodynamic Force on the Aerodynamic Heat for the Hypersonic Vehicle

During the flight of the hypersonic Vehicle, the angle of attack will change with the flight attitude. At the same time, the aerodynamic forces from the surface of aircraft will also be changing. The pressure and friction force are the main causes of the aerodynamic heating, so the surface aerodynamic heating will change. By used the method of numerical calculation, the passage studied the influence the change the pressure and friction force on the distribution of heat flux in different angle of attack and the relationship between the change of the force of lift-drag and aerodynamic heating. The research suggested that the distribution of the heat flux had very good consistency with that of pressure and friction. The lift change was the dominant factors influence of pneumatic thermal change; the change of drag force affected only the speed of heat flux change.

The aerodynamics of jumping rope

We consider the influence of aerodynamic forces on the shape of a whirling filament that is held at both ends, i.e. a jump rope. At high Reynolds numbers, the rope curls out of the plane and towards the axis of rotation—a feature we demonstrate via experiment. We derive a pair of coupled nonlinear differential equations that characterize the steady-state shape of the rope, and the resulting eigenvalue problem is solved numerically. The solution depends on two dimensionless groups: the ratio between the length of the rope and the distance between its ends, and the relative magnitude of the aerodynamic to centrifugal forces. As the latter ratio is progressively increased, the tension in the rope and the out-of-plane deflection increases, until eventually the rope reaches a limiting shape. Finally, we show that the airflow-induced shape change leads to a relative reduction in drag and has implications for successful skipping.

Study of Wake Characteristics of a Horizontal-Axis Wind Turbine within Two-Phase Flow

The two-phase flow is addressed for the more accurate estimation of the wake characteristic for the horizontal-axis wind turbine operating in the complexly unsteady environmental states. The computational fluid dynamics (CFD) method is implemented for performing the three-dimensional wind turbine using the simulating software tool of FLUNT. Three types of environmental states, single-phase flow, liquid-gas flow and solid-gas flow, are performed for the comparison of velocity and pressure distribution to derive the specify feature for wind turbine within two-phase flow environmental state. The calculated results shows that there has the similar evolutional tendency of velocity distribution for both single- and two-phase flows and the velocity decrement at the distance of 20 meter away from wind turbine still reach to 80% of inflow speed. But the turbine blade within two-phase flow is subject to the unsteady flow with the larger velocity gradient compared with that within single-phase flow. For the static pressure, large difference occurred in these three types of environmental state reveals that the second material in addition to atmospheres causes the prominent influence of aerodynamic force and its power coefficient. The results exhibit that wind turbine within solid-gas flow has the largest power coefficient that those within the gas and liquid-gas flows.

Influence of aerodynamic forces in ice shedding

Stresses in accreted ice on a typical airfoil impact ice caused by aerodynamic forces have been studied using finite element analyses. The objective of this study is to determine the significance of these stresses relative to values needed to cause ice shedding. In the case studied, stresses are not significant (less than 10 percent) when compared to the fracture value for airspeeds below a Mach number of 0.45. Above this velocity, the influence of aerodynamic forces on impact ice stresses should be considered in analyses of ice shedding.

Electrical characterization of bell-type electrostatic painting systems

A numerical model that determines the electrical characteristics of a bell-type electrostatic painting system is presented. The model is capable of handling the complex geometries of practical sprayers and accounts for the space charge effect of charged paint droplets. The influence of aerodynamic forces is also considered in tracing individual droplet trajectories. As a test of tile simulation, the restricted case of a sprayer emitting ions, rather than charged paint droplets, was modeled. The simulation results were compared with experimental data and showed good agreement. For the more general case, maps of equipotential contours and the paint droplet trajectories are generated for a bell-type sprayer. It was found that the space charge tends to increase the deposition field, although not as strongly as increased bell potential or decreased bell-to-target spacing. However, the space charge also caused the spray pattern to expand, possibly leading to increased overspray. >