scholarly journals Aerodynamic Characteristics Analysis and External Trajectory Simulation of High-speed Cross-media Water Entry Projectile

2021 ◽  
Vol 2079 (1) ◽  
pp. 012023
Author(s):  
Xu-Tuo Ding ◽  
Shi-Ji Li ◽  
Song-Jiang Peng ◽  
Jin Wei
Keyword(s):  
High Speed ◽  
Initial Conditions ◽  
Aerodynamic Characteristics ◽  
Static Stability ◽  
Water Entry ◽  
Aerodynamic Coefficients ◽  
Cross Media ◽  
Characteristics Analysis ◽  
The Stability ◽  
Trajectory Equation

Abstract The aerodynamic characteristics of a water entry projectile is studied. The aerodynamic coefficients at different Mach numbers and different attack angles are given through CFD numerical simulation, and the stability analysis is carried out. The results show that the projectile with the current shape meets the static stability requirements. Based on the aerodynamic coefficients obtained, the projectile flight trajectory equation is established to obtain the trajectory at different emissive angles. Finally, the trajectory parameters with the range of 5 km were used as the initial conditions for the simulation of high-speed water entry projectile, and the process of projectile entry with small angle was simulated. The simulation results show that the projectile sails smoothly when entering the water, the trajectory is straight, there is no ricochet phenomenon, which has a good water entry stability.

scholarly journals Aerodynamics of inclined cylindrical bodies free-flying in a hypersonic flowfield

2021 ◽  
Vol 62 (9) ◽  
Author(s):  
Patrick M. Seltner ◽  
Sebastian Willems ◽  
Ali Gülhan ◽  
Eric C. Stern ◽  
Joseph M. Brock ◽  
...  
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Numerical Data ◽  
Static Stability ◽  
Free Flight ◽  
Aerodynamic Coefficients ◽  
Flow Topology ◽  
Motion Data ◽  
Continuous Rotation ◽  
German Aerospace

Abstract The influence of the flight attitude on aerodynamic coefficients and static stability of cylindrical bodies in hypersonic flows is of interest in understanding the re/entry of space debris, meteoroid fragments, launch-vehicle stages and other rotating objects. Experiments were therefore carried out in the hypersonic wind tunnel H2K at the German Aerospace Center (DLR) in Cologne. A free-flight technique was employed in H2K, which enables a continuous rotation of the cylinder without any sting interferences in a broad angular range from 0$$^{\circ }$$ ∘ to 90$$^{\circ }$$ ∘ . A high-speed stereo-tracking technique measured the model motion during free-flight and high-speed schlieren provided documentation of the flow topology. Aerodynamic coefficients were determined in careful post-processing, based on the measured 6-degrees-of-freedom (6DoF) motion data. Numerical simulations by NASA’s flow solvers Cart3D and US3D were performed for comparison purposes. As a result, the experimental and numerical data show a good agreement. The inclination of the cylinder strongly effects both the flowfield and aerodynamic loads. Experiments and simulations with concave cylinders showed marked difference in aerodynamic behavior due to the presence of a shock–shock interaction (SSI) near the middle of the model. Graphic abstract

Aerodynamic Characteristics Analysis of High-Speed Train on Cutting under Crosswinds

2013 ◽  
Vol 300-301 ◽  
pp. 62-67
Author(s):  
Kun Ye ◽  
Ren Xian Li
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
High Speed Train ◽  
Aerodynamic Forces ◽  
Cutting Depth ◽  
Cutting Slope ◽  
Characteristics Analysis ◽  
Relationship Of ◽  
The Relationship

Cutting is an effective device to reduce crosswind loads acting on trains. The cutting depth, width and gradient of slope are important factors for design and construction of cutting. Based on numerical analysis methods of three-dimensional viscous incompressible aerodynamics equations, aerodynamic side forces and yawing moments acting on the high-speed train, with different depths and widths of cutting，are calculated and analyzed under crosswinds，meanwhile the relationship of the gradient of cutting slope and transverse aerodynamic forces acting on trains are also studied. Simulation results show that aerodynamic side forces and yawing moments acting on the train（the first, middle and rear train）decrease with the increase of cutting depth. The relationship between transverse forces (moments) coefficients acting on the three sections and the cutting depth basically is the three cubed relation. The bigger is cutting width，the worse is running stability of train. The relationship between yawing moments coefficients acting each body of the train and the cutting width approximately is the three cubed relation. The transverse Aerodynamic forces decreased gradually with the increase of the gradient of cutting slope, the relationship between yawing moments coefficients acting each body of the train and the gradient of cutting slope basically is the four cubed relation.

Loss Characteristics Analysis and Optimization of an Off-Axis Rotary Optical Fiber Communication System

2014 ◽  
Vol 596 ◽  
pp. 788-793 ◽  
Author(s):  
Xiao Hua Wang ◽  
Qian Zhao ◽  
Li Li ◽  
Jie Ding ◽  
Qiu Xin Zheng ◽  
...  
Keyword(s):  
Optical Fiber ◽  
Communication System ◽  
High Speed ◽  
Optical Fiber Communication ◽  
Fiber Communication ◽  
Experiment Platform ◽  
Optical Fiber Communication System ◽  
Characteristics Analysis ◽  
Fiber Collimator ◽  
The Stability

The losses of the off-axis rotary optical fiber communication system were derived from optical fiber coupling, three kinds of misalignments between optical fiber collimators (Axial separation Z0, lateral offset X0, angular tilting θ), incomplete alignment of optical fiber collimator during rotation and system tremble caused by high speed rotating. Some measures were taken to reduce the loss. The thermally expanded core fiber collimator cut down the influence of axial separation and angular tilting. The position of the optical fiber collimator on the flange was adjusted and infrared right angle prisms were installed to reduce the losses during rotation of the system. In addition, improving the precision and optimizing device of mechanical structure can increase the stability of the whole experiment platform and decrease the losses.

scholarly journals Methodology for calculating the efficiency of the rudders of the tandem aircraft

2021 ◽  
pp. 11-21
Author(s):  
Illya Bilous ◽  
Illya Kryvohatko ◽  
Yurii Yakovlev
Keyword(s):  
Wind Tunnel ◽  
Rapid Development ◽  
Aerodynamic Characteristics ◽  
Wind Tunnel Experiment ◽  
Wind Tunnels ◽  
Analysis Tool ◽  
It Impacts ◽  
Characteristics Analysis ◽  
The Stability

As of recent rapid development in the field of UAVs, unusual aerodynamic practices can be used, for example, the tandem scheme. In early planning stages, it’s important to evaluate aerodynamic characteristics of the chosen scheme and to approximate its balancing losses, as it impacts the stability and controllability of the craft. The most effective way of aerodynamic characteristics analysis is done using wind tunnels. However, it requires considerable investments in both financial terms and time, when designing the model, conducting the experiment and processing the results. Because of that, it’s worthwhile to consider the simple CFD calculations (XFOIL). This paper calculates aerodynamic characteristics of a tandem-scheme based “A-8” aircraft using XFLR5 analysis tool with the results compared to a real wind tunnel experiment. The overall conclusion of the paper is a recommendation to consider XFLR5 for early planning stages for advanced balancing losses calculation approximation.

scholarly journals ОСОБЛИВОСТІ ЗАБЕЗПЕЧЕННЯ АЕРОДИНАМІЧНИХ ХАРАКТЕРИСТИК РЕГІОНАЛЬНОГО ПАСАЖИРСЬКОГО ЛІТАКА

2019 ◽  
pp. 106-133
Author(s):  
Олександр Дмитрович Донець ◽  
Володимир Олександрович Кудрявцев
Keyword(s):  
High Speed ◽  
Research Work ◽  
Flight Dynamics ◽  
Aerodynamic Characteristics ◽  
Static Stability ◽  
Control Mode ◽  
Aviation Industry ◽  
Maximum Speed ◽  
Flight Tests ◽  
Aerodynamic Configuration

Principal results of the computational and research work performed during development of a regional passenger aircraft to ensure its aerodynamic characteristics are given. When creating the An-148-100/An-158 family of aircraft, such level of the aircraft aerodynamic perfection was achieved, which ensured fulfillment of the specified requirements for their flight performance – maximum speed, cruising flight altitude and flight range with different payloads. The developed aerodynamic configuration made it possible to create a family of regional passenger high-wing planes with a flight speed of up to 870 km/h (true speed) (M = 0.8), which have no analogues in the world aviation industry. Developed for the An-148-100 / An- 158 aircraft, supercritical profiles of the new generation with a large maximum relative thickness formed the basis of the aerodynamic configuration of a high-speed  wing with moderate sweep. The aircraft lift-to-drag ratio in cruise flight is Kcruise = 15.8, which corresponds to the worldwide values. Developed aerodynamic configuration of the wing high-lift devices provides high bearing properties of the wing during take-off and landing stages, which allows to fully meet the requirements for the runway required length of the base airfields Lrun = 1485...1950 m. Developed algorithms are implemented in the electric remote control system and provide necessary standard characteristics of stability, controllability and flight dynamics in the main control mode. Selected margins of the aircraft’s own static stability and effectiveness of its controls ensure safe completion of the flight in standby control mode. The certification flight tests of the An-148-100/An-158 airplanes confirmed full compliance of their take-off and landing performance, as well as the stability, controllability and flight dynamics characteristics with the requirements of the Certification basis in both standard and in failure situations tested in flight tests. Necessary and sufficient amount of experimental work was conducted in the lowspeed  and high-speed wind tunnels of the ANTONOV SC and TsAGI to verify the aerodynamic and spin characteristics of the An-148-100/An-158 airplane models, which improved the aerodynamic configuration of the aircraft and its individual units and allowed to apply the work results in calculation of aircraft strength, as well as for development of their systems.

scholarly journals Numerical Investigations on the Water Entry of Cylindrical Projectiles with Different Initial Conditions

2019 ◽  
Vol 9 (9) ◽  
pp. 1858 ◽  
Author(s):  
Jianguo Gao ◽  
Zhihua Chen ◽  
Wei-Tao Wu ◽  
Xin Li
Keyword(s):  
High Speed ◽  
Gas Flow ◽  
Stokes Equations ◽  
Initial Conditions ◽  
Water Entry ◽  
Navier Stokes ◽  
Multiphase Model ◽  
Entry Angle ◽  
Vibration Period ◽  
Small Water

In this paper, coupled with Reynolds-averaged Navier–Stokes equations and ballistic equations, the numerical simulations of high-speed water entry of projectiles under different conditions have been conducted. The water-gas flow was modeled by the mixture multiphase model. The numerical results indicated that the simulations agree well with analytical solutions by two cavity models, which validates the model applied. Then the effects of variations of project length, entry angle and velocity on the entry process of projectiles were further investigated. The results show that, for small water entry angles, the cavity wall interacts with the projectile, affects the trajectory of the projectile, and even ricochets for projectiles with small length (5D). On the other hand, the projectile vibrates during the whole process of water entry; the vibration amplitude decreases with the increase of projectile length and entry angle; however, it is the contrary for the vibration period. Furthermore, after the initial impact period, the influence of these parameters on the drag coefficient is not obvious.

scholarly journals Motion Characteristics After Ricochet: An Experimental Investigation

2020 ◽  
Vol 27 (2) ◽  
pp. 4-10
Author(s):  
Guoming Chen ◽  
Junhua Hu ◽  
An Liu ◽  
Jinfu Feng ◽  
Qingqing Hu
Keyword(s):  
High Speed ◽  
Initial Conditions ◽  
Incident Angle ◽  
Linear Functions ◽  
Small Scale ◽  
Residual Velocity ◽  
Angle Change ◽  
Motion Characteristics ◽  
The Stability ◽  
The Relationship

AbstractThe ricochet behaviour of the air–water trans-media vehicle (AWTMV) during water-entry crossing was experimentally investigated. Three types of small-scale AWTMV including cone, ogive, and flat nose were used in the test. The underwater trajectory, velocity, and inclination angle of projectiles during the ricochet process were obtained using a high-speed camera. The angle change of the AWTMV and the ratio of the residual velocity are introduced. Based on this result, the relationship between the ricochet responses and initial conditions was derived. The results of this study show that (1) a small incident angle and great velocity make the occurrence of ricochet behaviour easier, (2) the stability of the trajectory of projectiles with cone, ogive, and flat nose weakened in turn at the same initial conditions, (3) the angle change and the ratio of the residual velocity are linear functions of the incident angle and velocity.

STATIC STABILITY OF AERODYNAMICALLY SUPPORTED PLATFORMS MOVING ABOVE WATER

2021 ◽  
Vol 153 (A3) ◽  
Author(s):  
K I Matveev
Keyword(s):  
High Speed ◽  
Stability Margin ◽  
Ground Effect ◽  
Aerodynamic Characteristics ◽  
Static Stability ◽  
Underlying Surface ◽  
Geometrical Parameters ◽  
Marine Vehicles ◽  
Effect Theory ◽  
Rigid Plane

The motion stability is the most important problem of high-speed marine vehicles that utilize aerodynamic support. A simplified analysis and calculations of longitudinal static stability of several basic platforms moving above water are carried out in this study. The analysis is based on the extreme ground effect theory and the assumption of hydrostatic deformations of the water surface. Effects of the underlying surface type, Froude number, and several geometrical parameters on main aerodynamic characteristics, including the static stability margin, are presented. If the underlying surface is water instead of a rigid plane, the static stability worsens for platforms with flat or S-shaped lower surfaces, but it slightly improves for a horizontal platform with a flap. The static stability margin remains positive for S-shaped profiles at sufficiently low Froude numbers, while it is negative for other configurations.

Aerodynamic Characteristics Analysis of Ultra-High-Speed Elevator with Different Hoistway Structures

2021 ◽  
Author(s):  
Hao Jing ◽  
Qing Zhang ◽  
Ruijun Zhang ◽  
Qin He
Keyword(s):  
High Speed ◽  
Aerodynamic Force ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
Sudden Increase ◽  
Aerodynamic Forces ◽  
Cross Sectional ◽  
Ultra High Speed ◽  
Characteristics Analysis ◽  
Ventilation Hole

The high-speed airflow generated by ultra-high-speed elevators causes significant aerodynamic force, which seriously reduces the comfort and safety of passengers. First, a multi-parameter general model of ultra-high-speed elevator was established, and the three-dimensional numerical simulation of incompressible flow in the ultra-high-speed elevator was simulated. The correctness of the model and method was verified by experiments and grid-independence analyses. On this basis, the variation in the aerodynamic forces and the pressure in the hoistway was analyzed. Finally, the influence of different hoistway structures and parameters of ventilation holes on the aerodynamic forces and hoistway pressure were analyzed. The results showed that the opening of ventilation holes significantly reduced the aerodynamic forces and hoistway pressure for most of the period of the car’s operation period, but both the aerodynamic forces and hoistway pressure showed a sudden increase–decrease process. The aerodynamic forces and hoistway pressure were highly sensitive to changes in the hoistway blockage ratio, the cross-sectional area of the ventilation hole, and the position of the ventilation hole. When a pair of ventilation holes were opened, those in the middle of the hoistway reduced aerodynamic problems in the hoistway to the greatest extent. The increase in the connection angle between the ventilation hole and the hoistway eliminated the low-speed recirculation zone at the ventilation hole and increased the total volume of exhaust air at the ventilation hole.

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