Prediction of Yawing Moment for a Hand-Launched UAV Considering Interference Effect of Propeller Wake

In this paper, three-dimensional unsteady computational fluid dynamic(CFD) analyses based on overset grid technique have been performed for a hand-launched unmanned aerial vehicle(UAV) considering the wake effect generated by a rotating propeller. In addition, the defection of rudder is considered in order to consider to predict the equilibrium condition of yawing moment during cruise flight conditions. It is importantly shown in this paper that the wake interference effect of the propeller is significant to accurately predict the yawing moment of the UAV and the yawing moment coefficient corresponding to a flight speed can be different because of its different amount of wake effect due to the different rotating speed of the propeller.

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Improving a one-dimensional centrifugal compressor performance prediction method

Proceedings of the Institution of Mechanical Engineers Part A Journal of Power and Energy ◽

10.1243/095765005x31351 ◽

2005 ◽

Vol 219 (8) ◽

pp. 653-659 ◽

Cited By ~ 16

Author(s):

E Swain

Keyword(s):

Centrifugal Compressor ◽

Performance Prediction ◽

Fluid Dynamic ◽

Three Dimensional ◽

Axial Compressor ◽

Prediction Method ◽

Compressor Cascade ◽

One Dimensional ◽

Compressor Performance ◽

Cfd Analyses

A one-dimensional centrifugal compressor performance prediction technique that has been available for some time is updated as a result of extracting the component performance from three-dimensional computational fluid dynamic (CFD) analyses. Confidence in the CFD results is provided by comparison of overall performance for one of the compressor examples. The extracted impeller characteristic is compared with the original impeller loss model, and this indicated that some improvement was desirable. The position of least impeller loss was determined using a traditional axial compressor cascade method, and suitable algebraic expressions were derived to match the CFD data. The merit of the approach lies with the relative ease that CFD component performance currently can be achieved and adjusting one-dimensional methods to agree with the CFD-derived models.

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Vibration characteristics of triple-gear-rotor system in compressed air energy storage under variable torque load

Science Progress ◽

10.1177/0036850420987058 ◽

2021 ◽

Vol 104 (1) ◽

pp. 003685042098705

Author(s):

Xinran Wang ◽

Yangli Zhu ◽

Wen Li ◽

Dongxu Hu ◽

Xuehui Zhang ◽

...

Keyword(s):

Large Scale ◽

Three Dimensional ◽

Element Model ◽

Rotor System ◽

Dynamic Responses ◽

System Response ◽

Rotating Speed ◽

Torque Load ◽

Set Up ◽

Two Stages

This paper focuses on the effects of the off-design operation of CAES on the dynamic characteristics of the triple-gear-rotor system. A finite element model of the system is set up with unbalanced excitations, torque load excitations, and backlash which lead to variations of tooth contact status. An experiment is carried out to verify the accuracy of the mathematical model. The results show that when the system is subjected to large-scale torque load lifting at a high rotating speed, it has two stages of relatively strong periodicity when the torque load is light, and of chaotic when the torque load is heavy, with the transition between the two states being relatively quick and violent. The analysis of the three-dimensional acceleration spectrum and the meshing force shows that the variation in the meshing state and the fluctuation of the meshing force is the basic reasons for the variation in the system response with the torque load. In addition, the three rotors in the triple-gear-rotor system studied show a strong similarity in the meshing states and meshing force fluctuations, which result in the similarity in the dynamic responses of the three rotors.

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Coupled Fluid–Solid Numerical Simulation for Flow Field Characteristics and Supporting Performance of Flexible Support Cylindrical Gas Film Seal

Aerospace ◽

10.3390/aerospace8040097 ◽

2021 ◽

Vol 8 (4) ◽

pp. 97

Author(s):

Junfeng Sun ◽

Meihong Liu ◽

Zhen Xu ◽

Taohong Liao ◽

Xiangping Hu ◽

...

Keyword(s):

Flow Field ◽

Film Thickness ◽

Fluid Dynamic ◽

Structural Characteristics ◽

Structural Parameters ◽

Equivalent Stress ◽

Three Dimensional ◽

High Rotational Speed ◽

Flexible Support ◽

Flow Field Characteristics

A new type of cylindrical gas film seal (CGFS) with a flexible support is proposed according to the working characteristics of the fluid dynamic seal in high-rotational-speed fluid machinery, such as aero-engines and centrifuges. Compared with the CGFS without a flexible support, the CGFS with flexible support presents stronger radial floating characteristics since it absorbs vibration and reduces thermal deformation of the rotor system. Combined with the structural characteristics of a film seal, an analytical model of CGFS with a flexible wave foil is established. Based on the fluid-structure coupling analysis method, the three-dimensional flow field of a straight-groove CGFS model is simulated to study the effects of operating and structural parameters on the steady-state characteristics and the effects of gas film thickness, eccentricity, and the number of wave foils on the equivalent stress of the flexible support. Simulation results show that the film stiffness increases significantly when the depth of groove increases. When the gas film thickness increases, the average equivalent stress of the flexible support first decreases and then stabilizes. Furthermore, the number of wave foils affects the average foils thickness. Therefore, when selecting the number of wave foils, the support stiffness and buffer capacity should be considered simultaneously.

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A Fast Two-Dimensional Numerical Method for the Wake Simulation of a Vertical Axis Wind Turbine

Energies ◽

10.3390/en14010049 ◽

2020 ◽

Vol 14 (1) ◽

pp. 49

Author(s):

Zheng Yuan ◽

Jin Jiang ◽

Jun Zang ◽

Qihu Sheng ◽

Ke Sun ◽

...

Keyword(s):

Velocity Distribution ◽

Numerical Method ◽

Three Dimensional ◽

Particle Method ◽

Vortex Method ◽

Vertical Axis ◽

Two Dimensional ◽

Vertical Axis Wind Turbine ◽

Wake Effect ◽

Array Design

In the array design of the vertical axis wind turbines (VAWT), the wake effect of the upstream VAWT on the downstream VAWT needs to be considered. In order to simulate the velocity distribution of a VAWT wake rapidly, a new two-dimensional numerical method is proposed, which can make the array design easier and faster. In this new approach, the finite vortex method and vortex particle method are combined to simulate the generation and evolution of the vortex, respectively, the fast multipole method (FMM) is used to accelerate the calculation. Based on a characteristic of the VAWT wake, that is, the velocity distribution can be fitted into a power-law function, a new correction model is introduced to correct the three-dimensional effect of the VAWT wake. Finally, the simulation results can be approximated to the published experimental results in the first-order. As a new numerical method to simulate the complex VAWT wake, this paper proves the feasibility of the method and makes a preliminary validation. This method is not used to simulate the complex three-dimensional turbulent evolution but to simulate the velocity distribution quickly and relatively accurately, which meets the requirement for rapid simulation in the preliminary array design.

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The inlet flow structure of a conceptual open-nose supersonic drone

Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering ◽

10.1177/0954410020983043 ◽

2021 ◽

pp. 095441002098304

Author(s):

Eiman B Saheby ◽

Xing Shen ◽

Anthony P Hays ◽

Zhang Jun

Keyword(s):

Flow Structure ◽

Stokes Equations ◽

Fluid Dynamic ◽

Three Dimensional ◽

Computational Fluid Dynamic Simulation ◽

Navier Stokes ◽

Ansys Fluent ◽

Navier Stokes Equations ◽

Aerodynamic Efficiency ◽

Performance Effects

This study describes the aerodynamic efficiency of a forebody–inlet configuration and computational investigation of a drone system, capable of sustainable supersonic cruising at Mach 1.60. Because the whole drone configuration is formed around the induction system and the design is highly interrelated to the flow structure of forebody and inlet efficiency, analysis of this section and understanding its flow pattern is necessary before any progress in design phases. The compression surface is designed analytically using oblique shock patterns, which results in a low drag forebody. To study the concept, two inlet–forebody geometries are considered for Computational Fluid Dynamic simulation using ANSYS Fluent code. The supersonic and subsonic performance, effects of angle of attack, sideslip, and duct geometries on the propulsive efficiency of the concept are studied by solving the three-dimensional Navier–Stokes equations in structured cell domains. Comparing the results with the available data from other sources indicates that the aerodynamic efficiency of the concept is acceptable at supersonic and transonic regimes.

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Collaborative Pursuit-Evasion Strategy of UAV/UGV Heterogeneous System in Complex Three-Dimensional Polygonal Environment

Complexity ◽

10.1155/2020/7498740 ◽

2020 ◽

Vol 2020 ◽

pp. 1-13

Author(s):

Xiao Liang ◽

Honglun Wang ◽

Haitao Luo

Keyword(s):

Visual Field ◽

Heterogeneous System ◽

Three Dimensional ◽

Unmanned Ground Vehicle ◽

Worst Case ◽

Ground Vehicle ◽

Pursuit Evasion ◽

Evasion Game ◽

Evasion Strategy ◽

Aerial Vehicle

The UAV/UGV heterogeneous system combines the air superiority of UAV (unmanned aerial vehicle) and the ground superiority of UGV (unmanned ground vehicle). The system can complete a series of complex tasks and one of them is pursuit-evasion decision, so a collaborative strategy of UAV/UGV heterogeneous system is proposed to derive a pursuit-evasion game in complex three-dimensional (3D) polygonal environment, which is large enough but with boundary. Firstly, the system and task hypothesis are introduced. Then, an improved boundary value problem (BVP) is used to unify the terrain data of decision and path planning. Under the condition that the evader knows the position of collaborative pursuers at any time but pursuers just have a line-of-sight view, a worst case is analyzed and the strategy between the evader and pursuers is studied. According to the state of evader, the strategy of collaborative pursuers is discussed in three situations: evader is in the visual field of pursuers, evader just disappears from the visual field of pursuers, and the position of evader is completely unknown to pursuers. The simulation results show that the strategy does not guarantee that the pursuers will win the game in complex 3D polygonal environment, but it is optimal in the worst case.

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Fish larvae exploit edge vortices along their dorsal and ventral fin folds to propel themselves

Journal of The Royal Society Interface ◽

10.1098/rsif.2016.0068 ◽

2016 ◽

Vol 13 (116) ◽

pp. 20160068 ◽

Cited By ~ 16

Author(s):

Gen Li ◽

Ulrike K. Müller ◽

Johan L. van Leeuwen ◽

Hao Liu

Keyword(s):

Larval Fish ◽

Fish Larvae ◽

Fluid Dynamic ◽

Three Dimensional ◽

Reynolds Numbers ◽

Bony Fish ◽

The Body ◽

Functional Explanation ◽

Image Velocimetry ◽

Median Fins

Larvae of bony fish swim in the intermediate Reynolds number ( Re ) regime, using body- and caudal-fin undulation to propel themselves. They share a median fin fold that transforms into separate median fins as they grow into juveniles. The fin fold was suggested to be an adaption for locomotion in the intermediate Reynolds regime, but its fluid-dynamic role is still enigmatic. Using three-dimensional fluid-dynamic computations, we quantified the swimming trajectory from body-shape changes during cyclic swimming of larval fish. We predicted unsteady vortices around the upper and lower edges of the fin fold, and identified similar vortices around real larvae with particle image velocimetry. We show that thrust contributions on the body peak adjacent to the upper and lower edges of the fin fold where large left–right pressure differences occur in concert with the periodical generation and shedding of edge vortices. The fin fold enhances effective flow separation and drag-based thrust. Along the body, net thrust is generated in multiple zones posterior to the centre of mass. Counterfactual simulations exploring the effect of having a fin fold across a range of Reynolds numbers show that the fin fold helps larvae achieve high swimming speeds, yet requires high power. We conclude that propulsion in larval fish partly relies on unsteady high-intensity vortices along the upper and lower edges of the fin fold, providing a functional explanation for the omnipresence of the fin fold in bony-fish larvae.

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