Abstract ：

This study investigates surface erosion wear caused by collision and friction between propellers and sand particles during the flight of propeller transport aircraft in harsh environments like deserts and plateaus, which are characterized by strong sand and wind conditions. Firstly, the erosion behavior of individual propeller blades is analyzed under various sand particle parameters using the commercial software FLUENT. Subsequently, dynamic simulations of the entire blade are conducted by the sliding mesh method to examine erosion patterns under different operational conditions, including rotation speed and climb angle. Finally, the impact of erosion on the aerodynamic characteristics of the propeller is obtained based on simulation results. This study delves into the erosion patterns observed in large aircraft propellers operating within sandy and dusty environments, as well as the consequential impact of propeller surface wear on aerodynamic performance. By elucidating these phenomena, this research provides valuable insights that can inform future endeavors aimed at optimizing propeller design.

Keyword ：

Erosive wear behavior Aircraft propellers Aerodynamic characteristics

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Abstract ：

The new functionally grated graphene platelets (FG-GP) reinforced rotating pre-twisted composite laminated blade may exhibit strong nonlinear vibrations under combined the transverse aerodynamic force and axial excitation. These nonlinear vibrations are major contributors to the overall failure of the rotating pre-twisted composite laminated blade. In this paper, the resonant responses, threshold surface, global bifurcations and double-parameter multi-pulse chaotic dynamics of the rotating pre-twisted composite laminated blade are investigated on the basis of the nonlinear dynamic model of the new FG-GP reinforced rotating pre-twisted composite laminated blade for the first time. Considering the primary parametric and 1:1 internal resonances, the averaged equations for the new FG-GP reinforced rotating pre-twisted composite laminated blade are derived by using the multiple scale perturbation (MSP) method. The amplitude-frequency and force-amplitude response curves are obtained to analyze the resonant responses of the new FG-GP reinforced rotating pre-twisted composite laminated blade. The extended Melnikov method is used to explore the threshold surface, global bifurcations and double-parameter multi-pulse chaotic dynamics of the new FG-GP reinforced rotating pre-twisted composite laminated blade under combined the transverse aerodynamic force and axial excitation. Through the theoretical analysis and numerical simulation, it is discovered that the new FG-GP reinforced rotating pre-twisted composite laminated blade exhibits the hard spring characteristics. The energy transfers between two-order modes are proved by the occurrence of the bubble response shape. The complex double-parameter multi-pulse chaotic vibrations are investigated for the new FG-GP reinforced rotating pre-twisted composite laminated blade under the influence of different parameters. These results have the significant theoretical guidance for the optimized design of the new FG-GP reinforced rotating pre-twisted composite laminated blade.

Keyword ：

Graphene reinforcement Resonant responses The extended Melnikov method Rotating pre-twisted plate Threshold surface Double-parameter multi-pulse chaotic vibra- tions

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Abstract ：

This paper analyzes the nonlinear dynamic behaviors of the graphene-reinforced aluminum-based aero-engine blade under the primary resonance using the amplitude-frequency response curves, bifurcation diagram, Lyapunov exponent and Poincare ' map. The lateral aerodynamic load, longitudinal aerodynamic load, centrifugal force and temperature are investigated for the graphene-reinforced aluminum-based aero-engine blade. Three kinds of configurations for the functionally graphene-reinforced gradient are considered. The effective Young's modulus of the composite material is given by Halpin-Tsai mode. The rule of the mixture gives other material properties. The results demonstrate that the bifurcation diagrams of the modal amplitude for the blade with the lateral aerodynamic load, longitudinal aerodynamic load and temperature have the periodic-chaos dynamic evolution process under the disturbance of the engine rotation speed. When the disturbance amplitude reaches a specific value, a new round of the periodic-chaos dynamic evolution will be continued. The results also clearly indicate that the aero-engine blade has the rich and complex nonlinear dynamic behaviors which include the hyperchaos, chaos, almost periodic, typical period-doubling bifurcation and anti-period-doubling bifurcation vibrations. This research is more helpful for the engineers to understand the nonlinear dynamic behavior of the blade.

Keyword ：

Bifurcation diagram Nonlinear dynamics Graphene-reinforced Temperature dependence Poincare ' map Halpin-Tsai model

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A 5-MW wind turbine has been modeled and analyzed for fluid-structure interaction and aerodynamic performance. In this study, a full-scale model of a 5-MW wind turbine is first developed based on a computational fluid dynamics (CFD) approach, in which the unsteady, noncompressible Reynolds Averaged Navier-Stokes (RANS) method is used. The main focus of the study is to analyze the tower shadow effect on the aerodynamic performance of the wind turbine under different inlet flow conditions. Subsequently, the finite element model is established by considering fluid/structure interactions to study the structural stress, displacement, strain distributions and flow field information of the structure under the uniform wind speed. Finally, the fluid-structure interaction model is established by considering turbulent wind and the tower shadow effect. The variation rules of the dynamic response of the one-way and two-way fluid-structure interaction (FSI) models under different wind speeds are analyzed, and the numerical calculation results are compared with those of the centralized mass model. The results show that the tower shadow effect and structural deformation are the main factors affecting the aerodynamic load fluctuation of the wind turbine, which in turn affects the aerodynamic performance and structural stability of the blades. The structural dynamic response of the coupled model shows significant similarity, while the structural displacement response of the former exhibits less fluctuation compared with the conventional centralized mass model. The one-way fluid-structure interaction (FSI) model shows a higher frequency of stress-strain and displacement oscillations on the blade compared with the two-way FSI model.

Keyword ：

computational fluid dynamics methods (CFD) tower shadow effect aerodynamic performance fluid-structure interaction space flow field

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Because of the aerodynamic drag force, satellites formation with different area-mass-ratio will diverge during the life time in orbit. To maintain the configuration of the formation, this paper proposed a control strategy with high engineering practicability and fuel economy. By reversely calculating the rate of orbit decay from the time interval between formation maintenance control and the distance variation between satellites, the velocity increment of a unilateral limit cycle is decided without the estimation of the atmosphere density. Besides, the method adapted the uncertainty of the evolution of the atmosphere while the only-lifting control of the orbit will save the fuel of the satellite and reduce the frequency of the maintenance control. The simulation result demonstrates the validity of the method. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

Keyword ：

Maintenance Fuel economy Satellites Orbits Aerodynamic drag

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In this article, a three-dimensional integrated guidance and control (IGC) scheme is proposed for the hypersonic gliding vehicle (HGV), of which the control parameters are determined by enhanced fruit fly optimization algorithm (EFOA). Based on the dynamic and kinematical models, the IGC mathematical model of HGV is established. The control scheme is achieved using a dual-loop control structure. The backstepping-based guidance law can generate the commands of attack angle, sideslip angle, and bank angle, while the attitude control utilizes high-order sliding mode control to track the desired flight attitude angles. Additionally, the extended state observer is designed to estimate the uncertainties arising from the aerodynamic parameters and model dynamics. To obtain satisfactory control performance, the EFOA is introduced to search for optimal control parameters, which divides the whole fruit fly swarm into two subgroups, and introduces the chaotic mapping mechanism as well as the exponential decay search strategy to improve the ability of overall searching and local optimum jumping. The effectiveness and robustness of the proposed EFOA and IGC scheme are, respectively, verified through comparative experiments under different scenarios and Monte Carlo simulations.

Keyword ：

Design methodology Vehicle dynamics Optimization Uncertainty Aerodynamics Backstepping Mathematical models

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Abstract ：

A novel dynamic model of the functionally graded graphene platelet (FGGP) reinforced rotating pretwisted composite blade under the aerodynamic force and blade-casing rubbing is established for the first time. The blade is simplified to a FGGP reinforced rotating pretwisted composite cantilever plate. The dynamic model of the axial excitation produced by considering the aerodynamic force in the tip clearance includes two trigonometric functions with different frequencies. The subsonic airflow is considered as a transverse excitation which is derived by utilizing the vortex lattice method (VLM). The dynamic model expresses the changes of the nonuniform axial and contact forces through the tip clearance and rotating pretwisted plate-casing rubbing when the shaft is eccentric. Based on Rayleigh-Ritz method, the linear frequencies and mode shapes are obtained for the FGGP reinforced rotating pretwisted plate. The influences of the graphene distribution pattern, rotating pretwisted plate-casing rubbing, axial excitation in the tip clearance and geometric parameter on the frequencies are investigated. Using the obtained mode shapes, von-Karman type nonlinear geometric assumptions and Lagrange equation, the differential governing equations of motion are derived for the FGGP reinforced rotating pretwisted plate. The nonlinear vibrations under the 1:1 internal resonance at two critical rotating speeds is studied by using Runge-Kutta method. The amplitude-frequency and force-frequency response curves under the low and high critical rotating speeds are investigated by using numerical calculations. The obtained results demonstrate the influence of the rotating speed, frequency ratios and incoming flow speeds on the nonlinear vibrations of the FGGP reinforced rotating pretwisted plate. The dynamic model of the rubbing-impact for the rotating blade provides a theoretical basis for the blade-casing rubbing analysis. At the same time, this study is also used as a theoretical guidance to reduce the damage of the blade-casing rubbing and blade design.

Keyword ：

Graphene platelet Internal resonance Critical rotating speed Subsonic air flow excitation Rotating pretwisted plate

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In this work, we investigate the aero-thermo-elastic properties of graphene platelet (GPL)-reinforced nanocomposite lattice sandwich plates with pyramidal truss cores under supersonic airflow by consid-ering the temperature-and moisture-dependent properties for the first time. GPLs in the face sheets are uniformly distributed or in graded form, and the trusses of the lattice cells are uniformly reinforced by GPLs. The effective modulus of elasticity of the GPL-reinforced nanocomposite is obtained using the Halpin-Tsai model, while the rule of mixture is used to estimate the Poisson's ratio and mass density of nanocomposite. Through the stress and deformation analysis of a pyramidal cell, the equivalent transverse shear modulus of a lattice-sandwich-core layer is determined; then, the composite lattice sandwich plate is transformed into a three-layered-sandwich structure. The kinematic relationships of the face sheets and lattice core layer are established using Kirchhoff plate theory and first-order shear deformation theory, respectively. The aerodynamic load resulting from the supersonic flow is obtained using piston theory. The equations of motion governing the flutter behaviors of simply supported sandwich plates under supersonic flow are derived with the help of a standard Lagrange process and assumed mode method. A comprehensive parameter study is conducted to explore the effects of temperature, moisture, GPL distribution pattern, and GPL weight fraction on the aero-thermo-elastic flutter characteristics of the nanocomposite lattice sandwich plates.(c) 2023 Elsevier Masson SAS. All rights reserved.

Keyword ：

Flutter behaviors Graphene platelet reinforced nanocomposite Stability analysis Lattice sandwich plate Hygrothermal environment

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Abstract ：

In this study, the nonlinear dynamic behaviors are investigated for the functionally graded graphene platelet (FGGP) reinforced composite rotating warping blade under combined the aerodynamic force and centrifugal force. The blade is simplified to a FGGP reinforced com-posite rotating warping cantilever plate with a rectangular cross-section. Four distribu-tion patterns of the graphene platelets (GPLs) along the thickness of the plate are con-sidered when establishing the dynamic model. The effective material parameters, Poisson's ratio, mass density and Young's modulus of the FGGP reinforced composite rotating warp-ing cantilever plate are calculated based on the modified Halpin-Tsai model and mixture rule. Considering the warping effect, the dynamic governing equations of motion for the rotating FGGP reinforced composite cantilever plate subjected to the aerodynamic force and centrifugal force are established by using the first-order shear deformation theory and Hamilton's principle. Galerkin approach is exploited to transform the partial differ-ential equations of motion to the ordinary differential equations of motion the FGGP re-inforced composite rotating warping cantilever plate. Four-dimensional autonomous aver-aging equations of the system are obtained by using the asymptotic perturbation method. The parameter analyzes on the amplitude-frequency and force-amplitude responses of the FGGP reinforced composite rotating warping cantilever plate are carried out by consid-ering the 1:2 internal resonance and principal parametric resonance. The stability of the steady solution of the autonomous system is discussed. The influences of the GPL distri-bution patterns, rotating speed, aerodynamic force and damping on the chaotic dynamics are investigated for the FGGP reinforced composite rotating warping cantilever plate.(c) 2022 Elsevier Inc. All rights reserved.

Keyword ：

Amplitude -frequency response curve Blade Composite cantilever rotating warping plate Chaotic dynamics Functionally graded graphene platelets

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Abstract ：

For the first time, this paper investigates the temperature-dependent aerothermoelastic properties of nano-composite pyramidal lattice sandwich beams in supersonic airflow. A nonuniform temperature distribution along the thickness is considered. The face sheets and core of the sandwich beam are fabricated from graphene platelet (GPL)-reinforced nanocomposites. A refined thermo-mechanical equivalent model is established to determine the effective shear modulus of the lattice core subjected to a nonuniform temperature distribution. Then, the core transforms into a continuum layer. Subsequently, the beams with lattice cores were modeled as equivalent sandwich structures composed of three continuum layers. The effective modulus of elasticity of the nano-composites was calculated using the Halpin-Tsai micromechanics model combined with the mixture rule. The aerodynamic pressure was calculated using the first-order supersonic piston theory. The aerothermoelastic properties of the sandwich beam were investigated by analyzing the critical flutter aerodynamic pressure and time-dependent responses of structures. The influences of nonuniform temperature distribution, GPL re-inforcements, and end restrictions on the flutter characteristics of beams are addressed using some parameter examples.

Keyword ：

graphene platelets (GPLs) reinforced composite Nonuniform thermal environments Flutter properties material Lattice sandwich beam Supersonic airflow

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