scholarly journals Unsteady aerodynamic characteristics of a bionic flapping wing in three-dimensional composite motion

AIP Advances ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 015109
Author(s):  
Lun Li ◽  
Jiulong Xu ◽  
Yuan Gao ◽  
Jinghong Yang ◽  
Fan Bai ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
Flapping Wing ◽  
Unsteady Aerodynamic

scholarly journals Unsteady Aerodynamic Characteristics Simulations of Rotor Airfoil under Oscillating Freestream Velocity

2020 ◽  
Vol 10 (5) ◽  
pp. 1822
Author(s):  
Qing Wang ◽  
Qijun Zhao
Keyword(s):  
Three Dimensional ◽  
Grid Method ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Critical Value ◽  
Dynamic Stall ◽  
Navier Stokes ◽  
Freestream Velocity ◽  
Unsteady Aerodynamic ◽  
Edge Vortex

The dynamic stall characteristics of rotor airfoil are researched by employing unsteady Reynolds-Averaged Navier-Stokes (RANS) method under oscillating freestream velocity conditions. In order to simulate the oscillating freestream velocity of airfoil under dynamic stall conditions, the moving-embedded grid method is employed to simulate the oscillating velocity. By comparing the simulated dynamic stall characteristics of two-dimensional airfoil and three-dimensional rotor, it is indicated that the dynamic stall characteristics of airfoil under oscillating freestream velocity reflect the actual dynamic stall characteristics of rotor airfoil in forward flight more accurately. By comparing the simulated results of OA209 airfoil under coupled freestream velocity/pitching oscillation conditions, it is indicated that the dynamic stall characteristics of airfoil associate with the critical value of Cp peaks (i.e., the dynamic stall characteristics of OA209 airfoil would be enhanced when the maximum negative pressure is larger than −1.08, and suppressed when this value is smaller than −1.08). By comparing the characteristics of vortices under different oscillating velocities, it indicates that the dissipation rate of leading edge vortex presents as exponent characteristics, and it is not sensitive to different oscillating velocities.

scholarly journals Aerodynamic Performance of the Three-Dimensional Lumped Flexibility Bionic Hovering Wing

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Zhu Jianyang ◽  
Jiang Lin ◽  
Hou Yu
Keyword(s):  
Numerical Analysis ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Performance ◽  
Flapping Wing ◽  
Iterative Coupling ◽  
Insect Wing ◽  
Flexible Wing ◽  
At Resonance ◽  
Systematic Synthesis

Understanding the effect of flexibility on the aerodynamic characteristics of the wing is one of the most important considerations for successfully designing a flapping wing micro aero vehicle (FMAV). This paper aims at providing a systematic synthesis on the flexibility effects on the hovering performance of the bionic wing based on the numerical analysis approach. We construct a novel three-dimensional bionic wing, which has lumped flexibility at the root, and develop an iterative coupling program to simulate the interaction between the flexible wing and fluid. The effects of flexibility on the hovering performance of the three-dimensional flapping wing are investigated, and the results indicate that the best performance of the wing is achieved when the wing flaps at resonance and has the density close to the natural insect wing. The feasibility of using lumped flexibility wings driven by a simple harmonic flapping for designing efficient FMAV is also concluded in this study.

scholarly journals Unsteady Aerodynamic Characteristics of Transversely Inclined Prisms Under Forced-Vibration---The Base Intensification Phenomenon

2021 ◽  
Author(s):  
Zengshun Chen ◽  
Jie Bai ◽  
Cruz Y. Li ◽  
Yemeng Xu ◽  
Jianmin Hua ◽  
...  
Keyword(s):  
Forced Vibration ◽  
Three Dimensional ◽  
Horseshoe Vortex ◽  
Aerodynamic Characteristics ◽  
Experimental Comparison ◽  
Force Coefficient ◽  
Aerodynamic Damping ◽  
Wind Speeds ◽  
Unsteady Aerodynamic ◽  
Inclination Angles

Abstract This work, through a series of forced-vibration wind tunnel experiments, investigates the aerodynamic characteristics of square prisms subject to the transverse inclination. An aeroelastic prism was tested under different wind speeds, inclination angles, and oscillation amplitudes. Through analysis on the mean pressure distribution, local force coefficient, force spectra, and aerodynamic damping coefficient, the unsteady aerodynamic characteristics of the configuration were revealed. Empirical observations discovered the Base Intensification phenomenon, which refers to a fundamental change in the structure’s aerodynamic behaviors given any degrees of transverse inclination. Specifically, it is the intensification of the aerodynamic loading, vortical activities, and aerodynamic damping on only the lower portion of an inclined structure. The phenomenon, being almost impactless to the upper portion, is also insensitive to changes in inclination angle and tip amplitude once triggered by the initial inclination. Analysis also revealed that the origin of Base Intensification phenomenon traces back to fix-end three-dimensional effects like the horseshoe vortex, instead of the predominant Bérnard-Kármán vortex shedding. Moreover, results showed that wind speed is the decisive factor for the structure’s crosswind motions. Inside the lock-in region, structure loadings, vortical activities, and the effects of Base Intensification are significantly amplified. Beyond the range, the configuration gradually resorts to a quasi-steady linearity. Finally, results from the force-vibration tests were used for the prediction of structure response. Experimental comparison revealed that the predictions notably outperform those based on rigid tests, forecasting the actual responses with a markedly improved accuracy.

scholarly journals Numerical Calculations on the Unsteady Aerodynamic Force of the Tilt-Rotor Aircraft in Conversion Mode

2019 ◽  
Vol 2019 ◽  
pp. 1-15
Author(s):  
Hao Chen
Keyword(s):  
Aerodynamic Force ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
Computational Method ◽  
Finite Volume Scheme ◽  
Continuous Transition ◽  
Tilt Rotor ◽  
Unsteady Aerodynamic ◽  
Conversion Mode ◽  
Predictor Corrector

A computational method is developed in order to predict the unsteady aerodynamic characteristics of the tilt-rotor aircraft in conversion mode. In this approach, the rotor is modeled as an actuator disk so that the effect of individual blades can be ignored. A novel predictor-corrector-based dynamic mesh method is presented for dealing with extremely large mesh deformation during a conversion process. The dual time-stepping approach and the finite volume scheme are applied to solve the unsteady N-S equation. A parallel algorithm is utilized in this work to improve the computational efficiency. By using the present method, quantitative and qualitative comparisons are made between the aerodynamic coefficients obtained in the quasi-steady fixed conversion mode and the time-accurate continuous transition flight condition. Both two-dimensional (2D) and three-dimensional (3D) computations are carried out. The influence of the tilt modes and the tilt period time on the unsteady aerodynamic forces are also studied. Numerical results demonstrate that the developed method is effective in simulating the aerodynamic characteristics of the tilt-rotor aircraft in conversion mode.

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