Aerodynamic investigation of an airfoil under two hovering modes considering ground effect

Younsi, Abdelhakim; El-Hadj, A. Abdellah; Rahim, Shayfull Zamree Bin Abd; Rezoug, Tahar

doi:10.1016/j.jfluidstructs.2019.102759

Cited by 8 publications

(3 citation statements)

References 14 publications

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“…The convection term in the momentum equation was discretized using a second-order upwind scheme as it was used in our previous study. 21 Finally, for the temporal discretization, a second-order implicit time integration was used.…”

Section: Mathematical Modelingmentioning

confidence: 99%

Effects of the wing spacing, phase difference, and downstroke ratio on flapping tandem wings

Younsi

El-Hadj

Rahim

et al. 2022

Proceedings of the Institution of Mechanical Engineers, Part C:

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In this paper, a numerical study on the effects of the asymmetry in flapping duration, wing spacing, and phase difference on the aerodynamic performance of flapping tandem wings is carried out. Three downstroke ratios to flapping period ( ξ) are chosen, ξ = 0.35, ξ = 0.5, and ξ = 0.65, where ξ = 0.5 represents a symmetrical stroke. Four values of wing spacing L are selected: 1.25c, 1.5c, 1.75c, and 2c (c is the wing chord length), while the phase difference between the fore and hind wings is ranged from 0° to 270° with an interval of 90°. The effects of these parameters on the lift and thrust generation are investigated. A study of the energy consumption and the flight efficiency has also been taken into consideration. The flow variables in the computational domain around the flapping tandem wings are solved using the commercial software Fluent. The results show that the effects of the downstroke ratio on the aerodynamic performance are significantly higher than the effects of the wing spacing and the phase difference. The thrust generation and efficiency are maximized in the case with faster upstroke ( ξ =0.65). However, the maximum lift generation and efficiency are located in the case with faster downstroke ( ξ =0.35) instead. The optimal configuration is obtained using a minimum of wing spacing (1.25c) and phase angle (0°) with a downstroke ratio of 0.436.

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Section: Mathematical Modelingmentioning

confidence: 99%

Effects of the wing spacing, phase difference, and downstroke ratio on flapping tandem wings

Younsi

El-Hadj

Rahim

et al. 2022

Proceedings of the Institution of Mechanical Engineers, Part C:

Self Cite

View full text Add to dashboard Cite

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“…Reducing the time of the upstroke increased the mean thrust coefficient. Younsi et al 27 examined the impact of the ground on an elliptic airfoil experiencing two hovering modes, "water treading" and "normal. " The unstable, laminar, incompressible Navier-Stokes equations were solved using the finite volume approach at Re=100.…”

Section: Reduced Frequency C Lmentioning

confidence: 99%

Numerical investigation on the aerodynamic efficiency of bio-inspired corrugated and cambered airfoils in ground effect

Abdizadeh

Farokhinejad

Ghasemloo

2022

Sci Rep

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This research numerically investigates the flapping motion effect on the flow around two subsonic airfoils near a ground wall. Thus far, the aerodynamic efficiency of the dragonfly-inspired flapping airfoil has not been challenged by an asymmetric cambered airfoil considering the ground effect phenomenon, especially in the MAV flight range. The analysis is carried out on the basis of an unsteady Reynolds-averaged Navier-stokes (URANS) simulation, whereby the Transition SST turbulence model simulates the flow characteristics. Dragonfly-inspired and NACA4412 airfoils are selected in this research to assess the geometry effect on aerodynamic efficiency. Moreover, the impacts of Reynolds number (Re), Strouhal number (St), and average ground clearance of the flapping airfoil are investigated. The results indicate a direct relationship between the airfoil’s aerodynamic performance ($$C_l$$ C l /$$C_d$$ C d ) and the ground effect. The $$C_l$$ C l /$$C_d$$ C d increases by reducing the airfoil and ground distance, especially at $$h_{0}=c$$ h 0 = c . At $$Re=5\times 10^4$$ R e = 5 × 10 4 , by increasing the St from 0.2 to 0.6, the values of $$C_l$$ C l /$$C_d$$ C d decrease from 10.34 to 2.1 and 3.22 to 1.8 for NACA4412 and dragonfly airfoils, respectively. As a result, the $$C_l$$ C l /$$C_d$$ C d of the NACA4412 airfoil is better than that of the dragonfly airfoil, especially at low oscillation frequency. The efficiency difference between the two airfoils at St=0.6 is approximately 14%, indicating that the $$C_l$$ C l /$$C_d$$ C d difference decreases substantially with increasing frequency. For $$Re=5\times 10^3$$ R e = 5 × 10 3 , the results show the dragonfly airfoil to have better $$C_l$$ C l /$$C_d$$ C d in all frequencies than the NACA4412 airfoil.

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“…Li et al [7] conducted a study on designing wind turbine airfoils that are used in low rated wind speed locations and found that the framework given in the study enables the design of various airfoils to meet site-specific blade requirements. Younsi et al [8] investigated the aerodynamics of an elliptic airfoil exposed to translational and rotational motion while accounting for ground effects. They found that the majority of lift generation is due to delayed stall coupled with leading-edge vortex processes and rapid pitching.…”

Section: Introductionmentioning

confidence: 99%

Aerodynamic Properties Identification for Small-Size Wind Turbine Blade Airfoil Sections Using the CFD Method

Fadaei,

Langlois,

Afagh

2023

Proceedings of the 10th International Conference on Control, Dynamic Systems, and Robotics (CDSR 2023)

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In this paper, three airfoil sections at the root, middle, and tip of the blade of the Sunforce 400 W conventional wind turbine were investigated at different angles of attack using Computational Fluid Dynamics (CFD) to identify the stall occurrence correlated with the maximum of the lift coefficient. To verify the CFD models, firstly, simulation results of the NACA 4412 airfoil were calculated using the XFOIL code and the CFD method, and compared against available experimental data when using a k-ω SST turbulence model. Then, lift coefficients for the three airfoil sections of the small-size wind turbine blade obtained from the CFD simulations and k-ω SST turbulence model, were calculated and compared with each other. The simulations were performed at three flow speeds, V = 3, 5 and 7m/s, while the angle of attack was varied between -2 and 15 degrees until stall occurred. Flow separation occurred close to the leading edge of the airfoil at the middle and tip of the blade at lower angles of attack, while the airfoil section at the root of the blade was more successful in keeping the flow attached to the surface.

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Aerodynamic investigation of an airfoil under two hovering modes considering ground effect

Cited by 8 publications

References 14 publications

Effects of the wing spacing, phase difference, and downstroke ratio on flapping tandem wings

Effects of the wing spacing, phase difference, and downstroke ratio on flapping tandem wings

Numerical investigation on the aerodynamic efficiency of bio-inspired corrugated and cambered airfoils in ground effect

Aerodynamic Properties Identification for Small-Size Wind Turbine Blade Airfoil Sections Using the CFD Method

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