Numerical Investigation of the Performance of Pitching Airfoils at High Amplitudes

Rahromostaqim, Mahsa; Posa, Antonio; Balaras, Elias

doi:10.2514/1.j054424

Cited by 28 publications

(10 citation statements)

References 32 publications

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“…Furthermore, hovering efficiency increases when camber varies from 8 to 0 per cent and then decreases when inverse camber rises. Obviously, there are four force peaks in all figures, which have been proved by Rahromostaqim et al (2016). Higher frequencies and amplitudes of pitching motion are associated with an increased hysteresis of the force coefficients between the pitch-up and pitch-down intervals.…”

Section: Resultsmentioning

confidence: 53%

The effect of aerofoil camber on cycloidal propellers

Zhang

Wang

2018

AEAT

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Purpose This paper aims to investigate the impact of aerofoil camber on the performance of micro-air-vehicle-scale cycloidal propellers. Design/methodology/approach First, experiments were conducted to validate the numerical methodology. After that, three turbulent models were compared to select the most accurate one. Then, 2D numerical simulation was carried out on 11 aerofoils with different cambers, including five cambered aerofoils, one symmetrical aerofoil and five inverse cambered aerofoils. The inverse cambered aerofoils are symmetrical about the chord line to the corresponding cambered ones. Findings The cycloidal propeller with large cambered aerofoil gives the lowest hovering efficiency, but with symmetrical aerofoil or small inverse cambered aerofoil shows the highest. Also, blades with large cambered aerofoil display high performance at the upper part of its trajectory, while with symmetrical aerofoil or the inverse cambered aerofoil have their best at the lower part. In addition, intensified downwash can be observed in the rotor cage for all cases. When a blade runs through the top-left part of its circle path, all cases display the feature of deep dynamic stall. When the blade travels through the nadir of its path, the actual angle of attack is close to zero due to the strong downwash. Furthermore, there exits intensified blade-vortex interaction induced by the preceding blade for large cambered aerofoils at the lower-right part of its trajectory. Practical implications This paper develops a new cycloidal propeller which is more efficient than the one already present. Originality/value This paper discovers that the aerofoil camber is a vital design parameter in the performance of cycloidal propeller, and the authors expect that the rotor with deformable aerofoil on camber would achieve much higher efficiency.

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Section: Resultsmentioning

confidence: 53%

The effect of aerofoil camber on cycloidal propellers

Zhang

Wang

2018

AEAT

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“…When low-frequency oscillation [13,14], separation point showed quasi-period movement thus flow structures around the airfoil can generate reverse flow region. Additionally, high amplitudes of the pitching motion were also associated with an increased hysteresis of the force coefficients between the upstroke and downstroke [3]. And the onset of vortex formation was found to occur at earlier times with higher amplitude [15].…”

Section: Nomenclature αmentioning

confidence: 91%

“…Many factors have significant influences over how vortical evolution affects aerodynamic loads. In general, pitching motion of an airfoil or flat plate is dominated by the amplitude α m [1][2][3] and reduced frequency k (k = πf c/U ∞ ) [1,2]. Besides, Reynolds number Re [4][5][6][7] , turbulence intensity T u [6], wall effect [8,9] and flexible deformation [10] are noteworthy parameters.…”

Section: Nomenclature αmentioning

confidence: 99%

Effects of Pivot Point and Spacing on the Aerodynamic Characteristics of Tilting Biplane Airfoils

et al. 2022

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“…Details on the method, as well as applications, including rotating machinery cases, can be found in Refs. [30][31][32][33][34][35][36][37], while the implementation in the present configuration is outlined in Refs. [27] and [28].…”

Section: Problem Formulation and Methodsmentioning

confidence: 99%

Investigation of Separation Phenomena in a Radial Pump at Reduced Flow Rate by Large-Eddy Simulation

Posa

Lippolis

Balaras

2016

Journal of Fluids Engineering

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Turbopumps operating at reduced flow rates experience significant separation and backflow phenomena. Although Reynolds-Averaged Navier–Stokes (RANS) approaches proved to be usually able to capture the main flow features at design working conditions, previous numerical studies in the literature verified that eddy-resolving techniques are required in order to simulate the strong secondary flows generated at reduced loads. Here, highly resolved large-eddy simulations (LES) of a radial pump with a vaned diffuser are reported. The results are compared to particle image velocimetry (PIV) experiments in the literature. The main focus of the present work is to investigate the separation and backflow phenomena occurring at reduced flow rates. Our results indicate that the effect of these phenomena extends up to the impeller inflow: they involve the outer radii of the impeller vanes, influencing significantly the turbulent statistics of the flow. Also in the diffuser vanes, a strong spanwise evolution of the flow has been observed at the reduced load, with reverse flow, located mainly on the shroud side and on the suction side (SS) of the stationary channels, especially near the leading edge of the diffuser blades.

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Numerical Investigation of the Performance of Pitching Airfoils at High Amplitudes

Cited by 28 publications

References 32 publications

The effect of aerofoil camber on cycloidal propellers

The effect of aerofoil camber on cycloidal propellers

Effects of Pivot Point and Spacing on the Aerodynamic Characteristics of Tilting Biplane Airfoils

Investigation of Separation Phenomena in a Radial Pump at Reduced Flow Rate by Large-Eddy Simulation

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