Numerical investigation of dynamic stall reduction on helicopter blade section in forward flight by an airfoil deformation method

Karimian, S. M. H.; Aramian, S. V.; Abdolahifar, Abolfazl

doi:10.1007/s40430-021-02822-y

Cited by 6 publications

(2 citation statements)

References 36 publications

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“…A numerical investigation focused on the blade section of a helicopter rotor during forward flight aimed to reduce or alleviate dynamic stall on the retreating blade [48]. For validation and verification purposes, simulations were conducted for flows around static and pitching airfoils at constant and variable Mach numbers.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of the Transient Flow around the Combined Morphing Leading-Edge and Trailing-Edge Airfoil

Bashir,

Negahban,

Botez

et al. 2024

Biomimetics

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An integrated approach to active flow control is proposed by finding both the drooping leading edge and the morphing trailing edge for flow management. This strategy aims to manage flow separation control by utilizing the synergistic effects of both control mechanisms, which we call the combined morphing leading edge and trailing edge (CoMpLETE) technique. This design is inspired by a bionic porpoise nose and the flap movements of the cetacean species. The motion of this mechanism achieves a continuous, wave-like, variable airfoil camber. The dynamic motion of the airfoil’s upper and lower surface coordinates in response to unsteady conditions is achieved by combining the thickness-to-chord (t/c) distribution with the time-dependent camber line equation. A parameterization model was constructed to mimic the motion around the morphing airfoil at various deflection amplitudes at the stall angle of attack and morphing actuation start times. The mean properties and qualitative trends of the flow phenomena are captured by the transition SST (shear stress transport) model. The effectiveness of the dynamically morphing airfoil as a flow control approach is evaluated by obtaining flow field data, such as velocity streamlines, vorticity contours, and aerodynamic forces. Different cases are investigated for the CoMpLETE morphing airfoil, which evaluates the airfoil’s parameters, such as its morphing location, deflection amplitude, and morphing starting time. The morphing airfoil’s performance is analyzed to provide further insights into the dynamic lift and drag force variations at pre-defined deflection frequencies of 0.5 Hz, 1 Hz, and 2 Hz. The findings demonstrate that adjusting the airfoil camber reduces streamwise adverse pressure gradients, thus preventing significant flow separation. Although the trailing-edge deflection and its location along the chord influence the generation and separation of the leading-edge vortex (LEV), these results show that the combined effect of the morphing leading edge and trailing edge has the potential to mitigate flow separation. The morphing airfoil successfully contributes to the flow reattachment and significantly increases the maximum lift coefficient (cl,max)). This work also broadens its focus to investigate the aerodynamic effects of a dynamically morphing leading and trailing edge, which seamlessly transitions along the side edges. The aerodynamic performance analysis is investigated across varying morphing frequencies, amplitudes, and actuation times.

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Section: Introductionmentioning

confidence: 99%

Numerical Simulation of the Transient Flow around the Combined Morphing Leading-Edge and Trailing-Edge Airfoil

Bashir,

Negahban,

Botez

et al. 2024

Biomimetics

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“…These results show how TEF reduced wind turbine blade loads changes. Another study analysed the flow field around a helicopter blade in forward flight [77]. The two-dimensional model incorporated forward flight speed, resulting in a time-variable aerofoil flow speed.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of the dynamic stall reduction on the UAS-S45 aerofoil using the optimised aerofoil method

Bashir,

Zonzini,

Longtin Martel

et al. 2023

Aeronaut. j.

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This paper investigates the effect of the optimised morphing leading edge (MLE) and the morphing trailing edge (MTE) on dynamic stall vortices (DSV) for a pitching aerofoil through numerical simulations. In the first stage of the methodology, the optimisation of the UAS-S45 aerofoil was performed using a morphing optimisation framework. The mathematical model used Bezier-Parsec parametrisation, and the particle swarm optimisation algorithm was coupled with a pattern search with the aim of designing an aerodynamically efficient UAS-45 aerofoil. The $\gamma - R{e_\theta }$ transition turbulence model was firstly applied to predict the laminar to turbulent flow transition. The morphing aerofoil increased the overall aerodynamic performances while delaying boundary layer separation. Secondly, the unsteady analysis of the UAS-S45 aerofoil and its morphing configurations was carried out and the unsteady flow field and aerodynamic forces were analysed at the Reynolds number of 2.4 × 106 and five different reduced frequencies of k = 0.05, 0.08, 1.2, 1.6 and 2.0. The lift ( ${C_L})$ , drag ( ${C_D})$ and moment ( ${C_M})\;$ coefficients variations with the angle-of-attack of the reference and morphing aerofoils were compared. It was found that a higher reduced frequencies of 1.2 to 2 stabilised the leading-edge vortex that provided its lift variation in the dynamic stall phase. The maximum lift $\left( {{C_{L,max}}} \right)$ and drag $\left( {{C_{D,max}}} \right)\;$ coefficients and the stall angles of attack are evaluated for all studied reduced frequencies. The numerical results have shown that the new radius of curvature of the MLE aerofoil can minimise the streamwise adverse pressure gradient and prevent significant flow separation and suppress the formation of the DSV. Furthermore, it was shown that the morphing aerofoil delayed the stall angle-of-attack by 14.26% with respect to the reference aerofoil, and that the ${C_{L,max}}\;$ of the aerofoil increased from 2.49 to 3.04. However, while the MTE aerofoil was found to increase the overall lift coefficient and the ${C_{L,max}}$ , it did not control the dynamic stall. Vorticity behaviour during DSV generation and detachment has shown that the MTE can change the vortices’ evolution and increase vorticity flux from the leading-edge shear layer, thus increasing DSV circulation. The conclusion that can be drawn from this study is that the fixed drooped morphing leading edge aerofoils have the potential to control the dynamic stall. These findings contribute to a better understanding of the flow analysis of morphing aerofoils in an unsteady flow.

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Numerical study of dynamic stall effects on VR‐12 airfoil with pitch oscillation and accelerated inflow

Zolghadr,

Khoshnevis

2024

Energy Science & Engineering

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This study investigates the effects of positive horizontal acceleration of the freestream velocity on a pitch‐oscillating VR‐12 airfoil using computational fluid dynamics. The shear stress transport k–ω model, coupled with a low‐Reynolds number correction, was employed for Re <105 during dynamic stall. The flow equations were solved in two‐dimensional, incompressible form using the finite volume method. The study examined various parameters, including positive acceleration values of the inflow and the angle of attack of the airfoil, to determine their impact on lift and drag coefficients, as well as the ratio. Additionally, the maximum lift coefficient was analyzed under different inflow and airfoil motion conditions. The results indicate that aerodynamic force coefficients and the ratio are influenced by both the attack angle and the acceleration of the inflow. Furthermore, inflow acceleration affects the onset of dynamic stall conditions. Generally, inflow acceleration modifies the lift coefficient of the airfoil during the upstroke, while having minimal effect on the drag coefficient, except near dynamic stall points. The findings also suggest that, for a specific airfoil, the sequence of factors with the greatest influence on lift force generation before static stall occurs is as follows: asymmetric airfoil oscillation, symmetrical airfoil oscillation, accelerated inflow, constant velocity inflow, and static airfoil.

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Numerical investigation of dynamic stall reduction on helicopter blade section in forward flight by an airfoil deformation method

Cited by 6 publications

References 36 publications

Numerical Simulation of the Transient Flow around the Combined Morphing Leading-Edge and Trailing-Edge Airfoil

Numerical Simulation of the Transient Flow around the Combined Morphing Leading-Edge and Trailing-Edge Airfoil

Numerical investigation of the dynamic stall reduction on the UAS-S45 aerofoil using the optimised aerofoil method

Numerical study of dynamic stall effects on VR‐12 airfoil with pitch oscillation and accelerated inflow

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