Wake vortex encounter severity for rotorcraft in final approach

Lawrence, Ben; Padfield, Gareth D.

doi:10.1016/j.ast.2007.09.006

Cited by 8 publications

(6 citation statements)

References 9 publications

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“…4) The series of publications on helicopter handling qualities in parallel wake encounters (Refs. [11][12][13][14] suggest that the flight dynamics situation may be significantly different from the static stability observed in this research and should be investigated.…”

Section: Recommendationsmentioning

confidence: 69%

Numerical and Experimental Investigation into the Aerodynamic Benefits of Rotorcraft Formation Flight

Voskuijl¹,

Vries²,

Veen³

et al. 2020

Proceedings of the Vertical Flight Society 76th Annual Forum

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The use of formation flight to achieve aerodynamic benefit as applied to rotorcraft is, unlike its fixed-wing counterpart, an unproven principle. This document presents a proof-of-concept of rotorcraft formation flight through a numerical research study, supported by results from an independent wind-tunnel experiment. In both cases, two helicopters are placed in an echelon formation aligned on the advancing side of the main rotor, though they do not simulate directly comparable flight conditions. The vertical and lateral alignment is varied in order to observe the achievable reductions in main rotor power required during cruise flight. The wind-tunnel experiment data yields an estimated maximum total power reduction for the secondary aircraft of 24%, while the numerical models yield reductions between 20% and 34% dependent on flight velocity. Both experiments predict a higher potential for aerodynamic benefit than observed for fixed-wing formations, which is contributed to the asymmetric upwash profile in the rotor wake. Optimal lateral alignment of both experimental and numerical results is found to feature overlap of the rotor disk areas due to circular area effects. Experimental data shows an optimal vertical alignment of the secondary rotorcraft below the primary, due to wake displacement. This is not present in the numerical simulations as a result of the applied leader wake modeling.

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Section: Recommendationsmentioning

confidence: 69%

Numerical and Experimental Investigation into the Aerodynamic Benefits of Rotorcraft Formation Flight

Voskuijl¹,

Vries²,

Veen³

et al. 2020

Proceedings of the Vertical Flight Society 76th Annual Forum

View full text Add to dashboard Cite

show abstract

“…For comparison, the circulation strength of wake vortices from large fixed-wing aircraft [18] and rotorcraft [19][20][21] have been characterized from numerous flight tests and the decay of the circulation strength over distance and time has been observed. The wake vortices from a leading aircraft can induce undesirable motion on fixed-wing aircraft [22] and rotorcraft [23,24], so understanding the decay rate of wake vortices helps to determine the minimum separation that must be maintained between aircraft to mitigate the hazard due to the wake vortices [25,26].…”

Section: Introductionmentioning

confidence: 99%

A Study on Circulation Strength Decay Over Time of Quadrotor Wake Using Large Eddy Simulation

Nathanael

Wang

Low

2022

AIAA SCITECH 2022 Forum

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As the use of multi-rotors is becoming common, understanding how the wake vortices develop and decay from a multi-rotor is important to reduce the effect of wake vortices on other multi-rotors and ensure their safety during operation by applying a wake separation minima. This paper proposes a method of flow simulation in ANSYS Fluent to study the decay of wake vortices from quadrotor propellers as the vortices evolve over distance and time. First, the near-field wake flow from the quadrotor propellers was simulated using Reynolds-Averaged Navier-Stokes (RANS) turbulence model. The velocity profile in the quadrotor frame of reference was then extracted to be applied for a flow simulation using Large Eddy Simulation (LES). The circulation strength as a function of distance could then be calculated, but it was limited by the length of the computational grid due to the wake flow being seen from the quadrotor frame of reference. To change into the stationary frame of reference, the interpolation data from the first stage LES was exported and modified by subtracting the freestream velocity from the velocity component in the freestream direction. The modified interpolation data was then used for the second stage LES, and the circulation strength in terms of time could be calculated from the resulting wake flow. Three cases of flow simulation are presented in this paper: first using 380-mm-diameter propellers based on the SUI Endurance quadrotor propellers with forward flight speed of 6 m/s, second using the 380-mm-diameter propellers with 12 m/s speed, and third using 240-mm-diameter propellers (similar to the propellers of DJI Phantom quadrotor) with 12 m/s speed. Findings regarding the decay of wake vortex from multi-rotor vehicles will help in determining the safe separation distance required to mitigate the hazards due to wake vortex encounters and ensure the safety of multi-rotor vehicles.

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“…Vortex-rotor aerodynamic interaction is a phenomenon that was more intensely investigated by flight testing and by numerical simulation from the mid-1970s to the end of the 1980s with respect to flight mechanics response of helicopters encountering the wake of large and heavy fixed-wing aircraft [1][2][3][4][5]. The subject was taken up again from 2000 on for handling qualities aspects [6][7][8]. All these were based on numerical simulation with different degrees of simplifications.…”

Section: Introductionmentioning

confidence: 99%

Analytic solution of in-plane vortex–rotor interactions with arbitrary orientation and its impact on rotor trim

Wall

Wall²

2021

CEAS Aeronaut J

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The general aerodynamic problem of arbitrarily oriented in-plane vortex-rotor interaction was investigated in the past only by numerical simulation. Just one special case of in-plane vortex-rotor interaction with the vortex axis in flight direction was recently solved analytically. In this article, the analytical solution for arbitrary in-plane vortex orientation and position relative to the rotor is given for the first time. The solution of the integrals involved as derived here encompasses and simplifies the previous derivation of the special case significantly. Results provide the vortex impact on rotor trim (thrust, aerodynamic rolling and pitching moments about the hub) and the rotor controls required to mitigate these disturbances. For the special case with the vortex axis in flight direction, the results are identical to the former solution and results for the other in-plane vortex orientations and positions agree with the numerical results obtained so far.

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Wake vortex encounter severity for rotorcraft in final approach

Cited by 8 publications

References 9 publications

Numerical and Experimental Investigation into the Aerodynamic Benefits of Rotorcraft Formation Flight

Numerical and Experimental Investigation into the Aerodynamic Benefits of Rotorcraft Formation Flight

A Study on Circulation Strength Decay Over Time of Quadrotor Wake Using Large Eddy Simulation

Analytic solution of in-plane vortex–rotor interactions with arbitrary orientation and its impact on rotor trim

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