Vortical Sheet Behavior in the Wake of a Rotor in Ground Effect

Milluzzo, Joseph; Leishman, J. Gordon

doi:10.2514/1.j054498

Cited by 21 publications

(12 citation statements)

References 28 publications

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“…The particles are driven by the flowfield velocities and their position in time are obtained by integrating their equation of motion, the particles are assumed massless. The integration method used is a second order Runge-Kutta , and the equation of motion for massless particles is: (4) x p = (x p0 + ut)…”

Section: Particle Trackingmentioning

confidence: 99%

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CFD Analysis of a micro rotor in ground effect

Rovere

Steijl

Barakos

2020

AIAA Scitech 2020 Forum

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In this work, computational fluid dynamics is used to compare experimental results for a two-bladed small rotor Out of Ground Effect and In Ground Effect conditions. The paper focuses on the evalutation and prediction of the performance of the rotor and investigates the outwash generated in ground effect. Time and phase averaged outflow velocities with two different scaling methods are compared with experiments. The results are also scaled to a full-size rotor, and compared with the PAXman model of crew operating in close rotor proximity. A particle pickup model is also used showing the dust cloud generated by the rotor. Nomenclature Acronyms CF D Computational Fluid Dynamics DV E Degraded Visual Environment IGE In Ground Effect M T OW Maximum TakeOff Weight M U SCL Monotone Upstream Centred Schemes for Conservation Laws OGE Out of Ground Effect P IV Particle Image Velocimetry Greek ν Kinematic viscosity, m 2 /s Ω Rotor angular velocity, rad/s Ψ Local azimuth angle, deg ρ Density, kg/m 3 τ w Wall shear stress, kg/ms 2 θ Collective pitch at three-quarter radius, deg Latin a Speed of sound, m/s c Blade chord, m C Q Rotor torque coefficient, C Q = Q

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Section: Particle Trackingmentioning

confidence: 99%

“…The influence of the ground on the flowfield generated by a lifting rotor has been discussed in several works, using from full-scale aircraft [1] to small, isolated, rotors [2], [3] and [4]. This interaction between the flowflield and the ground changes the direction of the induced flow from vertical (downwash) to radial flow (outwash).…”

Section: Introductionmentioning

confidence: 99%

CFD Analysis of a micro rotor in ground effect

Rovere

Steijl

Barakos

2020

AIAA Scitech 2020 Forum

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“…elicopters operating in ground effect (IGE) have so far been widely investigated. Nevertheless, there are still issues related to the downwash and outwash of rotors that need investigating [1][2][3]. Contrary to a rotor operating out of ground effect (OGE), the presence of the ground significantly alters the rotor aerodynamics and generates more complex and unsteady flow field.…”

Section: Iintroductionmentioning

confidence: 99%

“…7, Phillips et al stated that the brownout characteristics of rotorcraft are extremely sensitive to the vortices of the wake, so the geometry and dynamics of the individual vortical structures within the flow alter markedly the resultant structure of the dust cloud under brownout condition. Additionally, the fundamental understanding of the fluid dynamics of the rotor wake as it interacts with the ground is a prerequisite to understanding and mitigating brownout [1]. However, investigations are mainly focus on the evolution and formation of wake of an isolated single rotor system.…”

Section: Iintroductionmentioning

confidence: 99%

Vortex Approach for Downwash and Outwash of Tandem Rotors in Ground Effect

Tan

Sun

Barakos

2018

Journal of Aircraft

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A vortex-based approach is employed to predict downwash and outwash of a tandem rotor in ground effect and provide an understanding of its wake. The aerodynamic loads of the blades are represented through a panel method, and the behavior of the wake is captured by a viscous vortex particle method. The viscous effects of the ground are accounted for by a viscous boundary model satisfying the no-slip and non-penetration boundary conditions. The method is first validated for an isolated full-scale Lynx tail rotor and a 172 mm-diameter scale rotor in ground effect. The results show that the predicted trajectories of the tip vortices and the radial velocity profiles compare favorably with experiments and published CFD results. Results for a model CH-47D are then compared with experiments for the downwash and outwash of the tandem rotor. As opposed to the isolated single rotor, a radial outward expansion in the overlapping area is observed, and the peak and the corresponding vertical distance of the velocity maximum of the radial outwash flow for the tandem rotor is larger. Moreover, the rotational direction of the tandem rotor leads to a wake with several vortical interactions resulting in different outwash on the port and starboard sides. Nomenclature b, f = edge lengths of the rectangular panel, m hxi, hyi, hzi = edge lengths of the integration cuboid, m

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“…A considerable amount of prior work has been performed to understand the vortical wakes produced by helicopter rotors [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The majority of this research has primarily focused on characterizing the rotor wake and the dominant blade tip vortices [15][16][17][18][19][20][21][22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%