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Wednesday, July 29, 2020 | History

3 edition of Viscous effects on a vortex wake in ground effect found in the catalog.

Viscous effects on a vortex wake in ground effect

Viscous effects on a vortex wake in ground effect

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  • 3 Currently reading

Published by Old Dominion University Research Foundation, Dept. of Mechanical Engineering & Mechanics, College of Engineering & Technology, Old Dominion University, National Aeronautics and Space Administration, National Technical Information Service, distributor in Norfolk, Va, [Washington, DC, Springfield, Va.? .
Written in English

    Subjects:
  • Wakes (Fluid dynamics)

  • Edition Notes

    Statementby Z. Zheng and Robert L. Ash.
    SeriesNASA-CR -- 190400., NASA contractor report -- NASA CR-190400.
    ContributionsAsh, Robert L., United States. National Aeronautics and Space Administration.
    The Physical Object
    FormatMicroform
    Pagination1 v.
    ID Numbers
    Open LibraryOL14684457M

    the obstacle is larger than 3R, the effect of the obstacle is small. Keywords Rotor wake Flow field Ground obstacle Vortex particle method Viscous boundary model List of symbols b, f Size of the rectangular panel (m) h xi,h yi,h zi Size of the integration cuboid . Furthermore at higher advance coefficients, a weaker wake and tip vortex, reduce the cross-interaction resulting in a more stable helical vortex system as observed in incipient cavitation flow visualization (Stella et al ) REFERENCES Stella, A., Guj, G: Di Felice, F., Elefante, M. â Propeller wake analysis by LDV and Flow Visualitationsâ.

    Space Systems Engineering/ Mars Exploration / Wright Brothers' Flyers / Airplane Wake Hazards / Extraterrestrial Resources/Non-equilibrium and High-speed Flow Phenomena; Research Interests Vortical flows, non-equilibrium phenomena, space systems, Mars resources R. L. "Vortex Wake Modeling" $, - Ash, R. L. "Advanced Space. The detailed experimental visualizations of the wake of an isolated fan in GE [12], for example, show that the highly viscous interactions of the rotor wake with the ground greatly affect the flow characteristics and the velocity profiles at the proximity to the ground. These detailed flow studies have.

    An aerodynamic method of the rotor in ground effect is then established by coupling the ground aerodynamic model with an unsteady panel/viscous vortex particle hybrid method in which the unsteady aerodynamics of rotor and unsteady behavior of the rotor wake are taken into account. The existing theory for vortex formation (Nagata ()) suggests that impeller Froude number adequately characterizes the vortex depth when viscous effects are minor. In the present work, we first show that at the L scale, the scaling with Froude number fails when viscous effects are significant.


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Viscous effects on a vortex wake in ground effect Download PDF EPUB FB2

Get this from a library. Viscous effects on a vortex wake in ground effect. [Z Zheng; Robert L Ash; United States. National Aeronautics and Space Administration.]. Simulation of Wake Vortex Aircraft in Ground Effect. The book goes into some detail on the more recent developments that attempt to account for viscous effects, in particular the presence of.

A vortex-based approach is employed to predict the 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 Cited by: 1.

Instead, concerning the axial position of the tip vortex, for h g / R = ground effects are significant only when the wake is in proximity to the ground, where its axial velocity tends to become negligible, whereas for h g / R = the axial velocity of the tip vortex is significantly reduced by the ground presence since the beginning of Author: Claudio Pasquali, Jacopo Serafini, Giovanni Bernardini, Joseph Milluzzo, Massimo Gennaretti.

Towing-tank experiments were conducted to investigate ground effects on vortex wakes. Two methods were used to generate the vortex wakes: 1) a towed NACA wing and 2) a slotted-jet vortex.

The vertical anemometer array showed that the crosswind profile under a wake vortex in ground effect has a very thin boundary layer, much thinner than that of the ambient wind. Due to viscous effects in the near wall region, adding to the complexity of the flow, the resulting vortex system can deviate substantially from the classical expected ideal flow monopole generated at the vortex generator tip.

From more recent theory and previous experience, the wake was instead expected to contain a basic vortex system. A vortex-based approach is employed to predict the 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.

Comparison to wake predictions out of ground effect indicates that in ground effect (i) the rapid-decay phase progresses slower, (ii) wake vortex evolution can be predicted with improved accuracy.

A fast-time model for wake vortex behavior prediction in ground proximity is presented. This model takes into account the combined effects of ground proximity and wind (both crosswind and headwind components) on the wake vortex transport and decay.

It aims to mimic the whole flow using a limited set of vortex particles to model both the primary two-vortex system and the ground-generated. 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. The authors have been involved in a systematic study concerned with including viscous effects in a wake-vortex system which is near the ground plane. The study has employed numerical solutions to the Navier-Stokes equations, as well as perturbation techniques to study ground coupling with a descending vortex.

The effect of viscous drag and vortex decay. Besides the SV, there are several other physical ingredients which might affect the evolution of the co-rotating vortex in ground effect, such as vortex decay, viscous drag, temperature stratification, cross-wind, etc.

Due to the fact that there are certain difficulties in demonstrating the. "Vortex Wake and Exhaust Plume Interaction, Including Ground Effect" (). Doctor of Philosophy (PhD), dissertation, Aerospace Engineering, Old Dominion University, DOI: /k4vq   Alexander and Vogel () suggest that the Wagner effect is magnified at low Reynolds numbers (where viscous effects dominate over inertial effects).

However, some results contradict this statement. The experiments of Dickinson and Gotz () at Re=10–10 3 show little evidence of Wagner’s effect.

For the first one-chord-length of travel. Leishman studied the ground effect on helicopter wake using a filament based method, where a mirrored wake solution was used to simulate the ground plane.

Leishman solves the free-wake viscous effects to the vortex core using a simple diffusion model as10, The motion of two-dimensional vortex pairs in a ground effect - Volume 82 Issue 4 - Steven J. Barker, Steven C. Crow Skip to main content Accessibility help We use cookies to distinguish you from other users and to provide you with a better experience on our websites.

The model was mounted in proximity to a ground plane initially located H above the model as depicted in Fig. ground clearance is the identical to that used by Parkin et al.

and slightly higher than the H utilised by Grandemange et addition to this, ground clearances of 0H, H and H were also tested in limited quantities, with the last of these approximating the away. Conversely, tilting the nacelle toward the ground directs the wake into the turbine mast and ground, resulting in a "crashing" wake with a lower velocity deficit.

The high-speed, undisturbed flow above the wind farm is shifted in response to θ = 15 °, obstructing the flow, while θ = − 15 ° draws the high-speed flow into the wind plant. Close Drawer Menu Close Drawer Menu Menu.

Home; Journals. AIAA Journal; Journal of Aerospace Information Systems; Journal of Air Transportation; Journal of Aircraft; Journal of. Viscous Effects on a Vortex Wake in Ground Effect by Z. Zheng* and R. L.

Ash t Abstract Wake vortex trajectories and strengths are altered radically by interactions with the ground plane. Prediction of vortex strength and location is especially important in the vicinity of airports.For the ground effect, the wake vortex generated by a fixed ground boundary condition is closer to the ground, while the wake vortex generated by a moving ground boundary tends to break away from the ground as the wake gradually develops backward (Zhang et al., ).

The dominant frequency of vortex shedding on the fixed ground is much higher.Aircraft wakes represent potential hazards which can control aircraft spacing and thus limit airport capacity. Wake vortex trajectories and strengths are altered radically by interactions with the ground plane and by atmospheric conditions.

This work has been concerned with developing more accurate numerical predictions. A two-dimensional, unsteady numerical-theoretical study is presented.