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  • 1
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    Euler solutions for the flow around a hovering helicopter rotor (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A method for computing the flow around a hovering helicopter rotor is presented. The solution procedure is divided into two parts. The first part is a finite volume solution of the Euler equations for the near field flow around a rotor blade. The second part is a free wake approach for determining the wake geometry and induced velocities. These two parts are solved in a coupled fashion. The rolled-up vortex wake of the rotor is included in the Euler computational domain through a nonlinear perturbation technique. This eliminates the numerical diffusion of the wake vorticity due to truncation error and artificial viscosity without the need for excessive grid resolution near the vortex core. The method is used to compute both hovering rotor and wing/vortex interaction flows, and the results are compared to experiment.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 86-1784
    Format: text
    Location Call Number Expected Availability
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    NASA TECHNICAL REPORTS
  • 2
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    Solution method for a hovering helicopter rotor using the Euler equations (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A method for the calculation of the flow field of a helicopter rotor blade in hover is presented. The approach uses a finite volume solution of the three dimensional Euler equations for the blade near field. In the Euler solver the velocity field is decomposed into two parts. One is the induced velocity of the vortex wake extending below the blade, found from a free wake calculation procedure. The other part is the unknown additional velocity field of the rotor blade. This approach eliminates numerical diffusion of the rolled up wake vorticity due to truncation error and artificial viscosity. Also, the effects of the far wake are included in the limited computational domain. Solutions are presented for an isolated wing and a model helicopter rotor and compared to experiment.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 85-0436
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    A computational method for helicopter vortex wakes (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A method for calculating the wake geometry and blade loads for a hovering helicopter rotor is presented. The approach incorporates a simplified free wake model of the rotor in a finite difference calculation of the flow field. A variation of the 'cloud-in-cell' technique, modified to eliminate self-induced velocity errors for curved vortex filaments, is used. Simple lifting line theory is used to calculate the blade loads. Calculations showing the effect of vortex core size and the number of vortex filaments representing the wake are presented. For large numbers of vortices, it is seen that the wake geometry fails to converge. However, only a few vortices are needed to adequately represent the wake. Comparisons with experimental results are also presented.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 84-1554
    Format: text
    Location Call Number Expected Availability
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    NASA TECHNICAL REPORTS
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