Curvature Corrections to Improve the Accuracy of Free-Vortex Methods

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Curvature Corrections to Improve the Accuracy of Free-Vortex Methods

Govindarajan, B. M. / Leishman, J. G.

The accuracy of discretized induced velocity calculations using straight-line vortex segmentation has been examined using an induced velocity correction (curvature correction) based on a curved element with a thin core. The validity of the curvature correction has been evaluated for the prediction of helicopter rotor wakes using a free-vortex method. Numerical techniques were developed to incorporate the correction into the self-induced velocity calculations to improve the accuracy for a given discretization or to reduce the discretization for a required accuracy or computational cost. The correction was analyzed in detail to understand its validity based on its thin-core assumptions and to quantify the effect of the correction as it affects the evolution of the rotor wake. It is shown that, while the inclusion of the curvature correction can, in some cases, improve the accuracy of the induced velocity calculation for a given level of discretization, its applicability to helicopter wake problems is not guaranteed or universal.