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Foundation ::
Aerodynamics Applications ::
VLMD
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VLMD
Vortex-Lattice Code for Determination of Mean Camber Surface for Trimmed Noncoplaner Planforms with Minimum Vortex Drag
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SOURCE CODE AVAILABLE
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VLMD represents a subsonic aerodynamic method for determining the mean camber surface of trimmed noncoplaner planforms with minimum vortex drag.
With
this program, multiple surfaces can be designed together to yield a trimmed configuration with minimum induced drag at some specified lift coefficient. The method uses
a vortex-lattice and overcomes previous difficulties with chord loading specification. A Trefftz plane analysis is used to determine the optimum span loading for
minimum drag. The program then solves for the mean camber surface of the wing associated with this loading. Pitching-moment or root-bending-moment constraints can
be employed at the design lift coefficient. Sensitivity studies of vortexlattice arrangements have been made with this program and comparisons with other theories show
generally good agreement.
The program is very versatile and has been applied to isolated wings, wing-canard configurations, a tandem wing, and a wing-winglet
configuration.
The design problem solved with this code is essentially an optimization one. A subsonic vortex-lattice is used to determine the span load distribution(s) on bent lifting
line(s) in the Trefftz plane. A Lagrange multiplier technique determines the required loading which is used to calculate the mean camber slopes, which are then integrated
to yield the local elevation surface.
The problem of determining the necessary circulation matrix is simplified by having the chordwise shape of the bound circulation
remain unchanged across each span, though the chordwise shape may vary from one planform to another. The circulation matrix is obtained by calculating the spanwise
scaling of the chordwise shapes. A chordwise summation of the lift and pitching-moment is utilized in the Trefftz plane solution on the assumption that the trailing wake
does not roll up and that the general configuration has specifiable chord loading shapes.
VLMD carries the NASA case number LAR-15160. It was originally released as part of the COSMIC collection.
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