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Implementations of lifting-line theory predict the lift of a finite wing using a sheet of semi-infinite vortices extending from a vortex filament placed along the locus of aerodynamic centers of the wing. Prandtl's classical implementation is restricted to straight wings in flows without sideslip. In this work, it is shown that lifting-line theory can be extended to swept wings if, at the control points where induced velocity is calculated, the second derivative of the locus of aerodynamic centers is zero and the trailing vortices are perpendicular to the locus of aerodynamic centers. Therefore, a general implementation of lifting-line theory is presented that conditionally forces the second derivative of the locus of aerodynamic centers to zero at each control point and joints each trailing vortex such that there is a finite segment of the trailing vortex that lies perpendicular to the locus of aerodynamic centers. Consideration is given to modeling the locus of aerodynamic centers and section aerodynamic properties of swept wings. The resulting general formulation is analyzed to determine its sensitivity to closure parameters, accuracy, and numerical convergence.

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A significant factor which affects the accurate prediction of the discharge coefficients of square edged orifice plates is the precise shape of the edge. A rounding of only 0·002 of the orifice diameter can increase the coefficient by 1% so that a reliable method of assessing the edge sharpness is of considerable benefit to the instrument engineer. In the work described in this paper, a systematic intercomparison of three methods of measuring orifice edge sharpness has been undertaken. The methods tested involved casting, lead foil impression and optical techniques, and their relative reliability and effectiveness has been assessed. While the results obtained from the casting and lead foil methods showed good agreement, the foils did not follow the edge profiles as closely as the castings. The casting procedure can also be used to determine the shapes of re-entrant profiles which will not be detected using lead foil impressions. However, the casting method required more skill and considerably more time to complete measurements than the impression method. The optical method proved to be the least reliable, since measurements depended on subjective judgment. Nevertheless, this measuring procedure could be completed more quickly than the others, and these tests indicated that it may be used to examine large diameter plates for burrs or excessive rounding.