Reference 1 describes a numerical procedure for calculating the roll-up of the wake behind a wing of finite span, when the wake vorticity is assumed to occur within a layer of finite thickness with thin elliptic cross-section normal to the stream. The vorticity is assumed to be a function of spanwise position only (corresponding to a linear transverse velocity profile when the wake is thin), the process is treated as a two-dimensional unsteady one, as in the work of Westwater, Moore and others, and viscous and turbulence effects are ignored.

In Ref. 1 the technique was applied to the classical elliptic loading, to calculate the very early stages of the roll-up. In the present paper these calculations are extended to larger values of the dimensionless time t* and the results are seen to tally fairly well with those of Moore, which were obtained by using a point-vortex model. Similar calculations have also been carried out for a particular non-elliptic loading which was dealt with by Clements and Maull by a two-dimensional, point-vortex method. They gave this loading as an example of a distribution which produces two roll-up cores on each half span, with an induced drag only 10% greater than that of the elliptic loading having the same Ch. The results of the new calculations are presented here, and are seen to be similar to those of Ref. 4 in a general way, both qualitatively and quantitatively.