oktas8, can you expand a bit?
I've never heard that straight wing aircraft exibit spanwise flow. From the tip to the root? An effect of changing chord or wash out? With constant chord and camber, if anything I'd think fuselage effects produce a slight spanwise flow towards the tips. With of course any winglet limiting this.
And when you talk of spanwise flow on swept wings of sin(sweep angle), I presume you're implying the airflow continues to move in the same direction of the aircraft's longitudinal axis. But surely on most swept wing aircraft there must be some lateral movement of the air, especially at high aoa, and towards the tips.
Hawk