Flow to tip
I remember reading that the spanwise flow moves in the direction of the tip due to the rearward sweep.Part of the airflow continues over the wing and some is influenced by the sweep to move in the direction of the tip along/just behind the leading edge area(think its called rams horn).This is one of the problems at low speed,causing a reduction in the lift from a swept wing and high AoA on approach.Hence wing fences ect.