How do streamlines/flow look like on single surface wing of hang gliders, especialy on the lower side? Has anyone installed tufts or done CFD analysis on this?
The lower side isn't the one that stalls, but circulation of air underneath a thin undercambered wing may be of interest.
Thin undercambered wings go back to the earliest days of aviation, providing the most lift at low airspeeds.
Analysis of the flow underneath may show a bit of circulation up and into the underside, providing a bit of drag energy recovery in addition the the lift from higher (ram) pressure underneath the wing.
Full scale hang gliders have sufficient Reynolds numbers to also generate "top lift", which is lost in stall. This is why "tufts" are usually placed there for study.