Hi!:)i want to know how sandripples happen?what make it happen?I need your answer! thanks alot:confused:confused:

The threshold wind speed for moving dry sand grains, about 24 kph (13 knots), is the minimum required to develop sand ripples. Prevailing wind direction is generally transverse to the long dimensions of the ripples, but perturbations of wind currents due to local slopes commonly produce local variations within a ripple field.

Water flowing or wind blowing across sand.
Ber

Yea.
The ripple patterns under shallow water are the most inersting ones.
If you look physiclly at this problem, you'll recoginze that this has to do with the Frouds Number, and also the Reynolds Number...