Modelling wind ripples
Here, I try to simulate the patterns obtained on a sandy terrain. This is what is observed when the wind blows on the dry surface of a land with sand or also on the surface of the sea in the presence of currents.
As described in https://en.wikipedia.org/wiki/Dune,
When a sandy seabed is subject to wave action and the wave orbital motion is strong enough to move sand grains, ripples often appear. The ripples induced by wave action are called “wave ripples”; their characteristics being different from those of the ripples generated by steady flows. The most striking difference between wave ripple fields and current ripple fields is the regularity of the former. Indeed, regular long-crested wave ripple fields are often observed on tidal beaches from which the sea has withdrawn at low water (see figure 1).
A nice example is shown in http://www.coastalwiki.org/wiki/Wave_ripple_formation showing
Ripples observed at Sea Rim State Park, along the coast of east Texas close to the border with Louisiana (courtesy by Zoltan Sylvester).
An interesting aspect of that patterns is that they may occur at different scales, like taht example on the surface of the Mars planet:
Overview of large sand wave field and high-resolution difference map of two surveys approximately 21 hours apart illustrating both large-scale and small-scale sand wave migration and orientation. Migration is from right to left.