Coherent structures over flat sandy surfaces in aeolian environment

- Coherent structures in aeolian environments can be captured by PIV and POD.
- Streamwise, elongated, low- and high-speed streaks over sandy beds were identified.
- Saltating grains seem to influence the scale and direction of coherent structures.

A basic assumption in many theoretical models of aeolian sediment transport is that airflow is uniform. In fact, turbulence is structural, and there exist extremely complex dynamic behaviors. Coherent structures are probably most important features. Nowadays aeolian researchers are generally aware of the significance of coherent structures, although even their basic forms have not been revealed completely. In the current research, the wind tunnel experiment with the help of the particle image velocimetry (PIV) technique and the proper orthogonal decomposition (POD) method shows that there are streamwise, elongated, low- and high-speed, streaks-type coherent structures over sandy surfaces with and without saltation in aeolian environment.