Observations of collisions of saltating grains with a granular bed from high-speed cine-film



High-speed photography was used to record saltating sand grains colliding with a horizontal, noncohesive bed of similarly sized grains. Impacting grain/bed interaction is discussed in general. The process, as observed from the films, is then described in terms of the apparent bed contact length (ABCL) and various parameters of the impacting grains and any ejected grains. Examples are given of typical behaviour of bed grains in response to impacting grains of different sizes. Saltating grains that are large in comparison to the bed grains they encounter at collision can churn up the surface layers of soils and sediments, so that previously buried grains become available for entrainment. This process is discussed in relation to the potential release of dust particles into the airflow.