Periods of high downstream and cross-stream transport were selected for detailed manual particle tracking analysis at distances 25 cm, 55 cm, and 115 cm downstream of the backstep (flow reattachment occurred at ~18cm). Particle tracking of high transport events was conducted using the MTrackJ plugin for ImageJ. For each high transport event, ~250-500 grains were tracked from initiation of movement to completion of movement/exiting the field of view. Length of transport, average and instantaneous particle velocity, and average and instantaneous direction of particle transport were recorded for each grain.

These videos show a distinct change in the pattern of transport caused by flow reattachment. Near flow reattachment, cross-stream transport is occurring at comparable magnitudes to downstream transport. Further downstream of flow-reattchment, the dominant direction of transport is downstream.

 


 

All images and text on this site © 2016 Kate Leary