August 2016, Amsterdam
The video below demonstrates how aggregate formation in lake water can be simulated in the lab using a Couette flocculator. As you can see in the movie, aggregates appear in initially clear water.
The outer wall of the flocculator rotates at a constant angular velocity. The inner cilinder does not rotate; it is fixed. As a results, a laminar flow of water is created inside the cilinder. Suspended particles in this laminar flow will collide with a certain probability. Some colliding particles will stick together, others will break. Over time, the average size of suspended particles will grow - as is the case in this movie - or will become smaller, until an equilibrium size has been reached.
This method contributed to experiments that I have performed as part of my second MSc thesis. Amongst other purposes, it was used to restore aggregates that were potentially damaged as a result of aggregate sampling (in the field) and/or aggregate transportation (to the lab). An interactive 3D visualisation of an aggregate, restored using this technique, is presented on this website. It was also presented by way of a poster presentation at the ISME16 conference in Montreal, Canada.