Surfzone dye and drones

Waves, wind and tides all influence the water motion near the beach. Although we know a lot about what drives coastal currents, we can still be amazed by how complex the flow can be in a real life situation.

This week we did experiments with green dye (don't worry, it's environmental friendly!) to get a top view of the flow pattern. The green dye is released in small patches, which is then transported and mixed by the flow.

To follow the dye movement we use small drones (UAVs) to take aerial pictures. We have to specialists at the experiment right now that can make great pictures of the beach as their drones fly about 100 m above the Sand Engine and are equipped with small GoPro Camera's. 

A few snapshots of one dye deployment are shown below:

Two small patches of dye at the start of the experiment. One offshore of the bar, and one inshore of the bar. 

after 6 minutes

after 12 minutes

After 18 minutes

And after 28 minutes

These pictured give an impression on how fluid can mix material floating in the water (swimmers, sand, oil etc.) and redistribute this matter along the coast. 

Images from Ronald Brouwer (Delft University of Technology) and Patrick Rynne (University of Miami/Waterlust)

NB.. Note the small white line in the offshore region. That's probably the edge of the fresh water from the river and the salt sea water. Pretty cool!