Category: Observing Water

The wake

Wake spreading after duck
Wild Duck (Mallard) swimming across a water surface, generating a wake behind it. Small waves can be seen capturing up with the main wake, overtaking it, and then dissolving as they advance ahead and loose their energy. Söderåsen National Park, Sweden.
Photo: Lasse Johansson

Quietly, the duck swims across the water surface, its legs paddling silently underneath. Behind it, a small wake spreads distinctly, disturbing the otherwise completely still water surface. The sun is setting over the little lake – the oblique light causes the ripples to stand out, bringing them to my attention. Here at the outlet, just above a small dam, pieces of pond weed come drifting in an almost invisible current, and the duck hunts for food. Continue reading The wake

The artist’s water

The undulating water mirror
Reflections in an undulating water surface, stretching in the vertical direction. Slussen, Orust island, at the west coast of Sweden.
Photos and illustrations: Lasse Johansson

Like a painting, the water surface shimmers. Its low undulating forms, just slightly curved, one in front of another, has been shaped by the wind or a passing boat, and the water surface comes to life. Like the memory filtering an artist’s impression, the water surface has its own way of filtering our impressions, the image of the land reflected across the bay appears fuzzy and smeared out. Continue reading The artist’s water

The fish and the propeller

Karman vortex street - fully developed
Kármán vortex street, generated by a paddle and captured on paper with dye. The inrolling motion, clockwise at left, counter-clockwise at right, has developed more fully, and the alternating vortexes are clearly discernible. Paddle movement is downwards. From a workshop with Nigel Wells. Archives of Institute of Ecological Technology.

Flip, flap, flip, flap, the tail fin of the trout swishes to and fro, thrusting the fish forward in the still water. Silently it speeds away under the surface. Seemingly without effort it moves, leaving a series of wakes behind. As a contrast, our propeller thrusts water backwards indiscriminately, creating a white foam of turbulent water behind the boat. How can the fish swim so fast and elegant, almost effortlessly? Continue reading The fish and the propeller

The water jet dances

The dancing water jet
As the up-going flow bumps into the down-going, it starts to twist and bend. Botanical garden, Gothenburg, Sweden. Photo(s): Lasse Johansson

The jet of water ejects out of the nozzle in a continuous, steady flow. Directing my eyes towards the opening, there is not a trace of pulsation.

Yet just slightly above, the dance has begun. As the upward movement is gradually lost, the water jet starts to twist and bend, like a rubber band being pushed.

Then it turns around and sweeps down, now on this side, now on that, now hitting the up going flow and, for a moment, almost extinguishing it, and then it moves on again, unpredictable. Never at rest, oscillating, yet not repeating itself – its aperiodic undulations never reveal what is next to come. Continue reading The water jet dances

Ink droplets falling in water

Umbrella shaped ink droplet
Slowly sinking umbrella shaped ink droplet, like a primitive octopus. Photo(s): Lasse Johansson

Water’s inherent tendency to form patterns can be observed as simple as with ink droplets falling into water (preferably in a container with flat walls). The impact of the droplet creates vaulting toroidal forms, vortexes resembling jellyfish, and finally, when the motion slows down, settles into sinking octopus-like forms.

Studying and looking at the flow patterns can be really captivating. I once tried this experiment with children in kindergarten, who were amazed, and would stand dripping ink into the water for more than half an hour. Continue reading Ink droplets falling in water