Wild Side: On the eddy line between turbulent fluids
by Dan Wildcox, outdoor columnist
Last Saturday was an end-of-summer day for us. The big travel lift at the Washburn Marina picked our old sailboat out of the water and set it on its steel cradle. The marina staff pressure-washed the bottom and parked the boat on land for the winter. Despite a cold gale from the northeast that turned Chequamegon Bay into a streaked gray sea of whitecaps, I was able to finish preparing the boat for the winter and install the canvas cover.
Monday, Sept. 30 was another end-of-summer day for me; the last day of the stream trout fishing season. I caught some nice brook trout in the Rush River including a spectacular 11-inch male in full spawning color. The fish were feeding in a run just over knee deep. It was hard to cast with a wind blowing upstream and bouncing off the cliff across the river.
What makes sailing and fly fishing so special to me goes beyond being in beautiful places. Sailing a boat and fly casting are both fascinating activities involving being in the interface between the turbulent fluids of air and water. Both require intent observation and sensing what is happening above and below.
Sailing takes some practice, mainly to become attuned to the wind and waves. Wind speed and direction are constantly changing. Wind may veer (move in a clockwise direction) and back, oscillating over 20 degrees of direction.
Friction of the air on the water surface creates wind-driven waves that range from vague ripples to dangerous breaking waves. Watching the water surface upwind gives advance notice of gusts and changes in wind direction. Keeping a sailboat moving in light air is nearly as challenging as blasting along reefed down in heavy wind and waves.
When fly fishing on a river, the line propels the leader and fly toward the intended target but is vulnerable to the vagaries of wind and waving tree branches. To present a fly that effectively imitates a drifting insect involves accurately placing the cast and dealing with the line and river current to avoid dragging the fly. It takes lots of observation and practice to get to know the flow lines in rivers.
It doesn’t take an engineering degree in fluid dynamics to appreciate the different scales of turbulence and interactions between the air and water. The play of light and sound at the air-water interface is mesmerizing. That’s a big reason why we are attracted to lakes, rivers and oceans. Rivers run through us; the turbulent flow of air and water is in us.
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