Thread: Underwater vortex photos

I have seen this phenom in a movie and recently a photographer posted a couple underwater photos from Hawaii where you can see what looks like little tornadoes behind the curl of a wave.
When I asked him what they were, he responded with this: "I have no idea what you call those things or what they are. All I know is they have something to do with the turbulence under the water, after the lip penetrates. They're fun to shoot, but you almost have to develop a sixth sense about where the lip will be touching down, because you're underwater. Here's another one from yesterday..."

Here's the 2 photos.


Thanks for your help.

I really am interested in understanding this and will continue to check back to see if anyone has ANY comments.

not even sure what i'm looking at - is it air trapped in a breaker, or air/foam being dragged into the water ? or something else altogether ?

It is airflow being sucked into and under the advancing wave. Just as air is sucked into a rapidly draining sink drain due to the vast difference in viscosity between air and water forming a vortex. Rotation is due to the pressure difference and the resulting centripetal forces. The water and air is drawn in, under, and behind the advancing wave as the amplitude builds near shore and the shallow water starves the wave of the normal water volume available at greater depths. This reduction in cross sectional area for counter-flow (required to build wave amplitude, based on wave energy physics) causes the water velocity to peak right as the wave crests. This is where the vortexes would form.

Originally Posted by cypress

It is airflow being sucked into and under the advancing wave. Just as air is sucked into a rapidly draining sink drain due to the vast difference in viscosity between air and water forming a vortex. Rotation is due to the pressure difference and the resulting centripetal forces. The water and air is drawn in, under, and behind the advancing wave as the amplitude builds near shore and the shallow water starves the wave of the normal water volume available at greater depths. This reduction in cross sectional area for counter-flow (required to build wave amplitude, based on wave energy physics) causes the water velocity to peak right as the wave crests. This is where the vortexes would fom.

Wow,
Thanks for taking the time to explain that process to me. I can't say that I totally understood what you said but I think I get the jest of it.

Originally Posted by cypress

It is airflow being sucked into and under the advancing wave. Just as air is sucked into a rapidly draining sink drain due to the vast difference in viscosity between air and water forming a vortex. Rotation is due to the pressure difference and the resulting centripetal forces. The water and air is drawn in, under, and behind the advancing wave as the amplitude builds near shore and the shallow water starves the wave of the normal water volume available at greater depths. This reduction in cross sectional area for counter-flow (required to build wave amplitude, based on wave energy physics) causes the water velocity to peak right as the wave crests. This is where the vortexes would form.

Woo.

'Course it is my nature to flip everything upside down. So after reading that awesome explanation I wonder if one could say the air is trailing behind, not sucked under. So rather than sink drain dragging air through space I see the temporal wake of an advancing boat's propeller. Just another way of looking at it.

A vortex is a spinning, often turbulent, flow of fluid. Any spiral motion with closed streamlines is vortex flow. The motion of the fluid swirling rapidly around a center is called a vortex. The speed and rate of rotation of the fluid in a free (irrotational) vortex are greatest at the center, and decrease progressively with distance from the center, whereas the speed of a forced (rotational) vortex is zero at the center and increases proportional to the distance from the center. Both types of vortices exhibit a pressure minimum at the center, though the pressure minimum in a free vortex is much lower.

photo may be a Whirlpool: a swirling body of water produced by ocean tides.