Descending Into Liquid

June 12, 2019

When you dive into water, it cushions you and absorbs your energy.  Your body pushes water out of your path and energy is transferred to water in the form of waves.  You generate waves, slowing and descending deeper until your energy dissipates.  Descent into liquid is only possible, when water has time to move out of your way. 

 

 

 

 

 

 

 

 

Should you fall into water from a ledge several hundred feet high, you will hit water carrying great speed.  Water cannot move out of your way in time to allow penetration.  You will momentarily stop on the surface, blocked by water until you decelerate.  Water can not absorb your impact, instead your body takes the crushing blow.  Depending on how you land, you may sustain injuries. 

 

 

 

 

 

 

 

 

 

 

 

 

 

In a high fall, water supports you briefly, on the surface with hydrodynamic resistance.  Water cannot compress due the inter molecular bond of hydrogen atoms. There is no space for molecules to compress.  Water becomes more like earth to speeding objects.

 

 

After a hard numbing collision with water, your body penetrates and decelerates. The collision possibly compressed your neck and vertebrate, this will hurt later.  Your tissues and organs also took a jolting blow, when the water's surface did not give in.  You probably feel a bit dizzy from a numbing bump to your head.  As you come to your senses, you yearn and crave air, as your lungs compressed.  Just when things start to calm, there is a roar and a thundering explosion.  The wave breaks on you with a brutal and violent force that compresses your sinuses and ears.  They feel like they will burst.   Water twists and bends your body into unimaginable shapes.  You experienced the forces of hydrodynamic resistance.  Hydrodynamic forces bend and twist your body as you are propelled through water by the wave's energy.

 

 

 

 

 

 

 

 

 

 

 

 

Andrew Cotton lands hard and breaks his back in the following video

 

 

 

 

 

An object with speed cannot displace water, instead water supports speeding objects on the surface, with Hydrodynamic lift. Hydrodynamic lift propels surfers on waves.  Speed generates lift and surfers ride on the water's surface hydro-dynamically. 

 

A long standing belief is that nose rocker prevents pearls and nose pokes.  This is true at low speed when water can be pushed aside.   At high speed the flat underside of the nose bend is exposed to impact.  The bend produces an appendage that curves upward.  Impact on this appendage, generates resistance much like a body falling into water from great heights.  Like a crushing body blow on water, the surfboard momentarily stops on the surface before submerging deeper.  A rider is catapulted, by the abrupt change in speed,.  The wipe out is called a pearl dive or nose poke.  The combined pressure generated by the surfer's weight and impact force from speed, on the bent appendage, is momentarily blocked by water.  Instead of preventing these wipe outs, too much nose rocker can enhance them.  Water generates more pressure or lift than the combined force and weight of the speeding surfer, proven in Bernoulli's Principle.

 

Skill is an important factor in maintaining control. Pros are skilled at keeping the nose from impacting water. Only when they lose control is this a factor.  For normal surfers a round or vee nose bottom with moderate nose rocker will ride out of a shallow dive.  Skill and wave conditions dictate rocker and bottom shape for each individual surfer.  It is not likely that such a board will come from China.

 

 

 

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