In recent years, swimming records have been broken and set at higher
standards with incredible frequency. This was highlighted during the 2012
Olympics in London. During these games, engineers went to several specific
efforts to improve the quality of the pool, making it faster. Swimming athletes
like Missy Franklin also combined physical advantages with improved swimming
techniques to reduce the frictional drag, pressure drag, and wave drag exerted
on the swimmers by the water. To improve racing velocity and increase the
chances of winning, a swimmer must overcome the dynamic fluid forces acting
against the swimmer’s movement in the water. Understanding biomechanics in
combination with advanced engineering in pool design has led to faster swimming
and improved competition.
The pool design for swimming at the 2012 Olympics was a significant
advancement making the pool easier to swim in at a faster pace than the pools
in previous Olympics. The efforts in improving the design of the pool were all
aimed at reducing the water turbulence created by the waves in the water made
by the swimmers. The first engineering change was to increase the depth of the
pool to 3 meters. This increased depth dissipates the effect of waves in the
vertical direction by creating enough distance between the swimmer and the
bottom of the pool that the waves do not rebound off the bottom and increase
the upward forces that create frictional drag acting on the underside of the
swimmer’s body.
The London pool was also designed with troughs along all four sides so
that the waves along the surface of the pool would be captured instead of
rebounding laterally at the swimmer. These troughs served the purpose of
absorbing the energy generated by the waves so that turbulence and the
corresponding increases in drag forces would be reduced throughout the pool.
This design served to reduce drag forces coming at the swimmers from all
directions on the surface; front, back, and both sides. The overall width of
the pool was increased to 25 meters and lane width was increased to 2.5 meters.
Both of these width increases served to further minimize the effects that
turbulence, caused by waves, had on increasing drag forces between individual
swimmers within the lanes and the sides of the pool. The lane lines separating
each swimmer’s lane were also designed to spin. This spinning motion of the
lane line served to absorb the waves’ energy so that it was reduced rather that
entering the adjoining lane. This prevented an increase in drag forces caused
by turbulence that would have happened if the waves from multiple swimmers met
at full force without the lines acting to reduce the turbulent flow existing
between the swimmers. Another subtle way of improving the quality of the pool
for swimming would be to increase the warmth of the water temperature. Warmer
temperatures, when compared with cooler temperatures in a fluid, tend to have lower
viscosity, thereby reducing the effects of drag forces. All of these
engineering improvements created an environment in the pool that reduced drag
forces, allowing the swimmers to reach faster velocities in the water.
The relative velocity of an object in the water is the difference
between the object’s velocity and the velocity of the water. In the case of
swimmers in a pool during competition, the velocity of the water is a result of
turbulence caused by the waves which in turn are created by the bodily
movements of the swimmers’ moving through the water. The more swimmers in the
pool and the faster velocities those swimmers are attempting to achieve, the
greater the increase will be in the fluid velocity of the water. As the fluid
velocity of the water increases so does the drag force effects on the swimmers.
In a sense, when the swimmers attempt to swim at faster velocities, they are making
it harder on themselves to overcome the drag forces and achieve faster relative
velocities to the water. One approach to counteract this during the London
Olympics was to leave the two outside lanes empty during the races. Fewer
swimmers in the pool decreased the overall turbulence within the pool,
resulting in a reduction in drag forces due to turbulent flow.
Body composition and body position of the individual swimmer within the
water may also contribute to improved swimming performance. Having longer limbs
would allow a swimmer to create greater torque forces when moving the arms
through the water, pushing more water behind the swimmer and thereby increasing
velocity. Perhaps the most important key to reducing fluid drag forces is to be
in what swimmers refer to as a streamlined body position. A streamline position
minimizes body contact with the water by keeping the body in as narrow a
position as possible relative to the direction of travel within the water. A
streamlined position would give an advantage to people whose physical builds
are taller, longer limbed, and have narrow body frame and shoulders. When
compared to a wider body frame, a narrower and slim frame would help reduce the
overall surface area exposed to the viscous or surface drag against the body in
the direction of travel. A narrower and straighter body position would also
have an increased laminar flow to counteract the drag forces acting backward on
the swimmer. This would be an effective way to reduce the drag forces,
providing that the swimmer did not reach too fast of a relative velocity that
the forward moving water molecules of the laminar flow moved away from the
swimmer’s body and further contributed to an increase in turbulent flow. If
this were to happen, the turbulent flow would create a vacuum in the water
immediately behind the swimmer and increase the overall force of form drag.
Water moving past the swimmer also creates a pressure drag as it moves
around the curves and contours of the body. This creates a pressure difference
between the head and feet. This difference pushes back against the swimmer,
slowing velocity. A wave drag also exists in front of the swimmer created by
water that gets pushed in front of the swimmer as a result of movement through
the water. Swimmers work hard to make the techniques of swimming motions as
efficient as possible by moving in such a way as to cause a maximal decrease in
drag forces while creating the fastest velocity possible with little energy
lost to overcoming the drag forces. This allows the swimmer to put as much
kinetic energy as possible into moving throughout the race distance in the
shortest time possible, rather than expending the majority of the energy in
overcoming the drag forces. The streamlined position of a swimmer helps to
reduce these combined drag forces, minimizing the effects of a decreased
velocity in the water.
Competitive swimmers wear skin-tight swimsuits in an effort to minimize
fluid drag forces by reducing the total surface area exposed to viscous drag.
Wearing loose-fitting swimsuits would increase the surface area of the
swimmer’s body; thereby increasing viscous drag and reducing velocity. Wearing
a tight swim suit made of smooth material may also help reduce drag. The
purpose of wearing a smooth swimsuit is to reduce the coefficient of drag so
that the friction that exists between the suit and the viscosity of the water
is lowered than the friction between the water and human skin. To further
encourage a reduction in drag forces, swimmers will often wear swim caps on the
heads and shave all exposed body hair in addition to wearing suits designed to
reduce friction and drag forces.
A high level of performance in swimming is dependent on the ability to
reduce drag forces on the swimmer so that the relative velocity of the swimmer
in the water may be as fast as possible. Often athletes only consider how to
train the body for better performance. Swimmers do this by training to maintain
a streamlined position in the water. However, it is clear that changes to the
swim suits as well as the design structure and environment of the pool can also
be manipulated to reduce drag forces, resulting in faster velocities of the
swimmers. Records may very well continue to fall.