Swimming to Success

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.