Would a Plane with Golf Ball-Like Dimples Fly Better?

The idea of adding dimples to an airplane wing may seem novel, but it requires a deep understanding of aerodynamics to determine its actual effectiveness. While dimples on a golf ball can reduce drag and improve performance, their application on an aircraft is more nuanced and context-specific.

Why Dimples Work on Golf Balls

Dimples on a golf ball can indeed reduce drag, a phenomenon that can be explained by the transition of airflow over the ball's surface. As golf balls fly through the air, the dimples disrupt the smooth flow of air around the ball, creating a series of vortices that help to smooth out the trailing edge of the airflow. This means that the air does not separate as quickly from the surface of the ball, resulting in less drag.

Drag in Aircraft

Aircraft are designed with smooth, streamlined surfaces to minimize drag, which is crucial for long-distance flight. To reduce drag, the overall shape of the aircraft is optimized, and small irregularities, if present, are typically detrimental. Adding dimples or turbulators to an aircraft wing could potentially disrupt this streamlined design, leading to increased drag.

The Role of Reynolds Number

The challenge in applying golf ball dimples to aircraft lies in the Reynolds number, which changes with flight speed. At low speeds, such as those in takeoff and landing, the Reynolds number is lower, and dimples can help reduce drag. However, at higher speeds, such as cruising, the Reynolds number is much higher, and dimples can actually increase drag. Therefore, dimpling an aircraft wing may only be beneficial in certain flight conditions.

Alternative Airdrag Reduction Strategies

Instead of adding dimples, aircraft designers focus on maintaining a streamlined shape to reduce drag at all speeds. Turbulence can be managed through various devices called turbulators, but these are typically used in specific areas where drag is more problematic, like the blades of wind turbines. In aircraft, such measures are less common due to the already streamlined design.

The Importance of Streamlining

Airplanes are inherently streamlined to optimize their flight characteristics. Dimples can negatively impact this streamlined design, potentially causing turbulence that leads to higher drag. Airflow over a smooth wing surface is crucial for lift and stability. Any disruption, such as the ones caused by dimples, can interfere with these critical functions.

The Magnus Effect and Its Limitations

One of the mechanisms by which dimples might offer benefits is through the Magnus effect. The Magnus effect is the phenomenon where an object spinning through the air experiences a force perpendicular to both the spin axis and the direction of travel. While dimples can create turbulence and reduce pressure drag, they are not a substitute for optimized aerodynamics.

Relevant types of drag are base drag and skin friction drag. Base drag is the drag created when airflow separates from the body, creating a low pressure area behind the body. Skin friction drag is the drag generated by the air rubbing against the body. Dimples can reduce skin friction drag, but this effect is outweighed by the increased base drag in most flight conditions.

Conclusion

While dimpled golf balls exhibit a reduction in drag due to the unique flow characteristics of a spherical object, the same cannot be said for aircraft. Adding dimples to an aircraft wing can actually increase drag under many conditions, undermining the aircraft's overall performance. The best approach remains the optimization of the aircraft's sleek, streamlined design to minimize drag across all flight speeds.

Acknowledgments

A special thanks to the MythBusters for their insightful experimentation and to the aeronautical community for their ongoing research into aerodynamics and aircraft design.