What is the term for airflow from two adjacent surfaces that merge and create turbulence?

The concept of turbulence created by the merging of airflow from two adjacent surfaces is best captured by the term "interference drag." This type of drag arises when the airflow around one surface affects the airflow around another adjacent surface, leading to disruptions in the smooth flow of air. When these airflows blend, or interfere with one another, they create additional resistance in the form of turbulence. This disruption typically results in increased drag compared to what would be encountered if the surfaces were isolated from each other.

Interference drag is particularly significant in the design of aircraft, where multiple surfaces, such as wings and fuselage, interact. Understanding this effect is crucial for aerodynamic efficiency, as it helps engineers optimize the shape and arrangement of these surfaces to minimize drag.

In contrast, form drag relates to the shape of an object and the resistance caused by the shape itself as it moves through the air. Skin friction drag is associated with the friction between air and the surface of the object. Profile drag is a broader term that encompasses both form drag and skin friction drag, but it does not specifically address the merging of airflow from adjacent surfaces. This is why interference drag is the most accurate term for the scenario described.