Eddystrukturer

Eddystrukturer, also known as vortex streets or von Kármán vortex streets, are a periodic alternating pattern of swirling vortices caused by the unsteady separation of flow of a fluid. This phenomenon occurs when a fluid, such as air or water, flows past a blunt obstacle. As the fluid moves around the obstacle, it separates from the surface, forming a wake. The separated flow then rolls up into discrete vortices that are shed alternately from opposite sides of the obstacle. This shedding creates a staggered, repeating pattern of vortices extending downstream from the object.

The formation of eddy structures is a common occurrence in fluid dynamics and can be observed in various natural and engineered systems. Examples include the wake behind a bridge pier in a river, the airflow around an airplane wing at high angles of attack, or the smoke rising from a chimney. The regularity of the vortex shedding depends on factors such as the speed of the fluid, the shape and size of the obstacle, and the properties of the fluid itself, like its viscosity.

The presence of eddy structures can have significant implications. In engineering, they can lead to vibrations in structures due to the fluctuating forces exerted by the shedding vortices. This phenomenon is known as vortex-induced vibration and is a critical consideration in the design of bridges, buildings, and offshore platforms. Understanding and predicting the formation and behavior of eddy structures is therefore important for ensuring the safety and efficiency of many technological applications. The characteristic frequency of vortex shedding is often related to the Strouhal number, a dimensionless parameter that helps characterize the unsteady flow.