Görtler vortices

If the boundary layer is thin compared to the radius of curvature of the wall, the pressure remains constant across the boundary layer.

On the other hand, if the boundary layer thickness is comparable to the radius of curvature, the centrifugal action creates a pressure variation across the boundary layer.

These phenomena are named after mathematician Henry Görtler [de].

It is the ratio of centrifugal effects to the viscous effects in the boundary layer and is defined as where Görtler instability occurs when G exceeds about 0.3.

A similar phenomenon arising from the same centrifugal action is sometimes observed in rotational flows which do not follow a curved wall, such as the rib vortices seen in the wakes of cylinders[1] and generated behind moving structures.