Shear flow

For thin-walled profiles, such as that through a beam or semi-monocoque structure, the shear stress distribution through the thickness can be neglected.

[1] This corresponds to units of newtons per meter in the SI system and pound-force per foot in the US.

[2] The concept of shear flow is particularly useful when analyzing semi-monocoque structures, which can be idealized using the skin-stringer model.

In this model, the longitudinal members, or stringers, carry only axial stress, while the skin or web resists the externally applied torsion and shear force.

Here, the strain rate is simply the relative velocity divided by the distance between the plates.

For example, when two layers of fluid shear against each other with relative velocity, the Kelvin–Helmholtz instability may occur.

Example of Skin Stringer Model with Shear Flow
Shear-flow vortices form as ethanol is injected into a viscous glycerol medium from the right side, and streams along the arched boundary of an air cavity . (Note, the small circular air cavity is not in the flow path.)