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Wall shear stress expresses the retarding force (per unit area) from a wall in the layers of a fluid flowing next to the wall. It is defined as: ...
A typical timber shear wall consists of braced panels in the wall line, constructed using structural plywood sheathing, specific nailing at the edges, and supporting framing. A shear wall is an element of a structurally engineered system that is designed to resist in- plane lateral forces, typically wind and seismic loads.
For a Newtonian fluid wall, shear stress (τ w) can be related to shear rate by = ˙ where μ is the dynamic viscosity of the fluid. For non-Newtonian fluids, there are different constitutive laws depending on the fluid, which relates the stress tensor to the shear rate tensor.
The logarithmic law of the wall is a self similar solution for the mean velocity parallel to the wall, and is valid for flows at high Reynolds numbers — in an overlap region with approximately constant shear stress and far enough from the wall for (direct) viscous effects to be negligible: [3]
is the average shear stress, is the shear force applied to each section of the part, and is the area of the section. [1] Average shear stress can also be defined as the total force of as = This is only the average stress, actual stress distribution is not uniform.
is the wall shear stress, is the suction/injection velocity at the wall, is the displacement thickness and is the momentum thickness. Kármán–Pohlhausen Approximation is derived from this equation.
Shear velocity is linked to the Darcy friction factor by equating wall shear stress, giving: = where f D is the friction factor. [1] Shear velocity can also be defined in terms of the local velocity and shear stress fields (as opposed to whole-channel values, as given above).
In fluid dynamics, Couette flow is the flow of a viscous fluid in the space between two surfaces, one of which is moving tangentially relative to the other. The relative motion of the surfaces imposes a shear stress on the fluid and induces flow.