Shear velocity scales well to rates of dispersion and bedload sediment transport.
For river base case, the shear velocity can be calculated by Manning's equation.
[2] One method of obtaining the shear velocity is through non-dimensionalization of the turbulent equations of motion.
For example, in a fully developed turbulent channel flow or turbulent boundary layer, the streamwise momentum equation in the very near wall region reduces to: By integrating in the y-direction once, then non-dimensionalizing with an unknown velocity scale u∗ and viscous length scale ν/u∗, the equation reduces down to: or Since the right hand side is in non-dimensional variables, they must be of order 1.
This results in the left hand side also being of order one, which in turn give us a velocity scale for the turbulent fluctuations (as seen above): Here, τw refers to the local shear stress at the wall.
) is the height in meters above the ground at which zero wind speed is achieved as a result of flow obstacles such as trees or buildings.
Due to the limitation of observation instruments and the theory of mean values, the levels (z) should be chosen where there is enough difference between the measurement readings.
If one has more than two readings, the measurements can be fit to the above equation to determine the shear velocity.