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The Bulk Richardson Number (BRN) is an approximation of the Gradient Richardson number. [1] The BRN is a dimensionless ratio in meteorology related to the consumption of turbulence divided by the shear production (the generation of turbulence kinetic energy caused by wind shear) of turbulence.
Roughness length is a parameter of some vertical wind profile equations that model the horizontal mean wind speed near the ground. In the log wind profile, it is equivalent to the height at which the wind speed theoretically becomes zero in the absence of wind-slowing obstacles and under neutral conditions. In reality, the wind at this height ...
The Shields parameter, also called the Shields criterion or Shields number, is a nondimensional number used to calculate the initiation of motion of sediment in a fluid flow. It is a dimensionalization of a shear stress , and is typically denoted ψ {\displaystyle \psi } or θ {\displaystyle \theta } .
In common usage, wind gradient, more specifically wind speed gradient [1] or wind velocity gradient, [2] or alternatively shear wind, [3] is the vertical component of the gradient of the mean horizontal wind speed in the lower atmosphere. [4] It is the rate of increase of wind strength with unit increase in height above ground level.
Wind setup, also known as wind effect or storm effect, refers to the rise in water level in seas, lakes, or other large bodies of water caused by winds pushing the water in a specific direction. As the wind moves across the water’s surface, it applies shear stress to the water, generating a wind-driven current.
It is important to realise that is the shear stress exerted by the flow (i.e. a property of the flow) and is the shear stress at which the grains move (i.e. a property of the grains). The shear stress velocity is often used instead of the shear stress:
The use of the depth–slope product — in computing the bed shear-stress — specifically refers to two assumptions that are widely applicable to natural river channels: that the angle of the channel from horizontal is small enough that it can be approximated as the slope by the small-angle formula, and that the channel is much wider than it is deep, and sidewall effects can be ignored.
In simple contexts, a single number may suffice to describe the strain, and therefore the strain rate. For example, when a long and uniform rubber band is gradually stretched by pulling at the ends, the strain can be defined as the ratio between the amount of stretching and the original length of the band: