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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.
Automotive aerodynamics is studied using both computer modelling and wind tunnel testing. For the most accurate results from a wind tunnel test, the tunnel is sometimes equipped with a rolling road. This is a movable floor for the working section, which moves at the same speed as the air flow.
This allows direct estimation of the drag force at a given speed for any vehicle for which only the drag area is known and therefore easier comparison. As drag area CdA is the fundamental value that determines power required for a given cruise speed it is a critical parameter for fuel consumption at a steady speed. This relation also allows an ...
Drag coefficients in fluids with Reynolds number approximately 10 4 [1] [2] Shapes are depicted with the same projected frontal area. In fluid dynamics, the drag coefficient (commonly denoted as: , or ) is a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment, such as air or water.
The vehicle achieved a dead downwind speed of about 2.8 times the speed of the wind. [34] [35] [36] In 2011 a streamlined Blackbird reached close to 3 times the speed of wind. [33] Upwind—In 2012, Blackbird set the world's first certified record for going directly upwind faster than the wind, using only wind power. The vehicle achieved a dead ...
The power law is often used in wind power assessments [4] [5] where wind speeds at the height of a turbine ( 50 metres) must be estimated from near surface wind observations (~10 metres), or where wind speed data at various heights must be adjusted to a standard height [6] prior to use.
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Roughness length is a parameter used in modeling the horizontal mean wind speed near the ground. In wind vertical profile such the log wind profile, the roughness length (with dimension of length and SI unit of metres) is equivalent to the height at which the wind speed theoretically becomes zero in the absence of wind-slowing obstacles and ...