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Direction shown by smoke drift but not by wind vanes 2 Light breeze 4–6 knots 4–7 mph 6–11 km/h 1.6–3.3 m/s 1–2 ft 0.3–0.6 m Small wavelets still short but more pronounced; crests have a glassy appearance but do not break Wind felt on face; leaves rustle; wind vane moved by wind 3 Gentle breeze 7–10 knots 8–12 mph 12–19 km/h
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.
Measurements show that wind speed, (V (h) ) varies, according to a power law with height (h) above a non-zero measurement height datum (h 0 —e.g. at the height of the foot of a sail), using a reference wind speed measured at the datum height (V (h 0) ), as follows: [24] [25]
The wind triangle is a vector diagram, with three vectors. The air vector represents the motion of the aircraft through the airmass. It is described by true airspeed and true heading. The wind vector represents the motion of the airmass over the ground. It is described by wind speed and the inverse of wind direction.
A polar diagram, or polar plot, is a graph that shows a sailboat's potential speed over a range of wind speeds and relative wind angles. [1] It normally consists of the right side of a line chart with the radius representing the yacht speed and the angle representing the wind direction blowing from top to bottom. Several lines are normally ...
A V-n diagram showing V S (stall speed at 1G), V C (corner/maneuver speed) and V D (dive speed) A chart of velocity versus load factor (or V-n diagram) is another way of showing limits of aircraft performance. It shows how much load factor can be safely achieved at different airspeeds. [3]
The wind profile power law relationship is = where is the wind speed (in metres per second) at height (in metres), and is the known wind speed at a reference height .The exponent is an empirically derived coefficient that varies dependent upon the stability of the atmosphere.
The tip-speed ratio, λ, or TSR for wind turbines is the ratio between the tangential speed of the tip of a blade and the actual speed of the wind, v. The tip-speed ratio is related to efficiency, with the optimum varying with blade design. [1] Higher tip speeds result in higher noise levels and require stronger blades due to larger centrifugal ...