Thermal windIn atmospheric science, the thermal wind is the vector difference between the geostrophic wind at upper altitudes minus that at lower altitudes in the atmosphere. It is the hypothetical vertical wind shear that would exist if the winds obey geostrophic balance in the horizontal, while pressure obeys hydrostatic balance in the vertical. The combination of these two force balances is called thermal wind balance, a term generalizable also to more complicated horizontal flow balances such as gradient wind balance.
Wind speedIn meteorology, wind speed, or wind flow speed, is a fundamental atmospheric quantity caused by air moving from high to low pressure, usually due to changes in temperature. Wind speed is now commonly measured with an anemometer. Wind speed affects weather forecasting, aviation and maritime operations, construction projects, growth and metabolism rate of many plant species, and has countless other implications. Wind direction is usually almost parallel to isobars (and not perpendicular, as one might expect), due to Earth's rotation.
Savonius wind turbineSavonius wind turbines are a type of vertical-axis wind turbine (VAWT), used for converting the force of the wind into torque on a rotating shaft. The turbine consists of a number of aerofoils, usually—but not always—vertically mounted on a rotating shaft or framework, either ground stationed or tethered in airborne systems. The Savonius wind turbine was invented by the Finnish engineer Sigurd Johannes Savonius in 1922 and patented in 1926. Europeans had earlier experimented with curved blades on vertical wind turbines for many decades.
Early flying machinesEarly flying machines include all forms of aircraft studied or constructed before the development of the modern aeroplane by 1910. The story of modern flight begins more than a century before the first successful manned aeroplane, and the earliest aircraft thousands of years before. Some ancient mythologies feature legends of men using flying devices. One of the earliest known is the Greek legend of Daedalus; in Ovid's version, Daedalus fastens feathers together with thread and wax to mimic the wings of a bird.
Feasible regionIn mathematical optimization, a feasible region, feasible set, search space, or solution space is the set of all possible points (sets of values of the choice variables) of an optimization problem that satisfy the problem's constraints, potentially including inequalities, equalities, and integer constraints. This is the initial set of candidate solutions to the problem, before the set of candidates has been narrowed down.
