Referring to the air lift wings, at takeoff and landing the ground may contribute to the generated lift force. The available infinite airfoils data are mostly given as a function of the angle of attack, where one can deduce the finite air foils behavior based on the geometrical and operational conditions. However, the ground effects may not well presented at least in fluid mechanics textbooks. We are looking for the physical concept interpretation, mathematical models, any available data concerning the contribution of the ground lift. Your contribution is highly appreciated . Thank you very much,,,
Mathematical Modelling of Material Handling Equipment - Nicely described .
The ground effect on the wing performance comes due to two main reasons; firstly, the ground surface interrupting developing the wingtip vortices and downwash behind the wing. This leads to lower induced drag, which increases the speed and lift of the aircraft. Reduced drag means lower thrust versus speed, where reduced induced drag requires less thrust, i.e. less power and lower fuel rate, in order to maintain the same speed. Secondly, referring to the generation of the lift by deflecting the oncoming airmass downward, flying close to the ground surface increases the air pressure on the lower side of the wing surface. This improves the aircraft lift with respect to the drag forces. The amount of the ground contribution depends on a number of factors including; airfoil and aircraft design, speed and distance above ground surface, weather conditions, and the nature of the ground surface whether is made of a concrete, other smooth hard surface, water, or broken ground.
The normal method -- and you can find sources at the NASA Technical Report Server or Cranfield's equivalent -- is by reflecting the aircraft's wing about the ground plane, forming a virtual biplane.
Examples at https://ntrs.nasa.gov/search.jsp?N=0&DocumentID=19930080862|19930091333|19930094588|19930094646|19930094742
Mathematical Modelling of Material Handling Equipment - Nicely described .
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