Abstract
Abrupt changes in wind velocities over small distances in a lateral or vertical direction can produce wind shear which is known to have serious effects upon the performance of an aircraft. Brought about by large-scale changes in the atmospheric conditions, it is a three-dimensional flow phenomenon imposing severe velocity gradients on an aircraft from all possible directions. While it would be difficult to model an instantaneous velocity gradient in a lateral plane, a vortical flow impinging from the sides which represents a wind shear in a vertical direction is imposed on a forward-moving aircraft to investigate the effect on the aerodynamic performance. The maximum shear wind speed from the side was fixed at 0.3 times the forward velocity. After due validations under no-wind shear conditions on simpler half-reflection plane models, a BGK airfoil-based full 3D wing and the ONERA M6 3D wing model were selected for preliminary studies. The investigation was concluded using the ARA M100 wing-fuselage model.
Highlights
There are large numbers of weather patterns which can produce sudden three-dimensional uneven flow conditions anywhere in the atmosphere
The present investigation concentrates upon a simplified model of the wind shear in the vertical direction where a rotational side shear flow is imposed as the aircraft with uniform forward velocity
ARA M100 model pressure distribution Cp Streamlines colored by M
Summary
There are large numbers of weather patterns which can produce sudden three-dimensional uneven flow conditions anywhere in the atmosphere. From 1964 to 1985, wind shear directly caused or contributed to 26 major civil transport aircraft accidents in the U.S that led to 620 deaths and 200 injuries. The present investigation concentrates upon a simplified model of the wind shear in the vertical direction where a rotational side shear flow is imposed as the aircraft with uniform forward velocity. The flow past all 3D models was first studied under normal forward flow conditions, and the results were compared against measurements carried out in various wind tunnels. A vertical shear flow which varied from a maximum lateral flow at the top of the grid to zero in the aircraft horizontal plane to a negative maximum at the bottom end of the mesh was imposed upon the normal forward flow condition. The side vortical flow appears to degrade the aerodynamic performance of the aircraft
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