Effect Of Gust Width On Flat-Plate Response In Large Transverse Gust

The split velocity method was applied to study the response of a finite flat-plate wing with an aspect ratio of four encountering a large transverse gust with various gust widths. The gust is modeled by a "sine-squared" velocity profile with maximum magnitude equal to 80% of the freestream velocity. During the gust encounter, the flat plate experiences large unsteady forces associated with formation of a leading-edge vortex and massive vorticity shedding upon exiting of the gust. This study aims to investigate the effect of gust width on a flat-plate gust response at two angles of incidence: 0 and 45 deg. Computations show that the maximum lift peak increases logarithmically with increasing gust width, asymptotically reaching a fixed value. For a flat plate at 0 deg, the lift history during the incremental lift phase (initial response) agrees with the analytical solution based on Kussner's function up to gust width of four chords. For a wider gust, the maximum incremental lift is lower than the analytical estimated lift. For a flat plate at 45 deg, in wide gusts, the wake is nonlinear. Decremental lift below the steady-state value is observed upon gust exit, and it is followed by a secondary lift enhancement.