Effect of Localised Pressure Depression and Rain on Aerodynamic Characteristics of MALE UAV

Abstract

This paper presents the effect of the local low-pressure region in the atmosphere and rain on aerodynamic characteristics of medium altitude long endurance unmanned aerial vehicle (MALE-UAV) configuration during cruise/loiter. Computations are performed using CFD++, a commercial CFD software suite. A large low-pressure depression past the MALE UAV (symmetrically and asymmetrically) with pressure 10-15 % lower than the free stream pressure and a widespread rainfall type with a rainfall rate of 1195 mm/hr., are considered for CFD simulation. A large low pressure that spans the whole MALE-UAV results in a decrement in both lift and drag, but does not affect the yawing and rolling moments significantly. However, a low-pressure region that engulfs only one-half of MALE UAV causes sudden/abrupt changes in rolling and yawing moments. The effect of rain causes a significant decrease in a lift at higher alpha, accompanied by a decrease in stall angle of 2 degrees, and a significant increase in drag. From the study, a Standard Operating Procedure (SOP) was adopted to fly UAVs in adverse weather effects, such that the aircraft can be operated with a velocity higher than 1.3Vstall and at a power setting not less than 75% of max power capacity.


Delta change in inviscid, viscous, and EDP components of lift and drag and its % due to rain.
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Description