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

M. Vijayakumar; K M Parammasivam; S Rajagopal; C. Balaji

doi:10.14429/dsj.73.17481

M. Vijayakumar DRDO-Aeronautical Development Establishment, Bengaluru - 560 075, India https://orcid.org/0000-0003-0097-5580
K M Parammasivam Department of Aerospace Engineering, Anna University, Chennai - 600 025, India https://orcid.org/0000-0001-5987-4368
S Rajagopal DRDO-Aeronautical Development Establishment, Bengaluru - 560 075, India https://orcid.org/0000-0002-2405-544X
C. Balaji Senior Scientist, Metacomp Technologies Pvt. Ltd., Chennai - 600 020, India https://orcid.org/0000-0001-7252-5795

DOI: https://doi.org/10.14429/dsj.73.17481

Keywords: MALE(Medium Altitude Long Endurance), UAV(Unmanned Aerial Vehicle), Low-pressure depression, Rain, Eulerian dispersed phase model(EDP), Adverse weather effects

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.