DLR’s S4 Rotor Code Validation With HART II Data: The Baseline Case

Abstract

S4 is the name of DLR’s high resolution rotor code for simulation of aerodynamics, dynamics, acoustics and flow field of isolated rotors like those being operated in the wind tunnel. In 2001, the HART II test was performed by DLR, ONERA, US Army AFDD, NASA Langley and DNW in the large low-speed facility (LLF) of the DNW. The test encompasses the Bo105 40% Mach scaled and dynamically scaled model rotor in descent flight condition creating a large amount of blade-vortex interaction (BVI) noise as the baseline (BL) case. Higher harmonic control (HHC) was applied at 3/rev with different phases for minimum noise radia-tion (MN) and for minimum vibration characteristics (MV). This paper addresses the S4 code validation using HART II data of blade motion, section air loads and acoustic radiation. Acoustic radiation is post-processed by DLR acoustic code APSIM using S4 unsteady airloads as input. It is found that even with such kind of comprehensive code qualitatively and quantitatively good results can be obtained for all these aspects, when appropriate engineering models are applied: unsteady aerodynamics, fully elastic blades and wake vortex system with prescribed geometry.