Multidisciplinary Modeling of the CH-47 Helicopter with CFD/CSD Coupling and Trim

This paper presents work done on modeling the CH-47 tandem rotor helicopter with fuselage in high speed forward flight using computational fluid dynamics coupled with a comprehensive rotorcraft analysis tool. The flow calculations and subsequent airloads were generated by a modfied version of OVERFLOW-2, which includes elastic blade modeling. The structural dynamic calculations are provided by the CSD module in RCAS-the US Army's comprehensive rotorcraft analysis tool-while the trim module in RCAS trims the whole aircraft. RCAS calculates all the predicted rotor motions for a full period using the airloads obtained from OVERFLOW. OVERFLOW deflects the blades, and then calculates the flow about the newly deflected rotor blades. The loose coupling between the two codes is repeated on a periodic basis until the solution converges. The computed results arc, compared qualitatively with Boeing experimental and flight test data and show good agreement. The results are presented mainly to validate the methodology; so extensive quantitative analyses are not included. The work. demonstrates that a high fidelity, comprehensive modeling of a full rotorcraft in flight is now possible, and is a significant advancement in rotorcraft analysis over current state-of-the-art comprehensive tools.