Massimo Biava

Fully Implicit Discrete Adjoint Methods for Rotorcraft Applications

This paper presents the development of a fully implicit, low-memory discrete-adjoint method by means of automatic source-code differentiation applied to the Helicopter Multi-Block computational fluid dynamics solver. The method is suitable for applications in flight mechanics, as well as shape optimization, and is demonstrated in this paper for popular flow cases reported in the literature. In particular, adjoint computational fluid dynamics computations were undertaken for airfoils, wings, and rotor-blade cases, and the obtained results were found to agree well with published solutions and with finite differences of flow derivatives. The method has been demonstrated for inviscid and viscous cases, and the results suggest that the current implementation is robust and efficient. The cost of the adjoint computations is relatively low due to the employed source-code differentiation, and most of the time, it is no more than the cost of a steady-state flow solution.

Computation of Rotorcraft Stability Derivatives Using the Discrete Adjoint Method

This chapter presents a method for computing rotorcraft stability derivatives based on the discrete adjoint method. The adjoint equations are derived by means of automatic source-code differentiation, and solved using a fully implicit, low-memory fixed-point iteration scheme. The method is demonstrated for two rotor-blade cases, and the obtained results were found to agree well with finite differences of flow derivatives. The cost of the adjoint computations is relatively low due to the employed source-code differentiation, and most of the time, it is no more than the cost of a steady-state flow solution.