Domain decomposition methods for sensitivity analysis of a nonlinear aeroelasticity problem Omar Ghattas and Xiaogang Li Computational Mechanics Laboratory Department of Civil and Environmental Engineering Carnegie Mellon University Pittsburgh, Pennsylvania 15213, USA We consider the nonlinear aeroelasticity problem of the interaction between a viscous, incompressible fluid and an elastic solid undergoing large displacement. The nonlinearities of the problem formulation include the solid and fluid governing equations, as well as the dependence of the flow geometry on the solid deformation. The resulting coupling is thus two-way. We develop domain-decomposition methods for solution and sensitivity analysis of the coupled problem. The domain decomposition is in the form of a block-Gauss-Seidel-like preconditioner that decomposes the coupled-domain problem into distinct nonoverlapping fluid and solid subdomain problems. The preconditioner thus enables exploitation of single-domain algorithms for solid and fluid mechanics discretization and solution. On the other hand, two-way fluid-solid coupling is retained within the residuals, which is essential for correct sensitivities. Sensitivities of field quantities can be found with little additional work beyond that required for solving the coupled fluid-solid system. The methodology developed here is illustrated by the solution of a problem of viscous incompressible flow about an infinite elastic cylinder. Sensitivities of the resulting velocity and displacement fields with respect to elastic modulus and fluid viscosity are computed.