AcuSolve was used to simulate the hydrodynamic damping of water flowing over an flexible airfoil using the Practical Fluid Structure Interaction technology. The airfoil was excited by applying an initial displacement to the first mode, then letting it naturally decay. The added mass of surrounding water makes this a challenging FSI application from a numerical stability standpoint. The modal data for the analysis is provided by RADIOSS in OP2 format. The hydrodynamic damping ratio is calculated by evaluating the logarithmic decrement of the displacement time history plot from a monitor point placed on the airfoil surface. Altair ® AcuSolve ® Better Technology, Better Solution Advanced Technology, Accurate Results AcuSolve is based on the Galerkin/Least- Squares (GLS) finite element method. GLS is a higher-order accurate, yet stable formulation that uses equal order nodal interpolation for all variables, including pressure. The method is specifically designed to maintain local and global conservation of relevant quantities under all operating conditions and for all meshes. In addition to excellent spatial accuracy, AcuSolve has a second-order time integration option. Since AcuSolve obtains rapid nonlinear convergence within each time step, temporal accuracy is achieved in practice. AcuSolve has a very rich mathematical foundation, translating into superb numerical behavior. AcuSolve can easily solve the largest and most complex mission critical industrial problems. Robust Solution AcuSolve typically solves a given problem in the first attempt. Fully converged solutions are reliably obtained using AcuSolve’s efficient steady-state solver. Nonlinear convergence remains strong even as solutions approach their final result. Two key components contribute to this robustness: the GLS finite element formulation, and a novel iterative linear equation solver for the fully coupled pressure/velocity equation system. This powerful iterative solver is highly stable and is capable of efficiently handling unstructured meshes with high aspect ratios and badly distorted elements commonly produced by fully automatic mesh generators. This linear solver yields significant stability and convergence advantages over the segregated solution procedures commonly found in many commercial incompressible flow solvers. High Speed, Parallel Performance AcuSolve achieves fast solutions via three mechanisms: • Solution of the fully-coupled pressure/velocity equation system, which yields significant linear and nonlinear convergence speed. • Architected from the ground up for vector and cache-based super-scalar computers. • All algorithms are designed for multi-core parallel clusters, using a hybrid distributed/shared-memory (MPI/OpenMP) parallel model. The parallelization is completely transparent to end users.