An Euler solution algorithm for steady helicopter-rotor flows

The Euler equations are sufficiently general to represent many of the complex features which occur in helicopter-rotor flows, including shock waves and blade-vortex interactions. Due to computer hardware constraints, however, the numerical solution of the Euler equations for rotor flows has been restricted to relatively coarse meshes, and has required run times which are impractical for the design environment. This work is concerned with the development of an effective Euler algorithm for steady rotor flows. In order to maximize both accuracy and efficiency, a number of spatial discretization options and acceleration techniques are implemented and compared.;The basic spatial discretization is performed using a multi-block, finite-volume approach. Both an upwind-biased, total variation diminishing (TVD) scheme and a centered artificial viscosity scheme are implemented for flux evaluation. A number of options have also been implemented for the application of solid-wall boundary conditions. Time integration is performed using an explicit Ringe-Kutta procedure. This process is expedited by the application of several acceleration techniques, including local time stepping, residual smoothing, enthalpy damping, and multigrid.;Comparison of the TVD and artificial viscosity schemes demonstrate that for the relatively coarse meshes used in practical rotor calculations, the flux evaluation method can significantly affect both accuracy and efficiency. It is concluded that although superior for shock capturing, the TVD scheme is not necessarily superior to the artificial viscosity scheme for wake capturing. In general, it is found that the accuracy of the TVD scheme increases for more compressive limiter functions. This increased accuracy is offset, however, by a lower rate of convergence to steady state.;Computations are performed for a range of two- and three-dimensional flows, including several rotor flows. Comparisons are made with experimental data, and results from other numerical methods. In general, the agreement is quite good, and demonstrates that the current algorithm provides an effective method for the analysis of steady rotor flows.