A review of propeller modelling techniques based on Euler methods

Abstract

Future generation civil aircraft will be powered by new, highly efficient propeller propulsion systems. New, advanced design tools like Euler methods will be needed in the design process of these aircraft. This report describes the application of Euler methods to the modelling of flowfields generated by propellers. An introduction is given in the general layout of propellers and the propeller slipstream. It is argued that Euler methods can treat a wider range of flow conditions than the classical propeller theories. The power of Euler methods lies in the fact a separate wake model is not needed because their solution includes the propeller slipstream. Two different ways are described of modelling the propeller slipstream using Euler methods. These are the time-accurate approach that uses the real propeller geometry and the time-averaged approach using an actuator disc representation of the propeller. Both techniques and their specifics concerning the grid and the boundary conditions that have to be imposed are described. The results of a few propeller calculations using Euler methods are described. Discrepancies between experiments and the simulations can of ten be traced back to the neglect of the physical viscosity and the quality of the grid. Research is still ongoing into further improving the mathematical flow models and using new concepts like grid adaption.