Implementation of a trim routine in a rotor model for the numerical simulation of helicopter flow-fields

Includes bibliographical references (p. 82-83)The aim of the current project is to develop, validate and implement a trim routine for a numerical rotor model, developed for the use in simulations of a helicopter exterior flow-field. In this investigation a ROBIN fuselage geometry was utilised. Simulations of the fuselage without the rotor were carried out initially so that investigations into the computational grids and turbulence models could be done. The computational simulations were performed in the commercially available CFD solver, FLUENT® Computational grids were created for the near wall modelling approach and wall function approach. Some of the more applicable turbulence models available in the solver were compared. For the wall function approach grids the k - ε, and its variants, the RNG and realizable models were found to be suitable choices. For the near wall modelling approach grids used, the SST models performed the best. The rotor model used during this investigation utilised a combination of blade element and actuator disk theory. Forces exerted by the rotor are calculated with the use of blade characteristics and flow properties. These forces were applied to the domain as momentum sources terms. The rotor model was incorporated with the CFD solver, through the use of a User Defined Function (UDF). The method used to trim the rotor was the Newton-Raphson Iterative method. This trim routine was incorporated in the UDF used for the rotor model. Tests were conducted, on a 'rotor-alone' model, as well as the rotor and fuselage model. The trim routine was found to be rigorous and managed to trim the rotor in each of the tests conducted. Good agreement between experimental and numerical collective pitch angle and cyclic pitch coefficients were found. Also the effect of the fuselage on the trim conditions proved to be minimal