Source Term Model Approaches to Film Cooling Simulations

Doctoral thesis, 2001

Film cooling simulations using Computational Fluid Dynamics (CFD) are very difficult and extremely computer power demanding. This thesis deals with the development of a method to save computer power for these types of simulations. The cooling air is injected using additions to the source terms of the discretised governing equations. Cell lengths up to about one or two cooling hole diameters are used, thereby precluding modelling of the detailed flow around each cooling hole. Three different models for distributing the source terms are evaluated. In the first model, the sources are distributed to only one cell, namely the cell closest to the cooling hole, resulting in a poorly penetrating jet. To obtain better jet penetration and to be able to better control the concentration of coolant at the wall, the second model distributes the sources as a line source. This model produced reasonable results for the heat transfer rate on a film-cooled nozzle guide vane but not for temperature comparisons on multi-row effusion-cooled plates. The results were found to be sensitive to some input parameters. The third model uses limited parts of source term fields, evaluated from the averaged solutions of detailed jet simulations. This model showed the best and most realistic injection of the coolant. Owing to the different qualities of the results, especially for the first and second models, the method should be seen as a ``last way out`` when it is not possible to make detailed 3D simulations of high quality due to a lack of computer power.