Low-dimensional models of internal combustion engine flows using the proper orthogonal decomposition

The analysis of the tumble breakup process in internal combustion in-cylinder flows is of a primary concern for engine designers. The high levels of turbulence immediately prior to ignition to which tumble breakup contributes can increase engine efficiency greatly. The proper orthogonal decomposition is designed to extract the most energetic structures from a turbulent flow making it ideal for the study of tumble breakup.; Computational and experimental datasets were used in several POD methods. A novel POD method was created which could be used in a flow which contained large energy fluctuations, a moving grid and high levels of divergence. The direct output of these POD methods was used to analyze the tumble breakup process. These methods extract and show the relative energies contained in the coherent structures, including tumble, during intake and compression.; The output of one of these POD methods is used as the basis set for a low-dimensional model of this flow during compression. A low-d model with only six modes captured the general dynamics of the flow while a 31 mode model more accurately recreates the original system. This model was used to explore other parameter ranges including a change in engine speed and varying levels of initial tumble strength. The flow of energy between individual modes of the model was examined which showed that the tumble vortex gains strength from the compression field before decaying to more complex structures.