The first edition of this book was concentrated on turbomachinery flow physics, design, off-design and nonlinear dynamics performance. As I mentioned in the preface to the first edition, in dealing with three-dimensional turbulent flows through a turbomachinery component, for the reasons I outlined, I refrained from presenting a multitude of existing turbulence models. In the meantime, only a few of those models have survived exhibiting the standard working tools implemented in almost all computational tools dealing with turbomachinery flow simulations. Experienced turbomachinery aerodynamicist knowledgeable of the underlying physics of the models in existing commercial codes is able to appropriately interpret the results. Without this knowledge, however, the user of commercial codes may tend to uncritically accept computational results as infallible. This issue has been addressed in the current second edition. While maintaining the unifying character of the book structure in this second revised and extended edition all chapters have undergone a rigorous update and enhancement. Accounting for the need of the turbomachinery community, three chapters have been added, that deal with computationally relevant aspects of turbomachinery design such as boundary layer transition, turbulence and boundary layer. With this second edition, the readers have a solid source of information for designing state-of-the art turbomachinery components and systems at hand.