Turbomachinery design and optimization using numerical technique has been presented in this book. Reynolds Average Navier-Stokes (RANS) equation based solution approach has been explained to design the system. Single as well as multi-objective optimization techniques are presented along with the analysis of flow field. Several surrogate based optimization techniques including a weighted average method was used for optimization. The Turbomachinery designers trying to enhance the system performance can follow the procedure explained in this book. In short, the books can be helpful for the Turbomachinery designers and academicians. This book may also be of general interest of designers and researchers who want CFD simulation of any system via RANS and want to apply systematic approach for optimization.