This book is an expanded and refined version of a master's research project, now presented as a comprehensive study integrating both experimental and numerical methods. The book explores how swirl influences flow behavior, pressure recovery, and efficiency in conical diffusers-key components in aerospace and fluid machinery.The authors designed a transparent Perspex diffuser and introduced swirl using a custom vane-type swirler. Using hot-wire anemometry and Pitot probes, they measured velocity profiles, pressure distribution, and turbulence characteristics. To validate and extend the findings, simulations were performed using ANSYS Fluent with Reynolds Stress Modeling (RSM), ideal for capturing the complex dynamics of swirling flows.The study revealed that swirl at the inlet significantly reduces boundary layer separation and improves diffuser performance, especially when combined with a properly sized tailpipe. Detailed results include CAD models, flow visualizations, and performance plots.This book is a valuable reference for graduate students, researchers, and professionals working in fluid mechanics, turbomachinery, and industrial flow applications.