This textbook offers a comprehensive exploration of turbulence in fluids and its complex modeling, tailored for postgraduate students and advanced undergraduates. It examines the multifaceted behavior of turbulent flows—marked by irregular fluctuations in velocity, pressure, and temperature—and addresses the challenges these pose for analysis and prediction. The text covers foundational theories and key modeling strategies, guiding readers from the basics of turbulent flow and laminar instabilities to the transition to turbulence. It presents detailed discussions on homogeneous and isotropic turbulence, the governing equations of turbulent motion, and the closure problem, with a focus on achieving simplifications that are physically, mathematically, and computationally meaningful. The book also delves into advanced modeling techniques, including the Unsteady Reynolds-Averaged Navier-Stokes (URANS) approach and its closure models, as well as hybrid methods such as URANS-URANS and URANS-LES (Large Eddy Simulation). Designed to deepen understanding, this text serves as a valuable resource for mastering the complexities of fluid dynamics and turbulence modeling.
