Hadi Hajibeygi is Professor of Geo-Energy Solid and Fluid Mechanics at Delft University of Technology (TU Delft). His teaching and research focus on the modeling and simulation of flow, transport and mechanics in porous media, with applications across geothermal energy, subsurface storage, and the energy transition. He teaches courses including Dynamics of Solids and Fluids, Multiphase Flow in Porous Media, Grand Challenges in Earth Sciences, Subsurface Storage, Advanced Reservoir Simulation, and Fluid Dynamics. Hadi runs an open lecture series on porous-media physics and simulaion on YouTube, of which this book is the written companion. Hadi holds PhD with medal from ETH Zurich and was a postdoctoral scholar at Stanford University before joining TU Delft in 2013 as professor. He was named the Most Innnovative Teaching Talent of TU Delft in 2018 and the Lecturer of the Year of the Faculty of Civil Engineering and Geosciences of TU Delft in 2026.