William C. Reynolds (1933–2004) was a renowned and exceptionally creative scientist who specialized in turbulent flow and computational fluid dynamics. However, his competence spanned many areas of fluid mechanics, and of mechanical engineering in general. He completed his bachelor's (1954), master's (1955) and doctoral (1957) degrees at Stanford University, California. Reynolds chaired the Department of Mechanical Engineering from 1972 to 1982 and from 1989 to 1992. A pioneer in large eddy simulation for fluid modelling, he was elected to the National Academy of Engineering in 1979. He won the Fluid Engineering Award of the American Society of Mechanical Engineers in 1989 and the Otto Laporte Award by the American Physical Society in 1992. He was universally recognized as a gifted and original educator. He wrote several books, some on thermodynamics. Piero Colonna is Professor and Chair of Propulsion and Power at Delft University of Technology, where he has been teaching Thermodynamics and Modelling and Simulation of Energy Conversion Systems since 2002. He completed his master's degree (1991) in aerospace engineering at Politecnico di Milano, obtained a master's degree in mechanical engineering from Stanford University, California (1995) and a doctoral degree again from Politecnico di Milano (1996). In 2005, he became the recipient of the VIDI personal grant of the Dutch Science Foundation (NWO) for his research on the gas dynamics of dense vapours and supercritical fluids. He is also a recognized world expert of Organic Rankine Cycle and Supercritical CO2 power systems (renewable thermal energy conversion), and a pioneer of Non Ideal Compressible Fluid Dynamics (NICFD). He served as the Chairman of the Board of the International Gas Turbine Institute (2015–17), and is advisor to the Board of the Global Power and Propulsion Society. He was also Associate Editor of the ASME Journal for Engineering of Gas Turbines and Power, and is currently Associate Editor of the Journal of the Global Power and Propulsion Society. His talent as lecturer is testified by the Best M.Sc. Lecturer Award in Sustainable Energy Technology and Fluid Mechanics which he received twice in 2010 and 2012.