Fluid flows have proved to be an integral part of many metallurgical processing operations. Metal, slag, and gas flows invariably affect the viability, effectiveness, and efficiency, of our reactor vessels. The performance characteristics of our blast furnaces and steelmaking vessels, such as BOF's, OBM's, ladles, tundishes, and the moulds of continuous casting machines, are all strongly influenced by such flows. Similarly, liquid metal quality and cast micro-structures, are also bound up with the way fluids have flowed and interacted. In all these aspects, the rapid evolution in our techniques and abilities to mathematically and physically model single and multi-phase flows and their attendant heat and mass transfer processes, have contributed significantly to our understanding, and ability, to control and improve these metallurgical processing operations, and to develop new and better processes. The evolution and application of computational fluid dynamics (CFD) over the past four decades has been particularly impressive. The author's many fine Japanese graduate students have made very valuable contributions to this new field of research for Process Metallurgists, as well as to the founding and scientific support of the McGill Metals Processing Centre, MMPC, following their return to Japan.