The applications of computational fluid dynamics (CFD) are immense. Following the Les Houches 93 CFD session, this book presents the basic numerical methods for CFD and turbulence, and investigates important applications of CFD in engineering in the environment. The volume opens with a physical and engineering section and includes chapters covering numerical methods used in compressible CFD, principles of vortex and random-vortex methods, numerical methods for compressible flows and numerical simulations of variable-density flows at low match numbers are included. The second part of the book is devoted to geophysical fluid dynamics and topics such as three-dimensional turbulent phenomena arising in clouds dynamics and thunderstorms, (whose evolution may now be simulated deterministically) are discussed. The importance of large-eddy systems is emphasized for these simulations. A complete overview of ocean circulation and the quasi-geostrophic models which have been developed is included. The final chapters are devoted to mathematical and computing developments where all the facets of spectral methods are described. Principles of massively-parallel computing, with application to incompressible and compressible flows are presented.