This book contains edited and improved versions of a selection of papers presented at the Fourth Symposium on Numerical and Physical Aspects of Aerodynamic Flows as well as J.H. Whitelaw's Stewartson Memorial Lecture. The topics covered are technology in two- and three-dimensional steady flows, two- and three-dimensional unsteady flows, and stability and transition. Each part begins with an overview of current research. The book addresses researchers in numerical and applied physics, and engineers in applied mechanics and fluid mechanics.