This volume contains revised and edited forms of papers presented at the Symposium on Numerical and Physical Aspects of Aerodynamic Flows, held at the California State University from 19 to 21 January 1981. The Symposium was organized to bring together leading research workers in those aspects of aerodynamic flows represented by the five parts and to fulfill the following purposes : first, to allow the presentation of technical papers which provide a basis for research workers to assess the present status of the subject and to formulate priorities for the future; and second, to promote informal discussion and thereby to assist the communication and develop ment of novel concepts. The format ofthe content ofthe volume is similar to that ofthe Symposium and addresses, in separate parts: Numerical Fluid Dynamics, Interactive Steady Boundary Layers, Singularities in Unsteady Boundary Layers, Transonic Flows, and Experimental Fluid Dynamics. The motivation for most of the work described relates to the internal and extern al aerodynamics of aircraft and to the development and appraisal of design methods based on numerical solutions to conservation equations in differential forms, for corresponding components. The chapters concerned with numerical fluid dynamics can, perhaps, be interpreted in a more general context, but the emphasis on boundary-Iayer flows and the special consideration oftransonic flows reflects the interest in external flows and the recent advances which have allowed the calculation methods to encompass transonic regions.