This book contains contributions by colleagues, former students and friends of Professor Eli Reshotko in celebration of his 60th birth­ day. Since Professor Reshotko's scientific and engineering contribu­ tions have been in the areas of hydrodynamic stability, transition to turbulence, and boundary layer flows, it is only appropriate that the articles in this volume be devoted to these and related topics. The first two sections focus on instabilities and transition in sub­ sonic and supersonic flows, respectively. The third section deals with developing turbulence, while the the final section treats related prob­ lems in engineering fluid mechanics. The diversity and scope of the articles contained herein exemplify the insight and expertise required in the study of transitional and turbulent flows today - traits which also exemplify Eli Reshotko's contributions to these fields. A few of the articles in this volume were presented at a sym­ posium in honor of Eli Reshotko's 60th birthday, held in Newport News, Virginia, on July 28, 1991. The symposium was sponsored by lCASE, and organized by M.Y. Hussaini (lCASE) and R. Hirsh (U.S. National Science Foundation). Of those who could not attend, many chose to honor Professor Reshotko by a contribution to the volume dedicated to him. We would like to use this opportunity to express our deep ap­ preciation to M.Y. Hussaini for initiating this very special tribute to Eli, and to Ms. Emily Todd for her efforts in the volume preparation and in the organization of the symposium.

1. Instability and Transition in Subsonic Flow.- Bypass-Transition Research: Issues and Philosophy.- The Generation of Disturbances in a Boundary Layer by Wall Perturbations: The Vibrating Ribbon Revisited Once More.- The Preferred Spanwise Wavenumber in Subharmonic-Type Transition.- The Influence of Imperfections on the Stability of Subsonic Boundary Layers.- An Asymptotic-Numerical Method for the Orr-Sommerfeld Equation.- Direct Numerical Simulation of Instabilities in Parallel Flow with Spherical Roughness Elements.- A Study of Active Dither Control of Aerodynamic Instabilities in Axial-Compressors.- Dynamic Modelling of Axial Flow Compression Systems.- 2. Instability and Transition in High-Speed Flow.- Effect of Cooling on Boundary-Layer Stability at Mach Number 3.- Stability of the Inviscid Shock Layer in Strong Interaction Flow Over a Hypersonic Flat Plate.- Effect of Mach Number on Instability Waves Generated From a Localized Disturbance.- Observations in Using Linear Stability Theory for 3-D Supersonic Boundary Layers.- 3. Turbulence in Nonequilibrium Flows.- Some Remarks on the Nature of Navier-Stokes Turbulence.- The Turbulence Structure in an Eight-Degree Conical Diffuser.- Turbulence Modeling for Recirculating Flows - Reasons and Approach.- Laser Doppler Anemometer Measurements in Recirculating Flowfields.- The Entrainment Rate for a Row of Turbulent Circular Jets.- Core Turbulence Effect on Naturally Occuring Modes in a Circular Jet.- Applications of CFD for Hypersonic Propulsion.- 4. Related Problems in Engineering Flows.- Diffusion Layer Structure in a Thermophoretically Affected Flow Over a Hot Surface.- Numerical Analysis for Thermo capillary Flow Experiment in Microgravity.- A Large Aspect Ratio Waverider.- Assessment of Scaling of Pressurized WaterReactor Emergency Core Coolant Bypass Flow Tests.