This volume contains papers presented to a EUROMECH-Colloquium held in Munich, September 30 to October 2, 1985. The Colloquium is number 199 in a series of colloquia inaugurated by the European Mechanics Committee. The meeting was jointly organized by the 'Lehrstuhl fur Stromungsmechanik' at the 'Technische Universitat Munchen' and the 'Institut fur Physik der Atmosphare' of the 'Deutsche Forschungs- und Versuchsanstalt fur Luft- und Raumfahrt' (DFVLR) in Oberpfaffenhofen. 'Direct' and 'large eddy simulation' are terms which denote two closely con nected methods of turbulence research. In a 'direct simulation' (DS), turbu lent motion is simulated by numerically integrating the Navier-Stokes equations in three-dimensional space and as a function of time. Besides ini tial and boundary conditions no physical simplifications are involved. Com puter resources limit the resolution in time and space, though simulations with an order of one million discrete points in space are feasible. The simu lated flow fields can be considered as true realizations of turbulent flow fields and analysed to answer questions on the basic behaviour of turbulence. Direct simulations are valid as long as all the excited scales remain within the band of resolved scales. This means that viscosity must be strong enough to damp out the not resolved scales or the simulation is restricted to a lim ited integration-time interval only. In summary, DS provides a tool to investigate turbulent motions from first principles at least for a finite band of scales.

Inhalt
Subcritical Transition to Turbulence in Channel Flow.- Vortical Mechanisms in Shear Flow Transition.- Subgrid Scale Models for Homogeneous Anisotropic Turbulence.- Application of Renormalization Group (RG) Methods to the Subgrid Modelling Problem.- Helical Fluctuations, Fractal Dimensions and Path Integral in the Theory of Turbulence.- Large-Eddy Simulation of Low Reynolds Number Channel Flow by Spectral and Finite Difference Methods.- Large Eddy Simulation of Turbulent Channel Flow by 1-Equation Model.- Numerical Prediction of Turbulent Plane Couette Flow by Large Eddy Simulation.- Advective Formulation of Large Eddy Simulation for Engineering Type Flows.- Large-Eddy Simulation of Turbulent Boundary Layer and Channel Flow at High Reynolds Number.- Numerical Investigation of a Vortical Structure in a Wall-Bounded Shear Flow.- Recent Results on the Structure of Turbulent Shear Flows using Simulation Databases.- Simulation of the Turbulent Rayleigh-Benard Problem using a Spectral/Finite Difference Technique.- Application of the TURBIT-3 Subgrid Scale Model to Scales Between Large Eddy and Direct Simulations.- Direct Simulation of High-Reynolds-Number Flows by Finite-Difference Methods.- Direct Simulation of Stably Stratified Turbulent Homogeneous Shear Flows.- The Effect of Coherent Modes on the Evolution of a Turbulent Mixing Layer.- Turbulent Flow near Density Inversion Layers.- A Large Eddy Simulation Model for the Stratus-Topped Boundary Layer.- Decay of Convective Turbulence, a Large Eddy Simulation.- 6. Summarizing Statements on Results, Trends and Recommendations.- List of Participants.- List of Authors.