The study of wall-bounded turbulent flows is of considerable interest from both scientific and practical view points. As such it has attracted a great deal of research over the last 100 years. Much research has concentrated on flows over smooth walls since these are simpler from experimental, numerical and theoretical standpoints. The flow over rough walls has still received considerable attention but progress has necessarily been slower. Perhaps the most essential problem (certainly from a practical point of view) is to be able to predict the skin-friction drag acting on a plate (or a body) given a certain known roughness characteristic of the surface. Unfortunately this has proved to be very difficult since even the simplest rough surfaces can be characterised by a number of different parameters and we still cannot directly connect these to the fluid dynamic drag in a given situation. Various theories and models have been proposed in order to make progress but there is still some disagreement in the community as to the correct understanding of these important flows. The IUTAM Symposium on the Physics of Wall-bounded Flows on Rough Walls was held in Clare College, Cambridge from the 7th - 9th July 2009 in order to bring together various expert researchers in the field to try and resolve some of these disagreements and to develop a consensus on the most fruitful directions of future research.

Zusammenfassung
The study of wall-bounded turbulent ows is of considerable interest from both scienti c and practical view points. As such it has attracted a great deal of research over the last 100 years. Much research has concentratedon ows over smooth walls since these are simpler from experimental, numerical and theoretical standpoints. The ow over rough walls has still received considerable attention but progress has necessarilybeenslower.Perhapsthemostessentialproblem(certainlyfromaprac- cal point of view) is to be able to predict the skin-frictiondrag acting on a plate (or a body) given a certain known roughness characteristic of the surface. Unfortunately this has proved to be very dif cult since even the simplest rough surfaces can be characterised by a number of different parameters and we still cannot directly c- nectthese tothe uiddynamicdragin a givensituation.Varioustheoriesandmodels have been proposed in order to make progress but there is still some disagreement in the community as to the correct understanding of these important ows.

Inhalt
Direct Numerical Simulation and PIV Measurement of Turbulent Boundary Layer over a Rod-Roughened Wall.- Turbulent Flows over Aligned and Inclined Ribs.- An Experimental Study of Turbulent Flow in the Vicinity of Transverse Square Bars.- Boundary Layer Structure over a Two-Dimensional Rough Wall.- Turbulence in Pipe Flows with Small Relative Roughness.- LDV Measurement Near a Rough Surface for a Turbulent Boundary Layer.- POD Analysis of the Near-Wall Region of a Rough Wall Turbulent Boundary Layer.- An Experimental Study of a Turbulent Wall Jet on Smooth and Rough Surfaces.- Turbulent Flow Over Urban-Type Roughness Using PIV.- A High Reynolds Number Turbulent Boundary Layer with Regular 'Braille-Type' Roughness.- On the Outer Layer Controversy for a Turbulent Boundary Layer over a Rough Wall.- Turbulent Channel Flow over Model Dynamic Roughness.- Log-Layer Dynamics in Smooth and Artificially-Rough Turbulent Channels.- Roughness Scaling Parameters in the Fully-Rough Regime.- Transition in Rough Channels.- Effect of Isotropic Free-stream Turbulence in Favorable Pressure Gradient Turbulent Boundary Layers over a Rough Surface.- Particulate Impact and Erosion in a Turbulent Serpentine Channel.- Rough Wall Skin Friction Measurements Using a High Resolution Surface Balance.- Modified Hierarchy Structure of Rough-Wall Flows.- Analysis of Instantaneous Velocity Vector in Geostrophic Turbulent Ekman Layer over a Transitional Rough Surface.- Wall Roughness Effects: A Second Law Analysis (SLA).- Coherent Structures in Turbulent Flow over Arrays of Cubical Obstacles.- Large Roughness Effects in Channel Flow.- Very-Rough-Wall Channel Flows: A DNS Study.