This volume contains the 22 contributions of the Workshop on 3D-Computation at Incompressible Internal Flows held in 1989 at the EPFL, Lausanne, Switzerland. This was the first GAMM Workshop on Numerical Methods in Fluid Mechanics developed to a real industrial problem, namely the flow simulation through a Francis turbine configuration. A large part of this book deals with the analysis of the contributed simulations and with their comparisons with the experimental data. It also contains a detailed description of the text cases, of the experimental set up and of the experimental data base.