ESDU 87015 presents design recommendations for various performance improvement methods such as vanes or splitters, screens or perforated plates, surface roughness or ribs cut transversely in the walls, vortex generators, truncation, injection or boundary layer suction, use of curved walls, or the use of star-shaped inserts. Although the information on design and performance improvement is obtained from only limited ranges of test data drawn from the literature, a tentative basis for interpolation or extrapolation is suggested. A tabular presentation summarising the methods and their advantages and limitations guides the user in selecting the most appropriate, and a comprehensive worked example illustrates the use of the information.