This issue of the journal THERMAL SCIENCE is dedicated to Prof. Franz Durst, head of the Institute of Fluid Mechanics at the University Erlangen-Niirnberg, in recognition of his extraordinary contributions in many fields of fluid mechanics. His 60th birthday is an appropriate moment to present to the readers of this journal a selection of his research contributions to turbulence, laser-Doppler anemometry, optical measurements in fluid mechanics and computational fluid dynamics. We hope that the papers written by his co-workers will give detailed insight into his scientific activity and into his efforts to unplement fundamental scientific results in different technologies. For the scientific community in Yugoslavia there is one more reason to honor Prof. Durst on his 60th birthday. Franz Durst has for many years exerted a significant influence on, and has made an immeasurable contribution to, the development of the research activity in fluid mechanics in Yugoslavia, particularly in the Laboratory for Thermal Engineering and Energy of the VINCA Institute. Prof. Durst has always expressed a permanent cordial friendship and interest for development of the research activity in the Laboratory.