During his time at Imperial College in London he was involved in research and development work in fluid mechanics measuring techniques, like Hot-Wire- and Laser-Doppler-Anemometry. He continued this development work after joining a Special Research Centre at the Technical University of Karlsruhe in 1972. There the Phase-Doppler-Anemometry was developed for particulate two-phase flows with application to dispersion flows and sprays. He stayed at the centre in Karlsruhe for 10 years, carrying out research in laminar & turbulent fluid flows. Polymer flows, thin film flows and applications in wet-film coating, wind tunnel research and water treatments were part of his research in this time.
In 1982 Prof. Durst took over the directorship of the "Institute of Fluid Mechanics at the Friedrich Alexander University of Erlangen-Nuremberg". He built it up to a nationally and internationally highly recognized research institute in fluid mechanics.
One field of fluid mechanics was of particular interest to Prof. Durst relating to the validity of the basic equations of fluid mechanics, the continuity and the Navier-Stokes equations. He found out that, in their conventional from, these equations do not allow micro-channel and micro-capillary flows to be correctly predicted. The same is the case for shock wave flows and all other flows with strong density, pressure and temperature gradients. He derived the extended form of the basic equation of fluid mechanics and, with the help of some Ph.D.-students, he showed that these equations permit flows with strong gradients of fluid properties to be correctly predicted. The 2nd edition of his Fluid Mechanics textbook contains a complete chapter dealing with this new field of fluid mechanics.