The transition of the cylinder wake is investigated experimentally in a water channel and is computed numerically using a finite-difference scheme. Four physically different instabilities are observed: a local "vortex-adhesion mode," and three near-wake instabilities, which are associated with three different spanwise wavelengths of approximately 1, 2, and 4 diam. All four instability processes can originate in a narrow Reynolds-number interval between 160 and 230, and may give rise to different transition scenarios. Thus, Williamson's [Phys. Fluids 31, 3165 (1988)] experimental observation of a hard transition is for the first time numerically reproduced, and is found to be induced by the vortex-adhesion mode. Without vortex-adhesion, a soft onset of three-dimensionality is numerically and experimentally obtained. A control-wire technique is proposed, which suppresses transition up to a Reynolds number of 230.

A coupled Landau model describing the Strouhal-Reynolds number profile of a three-dimensional circular cylinder wake Phys. Fluids 15, L68 (2003);

The hydrodeoxygenation of guaiacol is investigated over bulk ceria and ceria-zirconia catalysts with different elemental compositions. The reactions are performed in a flow reactor at 1 atm and 275-400 °C. The primary products are phenol and catechol, whereas cresol and benzene are formed as secondary products. No products with hydrogenated rings are formed. The highest conversion of guaiacol is achieved over a catalyst containing 60 mol % CeO2 and 40 mol % ZrO2 . Pseudo-first-order activation energies of 97-114 kJ mol(-1) are observed over the mixed metal oxide catalysts. None of the catalysts show significant deactivation during 72 h on stream. The important physicochemical properties of the catalysts are characterized by X-ray diffraction (XRD), temperature-programmed reduction, titration of oxygen vacancies, and temperature-programmed desorption of ammonia. On the basis of these experimental results, the reasons for the observed reactivity trends are identified.

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