WG 1: Flow Measuring Techniques and Multiphase Flows
Flow Measuring Techniques
Flow measuring techniques provide insight into properties of flow fields, such as velocity, pressure, and temperature distributions, etc, which may in many cases be difficult to achieve by computational means. The present working group has special experience with two kinds of flow measuring techniques - optical techniques, based on interferometry, and a special kind of rheometry which looks at the elongational behaviour of liquid filaments in uniaxial elongational flows. The former flow measuring techniques are in particular Laser-Doppler anemometry (LDA), and Phase-Doppler anemometry (PDA) with its special forms Extended PDA (EPDA), Dual-Burst PDA (DB-PDA) and Dual-Mode PDA (DM-PDA). The group has experience in applications of these techniques to various kinds of single- and multi-phase flows. The latter rheometric flow measuring technique was developed and used for measuring the elongational viscosity of viscoelastic polymer solutions. The measurement results are used for characterising the atomization behaviour of polymer solutions. Applications to medical problems with viscoelastic body fluids - such as saliva and hyaluronic acid - are planned.
Multiphase flows form the biggest part of all flows in nature and engineering. The group works in the fields of bubbly liquid flows, on suspensions, on the flow in steel casting processes, and on sprays. The process of bubble formation on porous solid surfaces is investigated, the bubble dynamics during rise in liquids - without or with mass transfer to the ambient liquid - and methods for controlled bubble formation are subjects of research. In the field of suspensions, the sedimentation of single droplets in a pure liquid is investigated. In the steel casting flow, the melt flow laden with particles is of interest in the context of clogging. Finally the wide field of sprays and their applications is looked at to develop techniques for controlled spray formation, to quantify heat and mass transfer between the droplets and the host medium, and to study impingement of the sprays on solid surfaces.