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Subject of our investigations is the spatial distribution of a Newtonian liquid within a partially filled horizontal rotating hollow cylinder in dependence of the variables angular velocity and angular acceleration, cylinder filling and cylinder geometry as well as viscosity of the liquid. We focus on the development of a thin liquid film at the inner cylinder wall. The layer thickness was measured using a non‐invasive laser‐induced fluorescence measurement technique. In addition, the liquid distribution and flow topologies were observed and described using optical measurements.The occurring liquid distributions can be distinguished in three different states. At low angular velocities most of the liquid is located at the bottom area of the cylinder. However, a thin liquid film is always pulled out of the reservoir from the rotating cylinder wall. With increasing angular velocity more and more liquid is deflected and the locally measured film thickness increases. Exceeding a critical angular velocity, a centrifuged distribution of the whole liquid establishes. In this state the measured film thickness fits the theoretical calculated value quite well. Very complex liquid distributions and flow patterns develop in particular at critical angular velocities. In detail, at all investigated cylinder systems two critical angular velocities were verifiable, the so‐called transition points of liquid distribution. At the first critical velocity, the centrifuged state develops. With deceleration of the system a second critical angular velocity exists. Below this value the centrifuged distribution of the liquid collapses and moves back again to the bottom of the cylinder. A thin film is still pulled out of this reservoir. The second critical angular velocity of the break down is always smaller compared to the first one at which the centrifuged state develops. Both of them can be influenced using the investigated parameters. Eventually, we show that the locally measured film thickness also depends on these parameters. [ABSTRACT FROM AUTHOR]

Thermocapillary convection around an air bubble under a heated wall is experimentally investigated under gravitational conditions. The flow is basically studied through temperature fluctuation plots near the bubble periphery, which is subjected to an upward flow driving temperature gradient. This study illuminates the thermocapillary‐buoyancy convective flow behaviour within the regime of non‐periodic oscillations. Moreover, the fluid flow is qualitatively categorized according to the transient behaviour of the thermocapillary vortex boundary line around the bubble using the shadowgraph technique. A low viscous silicone oil as test fluid restricts reaching higher temperature gradients to avoid the formation of undesired vapour bubbles. However, pursuing the experiments under high pressures allowed reaching higher temperature gradients in order to achieve the non‐periodic flow regime. Both periodic and chaotic oscillations of the liquid flow around the bubble were recorded. They were distinguished from each other through the periodicity of the visualized thermocapillary vortex boundary line movements. The recording of temperature fluctuations at positions near the bubble during a time period Δt demonstrated the thermocapillary fluid flow behaviour at different Marangoni‐numbers Mg. [ABSTRACT FROM AUTHOR]

We experimentally investigated the specific behaviour of Newtonian thin liquid layers at curved solid edges in a continuative investigation of the so‐called picture framing effect coating error. We used adapted laser‐induced fluorescence technique (LIF) to measure the layer thickness distribution for the examination of the underlying edge bead in a cross section. The main motivation is to find optimal combinations of influencing quantities to reduce the picture framing effect (edge beads) in order to achieve a homogeneous layer thickness distribution of the liquid coating on the surface of the substrate, especially at the edges. For this purpose, we varied the viscosity of the Newtonian liquid, the edge radii of curvature of the substrate and its orientation regarding the gravitational direction. The results, i.e. the edge bead dependencies on the tested parameters, are physically plausible. With these findings the picture framing effect as a whole is manipulable regarding a minimisation of the coating error. [ABSTRACT FROM AUTHOR]

As part of an interdisciplinary major project regarding the development of a flexible and efficiently installable high-water protective system we investigated the behaviour of different system parts of flexible channel walls (thin, plastic slides/membranes) and types of self-installing water barricades subjected to different water channel flows experimentally and numerically. In the experiments we studied the strain of different flexible channel walls and the efficiency of various water barricades in a down-scale model by optical deformation, flow velocity and time measurements, respectively. We varied the water height as well as the representative flow velocity of the water channel flow and we also examined the influence of water waves onto these high-water protective system parts. Selected results will be shown and described concerning the stress on the used model-slide. In addition we applied similarity theory not only for general data presentation but also to generate findings regarding a future practical implementation in technical applications. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

The knowledge of the behaviour of thin liquid layers on solid surfaces is of fundamental interest as far as basic research and applications like technical covering or lubrication processes are concerned. The subject is currently of increasing importance, particularly due to stronger requirements of thin liquid layer functionalities. We therefore studied the development of the liquid layer thickness distribution field as well as the liquid layer disturbance propagation on a plane solid surface in the vicinity of a curved solid edge experimentally using LIF technique. The investigation focusses on the influence of the initial layer thickness as well as on liquid properties like viscosity and surface tension on the liquid film behaviour, especially close to solid edges. Selected experimental results are shown highlighting relevant quantities with respect to disturbance propagation and validation. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

The knowledge of the fluid behaviour in inclined cavities is of fundamental importance as far as heat and mass transfer are concerned. The interest in this subject is particularly increasing due to the rapid process in micro technologies. We therefore studied the flow- and temperature field of such flows numerically as well as experimentally using CFD and PIV/T, respectively. We present and discuss the numerical and experimental results of our investigations and explain the applied techniques. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]