Prof. Dr. Alexandra von Kameke
Department of Mechanical Engineering and Production
Hamburg University of Applied Sciences
Berliner Tor 21
20099 Hamburg, Germany
Email: Prof. Dr. Alexandra von Kameke
Phone: +49 40 428 75 - 8624
- Reaction-Diffusion-Advection Systems
- Faraday Flow
- Vorticity generation
- Global and local mixing dynamics and statistics
- Turbulent inter-scale kinetic energy transfer
- Pipe turbulence
- Reaction front spreading
We are glad to welcome our new employee Raffaele Colombi (M.Sc. in Aeronautical Engineering, Linköping Sweden). He will be concerned with the DFG-Project:
"Generation of energy and vorticity production by surface waves through two-dimensional turbulence effects"
We study energy condensation in quasi two-dimensional turbulence that is driven by surface waves. This physical mechanism is investigated with regard to its potential for energy production.
In two-dimensional turbulence the net energy is transferred from small scales to large scales. Energy condensation develops when large scale friction is low and energy piles up at large scales. In this way, energy condensation produces large ordered flow structures from disordered small scale forcing that drives the two-dimensional turbulence. It was shown only recently that two-dimensional turbulence can also be driven by surface waves [von Kameke et al. 2011].
However, it is unclear if two-dimensional turbulence and energy condensation can also be driven by more naturally occurring unordered forcing as for instance provided by oceanic surface waves. Further, it is not yet fully understood how non-breaking surface waves generate horizontal vorticity, and if the waves have to possess certain properties, i.e., if they need to be standing, non-linear or monochromatic [Francois et al. 2014, Filatov et al. 2016]. Additionally, the necessary boundary conditions for energy condensation are vague and need clarification. And, it needs to be addressed if the process of energy condensation is stable to the introduction of further sources of drag, i.e., when a turbine is plugged into the fluid flow in order to retrieve energy.
Here, these open points are to be investigated using a Faraday experiment [von Kameke et al. 2010, von Kameke et al. 2011, von Kameke et al. 2013]. The generation of vorticity by the surface waves and the influence of the boundary- and forcing- conditions on energy condensation will be studied as well as the velocity statistics. To this end the full unsteady three-dimensional velocity field at the water surface and below the water surface needs to be recorded which has not been investigated so far. The latest optical methods will be used, such as time-resolved high speed planar particle image velocimetry and time-resolved three-dimensional particle image velocimetry and particle tracking. The complete velocity data allows to doubtlessly verify, if the flow obtained in each case is two-dimensional and, if energy condensation takes place. Two-dimensionality is analyzed on the basis of energy and enstrophy spectra and spectral fluxes, calculated with the aid of a novel filtering method [Eyink, 1995, von Kameke et al. 2011, von Kameke et al. 2013]. Moreover, existing three- dimensional flow structures will be identified and characterized. The forcing, exerted by the surface waves on the fluid-particles, and the resulting vorticity generation will be quantified by measuring the fluid surface elevation simultaneously to the PIV measurements and the subsequent usage of Lagrangian methods [von Kameke et al. 2011, von Kameke et al. 2013, LaCasce 2008] that allow to correlate both movements. The objective of this study is to uncover a new effective mechanism to retrieve renewable energy and will broaden insight into surface wave physics and two-dimensional turbulence.
Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 395843083
|Title: The impact of advective transport by the South Indian Ocean Countercurrent on the Madagascar plankton bloom|
|Written by: F. Huhn, A. von Kameke, V. Pérez Muñuzuri, M. J. Olascoaga, and F. J. Beron-Vera|
|in: Geophys. Res. 2012|
|Volume: 39 Number:|
Abstract: Based on ten years (1998-2007) of satellite ocean color data we analyze the spatiotemporal patterns in the seasonal Madagascar plankton bloom with respect to the advection of the recently discovered Southern Indian Ocean Countercurrent (SICC). In maps of Finite-time Lyapunov Exponents (FTLE) and Finite-Time Zonal Drift (FTZD) computed from altimetry derived velocities we observe a narrow zonal jet that starts at ˜25°S at the southern tip of Madagascar, an important upwelling region, and extends to the east further than the largest plankton blooms (˜2500 km). In bloom years, the jet coincides with large parts of the northern boundary of the plankton bloom, acting as a barrier to meridional transport. Our findings suggest that advection is an important and so far underestimated mechanism for the eastward propagation and the extent of the plankton bloom. This supports the hypothesis of a single nutrient source south of Madagascar.