Thomas Leweke
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View article: Experiments and simulations on short-wave instabilities in helical vortices
Experiments and simulations on short-wave instabilities in helical vortices Open
Short-wave instabilities of helical vortices are investigated experimentally using a one-bladed rotor and numerically with a spectral/spectral-element code. Certain rotor flow configurations, defined by the Reynolds number (Re) and tip spe…
View article: High-speed volumetric particle tracking measurements of unstable helical vortex pairs
High-speed volumetric particle tracking measurements of unstable helical vortex pairs Open
We present results from an experimental study investigating pairs of helical vortices generated by a one-bladed rotor in hovering conditions. Time-resolved volumetric Lagrangian particle tracking measurements are conducted in a water tunne…
View article: Fluid–structure interaction of a sphere rolling along an inclined plane
Fluid–structure interaction of a sphere rolling along an inclined plane Open
A comprehensive investigation, using experimental, computational and analytic methods, is reported on the motion of, and the forces on, spheres of different density ratios rolling freely down an incline in a fluid under gravity. The Reynol…
View article: Numerical investigation of rotor asymmetry to promote wake recovery
Numerical investigation of rotor asymmetry to promote wake recovery Open
Tip vortices in the wakes of wind turbines are known to have detrimental effects on downstream turbines such as reduced performance and increased fatigue loading. Rotor asymmetry is investigated as a passive method for mitigating these eff…
View article: Time-resolved volumetric particle tracking measurements of an unstable helical vortex pair
Time-resolved volumetric particle tracking measurements of an unstable helical vortex pair Open
We present the outcome of an experimental study of a helical vortex pair affected by the presence of centrifugal instabilities. Water tunnel experiments involving time-resolved volumetric Lagrangian Particle Tracking are used to investigat…
View article: Experimental investigation of blade tip vortex behavior in the wake of asymmetric rotors
Experimental investigation of blade tip vortex behavior in the wake of asymmetric rotors Open
Wakes behind rotors such as wind turbines, propellers, and helicopters can have detrimental effects on downstream structures including increased structural loading. These wakes are characterized by helical vortices shed from the blade tips…
View article: Simplified model for helical vortex dynamics in the wake of an asymmetric rotor
Simplified model for helical vortex dynamics in the wake of an asymmetric rotor Open
Helical vortex systems, such as those found in the wakes of wind turbines, helicopter rotors and propellers, are subject to instabilities that lead to pairing between adjacent vortex loops. Certain modes of these instabilities can be trigg…
View article: Global pairing instabilities of three interlaced helical vortices in the wake of an asymmetric rotor
Global pairing instabilities of three interlaced helical vortices in the wake of an asymmetric rotor Open
International audience
View article: Experiments on a helical vortex pair influenced by centrifugal instabilities
Experiments on a helical vortex pair influenced by centrifugal instabilities Open
International audience
View article: Instability of three interlaced helical vortices: application to asymmetric. rotor wakes
Instability of three interlaced helical vortices: application to asymmetric. rotor wakes Open
International audience
View article: Simplified model for capturing helical vortex interactions with applications to asymmetric rotor wakes
Simplified model for capturing helical vortex interactions with applications to asymmetric rotor wakes Open
International audience
View article: Experimental investigation of a rotor blade tip vortex pair
Experimental investigation of a rotor blade tip vortex pair Open
This paper presents the results of an experimental study of two closely spaced vortices generated by a rotating blade with a modified tip geometry. The experiments are carried out in two water channel facilities and involve a generic one-b…
View article: Instability and merging of a helical vortex pair in the wake of a rotor
Instability and merging of a helical vortex pair in the wake of a rotor Open
We present results from an experimental investigation of two closely spaced helical vortices. The two co-rotating vortices are generated in a water channel by a one-bladed rotor, whose tip geometry is modified by the addition of a perpendi…
View article: Deformation and wake of a flexible rotor in water
Deformation and wake of a flexible rotor in water Open
In this paper, we study experimentally the fluid-structure interaction of a simplified small-scale rotor operating in a water channel. The rotor consists of a single untwisted rectangular blade and is tested with various pitch angles at di…
View article: Experiments on helical vortex pairs in the wake of a rotor
Experiments on helical vortex pairs in the wake of a rotor Open
International audience
View article: Bluff Bodies and Wake–Wall Interactions
Bluff Bodies and Wake–Wall Interactions Open
This review surveys the dramatic variations in wake structures and flow transitions, in addition to body forces, that appear as the motion of bluff bodies through a fluid occurs increasingly closer to a solid wall. In particular, we discus…
View article: Wake dynamics and flow-induced vibration of a freely rolling cylinder
Wake dynamics and flow-induced vibration of a freely rolling cylinder Open
View article: Local and global pairing instabilities of two interlaced helical vortices
Local and global pairing instabilities of two interlaced helical vortices Open
We investigate theoretically and experimentally the stability of two interlaced helical vortices with respect to displacement perturbations having wavelengths that are large compared to the size of the vortex cores. First, existing theoret…
View article: Numerical investigation of the vortex roll-up from a helicopter\n blade-tip using a novel fixed-wing adaptation method
Numerical investigation of the vortex roll-up from a helicopter\n blade-tip using a novel fixed-wing adaptation method Open
This contribution relates to the simulation of the flow around the tip of a\nhelicopter rotor blade in hovering flight conditions. We here propose a new\nmethodology of framework adaptation, using a comprehensive rotor code and\nhigh-fidel…