Nikolaos S. Lagopoulos

Dolprop Industries AB · Research and Development

Reversed von Kármán streets are responsible for a velocity surplus in the wake of flapping foils, indicating the onset of thrust generation. However, the wake pattern cannot be predicted based solely on the flapping peak-to-peak amplitude and frequency because the transition also depends sensitively on other details of the kinematics. In this work...

Symmetric flapping foils are known to produce deflected jets at high frequency–amplitude combinations even at a zero mean angle of attack. This reduces the frequency range of useful propulsive configurations without side force. In this study, we numerically analyse the interaction of these deflected jets for tandem flapping foils undergoing coupled...

In this work, we describe the impact of aspect ratio ( $AR$ ) on the performance of optimally phased, identical flapping flippers in a tandem configuration. Three-dimensional simulations are performed for seven sets of single and tandem finite foils at a moderate Reynolds number, with thrust producing, heave-to-pitch coupled kinematics. Increasing...

In this work, we describe the impact of aspect ratio (AR) on the performance of optimally phased, identical flapping flippers in a tandem configuration. Three-dimensional simulations are performed for seven sets of single and tandem finite foils at a moderate Reynolds number, with thrust producing, heave-to-pitch coupled kinematics. Increasing slen...

Marine vertebrates are well known to generate thrust via the oscillatory motion of bladelike body parts (e.g flippers, tails, fins, etc.). These configurations, often depicted as flapping floils in a two dimensional domain, demonstrate impressive manoeuvrability (Read et al., 2003) without the control imprecision exhibited by contemporary manmade d...

Have you wondered how you could straighten your deflected flapping-foil vortex wake? As shown in the simulations above, placing a second flapping foil in tandem behind the first can straighten that wake, even when placed five-chord lengths downstream while the flow is highly perturbed! Symmetric flapping foils are known to produce deflected wakes (...

Flapping foils are known to produce deflected jets at high frequency-amplitude combinations even at a zero mean angle of attack. This reduces the frequency range of useful propulsive configurations without side force. In this study, we analyse numerically the interaction of these deflected jets for tandem flapping foils, undergoing coupled heave to...

Reversed von K\'arm\'an streets are responsible for a velocity surplus in the wake of flapping foils, indicating the onset of thrust generation. However, the wake pattern cannot be predicted based solely on the flapping peak-to-peak amplitude $A$ and frequency $f$ because the transition also depends sensitively on other details of the kinematics. I...