Hoffmann, Florian
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Item-typ:Veröffentlichung, A Combined Rigid-Soft Thruster Based on Jetting Propulsion(IEEE, 2023); ; ; ; Ahstract- A new underwater thrust device is proposed in this work that makes use of a soft outer structure in combination with a parallel linkage and driven by a classical actuator. By merging soft and rigid parts, we hope to increase the performance of pulsed jet propulsion that plays a crucial role in attitude control for AUVs. But also simpler models for design and control can be applied by this approach. A specific linkage design for actuation, along with two different soft structures (mantles) are introduced and evaluated in experiments which indicate efficient thrust creation. Particle Image Velocimetry (PIV) experiments show the formation of vortex rings that suggest efficient propulsion, whereby the wider and more flexible mantel is characterized by higher momentum and thrust.Wissenschaftlicher Artikel109 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Hydrofoil-like legs help stream mayfly larvae to stay on the ground(Springer, 2023-03); ; ; ; Adaptations to flow have already been in the focus of early stream research, but till today morphological adaptations of stream insects are hardly understood. While most previous stream research focused on drag, the effects of lift on ground-living stream insects have been often overlooked. Stream mayfly larvae Ecdyonurus sp. graze on algae on top of the stones and therefore inhabit current exposed places in streams. They have a dorso-ventrally flattened body shape, which is known to reduce drag. However, this body shape enhances lift too, increasing the danger for the animal of getting detached from the substrate. Using microscopic techniques, 3D-printing, and drag and lift measurements in a wind tunnel, our experiments show that the widened femora of Ecdyonurus sp. can generate negative lift, contributing to counterbalance the (positive) lift of the overall body shape. The larvae can actively regulate the amount of lift by adjusting the femur's tilt or optimizing the distance to the ground. This shows that morphological adaptations of benthic stream insects can be very elaborate and can reach far beyond adaptations of the overall body shape. In the presented case, Ecdyonurus sp. takes advantage of the flow to overcome the flow's challenges.Wissenschaftlicher ArtikelBand:20989 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Biomimetrics and 3D printing for the optimization of underwater robotic systemsWissenschaftlicher Artikel55