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Owls’ silent flight is commonly attributed to their special wing morphology combined with wingbeat kinematics. One of these special morphological features is the leading-edge serrations: rigid miniature hook-like patterns found at the primaries of the wings’ leading-edge. It is hypothesized that leading-edge serrations function as a passive flow control mechanism, impact the aerodynamic performance, supposedly alter the boundary layer over the wing, and the wake dynamics. We study the flow physics associated with owls’ leading-edge serrations using an owl wing with mimicked serrated geometry at Rec=40,000. We measured the flow characteristics of the boundary layer over the wing for various angles of attack (6o-20o) using PIV in a water channel. The experimental results suggest that leading-edge serrations modify the boundary layer over the wing. At low angles of attack (&lt;20o), the serrations amplified the turbulence activity over the wing planform. At 20o, the serrations act to suppress existing turbulence conditions, presumably by causing an earlier separation closer to the leading-edge region, thus enabling the flow to reattach prior to shedding downstream. These results served as a benchmark for numerical simulations using DNS to elucidate the underlying mechanisms of the flow dynamics due to presence of these micro-structures. The 3D simulations shown that the serrations improve suction surface flow by promoting sustained flow reattachment via streamwise vorticity generation at the shear layer, prompting weaker reverse flow, and thus augmenting stall resistance. However, aerodynamic performance is negatively impacted due to the shear layer passing through the serration array which results in altered surface pressure distribution over the upper surface.

SEB Conference Prague 2024

Fluid-wing interaction over inspired owl wing with leading edge serrations

serrations

owls

fluid dyanmics

Owls’ silent flight is commonly attributed to their special wing morphology combined with wingbeat kinematics. One of these special morphological features is the leading-edge serrations: rigid miniature hook-like patterns found at the primaries of the wings’ leading-edge. It is hypothesized that leading-edge serrations function as a passive flow control mechanism, impact the aerodynamic performance, supposedly alter the boundary layer over the wing, and the wake dynamics. We study the flow physics associated with owls’ leading-edge serrations using an owl wing with mimicked serrated geometry at Rec=40,000. We measured the flow characteristics of the boundary layer over the wing for various angles of attack (6o-20o) using PIV in a water channel. The experimental results suggest that leading-edge serrations modify the boundary layer over the wing. At low angles of attack (<20o), the serrations amplified the turbulence activity over the wing planform. At 20o, the serrations act to suppress existing turbulence conditions, presumably by causing an earlier separation closer to the leading-edge region, thus enabling the flow to reattach prior to shedding downstream. These results served as a benchmark for numerical simulations using DNS to elucidate the underlying mechanisms of the flow dynamics due to presence of these micro-structures. The 3D simulations shown that the serrations improve suction surface flow by promoting sustained flow reattachment via streamwise vorticity generation at the shear layer, prompting weaker reverse flow, and thus augmenting stall resistance. However, aerodynamic performance is negatively impacted due to the shear layer passing through the serration array which results in altered surface pressure distribution over the upper surface.

technical paper

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The mechanistic link between metabolic rate and foraging behaviour underpins several energy-based ecological theories, yet whether and how they interact remains unclear. Here we aimed to assess how modes of behaviour, in terms of cumulative space use, patch selection and time spent in an experimental resource patchy environment, are influenced by the foragers’ metabolic rate (SMR) and its main determinants i.e. body mass and temperature. We tested the individual behavioural patterns and metabolic rates of a model organism, the amphipod Gammarus insensibilis, across a range of body masses and temperatures. Our findings showed that body mass and temperature exert a major influence on foraging decisions and space use behaviour via their effects on metabolic rates. Individual cumulative space use was found to scale allometrically with body mass and exponentially with temperature, with patch giving-up time falling as body mass and temperature increased. Moreover, SMR had greater predictive power for behavioural patterns, explaining variation beyond that accounted for by body mass and temperature combined. Our results showed that cumulative space use scaled positively with mass-and-temperature-adjusted SMR (residual). Furthermore, the foraging decisions regarding patch choice and partitioning were strongly related to mass-and-temperature-adjusted SMR; individuals with higher mass-and-temperature-adjusted SMR initially preferred the most profitable patch and, as time progressed, abandoned the patch earlier compared to others. Our findings regarding the mechanistic relationship between behavioural patterns and metabolic rate across body mass and temperature shed light on higher-order energy-based ecological processes, with implications in the face of climate change.

Foraging decisions and space use behavior are linked to metabolic rate across temperatures

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Fluid-wing interaction over inspired owl wing with leading edge serrations

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Fluid-wing interaction over inspired owl wing with leading edge serrations

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Foraging decisions and space use behavior are linked to metabolic rate across temperatures

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