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lotnictwo: Vortex ring state

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Since vortex rings are a surprisingly stable fluid dynamical phenomenon (a form of topological soliton), the best way to recover from them is to laterally steer clear of them, in order to re-establish lift, and to break them up using maximum engine power, in order to establish turbulence.

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The vortex ring state (VRS) is a dangerous aerodynamic condition that may arise in helicopter flight, when a vortex ring system engulfs the rotor, causing severe loss of lift. Often the term settling with power is used as a synonym, e.g., in Australia, the UK, and the US, but not in Canada, which uses the latter term for a different phenomenon. A vortex ring state sets in when the airflow around a helicopter's main rotor assumes a rotationally symmetrical form over the tips of the blades, supported by a laminar flow over the blade tips, and a countering upflow of air outside and away from the rotor. In this condition, the rotor falls into a new topological state of the surrounding flow field, induced by its own downwash, and suddenly loses lift. Since vortex rings are a surprisingly stable fluid dynamical phenomenon (a form of topological soliton), the best way to recover from them is to laterally steer clear of them, in order to re-establish lift, and to break them up using maximum engine power, in order to establish turbulence. This is also why the condition is often mistaken for "settling with insufficient power": high-powered maneuvers can both induce a vortex ring state in free air, and then at low altitude, during landing conditions, possibly break it. If sufficient power is not available to maintain the airfoil of the rotor at a stalled condition, while generating suffi…

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Jakość źródła: 65/100

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Notatka fact-checku: Fact-check 3.0-content-aware: no sufficient claim-bound corroboration after 3 healthy attempts. Scope=verify the factual claim. Required independent sources=2; stored evidence groups=1. Provider/API errors did not consume attempts. | Fact-check 4.3.2: research wznowiony bez zdejmowania HOLD. Poprzednia metoda: factcheck-300-content-aware. | Fact-check 4.3.2: research wznowiony bez zdejmowania HOLD. Poprzednia metoda: factcheck-weekly-research-432.

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The vortex ring state (VRS) is a dangerous aerodynamic condition that may arise in helicopter flight, when a vortex ring system engulfs the rotor, causing severe loss of lift. Often the term settling with power is used as a synonym, e.g., in Australia, the UK, and the US, but not in Canada, which uses the latter term for a different phenomenon. A vortex ring state sets in when the airflow around a helicopter's main rotor assumes a rotationally symmetrical form over the tips of the blades, supported by a laminar flow over the blade tips, and a countering upflow of air outside and away from the rotor. In this condition, the rotor falls into a new topological state of the surrounding flow fiel…

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Minimal-actuation feather star-inspired soft swimmers for multimodal 3D maneuverability.. Complex, three-dimensional (3D) motions typically require actuator arrays and complex control architectures. Here, we present a feather star-inspired soft robotic swimmer that uses only two pneumatic inputs to produce three distinct and switchable swimming modes: jellyfish-like pulsation, fishlike propulsion, and rotor-like reorientation. The robot owes this ability to mechanical intelligence: It leverages a monostable instability in its flexible arms to convert two control actuation inputs into 3D swimming modes, including ascension and descension, forward and backward swimming, hovering, and rotation…

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