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General External Flow Characteristics01:26

General External Flow Characteristics

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The study of external flow is essential for creating structures and objects that interact efficiently and safely with moving fluids, such as air or water. When a body is immersed in a flowing fluid, it experiences two primary forces: drag, which opposes motion along the flow direction, and lift, which acts perpendicular to the flow. The shape, size, and orientation of the object influence these forces.Streamlined and Blunt Bodies in External FlowObjects in fluid flow are classified as...
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Plane potential flows simplify fluid motion by assuming the fluid to be irrotational and incompressible. These characteristics allow these flows to be described by a velocity potential function, ϕ, representing the flow speed in a given direction, and a stream function, ψ, that visualizes the flow path, both governed by Laplace's equation. These parameters help in estimating flow patterns, velocity distributions, and pressure fields around various hydraulic structures.
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Gradually Varying Flow01:29

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Gradually varying flow (GVF) in open channels describes situations where water depth changes slowly along the channel due to factors like non-uniform bed slope, channel shape variations, or obstructions. This flow type occurs when the depth adjusts gradually to balance gravitational forces, shear forces, and energy requirements, resulting in a low rate of depth change.Characteristics of Gradually Varying FlowGVF is commonly observed in natural streams, rivers, and canals, where flow depth...
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From grasshoppers to gliders: evaluating the role of hindwing morphology in gliding flight.

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Distributed feather-inspired flow control mitigates stall and expands flight envelope.

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Feather-inspired flow control device across flight regimes.

Ahmed K Othman1, Nirmal J Nair2, Andres Goza2

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Bio-inspired covert flaps enhance lift by up to 12% in airfoils, mimicking bird feather control. These flaps offer improved agility and adaptability for uncrewed aerial vehicles across various flight conditions.

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Area of Science:

  • Aerodynamics
  • Bio-inspired engineering
  • Fluid dynamics

Background:

  • Traditional flow control methods face limitations in efficiency and adaptability.
  • Small uncrewed aerial vehicles (UAVs) require enhanced agility and adaptability, similar to birds.
  • Birds utilize covert feathers for flow control during different flight regimes.

Purpose of the Study:

  • Investigate covert feather-inspired flaps for aerodynamic flow control.
  • Analyze flap performance across different Reynolds numbers (200,000 and 1,000).
  • Determine the impact of flap structural parameters on aerodynamic lift.

Main Methods:

  • Experimental and simulation-based investigation of torsionally hinged flaps on a NACA2414 airfoil.
  • Systematic variation of flap location, hinge stiffness, and moment of inertia.
  • Analysis of aerodynamic performance, including lift improvements and flow physics.

Main Results:

  • Achieved up to 12% lift improvement post-stall compared to a flap-less baseline.
  • Lift enhancement is sensitive to flap structural properties and location.
  • Hinge stiffness influences mean deflection and time-averaged lift; moment of inertia affects flap dynamics and instantaneous lift.

Conclusions:

  • Covert-inspired flaps demonstrate significant potential for aerodynamic lift improvement.
  • Flap performance is adaptable across different Reynolds numbers, mimicking avian flight.
  • This technology offers a feasible flow control solution for diverse UAV missions and speeds.