Related Experiment Video
Updated: Nov 11, 2025
09:17
Experimental Investigation of the Flow Structure over a Delta Wing Via Flow Visualization Methods
Published on: April 23, 2018
11.0K
Covert-inspired flaps for lift enhancement and stall mitigation.
1University of Illinois at Urbana-Champaign, 105 S. Mathews Ave., Urbana, IL 61801, United States of America.
Bioinspiration & Biomimetics
|March 30, 2021
Summary
A bird-inspired covert flap can delay stall by 5° and increase post-stall lift by 23% for unmanned aerial vehicles (UAVs). This flow control device shows tunable effectiveness on sharp stall airfoils but acts as a simple on/off switch for soft stall airfoils.
Area of Science:
- Aerospace Engineering
- Fluid Dynamics
- Bio-inspired Design
Background:
- Unmanned aerial vehicles (UAVs) exhibit limitations in adaptability and agility compared to birds, especially at low Reynolds numbers.
- Bird's covert feathers act as natural flow-control devices, mitigating flow separation, enhancing lift, and delaying stall.
- Understanding these biological mechanisms can inform the design of more effective UAVs.
Purpose of the Study:
- To investigate the effects of a covert-inspired flap on airfoil performance at Reynolds numbers relevant to small UAVs (10^5).
- To analyze how flap chord-wise location and deflection angle influence lift and drag on airfoils with distinct stall characteristics (sharp vs. soft).
- To compare the performance of freely-moving and static covert-inspired flaps.
Main Methods:
- Wind tunnel experiments were conducted on two airfoils: NACA 2414 (sharp stall) and E387(A) (soft stall).
- Numerical simulations were employed to analyze the aerodynamic principles behind the flap's effects.
- Investigated static and freely-moving flaps with varying chord-wise positions and deflection angles.
Main Results:
- The static covert-inspired flap successfully delayed stall by up to 5° and improved post-stall lift by up to 23%.
- Stall delay and lift enhancement were highly dependent on the airfoil's stall characteristics.
- For sharp stall airfoils, lift improvements were tunable via flap deflection and effective across various locations; for soft stall airfoils, the flap's effectiveness was limited and insensitive to adjustments.
Conclusions:
- The covert-inspired flap demonstrates significant potential as a flow control device for UAVs.
- Its effectiveness is tunable for sharp stall airfoils, offering versatile aerodynamic control.
- For soft stall airfoils, the flap serves primarily as a stall mitigation device with a binary on/off functionality.
Related Concept Videos
01:23Lift
298
Lift is a fundamental aerodynamic force that acts perpendicular to the direction of airflow. It plays a central role in achieving and sustaining flight and in stabilizing various vehicles. Lift primarily originates from pressure differences created across surfaces, such as an airfoil. A lower pressure region forms above the wing, while a higher pressure region forms below it, generating an upward force. This differential results from the shape and orientation of the airfoil, enabling the wing...
298
01:11Buoyancy and Stability for Submerged and Floating Bodies
2.3K
In fluid mechanics, buoyancy and stability are key concepts for understanding the behavior of submerged and floating bodies. When a stationary body is fully or partially submerged in a fluid, the fluid exerts a force on the body known as the buoyant force. This force acts vertically upward through a point called the center of buoyancy, which is the center of the displaced fluid volume. According to Archimedes' principle, the magnitude of the buoyant force is equal to the weight of the fluid...
2.3K
01:17Bernoulli's Principle: Applications
5.5K
There are many devices and situations in which fluid flows at a constant height and so can be analyzed using Bernoulli's principle. These devices include, but are not limited to, entrainment devices and fluid flow measuring devices.
Entrainment devices use a high fluid speed to create low pressures and, thus, entrain one fluid into another. Some examples of these devices are given below:
Entrainment devices use a high fluid speed to create low pressures and, thus, entrain one fluid into another. Some examples of these devices are given below:
5.5K
01:26Flail Chest-II
347
Managing flail chest, a condition characterized by a segment of the chest wall moving independently from the rest of the thoracic cage, requires a comprehensive approach. It includes a thorough assessment of the patient's condition, a diagnostic evaluation to determine the extent of the injury, and the implementation of appropriate medical interventions tailored to the individual's needs.
Assessment:
1. Clinical Evaluation:
History:
Assessment:
1. Clinical Evaluation:
History:
347
01:17Steady, Laminar Flow Between Parallel Plates
540
Understanding steady, laminar flow between parallel plates is essential for analyzing and designing flow in narrow rectangular channels, commonly found in various water conveyance and drainage systems. The Navier-Stokes equations govern fluid motion and are generally challenging to solve due to their nonlinearity. However, simplifications are possible in certain cases, like the steady laminar flow between parallel plates. For this scenario, we assume steady, incompressible, laminar flow.
540
01:01Bernoulli's Principle
10.9K
Bernoulli's equation incorporates how fluid pressure changes across a static, incompressible fluid by equating the kinetic energy contribution to zero. It is also helpful in analyzing horizontal flows in which the gravitational energy density is constant throughout. The latter equation is so useful that it is called Bernoulli's principle. According to Bernoulli's principle, the fluid pressure drops if the speed increases and vice versa.
Bernoulli's principle has several...
Bernoulli's principle has several...
10.9K