Related Experiment Video
Updated: Jan 5, 2026
09:17
Experimental Investigation of the Flow Structure over a Delta Wing Via Flow Visualization Methods
Published on: April 23, 2018
11.2K
Influence of a Backward-Facing Step on Swept-Wing Boundary-Layer Transition.
Jenna L Eppink1, Richard W Wlezien2, Rudolph A King1
1NASA Langley Research Center, Hampton, Virginia 23681.
AIAA Journal. American Institute of Aeronautics and Astronautics
|October 22, 2019
Summary
A backward-facing step significantly impacts boundary layer transition by increasing unsteady disturbances. These disturbances, amplified by stationary crossflow vortices, lead to intermittent velocity spikes and eventual flow breakdown.
Area of Science:
- Fluid dynamics
- Aerodynamics
- Boundary layer theory
Background:
- Understanding boundary layer transition is crucial for aerodynamic efficiency.
- Stationary crossflow vortices are a key feature in swept-wing boundary layers.
- Backward-facing steps can alter flow behavior and potentially induce transition.
Purpose of the Study:
- To investigate the effect of backward-facing steps on boundary layer transition.
- To analyze the role of stationary crossflow vortices and unsteady disturbances.
- To determine the influence of step height on transition mechanisms.
Main Methods:
- Experimental measurements using hot-wire anemometry.
- Testing on a swept flat-plate model with an airfoil leading edge.
- Imposing chordwise pressure gradients and varying step heights (36-49% of boundary layer thickness).
Main Results:
- Backward-facing steps had a localized effect on stationary crossflow vortex growth.
- Unsteady disturbance amplitudes increased with step height.
- Intermittent velocity spikes appeared for larger step heights, indicating transition.
- Nonlinear interactions between instabilities and vortices drove transition.
Conclusions:
- Unsteady disturbances are the primary drivers of transition in this scenario.
- Stationary crossflow vortices play a significant role by modulating and amplifying unsteady disturbances.
- Backward-facing steps, particularly critical ones, can cause sudden shifts in the transition front.
More Related Videos
Related Concept Videos
01:18Boundary Layer Characteristics
484
When a fluid encounters a solid surface, a boundary layer forms due to the interaction between the fluid's motion and the stationary surface. This phenomenon is characterized by a thin region adjacent to the surface where viscous forces dominate, influencing the fluid's velocity profile. The development of the boundary layer begins at the leading edge of the surface and evolves as the fluid moves downstream.As the fluid flows over the surface, friction between the fluid and the wall slows down...
484
01:23Lift
443
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...
443
01:16Bernoulli's Equation for Flow Normal to a Streamline
1.2K
Bernoulli's equation for flow normal to a streamline explains how pressure varies across curved streamlines due to the outward centrifugal forces induced by the fluid's curvature. The pressure is higher on the inner side of the curve, near the center of curvature, and decreases outward to balance these centrifugal forces.
The pressure difference depends on the fluid's velocity and radius of curvature. The pressure variation is minimal in flows with nearly straight streamlines. However, the...
The pressure difference depends on the fluid's velocity and radius of curvature. The pressure variation is minimal in flows with nearly straight streamlines. However, the...
1.2K
01:30Bernoulli's Equation for Flow Along a Streamline
1.4K
Bernoulli's equation relates the energy conservation in a fluid moving along a streamline. The equation applies to incompressible and inviscid fluids under steady flow. For such a flow, Newton's second law is applied to a small fluid element, which experiences forces due to pressure differences, gravity, and velocity variations. The force balance leads to the following form of Bernoulli's equation:
1.4K
01:17Steady, Laminar Flow Between Parallel Plates
743
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.
743
01:07Laminar and Turbulent Flow
10.4K
Fluid dynamics is the study of fluids in motion. Velocity vectors are often used to illustrate fluid motion in applications like meteorology. For example, wind—the fluid motion of air in the atmosphere—can be represented by vectors indicating the speed and direction of the wind at any given point on a map. Another method for representing fluid motion is a streamline. A streamline represents the path of a small volume of fluid as it flows. When the flow pattern changes with time, the...
10.4K