Related Experiment Video
Updated: Nov 8, 2025
08:53
The Measurement of Unsteady Surface Pressure Using a Remote Microphone Probe
Published on: December 3, 2016
7.2K
Receptivity and Forced Response to Acoustic Disturbances in High-Speed Boundary Layers
P Balakumar1, Rudolph A King1, Amanda Chou1
1NASA Langley Research Center, Hampton, Virginia 23681.
AIAA Journal. American Institute of Aeronautics and Astronautics
|April 19, 2021
Summary
Supersonic boundary-layer receptivity was studied using Navier-Stokes equations. Acoustic disturbances amplified within the boundary layer, with amplitudes up to 2.5 times larger than the incoming field.
Area of Science:
- Fluid Dynamics
- Aerodynamics
- Acoustics
Background:
- Supersonic boundary layers are sensitive to freestream disturbances.
- Understanding receptivity is crucial for predicting flow behavior and performance.
Purpose of the Study:
- Investigate supersonic boundary-layer receptivity to acoustic disturbances.
- Analyze the generation and amplification of perturbations within the boundary layer.
Main Methods:
- Solved Navier-Stokes equations for Mach 3.5 flow over a cone.
- Generated freestream acoustic disturbances using a wavy nozzle wall.
- Utilized linearized Euler equations to model acoustic radiation.
Main Results:
- Oblique impingement of acoustic disturbances did not generate noticeable instability modes.
- Boundary layer perturbations were a direct response to external acoustic forcing.
- Amplification factors of 2.5 and 1.5 were observed for zero and large azimuthal wave numbers, respectively.
Conclusions:
- The supersonic boundary layer exhibits forced response to acoustic disturbances.
- The amplitude of internal perturbations significantly exceeds the incoming acoustic field.
- Azimuthal wave number influences the amplification of forced disturbances.
More Related Videos
Related Concept Videos
01:18Boundary Layer Characteristics
309
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...
309
01:07Reflection of Waves
4.2K
When a wave travels from one medium to another, it gets reflected at the boundary of the second medium. A common example of this is when a person yells at a distance from a cliff and hears the echo of their voice. The sound waves (longitudinal waves) traveling in the air are reflected from the bounding cliff. Similarly, flipping one end of a string whose other end is tied to a wall causes a pulse (transverse wave) to travel through the string, which gets reflected upon reaching the wall. In...
4.2K
01:09Deriving the Speed of Sound in a Liquid
729
As with waves on a string, the speed of sound or a mechanical wave in a fluid depends on the fluid's elastic modulus and inertia. The two relevant physical quantities are the bulk modulus and the density of the material. Indeed, it turns out that the relationship between speed and the bulk modulus and density in fluids is the same as that between the speed and the Young's modulus and density in solids.
The speed of sound in fluids can be derived by considering a mechanical wave...
The speed of sound in fluids can be derived by considering a mechanical wave...
729
01:16Shock Waves
2.2K
While deriving the Doppler formula for the observed frequency of a sound wave, it is assumed that the speed of sound in the medium is greater than the source's speed through it. When this condition is breached, a shock wave occurs.
When the source's speed approaches the speed of sound, constructive interference between successive wavefronts emitted by the source occurs immediately behind it. Initially, scientists believed that this constructive interference would result in such high...
When the source's speed approaches the speed of sound, constructive interference between successive wavefronts emitted by the source occurs immediately behind it. Initially, scientists believed that this constructive interference would result in such high...
2.2K
01:14Sound Waves: Resonance
2.9K
Resonance is produced depending on the boundary conditions imposed on a wave. Resonance can be produced in a string under tension with symmetrical boundary conditions (i.e., has a node at each end). A node is defined as a fixed point where the string does not move. The symmetrical boundary conditions result in some frequencies resonating and producing standing waves, while other frequencies interfere destructively. Sound waves can resonate in a hollow tube, and the frequencies of the sound...
2.9K
01:16Electrostatic Boundary Conditions
725
Consider an external electric field propagating through a homogeneous medium. When the electric field crosses the surface boundary of the medium, it undergoes a discontinuity. The electric field can be resolved into normal and tangential components. The amount by which the field changes at any boundary is given by the difference between the field components above and below the surface boundary.
The surface integral of an electric field is given by Gauss's law in integral form and is related to...
The surface integral of an electric field is given by Gauss's law in integral form and is related to...
725