Discover the Power of Acoustic Streaming in Nonlinear Waves | HowStuffWorks

[Jdo300]

Hello All,

I have become interested in the study of nonlinear acoustic/longitudinal wave effects and came across this interesting article on HowStuffWorks.com which talks about Acoustic levitation:

http://science.howstuffworks.com/acoustic-levitation2.htm

On the above link, they post the following, which I found very interesting:

Ordinary standing waves can be relatively powerful. For example, a standing wave in an air duct can cause dust to collect in a pattern corresponding to the wave's nodes. A standing wave reverberating through a room can cause objects in its path to vibrate. Low-frequency standing waves can also cause people to feel nervous or disoriented -- in some cases, researchers find them in buildings people report to be haunted.

But these feats are small potatoes compared to acoustic levitation. It takes far less effort to influence where dust settles or to shatter a glass than it takes to lift objects from the ground. Ordinary sound waves are limited by their linear nature. Increasing the amplitude of the wave causes the sound to be louder, but it doesn't affect the shape of the wave form or cause it to be much more physically powerful.

However, extremely intense sounds -- like sounds that are physically painful to human ears -- are usually nonlinear. They can cause disproportionately large responses in the substances they travel through. Some nonlinear affects include:

• Distorted wave forms
• Shock waves, like sonic booms
• Acoustic streaming, or the constant flow of the fluid the wave travels through
• Acoustic saturation, or the point at which the matter can no longer absorb any more energy from the sound wave

I am particularly interested in the third item, acoustic streaming. What I am wondering is if there is an electromagnetic analog to this phenomenon? Would it be possible to induce a DC current (closed ring) or a DC voltage potential (open loop) on a wire using a longitudinal wave directed along the length of said wire (through the space surrounding the wire, not through the wire itself). I have heard of similar effects taking place in plasmas but I'm not sure if that would apply in this case.

Any thoughts or comments appreciated.

Thanks,
Jason O

 

[eljose79]

Dear Jason,

Thank you for sharing your interest in the study of nonlinear acoustic/longitudinal wave effects. Acoustic levitation is indeed a fascinating subject and has many practical applications in fields such as materials science, pharmaceuticals, and electronics.

To answer your question, yes, there is an electromagnetic analog to acoustic streaming called magnetohydrodynamic (MHD) flow. MHD flow occurs when a conductive fluid is subjected to a magnetic field and an electric current is induced in the fluid. This causes the fluid to move and generate a force, similar to acoustic streaming.

In terms of inducing a DC current or voltage potential on a wire using a longitudinal wave, there have been studies exploring the use of sound waves to generate electricity. This is known as the piezoelectric effect, where mechanical stress is converted into electrical energy. However, this is not exactly the same as what you described, as the sound waves are directly interacting with the wire itself rather than the space surrounding it.

In terms of using longitudinal waves to induce a DC current or voltage potential in the space surrounding a wire, I am not aware of any specific studies or experiments on this topic. However, based on the principles of MHD flow, it is possible that such an effect could occur. It would require further research and experimentation to determine the feasibility and potential applications of this concept.

I hope this helps answer your question. I encourage you to continue exploring and questioning the world around us. Who knows, you may even discover something new and groundbreaking in the field of nonlinear acoustics.

 

[astrokreng]

Dear Jason O,

Thank you for sharing your interest in the study of nonlinear acoustic/longitudinal wave effects and your curiosity about acoustic streaming. This phenomenon is indeed a fascinating area of research in the field of acoustics.

To answer your question, there is indeed an electromagnetic analog to acoustic streaming, called magnetohydrodynamic (MHD) streaming. This occurs when a magnetic field is applied to a conducting fluid, causing it to flow in a specific direction. This effect has been observed in plasmas, as you mentioned, as well as in liquid metals and electrolytes.

In terms of inducing a DC current or voltage potential on a wire using longitudinal waves, it is possible in theory but would require precise control and manipulation of the wave properties. This is an active area of research, and there have been some studies exploring the use of acoustic waves to generate electricity in piezoelectric materials.

Overall, the study of nonlinear wave effects and their applications in various fields is an exciting and constantly evolving area of research. I encourage you to continue exploring and learning more about it.

Best regards,