How Ultrasonics Work
How Ultrasonics Work
The Basic Ultrasonic Explanation
Ultrasonics generates vacuum bubbles in a liquid which is known as “Cavitation”. These vacuum bubbles implode at very high pressures and temperatures. This action of millions of “Cavitation” implosions per second has the effect of scrubbing the surface of any object that is immersed in the liquid.
The More Detailed Ultrasonic Explanation
Ultrasonic energy is sound beyond the range of human hearing. Frequencies above 16,000 cycles per second (16 kHz) are generally considered to be ultrasonic.When a sound wave travels through air, the air is compressed and then stretched as the wave passes through. Unlike air, liquids are not elastic an
d cannot stretch in this way. Consequently, if the sound wave is big enough (i.e. has a high enough amplitude relative to its wavelength) it will literally tear the liquid apart, forming extremely small vacuum pockets within the liquid. These vacuum pockets, which are known as cavitation bubbles, act as strain relievers for the liquid. They form during the negative pressure part of the wave, and collapse during the high-pressure part of the wave that follows. However, cavitation bubbles can grow over several waves before collapsing.
When a cavitation bubble collapses, it is literally an implosion in which extremely high pressure and temperature is generated. The high pressure and temperature lasts for a very brief period of time and only in a very small volume within the liquid. The implosion energy derives from a combination of three things:
1. Compression from the ultrasonic wave
2. Compression from surface tension in the bubble
3. Atmospheric pressure on the vacuum
2. Compression from surface tension in the bubble
3. Atmospheric pressure on the vacuum
If there is air suspended in the liquid, then this will tend to be released into the cavitation bubble. In this case it will not be a true vacuum and the strength of the implosion will be greatly reduced.
The action of millions of cavitation implosions per second has the effect of scrubbing the surface of any object that is immersed in the liquid. The scrubbing action acts much more quickly, and on a much finer scale, than any other known means of scrubbing or scouring. Because sound travels through metals and many other materials, the ultrasonic energy will penetrate into blind holes and complex shapes (including surface pores in metals) which cannot be reached by other methods.
The result is faster, more efficient cleaning. Cavitation is often strong enough to break ionic bonds holding insoluble contaminants to a surface. Ultrasound works particularly well with appropriate cleaning chemicals-detergents, surfactants, terpenes, aqueous and non-aqueous compounds, etc.