Ultrasonic Cleaning - Why You Should Care (3)
Ultrasonic Cleaning - Why You Should Care
Part Three:
What exactly is "Ultrasonic"?
In Latin, the prefix "Ultra" means "beyond." "Sonic" refers to the nature of sound or sound waves; thus, we "Ultrasonic" means beyond sound - faster than sound.
Ultrasonic Cleaning - the Physics of Cavitation
Ultrasonic Cleaning uses a physical phenomenon that takes advantage of rapid changes of pressure in a liquid; cavitation. This phenomenon occurs when the low pressure areas form small vapor-filled bubbles (also known as "voids"). The low pressure areas are created from the ultrasonic waves that the transducer emits. The bubbles created collapse under the immense pressure of the surrounding liquid, creating a shockwave through the process known as "inertial cavitation."
Cavitation Inception (how it is initiated) happens when the pressure of the liquid medium falls lower than its gas state. In order for cavitation inception to take place, there usually needs to be a medium where these microscopic bubbles (cavitation nuclei) can nucleate; grow and produce observable vapor bubbles. This can be anything that is not inherently part of the liquid, including the container (of the liquid) itself, impurity particles in the liquid, or even other bubbles.
The relationship between the pressure of the liquid and the pressure of its gas state is denoted by the following formula:
σ is the cavitation number, the potential for cavitation to occur.
Of the liquid/flow: U∞ is reference velocity. p∞ is pressure. T∞ is temperature. ρL is the liquid density. pV (T∞) is the saturated vapor pressure.
For reference, the lower σ is, the size and quantity of the vapor bubbles increase. When cavitation takes place, it is common for σ to be a negative value.
tl;dr:
When the water gets disturbed by the transducer, changes in pressure takes place. The areas with low pressure create microscopic bubbles which then grow and collapse, creating a shockwave.
The Transducer
There are two main types of transducers when it comes to Ultrasonic Cleaning: Piezoelectric and Magnetostrictive.
Piezoelectric transducers are made from lead zirconate titanate, a crystal that reacts to electricity. When an electrical current is sent through this material, the crystal rapidly changes shape and expands. Of course, it retains its shape after the current stops. This material is perfect for the use of an Ultrasonic Cleaning transducer, providing the flexibility in its resonance and its durability.
Magnetostrictive transducers operate when iron-rich metals warp under magnetic fields. The iron metal core is enwrapped in copper wiring. This assembly is then contained in a canister; the transducer.
Evidently, the Piezoelectric transducer is simpler, and therefore is more common in Ultrasonic Cleaners.
Cavitation that occurs elsewhere...
This phenomenon also takes place in the propellors of aquatic vehicles, mantis/pistol shrimps' killing mechanisms, vascular plants, and more!
I find it super interesting that engineers were able to take a phenomenon with such diversity in its happenings to apply it to the industry.
What exactly is "Ultrasonic"?
In Latin, the prefix "Ultra" means "beyond." "Sonic" refers to the nature of sound or sound waves; thus, we "Ultrasonic" means beyond sound - faster than sound.
Ultrasonic Cleaning - the Physics of Cavitation
Ultrasonic Cleaning uses a physical phenomenon that takes advantage of rapid changes of pressure in a liquid; cavitation. This phenomenon occurs when the low pressure areas form small vapor-filled bubbles (also known as "voids"). The low pressure areas are created from the ultrasonic waves that the transducer emits. The bubbles created collapse under the immense pressure of the surrounding liquid, creating a shockwave through the process known as "inertial cavitation."
Cavitation Inception (how it is initiated) happens when the pressure of the liquid medium falls lower than its gas state. In order for cavitation inception to take place, there usually needs to be a medium where these microscopic bubbles (cavitation nuclei) can nucleate; grow and produce observable vapor bubbles. This can be anything that is not inherently part of the liquid, including the container (of the liquid) itself, impurity particles in the liquid, or even other bubbles.
The relationship between the pressure of the liquid and the pressure of its gas state is denoted by the following formula:
σ is the cavitation number, the potential for cavitation to occur.
Of the liquid/flow: U∞ is reference velocity. p∞ is pressure. T∞ is temperature. ρL is the liquid density. pV (T∞) is the saturated vapor pressure.
For reference, the lower σ is, the size and quantity of the vapor bubbles increase. When cavitation takes place, it is common for σ to be a negative value.
tl;dr:
When the water gets disturbed by the transducer, changes in pressure takes place. The areas with low pressure create microscopic bubbles which then grow and collapse, creating a shockwave.
The Transducer
There are two main types of transducers when it comes to Ultrasonic Cleaning: Piezoelectric and Magnetostrictive.
Piezoelectric transducers are made from lead zirconate titanate, a crystal that reacts to electricity. When an electrical current is sent through this material, the crystal rapidly changes shape and expands. Of course, it retains its shape after the current stops. This material is perfect for the use of an Ultrasonic Cleaning transducer, providing the flexibility in its resonance and its durability.
Magnetostrictive transducers operate when iron-rich metals warp under magnetic fields. The iron metal core is enwrapped in copper wiring. This assembly is then contained in a canister; the transducer.
Evidently, the Piezoelectric transducer is simpler, and therefore is more common in Ultrasonic Cleaners.
Cavitation that occurs elsewhere...
This phenomenon also takes place in the propellors of aquatic vehicles, mantis/pistol shrimps' killing mechanisms, vascular plants, and more!
I find it super interesting that engineers were able to take a phenomenon with such diversity in its happenings to apply it to the industry.
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