Sonic Cavitation in Water

Source: 20170911-infinity-supercritical-cavitation-water-review

Source: Darner, C. L. (1970). Sonic cavitation in water (No. NRL-7131). NAVAL RESEARCH LAB WASHINGTON DC.

An introduction is given to talk a little bit about water. The point being, water is quite complex and if we didn’t interact with it everyday, it’s properties compared to other liquids would be rather outstanding.

Moving past that, the point of the report is to document a way to suppress sonic cavitation in water, a problem that is of interest of many naval communities.

Originally, back in the 1700s, Euler anticipated difficulties due to the areas of low pressure caused by turbines. He saw that they could cause bubbles which lower resistance and thus thrust. Later on, we found that there was also damage to the metal turbine as well. When the steam turbine was created, these two issues arose. There was a decrease in the increase of thrust with increasing propeller shaft speed. Also, the propellers were being eaten away rather quickly. It was found that this was due to the collapsing bubbles formed due to the low- pressure areas. Indeed, pressures over 400,000 psi can be found due to cavitation.

When high-power sonar is being used, similar problems arise. Cavitation happens and efficiency drops rapidly as acoustic intensity increases. Also, there is rapid mechanical destruction of the transducer.

Pure water in this report is considered distilled water. Even after distillation, contaminates still remain. If any water is even exposed to atmosphere with no mixing, CO2 in introduced and lowers the pH to ~5.5.

There are some laboratory methods to inhibit cavitation. These include maintaining a low pressure (44 to 58 psi) or after the application and then release of pressure around 15,000 psi. Another method to inhibit cavitation is to filter micro-sized particulate or to degas the water. To investigate the degassing of the water, a large tank was built and steel was introduced to allow it to rust. A piece of wood floated at the top to stop the reintroduction of oxygen. As the iron rusted and consumed the oxygen, a sound source was put at one end and the power required to induce cavitation was recorded. As the oxygen saturation lowered (down to 35 percentage from 100), the power had to be increased.

After the oxygen saturation reached 2 percentage and the total gas content down to 67 percentage, the power required to induce cavitation still increased. The increase from just deoxygenation was around 2 fold, while after letting the water sit past this, it allowed for up to 8 fold increases in power.

It seems that resting dexoygenated water seems to lead to an increasing “strength” against cavitation, while it was not seen with “regular” water. This “resting” was found to increase the power required by up to 10 fold.

This was found to be due to hydrogen being introduced into the system through the rusting process of the steel. When the process was repeated while introducing hydrogen into the water as well, the water withstood cavitation up to 36 fold the original amount.

When investigating the cohesiveness of the “strong” water, it was found that it took 40 drops of the treated water to make 1 cubic centimeter, but only 20 drops of untreated water.

It was also found that some dilute high- molecular-weight polymer solutions help to reduce cavitation.

One such polymer, polyethylene oxide, was able to increase the cavitation resistance by up to 8 fold. This however was reversed over time, due to the fact that it continued to fall out of solution and precipitate on the glass and sound producer.

Some other ways to cause these solutions (or seen by ships navigating at sea) is through algae that exude a polysaccharide that when in the water, increases resistance to cavitation.

When these algae were added to the tank, a resistance to cavitation by up to 10 fold was found. After removing the algae and boiling off the water, a solute of 2.5 grams/liter remained. When just the compound was re- introduced, the cavitation resistance returned. Adding more solute did not change the resistance however.

Different algae seem to produce different polysaccharides, some that produce this increase in resistance of 10 fold at concentrations of 0.25 grams/liter.

The paper concludes that the deoxygenation method (which also produces hydrogen) seems to be the best method for use inside a sonar dome. The issue being that cavitation starts to occur outside the dome past the increase in resistance. Thus, the polymer produced by the algae could be used if cheap enough, since it could be slowly leaked outside the sonar dome continuously, allowing for a higher original power due to a resistance to cavitation also outside the dome.

The paper has an appendix that seems to be of interest. It goes over the physics and chemistry of water.

Surprisingly, when looking at the other hydrides of the 6th main group of elements, (H2Te, H2Se, and H2S), they produce a rather good trend for reducing boiling and freezing points. They are also all colorless, pungent, and poisonous gases. However, the extrapolated value for the boiling-freezing point for water is not only wrong, the correct values are nearly twice these values.

Another surprising quality of water is the presence of “heavy” water (deuterium oxide) which is oxygen bonded to two hydrogens, both with an extra neutron bound to the proton. This type of water is not biologically active, and has numerous different qualities. It’s in concentrations of around 150-200ppm in natural water. There is also tritium (hydrogen with two neutrons) which can also form an oxide with oxygen.

This, along with the other isotopes of oxygen, allow for a total of 18 different molecular compounds. However, most are quite low in concentrations. On top of this, there are H+ and OH- ions found in pure water.

Water can also be superheated and supercooled. These events can be seen by slowly heating or slowly cooling water free of impurities and gases. People have been able to reduce water’s temperature to -4 degrees Fahrenheit before it froze. Small mechanical bumps can shock the system into the next physical state.

Another interesting behavior is that at low temperatures, the viscosity of water decreases with increasing hydrostatic pressure, while most other fluid’s viscosity’s increase with pressure.

Possibly the most striking quality of water is it’s hydrogen bond. Due to the bend in the

molecule, the positive charges of the protons (hydrogen), and the pull from the oxygen of the electrons, a strong dipole moment is achieved. The side of the oxygen has a strong negative charge that with form a hydrogen bond with other hydrogens who have their electrons pulled.

This could be from water, or from many other molecules. This bond is what allows for the increase in the extrapolated boiling-freezing point, as each molecule of H2O is strongly attached to one another.

Ice also has some interesting qualities. Different forms of ice form under different temperatures, pressures, and other conditions. Some of these have densities that don’t float in liquid water.

End of review.

Controlled Cavitation of Water In Engineering and Agricultural Applications

Review: 20170911-infinity-supercritical-controlled-cavitation-agricultural-review

Source: Dyussenov, K. M., Dyussenova, J., & Nedugov, I. (2013). The Using of Controlled Cavitation Processes in Some Engineering and Agricultural Applications. Universal Journal of Engineering Science, 1 (3), 89-94.

The article, “The Using of Controlled Cavitation Processes in Some Engineering and Agricultural Applications” is probably the worst scholarly article ever read. It’s as if someone just wrote the article in another language and then used Google Translate. That is on top of the fact that I don’t believe in any of the data. It’s on the edge of pushing water structuring psuedo science (water structuring is a real thing, but there is no real data to support that you can keep water structured without some constant influence like an electric field or ultrasonic waves.

They suggest that after an ultrasonic treatment that the water is structured differently and thus increase the yields in their plants. While there may be some real benefits, (disinfection, better mixing of metals, etc) it’s laughable to suggest that cavitation can cause nano-structuring for a lasting period of time.). If you’ve ever heard of China making fake science articles to increase publications and thus “legitimacy”, this is it.

Read with caution. The water heating part I mostly trust (besides the pH impact, they state the Venturi nozzle decreases pH by up to 15%).

Review of Publication:

Hydrodynamic and ultrasonic cavitation have wide uses from medicine, naval applications, chemical technologies, cosmetics, and more. The thermodynamics behind hydrodynamic cavitation give rise to the complex effects of cavitation. It leads to sono-luminescene, water ionization, extreme mixing, de- aeration, and structural changes in the water.

Hydrodynamic cavitation also can be used to heat water, make mixes of biodiesel and ethanol, and be used as a disinfectant.

Its use as a disinfectant and ability to nano structure water, can help in the growth of various plants, as shown later in this paper.

One way to use cavitation as a heat generator is to use a Venturi nozzle with a fragment to help mix the flow. The flow reduces in pressure as it gains fluid velocity and under goes cavitation.

The heat given off by these nozzles is evenly mixed due to the fragment and these nozzles can heat fluids with up to 98% efficiency. They also don’t require an electric or flame heat source which increases safety when in use in the preparation of fuel.

These types of heat generators perform as reliably as the motor and pump that directs the flow.

When using a Venturi nozzle to induce hydrodynamic cavitation in water being used to irrigate pine trees, there was a seen increase in their resistibility to pathogenic micro flora.

The water itself saw a decrease in conductivity from 18 to 23 percentage along with an decrease in the pH by 25 to 35 percentage.

Water then used in the growing of tomato and rose plants were then treated with a piezoeletric converter. This used ultrasonic frequencies to cause cavitation in the water. Frequencies between 20 and 50 Hz and 20 and 50 kHz were investigated.

20 kHz seemed to be the best way to treat the water.

It increased productivity of the tomato plants by up to 15 percentage and increased the root systems of the roses by up to 40 percentage.

These values correlated with an increase in the plant’s content of copper by 52 percentage, zinc by almost 70 times, tin by almost 8 times and cadmium by 3.9 times.

The 20 kHz treated water showed an increase in acidity by 1.14 to 2.01 percentage and the 50kHz saw an increase of 3.28 percentage.

These differences were attributed to the ultrasonic cavitation causing partial ionization of the water and causing molecular structuring.

There was also an increase in the how long the plants lasted under the 20kHz treatment.

It is suggested that the ultrasonic radiation can influence the physical and chemical properties of the water to some extent.

Biotechnology could also use cavitation to attack certain issues caused by hydrophilic and hydrophobic structures due to it’s high mixing.

It is suggested due to the low power consumption and reliability, that if these water treatments were taken into the field, a large increase in productivity could be seen.

End of publication review.