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Cavitation By Justin Lilly What is Cavitation? “The sudden formation and collapse of lowpressure bubbles in liquids by means of mechanical forces” – American Heritage College Dictionary This process usually produces a sound when the bubbles collapse How Does it Work? Cavitation takes place when the local ambient pressure of the liquid falls below the vapor pressure of that liquid at its local ambient temperature. Props cause this to happen because of the pressure changes that take place when a fluid flows around a solid object. Sound waves can also cause cavitation by the resulting shockwave from when two different sources of sound collide. This also occurs when sound waves strike a solid object. Where these bubbles collapse, temperatures reach 5000K and pressures of the order of 500 to 1,000 atm have been estimated. Beneficial Uses of Cavitation Cavitation, when employed in special ways, can aide in the following: 1) Degredation/destructio n of VOCs 2) Dissolve NORMs 3) Cleaning/dissolution of oil spills 4) Killing of plankton Beneficial Uses of Cavitation (1) VOCs are Volatile Organic Compounds. Benzene, Methylene, Formaldehyde are examples of VOCs These chemicals come from paints, varnishes, gasoline, solvents, cleaning chemicals, oil refineries, vehicle exhaust Health effects include: headaches, nausea, dizziness, cancer, liver damage, kidney damage, CNS damage Lab tests have indicated that using Acoustic Cavitation can partially degrade and/or destroy VOCs. Argonne National Laboratory believes using acoustic cavitation can destroy VOCs and petroleum hydrocarbons at a high rate with minimum contact time. Beneficial Uses of Cavitation (2) NORMS are Naturally Occuring Radioactive Materials. These are materials that have always been present in various concentrations in the Earth’s crust. Some industrial processes cause NORM to be concentrated to harmful levels. NORM is a carcinogen. In the study, Barium Sulfate was used as the NORM tested. Using sonication, It was shown that NORMs can be dissolved to a high percentage. Beneficial Uses of Sonication (3) To clean oil spills, the preferred method is mechanical recovery. This is dependent on things like weather The next best solution is to disperse the oil. Currently, dispersants are used to accomplish this task. Dispersants have other undesirable side effects because they are toxic. Beneficial Uses of Cavitation (3) Beneficial Uses of Cavitation (3) Beneficial Uses of Cavitation (4) Plankton in lakes and ponds can destroy the ecological environment there. Too much plankton in an ecosystem causes a depletion of oxygen in the body of water, which affects other marine creatures. Other Beneficial Uses of Cavitation Sonic cleaners make use of acoustic cavitation (sonication) It can be used as a non-invasive way to destroy kidney stones and has been used for some time experimentally. Cavitation is currently being studied as a way to get large molecules into cells Cavitation brought to a larger scale could be responsible for producing supersonic submersibles. Conclusions Sonication has several beneficial uses: 1) Dispersion/destruction of VOCs 2) Dissolving of NORMs 3) Dissolving of oil spills 4) Destruction of Plankton Also, cavitation also carries the potential to do many other things (such as kidney stone treatment and submarines). Sonic cleaners are currently used in labs that employ the use of cavitation. References “Utilization of Cavitation for Environmental Protection – Killing Plankton and Dispersing Spilled Oil.” Hiroharu KATO, Department. Of Mechanical Engineering, Toyo University. 2001 “The Use of Advanced Acoustic Cavitation for Applications in the Oil and Natural Gas Industry.” Michael Wilkey, Robert Peters, James Furness. Furness-Newburge, Inc (FNI) Versailles, KY. “A Brief Discussion About Naturally Occurring Radioactive Materials (NORM)” Stuart Hunt and Associates Ltd. “Minnesota Department of Health Fact Sheet: Volatile Organic Compounds – VOCs” Minnesota Department of Health Indoor Air Unit. St. Paul, MN. September 2005 “Cavitation and Bubble Dynamics” Christopher Earls Brennen. Oxford University Press. ISBN 0-19-509409-3. 1995 “Lithotripsy (Stone Treatment)” Center for Advanced Urology. Portland, Oregon. Questions?