University of Twente Student Theses


Electrocavitation in nanochannels

Schoot, D.S. van (2012) Electrocavitation in nanochannels.

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Abstract:Cavitation in water has been the subject of research for centuries. This thesis investigates a novel method for cavitation that was dubbed electrocavitation. It employs concepts of nanofluidics to create a platform to study cavitation that can be easily controlled and where cavitation can be reliably generated. It works by applying a voltage axially over a nanochannel where a conductivity step is present in the solution. This generates a tension in the solution which, at sufficiently low pressures, causes it to cavitate. The advantages of this setup over traditional methods of cavitation are that it is less cumbersome, more reliable and predictable and able to reach very high negative pressures. This thesis focusses both on the technical aspects of this method as well as the theoretical framework to interpret the cavitation experiments. First of all, an already existing setup is enhanced and upgraded to include electrical current measurements in the determination of cavitation experiment characteristics. These are the immediately employed in measurements. A theoretical framework is also provided to understand all the measurement results and make predictions about the measurements, including a part about the fundamentals of cavitation in general. With the help of the electrical current data a new set of measurements could be performed. One of the most important ones is a determination of the ζ-potential, an important quantity in nanofluidics in general and in electrocavitation in particular. This in turn is used to calculate the pressure everywhere in the channel during the electrocavitation experiment. It could then be proved that the position of cavitation coincides with the position of the front between the two solutions used for cavitation. The cavitation location moves over time and eventually disappears, suggesting the pressure at that moment is not low enough to make the solution cavitate. It is concluded that a reliable platform has been developed for cavitation experiments. It has potential to reach very low pressures and thereby tell new things about the behaviour of salty aqueous solutions. It can be further used to investigate for example the structure of water in salty solutions with use of the Hofmeister series.
Item Type:Essay (Master)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:53 electrotechnology
Programme:Electrical Engineering MSc (60353)
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