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1. Gekle, Stephan. Impact on liquids : void collapse and jet formation.

Degree: Faculty of Science and Technology, 2009, University of Twente

A spectacular example of free surface flow is the impact of a solid object on a liquid: At impact a “crown” splash is created and a surface cavity (void) emerges which immediately starts to collapse due to the hydrostatic pressure of the surrounding liquid. Eventually the cavity closes in a single point about halfway down its length and shoots out a fast and extremely slender water jet. Here we impact thin circular discs a few centimeters in radius with velocities of a few meters per second. Combining high-speed imaging with sophisticated boundary-integral simulations we elucidate various aspects of this fascinating process. First we show that the mechanism behind the formation of the fast, almost needle-like liquid jet is reminiscent of the violent jets of fluidized metal created during the explosion “of lined cavities” in military and mining operations. We obtain quantitative agreement between our simulations, experiments, and analytical model. Next we use visualization experiments to measure the air flow as it is squeezed out of the shrinking impact cavity. Together with numerical simulations we show that even in our simple system of a 2 cm disc impacting at merely 1 m/s the air flow easily attains supersonic velocities. A long-standing controversy in the fluid dynamics community has been until recently the pinch-off behavior of a bubble inside a liquid. Our observation of different time scales for the onset of the predicted final regime reconciles the different views expressed in recent literature about bubble pinch-off. Next we replace the impacting disc by a long, smooth cylinder and find that the closure position of the cavity displays distinct regimes separated by discrete jumps which are consistently observed in experiment and numerical simulations. Finally, we simulate the collapse of nanobubbles nucleating from small (50 nm) pits drilled into a silicon wafer. We find that just prior to final collapse a jet very similar in appearance to those after solid object impact forms and penetrates deep into the hole. Advisors/Committee Members: Lohse, Detlef, van der Meer, Devaraj, Physics of Fluids.

Subjects/Keywords: IR-68374

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APA (6th Edition):

Gekle, S. (2009). Impact on liquids : void collapse and jet formation. (Doctoral Dissertation). University of Twente. Retrieved from https://research.utwente.nl/en/publications/impact-on-liquids – void-collapse-and-jet-formation(2314e104-93f6-49a6-a068-5c3bc579928d).html ; urn:nbn:nl:ui:28-68374 ; 2314e104-93f6-49a6-a068-5c3bc579928d ; 10.3990/1.9789036529297 ; urn:isbn:9789036529297 ; urn:nbn:nl:ui:28-68374 ; https://research.utwente.nl/en/publications/impact-on-liquids – void-collapse-and-jet-formation(2314e104-93f6-49a6-a068-5c3bc579928d).html

Chicago Manual of Style (16th Edition):

Gekle, Stephan. “Impact on liquids : void collapse and jet formation.” 2009. Doctoral Dissertation, University of Twente. Accessed July 07, 2020. https://research.utwente.nl/en/publications/impact-on-liquids – void-collapse-and-jet-formation(2314e104-93f6-49a6-a068-5c3bc579928d).html ; urn:nbn:nl:ui:28-68374 ; 2314e104-93f6-49a6-a068-5c3bc579928d ; 10.3990/1.9789036529297 ; urn:isbn:9789036529297 ; urn:nbn:nl:ui:28-68374 ; https://research.utwente.nl/en/publications/impact-on-liquids – void-collapse-and-jet-formation(2314e104-93f6-49a6-a068-5c3bc579928d).html.

MLA Handbook (7th Edition):

Gekle, Stephan. “Impact on liquids : void collapse and jet formation.” 2009. Web. 07 Jul 2020.

Vancouver:

Gekle S. Impact on liquids : void collapse and jet formation. [Internet] [Doctoral dissertation]. University of Twente; 2009. [cited 2020 Jul 07]. Available from: https://research.utwente.nl/en/publications/impact-on-liquids – void-collapse-and-jet-formation(2314e104-93f6-49a6-a068-5c3bc579928d).html ; urn:nbn:nl:ui:28-68374 ; 2314e104-93f6-49a6-a068-5c3bc579928d ; 10.3990/1.9789036529297 ; urn:isbn:9789036529297 ; urn:nbn:nl:ui:28-68374 ; https://research.utwente.nl/en/publications/impact-on-liquids – void-collapse-and-jet-formation(2314e104-93f6-49a6-a068-5c3bc579928d).html.

Council of Science Editors:

Gekle S. Impact on liquids : void collapse and jet formation. [Doctoral Dissertation]. University of Twente; 2009. Available from: https://research.utwente.nl/en/publications/impact-on-liquids – void-collapse-and-jet-formation(2314e104-93f6-49a6-a068-5c3bc579928d).html ; urn:nbn:nl:ui:28-68374 ; 2314e104-93f6-49a6-a068-5c3bc579928d ; 10.3990/1.9789036529297 ; urn:isbn:9789036529297 ; urn:nbn:nl:ui:28-68374 ; https://research.utwente.nl/en/publications/impact-on-liquids – void-collapse-and-jet-formation(2314e104-93f6-49a6-a068-5c3bc579928d).html

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