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When swarms of bubbles are pushed upward through a fluid from their buoyancy, they can generate complex flow patterns in their wake. Called “pseudo-turbulence”, these models are characterized by a universal mathematical relationship between the energy of flows of different sizes and the frequency of their occurrence. This relationship has now been widely observed through 3D simulations, but it is less clear whether it would still hold true for 2D swarms of bubbles. Through a research published in EPJ E, Rashmi Ramadugu and colleagues from the TIFR Center for Interdisciplinary Sciences in Hyderabad, India show that in 2D simulated fluids, this pattern changes within large-scale flows into less viscous fluids.
The team’s findings relate to key oversight in fluid dynamics simulations and could allow researchers in areas from oceanography to acoustics to improve their predictions. In the past, many pseudo-turbulence studies have found that the statistical properties of 3D bubble swarms remain universal over a wide range of bubble surface tensions, fluid viscosities, and bubble-to-fluid density ratios. In 2D fluids, however, an effect called “reverse energy cascade” allows for the transfer of energy from small and large streams. In their study, Ramadugu’s team aimed to investigate the implications of this mechanism for the first time.
The researchers obtained their results through a simulation approach that takes full account of turbulent flows at all scales in space and time, eliminating the need for them to approximate any unpredictable behavior. They found that while the usual pseudo-turbulence relationship holds on larger scales within more viscous fluids; and on smaller scales in less viscous fluids, different behaviors can be found in large-scale flows within more viscous fluids. Here, Ramadugu and colleagues found that a reverse energy cascade occurs in the wake of the bubble swarm; as well as a different mathematical relationship between flow energy and frequency than any previously observed.
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Journal reference:
- Rashmi Ramadugu, Vikash Pandey, Prasad Perlekar. Pseudo-turbulence in two-dimensional buoyancy-driven foaming flows: a DNS study. The European Physical Journal E, 2020; 43 (11) DOI: 10.1140 / epje / i2020-11997-0
Cite this page:
Springer. “Characterization of Complex Flows in 2D Bubble Swarms.” ScienceDaily. ScienceDaily, December 4, 2020.
Springer. (2020, December 4). Characterization of complex flows in 2D bubble swarms. ScienceDaily. Retrieved December 4, 2020 from www.sciencedaily.com/releases/2020/12/201204110158.htm
Springer. “Characterization of Complex Flows in 2D Bubble Swarms.” ScienceDaily. www.sciencedaily.com/releases/2020/12/201204110158.htm (accessed on 4 December 2020).
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