Multiphase Flows

Multiphase flow is a profound problem of interest to a wide range of engineering, geophysical, and environmental applications. For example, in the fields of medicine and pharmacology, the microbubbles are widely used in enhancing ultrasound contrast for medical ultrasound imaging and delivering of target drugs and genes to tissues. In aquaculture, the microbubbles generated by aeration systems are applied in fish farming and culturing oysters to supply the oxygen and suspend the nutrients, resulting in increment of the production. Breaking waves, bubbles, and droplets play important roles in many physical oceanography processes, including the bubble-mediated air-sea gas transfer, wave energy dissipation, and the production of marine aerosol.

Our research group has performed a systematic study on the fundamental dynamics of bubbles and breaking waves. Firstly, we investigated the bubble generation process using high-fidelity simulations. The bubble fragmentation cascade process is observed and bubble size spectrum shows agreement with theoretical analysis and experimental dataset. An animation of bubble generation process in a breaking wave is shown below.

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Bubble generation under a breaking wave

To identify the bubbles from level set and air fraction fields and calculate their statistics, we have implemented an advanced multi-block paralleled bubble identification algorithm. In addition, we also proposed a robust and accurate algorithm for Lagrangian tracking of bubbles and detecting their time-evolution behaviors. Using these powerful tools, we are able to track individual bubbles and investigate the bubble trajectory, residence time, and their effects on air-sea gas transfer.

Video file
Bubble identification and tagging
Video file
Bubble trajectory

In addition to the breaking wave and bubbly flows, we also perform extensive studies on particle-laden flows, oil spills, cavitation, and fluid-structure interactionIntroductions to these studies can be found by following the links above.

 

Selected Publications:

  • Gao, Q., Shen, L. & Deane, G., “A numerical simulation framework for bubbly flow and sound generation in laboratory-scale breaking waves,” JASA Express Letters, in press.
  • Gao, Q., Deane, G., Liu, H. & Shen, L. (2021), “A robust and accurate technique for Lagrangian tracking of bubbles and drops and detecting fragmentation and coalescence,” International Journal of Multiphase Flow, Vol. 135, 103523.
  • Yang, Z., Deng, B. & Shen, L. (2018), “Direct numerical simulation of wind turbulence over breaking waves,” Journal of Fluid Mechanics, Vol. 850, pp. 120-155.
  • Tang, S., Yang, Z., Liu, C., Dong, Y. & Shen, L. (2017), “Numerical study on the generation and transport of spume droplets in wind over breaking waves,” Atmosphere, Vol. 8(12), 248.
  • Yang, Z., Lu, X., Guo, X., Liu, Y. & Shen, L. (2017), “LES study of sediment suspension and transport under plunging breaking waves,” Computers and Fluids, Vol. 158, pp. 57-71.
  • Hu, Y., Guo, X., Lu, X., Liu, Y., Dalrymple, R.A. & Shen, L. (2012), “Idealized numerical simulation of breaking water wave propagating over a viscous mud layer,” Physics of Fluids, Vol. 24, 112104.