Bubble dynamics can also be explained using the Russian turbulence theory, first proposed in 1941.

In a groundbreaking experiment, a team of researchers led by Dr. Andrew Bragg from Duke University and Dr. Hendrik Hessenkemper from HZDR have made significant strides in understanding the behaviour of turbulence in bubble-induced flows.

The researchers conducted the experiment using a water column filled with bubbles, created in a controlled manner. The bubbles used had diameters between three and five millimeters. They tracked both the bubbles and tiny marker particles in the water using a modern 3D tracking method, and captured images at a rate of approximately 2500 frames per second using high-speed cameras.

Outside the wakes of the bubbles, the turbulence behaved similarly to classical wind tunnel experiments. However, within the wakes, the flow is disrupted, with the vortices being particularly strong and irregular, preventing the formation of a classical energy cascade.

The researchers developed a model to better understand how quickly turbulence loses its energy. They found that the energy loss does not depend only on the size of the bubbles but also on the distance between them. If many bubbles rise simultaneously, the vortices reinforce each other, while if the bubbles are further apart, they weaken less.

The findings of the experiment showed that Kolmogorov's theory matched the turbulence in two out of four cases studied, especially for vortices smaller than the bubbles themselves. The classical Kolmogorov scaling of 1941 occurs in bubble-induced turbulence, mainly outside the direct wakes of the bubbles and for vortices smaller than the bubbles themselves.

The robustness of Kolmogorov's theory in bubble-induced turbulence surprises many experts. The researchers collaborated with the Technische Universität Dortmund, Brandenburgische Technische Universität Cottbus-Senftenberg, and Technische Universität Braunschweig, and their findings are useful for optimizing processes where bubbles play a role, such as chemical reactors, wastewater treatment facilities, and climate models.

The better understanding of the basic rules of turbulence in bubble flows can help in real-world applications. The experiment confirms Kolmogorov's 1941 turbulence theory as applicable to bubble-induced turbulence, and goes beyond fundamental physics, having implications for technology and science. The findings aid technology and climate research, providing valuable insights for future studies in this field.