Here, we will combine numerical simulation and experiments to unravel the complex flow created by non-spherical oscillating bubbles and the thereby created forces on the boundary. In particular we will quantify the shear stress acting spatially and time-dependent on the substrate. To connect better to applications we will not only focus on a flat substrate but also extend our studies to decorated surfaces.
The PI’s group conducted the first experiments to measure the shear stress back in 2008 (Dijkink et al., Appl. Phys. Lett 2008). There, single laser induced bubbles revealed a lower bound of the wall shear stress (e.g. the tangential force) of several thousand kilopascals. Recent simulations from his group predict that the wall shear stress may be locally even an order of magnitude higher than measured.
The first goal of the present project is to provide conclusive answers for the time-dependent magnitude and distribution of the wall shear stress. A second goal is to model and measure the forces acting on surfaces with structures to provide insight to more application relevant situations. The third part is the extension of the studies acoustic driven cavitation, i.e. to many cycles of bubbles approaching a surface.
The deliverables of the project are: (1) to develop a novel technique to measure simultaneously temporally and spatially resolved the wall shear stress, (2) detailed understanding how bubbles create viscosity mediated forces on boundaries, and (3) experimentally validated simulations which will be made available to the public by using the OpenFOAM framework.