Cavitation is defined as the breakdown of a liquid medium and occurrence of cavities and is of high importance in a wide range of applications from engineering (turbomachinery) to medicine (lithotripsy).
Leading edge cavitation (left) and cavitating Karman vortices (right) in a water flow over a 2-D hydrofoil (Farhat et. al., 2001)
To avoid and to exploit
In collabporation with the Laboratory for Hydraulic Machinery (Prof. Avellan, EPFL) we conduct a computational/experimental study of cavitation in hydraulic turbomachinery responsible for operating instabilities, erosion, noise and vibration. Under the so-called static conditions, vapor is formed when the pressure drops below the vapor pressure. Hydrodynamic cavitation is the onset of such cavities inside a liquid flow as the local high velocities induce low pressure. The pressure threshold under which the liquid cohesion is no longer guaranteed would ideally be defined from a microscopic point of view although in practice, it is more convenient to use macroscopic fluid properties. Cavitation-induced bubbles collapse and generate jets, shockwaves and pressure oscillations when subjected to high pressures.
Interaction of a M=3 shock wave in air with a cylindrical bubble of helium (At=0.8) and the resulting Richtmeyer-Meshkov Instability using wavelets-adaptive grids and local time stepping technique on multicore architectures, effective resolution=8192x8192 (CSE Lab)
Parallel Simulations and Experiments
We investigate the evolution of vapor cavities near rigid walls and free surfaces. The collapse of such bubbles is challenging to study as the phenomenon involves many temporal and spatial scales. Multiscale and multiphysics tools will be developed by coupling multi-resolution vortex methods and smoothed particle hydrodynamics to Lagrangian level-set formulation for two-phase flows. These tools will further extended to account for complex flows and geometries such as bubble collapse near a non-planar wall or inside a jet.
Collaborators: Prof. Francois Avellan (EPFL-LMH)
- Bergdorf M., Cottet G.H., Koumoutsakos P. (2005), “Multilevel Adaptive Particle Methods for Convection-Diffusion Equations, Multiscale Modeling and Simulation”, Vol. 4, No. 1, 2005.(Abstract) (pdf)
- Cottet G.H., Koumoutsakos P., (2000), “Vortex Methods: Theory and Practice”, Cambridge Univ. Press, 2000.
- Hieber S.E, Koumoutsakos P., (2005), “A lagrangian particle level set method”, Journal of Computational Physics, 210, pp. 342-367, 2005.(Abstract) (pdf)
- Hieber S. E., Walther J. H., Koumoutsakos P., (2004), “Remeshed Smoothed Particle Hydrodynamics Simulation of the Mechanical Behavior of Human Organs”, J. of Tech. and Health Care, 2004, vol. 12, no. 4, pp. 305 – 314.(Abstract) (pdf)
- Sbalzarini I.F., Walther J.H., Bergdorf M., Hieber S.E., Kotsalis E.M., Koumoutsakos P., (2006), “PPM – A highly efficient parallel particle–mesh library for the simulation of continuum systems”, J. of Comp. Phys, 215, pp. 566-588, 2006.(Abstract) (pdf).