Numerical and experimental investigations of bubble dynamics between two parallel cylinders

Combining experimental and numerical methods, we investigate the dynamics of a cavitation bubble between two parallel cylinders. The results reveal that the bubble motion is highly dependent on the distance parameter γ, cylinder size ratio λ and deviation distance η [γ = d/Rmax, λ = Rc/Rmax, η = (γ1 − γ2)/2, d is the vertical distance from the bubble's initial center to the cylinder walls, Rc is the radius of cylinder, Rmax is the maximum radius of the bubble]. Experiments are conducted using a high-speed camera to capture the morphology of a transient bubble with an electric discharge method. A three-dimensional model is established based on the boundary integral method. We employ a weighted moving least squares method, a density potential method, and an edge swapping method to maintain the mesh regularity. When the bubble is located in the middle between the two cylinders, three collapse patterns are identified as splitting, counter jet, and spherical collapse, indicated by the magnitudes of three distinct velocities. A phase diagram of the symmetric bubble collapse patterns in the λ–γ range is obtained. If the bubble deviates from the middle point of the two cylinders, two collapse patterns are observed, i.e., splitting and directed jetting. Finally, larger η enhances the Kelvin impulse and drives centroid migration toward the nearer cylinder. The Kelvin impulse undergoes rapid negative growth, a plateau phase, and a second phase of rapid negative growth.