The jet characteristics of bubbles near mixed boundaries

The jet characteristics of bubbles near mixed boundaries have been the focus of research in many fields. As the associated parameters are complicated, relatively few reports have been published. In this paper, a numerical model is established by considering the influence of the free surface and a mutual vertical wall using the boundary element method. To determine the jet characteristics of collapsing bubbles in different areas, two nondimensional parameters must be investigated: the distance γ_v from the bubble to the vertical wall and the distance γ_h from the bubble to the horizontal wall. At the same time, the buoyancy parameter δ cannot be ignored. First, the jet characteristics under an infinite vertical solid wall are discussed; furthermore, the jet direction in the stage of collapsing bubble under combined boundaries without buoyancy is studied, and we find that the variation amplitude of the jet angle changes with the free surface. Considering the buoyancy, we then divide the total area into six regions with different ranges of jet angle under small buoyancy values, allowing the significant effect of buoyancy to be studied as δ increases. In addition, we study the jet velocity qualitatively under the condition of negligible buoyancy and find that a peak jet velocity may exist at mid water depths.