Heat transfer with the growth and collapse of cavitation bubble between two parallel heated walls

Based on the axisymmetric Navier-Stokes equations and the volume of fluid (VOF) method, the dynamical characteristics of a single cavitation bubble between two parallel plates are numerically investigated together with the effect of bubble motion on heat transfer. By comparing the evolutions of the bubble profile with experimental photos, the validity and reliability of the present model has been verified. On this basis, the velocity fields of the micro-jet induced by the bubble motion are exhibited as well as the resultant heat transfer distribution on the solid wall. The intrinsic link between jet effect and heat transfer distribution is analyzed in details. Unlike the collapse of the bubble near a single wall, the bubble between two parallel walls displays the different changes of the profiles during the motion, and contains two collapse processes. The original big bubble is first split into two small sub-bubbles (the first collapse), and these sub-bubbles further collapse near the upper and lower walls respectively (the second collapse). It is found that the second collapse of the sub-bubble has greater impact on heat transfer than the first collapse. In addition, the effects of such parameters as the initial bubble radius, gas pressure inside the bubble and non-dimensional stand-off distance on the bubble behaviors and heat transfer are discussed in details, and some interesting phenomena and beneficial conclusions are obtained. (c) 2014 Elsevier Ltd. All rights reserved.