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This is the unspecified version of the paper.This version of the publication may differ from the final published version. A computational fluid dynamics cavitation model based on the Eulerian-Lagrangian approach and suitable for hole-type diesel injector nozzles is presented and discussed. Permanent repository link Modelling of cavitation in diesel injector nozzles E. G I A N N A D A K I S, M. G A V A I S E S A N D C. A R C O U M A N I SThe model accounts for a number of primary physical processes pertinent to cavitation bubbles, which are integrated into the stochastic framework of the model. Its predictive capability has been assessed through comparison of the calculated onset and development of cavitation inside diesel nozzle holes against experimental data obtained in real-size and enlarged models of single-and multi-hole nozzles. For the real-size nozzle geometry, high-speed cavitation images obtained under realistic injection pressures are compared against model predictions, whereas for the largescale nozzle, validation data include images from a charge-coupled device (CCD) camera, computed tomography (CT) measurements of the liquid volume fraction and laser Doppler velocimetry (LDV) measurements of the liquid mean and root mean square (r.m.s.) velocities at different cavitation numbers (CN) and two needle lifts, corresponding to different cavitation regimes inside the injection hole. Overall, and on the basis of this validation exercise, it can be argued that cavitation modelling has reached a stage of maturity, where it can usefully identify many of the cavitation structures present in internal nozzle flows and their dependence on nozzle design and flow conditions.

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This is the unspecified version of the paper.This version of the publication may differ from the final published version. Permanent repository link:

It is thus concluded that theimplementation of this model is an effective approach for overcoming the need of a pre-defined dynamic contact angle law, frequently adopted as an approximate boundary condition for such simulations. Clearly, this model is mostly influential during the spreading phase for the cases of low We number impacts (We<˜80) since for high impact velocities, inertia dominates significantly over capillary forces in the initial phase of spreading.

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The collapse of a cavitation bubble near a rigid boundary induces a high-speed transient jet accelerating liquid onto the boundary. The shear flow produced by this event has many applications, examples are surface cleaning, cell membrane poration, and enhanced cooling. Yet the magnitude and spatio-temporal distribution of the wall shear stress are not well understood, neither experimentally nor by simulations. Here we solve the flow in the boundary layer using an axisymmetric compressible Volume of Fluid (VOF) solver from the OpenFOAM framework and discuss the resulting wall shear stress generated for a non-dimensional distance, γ = 1.0 (γ = h/R max , where h is the distance of the initial bubble centre to the boundary, R max the maximum spherical equivalent radius of the bubble). The calculation of the wall shear stress is found reliable once the flow region with constant shear rate in the boundary layer is determined. Very high wall shear stresses of 100 kPa are found during the early spreading of the jet followed by complex flows composed of annular stagnation rings and secondary vortices. Although the simulated bubble dynamics agrees very well with experiments we obtain only qualitative agreement with experiments due to inherent experimental challenges.