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Presentation
Cavitation modelling based on Eulerian-Eulerian multiphase flow
6th OpenFOAM Workshop (2011)
  • Rachid Bannari, Ph.D
Abstract

Cavitation is a physical phenomenon encountered in the normal operation of hydraulic turbines. It can lead to loss in efficiency, vibrations and blade erosion damages. It is crucial to accurately predict cavitation development and evolution to make confident predictive results for hydraulic turbines in a cavitating regime. The cavity closure is a critical region that is characterized by its unsteady and unstable behavior. In this region, liquid and vapor are highly mixed and experienced a strong interaction between the cavity and the outer flow. Most of the published work is based on the mixture multiphase model. An important limitation of this model is the absence of the interphase forces which can strongly influence the results. The aim of this work is the use of the Eulerian-Eulerian multiphase flow (also known as non homogeneous Multi-Phase Model) to model two phases transport equation. With this approach, interphase forces models need calibration to have good agreement with experimental results. In the talk, we will present validation of the Eulerian-Eulerian solver on various test cases (Hemispheric head form [1], NACA66 MOD hydrofoil [2], Venturi [3]), with the various implementations of cavitation models (Zwart [4], Singhal [5], Sauer [6], Merkle [7] and Kunz [8]). As shown in figures 1 and 2, the solver gives more adequate results than the commercial codes used (using the same cavitation model) and the interPhaseChangeFoam solver (based on the VOF methodology). Computed shapes of cavities were found to be in good agreement with those of the reported experiments. We will also present results with a population balance model (DQMOM) [9] coupled with the Eulerian-Eulerian solver to account the evolution of the size of the bubbles. It is interesting to note that our solver has the nice property to be able to validate one assumption in the Singhal cavitation model [5] related to the fact that the relative velocity between the two phases can be replaced by the square root of the kinetic energy.

Keywords
  • Cavitation,
  • CFD,
  • Multiphase,
  • Open FOAM
Publication Date
Summer June 15, 2011
Citation Information
Rachid Bannari. "Cavitation modelling based on Eulerian-Eulerian multiphase flow" 6th OpenFOAM Workshop (2011)
Available at: http://works.bepress.com/rachid_bannari/15/