Volume 8, Issue 3 (March 2011)

    A Volume of Fluid Phase Change Model on Adaptive Octree Grids

    (Received 30 August 2010; accepted 19 January 2011)

    Published Online: 2011

    CODEN: JAIOAD

      Format Pages Price  
    PDF Version 21 $25   ADD TO CART


    Abstract

    A three-dimensional phase change model using finite volume has been developed. Interface thermal conditions that are consistent with the mixture formulation within the volume tracking framework are introduced. The computational grid is dynamically adapted near the interface using an octree based structure. Up to three levels of adaption are used to provide improved accuracy in regions of steep gradients of flow variables near the liquid-vapor interface at a reduced computational cost. Interface jump conditions are imposed by specifying mass, momentum, and energy sources for the mixture variables in the interface cells. Second order accurate liquid and vapor temperature gradients at cell faces are calculated based on the location and orientation of the interface (sharp interface approach). These estimates are then used to calculate the mass source terms, which are distributed in the interface cells consistent with the mixture formulation. Such an approach maintains the interface at saturation while the mixture temperatures of the liquid and vapor in the interface cells can be superheated. A one-dimensional cavity flow problem is used to test for the proper coupling of vapor generation rate with energy and momentum flux effects. Three-dimensional bubble growth rates at 5°C uniform superheat (Ja=8.6, density ratio 140, and conductivity ratio 2.3) of refrigerant FC-87 are compared with theory in the diffusion controlled regime. The analytical solution of Mikic for bubble radius as a function of time with a non-zero initial radius is used to validate the numerical solution. The numerical solution is validated against theoretical prediction of bubble radius as a function of time for a more complete validation of the balances of mass, momentum, and energy at the liquid-vapor interface.


    Author Information:

    Akhtar, Mohammad W.
    Univ. of Houston, Houston, TX

    Kleis, Stanley J.
    Univ. of Houston, Houston, TX


    Stock #: JAI103348

    ISSN: 1546-962X

    DOI: 10.1520/JAI103348

    ASTM International is a member of CrossRef.

    Author
    Title A Volume of Fluid Phase Change Model on Adaptive Octree Grids
    Symposium , 0000-00-00
    Committee D02