A turbulent plume under different experimental conditions: Entrainment, volocity and vorticity fields

• Author: María Pilar López González-Nieto, Dept. Matemática Aplicada, Facultad Ciencias Biológicas. Univ. Complutense de Madrid..


• Names of other authors: Annia Matulka, José Manuel Redondo, Ana María Tarquis.


• Oral or poster: poster.


• Downloadable abstract: click here.


• Abstract:
  Turbulent plumes are fluid motions whose primary source of kinetic energy and momentum flux is body forces derived from density inhomogeneities. The plume boundary acts as a phase boundary across which ambient fluid is entrained. The difference between the plume-fluid radial velocity and the total fluid velocity quantifies in a natural way the purely horizontal entrainment flux of ambient fluid into the plume across the phase boundary at the plume edge.
  At geophysics, it is usual the generation of turbulent plumes as a part of a dispersion process. For example, there are eruptionc plumes, river plumes (into a lake, sea or ocean), mantle plumes, hydrothermal plumes or contaminant plumes, for example. They also are important in engineering (building ventilation processes).
  Present paper describes an initial research on a turbulent plume in different experimental configurations (Atwood number and initial potential energy). This work is based on experiments in a confined geomtry that have been performed in laboratory utilizing visualizations methods.
  We aim to understand the behaviour of a turbulent plume looking at its velocity and vorticity fields, using the PIV method. We calculate velocity and vorticity PDFs and the evolution of the structure of stratified decaying, with DigFlow program (Matulka, 2010). Present paper shows results of velocity and vorticity for different Atwood number in the evolution of time. We also explore the mixing of the ambient fluid produced by plume analyzing the evolution of the plume radius b(z) under different experimental conditions. Commonly onedimensional models incorporating a constant entrainment coefficient are used; we verify experimentally this assumption and study the possibility of a variable entrainment, also related to the modification of the initial experimental conditions.
  
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