Towards an understanding of the mechanisms leading to air entrainment in the skimming fow over stepped spillways
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Fecha
2020-02
Profesor/a Guía
Facultad/escuela
Idioma
en
Título de la revista
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Título del volumen
Editor
Springer
Nombre de Curso
Licencia CC
Licencia CC
Resumen
Modern turbulence models allow for detailed numerical solutions, involving millions of
data points and numerous degrees of freedom; these solutions have the potential to provide
notable insights into the fows past hydraulic structures. In this paper, we present new analyses of a Detached-eddy simulation of the fow past stepped spillways in three dimensions,
in order to investigate the coherent structures conducive to the phenomenon of air entrainment. The analyses focus on the spatial distributions of vorticity and velocity, as well as
time series of the vorticity component in the transverse direction. A new index, Vn, is proposed in order to represent the spatial location of patches of vorticity magnitude, showing
by defnition that time-averaged values of such index (Vn) constitute the fraction of time
in which the vorticity exceeds n s−1
. When such average values are plotted for the central
plane of the spillway, they strongly agree with plots of turbulent kinetic energy, conclusively connecting the vorticity patches with the turbulence intensities. The spatial evolution
of velocity and vorticity components in a curved surface located at the experimental values
of the thickness of the boundary layer indicates an important development of turbulence,
manifested by large instantaneous values of the main fow variables. Three-dimensional
plots of iso-surfaces of constant Vn and of turbulent kinetic energy show a similar growth
rate, providing further evidence of the interconnection of variables. Finally, these results
suggest that steps “compensate” the decay of turbulence by generating vorticity patches in
between the steps, which they then become released to the fow and reach positions close to
the free surface
Notas
Indexación: Scopus
Palabras clave
Stepped spillway · Non-aerated fow · Skimming fow · Detached eddy simulation (DES) · Particle image velocimetry (PIV) · Vorticity · Turbulent kinetic energy
Citación
Environmental Fluid Mechanics Open Access Volume 20, Issue 2, Pages 375 - 3921 April 2020