We present new results from the simultaneous application of
Planar Laser-Induced Fluorescence (PLIF) and Particle Tracking
Velocimetry (PTV), complemented by Direct Numerical Simula-
tions (DNSs), aimed at the detailed hydrodynamic characteriza-
tion of harmonically excited liquid-film flows. The experimental
campaign spans the Reynolds number range Re = 8 − 320, and
three Kapitza numbers Ka = 85, 350 and 1800. PLIF was em-
ployed in order to generate spatiotemporally resolved film-height
data, and PTV to generate two-dimensional (2D) planar velocity-
vector maps of the flow-field underneath the wavy interface. By
combining the two optical techniques, instantaneous and highly
localised flow-rate data were retrieved, based on which the ef-
fect of local film topology on the flow-field is studied in detail.
Surprisingly, the instantaneous flow rate is found to vary linearly
with the instantaneous film-height, while both experimental and
numerical flow-rate data are closely approximated by a simple
analytical relationship with only minor deviations. This relation-
ship, which is reported here for the first time, includes the wave
speed c and mean flow-rate Q, both of which can be obtained by
simple and inexpensive methods, thus allowing for spatiotempo-
rally resolved flow-rate predictions to be made without requiring
any knowledge of flow-field information.
Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016.