This paper reports on the results of the experiment PULSAR (Pulsating and R
otating Instabilities in Oscillatory Marangoni Flows), performed on the MAX
US 3 Sounding Rocket launched last November from the Swedish base in Kiruna
. Aim of the experiment was the study of the oscillatory Marangoni convecti
on in a cylindrical liquid bridge of silicone oil with kinematic viscosity
of 5cSt. The experiment was motivated by preliminary on-ground numerical si
mulations and microscale experimental studies, that have pointed out that t
he oscillatory Marangoni instability appears at the beginning in the form o
f a pulsating regime, caused by a hydro-thermal standing wave, and then it
turns to a rotating regime, caused by a traveling wave. The height of the b
ridge was equal to the disk diameter (20mm), and the imposed temperature di
fference was 15K during the first 460 s and 20K in the second part of the e
xperiment, until the end of the microgravity period.
The analysis of the temperature profiles, measured by thermocouples located
near the disks at the same radial and axial coordinate but at different az
imuthal coordinates (shifted at 90 degrees), and the surface temperature di
stribution, measured by an infrared thermocamera, show that a pulsating and
a mixed pulsating-rotating regimes have been established during the experi
ment.
Unfortunately during the flight the accelerations level caused by two centr
ifuges with some biological samples in an adjacent module were above the ex
pected values, so that disturbing g-jitter were encountered at different ti
mes during the microgravity mission. The effects are clearly visible and th
e numerical simulations had to make different assumptions to correlate the
experimental results (C) 2000 International Astronautical Federation. Publi
shed by Elsevier Science Ltd. All rights reserved.