Abstracts - KTH Mechanics

134
APART: An MTV technique applicable in a large range of
environments
J. Bominaar ∗ , M. Pashtrapanska ∗ ,N.Dam ∗ , W. van de Water ∗† and
J. J. ter Meulen ∗
Molecular Tagging Velocimetry provides an interesting alternative to particleseeded
techniques for measuring flow velocities. Commercial techniques used nowadays
require adding seed particles to the flow, which possibly perturb the flow, do
not follow small scale turbulence very accurately and can not reach all regions of the
flow. With the MTV technique used in our lab (APART; Air Photolysis And Recombination
Tracking 1 ) a line of NO molecules is created locally by focusing a 193 nm
ArF excimer laser. An applied flow will change the characteristics and position of this
line which can be monitored, after an adjustable delay, by imaging the fluorescence
of NO induced by a 226 nm dye laser on a CCD camera. Figure 1 shows a schematic
drawing of the setup.
We present experiments where the APART technique was applied to several environments
including high temperatures and high pressures. Statistical data on the
turbulent characteristics of a turbulent premixed methane-air flame has been gathered
and compared to LDA measurements performed in a different lab. Another study
was performed in a high pressure cell where the pressure was varied between 0 and
80 bar and the ratio of oxygen and nitrogen adjusted. The width and diffusion for the
different compositions and pressures was examined.
∗Radboud University Nijmegen, Institute for Molecules and Materials, Applied Molecular Physics,
the Netherlands.
† Eindhoven University of Technology, Applied Physics, the Netherlands
1Dam et al., Opt Lett. 26, 36 (2001).
Figure 1: Schematic drawing of the APART setup; an ArF excimer laser is focused
in a line creating nitric oxide molecules from the ambient air. The line of molecules
will displace in the flow and can be visualized by imaging the fluorescence induced by
a 226 nm dye laser on an ICCD camera. The inset on the lower left shows a typical
image created by with this technique in a turbulent flame.