Detecting coherent patterns in a flume by using PIV and IR
Roi Gurka, Alex Liberzon, Gad Hetsroni
Abstract We investigated the ﬂow ﬁeld in a turbulent
boundary layer in a ﬂume, by using Particle Image Ve-
locimetry (PIV) and Hot-Foil Infrared Imaging (HFIRI)
techniques. Coherent patterns in the ﬂow were identiﬁed
and characterized by using instantaneous velocity and
temperature ﬁelds. The velocity ﬁelds in the streamwise–
spanwise plane were measured in parallel to the temper-
ature distribution of the ﬂume bottom. The identiﬁed
patterns are represented by means of their spatial char-
acteristics – a non-dimensional spatial separation between
streamwise patterns, k
Wall bounded turbulent ﬂows have been discussed exten-
sively in the literature, in particular the coherent structures
in this region (see for example Panton 1997). The coherent
structures account for over 80% of the energy in the tur-
bulent ﬂuctuations, during the bursting process (Kim et al.
1971), related to the transport of the ﬂuid from the low-
speed regions to the main stream, and sweeping of ﬂuid
from the outer region toward the wall (Robinson 1991).
High- and low-speed streaks are the most well recognized
coherent structures, originally discovered by Kline et al.
(1967), by using hydrogen bubble ﬂow visualization. Since
then, a variety of experimental techniques have been utilized
for investigation of low-speed streaks, including bubble or
particle tracer visualization (among others: Rashidi and
Banerjee 1990; Smith and Metzler 1983), hot-wire ane-
mometry (e.g., Nakagawa and Nezu 1981), and particle
image velocimetry (PIV) (Adrian 1991). A list of the
experimental investigation of the coherent patterns in the
near-wall region is far too long to review.
A comprehensive study of the heat transfer, in addition
to the momentum transfer in the near-wall region, relies
on the quantitative information about thermal and velocity
ﬁelds. Unfortunately, most of the available non-intrusive
measurement techniques, such as laser-Doppler veloci-
metry (LDV), planar laser induced ﬂorescence (PLIF) and
PIV, have limited accuracy at small non-dimensional dis-
tances from the wall. The direct evidence of the ﬂuid-wall
interactions can be visualized by using the heated-thin-foil
technique, which has been successfully applied to a variety
of convective heat transfer measurements (De Luca et al.
1990; Carlomagno 1997), and implemented for turbulent
boundary layer research (Hetsroni and Rozenblit 1994).
The idea is based on the assumption, that the ordered
thermal patterns show ﬂuctuations of the temperature ﬁeld
due to the exchange of the low- and high-momentum ﬂuid
between the near-wall and the outer regions of the
boundary layer, respectively.
Hetsroni et al. (2001) and Kowalewski et al. (2003) used
this assumption as a basis for the indirect measurement of
the convective velocity through IR imaging of the hot-foil
and tracking of the displacement of the thermal patterns. It
was shown by Iritani et al. (1983) and Kim (1989), that the
scalar ﬁelds in the wall region are highly correlated with
the streamwise velocity. In the present study we extended
the experimental technique (Hetsroni et al. 2001;
Kowalewski et al. 2003) toward the direct measurement of
the velocity ﬁeld in addition to the thermal patterns
measurements by using the HFIRI method. The combined
PIV and HFIRI measurement technique which allows for
the instantaneous correlated analysis of the momentum
and heat transfer in the near-wall region is presented.
In Sect. 2 we present the experimental setup, experi-
mental conditions and the optical conﬁguration of PIV
and HFIRI, followed by the description of the combined
technique in Sect. 3. The preliminary results and discus-
sions are provided in Sect. 4 and concluded by the sum-
mary in Sect. 5.
The experiments were conducted in a horizontal ﬂume of
4.9·0.32·0.1 m as shown in Fig. 1.
Experiments in Fluids 37 (2004) 230–236
Received: 10 September 2003 / Accepted: 26 February 2004
Published online: 15 April 2004
Ó Springer-Verlag 2004
R. Gurka, A. Liberzon, G. Hetsroni (&)
Multiphase Flow Laboratory, Mechanical Engineering Department,
Technion-IIT, 32000 Haifa, Israel
Present address: R. Gurka
Department of Mechanical Engineering, Johns Hopkins University,
Baltimore, MD USA
Present address: A. Liberzon
Institute of Hydromechanics and Water Resources Management,
The authors would like to thank Prof. Tomasz Kowalewski for
the help with the data acquisition and helpful discussions about
the experimental setup.