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Modeling and Numerical Simulation of Material Science, 2013, 3, 1-3
Published Online January 2013 (http://www.SciRP.org/journal/mnsms)
Copyright © 2013 SciRes. MNSMS
Application of Nano Technique in Measuring
Chen Zhi, YI Shihe, Zhu Yangzhu, Zhang Qinghu, Wu Yu
College of Aerospace Science and Engineering, National University of Defense Technology, Changsha , China
Turbulence, universally exist in nature and human activities, is a kind of t hre e-di me nsio nal , irregular, unsteady flow.
Ever since 19th cent ur y when people started to investigated turbulent flow technically, they have never dropped the po-
tent and intuitionistic experimental method. Recently, with the development of aviation and aerospace indust ry， espe-
cially with the increase desire of supersonic and hypersonic flight, the mecha nis m of high speed and compressible flow
has become hot topic of fluid research, resulting in development of measurement method and technique. When encoun-
tering compressible high flow, traditional techniques, such as schilieren, shadow and interference, cannot measure fine
flow structures. Fortunately, multiple-discipline integration of nano technique, laser technique and imaging technique
provides a new design for fluid measurement。Na no-tracer planar laser scattering (NPLS) is a new flow visualization
technique, which was developed by the authors’ group in 2005, and it can visualize time correctional flow structure in a
cross-section of instantaneous 3D supersonic flow at high spatiotemporal resolution. Many studies have demonstrated
that NPLS is a powerful tool to study supersonic turbulence.
Keywords: Nano Trace; NP LS; Supersonic/Hypersonic; Flow Visualization and Measurement
For the complexity and instability of the supersonic tur-
bulence, measuring its fine structures becomes very dif-
ficult. The existing experimental methods have their own
shortages for supersonic turbulence study, such as
Schlieren, filtered Rayleigh scattering (FRS), and planar
laser induced fluorescence (PLIF), and the main reasons
are their low resolution or signal noise ratio (SNR) .
NPLS, as a newly developed flow visualization tech-
nique by the authors’ group, can visualize time correc-
tional flow structures in a cross-section of instantaneous
3D supersonic flow at high spatiotemporal resolution .
Fig. 1 NPLS Testing System
As shown in Fig 1, it was the NPLS testing system used
in this paper. A dual-cavity Nd: YAG pulsed laser was
used as its light source, which emitted two laser beams of
pulse width of 6ns according to the scheduling set by the
synchronizer. A light sheet of less than 1mm thick illu-
minated the flow field of interest. Owning to the excel-
lent the following ability, nano-particles with nominal
diameter of 18 nm could catch the complicated structures
in supersonic flow field and scattered laser light effec-
tively to generate high SNR images. The recording sys-
tem was an interline transfer double-exposure CCD
whose resolution was 2K × 2K, and the shortest interval
of double-exposure was 0.2μs. The synchronizer, whose
accuracy was 250ps, can adjust the time of laser emitting
and CCD exposure according to the signal of computer to
make sure that the two laser beams were exposed in the
frames of dual-exposure respectively. The computer’s
charges were setting parameters of the synchronizer,
storing and processing images. Fig.2 shows a typical
supersonic flow image via NPLS.
Fig. 2 Typical supersonic flow measured by NPLS
C. ZHI ET AL.
Copyright © 2013 SciRes. MNSMS
2. Performance of NPLS
2.1. Visualization of supersonic flow
(a) Mc=0.24, Δt=5μs
In the past several years, spatiotemporal characteristic of
supersonic mixing layers with convective Mach number
0.12, 0.21, 0.24, 0.32, 0.50 and 0.60 were studied by the
author s. And the results revealed Kelvin-Helmholtz inst-
able vortexes in the flow field, and its spatial features and
temporal evolution can be yielded from NPLS image s,
which are shown in Fig. 3. We also studied its spanwise
structure, and found the intr i guin g vortexes due to the
secondary instability, which are shown in Fig. 4 and Fig.
The NPLS technique has been widely used to study other
important problems of supersonic mixing layer, including
the velocity field of the transition process , the turbu-
lent struc tur e with unmatched pressure , the fractal
characteristics of the mixing interface , the multiresolu-
tion analysis of the density field .
Fig. 8 NPLS image of supersonic boundary layer in
As shown in Fig. 8 is a NPLS image of flat plate boun-
dary layer in vertical plane in Ma=3 flow, and the flow
region is 100-320mm from the leading edge of plate. Fig.
8 displays the whole transition process of the boundary
layer. Until 180mm distant from the leading edge, the
flow is still laminar. Then follows transition, and flow
becomes fully developed from X=250.
2.2. Visualization of hypersonic flow
The following ability, scattering characteristic a nd reu-
niting of nano particles are the key points under the co n-
sideration of NPLS. The distribution of nano particles
can reveal the exact flow field structures as long as its
following ability meets the flows. However, when tested
flow accelerates to hypersonic, the following ability of
nano particles would be challenged again. And using
directly nano particles of smaller scale sometimes cannot
help, due to reuniting. Shown in Fig. 3, it is a hypersonic
flow structure measured by NPLS. By now, investiga-
tions on separating and scattering nano particles have to
be kept going on, in order to improve NPLS technique
and make it more applied in hypersonic flow measure-
Fig. 3 Hypersonic flow structure measured by NPLS
Fig.1 KD-01 free-piston shock tunnel
Fig. 2 Schematic diagram of the model
3. Development and Challenge of NPLS
5. Acknowledgemen ts
Project supported by National Basic Research Program
of China (Grant Nos. 2009 CB724100), National Natural
Science Foundation of China (Grant Nos. 11172326) and
innovation fund program for standout graduate students
of NUDT (Grant Nos. B120103).
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