V. ZHDANOV, E. HASSEL
Copyright © 2012 SciRes. AMPC
inal mean velocities, con-
oncentration (U, C) and the
s in mixing, as already has
us mixture, where the
faster formation of the quasi-homogeneous mixture in com-
parison with the other mouthpieces.
Decays of the normalized longitud
ntrations and their fluctuations along the mixer axis down-
stream the nozzle demonstrate the dynamics of the tabs influ-
ence on mixing (Figure 7(a),(b)).
Exit values of the velocity and ci i
lues of these parameters at the mixer axis (U0 and C0) at the
measured cross sections were used for the normalization of the
fluctuations downstream the flow. The first normalisation shows
the evolution of velocity and scalar fields along the mixer length
and the second one gives the dynamics of the fluctuation–to-
local velocity ratio. This parameter presents the development of
the turbulence level in the flow. The correlation of the present
measurements with the known ones  was quite well.
The tabs forced the co-flow entrainment into the jet. Th
ainment started earlier and was accompanied by the decrease
of the mean velocity and the concentration, and by the growth
of the fluctuations. Maximum of the fluctuations was moved to
the nozzle directions (at x/D=0.3 for D3). Because the mean
values of the velocity and the concentration decreased stronger
than the fluctuations ones, the local ratios u’/U0, c’/C0 at the
mixer axis increased downstream. The scalar parameters de-
cayed faster than the velocity one.
The advantage of the triangle tab
en noted in the references [1,9], can be seen within the inter-
val of 0 < x/D < 3 for the mouthpiece D2 against D1. With
smaller blockage effect the mouthpiece D2 more intensively
involved the co-flow fluid to the jet and resulted in the same
mixture quality to the distance x/D=5.
The formation of the quasi-homogeneo
locity and scalar gradients fast degenerated and the fluctua-
tions distributions across the mixer were nearly uniform, was
completed in the case of the mouthpiece D3 minimum about
10d earlier in comparison with the case when the jet was issued
from the mouthpiece D0.
Figure 7. Decay of the velocity and concentration fields inhe
l jet mixer was investigated applying si-
fluxes generated by tabs resulted in the earlier en-
y the German Research Founda-
 K. B. M. Q. Zamristics of compressible
and X. K. Wang, “Measurements in the
d Measurements in an Equilatera Trian-
os, J. W. Bitting, B. Rouge, and S. Gogineni,
J. Majamaki, I. T. Lam, O Delabroy, A.
mith, and A. R. Karagozian, “Passive
he distortion of a jet by
er, “Effect of
mimy, “Control of an
y, “The evolution of a jet with vor-
. Koh, “Experimental Investigation of
Hassel and A. Chorny, “Mixing of
tmixer confined coaxial flows”, Int. J. Heat and Mass Transfer, pp.
with different mouthpieces.
Mixing in the coaxia
multaneously methods PIV and PLIF. The development of the
velocity and concentration field was controlled by the mouth-
pieces with different tabs installing in the nozzle. The mixing
enhancement has been observed at all kinds of investigated tabs,
i.e., the tabs of relative small sizes (0.13 h/d 0.18) are quite
effective also in the developed turbulent jet. The advantage of
the triangular tabs against the rectangular ones also has been
ainment of the co-flow fluid to the jet and forced the jet to
The study has been supported b
an, “Spreading characte
jets from nozzles of various geometries”, J. Fluid Mech. vol. 383,
pp. 197-228, 1999
 S. C. M. Yu, L. P. Chua,
Near Field of a Conﬁned Coaxial Square Jet”, AIAA J. vol. 42,
pp.61-69, January 2004
 W. R. Quinn, “Near-Fiel
gular Turbulent Free jet”, AIAA J. vol. 43, pp. 2574-2585,
 D. E. Nikitopoul
“Comparisons of Initially Turbulent, Low-Velocity-Ratio Circu-
lar and Square Coaxial Jets”, AIAA J. vol. 41, , pp.230-239,
 L. L.Smith, A.
R.Karagozian, F. E Marble, and O. I.Smith, “Mixing En-
hancement in a Lobed Injector,” Phys. Fluids, vol. 9, pp.
 A. J. Majamaki, O. I. S
Mixing Control via Lobed Injectors in High-Speed Flow”,
AIAA J. vol. 41, pp 623-632, April 2003
 L. J. S. Bradbury and A. H. Khadem, “T
tabs”, J. Fluid Mech. vol. 70, pp. 801-813, 1975
 M. Samimy, K. B. M. Q. Zaman and M. F. Reed
Tabs on the Flow and Noise Field of an Axisymmetric Jet”,
AIAA J. vol. 31, pp. 609-619, April 1993
 M. Q. Zaman, M. F. Reeder and M. Sa
axisymmetric jet using vortex generators”, Phys. Fluids, vol. 6,
pp. 778-794, February 1994
 M. F. Reeder and M. Samim
tex-generating tabs: real-time visualization and quantitative
measurements”, J. Fluid Mech. vol. 311, pp. 73-118, 1996
 J. K. Foss, K.B.M.Q. Zaman, “Large- and small scale ve
motion in a shear layer perturbed by tabs”, J. Fluid Mech. vol.
382, pp. 307-329, 1999
 S. C. M. Yu and P. K
Two-Stream Mixing Flow with Multiple Tabs”, AIAA J. vol. 39,
pp. 996-1005, June 2001
 V. Zhdanov, N. Kornev, E.