The interactions between turbulence and flames in premixed reacting flows are studied for a broad range of turbulence intensities by analyzing scalar (reactant mass-fraction) gradient, vorticity, and strain rate fields. The analysis is based on fully compressible, three-dimensional numerical simulations of H2-air combustion in an unconfined domain. For low turbulence intensities, a flame reconstruction method based on the scalar gradient shows that the internal flame structure is similar to that of a laminar flame, while the magnitudes of the vorticity and strain rate are suppressed by heat release and there is substantial anisotropy in the orientation of intense vortical structures. As the turbulence intensity increases, the local flame orientation becomes increasingly isotropic, and the flame preheat zone is substantially broadened. There is, however, relatively little broadening of the reaction zone, even for high intensities. At high turbulence intensities, the vorticity and strain rate are only weakly affected by the flame, and their interactions with the scalar gradient are similar to those found in nonreacting turbulence. A decomposition of the total strain rate into components due to turbulence and the flame shows that vorticity suppression depends on the relative alignment between vorticity and the flame surface normal. This effect is used to explain the anisotropy of intense vortices at low intensities. The decomposition also reveals the separate effects of turbulent and dilatational straining on the flame width.
REFERENCES
1.
T.
Poinsot
and D.
Veynante
, Theoretical and Numerical Combustion
(Edwards
, Philadelphia
, 2005
).2.
S. H.
Kim
and H.
Pitsch
, “Scalar gradient and small-scale structure in turbulent premixed combustion
,” Phys. Fluids
19
, 115104
(2007
).3.
P. A.
Libby
and F. A.
Williams
, Turbulent Reacting Flows
(Academic Press
, London
, UK, 1994
), pp. 1
–61
.4.
5.
A. Y.
Poludnenko
and E. S.
Oran
, “The interaction of high-speed turbulence with flames: Global properties and internal flame structure
,” Combust. Flame
157
, 995
(2010
).6.
A. Y.
Poludnenko
and E. S.
Oran
, “The interaction of high-speed turbulence with flames: Turbulent flame speed
,” Combust. Flame
158
, 301
(2011
).7.
P. E.
Hamlington
, A. Y.
Poludnenko
, and E. S.
Oran
, “Turbulence and scalar gradient dynamics in premixed reacting flows
,” AIAA Paper 2010-5027, 2010
.8.
W. T.
Ashurst
, A. R.
Kerstein
, R. M.
Kerr
, and C. H.
Gibson
, “Alignment of vorticity and scalar gradient with strain rate in simulated Navier-Stokes turbulence
,” Phys. Fluids
30
, 2343
(1987
).9.
P. J.
Diamessis
and K. K.
Nomura
, “Interaction of vorticity, rate-of-strain, and scalar gradient in stratified homogeneous sheared turbulence
,” Phys. Fluids
12
(5
), 1166
(2000
).10.
G.
Gulitski
, M.
Kholmyansky
, W.
Kinzelbach
, B.
Lüthi
, A.
Tsinober
, and S.
Yorish
, “Velocity and temperature derivatives in high-Reynolds-number turbulent flows in the atmospheric surface layer. Part 3. Temperature and joint statistics of temperature and velocity derivatives
,” J. Fluid Mech.
589
, 103
(2007
).11.
D. A.
Donzis
and P. K.
Yeung
, “Resolution effects and scaling in numerical simulations of passive scalar mixing in turbulence
,” Physica D
239
, 1278
(2010
).12.
K. K.
Nomura
and S. E.
Elghobashi
, “The structure of inhomogeneous turbulence in variable density nonpremixed flames
,” Theor. Comput. Fluid Dyn.
5
, 153
(1993
).13.
O. N.
Boratov
, S. E.
Elghobashi
, and R.
Zhong
, “On the alignment of strain, vorticity and scalar gradient in turbulent, buoyant, nonpremixed flames
,” Phys. Fluids
10
(9
), 2260
(1998
).14.
F. A.
Jaberi
, D.
Livescu
, and C. K.
Madnia
, “Characteristics of chemically reacting compressible homogeneous turbulence
,” Phys. Fluids
12
(5
), 1189
(2000
).15.
N.
Swaminathan
and R. W.
Grout
, “Interaction of turbulence and scalar fields in premixed flames
,” Phys. Fluids
18
, 045102
(2006
).16.
N.
Chakraborty
and N.
Swaminathan
, “Influence of the Damköhler number on turbulence-scalar interaction in premixed flames. I. Physical insight
,” Phys. Fluids
19
, 045103
(2007
).17.
R.
Sankaran
, E. R.
Hawkes
, J. H.
Chen
, T.
Lu
, and C. K.
Law
, “Structure of a spatially developing turbulent lean methane-air bunsen flame
,” Proc. Combust. Inst.
31
, 1291
(2007
).18.
G.
Hartung
, J.
Hult
, C. F.
Kaminski
, J. W.
Rogerson
, and N.
Swaminathan
, “Effect of heat release on turbulence and scalar-turbulence interaction in premixed combustion
,” Phys. Fluids
20
, 035110
(2008
).19.
N.
Chakraborty
, M.
Klein
, and N.
Swaminathan
, “Effects of Lewis number on the reactive scalar gradient alignment with local strain rate in turbulent premixed flames
,” Proc. Combust. Inst.
32
, 1409
(2009
).20.
N.
Chakraborty
and R. S.
Cant
, “Effects of Lewis number on scalar transport in turbulent premixed flames
,” Phys. Fluids
21
, 035110
(2009
).21.
N.
Chakraborty
, J. W.
Rogerson
, and N.
Swaminathan
, “The scalar gradient alignment statistics of flame kernels and its modelling implications for turbulent premixed combustion
,” Flow, Turbul. Combust.
85
, 25
(2010
).22.
C. J.
Mueller
, J. F.
Driscoll
, D. L.
Reuss
, M. C.
Drake
, and M. E.
Rosalik
, “Vorticity generation and attenuation as vortices convect through a premixed flame
,” Combust. Flame
112
, 342
(1998
).23.
M.
Tanahashi
, M.
Fujimura
, and T.
Miyauchi
, “Coherent fine-scale eddies in turbulent premixed flames
,” Proc. Combust. Inst.
28
, 529
(2000
).24.
D. S.
Louch
and K. N. C.
Bray
, “Vorticity in unsteady premixed flames: Vortex pair-premixed flame interactions under imposed body forces and various degrees of heat release and laminar flame thickness
,” Combust. Flame
125
, 1279
(2001
).25.
A. M.
Steinberg
, J. F.
Driscoll
, and S. L.
Ceccio
, “Three-dimensional temporally resolved measurements of turbulence-flame interactions using orthogonal-plane cinema-stereoscopic PIV
,” Exp. Fluids
47
, 527
(2009
).26.
A. M.
Steinberg
and J. F.
Driscoll
, “Straining and wrinkling processes during turbulence–premixed flame interaction measured using temporally resolved diagnostics
,” Combust. Flame
156
, 2285
(2009
).27.
J. M.
Stone
, T. A.
Gardiner
, P.
Teuben
, J. F.
Hawley
, and J. B.
Simon
, “Athena: A new code for astrophysical MHD
,” Astrophys. J., Suppl.
178
, 137
(2008
).28.
T. A.
Gardiner
and J. M.
Stone
, “An unsplit Godunov method for ideal MHD via constrained transport in three dimensions
,” J. Comput. Phys.
227
, 4123
(2008
).29.
P.
Colella
, “Multidimensional upwind methods for hyperbolic conservation-laws
,” J. Comput. Phys.
87
, 171
(1990
).30.
J.
Saltzman
, “An unsplit 3D upwind method for hyperbolic conservation-laws
,” J. Comput. Phys.
115
, 153
(1994
).31.
V. N.
Gamezo
, T.
Ogawa
, and E. S.
Oran
, “Flame acceleration and DDT in channels with obstacles: Effect of obstacle spacing
,” Combust. Flame
155
, 302
(2008
).32.
Since kinetic energy dissipation is provided by numerical, rather than physical, viscosity, it is more difficult to estimate the Reynolds numbers and the Kolmogorov length scales. If the physical fluid is characterized by Schmidt, Sc = ν/D, and Prandtl, Pr = ν/K, numbers of unity, then the kinematic viscosity is given in analogy with Eq. 8 as ν = ν0Tn/ρ, where ν0 = D0 = κ0 = 2.9 × 10−5 g/(s · cm · Kn). This gives outer scale Reynolds numbers, ReL = UL/ν, between 180 and 2200 in the reactants for F1–F5. The corresponding Kolmogorov length scales, ηK = ν3/4/ɛ1/4, are between 0.16δL and 0.025δL.
33.
All pdfs examined in the present study (including conditional pdfs) are normalized so that the integral of the pdf over all possible values of the argument is unity.
34.
L. K.
Su
and W. J. A.
Dahm
, “Scalar imaging velocimetry measurements of the velocity gradient tensor field in turbulent flows. II. Experimental results
,”. Phys. Fluids
8
, 1883
(1996
).35.
A.
Tsinober
, An Informal Conceptual Introduction to Turbulence
(Springer
, New York
, 2009
).36.
D. A.
Donzis
, P. K.
Yeung
, and K. R.
Sreenivasan
, “Dissipation and enstrophy in isotropic turbulence: Resolution effects and scaling in direct numerical simulations
,” Phys. Fluids
20
, 045108
(2008
).37.
P. A.
Davidson
, Turbulence: An Introduction for Scientists and Engineers (Oxford University Press, 2004).38.
P.
Chakraborty
, S.
Balachandar
, and R. J.
Adrian
, “On the relationships between local vortex identification schemes
,” J. Fluid Mech.
535
, 189
(2005
).39.
S.
Pirozzoli
, M.
Bernardini
, and F.
Grasso
, “Characterization of coherent vortical structures in a supersonic turbulent boundary layer
,” J. Fluid Mech.
613
, 205
(2008
).40.
R. J.
Adrian
, “Hairpin vortex organization in wall turbulence
,”. Phys. Fluids
19
, 041301
(2007
).41.
J. M.
Wallace
, “Twenty years of experimental and direct numerical simulation access to the velocity gradient tensor: What have we learned about turbulence?
” Phys. Fluids
21
, 021301
(2009
).42.
Z. S.
She
, E.
Jackson
, and S. A.
Orszag
, “Structure and dynamics of homogeneous turbulence: Models and simulations
,” Proc. R. Soc. London, Ser. A
434
, 101
(1991
).43.
K. K.
Nomura
and G. K.
Post
, “The structure and dynamics of vorticity and rate of strain in incompressible homogeneous turbulence
,” J. Fluid Mech.
377
, 65
(1998
).44.
P. E.
Hamlington
, J.
Schumacher
, and W. J. A.
Dahm
, “Direct assessment of vorticity alignment with local and nonlocal strain rates in turbulent flows
,” Phys. Fluids
20
, 111703
(2008
).45.
O. N.
Boratov
, S. E.
Elghobashi
, and R.
Zhong
, “On the alignment of the α-strain and vorticity in turbulent nonpremixed flames
,” Phys. Fluids
8
(8
), 2251
(1996
).46.
N.
Swaminathan
and K. N. C.
Bray
, “Effect of dilatation on scalar dissipation in turbulent premixed flames
,” Combust Flame
143
, 549
(2005
).47.
A. N.
Lipatnikov
and J.
Chomiak
, “Effects of premixed flames on turbulence and turbulence scalar transport
,” Prog. Energy Combust. Sci.
36
, 1
(2010
).48.
K.
Bray
, “The interaction between turbulence and combustion
,” Proc. Combust. Inst.
17
, 223
(1979
).49.
P.
Libby
and K.
Bray
, “Countergradient diffusion in premixed turbulent flames
,” AIAA J.
19
, 205
(1981
).50.
D.
Veynante
, A.
Trouve
, K.
Bray
, and T.
Mantel
, “Gradient and counter-gradient scalar transport in turbulent premixed flames
,” J. Fluid Mech.
332
, 263
(1997
).© 2011 American Institute of Physics.
2011
American Institute of Physics
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